mv 4 :'^hl jbb^i li : '■ 4'!'. ?S--: fri-v'T.-f ■'■fit:*- ».■■';' M . 4> -J ■ -(.■v BtH'Tri'i :L Weber's Hildebrandt's Handbuch der Anatomie des Menschen, s. 66. c Carpenter's Principles of Human Physiology, p. 56. Lond. 1842; or Amer. edit, by Dr. Clymer, Philad. 1843; and Todd and Bowman's Physiological Anatomy and Physiology of Man, p. 4. Lond. 1843. 16 NATURAL BODIES. " in the present state of the science," for several bodies, now esteemed compound, were, not many years ago, classed amongst the simple, or elementary. It is not much more than thirty years since the alkalies were found to be composed of two elements. Previously they were considered simple. In the animal and the vegetable, we find substances, also called elements, but with the epithet organic, because only found in organized bodies, and therefore the exclusive products of organization and of life. For ex- ample, in both animals and vegetables we meet with oxygen, hydrogen, carbon, azote, and different metallic substances: these are chemical or inorganic elements, and we further meet with albumen, gelatin, fibrin, osmazome, &c, substances, which con- stitute the various organs, and which, therefore, have been termed organic elements or compounds of organization ; yet they are capable of decomposition, and in one sense, therefore, not elemen- tary. In the inorganic body, all the elements, that constitute it, are formed by the agency of general chemical affinities; but, in the organized, the formation is produced by the force, that presides over the formation of the organic elements themselves — the force of life. Hence, the chemist is able to recompose many of the in- organic bodies, whilst the products of organization and of life set his art at defiance. The different parts of an inorganic body enjoy an existence in- dependent of each other; whilst those of the organized are mate- rially dependent. No part can, indeed, be injured without the mass and the separated portion being more or less affected. If we take a piece of marble, which is composed of carbonic acid and of lime, and break it into a thousand fragments, each portion will be found to consist of carbonic acid and of lime. The mass will be destroyed, but the pieces will not suffer from the disjunction. They will continue as fixed and unmodified as at first. Not so with an organized body. If we tear the branch from a tree, the stem itself participates more or less in the injury; the detached branch speedily undergoes striking changes; it withers; becomes shrivelled ; and, in the case of the succulent vegetable, undergoes decomposition ; certain of its constituents, no longer held in control by the vital agency, enter into new combinations, are given off in the form of gas, and the remainder sinks to earth. Changes, no less impressive, occur in the animal when a limb is separated from the body. The parent trunk suffers ; the system recoils at the first infliction of the injury, but subsequently arouses itself to a reparatory effort, — at times with such energy as to de- stroy its own vitality. The separated limb, like the branch, is given up, uncontrolled, to new affinities ; and putrefaction soon reduces the mass to a state in which its previously admirable or- ganization is no longer perceptible. Some of the lower classes of animals may indeed be divided with impunity, and with no other effect than that of multiplying the animal in proportion to the num.- INORGANIC AND ORGANIZED. 17 ber of sections, but these cases are exceptions; and we may re- gard the destructive process, — set up when parts of organized bodies are separated, — as one of the best modes of distinction between the inorganic and organized classes. 5. Texture. — In this respect the inorganic and organized differ considerably, — a difference which has given rise to their respective appellations. To the structure of the latter class only can the term texture be with propriety applied. If we examine a vegetable or animal substance with attention, we find, that it has a regular and determinate arrangement or structure; and we readily discover, that it consists of various parts ; — in the vegetable, of wood, bark, leaves, roots, flowers, &c.; and in the animal, of muscles, nerves, vessels, &c.; all of which appear to be instruments or organs for specific purposes in the economy of the being. Hence, the body is said to be organized, and the result, as well as the process, is often called organization. Properly, organization means the process by which an organised being is formed; organism, the result of such process, or the organic structure. The particles of matter in an organized body, in many instances, constitute fibres, which interlace and intersect each other in all directions, and form a spongy areolar texture or tissue. Of these tissues the various organs of the body are composed. These fibres, and indeed every organized structure, are considered by recent histologists to be formed originally from cellgerms or cytoblasts ; the cells formed from them assuming an arrangement appropriate to the particular tissue. In the inorganic substance the mass is homoge- neous ; the smallest particle of marble consists of carbonic acid and lime ; and all the particles concur alike in the formation and pre- servation of the body. Lastly, whilst an inorganic body, of a de- terminate species, has always a fixed composition, the living being, although constituting a particular species, may present individual differences, giving rise, in the animal, to various temperaments, constitutions, &c. 6. Mode of preservation. — Preservation of the species is, in the organized, the effect of reproduction. As regards individual pre- servation, that of the mineral is dependent upon the same actions that effected its formation, on the persistence of the affinities of co- hesion and combination, which united its various particles. The animal and the vegetable, on the other hand, are maintained by a mechanism peculiar to themselves. From the bodies surrounding them they lay hold of nutritious matter, which, by a process of elaboration, they assimilate to their own composition ; at the same time, they are constantly absorbing or taking up particles of their own structure, and throwing them off. The actions of composition and decomposition are constant whilst life exists, although subject to particular modifications at different periods of existence, and under different circumstances. Again: — the inorganic and organized are alike subject to changes 18 NATURAL BODIES. during their existence; but the character of these changes, in the two classes, differs essentially. The mineral retains its form, unl(?ss acted upon by some mechanical or chemical force. Within, all tne particles are at rest, and no internal force exists which can su[JJect them to modification. There is no succession of conditions whictj can be termed ages. How different is the case with organized bodies ! Internally, there is no rest; from birth to death all is in a state of activity. The plant and the animal are subject to inces- sant changes. Each runs through a succession of conditions or ages. We see it successively develope its structure and functions, attain maturity, and finally decay. Characteristic differences likewise exist in the external confor- mation of the beings of the two divisions, as well as in their mode of increase. Inorganic bodies have no covering to defend them, no exterior envelope to preserve their form ; — a stone, for example, is the same at its centre as at its circumference ; — whilst organized bodies are protected by an elastic and extensible covering, differing from the parts beneath, and inservient to valuable purposes in the economy. Every change, to which an inorganic body is liable, must occur at its surface. It is there that the particles are added or abstracted when it experiences increase or diminution of size. This increase — for growth it can scarcely be termed — takes place by accretion or juxtaposition, that is, by the successive application of fresh parti- cles upon those that form the primitive nucleus ; and diminution in bulk is produced by the removal of the external layers or particles; but in organised substances, increase or growth is caused by parti- cles deposited internally, and diminution by particles substracted from within. We see them, likewise, under two conditions, to which there is nothing similar in the mineral kingdom—health, and disease. In the former, the functions are executed with freedom and energy; in the latter, with oppression and restraint. 7. Termination. — Every body,inorganic or organized, may cease to exist but the mode of cessation varies greatly in the two classes. The mineral is broken down by mechanical violence, or it ceases to exist in consequence of modifications in the affinities, which held it concrete. It has no fixed duration, and its existence may be ter- minated at any moment, when the circumstances, that retained it in aggregation, are destroyed. The vegetable and the animal, on the other hand, can carry on their functions for a period only, which is fixed and determinate for each species. For a time, new particles are deposited internally. The bulk is augmented, and the external envelope distended, until maturity or full development is attained ; but, after this, decay commences ; the functions are ex- erted with gradually diminishing energy; the fluids decrease in quantity ; and the solids become more rigid, — circumstances pre- monitory of the total cessation of vitality. This term of duration is very different in different species. Whilst many of the lower classes of animals and vegetables have but an ephemeral existence ANIMALS AND VEGETABLES. 19 some of the more elevated individuals of the two kingdoms outlive a century. 8. Motive forces. — Lastly, observation has satisfactorily proved, that there are certain forces which affect matter in general, the in- organic as well as the organized, but that, in addition to these, the organized possess a peculiar force or forces, which modify them in the most remarkable manner. Hence, we have general forces, and special or vital; the first acting upon all matter, the dead and the living, and including the forces of gravitation, cohesion, chemical affinity, &c.; the latter being exclusive to living beings. Such are the chief distinctions to be drawn between the two great divisions of natural bodies, the inorganic and the organized. By the comparison which has been instituted, the objects of physio- logy, the phenomena of life, have been indicated. To inquire into the mode in which a living being is born, nourished, reproduced, and dies, is the legitimate object of this science. We have, how- ever, entered only into a comparison between the inorganic and the organized. The two divisions constituting this latter class differ also materially from each other. Into these differences we shall now inquire. 2. DIFFERENCE BETWEEN ANIMALS AND VEGETABLES. The distinctions between these divisions of organized bodies are not so rigidly fixed, or so readily appreciated, as those we have just considered. There are certain functions possessed by both, and hence called vegetative, plastic, or organic—nutrition and reproduction, for example ; but vegetables are endowed with these only. All organized bodies must have the power of assimilating foreign matters to their own substance, and of producing a living being similar to themselves; otherwise the species, having a limited duration, would perish. In addition to these common functions, animals have two others, sensation and voluntary motion, by the possession of which they are said to be animated. Hence they are termed animals, and the condition is called animality. This divi- sion of the functions into animal and organic has been adopted, with more or less modification, by the generality of physiologists. Between animals and vegetables, that are situate high in their respective classes, no error can possibly be indulged. The charac- ters are obvious at sight. No one can confound the horse with the oak, the butterfly with the potato. It is on the lower confines of the two kingdoms that we are liable to be deceived. Many of the zoophytes have alternately been considered vegetable and animal; and it is not until of modern date that the sponge has been almost uni- versally elevated to that kingdom to which it seems entitled. Nor is this to be wondered at. In its attachment to the rock, it is as immoveable as the lichen is to the slate, and almost equally defi- cient in the usual characteristics of animality. In general, how- ever,, we are able to classify any doubtful substance with accuracy, and the following are the principal points of difference. 20 NATURAL BODIES. 1. Composition. — The essential elements of organized matter are, carbon, oxygen, hydrogen, and azote, with alkaline and eartny salts, variously combined. Vegetables consist of the three first ol these elements, carbon, oxygen, and hydrogen. Azote is possessed in addition by the animal; yet there are many ammalsubstances that contain no azote. Plants have scarcely any ; and generally, when it is met with in them, it is found in some part, — scarcely ever dis- tributed through the whole. In the fungi, traces of a vegeto-ammal matter have been detected by the chemist, but they have only been traces. In consequence of this difference of composition, animal substances are easily known from vegetable by burning ; — a fact, which, as Dr. Fleminga has remarked, is interesting to the young naturalist, if uncertain to which kingdom to refer any substance met with in his researches. The smell of a burnt sponge, of coral, or other zoophytic animal, is so peculiar, that it can scarcely be mis- taken for that of a vegetable body in combustion. 2. Texture. — In this respect, important differences are observa- ble. Both animals and vegetables consist of solid and fluid parts. In the former, however, the fluids bear a large proportion: in the latter, the solids. This is the cause why decomposition occurs so much more rapidly in the animal than in the vegetable, and in the succulent than in the dry vegetable. If we analyze the structure of the vegetable, we cannot succeed in detecting more than one elementary tissue, which is vesicular, or arranged in areolae or vesicles, and appears to form every organ of the body, whilst, in the animal, we discover at least three of these anatomical elements, the cellular — analogous to that of the vegetable — the muscular, and the nervous. The vegetable again has no great splanchnic cavities containing the chief organs of the body. It has a smaller number of organs, and none that are destined for sensation or voli- tion ; in other words, no brain, no nerves, no muscular system ; and the organs of which it consists, are simple, and readily converti- ble into each other. This is not the case with the animal. But these differences in organization, striking as they may ap- pear, are not sufficient for rigid discrimination, as they are appli- cable only to the upper classes of each kingdom. In many vege- tables, the fluids appear to preponderate over the solids ; numerous animals are devoid of muscular and nervous tissues, and appa- rently of vessels, and distinct organs; whilst MM. Dutrochet,b Brachet,0 and others,*1 admit the existence of a rudimental nervous system even in vegetables. 3. Sensation and voluntary motion. — One manifest distinction exists between animals and vegetables. Whilst the latter receive a Philosophy of Zoology, i. 41. Edinburgh, 1822. b Recherches Anatomiques et Physiologiques sur la Structure Intime des Animaux, et des Vegetaux, et sur leur Motilite. Paris, 1824. = Recherches Experimentales sur les Fonctions du Systeme Nerveux Ganglionaire &c. Paris, 1830. d Sir J. E. Smith, Introduction to Botany, 7th edit., by Sir W. J. Hooker, p. 40 Lond. 1833. t ANIMALS AND VEGETABLES. 21 their nutrition from the objects situate around them — irresistibly and without volition, or the participation of mind — and whilst the function of reproduction is effected without the union of the sexes; volition and sensation are both necessary for the nutrition of the former, and for the acts requisite for the reproduction of the species. Hence, the necessity of two faculties or functions in the animal, which are wanting in the vegetable, viz., sensibility, or the faculty of consciousness and feeling ; and motility, or the power of moving the whole body or any of its parts at the will of the being. Vege- tables are possessed of spontaneous, but not of voluntary motion. Of the former we have numerous examples in the direction of the branches and upper surfaces of the leaves, although repeatedly disturbed, to the light; and in the unfolding and closing of flowers,- at stated periods of the day. This, however, is quite distinct from the sensibility and motility that characterize the animal. By sen- sibility man feels his own existence, — becomes acquainted with the universe, — appreciates the bodies that compose it, and expe- riences all the desires and inward feelings that solicit him to the performance of those external actions, which are requisite for his preservation as an individual, and as a species; and by motility he executes those external actions which his sensibility may suggest to him. By some naturalists it has been maintained, that those plants, which are borne about on the waves, and fructify in that situa- tion, exhibit to us examples of the locomotility, which is described as characteristic of the animal. One of the most interesting novel- ties, in the monotonous occurrences of a voyage across the Atlantic towards the Gulf of Florida, is the almost interminable quantity of the Fucus natans, Florida weed or Gulf weed, with which the surface of the ocean is covered. But how different is this motion from the locomotility of animals ! It is a subtlety to conceive them identical. The weed is passively and unconsciously borne whithersoever the winds and the waves may urge it, whilst loco- motion requires the direct agency of volition, of a nervous system that can excite, and of muscles that can act under such excitement. The spontaneity and perceptivity of plants, as they have been termed, must also be explained in a different manner from the ele- vated function of sensibility on which we shall have to dwell. These properties must be referred to the fact of certain vegetables being possessed of the faculty of contracting on the application of a stimulus, independently of sensation or consciousness. If we touch the leaf of the sensitive plant, Mimosa pudica, the various leaflets collapse in rapid succession. In the barberry bush, Berberis vulgaris, we have another example of the possession of this faculty. In the flower, the six stamens, spreading moderately, are sheltered under the concave tips of the petals, till some extraneous body, as the feet or trunk of an insect in search of honey, touches the inner part of each filament, near the bottom. The susceptibility of this part is such, that the filament immediately contracts, and strikes its 22 NATURAL BODIES. anther, full of pollen, against the stigma. Any other part of the filament may be touched without this result, provided no concus- sion be given to the whole. After a while, the filament retires gradually, and may be again stimulated, and when each petal, with its annexed filament, has fallen to the ground, the latter, on being touched, shows as much sensibility as ever.a These singular effects are produced by the power of contrac- tility or irritability, the nature of which will fall under considera- tion hereafter. It is possessed equally by animals and vegetables, and is essentially organic and vital. This power, we shall see, needs not the intervention of volition : it is constantly exerted in the animal without consciousness, and therefore necessarily without • volition. Its existence in vegetables does not, consequently, demonstrate that they are possessed of consciousness. 4. Nutrition.—A great difference exists between plants and animals in this respect. The plant, being fixed to the soil, cannot search after food. It must be entirely passive, and obtain its sup- plies from the materials around, and in contact with it; and the absorbing vessels of nutrition must necessarily open on its exterior. In the animal, on the other hand, the aliment is scarcely ever found in a state fit for absorption : it is crude, and in general — Ehrenbergb thinks always — requires to be received into a central organ, or stomach, for the purpose of undergoing changes, by a process termed digestion, which adapts it for the nutrition of the individual. The absorbing vessels of nutrition arise, in this case, from the internal or lining membrane of the alimentary tube. The analogy, however, that exists between these two kinds of absorp- tion is great, and had not escaped the attention of the ancients : — " Quemadmodum terra arboribus, ita animalibus ventriculus sicut humus" was an aphoristic expression of universal reception. With similar feelings, Boerhaave asserts, that animals have their roots of nutrition in their intestines ? and Dr. Alston0 has fancifully termed a plant an inverted animal. Again, in both plants and animals the residue of the matters absorbed is ejected from the body; but the form and character of the rejected portion vary in the two kingdoms. In the plant, the superfluous quantity is thrown off in gaseous, hydrogenated, or aqueous exhalations : in the animal, the useless portion is excreted, or rejected as excrement, of which azote is a constituent. After all, the most essential difference consists in the steps that are preliminary to the reception of food. These, in the animal, are voluntary, — requiring prehension, often locomotion, and always consciousness. 5. Reproduction. — In this function we find a striking analogy between animals and vegetables ; but differences exist, which must be referred to the same cause, that produced many of the a Sir J. E. Smith's Introduction to Botany, p. 325. t> Edinb. New Philosophical Journal, for Sept. 1831 ; and Jan. 1838, p. 232. e Tirocinium Botanicum Edinburgense, 8vo. Edinb. 1753. PHYSIOLOGY OF MAN. 23 distinctions already pointed out — the possession, by the animal, of sensibility and locomotility. For example, every part of the generative act is, in the vegetable, without the perception or voli- tion of the being : —the union of the sexes, fecundation, and the birth of the new individual are alike automatic. In the animal, on the other hand, the approximation of the sexes is always volun- tary and effected consciously — the birth of the new individual being not only perceived, but somewhat aided by volition. Fecun- dation alone is involuntary and irresistible. Again, in the vegetable the sexual organs do not exist at an early period, and are not developed until reproduction is practicable. They are capable of acting for once only, and perish after fecun- dation ; and if the plant be vivacious, they fall off after each repro- duction, and are annually renewed. In the animal, on the contrary, they exist from the earliest period of foetal development, survive repeated fecundations, and continue during the life of the individual. Lastly, the possession of sensibility and locomotility leads to other characteristics of animated beings. These functions are incapable of constant, unremitting exertion. Sleep, therefore, be- comes necessary. The animal is also capable of expression or of language, in a degree proportionate to the extent of his sensibility, and of his power over the beings that surround him. But these differences in function are not so discriminative as they may at first appear. There are many animals, which are as irresistibly attached to the soil as the vegetables themselves. Like the latter, they must, of necessity, be compelled to absorb their food in the state in which it is presented to them. Sensibility and locomotility appear, in the zoophyte, to be no more necessary than in the vegetable. No nervous, no muscular system is required; and, accordingly, none can be traced in them ; whilst many of those spontaneous motions of the vegetable, which have been described, have been considered by some to indicate the first rudiments of sensibility and locomotility : and Linnaeus* has regarded the closure of the flowers towards night as the sleep, and the movements of vegetables, for the approximation of the sexual organs, as the marriage of plants.b II. GENERAL PHYSIOLOGY OF MAN. The observations made on the difference between animals and vegetables have anticipated many topics, which would require con- a Amoenit. Academ.; torn. iv. b See, on the differences between Animals and Vegetables, Tiedemann, Traite Com- plet de Physiologie de l'Homme, traduit par A. J. L. Jourdan, i. 166, Paris, 1831 ; Southwood Smith's Philosophy of Health, Part I. chap. i. Lond. 1835 ; Virey, Philo- sophic de l'Histoire Naturelle, &c. p. 253, Paris, 1835; Miiller's Handbuch der Phy- siologie des Menschen, Coblenz, 1835, 1837, or Baly's translation, Part I. p. 40, Lond. 1837 i Dr. W. B. Carpenter's Principles of General and Comparative Physio- logy, Introduction, 2d edit. Lond. 1841; and his Human Physiology, Lond. 1842; and Henle, Allgemeine Anatomie, u. s. w. Leipz. 1841 ; or Jourdan's French Transla- tion, p. 3. Paris, 1843. 24 MATERIAL COMPOSITION OF MAN. sideration under this head. Those general properties, which man possesses along with other animals, have been referred to in a cur- sory manner. They will now demand a more special investigation. 1.--MATERIAL COMPOSITION OF MAN. The detailed study of human organization is the province of the anatomist, — of its intimate composition, that of the chemist. In explaining the functions executed by the various organs, the phy- siologist will frequently have occasion to trench upon both of these departments. The bones, in the aggregate, form the skeleton. The base of this skeleton is a series of vertebrae, with the skull as a capital — itself regarded as a vertebra by De Blainville. This base is situate on the median line through the whole trunk, and contains a cavity, in which are lodged the brain and spinal marrow. On each side of this, other bones are arranged in pairs, which by some have been called appendices. Upon the skeleton are placed muscles, for moving the different parts of the body, and for changing its situa- tion with regard to the soil. The body is again divided into trunk and linibs. The trunk, which is the principal portion, is composed of three splanchnic cavities, situate one above the other — the ab- domen, thorax, and head. These contain the most important organs of the body — those that effect the functions of sensibility, digestion, respiration, circulation, &c. The head comprises the face, which contains the organs of four of the senses—those of sight, hearing, smell, and taste, — and the cranium, which lodges the brain — the organ of the mental manifestations, and the most elevated part of the nervous system. The thorax or chest con- tains the lungs — organs of respiration — and the heart, the great organ of the circulation. The abdomen contains the principal organs of digestion, and (if we include in it the pelvis) those of the urinary secretion and of generation. Of the limbs, the upper, suspended on each side of the thorax, are instruments of prehension, and are terminated by the hand, the great organ of touch. The loioerare situate beneath the trunk, and are agents for supporting the body, and for locomotion. Vessels, emanating from the heart, are distri- buted to every part; conveying to them the blood necessary for their vitality and nutrition : these are the arteries. Other vessels com- municate with them, and convey the blood back to the heart — the veins; whilst a third set communicate also with the arteries, and convey into the circulation, by a particular channel, a fluid called lymph — whence they derive the name of lymphatics. Nerves, communicating with the great central masses of the nervous sys- tem, are distributed to every part to complete their vitality; and lastly, a membrane or layer, possessed of acute sensibility__the skin — serves as an outer envelope to the whole body. It has been already remarked, that the animal body consists essentially of four ultimate elements — oxygen, hydrogen, carbon and azote. This is correct as a general principle ; but organic MATERIAL COMPOSITION OF MAN. 25 chemistry has shown, that some of the constituents afford little or no traces of azote. It was likewise observed, that two kinds of elements enter into the composition of the body — the chemical or inorganic ; and the organic, which are compound, and formed only under the principle of life. The chemical or inorganic elements, met with, are — oxygen, hydrogen, carbon, azote, phosphorus, calcium ; and, in smaller quantity, sulphur, iron, manganese, calcium, silicium, aluminium, chlorine ; also, sodium, magnesium, &c, &c. 1. Oxygen. — This is widely distributed in the solids and fluids, and a constant supply of it from the atmosphere is indispensable to animal life. It is almost always found combined with other bodies, often in the form of carbonic acid — that is, united with carbon. In a separate state it is met with in the air-bag of fishes, in which it is found varying in quantity, according to the species, and the depth at which the fish has been caught. 2. Hydrogen. — This gas occurs universally in the animal kingdom. It is a constituent of all the fluids, and of many of the solids ; and is generally in a state of combination with carbon. In the human intestines it has been found pure, as well as combined with carbon and sulphur. 3. Carbon. — This substance is met with under various forms, in both fluids and solids. It is most frequently found under that of carbonic acid. Carbonic acid has been detected in an uncom- bined state in urine by Proust, and in the blood by Vogel.a It likewise exists in the intestines of animals; but it is chiefly met with in animal bodies, in combination with the alkalies or earths ; and is emitted by all animals in the act of respiration. 4. Azote. — This gas is likewise widely distributed as a com- ponent part of animal substances. Indeed, so generally does it prevail, that it often affords a distinctive mark by which they may be known from vegetables. It likewise occurs, in an uncombined state, in the swimming bladder of certain fishes. 5. Phosphorus is an essential constituent of the brain ; and is found united with oxygen —in the state of phosphoric acid—in many of the solids and fluids. This is the acid, that is combined with the earthy matter of bones, and with potassa, soda, ammonia, and magnesia, in other parts. It is supposed to give rise to the luminousness of certain animals — as of the firefly, the Pyrosoma Allanticum, &c. — but nothing precise is known on this subject. 6. Calcium. — This metal is found only in the state of oxide or lime in the animal economy; and it is generally united with the phosphoric or carbonic acid. It is the earth, of which the hard parts of animals are constituted. 7. Sulphur is not met with extensively in the animal solids or fluids ; nor is it ever found free, but always in combination with oxygen, united to soda, potassa, or lime. It seems to be an inva- riable concomitant of albumen, and is found in the intestines, in a Annals of Philosophy, vii. 56. VOL. I.--- 3 2 6 MATERIAL COMPOSITION OF MAN. the form of sulphuretted hydrogen gas ; and as an emanation from fetid ulcers. 8. Iron.__This metal has been detected in the colouring matter of the blood, in bile, and in milk. For a long time it was con- sidered to be, in the first of these fluids, in the state of phosphate or sub-phosphate. Berzelius,a however, showed; that this was not the case; that the ashes of the colouring matter always yielded oxide of iron in the proportion of l-200th of the original mass. That distinguished chemist was, however, unable to detect the condition in which the metal exists in the blood, and could not dis- cover its presence by any of the liquid tests. Subsequently, Engel- hart showed, that the fibrin and albumen of the blood, when care- fully separated from colouring particles, do not contain a trace of iron ; whilst he could procure it from the red globules by incinera- tion. He also succeeded in proving its existence in the red glo- bules by liquid tests ; and his experiments were repeated, with the same results, by Rose of Berlin.b In milk, iron seems to be in the state of phosphate. 9. Manganese has been found in the state of oxide, along with iron, in the ashes of the hair, and also in the bones. 10. Copper and lead.—It was conceived by Devergie, that copper and lead may exist naturally in the tissues; but a commis- sion of the Academie Royale de Medecine of Paris was unable to confirm the opinion in regard to the existence of copper; and the results of the investigations of Professor F. de Cattanei di Momo,c of Pa via, seem to prove the non-existence of lead also. 11. Silicium. —Silica is found in the hair, urine, and in urinary calculi. 12. Chlorine.—In combination with hydrogen, and forming chlorohydric acid, chlorine is met 'with in most of the animal fluids. It is generally united with soda. Free chlorohydric acid has also been found by Proutd in the stomach of the rabbit, hare, horse, calf, and dog; and he has discovered the same acid in the sour matter ejected from the stomachs of those labouring under indigestion. Mr. Children, and Messrs. Tiedemann and Gmelin,6 made similar observations. Professor Emmet, and the authorf found it in considerable quantity in the healthy gastric secretions of man. 13. Fluorine. — This simple substance has been found com- bined with calcium in the enamel of the teeth. 14. Sodium, — The oxide of sodium, soda, forms a part of all the » Medico-Chirurgical Transact, vol. iii. b Turner's Chemistry, fifth ed. p. 963. Lond. 1834. «Annali Universali di Medicina, Aprile, 1840; and British and Foreign Medical Review, Jan. 1841, p. 226. d Philosoph. Transact, for 1824, p. 45. • Recherches Experimentales, &c. sur la Digestion, trad, par A. G. L. Jourdan. Art. 4, p. 94, Pans, 1827. pJ-fTi"^6'!1116 head °f " DiSestion>" and the author's Elements of Hygiene, p. 222, a fliliiuclpnicij loot). ORGANIC ELEMENTS. 27 fluids. It has never been discovered in a free state, but is united, (without an acid,) to albumen. Most frequently, it is combined with the muriatic and phosphoric acids; less so, with the lactic, carbonic, and sulphuric acids. 15. Potassium. — The oxide, potassa, is found in many animal fluids, but always united with acids—the sulphuric, chlorohydric, phosphoric, &c. It is much more common in the vegetable king- dom, and hence one of its names — vegetable alkali. 16. Magnesium. — The oxide, magnesia, exists sparingly in bones, and in some other parts, but always in combination with phosphoric acid. 17. Aluminium. — Alumina is said by Morichini to exist in the enamel of the teeth. Fourcroy and Vauquelin found it in the bones; and John, in white hairs. According to Schlossberger, it exists in the flesh of fishes.a 18. Titanium. — Rees affirms, that he detected it in salts ob- tained from the supra-renal capsules. 19. Arsenic. — It cannot be considered positively established, whether arsenic exist in the human body. Raspail and Orfila affirm that it does, and that they have discovered traces of it in the bones and muscles. They are of opinion, that it is introduced into the body in phosphuretted articles of diet, which always contain small quantities. Its presence has, however, been denied by others. The Organic Elements, proximate principles or compounds of organization are the primary combination of two or more of the elementary substances, in definite proportions. Formerly, four only were admitted—gelatin, fibrin, albumen, and oil. Of late, however, organic chemistry has pointed out numerous others, which are divided into two classes—first, those that contain azote, as albumen, gelatin, fibrin, osmazome, mucus, casein, urea, uric acid, the red colouring principle of the blood, the yellow colour- ing principle of the bile, &c.; and secondly, those that do not con- tain azote, as olein, stearin, the fatty matter of the brain and nerves, the acetic, oxalic, benzoic, and lactic acids, the sugar of milk, sugar of diabetes, picromel, the colouring principle of the bile, and that of other solids and liquids. a. Organic Elements that contain Azote. 1. Protein. — Recent researches have shown, that the chief proximate principles of animal tissues, and those that have been regarded as highly nutritious among vegetables, have almost iden- tically the same composition; and are modifications of a princi- ple to which Mulder—its discoverer — gave the name Protein. If animal albumen, fibrin, or casein, be dissolved in a moderately strong solution of caustic potassa, and the solution be exposed for » Henle, Allgemeine Anatomie, s. 4. Leipz. 1841, or Jourdan's translation, i. 2. Paris, 1843. 28 MATERIAL COMPOSITION OF MAN. some time to a high temperature, these substances are decom- posed. The addition of acetic acid to the solution causes, in all three, the separation of a gelatinous translucent precipitate, which has exactly the same character and composition, from whichsoever of the solutions it has been obtained. It may be procured, too, from globulin of blood and from vegetable albumen.a The following substances may be regarded as modifications or combinations of protein. They are composed of it and of a small quantity of phosphorus, or of sulphur, or both.b a. Albumen. — This is one of the most common organic constitu- ents, and appears under two forms — liquid and concrete. In its purest state, the former is met with in the white of egg — whence its name ; in the serum of the blood, the lymph of the absorbents, the serous fluid of the great splanchnic cavities and of the cellular membrane, and in the synovial secretion. It is colourless and transparent, without smell or taste, and is coagulated by acids, alcohol, ether, metallic solutions, infusion of galls, and by a tempe- rature of 165° Fahrenheit. It is excreted by the kidneys in large quantities, in the disease, which, owing to its presence in the urine, has been called Albuminuria. Concrete, coagulated, or solid albumen, is white, tasteless, and elastic; insoluble in water, alcohol, or oil, but readily soluble in alkalies. Albumen is always combined with soda. It exists, in abun- dance — both liquid and concrete — in different parts of the animal body. Hair, nails, and horn consist of it; and it is, in some form or other, the great constituent of many tumours. b. Fibrin. — This proximate principle exists in the chyle ; enters into the composition of the blood ; forms the chief part of muscular flesh, and may be looked upon as one of the most abundant animal substances. It is obtained by beating the blood, as it issues from a vein, with a rod. The fibrin attaches itself to each twig in the form of red filaments, which may be deprived of their colour by repeated washing with cold water. Fibrin is solid, white, flexible, slightly elastic, insipid, inodorous, and heavier than water. It is neither soluble in water, alcohol, nor acids ; it dissolves in liquid potassa or soda, in the cold, without much change, but, when warm, becomes decomposed. Fibrin constitutes the buffy coat of blood; it is thrown out from the bloodvessels, as a secretion, in many cases of inflammation becoming subsequently organized, or penetrated by bloodvessels and nerves. There is no mode of distinguishing liquid fibrin from liquid albu- men, except by the spontaneous coagulation of the former Con- sequently, according to Henle,c if a liquid does not coagulate of itself, it does not contain fibrin. The blood of persons in a state ol asphyxia, of animals fatigued to death, or poisoned ; or of per- t Hen^'o^cTt^Sr18^' Greg°ry'S ™d Wehsl^s edit- P- 10°- Cambridge, 1842. xieme, op. cu. p. ai. c Op. cit. p. 38. ORGANIC ELEMENTS. 29 sons, otherwise in health, who die of hemorrhage in consequence of slight wounds, does not coagulate, and therefore is devoid of albumen. It is erroneous, he considers, to state, that in these cases the fibrin does not coagulate. The change of albumen to fibrin has been regarded as the first important step in the process of assimilation, —fibrin being endowed with much higher vital pro- perties than albumen. This has been attributed to some influence exerted upon albuminous fluids by the living surfaces over which they pass.* c. Caseum or Casein or Caseous matter. — This substance exists in greatest abundance in milk, and is the basis of cheese. It is found also in the blood, saliva, bile, pancreatic juice; in pus, tubercular matter, &c. To obtain it, milk must be left at rest, at the ordinary temperature, until it is coagulated; the cream that collects on the surface must be taken off; the clot well washed with water, drained upon a filter, and dried. The residuum is pure caseum. It is a white, insipid, inodorous substance, insoluble in water, but readily soluble in the alkalies, especially in ammonia. It pos- sesses considerable analogy with albumen. Proust ascribes the characteristic flavour of cheese to the presence of the caseate of ammonia. Until recently, it was believed that vegetable albumen and fibrin differ from animal albumen and fibrin; but Mulder has shown that this is not the case ; and casein, which agrees with the others in composition, has been found by Liebig in the vegetable. Legumin is vegetable casein. 2. Globulin. — The globulin of Berzelius consists of the enve- lopes of the blood corpuscles, and of the part of their contents that remains after the extraction of the hematosin. Lecanu regards glo- bulin as identical with albumen; and, according to Mulder, it belongs to the combinations of protein. Henleb thinks it probable, that globulin is in reality only albumen with the membranes of the blood corpuscles. Berzelius considers the crystalline lens to be composed of the same substance. 3. Pepsin. — This substance, to which Eberle gave the name, was discovered by Schwann. It seems to be a modification of protein, but has not been much examined. It is contained in the gastric juice, and its physiological properties will be described under the head of Digestion. It greatly resembles albumen; coagulates by heat and alcohol, and loses its solvent virtues. Liebig doubts the existence of pepsin as a distinct com- pound. According to him — as explained hereafter —the solvent power of the gastric juice is owing to the gradual decomposition of a matter dissolved from the lining membrane of the stomach, aided by oxygen introduced in the saliva. 4. Gelatin. — This is the chief constituent of the cellular tissue, skin, tendons, ligaments, and cartilages. The membranes and bones also contain a large quantity of it. It is obtained by boiling * Dr. Carpenter, Brit, and For. Med. Rev., Jan. 1843, p. 269. b Op. cit. p. 53. 3* 30 MATERIAL COMPOSITION OF MAN. these substances for some time in water; clarifying the conaeii- trated solution ; allowing it to cool, and drying the substance, tnus obtained, in the air. In this state it is called glue; in a more liquia form, jelly. Gelatin dissolves readily in hot water: it is soluble in acids and alkalies; insoluble in alcohol, ether, and in the nxed and volatile oils. Alcohol precipitates it from its solution in watei. It is not a compound of protein: hence it has been concluded, that it cannot yield albumen, fibrin, or casein; and, therelore, that blood cannot be formed of it. The animal system, it has been maintained, can convert one form of protein into another, but cannot from protein form compounds that do not contain it. This deduction is probably, however, too hasty. When mixed with other food, — especially compounds of protein, — gelatin, according to Liebig,a may be useful, and may serve directly to nourish the gelatinous tissues. • Gelatin, nearly in a pure state, forms the air-bag of different kinds of fishes, and is well known under the name of isinglass. It is used also extensively in the arts, under the forms of glue and size, on account of its adhesive quality. What is called portable soup is dried jelly, seasoned with various spices. 5. Chondrin. — This was first discovered by J. Muller. It is obtained by boiling the cornea, the permanent cartilages, and the bones before ossification. 6. Osmazome. — This is the matiere extractive du bouillon, extractive, and saponaceous extract of meat. — When flesh, cut into small fragments, is macerated in successive portions of cold water, the albumen, osmazome, and salts are dissolved ; and, on boiling the solution, the albumen is coagulated. From the liquid remaining, the osmazome may be procured in a separate state, by evaporating to the consistence of an extract, and treating it with cold alcohol. This substance is of a reddish-brown colour, and is distinguished from the other animal principles by solubility in water and alcohol — whether cold or at the boiling point — and by not forming a jelly when its solution is concentrated by evaporation. Osmazome exists in the muscles of animals, in the blood, and in the brain. It gives the peculiar flavour of meat to soups; and, ac- cording to Fourcroy, the brown crust of roast meat consists of it. 7. Mucus. —This term has been applied to various substances; and hence the discordant characters ascribed to it. Applying it to the fluid secreted by mucous surfaces, it varies somewhat according to the source whence it is derived. Its leading characters may be exemplified in that derived from the nostrils, which has the follow- ing properties : it is insoluble in alcohol and water, but imbibes a little of the latter, and becomes transparent; it is neither coagu- lated by heat, nor rendered horny; but is coagulated by tannin. Mucus, in a liquid state, serves as a protecting covering to differ- ent parts. Hence it differs somewhat in its characters, according to the office it has to fulfil. When inspissated, it forms, according to some, the minute scales that are detached from the surface of the * Turner's Chemistry, 7th edit. p. 1194. Lond. 1842. ORGANIC ELEMENTS. 31 body by friction, corns, and the thick layers of the soles of the feet, the nails, and horny parts; and it is contained in considerable quantity in hair, wool, feathers, scales of fishes, &c. 8. Urea. — This proximate principle exists in the urine of the mammalia when they are in a state of health. In human urine, it is believed to exist in the form of a lactate ; in the urine of her- bivorous animals, to be combined with hippuric acid. In human urine it is less abundant after a meal, and it nearly disappears in diabetes, and in affections of the liver. It is obtained by evapo- rating urine to the consistence of syrup. The syrup is then treated with four parts of alcohol, which are afterwards volatilized by heating the alcoholic extract. The mass, that remains, is dissolved in water, or rather in alcohol, and crystallized. The purest urea that has been obtained assumes the shape of acicular prisms, similar to those of the muriate of strontian. It is colourless, devoid of smell, or of action on blue vegetable colours, transparent, and somewhat hard. Its taste is cool, slightly sharp, and its specific gravity greater than that of water. Urea is supposed by Prout to be chiefly derived from the decom- position of the gelatinous tissues; but, as Dr. Carpenter has re- marked,11 there seems to be no valid reason thus to limit the mode of its production. 9. Uric or lit hie acid. — This acid is found in the urine of man, birds, serpents, tortoises, crocodiles, lizards, in the excrements of the silk-worm, and very frequently in urinary calculi. It is obtained by dissolving any urinary calculus which contains it, or the sedi- ment of human urine, in warm liquid potassa, and precipitating the uric acid by the chlorohydric. Pure uric acid is white, taste- less, and inodorous. It is insoluble in alcohol, and is dissolved very sparingly by cold or hot water, requiring about 10,000 times its weight of that fluid, at 60° of Fahrenheit, for solution. Accord- ing to Dr. Prout, this acid is not free, but is commonly combined with ammonia; the reddening of litmus paper being not altogether owing to it, but to the super-phosphate of ammonia, which is like- wise present in urine. In the herbivora, this acid is replaced by the hippuric. The xanthic acid, found by Marcet in urinary calculi, seems to have been uric acid. 10. Red colouring principle of the blood. — It has been already observed that Engelhart and Rose, German chemists, had detected iron in the red globules of the blood, and had not found it in the other principles of that fluid. It has been considered probable, therefore, that it has something to do with the colour. Engelhart's experiments have not, however, determined the manner in which it acts, nor in what state it exists in the blood. The sulphocyanic acid which is found in the saliva, forms, with the peroxide of iron, a colour exactly like that of venous blood ; and it is possible that the colouring matter may be a sulphocyanate of iron. To obtain the red colouring matter, hematin or hematosin, ■ Human Physiology, § 673, Lond. 1842. 32 MATERIAL COMPOSITION OF MAN. allow the crassamentum or clot, cut into thin pieces, to drain as much as possible on bibulous paper, triturating it with water, and then evaporating the solution, at a temperature not exceeding 122 of Fahrenheit. When thus prepared, the colouring particles are no longer of a bright red colour, and their nature is somewhat modi- fied, in consequence of which they are insoluble in water. When half dried, they form a brownish-red, granular, friable mass ; and, when completely dried, at a temperature between 167° and 190°, the mass is tough, hard, and brilliant. The mode in which the hematosin is concerned in the coloration of the blood, will be inquired into under the head of Respiration. 11. Yellow colouring principle of the bile. — This substance is present in the bile of nearly all animals. It enters into the com- position of almost all gall-stones, and is deposited in that organ under the form of magma. It is solid, pulverulent when dry, insipid, inodorous, and heavier than water. When decomposed by heat, it yields carbonate of ammonia, charcoal, &c. It is insoluble in water, in alcohol, and the oils, but is soluble in the alkalies. These are the chief non-azoted organic elements. b. Organic Elements that do not contain Azote.a 1. Olein and Stearin. — Fixed oils and fats are not pure proxi- mate principles, as was at one time supposed. They were long presumed to consist of two substances, one of which is solid at the ordinary temperature of the atmosphere, and the other fluid: the former of these was called Stearin, from *■<«*,>, suet, the latter Elain, or Olein, from *\*.m, oil. Stearin is the chief ingredient of vegetable and animal suet, of fat and butter; and is found, although in small quantity, in the fixed oils. In the suety bodies, it is the cause of their solidity. Elain and stearin may be separated from each other by exposing fixed oil to a low temperature, and press- ing it, when congealed, between folds of bibulous paper. The stearin is thus obtained in a separate form, and by pressing the bibulous paper under water, an oily matter is procured, which is elain in a state of purity. Modern chemistry has shown, how- ever, that the fat contained in the cells of the adipose tissue is composed of a base termed glycerin, with stearic and margaric acids. Stearin is regarded as a bi-stearate of glycerin : — olein or elain, as an oleate of glycerin}' ' 2. Fatty matter of the Brain and Nerves. — Vauquelinc found two varieties of fatty matter in the brain, —the one white the other red, the properties of which have not been fully investigated Both possess the property of giving rise to phosphoric acid by cal- cination, without there being any evidence of an acid, or a r>hos- 'hoHinftv! c°mPositjon- They ma^ be obtained by repeatedly boiling the cerebral substance in alcohol, filtering each time, mix- ing the various liquors, and suffering them to cool: - a lamellated substance is deposited, which is the white fatty matter. By then a Thenard, Traite de Chimie, torn. v. Paris 1S24 » Henle, Allgemein. Anat. s. 107, Leipz. 1841. ' e Annales de Chim. Ixxxi. 37. ORGANIC ELEMENTS. 33 evaporating the alcohol, which still contains the red fatty matter and osmazome, to the consistence of bouillie, and exposing this, when cold, to the action of alcohol, the osmazome is entirely dis- solved, whilst the alcohol takes up scarcely any of the red fatty matter. 3. Acetic acid. — This acid exists in a very sensible manner in the sweat, urine, and in milk — even when entirely sweet. It, Or rather lactic acid, is formed in the stomach in indigestion; was found by the author3 and his late friend, Professor Emmet, to be contained in the gastric secretions in health, and it is one of the con- stant products of the putrid fermentation of animal or vegetable substances. It is the most prevalent of the vegetable acids, and the most easily formed artificially. 4. Oxalic acid. — This acid, — which exists extensively in the vegetable kingdom, but always united with lime, potassa, soda, or oxide of iron, — is only found as an animal constituent in certain urinary calculi, combined with lime. 5. Benzoic acid. — This acid, found in many individuals of the vegetable kingdom, is likewise met with in the urine of the horse, cow, camel, rhinoceros; and sometimes in that of man, especially of children. When benzoic acid is swallowed, hippuric acid is observed in the urine ; and it was supposed by Dr. A. Ure and others, that this was owing to the conversion of uric acid into hippuric; and as the hippurates are more soluble, it was suggested, that benzoic acid might be advantageously exhibited in lithuria; and in cases of gouty depositions of lithate of soda. It has been found, however, by Liebig,b and by Professor Booth, and Mr. Boye, of Philadelphia,0 that the administration of benzoic acid exerts no influence on the amount of uric acid in the urine. 6. Lactic acid. — The acid of milk is met with in blood, gastric juice, urine, milk, marrow, and also in muscular flesh. Some- times it is in a free state, but usually united with the alkalies. However much it may be concentrated, it does not crystallize, but remains under the form of syrup or extract. When cold it is taste- less, but when heated has a sharp acid taste. According to Dr. Prout, this acid, like urea, results from the decomposition of the gelatinous parts of the system ; according to Berzelius, however, it is a general product of the spontaneous decomposition of animal matters within the body. Liebigd denies, that any lactic acid is formed in the stomach in health ; and he adds, that the property possessed by many substances, such as starch, and the varieties of sugar, by contact with animal substances in a state of decomposi- tion, of passing into lactic acid, has induced physiologists too hastily to assume the fact of the production of lactic acid during healthy t digestion. 7. Sugar of milk. —This substance, which is so called because it has a saccharine taste, and exists chiefly, if not solely, in milk, » Elements of Hygiene, p. 222. b Animal Chemistry, p. 316. c Proceedings of the American Philosophical Society at the Centennial Celebration in Philad. May, 1843. d Op. cit. p. 107. 34 MATERIAL COMPOSITION OF MAN. differs from ordinary sugar in not fermenting. It is obtained by evaporating whey, formed during the making of cheese, to the consistence of honey; allowing the mass to cool, dissolving it, clarifying, and crystallizing. It commonly crystallises in regular parallelopipedons, terminated by pyramids with four faces. It is white, semitransparent, hard, and of a slightly saccharine taste. 8. Sugar of diabetes. — In the disease, called diabetes mellitus, the urine, which is passed in enormous quantity, contains, at the expense of the economy, a large amount of peculiar saccharine matter, which, when properly purified, appears identical, both in properties and composition, with vegetable sugar, approaching nearer to the sugar of grapes than to that of the cane. It is ob- tained in an irregularly crystalline mass, by evaporating diabetic urine to the consistence of syrup, and keeping it in a warm place for several days. It is purified by washing in cold, or, at the most, gently heated alcohol, till the liquor comes off colourless, and then dissolving it in hot alcohol. By repeated crystallization it is thus rendered pure.a In the notes of two cases of diabetes mellitus now before the author, it appears, that sixteen ounces of the urine of one of the patients, of the specific gravity of 1*034, afforded a straw- coloured extract, which, when cold and consolidated, weighed one ounce and five drachms. The same quantity of the urine of the other patient, specific gravity 1-040, yielded one ounce and seven drachms. Neither extract appeared to contain urea when nitric acid was added, but when a portion was dissolved in water, and subjected to a temperature of 212°, traces of ammonia were mani- fested on the vapour being presented to the fumes of muriatic acid. From this a conclusion was drawn that urea was present, as it is the only known animal matter which is decomposed by the heat of boiling water. During a little more than one month, the subject of the latter case passed about four hundred and eighty pints of urine, or about seventy-five pounds troy of diabetic sugar! 9. Bilin or Picromel.— Thenardb discovered this principle in the bile of the ox, sheep, dog, cat, and of several birds ; Chevallier, in that of man. To obtain it, the acetate of lead of commerce must be added to bile until there is no longer any precipitate. By this means, the yellow matter of the bile and the whole of the fatty matter are thrown down, united with the oxide of lead; the phos- phoric acid of the phosphate of soda, and the sulphuric acid of the sulphate of soda, are likewise precipitated. The picromel may then be thrown down from the filtered liquor by the subacetate of lead. The precipitate, which is a combination of picromel with oxide of lead, must now be washed and dissolved in acetic acid. t Through this solution, sulphuretted hydrogen is passed to separate the lead ; the solution is then filtered, and the acetic acid driven off by evaporation. Pure picromel is devoid of colour, and has the same appearance and consistence as thick turpentine. Its taste is at first acrid and a Prout, Medico-Chirurg. Transact, viii. 538. b Memoir. d'Arcueil, i. 23, and Traite de Chimie, torn. iii. ORGANIC ELEMENTS. 35 bitter, but afterwards sweet. Its smell is nauseous, and its specific gravity greater than that of water. When digested with the resin of the bile, a portion of the latter is dissolved, and a solution is obtained, which has both a bitter and a sweet taste, and yields a precipitate with the subacetate of lead and the stronger acids. This is the compound that causes the peculiar taste of the bile. 10. Cholesterin. — This is a constituent principle of the blood, the bile, and the medullary neurine. It is often precipitated from bile in a crystalline state ; and forms of itself concretions, which have an evidently laminated texture. It has been very frequently met with in morbid secretions and tissues, in the fluid of dropsies, in that of cysts and hydatids, and in medullary fungous and other tumours. At times, it is dissolved ; at others, swims upon the fluid under the form of brilliant plates, or forms solid masses. It is obtained from biliary calculi by boiling them in water, and dissolving them afterwards in boiling alcohol. On cooling, crystals of cholesterin separate. 11. Colouring principle of the bile — Biliverdin. — Of the na- ture of this-principle, which exists in the bile of different animals, we have no definite ideas. It is generally precipitated along with the fatty matter ; and, by means of ether, which dissolves it, may be obtained pure. The colouring principles of other parts of animals are not suffi- ciently known to admit of classification. These inorganic andorganic elements, with others of less moment, that have been discovered by modern chemists, variously com- bined and modified by the vital principle, constitute the different parts of the animal fabric. Chemistry, in its present improved con- dition, enables us to separate them, and to investigate their proper ties; but all the information we derive from this source relates to bodies, which have been influenced by the vital principle, but are no longer so ; and in the constant mutations that are occurring in the system whilst life exists, and under its controlling agency, the same textures might exhibit very different chemical characteristics, could our researches be directed to them under those circumstances. Whenever, therefore, the physiologist has to apply chemical eluci- dations to operations of the living machine, he must recollect, that all his analogies are drawn from dead matter — a state so widely differing from the living as to suggest to him the necessity of a wise and discriminating caution. The components of the animal body are invariably found under two forms — solids and fluids. Both of these are met with in every animal, the former being derived from the latter; for, from the blood every part of the body is separated; yet they are mutually dependent, for every liquid is contained in a solid. The blood itself circulates in a solid vessel: both, too, possess an analo- gous composition, are in constant motion, and are incessantly converted from one into the other. Every animal consists of a 36 MATERIAL COMPOSITION OF MAN. union of the two, and this union is indispensable to life. Yet cer- tain vague notions, with regard to their relative preponderance in the economy, and to their agency in the production of disease, have lead to very discordant doctrines of pathology, — the solidists believing, that the cause of most affections is resident in the solids ; the humorists, that we are to look for it in the fluids. In this, as in similar cases, the mean will lead to the most rational result. The causes of disease ought not to be sought in the one or the other exclusively. c. Of the Solid Parts of the Human Body. A solid is a body, whose particles adhere to each other, so that they will not separate by their own weight, but require the agency of some extraneous force to effect the disjunction. Anatomists re- duce all the solids of the human body to twelve varieties : bone, cartilage, muscle, ligament, vessel, nerve, ganglion,follicle, gland, membrane, cellular membrane, and viscus. 1. Bone is the hardest of the solids. It forms the skeleton — the levers for the various muscles to act upon, and serves-for the pro- tection of important organs. 2. Cartilage is of a white colour, formed of very elastic tissue, covering the articular extremities of bone to facilitate their move- ments ; sometimes added to bones to prolong them, as in the case of the ribs; at others, placed within the articulations, to act as elastic cushions ; and, in the foetus, forming a substitute for bone; hence, cartilages are divided into articular or incrusting, carti- lages of prolongation, interarticular cartilages, and cartilages of ossification. 3. The muscles constitute the flesh of animals. They consist of fasciculi of red and contractile fibres, extending from one bone to another, and are the agents of all movements. 4. The ligaments are very tough, difficult to tear, and under the form of cords or membranes serve to connect different parts with each other, particularly the bones and muscles ; hence their divi- sion, by some anatomists, into ligaments of the bones — as the liga- ments of the joints ; and into ligaments of muscles — as the tendons and aponeuroses. 5. The vessels are solids, having the form of canals, in which the fluids circulate. They are called — according to the fluid they convey—sanguineous (arterial and venous), chyliferous, lym- phatic, &c. 6. The nerves are solid cords, consisting of numerous fasciculi. These are connected with the brain, spinal marrow, or great sym- pathetic ; and they are the organs by which impressions are con- veyed to the nervous centres, and by which each part is endowed with vitality. There are two great divisions of the nerves, — the encephalo-spinal and the organic. 7. A ganglion is a solid knot, situate in the course of a nerve and seeming to be formed by an inextricable interlacing of the ner- SOLID PARTS. 37 vous filaments. The term is likewise applied, by many modern anatomists, to a similar interlacing of the ramifications of a lym- phatic vessel. Ganglions may, consequently, either be nervous or vascular ; and the latter, again, may be divided into chyliferous, or lymphatic, according to the kind of vessel in which they appear. Chaussier, a distinguished anatomist and physiologist, has given the name glandiform ganglions to certain organs, whose nature and functions are unknown to us, but which he considers to be organs for the admixture and elaboration of fluids, — as the thymus gland, the thyroid gland, &c. 8. Follicles or crypts are secretory organs, shaped like membra- nous ampullae or vesicles, always seated in the substance of one of the outer membranes of the body —the skin or the mucous surfaces — and secreting a fluid intended to lubricate them. They are often divided into the simple or isolated, the conglomerate, and the com- pound, according to their size, or the number in which they are grouped and united together. 9. A gland is also a secretory organ, but differing from the last. The fluid secreted by it, is of greater or less importance. Its organization is more complex than that of the follicle; and the fluid, after secretion, is poured out by means of one or more excre- tory ducts. 10. Membrane.— This is one of the most extensive and im- portant of the substances formed by the cellular tissue. It is spread out in the shape of a web, and, in man, serves to line the cavi- ties and reservoirs, and to form, support,and envelope all the organs. Bichat divides membranes into two kinds, the simple and the compound, according as they are formed of one or more layers. The simple membranes are of three kinds, the serous, mucous, and fibrous. 1st. The serous membranes are those that constitute all the sacs or shut cavities of the body, — those of the chest and abdomen, for example. 2dly. The mucous, or those that line all the outlets of the body,— the air passages, alimentary canal, urinary and genital organs, &c. 3dly. Fibrous membranes, or those which form tendon, aponeu- rosis, ligament, &c. The compound membranes are formed by the union of the sim- ple, and are divided into fibro-serous, as the pericardium; sero- mucous, as the gall-bladder, at its lower part; and fibro-mucous, as the ureter. 11. The cellular or laminated tissue — to be described pre- sently— is a sort of spongy or areolar structure, which forms the framework of all the solids, fills up the spaces between them, and serves, at the same time, as a bond of union and of separation. 12. The viscus is the most complex solid of the body, not only as regards intimate organization but use. This name is given to organs contained in the splanchnic cavities,— brain, thorax, and abdomen, — and hence called cerebral, thoracic, or abdominal. vol i. — 4 38 MATERIAL COMPOSITION OF MAN. Every animal solid is either amorphous or fibrous ; that is, it is either without apparent arrangement, like jelly, or is disposed in minute threads, which are called fibres. The disposition of these threads, in different structures, is various. Sometimes, they retain the form of threads; at others, they have that of laminae, lamella, or plates. Accordingly, when we examine any animal solid, where the organization is perceptible, it is found to be either amorphous, or fibrous and laminated. This circumstance led the ancients to endeavour to discover an elementary fibre ox filament, from which all the various organs might be formed. Hallera embraced the idea, and endeavoured to unravel every texture to this ultimate element, — asserting that it is to the physiologist what the line is to the geometer; and that, as all figures can be constructed from the line, so every tissue and organ of the body may be built up from the filament. Haller, however, admits that this elementary fibre is not capable of demon- stration, and that it is visible only to the " mind's eye," — " invisi- bilis est ea fibra, sold mentis acie distinguimus." It must be regarded, indeed, as a pure abstraction; for, as different animal substances have different proportions of carbon, hydrogen, oxygen, and azote, it is fair to conclude that the elementary fibre must differ also in the different structures. The ancients believed, that the first product of the elementary fibre was cellular tissue, and that this tissue formed every organ of the body; — the difference in the appearance of these organs arising from the different degrees of condensation of its lamina?. Anatomists, however, havebeen unable to reduce all the animal solids to cellular tissue solely. In the upper classes of animals, three primary fibres or tissues or anatomical elements are usually admitted, — the cellular or laminated, the muscular, and the nervous,pulpy, or medullary. l.'Yhecellular areolar,filamentous or laminatedfibreor tissue.— This is the most simple and abundant of the animal solids. It exists in every organized being, and is an element of every solid. In the enamel of the teeth only it has not been detected. It is formed of an assemblage of thin laminae, of delicate whitish, ex- tensible filaments, interlacing and leaving between each other areolae or cells. These plates or filaments — although possessed like every living tissue of contractility or the power of feeling an appropriate irritant and of moving responsive to such irritant —do not move perceptibly under the influence of mechanical or chemi- cal stimuli. They are composed of concrete gelatin. The great bulk of animal solids consists of cellular tissue, arranged in the form of membrane. 2. Muscular fibre or tissue. — This is a substance of a peculiar nature, arranged in fibres of extreme delicacy. The fibres are linear, soft, grayish or reddish, and manifestly possessed of con- tractility or irritability; that is, they move very perceptibly under * Elementa Physiologiae, vol. i. lib. i. sect. i. PRIMARY AND COMPOUND TISSUES. 39 the influence of mechanical or chemical stimuli. They are com- posed, essentially, of fibrin, and their histology will be described hereafter. The muscular fibres, which are arranged in the form of mem- branous expansions or muscular coats, differ from proper muscles chiefly in the mechanical arrangement of their fibres. But the physical and chemical characters of both are identical. The fibres, instead of being collected into fasciculi, are in layers, and, instead of being parallel, interlace. This tissue does not exist in the zoophyte. 3. Nervous, pulpy, or medullary fibre or tissue. — This tissue, which will be referred to hereafter, is much less distributed than the ' preceding. It is of a pulpy consistence, is composed essentially of albumen united to a fatty matter, and is the organ of sensibility, or for receiving and transmitting impressions to the mind. Of it, the brain, cerebellum, medulla spinalis, nerves and their ganglia are composed. Professor Chaussiera has added another primary fibre or tissue,— the albugineous. It is white, satiny, very resisting, of a gelatinous nature, and constitutes the tendons and tendinous structures. Chaus- sier is, perhaps, the only anatomist that admits this tissue. Others properly regard it as a very condensed variety of the cellular. These various fibres or tissues, by uniting differently, constitute the first order of solids ; and these, again, by union, gives rise to compound solids, from which the different organs, bones, glands, &c, are formed. A bone, for example, is a compound of various tissues, osseous in its body, medullary in its interior, fibrous ex- ternally, and cartilaginous at its extremities. Bichatb was the first anatomist who possessed any clear views regarding the constituent tissue's of the animal frame; and whatever merit may accrue to after anatomists and physiologists, he is en- titled to the credit of having pointed out the path, and facilitated the labours of the anatomical analyst.0 In combining to form the different structures, the solids are ar- ranged in a variety of ways. Of these, the chief are in filaments or elementary fibres, tissues, organs, apparatuses, and systems. The filament, we have seen, is the elementary solid. A fibre consists of a number of filaments united together. Occasionally, this is called a tissue: — the term tissue usually, however, means a particu- lar arrangement of fibres. An organ is a compound of several tissues. An apparatus is an assemblage of organs, concurring to the same end: — the digestive apparatus consists of the organs of mastication, insalivation,and deglutition, of the stomach, duodenum, pancreas, liver, &c. These organs may be, and are, of very dis- similar character, both as regards their structure and functions; a Table Synoptique des Solides Organiques. b Anatomie Ge"n., Paris, 1801, torn. i. c For various arrangements of the tissues, see Lepelletier, Physiologie Medicale; torn. i. Paris, 1831-1832 ; Meckel's Handbuch der Anatomie, u. s. w. Doane's trans- lation, vol. i., Philadelphia, 1822; or Grainger's Elements of General Anatomy, Lond. 1829. 40 MATERIAL COMPOSITION OF MAN. but, if they concur in the same object, they form an apparatus. A system, on the other hand, is an assemblage of organs, all ot wnicn possess the same or an analogous structure. Thus, all the muscles of the body have a common structure and function, and they con- stitute, in the aggregate, the muscular system. All the vessels ot the body, and all the nerves, for like reasons, constitute respectively the vascular, and nervous systems. d. Of the Fluids of the Human Body. The positive quantity or proportion of the fluids in the human body does not admit of easy appreciation, as it must obviously vary at different periods and under different circumstances. The younger the animal, the greater is the preponderance. When we first see the, embryo, it appears to be almost fluid. As it becomes gradually developed, the solid parts increase in their relative proportion, until the adult age ; after which the proportion becomes less and less as the individual advances in life. During the whole of existence, too, the quantity of fluids in the body fluctuates. At times, there is plethora or unusual fulness of vessels ; at others, the blood is less in quantity. Experiments have been made for the purpose of ascer- taining the relative proportion of the fluids to the solids. Richerand says, that they are in the ratio of six to one; Chaussier, of nine to one. The latter professor put a dead body, weighing one hundred and twenty pounds, into a heated oven, and dried it. After desic- cation, it was found to be reduced to twelve pounds. It is proba- ble, however, that some of the more solid portions were driven off by the heat employed, and hence, that the evaluation of the pro- portion of the fluids was too high. In the Egyptian mummies, which are completely deprived of fluid, the solids are extremely light, not weighing more than seven pounds; but as we are igno- rant of the original weight of the body, we cannot arrive at any approximation. The dead bodies found in the arid sands of Arabia, as well as the dried preparations of the anatomical theatre, afford additional instances of this reduction by desiccation. To a less ex- tent, we have the same thing exhibited in the excessive diminution in weight which occurs in disease, and occasionally in those who are apparently in health. Not many years ago, an Anatomie vivante was exhibited, in London, to the gaze of the curious and scientific, whose weight was not more than eighty pounds. Yet the ordinary functions were carried on, apparently unmodified. In the year 1830, a still more wonderful phenomena was exhibited in New York, who was called the " living skeleton." This extraor- dinary being was forty-two years old, five feet two inches high, and weighed but sixty pounds. His weight had formerly been one hundred and thirty-five pounds. For sixteen years previously, he had been gradually losing flesh, without any apparent disease, having enjoyed perfect health and appetite, and eating, drinking, and sleeping as well as any one. We have it also on the autho- rity of Captain Riley,3 that after protracted sufferings in Africa, 1 Narrative of the loss of the American Brig Commerce, &c, p. 302. New York 1817. FLUIDS. 41 he was reduced from two hundred and forty pounds to below ninety. [?] The fluids are variously contained; sometimes in vessels — as the blood and lymph; at others, in cavities — as the fluids secreted by the pleura, peritoneum, arachnoid coat of the brain, &c.; others are in minute areolae — as the fluid of the cellular membrane; whilst others again are intimately combined with the solids. They differ likewise in density, some existing in the state of halitus or vapour ; others being very thin and aqueous — as the fluid of the serous membranes ; others of more consistence — as the secretion of the mucous membranes, the animal oils, &c. The physical and chemical properties of the fluids will engage our attention when they fall individually under consideration, and we shall find that one of them at least — the blood — exhibits certain phenomena analogous to those of the living solid. The fluids have been differently classed, according to the parti- cular views that have from time to time prevailed in the schools. The ancients referred them all to four — blood, bile, phlegm or pituita, and atrabilis; and each of these was conceived to abound in one of the four ages, seasons, climates, or temperaments. The blood predominated in youth, in the spring, in cold mountainous regions, and in the sanguine or inflammatory temperament. The pituita or phlegm had the mastery in old age, in winter, in low and moist countries, and in the lymphatic temperament. The bile predominated in mature age, in summer, in hot climates, and in the bilious temperament; and lastly, the atrabilis was the character- istic of middle age, of autumn, of equatorial climes, and of the melancholic temperament. This was their grand humoral system, which has vanished before a better observation of facts, and more improved methods of physical and metaphysical investigation. The atrabilis was a creature of the imagination; the pituitous condition is unintelligible to us; and the doctrine of the influence of the humours on the ages, temperaments, &c, is irrational. Subsequently, the humours were classed according to their phy- sical and chemical properties ; for instance, they were divided into liquids, vapours, and gases; into acid, alkaline, and neutral; into thick and thin ; into aqueous, mucilaginous, gelatinous, and oily; into saline, oily, saponaceous, mucous, albuminous, and fibrinous, &c. In more modern times, endeavours have been made to arrange them according to their uses in the economy into—l,recrementitial fluids, or those intended to be again absorbed; 2, excrementitial, or those that have to be expelled from the body; and 3, those which participate in both uses, and are hence termed excremento- recrementitial. Blumenbacha divided them into crude humours, blood, and secreted humours, a division which has been partly adopted by Adelon ;b and lastly, by Professor Chaussier, whose anatomical arrangements and nomenclature have rendered him a Elements of Physiology, by Elliotson, 4th edit. Lond. 1828. b Physiologie de l'Homme, 2de edit. i. 124, Paris, 1829. 4# 42 MATERIAL COMPOSITION OF MAN. justly celebrated, reckons five classes:— 1, those produced by the act of digestion, —the chyme, and the chyle; 2, the circulating fluids, — the lymph and the blood ; 3, the perspired fluids ; 4, the follicular; and 5, the glandular. This arrangement has been adopted by Magendie,a and is perhaps as satisfactory as any that has been proposed. All these will have to engage attention under Secretion. e. Physical Properties of the Tissues. The tissues of the body possess the physical properties of matter in general. They are found to vary in consistence, — some being hard, and others soft, as well as in colonr, transparency, &c. They have, also, certain physical properties, analogous, indeed, to what are met with in several inorganic substances, but generally supe- rior in degree. These are flexibility, extensibility, and elasticity, which are variously combined and modified in the different forms of animal matter, but exist to a greater or less extent in every organ. Elasticity is only exerted under particular circumstances : when the part, for example, in which it is seated, is put upon the stretch or is compressed, the force of elasticity restores it to its primitive state, as soon as the distending or compressing cause is removed. The tissues, in which elasticity is inherent, are so dis- posed through the body, as to be kept in a state of distension by the mechanical circumstances of situation ; but, as soon as these circumstances are deranged, elasticity comes into play, and pro- duces shrinking of the.substance. It is easy to see, that these cir- cumstances, owing to the constant alteration in the relative situa- tion of parts, must be ever varying. Elasticity is, therefore, con- stantly called into action, and in many cases acts upon the tissues as a new power. The cartilages of the ribs, joints, &c, are in this manner valuable agents in particular functions. We have other examples of the mode in which elasticity exhibits itself, under similar circumstances, when the contents of hollow parts are with- drawn, and whenever muscles are divided transversely. The gaping wound, produced by a cut across a shoulder of mutton, is familiar to all. Previous to the division, the force of elasticity is kept neutralized by the mechanical circumstances of situation,— or by the continuity of the parts; but as soon as this continuity is disturbed, or, in other words, as soon as the mechanical circum- stances are altered, the force of elasticity is exerted and produces recession of the edges. This property has been described under various names. It has been called tone or tonicity, contractilite de tissu, contractility par defiant d'extension, &c. The other properties— flexibility and extensibility — vary greatly according to the structure of the parts. The tendons, which are composed of the cellular tissue, exhibit very little ex- tensibility, and this for wise purposes. They are the conductors of the force developed by the muscle, and were they to yield it would be at the expense of the muscular effort; but they possess a Precis Elementaire de Physiol. 2de edit. i. 20, Paris, 1825. PHYSICAL PROPERTIES OF TISSUES. 43 great flexibility. The articular ligaments are ve*y flexible, and somewhat more extensible. On the other hand, the fibrous or ligamentous structures, which are employed to support weights, or which are antagonists to muscular action,— such as the ligamen- tum nuchse or the strong ligament, which passes from the spine to the head of the quadruped, — are very extensible and elastic. Another physical property, possessed by animal substances, is a kind of contractility, accompanied with sudden corrugation and curling. This effect, which Bichat terms racornissement, is pro- duced by heat, and by chemical agents, especially by the strong mineral acids. The property is exhibited by leather when thrown into the fire. An effect, in some measure resembling this, is caused by the evaporation of the water which is united to animal substances. This constitutes what has been called the hygrometric property of animal membranes.11 It is characteristic of dry, membranous structures, all of which are found to contract, more or less, by the evaporation of moisture, and to expand again by its re-absorption ; hence the employment of such substances as hygrometers. Ac- cording to Chevreul,b many of the tissues are indebted for their phy- sical properties to the water they contain, or with which they are imbibed. When deprived of this fluid, they become unfit for the purposes for which they are destined in life, and resume them as soon as they have recovered it. A most important property possessed by the tissues of organized bodies, is imbibition; a property to which attention has been chiefly directed of late years. If a liquid be put in contact with any organ or tissue, in process of time the liquid will be found to have passed into the areolae of the organ or tissue, as it would enter the cells of a sponge. The length of time occupied in this imbibition, will depend upon the nature of the liquid and the kind of tissue. Some parts of the body, as the serous membranes and small vessels, act as true sponges, absorbing with great prompti- tude : others resist imbibition for a considerable time, — as the epidermis. Liquids penetrate equally from within to without: the process is then called transudation, but it does not differ from imbibition. Some singular facts have been observed regarding the imbibi- tion of fluids and gases. On filling membranous expansions, as the intestine of a chicken, with milk or some dense fluid, and im- mersing it in water, Dutrochetc observed, that the milk left the intestine, while the water entered it; and hence he concluded, that whenever an organized cavity, containing a fluid, is immersed in another fluid, less dense than that which is in the cavity, there is a Roget, art. Physiology, in Supplement to Encyclopaedia Britannica; and Outlines of Physiology, with an appendix on Phrenology. First American edition, with notes by the author of this work, p. 73, Philad. 1839. b Magendie, Precis Elementaire de Physiologie, 2de e"dit. 1825, i. 13. c Mem. pour servir a l'Histoire Anatom. et Physiol, des Animaux et des Veg&taux, Paris, 1837 ; and art. Endosmosis, in Cyclopaedia of Anatomy and Physiology, part x. p. 98, June, 1837. 44 MATERIAL COMPOSITION OF MAN. a tendency in *he cavity to expel the denser and absorb the rarer fluid This Dutrochet termed endosmose, or " inward impulsion , and he conceives it to be a new power, -a «Phy«c^r6fni° " vital action." Subsequent experiments showed, that a reverse operation could likewise take place. If the interna fluid was rarer than the external, the transmission occurred in the opposite direction. To this reverse process, Dutrochet gave the name ex- osmose, or " outward impulsion." . Soon after the appearance of Dutrochet's essay, similar experi- ments were repeated, with some modifications, by Dr. Faust,a and by Dr. Togno,b of Philadelphia, and with like results. The fact of this imbibition and transudation was singular and impressive; and with so enthusiastic an individual as Dutrochet, could not fail to give birth to numerous and novel conceptions. The energy of the action of both endosmose and exosmose is in proportion, he asserted, to the difference between the specific gravities of the two fluids; and also, independently of their gravity, their chemical nature affects their power of transmission. These effects — Du- trochet at once decided — must be owing to electricity. The cavities, in which the changes take place, he conceived to be like Leyden jars having their two surfaces charged with opposite elec- tricities, the ultimate effect or direction of the current being de- termined by the excess of the one over the other. In an interesting and valuable communication by Prof. J. K. Mit- chell,0 of Philadelphia, "on the penetrativeness of fluids," many of the visionary speculations of Dutrochet are sensibly animad- verted upon. It is there shown, that Dutrochet had asserted, in the teeth of some of his most striking facts, that the current was from a less dense to a more dense fluid; and that it was from positive to negative, dependent not on an inherent power of filtra- tion, a power always the same when the same membrane is con- cerned, but modified at pleasure by supposed electrical agencies. This view was subsequently abandoned by Dutrochet, in favour of the following principle. It is well known that porous bodies, as sugar, wood, or sponge, are capable of imbibing liquids, with which they are brought in contact. In such case the liquid is not merely introduced into the pores of the solid, as it would be into an empty space, but it is forcibly absorbed, so that it will rise to a height considerably above its former level. This force is mole- cular, and is the same that we witness in the phenomena presented by the capillary tube, which affords us the simplest case of the insinuation of a liquid into a porous body. This force alone can- not, however, cause the liquid to pass entirely through the body. If a capillary tube, capable of raising water to the height of six inches, be depressed, so that one inch only be above the surface, the water will rise to the top of the tube', but no part of it will escape. Even if the tube be inserted horizontally intd the side of the * Amer. Journal of the Med. Sciences, vii. 23, Philad. 1830. b Ibid. iv. 73, Philad. 1829. « Ibid. vii. 23, Phil. 1830. PHYSICAL PROPERTIES OF TISSUES. 45 vessel containing water, the water will only pass to the end of the tube. The same thing occurs when a liquid is placed in contact with one side of a porous membrane : it enters the pores, passes to the opposite side, and is there arrested. But if this membrane communicates with a second vessel containing a different liquid — as a saline solution, capable of mixing with the first, and affected to a different degree by the capillary attraction — then a new phe- nomenon will be presented. It will be found that both liquids enter the pores, and pass through to the opposite side. They will not, however, be carried through with the same force; that which has the greatest capillary ascension, — that is, which will rise the highest in a capillary tube,— will pass through in the greatest quantity, and cause an accumulation of liquid in the opposite side. The facts and arguments adduced by Prof. Mitchell, clearly ex- hibit, that imbibition and transudation are dependent upon the penetrativeness of the liquid, and the penetrability of the mem- brane : that if two liquids, of different rates of penetrativeness, be placed on opposite sides of an animal membrane — " they will in time present the greater accumulation on the side of the less pene- trant liquid, whether more or less dense; but will, finally, thoroughly and uniformly mix on both sides; and at length, if any pressure exist on either side, yield to that and pass to the other side."a In all such cases, there is both endosmose and exosmose; in other words, a certain quantity of one fluid passes in, and a certain quan- tity of the other passes out.b As a general rule, the imbibition takes place from the rarer to the denser medium; from pure water or dilute solutions towards those that are more concentrated. Yet there are exceptions to this. It would appear, indeed, that the stronger current is always from the medium which has the strongest affinity for the substance of the septum. It is well known, for exam- ple, that in the case of a mixture of dilute alcohol covered over by a piece of bladder, the alcohol becomes concentrated, owing to the water — a denser fluid — passing more rapidly through the septum or bladder than the alcohol; but if the same mixture be tied over with elastic gum, the contrary effect will be produced — the alcohol will escape in greater quantity.0 A portion of the communication of Prof. Mitchell relates to an analogous subject, to which, as M. Magendied has observed, little or no attention has been paid by physiologists — the permeability of membranes by gases. " The laminae," Magendie remarks, " of which membranes are constituted, are so arranged that the gases can penetrate them, as it were, without obstacle. If we take a bladder, and fill it with pure hydrogen gas, and afterwards leave it in contact with atmospheric air, in a very short -time the hydro-' » See also Amer. Journal of the Medical Sciences for November, 1833, p. 100. b Magendie, Legons sur les Phenomenes Physiques de.la Vie, torn. i. p. 99, Paris, 1836-38. c Henle, Allgem. Anat., or Jourdan's French Translat., p. 210, Paris, 1843; and Wagner, Elements of Physiology, by Willis, p. 438, Lond. 1842. <• Precis Elementaire de Physiologie, 2de edit. 1825, i. 13 ; and Legons, &c. torn. i. p. 132. 46 MATERIAL COMPOSITION OF MAN. sen will have lost its purity, and will be mixed with the atmo- spheric air, which has penetrated the bladder. This phenomenon is the more rapid in proportion as the membrane is thinner and less dense. It presides over one of the most important acts of life __respiration — and it continues after death." Prof. Mitchell is the first individual, who directed his observa- tion to the relative penetrativeness of different gases. This he was enabled to discriminate by the following satisfactory experiment, which we give in his own words : " Having constructed a syphon of glass, with one limb three inches long, and the other ten or twelve inches, the open end of the short leg was enlarged and formed into the shape of a funnel, over which, finally, was firmly tied a piece of thin gum elastic. By inverting this syphon, and pouring into its longer limb some clear mercury, a portion of com- mon air was shut up in the short leg, and was in communication with the membrane. Over this end, in the mercurial trough, was placed the vessel containing the gas to be tried, and its velocity of penetration measured by the time occupied in elevating to a given degree the mercurial column in the other limb. Having thus com- pared the gases with common air, and subsequently, by the same instrument, and in bottles, with each other, I was able to arrange the following gases according to their relative facility of transmis- sion, beginning with the most powerful: ammonia, sulphuretted hydrogen, cyanogen, carbonic acid, nitrous oxide, arsenuretted hydrogen, olefiant gas, hydrogen, oxygen, carbonic oxide,and nitro- gen." He found that ammonia transmitted in one minute as much in volume as sulphuretted hydrogen did in two minutes and a half; cyanogen,\n three minutes and a quarter; carbonic acid,in five minutes and a half; nitrous oxide, in six minutes and a half; arsenuretted hydrogen, in twenty-seven minutes and a half; olefiant gas, in twenty-eight minutes ; hydrogen, in thirty-seven minutes and a half; oxygen, in one hour and fifty-three minutes; and carbonic oxide, in two hours and forty minutes. It was found, too, that up to a pressure of sixty-three inches of mercury, equal to more than the weight of two atmospheres, the penetrative action was capable of conveying the gases — the subjects of the experiment —into the short leg through the gum elastic mem- brane. Hence, the degree of force exerted in the penetration is considerable. The experiments were all repeated with animal membranes, such as dried bladder and gold-beater's skin, moistened so as to re- semble the natural state. The same results, and in the same order followed as with the gum elastic. The more fresh the membrane! the more speedy and extensive was the effect; and in living ani- mals the transmission was very rapid. To these experiments we shall have frequent occasion to refer in the course of this work.a » See, connected with this subject, the ingenious papers by Dr. Robert E. Rogers ?si ^'Z^, f°rmer m the Ame»ca" Jo»™al of the Medical Science" Ma? 1836 p. 13; and the latter in the same Journal for August, 1836, p. 276 ; Nov IS??' p. 122; and Aug. 1838, p. 302. * ad7> FUNCTIONS OF MAN. 47 All these different properties of animal solids are independent of the vital properties. They continue for some time after the total extinction of life in all its functions, and appear to be connected either with the physical arrangement of molecules, the chemical composition of the substance in which they reside, or with pecu- liar properties in the body that is made to act on the tissue. They do not, indeed, seem to be affected, until the progress of decompo- sition has become sensible. Hence, many of these agencies have been termed collectively, by Haller, the vis mortua. II. FUNCTIONS OF MAN. Having described the intimate structure of the tissues, we pass to the consideration of the functions, the character of each of which is, — that it fulfils a special and distinct office in the economy, for which it has an organ or an instrument or an evident apparatus of organs. Physiologists have not, however, agreed on the number of distinct offices which are so performed; and hence the differ- ence, in the number and classification of the functions, that prevails amongst them. The oldest division is into the vital, natural, and animal; the vital functions including those of such importance as not to admit of interruption, such as circulation, respiration, and innervation; the natural functions including those that effect nu- trition, as digestion, absorption, and secretion; and the animal, those possessed exclusively by animals, as sensation, locomotion, and voice. This classification is the basis of that which generally prevails at the present day. The character of this work will not admit of a detail of every classification which has been proposed by the physiologist; that of Bichat, however, has occupied so large a space in the public eye, that it cannot well be passed over. It is the one followed by Richerand,a and by many modern writers. Bichat includes all the functions under two heads, according as they work to one or other of two ends, —functions of nutrition or life of the indivi- dual, and functions of reproduction or life of the species. Nutri- tion requires that the being shall establish relations around him to obtain the materials of which he may stand in need ; and, in ani- mals, the functions, which establish such relations, are under the volition and perception of the being. Hence they are divided into two sorts; those that commence or precede nutrition, consist of external relations, are dependent upon the will, and executed with consciousness; and those that are carried on within the body, spontaneously, and without consciousness. Bichat adopted this basis, and to the first aggregate of functions he applied the term ani- mal life, because it comprised those that characterize animality ; the latter he called organic life, because the functions comprised under it are common to every organized body. Animal life included sensation, motion, and expression; organic life, digestion, ab- a Nouveaux Elemens de Physiologie, 13eme edit, par M. Berard, aine, edit. Beige. p. 42, Bruxelles, 1837 ; or Amer. reprint of Copland's edit, of De Lys's translation, New York, 1836. 4g FUNCTIONS OF MAN. sorption, respiration, circulation, nutrition, secretion &c. In a"1JJlal life Bichat recognised two series of actions, opposed to, eaeft otner, the one proceeding from without and terminating in the brain, or passing from circumference to centre, and comprising the external senses! the other, commencing in the brain, and acting on external bodies, or proceeding from centre to circumference and including the internal senses, locomotion, and voice. The brain, in which one series of actions terminates and the other begins, he considered the centre of animal life. In organic life, he likewise recognised two series of actions ; the one proceeding from without to within and effecting composition; the other passing from within to without, and effecting decomposition. In the former, he included digestion; absorption; respiration, by which the blood is formed; the circu- lation, by which the blood is conveyed to different parts; and the functions of nutrition, and calorification. In the latter, that ab- sorption, which takes up parts from the body; the circulation, which conducts those parts or materials to the secretory or depu- ratory organs; and the secretions, which separate them from the economy. In this kind of life, the circulation is common to the two movements of composition and decomposition; and as the heart is the great organ of the circulation, he considered it the centre of organic life ; and, lastly, as the lungs are united both with animal life, in the reception of air, and with organic life, as the organs of sanguification, Bichat regarded those organs as the bond of union between the two lives. Generation constituted the life of the species. The classification, adopted in this work, will be that embraced by Magendie ;a and, after him, by Adelon,b who has written one of the best systems of human physiology which we possess. The first class, ox functions of relation or animal functions, includes those that establish our connexion with the bodies surrounding us; the sensations, voluntary motions, and expressions. The second class, or functions of nutrition, comprises digestion, absorption, respiration, circulation, nutrition, calorification, and secretion: and the third class, the functions of reproduction,—generation. TABLE OP THE FUNCTIONS. C 1. Sensibility. I. Animal or of Relation. < 2. Muscular Motion. (_ 3. Expression or Language. 4. Digestion. 5. Absorption. Functions. <^ ^ 6. Respiration. II. Nutritive. < 7. Circulation. 8. Nutrition. 9. Calorification. 10. Secretion. III. Reproductive. 11. Generation. In studying each of these functions, we shall first of all describe the organ or apparatus concerned in its production; but so far only as is necessary in a physiological point of view, and shall next a Precis, &c. i. 32. •> Physiologic de l'Homme, 2de 6dit., i. 116, Paris, 1829. FUNCTIONS OF MAN, 49 detail what has been called the mechanism of the function, or the mode in which it is effected. In many cases it will happen, that some external agent is concerned in its production, as light in vision; sound in audition ; odours in olfaction ; tastes in gusta- tion, &c. The properties of these agents will, in all instances, be detailed in a brief manner, and as far only as is requisite for the immediate purpose. The difficulty of observing actions, that are carried on by the very molecules of which the organs are composed, has given rise to many hypothetical speculations, some of which are sufficiently ingenious ; others too fanciful to be indulged, by the reflecting, for a moment ; and, as might be expected, the number of these fan- tasies generally bears a direct proportion to the difficulty and obscurity of the subject. It will not be proper to pass over the most prominent of these, but they will not be dwelt upon ; whilst the results of direct observation and experiment will be fully de- tailed ; and where differences prevail amongst observers, such differences will be attempted to be reconciled, where practicable. The functions, executed by different organs of the body, can be deduced by direct observation, although the minute and molecular action, by which they are accomplished in the very tissue of the organ, may not admit of detection. We see, for example, blood proceeding to the liver, and the vessels that convey it ramifying in the texture of the viscus, and becoming so minute as to escape vision, even when aided by a powerful microscope. We find, again, other canals in the organ becoming perceptible, gradually augmenting in size, and ultimately terminating in a larger duct, which opens into the small intestine. If we examine each of these orders of vessels in their most minute appreciable ramifications, we discover, in the one, always blood, and, in the other, always a very different fluid, — bile.. We are hence led to the conclusion, that in the intimate tissue of the liver, and in some part communicating directly or indirectly with both these orders of vessels, bile is sepa- rated from the blood ; in other words, that the liver is the organ of the biliary secretion. On the other hand, functions exist, which cannot be so demonstratively referred to an organ. We have every reason for believing, that the brain is the exclusive organ of the mental and moral manifestations; but, as few opportunities occur for seeing it in action, and as the operation is too molecular to admit of direct observation when we do see it, we are compelled to con- nect the organ and function by a process of reasoning only; yet we shall find, that the results, at which we arrive in this manner, are often by no means the least satisfactory. The forces that preside over the various functions are either gene- ral,— that is, physical or chemical; or special, —that is, organic or vital. Some of the organs afford us examples of purely physi- cal instruments. We have, for instance, in the eye, an eye-glass, if we may so call it, of admirable construction; in the organ*of voice, an instrument of music ; in the ear, one of acoustics ; the vol. i. — 5 50 NERVOUS SYSTEM. circulation is carried on through an ingenious hydraulic apparatus, and station and progression involve various laws of mechanics. i> many of the functions, again, we have examples ot cneiaiun agency, whilst all those, in which innervation is concerned, we are incapable of explaining on any physical or chemical principle, and are constrained to esteem vital. BOOK I. ANIMAL FUNCTIONS OR FUNCTIONS OF RELATION. The functions of relation consist,/^, of sensibility, and secondly, of muscular motion, including expression or language. All these actions are subject to intermission, constituting sleep; a condi- tion which has, consequently, by many physiologists, been investi- gated under this head; but as the functions of reproduction are also influenced by the same condition, the consideration of sleep will be deferred until the third class of functions has engaged attention. CHAPTER I. OF SENSIBILITY OR THE FUNCTION OF THE SENSATIONS. Sensibility is the function by which an animal experiences feel- ing, or has the perception of an impression. In its general accep- tation, it means the property possessed by living parts of receiving impressions, whether the being, exercising the property, have con- sciousness of it or not. To the first of these cases — in which there is consciousness — Bichat gave the epithet animal; to the second, organic ; the latter being common to animals and vegetables, and presiding over the organic functions of nutrition, absorption, ex- halation, secretion, &c.; the former existing only in animals, and presiding over the sensations, internal as well as external. Animal sensibility will be considered here. Pursuing the plan already laid down, the study of this interest- ing and elevated function will be commenced, by pointing out, as far as may be necessary, the apparatus that effects it, which com- prises the whole nervous system. 1. OF THE NERVOUS SYSTEM. Under the name nervous system anatomists include all those or- gans, that are composed of the nervous or pulpy tissue. In man, it is constituted of three portions ; first, of what has been called the cerebrospinal axis, a central part having the form of a long cord, expanded at its superior extremity, and contained within the cavi- ties, of the cranium and spine; secondly, of cords, called nerves, in number thirty-nine pairs, according to some, — forty-two, accord- ENCEPHALON. 51 ing to others, — passing laterally between the cerebro-spinal axis and every part of the body ; and, lastly, of a nervous cord, situate on each side of the spine, from the head to the pelvis, forming ganglia opposite each vertebral foramen, and called the great sym- pathetic. 1. Of the Encephalon. — Under this term are included the con- tents of the cranium, namely, the cerebrum or brain proper ; the cerebellum or little brain, and the medulla oblongata. These various parts have been included by some under the name of brain. When we look at a section of the encephalon, and at the three organs in their natural position, we find many distinct parts, and appearances of numerous and separate organs. So various, in- deed, are the prominences and depressions observable on the dis- section of the brain, that it is generally esteemed one of the most difficult subjects of anatomy; yet, owing to the attention paid to it in all ages, it is now one of the structures best understood by the anatomist. This complicated organ affords us a striking illustra- tion of the truth, that the most accurate anatomical knowledge will not necessarily teach the function. The elevated actions, which the encephalon has to execute, have, indeed, attracted a large share of the attention of the physiologist, — too often, however, without any satisfactory result; yet it may, we think, be safely asserted, that we have become better instructed regarding the uses of par- ticular parts of the brain, within the last few years, than during y the whole of the century preceding. The encephalon being of extremely delicate organization, and its functions easily deranged, it was necessary that it should be se- curely lodged and protected from injuries. Accordingly, it is placed in a round, bony case ; and, by an admirable mechanism, is de- fended against damage from surrounding bodies. Amongst these guardian agents or tutamina cerebri must be reckoned; — the hair of the head, the skin, muscles, pericranium, bones of the skull, the diploe separating the two tables of which the bones are composed, and the dura mater. It is not an easy matter to assign probable uses to the hair on various parts of the body. On the head, its function seems more readily appropriable. It deadens the concussion, which the brain would experience from the infliction of heavy blows, and prevents the skin of the scalp from being injured by the attrition of bodies. In military service, the former of these uses has been taken ad- vantage of, and an arrangement, somewhat similar to that which exists naturally on the head, has been adopted with regard to the helmet. The metallic substance, of which the ancient and modern helmets are formed, is readily thrown into vibration; which vi- bration, being communicated to the brain, might, after heavy blows, derange its functions more even than a wound inflicted by a sharp instrument. To obviate this, in some measure, the helmet has been covered with horse-hair; an arrangement which pre- vailed in the helmet worn by the Roman soldier. There can be no 52 NERVOUS SYSTEM. doubt, likewise, that being bad conductors of caloric, and forming a kind of felt which intercepts the air, the hairs may tend to pre- serve the head of a more uniform temperature. They are, more- over, covered with an oily matter, which prevents them from im- bibing moisture, and causes them to dry speedily. Another use, ascribed to them by Magendie,a is somewhat more hypothetical ;— that, being bad conductors of electricity, they may put the head in a state of insulation, so that the brain may be less affected by the electric fluid ! It is unnecessary to explain in what manner the differentlayers of which the scalp is composed, the cellular membrane beneath, the panniculus carnosus or occipito-frontalis muscle, and the peri- cranium covering the bone, act the parts of tutamina. The most important of these protectors is the bony case itself. In an essay written by one of the most distinguished physiologists of the present day,b we have some beautiful illustrations of the wisdom of God as displayed in the mechanism of man, and of his skull in particular; and although some of his remarks may be liable to the censures which have been passed upon them by Dr. Arnott,c most of them are admirably adapted to the contemplated object. It is impos- sible, indeed, for the uninitiated to rise from the perusal of his interesting essay, without being ready to exclaim with the poet, " how wonderful, how complicate is man ! how passing wonder He that made him such !" Sir Charles Bell attempts to prove, that the best illustration of the form of the head is the dome; whilst Dr. Arnott considers it to be " the arch of a cask or barrel, egg-shell, or cocoa-nut, &c, in which the tenacity of the material is many times greater than necessary to resist the influence of gravity, and comes in aid, therefore, of the curve, to resist forces of other kinds approaching in all directions, as in falls, blows, unequal pressures," &c. The remarks of Dr. Arnott on this subject are just; and it is owing to this form of the cranium, that any blow received upon one part of the skull is rapidly distributed to every other ; and that a heavy blow, inflicted on the forehead or vertex, may cause a fracture, not in the parts struck, but in the occipital or sphenoidal bones. The skull does not consist of one bone, but of many. These are joined together by sutures, — so called from the bones seeming as if they were stitched together. Each bone consists likewise of two tables ; an external,fibrous and tough, and an internal, of a harder character and more brittle, hence called tabula vitrea. The two tables are separated from each other by a cellular or cancellated structure, called diplo'd. On examining the mode in which the tables form a junction with each other at the sutures, we find ad- ditional evidences of design exhibited. The edges of the outer a Precis Ele"mentaire, edit. cit. i. 177. b Sir Charles Bell, in Animal Mechanics — Library of Useful Knowledge, London c Elements of Physics, or Natural Philosophy, General and Medical, London 1827 — reprinted in this country, with notes by Dr. Hays. Philad. 1841. ENCEPHALON. 53 Fi-. 1. Front view of the Skull. 1. Frontal portion of the frontal bone. b %The 2 immediately over the root of the nose, een refers to the nasal tuberosity; the 3 over table are serrated, and so arranged as to be accurately dove-tailed into each other; the tough fibrous tex- ture of the external plate being well adapted for such a junction. On the other hand, the tabula vitrea, which, on account of its greater hardness, would be liable to frac- ture, to chip off, is merely united with its fellow at the suture, by what is called harmony : the ta- bulae are, in other words, merely placed in contact. The precise object of these sutures is not apparent. In the mode in which ossification takes place in the bones of the skull, the radii from different ossific points must ne- cessarily meet by the "law of con- jugation," in the progress of ossifi- cation. This has, by many pctppmprl thp paiKP r>f thp snfnrp<5 the orbit, to the supraorbital "ridge. 4. Optic esteemed me cause 01 ine buuues, foramfin 5. sphenoidal fissure; 6. spheno- but the explanation IS insufficient, maxillary fissure. 7. Lachrymal fossa in the TT r . , ., -i • 1 c lachrymal bone, the commencement of the HoWSOeVer It may be, the Kllld Ot nasalduct. Flares 4,5, 6,7, are within the innptinn nfTnrrI<5 an pvamnlp of hpail- orbit- 8. Opening of the anterior nares.di- juncrion anoras an example ui ueciu- vided int0tvvopartsbythe vomer; thenum- tiful adaptation. During the foetal bers placed upon the latter. 9. Infra-orbi- , r n <-> . tal foramen. 10. Malar bone. 11. Sym- State, the SUtUreS dO not eXISt. 1 hey physis of the lower jaw. 12. Mental fora- „-„ fnllrr fnrmprl in vnnth avp rli<5 mel1, 13. Ramusof thelowetjaw. 14. Pa- are lUlly IOrmea in yOUin, aie Q1S- rietalbone. IS. Coronal suture. IG. Tem- tinct in the adult age, but, in after i»rai bone. n. squamous suture, 18 u> xw " b J > per part ofthegreat alaofthe sphenoid bone. periods Of life, become entirely Obll- 19. Commencement of the temporal ridge. T . i .1 i ^1 r • ^•J 20. Zygoma of the temporal bone assisting terated,the bone then forming a solid t0 form the zygomatic arch. 21. Mastoid spheroid. It does not seem, however, v™ess.-(mison.) that after the sutures are established, any displacement of the bones can take place ; and observation has shown, that they do not pos- sess much, if any, effect in putting a limit to fractures. In all cases of severe blows,"the skull appears to resist as if it were constituted of but one piece. But the separation of the skull into distinct bones, which have a membranous union, is of striking advantage to the foetus in parturition. It enables the bones to overlap each other ; and, in this way, to occupy a much smaller space than if ossification had united them, as in after life. It has, indeed, been imagined by some, that there is this advantage in the pressure made on the brain by the investing bones,—that the foetus does not suffer from the violent efforts made to extrude the child; but that during the passage through the pelvis, it is in a state of for- tunate insensibility; and, that pressure suddenly exerted upon the brain is attended with these effects is well known to the patholo-. 5* 54 NERVOUS SYSTEM. gist. It is, indeed, the great principle to be borne in mind in the management of apoplexy, fracture of the skull, &c. The uses of the diploe, which separates the two tables ot the skuii, are not equivocal. Composed of a cancellated structure, it is well adapted to deaden the force of blows; and as it forms, at the same time, a bond of union and of separation, a fracture might be in- flicted upon the outer tahle of the skull, and yet be prevented from extending to the tabula vitrea. Such cases have occurred, but they are rare. It will generally happen, that a blow, intended to cause serious bodily injury, will be sufficient to break through both tables or neither. Lastly, the dura mater, which has been reckoned as one of the tutamina cerebri, lines the skull, and constitutes a kind of internal periosteum to it. It may also be inservient to useful purposes, by deadening the vibrations, into which the head may be thrown by sudden concussions ; as the vibrations of a bfell are arrested by lining it with some soft material. It is chiefly, however, to protect the brain against itself, that we have the arrangement, which prevails. The cerebrum, as well as the cerebellum, consists of two hemi- spheres ; and its posterior part is situate immediately above the cerebellum. It is obvious, then, that without some protection, the hemisphere of one side would press upon its fellow, when the head is inclined to the opposite side ; and that the posterior lobes of the upon Fig. 2. brain would weigh the cerebellum in the erect attitude. The hemispheres are separated from each other by the falx cerebri, in the upper margin of which is the superior longitudinal sinus. The falx passes between the hemispheres. The tentorium cerebello super externum — a pro- longation of the dura mater — passes horizon- tally forwards so as to sup- port the posterior lobes of the brain, and prevent them from pressing inju- riously on the cerebellum. A process of the dura mater passes also between the hemispheres of the cerebellum. Independ- ently of the protection af- t1 A , 1 forded to the encephalon, the dura mater lodges the great sinuses into which the veins dis- Falx Cerebri and Sinuses of Upper and Back part of Skull. 1. Superior longitudinal sinus. 2, 2. Cerebral veins opening into the sinus from behind forwards. 3. Falx cere- bri. 4. Inferior longitudinal sinus. 5. Straight or fourth sinus. 6. The vena; Galeni. 7. Torcular Herophili. 8. Two lateral sinuses, with the occipital sinuses between them 9. lerrnination of the inferior petrosal sinus of one side. 10 Dilatations corresponding with the jugular fossa:. 11. in- ternal jugular veins.—{Wilson.) ENCEPHALON. 55 charge their blood. These different sinuses empty themselves into the torcular Herophili or confluence of the sinuses, and ultimately proceed to constitute the lateral sinuses, which pass through the temporal bone, and form the internal jugular veins. The tutamina are not confined to the contents of the cranium. The spine appears to be, if possible, still better protected. In the skull, we see a firm, bony case ; in the spine, a structure admitting considerable motion of the parts, without risk of pressure to the spinal marrow. Accordingly, the spine consists of numerous distinct bones or vertebras, with fibro-cartilaginous — techni- cally called intervertebral — sub- stances placed between each,so that, although the extent of motion be- tween any two of these bones may be small, the amount, when all are concerned, is considerable. The great use of this intervertebral sub- stance is to prevent the jar, that would necessarily be communicated to the delicate parts within the cavities of the spine and cranium, were the spine composed entirely of one bone. In falls from a height, upon the feet or breech, these elastic cushions are forcibly compressed, but they immediately re- turn to their former condition, and deaden the force of the shock. - In this they are aided by the curvatures of the spine, which give it the shape of the Italic s, and enable it to resist — in the same man- ner as a steel spring — any force acting upon it in a longitudinal direction. So well is the medulla spinalis protected by the strong bony processes jutting out in various directions from the spine, that it is extremely rare to meet with lesions of the part; and it is comparatively of late years that any ex professo treatises have ap- peared on the subject. Besides the protection afforded by the bony structure to the deli- cate medulla, Magendiea has pointed out another, which he was the first to detect. The canal, formed by the dura mater around the spinal cord, is much larger than is necessary to contain that organ; but, during life, the whole of the intermediate space is filled with a serous fluid, which strongly distends the membrane, so that it will frequently spirt out to a distance of several inches, when a puncture is made in the membrane. To this fluid he has given the » Precis, &c. edit. cit. i. 181. Fig. 3. Sinuses of the Base of the Skull. 1. Ophthalmic veins. 2. Cavernous sinus of one side. 3. Circular sinus ; the figure oc- cupies the position of the pituitary gland in the sella turcica. 4. Inferior petrosal sinus. 5. Transverse or anterior occipital sinus. 6. Superior petrosal sinus. 7. Internal jugular vein. 8. Foramen magnum. 9. Occipital si- nuses. 10. Torcular Herophili. 11,11. Lateral sinuses.—{Wilson.) 56 NERVOUS SYSTEM. epithet cephalo-spinal; and he conceives, that it may act as one o the tutamina of the marrow, (which is, as it were, suspenueu the fluid,) and exert upon it the pressure necessary for the neaiu y performance of its functions. . Beneath the dura mater is situate a very delicate membrane, me arachnoid, belonging to the class of serous membranes. It sur- rounds the encephalon in every part, but is best seen at the pase of the brain. Its chief use is to secrete a thin fluid, to lubricate the brain. This membrane enters into all the cavities of the organ, and in them fulfils a like function. When the fluid accumulates to a great extent, we have the disease called hydrocephalus chro- nicus. . , . Anatomists usually describe a third tunic of the brain — the pia mater. This is generally conceived to consist of the minute ter- minations of the cerebral arteries, and those of the corresponding veins, forming, at the surface of the brain, a vascular network, which passes into the cavities; and, in the ventricles, forms the plexus choroides, and tela choroidea. The dura and pia mater were so called, by the older anatomists, be- cause they were con- ceived to be the origin of all the other mem- branes of the body. The cerebrum or brain proper has the form of an oval, larger behind. On its outer surface are various un- dulating eminences, called convolutions, because they have been thought to re- semble the folds of the intestines—separated Fig. 4. Longitudinal Section of the Brain on the Mesial line. The incision has been carried along the m ddle line; between the two hemispheres of the cerebrum, and through the middle of r U *li V» the cerebellum and medulla oblongata. 1. Inner surface of the irom eaCU Omer Dy left hemisphere. 2. Divided surface of the cerebell the arbor vit See, on the Histology, of.the Organic or Sympathetic Nervous Fibres, Mr. Paget, Brit, and For. Med. Rev. July, 1842, p. 279. <= Cerebri Anatome, cui accessit Nervorum Descriptio, &c. Lond. 1664, cap. xxvi. <> De Vera Nervi Intercostalis Origine, Gutting. 1793; Collect. Dissert. Anat. ii. 939 ; and Oper. Minor, i. 503. e See, Appendix to Eng. edit, by Dr. Copland. f Lecons d'Anatomie Compar. Introd. p. 26. s Dissert, de Structura Usiique Gangliorum, ad J. B. Morgagnium, in Morgagni Adver. Anat. v. 101, Lugd. Bat. 1741. 68 NERVOUS SYSTEM. Scarpaa treats them as synonymous with plexuses, being, according to him, plexuses with the filaments in close approximation ; and the plexuses he regards as ganglions, whose filaments are more separated. He consequently believes, with many physiologists, that their office is to mix and unite various nervous filaments with each other. Dr. Wilson Philipb thinks, that they are secondary sources of nervous influence, the specific office of which is to re- ceive supplies of it from all parts of the brain and spinal marrow, and to transmit their united influence to the organs to which the nerves are distributed, whilst some conceive that at least one office is to communicate irritability to the tissues.0 The views of John- stone,11 Reil,e Bichat/ and others, is, that their use is to render the organs which derive their nerves from them, independent of the will. Although connected with the brain by the branches of the fifth and six pairs of encephalic nerves, and with the spinal cord by the spinal nerves, the sympathetic does not appear to be directly influenced by either; as the functions of the parts to which its ramifications are distributed can continue for some time after both brain and spinal marrow have been separated; nay, as in the case of the heart and intestines, after they have been removed from the body. Yet many discussions have been indulged regard- ing the origin of this important part of the nervous system ; some assigning it to the brain, others to the spinal marrow, whilst others again, with more justice,,esteem it a distinct nerve, communicat- ing with the brain and spinal cord, but not originating from either ; receiving, according to Broussais,s by the cerebral nerves, the stimulant influence, and applying it to movements which are in- dependent of the centre of perception. In like manner, Broussais affirms, when irritation predominates in the viscera, it is conveyed by the ganglionic to the cerebral nerves, which transmit it to the brain. The point is still sub lite. Reil and Bichat, esteeming this nerve to be the great nervous centre of involuntary functions, have termed it the organic nervous system, in contradistinction to the animal nervous system, which presides over the animal func- tions ; whilst Lobstein,h who has published an ex professo work on the subject, assigns three functions to it. 1. To preside over * De Nervis Comment, cap. ii. 320. t Philosoph. Transact, for 1829 ; and Inquiry into the Nature of Sleep and Death Lond. 1834, p. 14. * ' Fletcher, Rudiments of Physiology, P. ii. a. p. 68, Edinb. 1836. d Philosophical Transactions, vols. 54, 57, and 60 ; Essays on the Use of the Gan- glions of the Nerves, Shrewsbury, 1771; and Medical Essays and Observations relating to the Nervous System, Evesham, 1795. e Archiv. fur die Physiol, p. 226, vii. Halle, 1807. f Anatomie Generate, torn. i. 200, and ii. 405. s A Treatise on Physiology applied to Pathology, translated by Drs. John Bell and R. La Roche, p. 257, Philadelphia, 1832. h De Nervi Sympath. Human. &c. translated by Dr. Pancoast, Philadelphia 1831 • also, Copland, in London Medical Repository, for 1822, and in Richerand's Phy'siolo"v (Appendix); Brachet, Hecherches Experimentales, &c. Paris, 1830, and Bluff art. Ganglicn-system, in Encyclopiid Wbrterb. der Medicin. Wissensch. xiii IM Berlin, 1835. °'' GREAT SYMPATHETIC. 6.9 nutrition, secretion, the action of the heart, and the circulation of the blood: 2. To maintain a communication between different organs of the body ; and 3. To be the connecting medium between the brain and abdominal viscera. Remak,a who believes that the animal economy possesses two sensoriums, — the one that of the cerebro-spinal axis, the other that of the ganglionic system,— considers, that as in the cerebro-spinal system of nerves two orders of phenomena occur, — the perception of sensation, and the reaction or reflection of volition, so in the organic nervous system two analogous actions take place, — organic perception, or, as it has been called, Hallerian irritability, and reaction or the function of organic reflection, as shown by J. Miiller.b From his own researches, Dr. Carpenter0 infers, that the sympa- thetic system does not exist in the lowest classes of animals in a distinct form, — that the nervous system ofthe invertebrata, taken as a whole bears no analogy to it, and that as the divisions of this become more specialized, some appearance of a separate sympa- thetic presents itself, but this is never so distinct as in the verte- brata ; hence he deduces, and with every probability, that as the sympathetic system is not developed in proportion to the predomi- nant activity of the functions of organic life, but in proportion to the development of the higher division of the nervous system, its office is not to preside over the former, but to bring them in rela- tion with the latter; so that the actions of the organs of vegetative life are not dependent upon it, but influenced by it", in accordance with the operations of the system of animal life. Again, the great sympathetic is esteemed to be the visceral nerve, par excellence, or the nerve that supplies the different vis- cera with their nervous influence, — a part • of its office as the nervous system of involuntary functions; for different offices of the viscera are carried on independently of volition. On examining the course of the great sympathetic, we find many filaments pro- ceeding from the cervical and thoracic ganglions, interlacing and forming the cardiac plexus,from which the nerves of the heart and great vessels arise. The same thoracic ganglions furnish a branch to each intercostal artery. A nerve of the great sympathetic — called the great splanchnic ox visceral — proceeding from some of the thoracic ganglions, passes through the pillars ofthe diaphragm into the abdomen, and terminates in the large plexus or ganglion, called the semilunar, and this, by uniting with its fellow of the opposite side, constitutes the still more extensive interlacing, the solar plexus. From this, numerous filaments proceed, which — by accompanying the coronaria ventriculi, hepatic, splenic, spermatic, a Ammon's Monatschrift, June, 1840; and Edinb. Med. and Surg. Journal, Jan. 1841, p. 249. b Elements of Physiology, by Baly, i. 736, Lond. 1838. <= Dissertation on the Physiological Inferences to be deduced from the Structure of the Nervous System in the Invertebrated Classes of Animals, Edinb. 1839 ; reprinted in Dunglison's Med. Library Edit. Philad. 1839 ; also, his Principles of Human Phy- siology, p. Ill, Lond. 1842. 70 NERVOUS SYSTEM. renal, superior and inferior mesenteric, and hypogastric arteries — are distributed to the parts that are supplied with blood by these arteries, — the stomach, liver, spleen, testes, kidneys, intestines, &c. Weber,a however, a German anatomist of distinction, who ex- mined the great sympathetic in different animals, has afforded rea- son for believing that the splanchnic may not be the sole visceral nerve, but that the eighth pair may share in the function. He states, that the great sympathetic is less developed, the lower the animal; whilst the eighth pair is more and more developed as we descend in the scale, and at length is the only visceral nerve in some of the mollusca. Sir A. Cooper'sb experiments satisfied him that this nerve is very essential to the digestive process ; but of this we shall have to speak hereafter. In the prosecution of those experiments, he found, that when the great sympathetic was tied on a dog, but little effect was induced ; the animal's heart appeared to beat more quickly and feebly than usual; but of this circum- stance he could not be positive on account of the natural quickness of its action. The animal was kept seven days, at which time one nerve was ulcerated through, and the other nearly so, at the situation of the ligatures. Another animal was still living when he wrote, on which the sympathetic had been tied nearly a month before. When the pneumogastric or eighth pair, the phrenic, and the great sympathetic were all tied on each side," the animal lived little more than a quarter of an hour, and died of dyspnoea."0 These experiments would appear to show, either that the great sympathetic is not so indispensable to the economy as has been imagined, or that it is in every part of it a generator of nervous influence, so that if its connexion with the brain or any other viscus be destroyed, the divided portions may still possess the power of generating nervous agency. But if we admit this as regards the system of the great sympathetic, we shall find,, that it is difficult to extend it to detached portions of the nervous system of animal life. According to the experiments of Flourens,d the semilunar is the only ganglion which exhibits any great sensibility, and hence it has been considered as a sort of intervention to connect the viscera with the encephalon. Lepelletiere thinks we are justified in dividing the nerves into. five classes: — the first, comprising the nerves of special sensibi- lity—the olfactory, optic, lingual branch of the fifth pair, and the auditory : — the second, the nerves of general sensibility, the fifth pair; and the spinal nerves, through their posterior root:__the third, comprising the voluntary motors, the spinal nerves, by their anterior roots, the motore s oculorum or common oculo-muscular * Anatom. Comparat. Nerv. Sympath. Lips. 1817; and Hildebrandt's Handbuchder Anatomie des Menschen, 4te Ausgabe, von E. H. Weber, Band. iii. Braunschweig 1831 b Guy's Hospital Reports, vol. i. p. 457, London, 1836. c ibid. p. 471. * Recherches Experimentales sur les Proprietes et les Fonctions du Sys'teme Ner- veux, &c, 2d edit. p. 229, Paris, 1842. J 'Traite de Physiologie Medicale et Philosophique, torn. 3, p. 250, Paris, 1832. DR. M. HALL'S DIVISION. 71 the external oculo-muscular, and the hypo-glossal: — the fourth, instinctive motors, involuntary, respiratory nerves of Sir Charles Bell, the pathetic, facial glosso-pharyngeal, pneumogastric, and spinal accessory ; and the fifth, nerves of vital association and nutrition — the filaments and plexuses of the ganglionic system. Dr. Fletcher* adopts a different arrangement. He divides the nerves into ganglionic and cerebro-spinal; the latter being subdi- vided into the respiratory, motiferous, sensiferous, and regular; the last including those which communicate both the faculty of sen- sibility and the stimulus of volition. GANGLIONIC. Those immediately connected respectively with The Ophthalmic, The Cavernous, The Otic, The Sphenopala- tine, The Sub-maxillary, The three Cervical, The Cardiac, The twelve Dorsal, The Coeliac, The five Lumbar, The five Sacral, and The Coccygeal Ganglions, CEREBRO-SPINAL. ^\_ RESPIRATORT. The Pathetic, The Facial, The Glosso- pharyngeal, The Pneumo- gastric, The Accessory, The Phrenic, and The External Respiratory, MOTIFEROUS. SENSIFEROUS. The Motor oculi, The Olfactory, A part of the The Optic, lower maxil- The Ophthalmic lary branch of branch of the REGULAR. The Sub occi- pital, The seven Cer- vical, The twelve Dor- The five Lum- bar, The five Sacral. the Trigemi- Trigeminus, nus, The upper Max- The Abductor, illary branch The Hypoglos- of the Trige- sal, minus, A part of the lower Maxil lary branch of the Trigemi nus, The Auditory. Dr. Marshall Hall,b has proposed another division of the ner- vous system, which is calculated to explain many of the anomalous circumstances we so frequently witness. He proposes to divide all the nerves into 1. The cerebral or the sentient and voluntary. 2. The true spinal or excito-motory. 3. The ganglionic or the nutrient and secretory. If the sentient and voluntary functions be destroyed by a blow upon the head, the sphincter muscles will still contract when irri- tated, because the irritation is conveyed to the spine, and the reflex action takes place to the muscle so as to throw it into contraction. But if the spinal marrow be now destroyed, the sphincters remain entirely motionless, because the centre of the system is destroyed. Dr. Hall thinks, that a peculiar set of nerves constitute, with the true spinal marrow as their axis, the second subdivision of the ner- vous system ; and as those of the first subdivision are distinguished into sentient and voluntary, these may be distinguished into the ex- citor and rnotory. The first, ortheexcitor nerves, pursue their course principally from internal surfaces, characterised by peculiar excita- bilities, to the true medulla oblongata and spinalis ; the second or • Rudiments of Physiology, P. ii. a. p. 71. Edinb. 1836. b Lectures on the Nervous System, London, 1836, and American Edit. Philad. 1836. Also his Lectures on the Theory and Practice of Medicine, in the London Lancet, for Feb. 3, and Feb. 7, 1838. 72 NERVOUS SYSTEM. the motor nerves pursue a reflex course from the medulla to the muscles, having peculiar actions concerned principally in ingestion and egestion. The motions connected with the first or cerebral sub- division are sometimes,—indeed frequently,—spontaneous ; those connected with the true spinal are, he believes, always excited. Dr. Hall thinks, too, that there is good reason for viewing the fifth, and posterior spinal nerves as constituting an external gan- glionic system for the nutrition of the external organs ; and he pro- poses to divide the ganglionic subdivision of the nervous system, into l,the zWerraa/ganglionic, which includes that usually denomi- nated the sympathetic, and probably filaments of the pneumogas- tric; and 2, the external ganglionic, embracing the fifth and pos- terior spinal nerves. To the cerebral system he assigns all dis- eases of sensation, perception, judgment, and volition — therefore all painful, mental, and comatose, and some paralytic diseases. To the true spinal or excito-motory system, belong all spasmodic and certain paralytic diseases. He properly adds, that these two parts of the nervous system influence each other both in health and disease, as they both influence the ganglionic system.3 The views of Dr. Hall on the excito-motory function, have been embraced by MUller,b Grainger,0 Carpenter,d and others. Dr. Car- penter infers from his inquiries, that the actions most universally performed by a nervous system are those connected with the in- troduction of food into the digestive cavity, and that we have rea- son to regard this class of actions as everywhere independent of volition, and perhaps also of sensation — the propulsion of food along the oesophagus in man being of this character ; — that for the performance of any action of this nature, a nervous circle is requisite, consisting of an afferent nerve, on the peripheral extre- mities of which an impression is made, — a ganglionic centre, where the white fibres of which that nerve consists terminate in gray matter, and those of the efferent nerve originate in like man- ner; and an efferent trunk conducting to the contractile structure the motor impulse, which originates in some change between the gray and white matter; —that in the lowest animals such actions constitute nearly the entire function of the nervous system, —the amount of those involving sensation and volition being very'small • but as we ascend the scale, the evidence of the participation of true sensation in the actions necessary for acquiring food, as shown by the development of special sensory organs, is much greater • but that the movements immediately concerned with the intro- duction of food into the stomach remain under the control of a separate system of nerves and ganglia, to the action of which the influence ofthe cephalic ganglia — the special if not the only seat oLrinTciplf °f the The°ry and Practice "f Medicine, by Marshall Hall MD PR« P"- H' Yu^Z' Pt7' an,d Ame\6f • by DrS" Bi^'^ and Holmes Bost 1839 •' b Handbuch der Physiologie, s. 333, and 688, Coblentz, 1835 1837 or thp £« r u translation, by Dr. Baly, i. 707, London, 1838 ' hngllsh c o„ the structure and Functions of the Spinal Cord, London, 1837. See also Wistar s Anatomy, by Pancoast, n. 558, Philad. 1843. d Qp *?' 1S0' NERVOUS SYSTEM. 73 of sensibility and volition —is not essential; — that, in like man- ner, the active movements of respiration are controlled by a sepa- rate system of nerves and ganglia, and are not dependent upon that of sensation and volition, although capable of being influenced by it; — that whilst the actions of these systems are, in the lower tribes, almost entirely of a simply reflex character, we find them, as we ascend, gradually becoming subordinate to the will; and that this is effected by the mixture of fibres proceeding directly from the cephalic ganglia with those arising from their own cen- tres ; — that the locomotive organs, in like manner, have their own centres of reflex action, which are independent ofthe influence of volition, perhaps also of sensation; — that the influence of the will is conveyed to them by separate nervous fibres, proceeding from the cephalic ganglia, and that similar fibres probably con- vey to the cephalic ganglia the impressions destined to produce sensations; — that the stomato-gastric, respiratory, and locomotive centres are all united in the spinal cord of the vertebrata, where they form one continuous ganglionic mass, and that the nerves connected with all these likewise receive fibres derived imme- diately from the cephalic ganglia; — and 1 aft ly, that whenever peculiar consentaneousness of action is required between different organs, their ganglionic centres are united more or less closely; and that the trunks themselves are generally connected by bands of communication. On the whole, in the present state of our knowledge, we are justified, perhaps, in adopting the systematic summary ofthe func- tions of the nervous system, and the general purposes to which it is inservient, as given by the writer last cited.a 1. The nervous system receives impressions, which, being conveyed by its afferent fibres to the sensorium, are there communicated to the conscious mind ; and are inservient, in some manner, to the acts of that mind. As the results of these acts, a motor impulse is transmitted along efferent nerves to particular muscles, which excites them to con- traction. Of these acts the encephalon, and nerves communicating with it, are the organs. 2. Certain parts of the nervous system receive impressions, which are propagated along afferent fibres that terminate in ganglionic centres distinct from the sensorium. In these, a reflex motor impulse is thus excited, which is trans- mitted along efferent trunks proceeding from those centres, and ex- cites muscular contraction without any necessary intervention of sensation or volition. The organs of this function are the gray matter ofthe spinal cord, which is not continuous with the fibrous structure ofthe brain, and the trunks connected with it. It is the true spinal or excito-motory system of Dr. Hall, already referred to. 3. There is yet a division of the nervous system, which appears to have for its object to combine and harmonize the muscular movements immediately connected with the maintenance of or- ganic life. It may likewise influence, and connect with each other a Human Physiology, p. 79, Lond. 1842. VOL. I. --7 74 NERVOUS SYSTEM. the functions of nutrition, secretion, &c; although these — like the muscular movements immediately connected with the mainte- nance of organic life — are unquestionably essentially independent of it; and — as has been shown — can be carried on where it does not exist. The organ of these acts is the great sympathetic. From all that has been said, it will be understood, that each nerve as it issues from the spinal canal must be composed of vari- ous fasciculi:—one, sensory, or of sensation, connected with the pos- terior medullary tract continuous with the medullary matter of the brain ; another, connected with the anterior medullary tract, and conveying the influence of volition from the brain along the spinal cord and nerves to the muscles; a third, consisting of excitor fibres, terminating in the gray matter of the cord, and conveying impressions to it; and a fourth, consisting of motor fibres, arising from the gray or ganglionic matter of the cord, and conveying the influence reflected to the muscles. Much, doubtless, however, still remains to be accomplished, before we can consider these views established. Like many important questions of physiology, they may be regarded as in somewhat of a transition state ; but the zeal and activity of physiological inquirers are daily throwing light upon many obscure points; and of these there is none surrounded with more obscurity than the physiology of the ner- vous system. All the parts that have been described as constituting the nervous system — brain, cerebellum, medulla spinalis, and nerves—are formed of the primary nervous fibre, the nature of which has been already described. The neurine or substance of which they are constituted is soft and pulpy, but the consistence varies in different portions, and, in the whole, at different ages. In the foetus it is almost fluid ; in youth, of greater firmness ; and of still greater in the adult. This softness of structure in the encephalon of the foetus is by no means inutile. It admits of the pressure, which takes place to a greater or less extent, in all cases of parturition, whilst the head is passing through the pelvis, without the child sustaining any injury. On examining, however, the consistence of different brains, it is necessary to inquire into the period that has elapsed since the death ofthe individual, as the brain loses its firmness by being kept, and ultimately becomes semi-fluid. It is likewise ren- dered fluid by disease, constituting the ramollissement du cerveau, or mollescence ofthe brain, to which the attention of pathologists has been directed of late years, but without much important advan- tage to science. When the encephalon is fresh, it has a faint, spermatic, and some- what tenacious smell. This, according to Chaussier, has persisted for several years in brains that have been dried. The substance, of which the nervous system is composed, has been subjected to analysis by Vauquelin,a and found to contain, water, 80-00; white fatty matter, 4-53; red fatty matter, called » Annales de Chim. lxxxi. 37; and Annals of Philosophy, i. 332. NERVOUS TISSUE. 75 cerebrine, 0-70; osmazome, 1-12; albumen, 7-00; phosphorus, 1-50; sulphur, acid phosphates of potassa, lime, and magnesia, 5-15. M. Couerbe's analysis of the braina gives, 1. A pulverulent yel- low fat, stearconote; 2. An elastic yellow fat, cerancephalote ; 3. A reddish-yellow oil, eleancephol; 4. A white fatty matter, cere- brote, the white fatty matter of Vauquelin, the myelocone of Kiihn ; 5. Cerebral cholesterine — cholesterote; and the salts found by Vauquelin, lactic acid, sulphur and phosphorus, which form a part of the fats above mentioned.b In the spinal cord, there is more fatty matter, and less osmazome, albumen, and water. In the nerves the albumen predominates, and the fatty matters are less in quantity. Researches by Lassaigne show, that water constitutes Aths of the nerves, and T87ths of the brain ; whilst the proportion of albumen, in the former, is f2^ths ; in the latter, T^ths. He found the different parts of the brain to be composed as follows: The -whole Brain. Water, 770 Albumen. 9-6 White fatty matter, 7-2 Red fatty matter, 3-1 Osmazome, lactic acid and salts, 20 Earthy phosphate, 1*1 White portion. Gray portion 730 85-0 99 75 13-9 1-0 0-9 3-7 1-0 1-4 1-3 1-2 100-0 100-0 100-0= Raspail,d has pointed out two other differences. First, when a nerve is left upon a plate of glass in a dry air, it becomes dry, with- out putrefying, whilst the cerebral substance putrefies in twenty- four hours; and secondly, this dried nerve has all the physical characters of the corneous substances, — nails, hair, and other analogous bodies ; and in their chemical relations, he says, these bodies do not differ sufficiently to repel the analogy. Neither the chemical analysis of the nervous system, nor inquiry into its minute structure by the aid ofthe microscope, has, however,thrown light upon the wonderful functions executed by this elevated part of the economy. It would seem, that nervous matter is, in composition, interme- diate between fat and the compounds of protein ; containing azote, which is not present in fats, but in smaller proportion than pro- tein ; and, on the other hand, being much richer in carbon than protein or its compounds. Phosphorus, too, appears to be an essential ingredient. According to recent researches by Fremy, brain appears to contain a peculiar acid, analogous to the fatty a Annales de Chimie et de Physique, lvi. 160. b For John's Analysis of the white and gray cerebral matter, see Journal de Chimie M^dicale, Aout, 1835. c Journal de Chim. Me"dic.; and Pharmaceutisches Central Blatt, Nov. 19,1836, s. 765. Valentin, Hirn-und Nervenlehre, Leipzig, 1841; or French Translation, by Jourdan, p. 129, Paris, 1843. d Chimie Organique, p. 217, Paris, 1833. 76 NERVOUS SYSTEM. acids, which he calls cerebric acid, and which contains azote and phosphorus : this is mixed with an albuminous substance, with an oily acid — the oleo-phosphoric— with cholesterine, and finally, with small quantities of olein and margarin, and of oleic and mar- garic acids.a To the naked eye, the neurineor nervous substance appears under two forms, the one gray, and of a softer conststence ; the other white, and more compact. The former is called the cortical, cineritious, or pulpy substance ; the latter, the white, medullary, ox fibrous, also termed tubular in consequence of its being supposed to consist of tubes of great minuteness, which are filled with a kind of granular pith that can be squeezed from them — a view which is adopted by most histologists. Dr. James Stark has,b however, recently affirmed; as the result of his examination, that the matter which fills the tubes is of an oily nature, differing, in no essential respect, from butter or soft fat, and remaining of a fluid consistence during the life of the animal, or whilst it retains its natural temperature, but becoming granular or solid when the animal dies. The diameter of these cylindrical tubuli has been estimated to vary from about the T^th to the ^pth of a line. The nerves are wholly com- posed of it.c The gray substance is not always, however, at the exterior, nor the medullary in the interior. In the medulla spi- nalis, their situation is the reverse of what it is in the brain. In the invertebrata, the gray matter forms the nuclei of the gan- glia, which are the centres of the nervous system ; and the true spinal system, which occupies the interior of the spinal cord, has been regarded as a chain of similar ganglia. It is the organ, as already shown, of the excito-motory nervous function. Ruysch con- sidered, that the gray portion owes its colour to the blood- vessels which enter it ;d and, in this opinion, Haller, Adelon,e and others/concur, but this is not probable, and it has been by no means demonstrated. The medullary portion has the appearance of being fibrous, and it has been so regarded by Leeuenhoek,s Vieussens, Steno,and by Gall and Spurzheim.h Malpighi' believed the gray cortical substance to be an assemblage of small follicles, intended to secrete the nervous fluid, and the white medullary sub- stance to be composed of the excretory vessels of these follicles; and an analogous view is entertained by most physiologists of the present day — the gray matter being regarded as the generator of a Journ. des Connois. Med. Chir. Jan. 1841; also Turner and Liebig's Chemistrv 7th edit. p. 1195, Lond. 1842. B ^uermsiry, b Proceedings ofthe Royal Society. No. 56, Lond. 1843. c See, on the Histology of the Different Parts of the Nervous System Mr Paget Brit and For. Med. Rev. July, 1842, p. 282 ; and Henle, Allgemeine Anatomie, u.'a w" S. 616, Leipzig, 1841. "' * Oper. Amstel. 1727. e Physiologie de l'Homme, 2de edit, vol. i. Paris 1829 t Carpenter, Human Physiology, p. 81, Lond. 1842. g Philos. Transact. 1677, p. 899. «■ Recherches sur le Systeme Nerveux en general, et sur celui de Cerveau en parti- cuher, avec figur. Pans, 1809. v*ni i Oper. Malpighii, and Mangeti Bibl. Anat. i. 321. CIRCULATION IN THE ENCEPHALON. 77 the nervous influence —the white matter as chiefly concerned in its conduction. Gall and Spurzheim conjecture, that the use ofthe cine- ritious is, to be the source or nourisher of the white fibres. The facts, on which they support their view, are, that the nerves appear to be enlarged when they pass through a mass of cineritious matter, and that masses of this substance are deposited in all parts of the spinal cord where it sends out nerves; but Tiedemanna has remarked, that in the foetus the medullary is developed before the cortical portion, and he conceives the use of the latter to be — to convey arterial bloody which may be needed by the medullary portion for the due execution of its functions. Sir Charles Bellb affirms, that he has found, at different times, all the internal parts ofthe brain diseased, without loss of sense, but that he has never seen disease general on the surface ofthe hemi- spheres without derangement or oppression of mind during the patient's life ; and hence he concludes, that the cineritious matter of the brain is the seat of the intellect, and the medullary of the subservient parts. A similar use has been ascribed to the cineri- tous portion, from pathological observations, by MM. Foville and Pinel Grandchamp.c This view would afford considerable sup- port to the opinions of Gall, Spurzheim, and others, who consider the organs of the cerebral faculties to be constituted of expansions ofthe columns of the spinal marrow and medulla oblongata, and to terminate by radiating fibres on the periphery of the brain ; as well as of Desmoulins,d and those who regard the convolutions as the seat of mind. We have, however, cases on record, which signally conflict with this view of the subject; cases in which the cortical substance has been destroyed, and yet the moral and intellectual manifestations have been little, if at all, injured. Many years ago the author dissected the brain of an individual of rank in the British army of India, the anterior lobes of which were in such a state, that neither medullary nor cortical portion could be dis- tinguished, both one and the other appearing to be broken down into a semi-purulent, amorphous fluid; yet the intellectual facul- ties had been nearly unimpaired, although the morbid process must have been of considerable duration. . The encephalon affords us many striking instances of the differ- ent effects produced by sudden and by gradual interference with its functions. Whilst a depressed portion of bone or an extravasa- tion of blood may suddenly give rise to the abolition of the facul- ties, the gradual compression, produced by a tumour, may scarcely interfere with any of its manifestations. The circulation of blood in the encephalon requires mention. The arteries are four in number, — two internal carotids, and two vertebrals ; to these may be added the spinal artery or middle * Anatomie und Bildungsgeschichte des Gehirns, mit Tafeln. Niirnberg, 1816. b Anatomy and Physiology, 5th American edit, by J. D. Godman, p. 29, New York, 1827. c Sur le Systeme Nerveux, Paris, 1820. d Anatomie des Systemes Nerveux des Animaux a Vertebres, p. 599, Paris, 1825. 78 NERVOUS SYSTEM. Fig. 9. artery ofthe dura mater or arteria meningasa media. The carotid ar- teries enter the head through the carotid ca- nals, which open on each side of the sella turcica, or of the chiasma of the optic nerves. The ver- tebral arteries enter the head through the fora- men magnum of the oc- cipital bone; unite on the medulla oblongata to form the basilary ar- tery, which passes for- ward along the middle of the pons varolii, and, and at the anterior part of the pons, gives off' la- teral branches, which in- osculate with corres- ponding branches of the carotids, and form a kind of circle at the base of the brain, which has been called the circulus arteriosus of Willis. The passage of the bloodvessels is extreme- ly tortuous, so that the blood does not enter the brain with great impe- tus ; and the vessels be- come capillary before they penetrate the organ, — an arrangement of essential importance, when we regard the large amount of blood sent to it. This has been estimated as high as one-eighth of the whole fluid transmitted from the heart. The amount does not admit of accurate appreciation, but it is considerable. It must of course vary according to circumstances. In hypertrophy of the heart, the quantity sent is sometimes increased; as well as in ordi- nary cases of what are called determinations of blood to the head. Here, too large an amount is sent by the arterial vessels; but an equal accumulation may occur, if the return of the blood from the head, by means of the veins, be in any manner impeded, — as when we stoop, or compress the veins of the neck by a tight cravat, or by keeping the head turned for a length of time. Congestion or accumulation of blood may therefore arise from very different causes, Circle of Willis. The branches of the arteries have references only on one side, on account of their symmetrical distribution. 1. Ver- tebral arteries. 2. Two anterior spinal branches uniting to form a single vessel. 3. One of the posterior spinal ar- teries. 4. Posterior meningeal. 5. Inferior cerebellar. 6. The basilar artery giving off its transverse branches to either side. 7. Superior cerebellar artery. 8. Posterior cerebral. 9. Posterior communicating branch of the inter- nal carotid. 10. Internal carotid, showing the curvatures it makes within the skull. 11. Ophthalmic artery divided across. 12. Middle cerebral artery. 13. Anterior cerebral arteries connected by, 14. Anterior communicating artery. — (.Wilson.) CIRCULATION IN THE ENCEPHALON. 79 Sir Astley Coopera found by experiment, that the vertebral arte- ries are much more important vessels as regards the brain and its functions in certain animals, as the rabbit, than the carotid. The nervous power is much lessened by tying them ; and, in his experiments, the animals did not, in any case, survive the operation more than a fortnight. In the dog, also, he tied the carotids with little effect, but the ligature of the vertebrals had a great influence. The effect of the operation was to render the breathing immediately difficult and laborious, owing, in Sir Astley's opinion, to the supply of blood to the phrenic nerves, and the whole tractus respiratorius of Sir Charles Bell, being cut off. The animal became dull, and in- disposed to make use of exertion, or to take food. Compression of the carotids and the vertebrals at the same moment in the rabbit de- stroyed the nervous functions immediately. This was effected by the application of the thumbs to both sides of the neck, the trachea re- maining quite free from pressure. Respiration entirely ceased, with the exception of a few convulsive gasps. The same fact was evinced in a clearer and more satisfactory manner by the application of liga- tures to the four vessels, all of which were tightened at the same instant. Stoppage of respiration and death immediately ensued. The cerebral, like other arteries, are accompanied by branches of the great sympathetic. The encephalic veins are disposed as al- ready mentioned, terminating in sinuses formed by the dura mater, and conveying their blood to the heart by means of the lateral sinuses and internal jugulars. No lymphatic vessels have been detected in the encephalon; yet, that absorbents exist there is proved by the dissection of apoplectic and paralytic individuals. In these cases, when blood is effused within the brain, the red parti- cles are gradually taken up, with a portion of the fibrinous part of the blood, leaving a cavity called an apoplectic cell, which is at the same time the evidence of previous extravasation and of subsequent absorption. When the skull of the new-born infant, which, at the fontanelles, consists of membrane only — or the head of one who has received an injury, that exposes the brain — is examined,two distinct move- ments are perceptible. The one, which is generally obscure, is synchronous with the pulsation of the heart and arteries ; the other, much more apparent, is connected with respiration, the organ seem- ing to sink down at the time of inspiration, and to rise during expi- ration. This phenomenon is not confined to the brain, but exists likewise in the cerebellum and spinal marrow. The motion of the encephalon, synchronous with that of the heart, admits of easy explanation. It is owing to the pulsation of the circle of arteries at the base of the brain elevating the organ at each systole of the heart. The other movement is not so readily intelligible. It has been attributed to the resistance, experienced by the blood in its pas- sage through the lungs during expiration, owing to which an accu- mulation of blood takes place in the right side of the heart; this a Guy's Hospital Reports, i. 472, London, 1836. 80 NERVOUS SYSTEM. extends to the veins and to the cerebral sinuses, and an augmenta- tion of bulk is thus occasioned. We shall see hereafter, that one of the forces conceived to propel the blood along the vessels is at- mospheric pressure. According to that view, the sinking down of the brain, during inspiration, is explicable: the blood is rapidly drawn to the heart; the quantity in the veins is consequently dimi- nished, and sinking down ofthe brain succeeds. On dissection, we find that the encephalon fills the cavity of the cranium ; during life, therefore, it must be pressed upon, more or less, by the blood in the vessels, and by the serous fluid exhaled by the pia mater into the subarachnoid tissue. From thence it penetrates into the ventricles,— according to Magendie, at the lower end ofthe fourth ventricle, at the calamus scriptorius. The quantity varies according to the age and size ofthe patient, and usually bears an in- verse proportion to the size ofthe encephalon. It is seldom, how- ever, less than two ounces, andoftenamounts to five. Magendie is of opinion, that the fluid is secreted by the pia mater, and states, that it may be seen transuding from it in the living animal. The results of chemical analysis appear to show, that it differs much from mere serum. It is obviously, however, almost impracticable — if not wholly so—to separate the consideration of this fluid from that met with in the cavity of the arachnoid. The spinal marrow, as we have seen, does not fill the vertebral canal, but the cephalo-spinal fluid exerts upon it the necessary pressure; added to which, the pia mater seems to press more upon this organ than upon the rest of the cerebro-spinal system. A cer- tain degree of pressure appears, indeed, necessary for the due per- formance of its functions, and if this be either suddenly and con- siderably augmented, or diminished, derangement of function is the result. Magendie,3 however, asserts, that he has known ani- mals, from which the fluid had been removed, survive without any sensible derangement of the nervous functions. It is this fluid, which is drawn off by the surgeon when he punctures in a case of spina bifida. When the brain is examined in the living body, it exhibits pro- perties, which, some years ago, it would have been esteemed the height of hardihood and of ignorance to ascribe to it. The opinion has universally prevailed, that all nerves are exquisitely sensible. Many opportunities will occur for remarking whether this senti- ment be founded on fact; but we are now prepared to assert, that even the encephalon itself, — the organ in which perception takes place, — is insensible, in the common acceptation of the term; that is, we may prick, lacerate, cut, and even cauterize it, yet no painful impression will be produced. Experiment leaves no doubt regarding the truth of this, and we find the fact frequently con- firmed by pathological cases. * Precis Elementaire, seconde edit. i. 192 ; and Recherches Physiologiques et Cli- mquessur le Liquide Cephalo-rachidien ou Cerebro-spinal. Paris, 1842 ; analysed in Brit a?duF™ v ed." J*eV" f°r 0ct- 184*' P' 462' See' also' Ur- Skinner, in Amer. J-ournai ofthe Medical Sciences, for Nov. 1836, p. 109. PROPERTIES OF THE CEREBRAL SUBSTANCE. 81 Portions of brain may be discharged from a wound in the skull, and yet no pain be evidenced. In his " Anatomy and Physiology," Sir C. Bella remarks, that he cannot resist stating, that on the morn- ing on which he was writing, he had had his finger deep in the an- terior lobes ofthe brain, when the patient, being at the time acutely sensible, and capable of expressing himself, complained only of the integument. A pistol-ball had passed through the head, and Sir Charles having ascertained that it had penetrated the dura mater by forcing his finger into the wound, trepanned on the op- posite side ofthe head, and extracted it. By the experiments, instituted by Magendieb and others, it has been shown, that an animal may live several days, and even weeks, after the hemispheres have been removed; nay, that in certain animals, as reptiles, no change is produced in their habitudes by such abstraction. They move about as if unhurt. Injuries of the surface of the cerebellum exhibit, that it also is not sensible to that kind of irritation; but deeper wounds, and especially those that interest the peduncles, have singular results, — to be explained hereafter. The spinal cord is not exactly circumstanced in the same manner. Its sensibility is very exquisite on the posterior surface ; much less on the anterior, and almost null at the centre. These columns, as we have seen, have been esteemed the origins of the nerves of sensibility, motion, and respiration. Considerable sensibility is also found within, and at the sides of, the fourth ven- tricle ; but this diminishes as we proceed towards the anterior part of the medulla oblongata, and is very feeble in the tubercula qua- drigemina ofthe mammalia. It has been shown, that the spinal nerves, by means of their posterior roots, convey general sensibility to the parts to which they are distributed. But there are other nerves, which, like the brain, are themselves entirely devoid of general sensibility. This has given occasion to a distinction of nerves into those of general and of special sensibility. As nerves, which must be considered insensible or devoid of general sensibility, may be instanced the optic, olfactory, and auditory. Each of these has, however, a spe- cial sensibility, and although they may exhibit no pain when irri- tated, they are capable of being impressed by appropriate stimuli, as by light, in the case of the optic nerve ; by odours, in that of the olfactory; and by sound, in that of the auditory. Yet we shall find, that every nerve of special sensibility seems to require the influence of a nerve of general sensibility, the fifth pair. Many other nerves appear devoid of sensibility, as the third, fourth, and fifth pairs ; the portio dura ofthe seventh ; the ninth pair of encephalic nerves; and as has been shown, all the anterior roots of the spinal nerves. The parts of the encephalon, concerned in muscular motion, will fall under consideration hereafter. 1 5th Amer. edit, by J. D. Godman, ii. 6, 1827. See, also, Sir E. Home's Lectures on Compar. Anat. ii. 93, Lond. 1823. b Precis Elementaire, i. 335. 82 SENSATIONS. 2. PHYSIOLOGY OF SENSIBILITY. Sensibility we have defined to be — the function by which an animal experiences feeling, or has the perception of an impression. It includes two great sets of phenomena, the sensations, properly so called, and the intellectual and moral manifestations. These we shall consider in succession. a. Ofthe Sensations. A sensation is the perception of an impression made on some organ ; or, in the language of Gall, it is the perception of any irri- tation whatever. By the sensations we receive a knowledge of what is passing within or without the body ; and, in this way, our notions or ideas of them are obtained. When these ideas are re- flected upon, and compared with each other, we exert thought and judgment; and they can be recalled, with more or less vivid- ness and accuracy, by the exercise of memory. The sensations are numerous, but they may all be comprised in two divisions,—the external and the internal. Vision and audition afford us examples of the former, in which the impression, made upon the organ, is external to the part impressed. Hunger and thirst are instances of the latter, the cause here being internal, neces- sary, and depending upon influences seated in the economy itself. Let us endeavour to discover in what they resemble each other. In the first place, every sensation, whatever may be its nature,— external, or internal,— requires the intervention of the encephalon. The distant organ, — as the eye orear, — may receive the impres- sion, but it is not until this impression has been communicated to the encephalon, that sensation is effected. The proofs of this are easy and satisfactory. If we cut the nerve proceeding to any sensible part, if we put a ligature around it, or compress it in any manner ; it matters not that the object, which ordinarily excites a sensible impression, be applied to the part, no sensation is experienced. Again, if the brain, the organ of perception, be prevented in any way from acting, it matters not that the part impressed, and the nerve communicating with it, are in a condition necessary for the due performance of the function, sensation is not effected. We see this in numerous instances. In pressure on the brain, occasioned by fracture of the skull, or in apoplexy, a disease generally depend- ent upon pressure, we find all sensation, all mental manifestation, lost; and they are not regained until the compressing cause has been removed. The same thing occurs if the brain be stupified by opium, or any other narcotic ; and, to a less degree, in sleep, or when the brain is engaged in intellectual meditations. Who has not found, that in a state of reverie or brown study, he has succeeded in threading his way through a crowded street, carefully avoiding every obstacle, yet so little impressed by the objects around him as not to retain the slightest recollection of them ? On the other hand, how vivid are the sensations when the attention is directed to them \ Again, we have numerous cases in which the brain itself engen- SENSATIONS. 83 ders the sensation, as in dreams, and in insanity. In the former we see, hear, speak, make use of every one of our senses apparently, yet there has been no impression from without. Although we may behold in our dreams the figure of a friend long since deceased, there can obviously be no impression made on the retina from without.* The whole history of spectral illusions, of morbid hallucinations, and maniacal phantasies, is to be accounted for in this manner. Whether, in such cases, the brain reacts upon the nerves of sense, and produces an impression upon them from within, similar to what they experience from without during the production of a sensation, will form the subject of future inquiry. Pathology also affords several instances where the brain engenders the sensation, most of which are precursory signs of cerebral derangement. The appear- ance of spots flying before the eyes, of spangles, depravations of vision, of hearing, &c, and a sense of numbness in the extremities, are referable to this cause, as well as the singular fact well known to the operative surgeon, that pain is often felt in a particular part of a limb, years after the limb has been removed from the body.b These facts prove, that every sensation, although referred to some organ, must be perfected in the brain. The impression is made upon the nerve of the part, but the appreciation takes place in the common sensorium. There are but few organs ofthe body, which could be regarded insensible, provided we were aware of the precise circumstances under which their sensibility is elicited. The old doctrine — as old indeed as Hippocrates0 —was, that the tendons and other membra- nous parts are among the most sensible organs of the body. This opinion was implicitly credited by Boerhaave, and his follower Van Swieten,d and in many cases had a decided influence, on sur- gical practice especially. As the bladder consists principally of membrane, it was agreed for ages by lithotomists, that it would be improper to cut or divide any part of it; and therefore, in order to extract the stone, dilating instruments were used, which caused the most painful lacerations of the parts implicated in the operation. Haller6 considered the tendons, ligaments, periosteum, bones, meninges of the brain, different serous membranes, arteries and veins, entirely insensible ; yet we know, that these parts are ex- quisitely sensible when attacked with inflammation. One of the most painful affections to which man is liable is the variety of whitlow that implicates the periosteum; and in all affections of the bone, which inflame or press forcibly upon that membrane, we have excessive sensibility exhibited. It would appear, that the possession of vessels or of vascularity is a necessary condition of the sensibility of any tissue. Many parts, too, are affected by special irritants ; and, after they have appeared insensible to a multitude of agents, will show great * Adelon, Art. Encephale (Physiologie) in Diet, de Med. vii. 514, Paris, 1823, and Physiol, de l'Homme, torn. i. p. 239, 2de edit. Paris, 1829. b Porterfield on the Eye, i. 364. c Foesii fficonom. Hippocr. " N«vg Aphorism. 164, and Comment. e Oper. Minor, torn. i. 84 SENSATIONS. sensibility when a particular irritant is applied. Bichat endeavoured to elicit the sensibility of ligaments in a thousand ways, and with- out success ; but when he subjected them to distension or twisting, they immediately gave evidence of it. It is obvious, then, that be- fore we determine that a part is insensible, we must have submitted it to every kind of irritation. Adelon affirms, that there is no part but what may become painful by disease. From this assertion the cuticle might safely be excepted. If we are right, indeed, in our view of its origin and uses, as described hereafter, sensibility would be of no advantage to it, but the contrary. In the present state, then, of our knowledge, we are justified in asserting, that bones, cartilages, and membranes are not sensible to ordinary ex- ternal irritation, when in a state of health, or in other words, that we are not aware of the irritants, which are adapted to exhibit their sensibility. That sensibility is due to the nerves distributed to a part is so generally admitted as not to require comment. It is true, ho wever, that such sensibility is by no means in proportion to the number of nerves it may receive. Nay, some parts are acutely sensible in disease into which nerves cannot be traced. To explain these cases, Reila supposed, that each nerve is surrounded at its termination by a nervous atmosphere, by which its action is extended beyond the part in which it is seated. This opinion is a mere creation of the imagination. We have no evidence of any such atmosphere, and it is more philosophical in us to presume, that the reason we do not discover nerves in these parts may be owing to the imperfec- tion of our vision. We may conclude, then, that the action of impression occurs in the nerves of the part to which the sensation is referred. As to the mode in which this impression affects the nerves we are ignorant. Microscopic examination of the nerves connected with sensory organs would seem to show, that they come into relation with a substance very analogous to the gray matter of the ence- phalon, although its elements are somewhat differently arranged. The nervous fibres, too, appear to terminate in close approximation with a vascular plexus ; and a granular structure is always present, which— as in the cortical portion of the brain — seems to be in- termediate. This point has been regarded as the origin of the afferent fibres; and as the seat of changes that are made by ex- ternal impressions.b The facts, already mentioned, show, that the action of percep- tion takes place in the brain, and that the nerve is merely the con- ductor of the impression between the part impressed and that organ. If a ligature be put round a nerve, sensation is lost below the liga- ture, but it is uninjured above it. If two ligatures be placed, sen- sibility is lost in the portion included between the ligatures, but it is restored if the upper ligature be removed. The spinal marrow » Exercitat. Anatom. Fascic. i. p. 28, and Archiv. fur die Physioloeie, B. iii. b Carpenter, Human Physiology, p. 85, Lond. 1842. SENSATIONS. 85 is sensible along the whole of its posterior column, but it also acts only as a conductor of the impression. Flourens destroyed the spinal cord from below, by slicing it away, and he found that sen- sibility was gradually extinguished in the parts corresponding to the destroyed medulla, but that the parts situate above evidently continued to feel. Perception, therefore, occurs in the encephalon; and not in the whole,but in some of its parts. Many physiologists, amongst whom may be mentioned Haller, Lorry, Rolando, and Flourens,3 have sliced away the brain, and found that the sensations con- tinued until the knife reached the level of the corpora quadrigemina; and again it has been found, that if the spinal cord be sliced away from below upwards, the sensations persist until we reach the me- dulla oblongata. It is, then, between these parts, that we must place the cerebral organs ofthe senses, and it is with thispart ofthe cephalo- spinal axis, that the nerves of the senses are found to communicate. Mr. Lawrence5 saw a child with no more encephalon than a bulb, which was a continuation for about an inch above the fora- men magnum ofthe medulla spinalis, and with which all the nerves from the fifth to the ninth pair were connected. The child's breath- ing and temperature were natural; it discharged urine and faeces ; took food, and at first moved very briskly. It lived four days. If we divide the posterior roots of the spinal nerves and the fifth pair, all general sensibility is lost; but if we divide the nerves of the senses, we destroy only their functions. We can thus under- stand why, after decapitation, sensibility may still remain for a time in the head. It is instantly destroyed in the trunk, owing to the removal of all communication with the encephalon; but the fifth pair remains entire in the head, as well as the nerves ofthe organs of the senses. Death must of course follow almost instantaneously from loss of blood, but there is doubtless an appreciable space, during which the head may continue to feel, or in other words, during which the external senses may act.c M. Julia Fontanelled has indeed concluded, from a review of all the observations made on this matter, that, contrary to the common opinion, death by the guillotine is one ofthe most painful, that could be invented; that the pains of decollation are horrible, and endure even until there is an entire extinction of animal heat! It need scarcely be said, that all these inferences are imaginative, and perhaps equally fabu- lous with the oft told story of Charlotte Corday scowling at the executioner after her head was removed from the body by the guillotiue; and this conclusion is strongly confirmed by the results of experiments,—on a robber who was beheaded with the sword, * Rolando, Saggio sopra la vera Struttura del Cervello, Sassari, 1809 ; and Flourens Recherches Experimentales sur les Proprietes et les Fonctions du Systeme Nerveux, &c. 2de e\lit. Paris, 1842. b Medico-Chirurg. Transact, v. 166. c Berurd, Rapports du Physique et du Moral, p. 93, Paris, 1823. > Traite de Physiologie, &c., Paris, 1822; or translation by Drs. Bell and La Roche, 3d Amer. edit. p. 63, Philad. 1832. c See Fletcher's Rudiments of Physiology, P. ii. b. p. 68, Edinb. 1836. NERVOUS FLUID. 87 tweenthe different parts of the nervous system ; the second regards the nerves as cords, and the transmission as effected by means of the vibrations or oscillations of these cords; whilst the third ascribes it to the operation of electricity. 1. The hypothesis of animal spirits has prevailed most exten- sively. It was the doctrine of Hippocrates, of Galen, ofthe Ara- bians, and of most of the physicians of the last centuries. Des- cartes^ adopted it energetically, and was the cause of its more ex- tensive diffusion. The great grounds, assigned for the belief, were, first, that as the brain receives so much more blood than is neces- sary for its own nutrition, it must be an organ of secretion ; secondly, that the nerves seem to be a continuation ofthe medullary matter of the brain ; and it has already been remarked, that Mal- pighi considered the cortical part of the brain to be follicular, and the medullary to consist of secretory tubes. It was not unnatural, therefore, to regard the nerves as vessels for the transmission of these spirits. As, however, the animal spirits had never been met with in a tangible shape, ingenuity was largely invoked in sur- mises regarding their nature ; and, generally, opinions settled down into the belief, that the fluid was of an ethereal character. For the various views, that have been held upon the subject, the reader is referred to Haller,b who was himself an ardent believer in the existence of the animal spirits, and has wasted much time and space in an unprofitable inquiry into their nature. The truth is, that we have not sufficient evidence, direct or indirect, of the ex- istence of any nervous fluid ofthe kind described. Allusion has been already made to the views, in regard to the tubular struc- ture of the white neurine, admitted by most observers; Berres,0 however, affirms, that the forms, in which the nervous substance presents itself under the -magnifying glass, can only be compared to those of canals and vesicles; but whether they be hollow he does not attempt to decide. Raspaild has concluded, that the opi- nion of their being hollow, and containing a fluid, is unsupported by facts, for although he admits, that Bogrose succeeded in injecting the nerves with mercury, he thinks, that the passage of the metal along them was owing to its having forced its way by gravity. Raspail found the nerve, under the microscope, presenting a homo- geneous structure, without the slightest trace of solution of conti- nuity. We have, in truth, no reason for considering the brain the organ of any ponderable secretion. Yet the term " animal spirits," although their existence is not now believed in, adheres to us in popular language. We speak of a man who has a great flow of animal spirits, but without regarding the hypothesis whence the expression originated. * Tractatus de Homine, § 14. b Elementa Physiologic, x. 8. c Oesterreich. Med. Jahrbuch, vol. ix., and Brit, and Foreign Med. Review, January, 1838, p. 219. d Chimie Organique, p. 218. Paris, 1833. e See, on the tubular arrangement of the Nerves, Brit, and For. Med. Rev Jan 1838 p. 293; Oct. 1839, p. 394; and April, 1839, p. 500; Elements of Physiology by j' Miiller, translated by W. Baly, M.D., i. 633, Lond. 1838; and Mr. Paget Brit ami For. Med. Rev. July, 1842, p. 278. 8 ' 88 SENSATIONS. The term nervous fluid is still constantly used by physiologists. By this, however, they simply mean the medium of communication or of conveyance, by which the nervous influence is carried, with the rapidity of lightning, from one part of the system to another, but without committing themselves as to its character; so that, after all, the idea of animal spirits is in part retained, although the term, as applied to thenervousfluid, isexploded. Gooda directly admitsthem under the more modern title ; Mr. J. W. Earleb firmly believes in the existence of a circulation in the nervous system, — and it is not easy to conceive, that the brain does not possess the function of elaborating some fluid, — galvanoid or other, — which is the great agent in the nervous function. 2. The hypothesis of vibrations is ancient, but has been by no means as generally admitted as the last. Among the moderns, it has received the support of Condillac,0 Hartley,d Blumenbach,e and others ; some supposing, that the nervous matter itself is thrown into vibrations ; others, that an invisible and subtile ether is diffused through it, which acts the sole or chief part. As the latter is con- ceived, by many, to be the mode in which electricity is transmitted along conducting wires,it is not liable to the same objections as the former. Simple inspection, however,of a nerve at once exhibitsthat it is incapable of being thrown into vibrations. It is soft, never tense, always pressed upon in its course ; and, as it consists of filaments destined for very different functions, — sensation, voluntary, and in- voluntary motion, &c. — we cannot conceive how one of these fila- ments can be thrown into vibration without the effect being ex- tended laterally to others, and great confusion being thus induced. The very recent view of Dr. James Starkf in regard to the struc- ture of the tubes of the nerves, has led him to adopt a modification ofthe theory of vibrations. Believing that the matter which fills the tubes is of an oily nature,—and as oily substances are well known to be non-conductors of electricity, and farther, as the nerves have been shown by the experiments of Bischoff to be amongst the worst possible conductors of that agent,—he contends, that the ner- vous energy can be neither electricity nor galvanism, nor any pro- perty related to those powers; and conceives, that the phenomena are best explained on the hypothesis of undulations or vibrations propagated along the course of the tubes by the medium of the oily globules they contain. 3. The last hypothesis is of later date —subsequent to the dis- coveries made in animal electricity. The rapidity with which sensation and volition are communicated along the nerves could not fail to suggest a resemblance to the mode in which the electric a Study of Medicine, with Notes by S. Cooper, Doane's Amer. edit. vol. ii., in Proem to Class iv. Neurotica, New York, 1835. b New Exposition of the Functions ofthe Nerves, by James William Earle Part I London, 1833. c CEuvres, Paris, 1822. a Observations on Man, &c. chap. i. sect. 1 e Physiology, by Elliotson, § 226. f Proceedings of the Royal Society, No. 56, Lond. 1843. NERVOUS FLUID. 89 and galvanic fluids fly along conducting wires. Yet the great sup- port of the opinion was in the experiments instituted by Dr. Wilson Philip* and others, from which it appeared, that if the nerve pro- ceeding to a part be destroyed, and the secretion, which ordinarily takes place in the part, be thus arrested, the secretion may be re- stored by causing the galvanic fluid to pass from one divided ex- tremity of the nerve to the other. The experiments, connected with secretion, will be noticed more at length hereafter. It will likewise be shown, that in the effect of galvanism upon the mus- cles, there is the same analogy ; — that the muscles may be made to contract for a length of time after the death of the animal, even when a limb has been removed from the body, on the application of the galvanic stimulus; and comparative anatomy exhibits to us great development of nervous structure in those electrical ani- mals, which surprise us by the intensity of the electric shocks they are capable of communicating. Physiologists of the present day, generally, we think, accord with the electrical hypothesis. The late Dr. Young,bso celebrated for his knowledge in numerous departments of science, adopted it prior to the interesting experiments of Dr. Philip ; and Mr. Aber- nethy,c whilst he is strongly opposing the doctrines of materialism, goes so far as to consider some subtile fluid not merely as the agent of nervous transmission, but as forming the essence of life itself. By putting a ligature, however, around a nervous trunk, its functions, as a conductor of nervous influence, are paralysed, whilst it is still capable of conveying electricity; and Dr. Bostock,d has observed, that before the electrical hypothesis can be considered proved, two points must be demonstrated; first, that every func- tion of the nervous system may be performed by the substitution of electricity for the action of the nerves; and secondly, that all the nerves admit of this substitution. This is true, as concerns the belief in the identity of the nervous and electrical fluids ; but we have, even now, evidence sufficient to show their similarity, and that we are justified in considering the nervous fluid to be electroid or galvauoid in its nature, emanating from the brain by some ac- tion unknown to us, and distributed to the different parts ofthe sys- tem to supply the expenditure, which must be constantly going on. Riel,e Senac/ Prochaska, Scarpa,e and others are of opinion, that the nervous agency is generated through all the nervous system, and that every part derives sensation and motion from its own nerves. We have satisfactorily shown, however, that a communication with the brain is absolutely necessary in all cases, and that we can im- * Philosoph. Trans, for 1815, and Lond. Med. Gazette for March 18, p. 929, and March 25, 1837. •> Med. Literature, p. 93, Lond. 1813. c Physiological Lectures, exhibiting a view of Mr. Hunter's Physiology, &c. Lond. 1817. a An Elementary System of Physiology, 3d edit. p. 148, Lond. 1836. e De Structura Nervorum, Hal. 1796. f Traite de la Structure du Cceur, &c. Liv. iv. chap. 8, Paris, 1749. e Tabulffi Neurologic. Ticin. 1794, § 22. 8* 90 EXTERNAL SENSATIONS. mediately cut off sensation in the portion of a nerve included be- tween two ligatures, and as instantly restore it by removing the upper ligature and renewing the communication with the brain. a. External Sensations.. The external sensations are those perceptions that are occasioned by the impressions of bodies external to the part impressed. They are not confined to impressions made by objects external to us. The hand applied to any part of the body, any two of its parts brought into contact, the presence of its own secretions or excre- tions, may equally excite thern. AdeIona has divided them into two orders —first, the senses, properly so called, by the aid of which the mind acquires its notion of external bodies, and of their different qualities; and secondly,those sensations which are still caused by the contact of some body, and yet afford no information to the mind. It is by the agency of the organs of the external senses, that we become acquainted with the bodies that surround us. They are the instruments by which the brain receives its knowledge of the universe ; but they are only instruments, and cannot be considered as the sole regulators of the intellectual sphere of the individual. This we shall see is dependent upon another and still higher ner- vous organ, — the brain. The external senses are generally considered to be five in num- ber ; for, although others have been proposed, they may perhaps be reduced to some modification of these five, — tact or touch, taste, smell, hearing, and vision. All these have some properties in common. They are all situate at the surface of the body, so as to be capable of acting with due facility on external bodies. They all consist of two parts : —the one, physical, which modifies the action of the body, that causes the impression ; the other nervous or vital, which receives the impression, and conveys it to the brain. In the eye and the ear, we have better exemplifications of this dis- tinction than in the other senses. The physical portion ofthe eye is a true optical instrument, which modifies the light, before it impinges upon the retina. A similar modification is produced by the physical portion ofthe ear on the sonorous vibrations, before they reach the auditory nerve; whilst in the other senses, the physical portion forms part ofthe common integument in which the nervous portion is situate, and cannot therefore be easily distinguished. Some of them, again, are symmetrical; that is, composed of two separate and similar halves, united by a median line, — as the skin, tongue, and nose. Others, as the eye and the ear, are in pairs; and this, partly perhaps, to enable us to judge of the distances of ex- ternal objects. We shall find, at least, that there are certain cases, in which both the organs are necessary for accurate appreciation. Two of the senses — vision and audition —have, respectively, a nerve of special sensibility; and, until of late years, the smell has been believed to be similarly situate. In the present state of our 1 Physiologie de l'Hornme, torn. i. p. 259, 2de e'dit. Paris, 1829. EXTERNAL SENSATIONS. 91 knowledge, we cannot decide upon the precise nerve of taste, although it will be seen that a plausible opinion may be indulged on the subject. The general sense of touch is seated in the nerves of general sensibility. The others seem intimately connected with one of the nerves of general sensibility, — the fifth encephalic pair. This is especially the case with those senses that possess nerves of special sensibility, for, if the fifth pair be cut, the function is abolished, although the nerve of special sensibility may remain entire. Being instruments by which the mind becomes acquainted with external bodies, it is manifestly of importance, that the senses should be influenced by volition. Most of them are so. The touch has the pliable upper extremity, admirably adapted for the purpose. The tongue is moveable in almost every direction. The eye can be turned towards objects in almost all positions, by its own immediate muscles. The ear and the nose possess the least individual motion ; but the last four, being seated in the head, are capable of being assisted by the muscles adapted for its movements. All the senses may be exercised passively, and actively. By directing the attention, we can render the impression much more vivid ; and hence the difference between simply seeing or passive vision, and looking attentively; between hearing and listening; smelling and snuffing ; touching and feeling attentively. It is to this active exercise of the senses, that we are indebted for many of the pleasures and comforts of social existence. Yet, to preserve the senses in the vigour and delicacy, which they are capable of acquiring by attention, the impressions must not be too constantly or too strongly made. The occasional use of the sense of smell, under the guidance of volition, may be the test on which the che- mist, or the perfumer, or the wine-merchant, may rely in the dis- crimination of the numerous odorous characteristics of bodies; but, if the olfactory nerves be constantly or too frequently stimulated by excitants of this or any other kind, dependence can no longer be placed upon this means of discrimination. The maxim that " habit blunts feeling," is true only in such cases as the last. Edu- cation can indeed render it extremely acute.a Volition, on the other hand, enables us to deaden the force of sensations. By cor- rugating the eyebrows and approximating the eyelids, we can di- minish the quantity of light when too powerful. We can breathe through the mouth, when a disagreeable odour is exhaled around us; or we can completely shut off the passage by the nostrils, with the aid of the upper extremity. Over the hearing we have less command, as regards its individual action : the upper extremity is here always called into service, when we desire to diminish the intensity of any sonorous impression. Lastly. It is a common observation, that the loss of one sense occasions greater vividness in others. 'This is only true as regards the senses which administer chiefly to the intellect,— those of touch, * Berard, Rapport du Physique et du Moral, p. 245 ; Paris, 1823. 92 SENSE OF TOUCH. audition, and vision, for example. Those of smell and taste may be destroyed, and yet the more intellectual senses may be unin- fluenced in their action. The cause of the superiority of the remaining intellectual senses, when one or more has been lost, is not owing to any superior or- ganization in these senses, but is another example ofthe influence of education. The remaining senses are exerted attentively to com- pensate for the privation, and they become surprisingly delicate. We proceed to the consideration ofthe separate senses, beginning with that of tact or touch, because it is the most generally distri- buted, and may be regarded as that from which all the others are derived. They are all, indeed, modifications ofthe sense of touch. In the taste, the sapid body ; in the smell, the odorous particle ; in the hearing, the sonorous vibration ; and in the sight, the particle of light, must impinge upon or touch the nervous part of the organ, before sensation can, in any ofthe cases, be effected. SENSE OF TACT OR TOUCH--PALPATION. The sense of tact or touch is the general feeling or sensibility, possessed by the skin especially, and which instructs us regarding the temperature and the general qualities of bodies. By some, touch is confined to the sense of resistance alone ; and hence they have conceived it necessary to raise into a distinct sense one ofthe attri- butes of tact or touch. The sense of heat, for example, has been separated from tact j but although the appreciation of external bodies by tact or touch differs — as will be seen—in some respects from our appreciation of their temperature, it properly belongs to the sense we are considering, in the acceptation here given to it, and adopted by all the French physiologists. Accord- ing to them, tact is spread generally in the organs, and especially in the cutaneous and mucous surfaces. It exists in all animals; whilst touch is exercised only by parts evidently destined for that purpose. Touch does not exist in every animal. It is nothing more than tact joined to muscular contraction and directed by volition. So that, in the exercise of tact, we may be esteemed passive; in that of touch, active. The organs concerned in touch, execute other functions besides ; and in this respect touch differs from the other senses. Its chief organ, however, is the skin ; and hence it is necessary to inquire into its structure, so far as is requisite for our purpose. 1. ANATOMY OF THE SKIN, HAIR, NAILS, ETC. The upper classes of animals agree in possessing an outer enve- lope or skin, through which the insensible perspiration passes, a slight degree of absorption takes place, the parts beneath are pro- tected, and the sense of touch is accomplished. In man, the skin consists of four parts, — the cuticle, rete mucosum, corpus papillare, and corium. ORGANS OF TOUCH. 93 1. The epidermis or cuticle is the outermost layer. It is a dry, membranous structure, devoid of vessels and nerves, yet it is de- scribed by recent investigators as a tissue of a somewhat complex organization, connected with the functions of exhalation and ab- sorption ; but its vitality is regarded by them to be on a par with that of vegetables. The absence of nerves proper to it renders it insensible ; it is coloured, exhales and absorbs in the mannerofvege- tables. It is, so far as we know, entirely insensible. It resists pu- trefaction for a long time, and may be easily obtained in a separate state from the other layers, by maceration in water. It is the thin pellicle raised by a blister. The cuticle is probably a secretion from the true skin, which con- cretes on the surface, becomes dried, and affords an efficient pro- tection to the corpus papillare beneath. It is composed, according to some, of concrete albumen; according to others, of mucus ; and is said to be pierced by oblique pores for the passage of hairs, and for the orifices of exhalent and absorbent vessels. Breschet and Roussel de Vauzemea affirm, that there is a special " blennogenous or mucific apparatus^ for the secretion of this mucous matter, composed of a glandular parenchyma or organ of secretion situate in the substance ofthe derma, and of excretory ducts, which issue from the organ, and deposit the mucous matter between the pa- pills. It is probable, that this substance is placed at the surface of the body, not simply to protect the corpus papillare, but to prevent the constant imbibition and transudation that might take place did no such envelope exist. The cuticle exfoliates, in the form of scales, from our heads; and, in large pieces, from every part of the body, after certain cutaneous diseases. According to Raspail,b it is formed of a collection of vesicles deprived of their contents, closely applied together, dried, and thrown off in the form of branny scales. He regards it as the outer layer ofthe corium. M. Flou- rens6 considers the derma to be covered by two layers of epider- mis; the innermost of which is the seat of colour in the European. The colour ofthe areola around the mamma is owing to the same ; whilst in the black or coloured races, there is, beneath the two membranes, an organ for the secretion of the colouring matter. Modern histologists consider the epidermis to be composed of a series of flattened, scale-like cells, which, when first formed, are of a spheroidal shape ; but gradually dry up. These form various layers. The epidermoid tissues have the simplest structure of any solids.0 Recent analysis has shown, that the chemical constitu- tion of the membranous epidermis of the sole of the foot, and that of the compact horny matter of which nails, hair, wool and hair, are composed, is the same. 2. The corpus or rete mucosum, rete Malpighii or mucous web, a Nouvelles Recherches sur la Structure de la Peau, par M. Breschet, Paris, 1835. b Chimie Organique, p. 245, Paris, 1833. <: Gazette M£dicale de Paris, Mars, 1838. a Henle, Allgemeine Anatomie, u. s. w., and Mr. Paget, Brit, and For. Med. Rev. July, 1842, p. 263. 94 SENSE OF TOUCH. is the next layer. It was considered by Malpighi to be mucus, secreted by the papillae, and spread on the surface of the corpus papillare, to preserve it in the state of suppleness necessary for the performance of its functions. In this rete mucosum, the colouring matter of the dark races seems to exist. It is black in the African, or rather in the Ethiopian; and copper-coloured in the mulatto." Gaultierb considers it to be composed of four layers, but this notion is not universally admitted, and scarcely concerns the present in- quiry. Breschet affirms, that there is a particular " chromatoge- nous or colorific apparatus;' for producing the colouring matter, composed of a glandular or secreting parenchyma, situate a little below the papillas, and presenting particularexcreting canals, which pour out the colouring matter on the surface of the derma. Modern observers deny, that there is any such distinct layer. By them, the. colour is referred to pigment cells, which are scat- tered through the ordinary epidermic cells; and the colour of the skin is determined by that of their contents.6 The rete mucosum is considered to be the last formed portion of the cuticle. 3. The corpus papillare, or what Breschet calls the " neurothelic or mammillary nervous apparatus? is seated next below the rete mucosum. It consists of a collection of small papillas, formed by the extremities of nerves and vessels, which, after having passed through the corium beneath, are grouped in small pencils or villi on a spongy, erectile tissue. These pencils are disposed in pairs, and, when not in action, are relaxed, but become erect when employed in the sense of touch. They are very readily seen, when the cutis vera is exposed by the action of a blister, and are always evident at the palmar surface of the hand, and especially at the tips of the fingers, where they have a concentric arrangement. These villi are sometimes called papilla? of the skin. 4. The corium, cutis vera, derma, or true skin, is the innermost of the layers of the skin. It consists of a collection of dense fibres, intersecting each other in various directions, and leaving between them holes for the passage of vessels and nerves. It forms a firm stratum, giving the whole skin the necessary solidity for accom- plishing its various ends; and consists chiefly of gelatin; hence it is used in the manufacture of glue. Gelatin, when united with tannin, forms a substance which is insoluble in water ; and it is to this combination that leather owes the properties it possesses. The hide is first macerated in lime-water to remove the cuticle and hairs, and leave the corium or gelatin. This is then placed in an infusion of oak bark, which contains tannin. The tannin and the skin unite, and leather is the product. These four strata constitute the skin, as it is commonly called; yet all are comprised in the thickness of two or three lines. The cutis vera is united to the structures below by cellular mem- a Sir E. Home, Lect. on Camp. Anat. v. 278. *> Recherches Anatomiques sur le Systeme Cutane de l'Homme, Paris, 1811. c Carpenter, Human Physiology, § 616, Lond. 1842. ORGANS OF TOUCH. 95 Fig. 10. brane; and this, with the layers external to it, forms the common integument. In certain parts of the body, and in animals more particularly, the cutis vera is ad- herent to muscular fibres; insert- ed more or less obliquely. These form the muscular web, mantle or panniculus carnosus. The layer is well seen in the hedge- hog and porcupine, in which it rolls up the body, and erects the spines; and in birds, it raises the feathers. In man, it can hardly be said to exist. Some muscles, however, execute a similar func- tion. By the occipito-frontalis, for instance, many persons can move the hairy scalp: and by the dartos, the skin of the scrotum can be corrugated. These two parts, therefore, act as panniculi carnosi. In the skin are situate numer- ous sebaceous follicles or crypts, which separate an oily fluid from the blood, and pour it OVer the scope. ~6. A perspiratory gland with its spiral r 1 i_ • .. jir j •.. duct, such as is seen in the palm of the hand or SUrtace tO lubricate and detend It sole of the foot. 7. Another perspiratorygland frnm thp nptinn nf mnktnrp with a straighter duct, such as is seen in the irom me action 01 moisuue. gcaIp a Two hairs from tne sca,P) enclosed in They are mOSt abundant, Where their follicles; their relative depth in the skin .1 r 1 1 /-i 1 • 1 • is preserved. 9. A pair of sebaceous glands, tliere are IOldS Ot the Skin, Or hairs, opening by short ducts into the follicle of the or where the surface is exposed hair■-^mu Precis de Physiol, i. 139. 112 SENSE OF TASTE. Fig. 13. tion, deglutition, and articulation. These muscles being under the influence of volition, enable the sense to be executed passively or actively. As regards gustation, the mucous membrane is the portion that is immediately concerned. This is formed, like the mucous mem- branes in general, ofthe different layers already described. The cor- pus papillare, however, requires additional notice. If the surface ofthe tongue be examined, it will be found to consist of myriads of fine papillae or villi, giving the organ a velvety appearance. These papillae are, doubtless, formed, like those of the skin, of the final ramifications of nerves, and of the radicles of exhalent and absorbent ves- sels, united by means of a spongy erectile tissue. Great confusion exists among ana- tomists in their descriptions of the papillae of the tongue. Those concerned in the sense of taste may, however, all be included in two divisions: — 1st, the conical ox pyramidal, — the finest sort being by some called filiform; and 2dly, the fungiform. The former are broader at the base than at the top, and are seen over the whole surface of the tongue, from the tip to the root. The latter, which are larger at the top than at the base, and resemble the mushroom, — whence their name, — are spread about, here and there, upon the surface ofthe organ. These papilla? of taste must be distinguished from a third set, the papillae. capitatas, which are mucous follicles, and of course accomplish a very different function. All the nerves that pass to the parts whose office it is to appre- ciate savours must be considered to belong to the gustatory appa- ratus. These are the inferior maxillary, several branches of the superior, filaments from the spheno-palatine and naso-palatine ganglions, the lingual branch of the fifth pair, the whole of the ninth pair or hypoglossal, and the glosso-pharyngeal. To which of these must be assigned the function of gustation we shall inquire presently. Like the skin and mucous membranes in general, that of the tongue and mouth contains, in its substance, numerous mucous follicles, which secrete a fluid that lubricates the organ, and keeps it in a condition best adapted for the accomplishment of its func- Papilla of the Tongue. . Foramen of Morgagni. b. Fungiform papillae. Conical papilla, d. Papillaecapitata?. SAVOURS. 113 tions. Some of these are placed very conspicuously in the mucous membrane of the tongue. They are the papillae capitatse of many anatomists, — erroneously named, as they are not formed like the papillas, and, as we have said, execute a very different office. They are mucous follicles, and ought to be so called. They are situate near the base ofthe tongue, and the last percep- tible rows unite anteriorly at an angle close to the foramen caecum of Morgagni. The fluids, exhaled from the mucous membrane of the mouth, and the secretion of the different salivary glands likewise aid in gustation; but they are more concerned in mas- tication and in salivation, and will require notice under another head. 2. OP SAVOURS. Before proceeding to explain the physiology of gustation, it will be necessary to inquire briefly into the nature of bodies, connected with their sapidity, or, in other words, into savours, which are the cause of sapidity. The ancients were of opinion, that the cause of sapidity is a peculiar principle, which, according to its combination with the constituents of bodies, gives rise to the various savours that are found to exist. This notion has been long abandoned ; and chiefly, because we observe no general or common characters amongst sapid bodies, which ought to be expected if they were pervaded by the same principle; and because it is found that bodies may be deprived of their sapidity by subjecting them to appropriate agents. Many of our culinary processes have been instituted for this purpose : the infusion of tea is indebted for all its attractions to the power we possess of separating, by boiling water, its savoury from its insipid portions. A savour must, therefore, be esteemed an integrant molecule of a body; not identical in all cases, but as heterogeneous in its nature as the impressions that are made upon the organ of taste. When the notion was once entertained, that savour is an inte- grant molecule, sapidity was attempted to be explained by the shape of the molecule. It was said, for instance, that if the savour be sweet, the molecule must be round; if sharp, angular ; and so forth. Sugar was said to possess a spherical, —acids, a pointed, or angular molecule. We know, however, that substances, which resemble each other in the primitive shape of their crystal, impress the organ of taste very differently; and that solution, which must destroy most — if not all — of the influence from shape, induces no change in the savour. Others have referred sapidity to a kind of chemical action be- tween the molecules and the nervous fluid. This view has been suggested by the fact, that, as a general principle, sapid bodies, like chemical agents, act only when in a state of solution ; that the same savours usually belong to bodies possessed of similar chemi- cal properties as is exemplified by the sulphates and nitrates ; and that, in the action of acids on the tongue and mouth, we witness 114 SENSE OF TASTE. a state of whiteness and constriction, indicative of a first degree of combination. All these'circumstances, however, admit of another explanation. There are unquestionably many substances, which do combine chemically,— not with a nervous fluid, of whose exist- ence we know nothing, — but with the mucus of the mouth, and the sapidity resulting from such combination is appreciated by the nerves of taste ; but there are many bodies, which are eminently sapid, and yet afford us instances of very feeble powers of chemi- cal combination ; nay, in numerous cases, we have not the least evidence that such powers are existent. Vegetable infusions or solutions afford us strong examples of this kind, — of which syrup may be taken as the most familiar. The effect of solution is easily intelligible ; the particles of the sapid body are in this way sepa- rated and come successively into contact with the gustatory organ; but there is some reason to believe, that solution is not always requisite to give sapidity. Metals have generally a peculiar taste, which has been denominated vietallic ; and this, even if the sur- face be carefully rubbed, so as to free it from oxide, which is more or less soluble. Birds, too, whose organs of taste are as dry as the corn they select from a mass of equally arid substances, are probably able to appreciate savours. The taste produced by touching the wires of a galvanic pile with the tongue has been offered as another instance of sapidity exhibited by dry bodies. This is, more probably, the effect of that chemical action on the fluids covering the mucous membrane of the tongue, which always follows such contact. Such chemical change must, however, be confined to these fluids, and when once produced, the nerve of taste is compelled to appreciate the savour developed in the same manner as it does in cases of morbid alterations of the secretion of the mucous membrane, when, it is well known, a body pos- sessing considerable and peculiar sapidity may fail to impress the nerves altogether, or may do so inaccurately. The notion of any chemical combination with the nervous fluid must of course be discarded. There is not the slightest shadow of evidence in favour of the hypothesis: yet the epithet chemical was once ap- plied to this sense on the strength of it, in opposition to the senses of touch, vision, and audition, which were called mechanical, and supposed to be produced by vibration of their nerves. The savours, met with in the three kingdoms of nature, are in- numerable. Each body has its own, by which it is distinguished : but few instances occur in which any two can be said to be iden- tical. This is the great source of difficulty, when we attempt to throw them into classes, as has been done by many physiologists. Of these classifications, the one by Linnaeus3 is the best known : it will elucidate the unsatisfactory character ofthe whole. He divides sapid bodies into sicca, aquosa, viscosa, salsa, acida, slyptica, dulcia,pinguia, amara, acria, and nauseosa. He gives also exam- ples of mixed savours — the acido-acria, acido-amara, amaro- a Amcenit. Academ. ii. 335. SAVOURS. 115 acria, amaro-acerba, amaro-dulcia, dulci-styptica, dulci-acida, dulci-acria, and acri-viscida ; and he remarks, that the majority are antitheses to each other, two and two, as the dulcia and acria ; the pinguia and styptica ; the viscosa and salsa ; and the aquosa and sicca. Boerhaavea again divides them into primary and com- pound; the former including the sour, sweet, bitter, saline, acrid, alkaline, vinous, spirituous, aromatic, and acerb ; — the latter re- sulting from the union of some of the primary savours. There is, however, no accordance amongst physiologists regarding those that should be esteemed primary, and those that are secondary and compound ; although the division appears to be fairly admissible. The acerb, for example —which is considered primary by Boerhaave — is by others, with more propriety, classed among the secondary or compound, and believed to consist of a combination of the acrid and acid. Still we understand sufficiently well the character of the acid, acrid, bitter, acerb, sweet, &c.; but when, in common lan- guage, we have to depict other savours, we are frequently compelled to take some well known substance as the standard of comparison. According to Adelon,b the only distinction, which we can make amongst them, is, — into the agreeable and the disagreeable. Yet of the unsatisfactory nature of this classification he himself adduces numerous and obvious proofs. It can only, of course, be applicable to one animal species, often even to an individual only ; and often again only to this individual, when in a given condition. Animals are known to feed upon substances, which are not only disagree- able but noxious to other species. The most poisonous plants in our soil have an insect which devours them greedily and with im- punity : the southern planter is well aware, that this is the case with his tobacco, unless the operation of ivorming be performed in due season. The old adage, that " one man's meat is another man's poi- son," is metaphorically accurate. Each individual has, by organiza- tion or association, dislikes to particular articles of food, or shades of difference in his appreciation of tastes, which may be regarded pecu- liar ; and in certain cases these peculiarities are signal and surprising. Of the strange differences, in this respect, that occur in the same individual under different circumstances, we have a common and forcible instance in the pregnant female, who often has the most ardent desire for substances, which were previously perhaps repug- nant to her, or at all events not relished. The sense, too, in cer- tain diseases — especially of a sexual character, or which are con- nected with the state of the sexual functions — becomes remark- ably depraved, so that substances, which can in no way be ranked as eatables, are greedily sought after. A young lady was under the care of the author, whose greatest bonne bouche was slate pencils. At other times, we find chalk, brick-dust, ashes, dirt, &c, obtaining the preference. Habit, too, has considerable effect in our decisions regarding the agreeable. The Roman liquamen or 1 Pralect. Academ. torn. iv. b Physiologie de 1'Homme, seconde edit, i. 301, Paris, 1829. 116 PHYSIOLOGY OF TASTE. garum, the most celebrated sauce of antiquity, was prepared from the half putrid intestines of fish; and one of the varieties of the Owoc 2<* Op. Anat. de Aure Humana, &c. Ed. J. A. Morgagni, Venet. 1740. = Oper. Omn. Venet. 1720. d Enchirid. Anat. 1. iv. c. 4, Lugd. Bat. 1649 » Op. citat. i. 269. PHYSIOLOGY OF THE MUDDLE EAR. 157 thinks, opposes this doctrine. The function which, with Savart, he assigns to it — if not accurately, at least ingeniously —is the fol- lowing. As the membrane of the foramen ovale receives the vi- brations from the chain of small bones, these vibrations circulate through the intricate windings of the labyrinth, and are again trans- mitted to the air in the tympanum by the foramen rotundum. The different cavities of the labyrinth being filled with an incompres- sible fluid, no such circulation, he insists, would occur, provided the parts were entirely osseous. As it is, the membrane of the foramen rotundum gives way, " and this leads the course of the undulations ofthe fluid in the labyrinth in a certain unchangeable direction." The explanation of Sir C. Bell is not as convincing to us as it seems to be to himself. The membrane of the foramen rotundum does not appear to be required for the undulation in the cavities of the labyrinth, which he describes, as the liquor of Cotun- nius can readily reflo w into the aqueducts ofthe vestibule and cochlea. The principal use of these canals would seem, indeed, to be, to form diverticula for the liquor, when it receives the aerial impulses. Sir C. Bell cites the case, often quoted from Riolan, of an indivi- dual, who was deaf from birth, and who was restored to hearing by accidentally rupturing the membrana tympani, and breaking the ossicles with an ear-pick — " disrupit tympanum, fregitque ossi- cula, et audivit." In these and other cases, in which the mem- brana tympani and ossicles have been destroyed, and the hearing has still persisted, the vibrations must have been conveyed to the parietes of the internal ear through the air in the cavity of the tympanum, and, notwithstanding the charge of " absolute confu- sion of ideas," adduced against such individuals as Scarpa,3 Magendie, Adelon, and others, who believe that the foramen rotundum receives the undulations of the air, we must confess, that the idea of the communication of vibrations through that medium, as well as through the membrane of the foramen ovale, and the osseous parietes of the labyrinth, appears to us most solid and satisfactory. The ossicles or small bones have given occasion to the wildest speculations. At the present day, they are considered to fulfil one of two functions; — either to conduct the vibrations from the membrana tympani, or to stretch the membranes to which the ex- tremities of the chain are attached. Both these offices are proba- bly executed by them, the malleus receiving the vibrations from the membrana tympani, and conveying them to the incus, — the incus to the os orbiculare,— the os orbiculare to the stapes, and the stapes to the membrane of the foramen ovale, by which they are transmitted to the liquor of Cotunnius. Savart conceives, that the chain of ossicles is to the ear what the bridge is to the violin. It has been already observed, that the ossicles are not essential to hearing, although they may be required to perfect it; and that 1 Anat. Disquis. de Auditu et Olfactu., Ticin, 1789; and de Structure Fenestra Rotundae Auris, &c. Mutin. 1772. VOL. I. -- 14 158 SENSE OF HEARING. they may be destroyed, without deafness being produced, provided the membrane of the foramen ovale remains entire, and the parts within the labyrinth retain their integrity. If, in the removal of the stapes by ulceration or otherwise, the membrane of the fora- men were to be ruptured, the liquor of Cotunnius would of course escape, and partial or total deafness be the result. In some expe- riments, instituted by Flourens on pigeons, he found that the re- moval of the malleus and incus did not have much effect upon the hearing; but when the stapes was taken away it was greatly diminished, and still more so when the membranes ofthe fenestra ovalis and fenestra rotunda were destroyed. The Eustachian tube is an important part of the auditory appa- ratus, and an invariable accompaniment ofthe membrana tympani, in animals. Without the tube, the membrane would be almost devoid of function. Pathology shows us, in the clearest manner, that its integrity is necessary to audition ; and that deafness is the consequence of its closure. Dr. Bostocka thinks, " it is perhaps not very easy to ascertain in what mode it acts, but it may be con- cluded that the proper vibration of the membrana tympani is, in some way, connected with the state of the air in the tube." The name of the cavity to which the tube forms a communication with the external air suggests — the author conceives — an easy and sufficient explanation of its use. The drum of the ear, like every drum, requires an aperture in some part of its parietes, in order that its membranes may vibrate freely. The Eustachian tube serves this purpose, and its closure produces the same effect upon the membrana tympani at one end of the cylinder, and on the membrane of the foramen ovale at the other, as would be pro- duced on the parchments of the ordinary drum by the closure of its lateral aperture. We can, in this way, account for the tempo- rary deafness, which accompanies severe cases of inflammation of the throat: the swelling obstructs the Eustachian tube. Dr. Car- penter,1' however, thinks that the effect ofthe hole in the side of a drum seems rather to be the communication to the ear of the observer ofthe sonorous vibrations ofthe contained air, which are thus transmitted directly through the atmosphere, instead of being weakened by transmission through the walls of the instrument; and hence he concludes, that there is no real analogy between the two cases. During the constant efforts of deglutition the air is renewed in the cavity of the tympanum ; and, as the extremities of the Eusta- chian tube terminate in the pharynx, it always enters at a modi- fied temperature; and the writer last cited thinks the principal object of the tube seems to be the maintenance of the equilibrium between the air within the tympanum and that without, so as to prevent inordinate tension ofthe membrane, which would be pro- duced by too great or too little pressure on either side, the effect of which would be impaired hearing. » Physiology, 3d edit, p. 721, Lond. 1836. b Human Physiology, § 357, Lond. 1842. PHYSIOLOGY OF THE INTERNAL EAR. 159 By closing the nose and mouth,, and forcing air from the lungs, we can feel a sensation of fulness in the ear, produced by the pres- sure of the air against the internal surface of the membrana tym- pani ; and they, who have the membrane perforated, can send lobacco smoke copiously out ofthe external ear. Besides this necessary function, the Eustachian tube has been supposed to possess another, — that of serving as a second meatus auditorius, by permitting sonorous vibrations to enter through the pharyngeal extremity, and, in this way, to attain the internal ear. A simple experiment, first described by Perolle,3 exhibits the fal- lacy of this notion. If we carry a watch far back into the mouth, taking care not to touch the teeth, little or no sound will be heard, but if we draw the watch forward, so as to touch the teeth, the ticking becomes distinctly audible. If the pharyngeal extremity acted as a second meatus, the sound ought to be heard better when the watch is placed nearer to it,; but this is not the case. On the contrary, it is not until the sonorous body is put in contact with the teeth, that the sound is appreciated. This is effected by the vibrations of the watch being conveyed along the bony parietes until they reach the auditory nerve. Again ; if the meatus audito- rius externus be completely closed, we cannot hear the voice of one who speaks into the mouth ; and can hear but imperfectly our own. The fact of our gaping, when desirous of hearing accu- rately, has partly led to the belief, that the Eustachian tube acts as a second meatus. It has been properly remarked, however, that this may be merely an act of expression; and, also, that the meatus auditorius is rendered more open, when we depress the lower jaw, than when it is raised, as can be readily perceived by inserting the little finger into the meatus, when the jaw is in either situation. In addition to these functions, it is probable, that the Eustachian tube acts as a diverticulum for the air in the cavity of the tympa- num, when it is agitated by too powerful sounds. The closure of the Eustachian tube is the cause of that form of deafness, which is relieved by the injection of air or other fluids into the tube— a fact, the knowledge of which has been the foundation of much empiricism. It likewise conveys into the pharynx the mucus that is secreted by the lining membrane of the tympanum, probably by means of cilia vibrating on its mucous surface. Internal Ear. — In the various ways mentioned, the vibrations of a sonorous body reach the internal ear. The membranes ofthe foramen ovale and foramen rotundum resemble the membrana tympani in their physical characteristics ; and when thrown into vibrations communicate the impression to the liquor of Cotunnius, which fills the cavities of the internal ear. By this medium, the vibrations are conducted to the auditory nerve, which conveys the impression to the brain. The views entertained regarding the sympathetic vibrations of * Hist, et Mdm. de la Socie'te Royale de Medecine, torn. iii. 160 SENSE OF HEARING. the membrana tympani have almost all been applied to the mem- brane ofthe foramen ovale : our knowledge, however, is restricted to the fact, that its tension can be varied by the chain of bones, without our being able to specify the circumstances under which this takes place. Adelon asserts, that the membrane may be torn, and yet the sense of hearing may not be destroyed. This seems scarcely possible, as the liquor of Cotunnius must necessarily escape, and so much morbid action be induced as to render audi- tion apparently impracticable. The membrane of the foramen rotundum, which forms the me- dium of communication between the cavity of the tympanum and the cochlea, has, of course, no chain of bones to modify its tension. Both the vibrations into which it is thrown, and those of the ves- tibular membrane, are imparted, as we have seen, to the liquor of Cotunnius, which is present in every ear, and appears essential to audition. Of the precise uses of the vestibule, semicircular canals, and cochlea, we have very limited notions. The beauty and complexity of their arrangement has, however, given rise to various conjec- tures. Le Cata considered the lamina spiralis to consist of numerous minute cords, stretched along it, and capable of responding to every tone. Magendieb affirms, that no one at the present day admits the hypothesis regarding the use of this osseo-membranous septum ; but he is in error. Sir C. Bellc asserts, that the cochlea is the most important part of the organ of hearing ; or rather, that it is " the refined and higher part of the apparatus;" and he considers the lamina spiralis as the only part adapted to the curious and admira- ble powers of the human ear for the enjoyment of melody and karmony. The subject of the musical ear will engage us presently. It may be sufficient to remark, in this place, that there is no ratio in animals, between the delicacy of the hearing, and the degree of complication of the cochlea. The cochlea of the Guinea pig is more convoluted than that of man, yet we can hardly conceive it to have a better appreciation of musical tones; whilst in birds, whose hearing is unquestionably delicate, the organ is, as we have remarked, extremely simple, and has no spiral arrangement. Again; the semicircular canals have been compared to organ pipes, adapted for producing numerous tones; and Dr. Youngd sup- posed them to be " very capable of assisting in the estimation ofthe acuteness or pitch of a sound, by receiving its impression at their opposite ends; and occasioning a recurrence of similar effects at different points of their length according to the different character of the sound ; while the greater or less pressure of the stapes must serve to moderate the tension ofthe fluid within the vestibule, which serves to convey the impression." " The cochlea," he adds, " seems to be pretty evidentlya micrometer of sound." Another view__as remarked hereafter —is, that the peculiar function is the reception of a Traite des Sens, Paris, 1767, or English translation, Lond. 1750. b Precis. &c. i. 121. <= Op. citat. ii. 273. a Med. Literature, p. 98, Lond. 1813. PHYSIOLOGY OF THE INTERNAL EAR. 161 the impressions by which we distinguish the direction of sounds. All these are mere hypotheses; ingenious, it is true, but still hypo- theses ; and, in candour, we must admit, that we have no positive knowledge ofthe precise functions of either vestibule, cochlea, or semicircular canals. Our acquaintance with them is limited to this; that they contain the final expansions of the auditory nerve; and that it is within them, that this nerve receives its impressions from the oscillations of sonorous bodies. It has been observed, that these vibrations may reach the nerve by the bony parietes, and that the ticking of a watch held between the teeth, is, in this way, heard. A blow upon the head is distinctly audible ; and Ingrassiasa relates the case of a person, who had be- come deaf in consequence of obstruction of the meatus auditorius externus, and yet could hear the sound of a gnitar by placing the handle between his teeth, or by making a communication between his teeth and the instrument by a metallic or other rod. The physi- cian has recourse to a plan of this kind for detecting whether a case of deafness be dependent upon obstructed Eustachian tube; upon some affection of the meatus auditorius externus ; or upon insen- sibility of the auditory nerve, or of the part ofthe brain that effects the sensation. If the latter be the case, the ticking of a watch, applied to the teeth, will not be audible, and the case will necessarily be one of a hopeless character. If, on the other hand, the sound be perceived, the attention of the physician may be directed, with well founded expectation of success, to the physical parts of the organ, or to those concerned in the transmission of vibrations. Frequently, it will happen, in such cases, that the Eustachian tube is impervious, and properly directed efforts may succeed in removing the obstruc- tion ; or if this be impracticable, temporary, if not permanent, re-" lief may be obtained by puncturing the membrana tympani, and allowing the aerial undulations,in this way, to reach the middle and internal ear. Lastly ; — as regards the precise nerve of hearing. In this sense we have the distinction between the nerve of general, and that of spe- cial sensibility, more clearly observed. The experiments of Ma- gendie15 have shown, that the portio mollis of the seventh pair is the nerve of special sensibility ; —that it may be cut, pricked, or torn, without exhibiting any general sensibility, and that it is inservient only to the sense of hearing. The same experiments demonstrate that this nerve cannot act, unless the fifth pair or nerve of general sensibility be in a state of integrity. If the latter nerve be divided within the cranium, the hearing is always enfeebled, and frequently destroyed. The experiments of Flourens,0 to which allusion has been made, led him to infer that the rupture of the cochlea was of a De Ossibus, p. 7. See, also, Boerhaave, Praelectiones, iv. 415, and Haller, Element. Physiol, torn. v. p. 253, Lausann, 1763. b Precis, &c. 2de edit. i. 114. c Experiences sur le Systeme Nerveux, p. 42, Paris, 1825, or 2de edit., Paris, 1842 14* 162 SENSE OF HEARING. less consequence than that of the semicircular canals. Laceration of the nerve, distributed to the vestibule, enfeebled the hearing, and its total destruction was followed by irreparable deafness. For these, and other reasons furnished by comparative anatomy, Le- pelletiera infers, that, in the higher organisms, the vestibule and its nerve constitute the essential organ of impression, the other parts being superadded to perfect the apparatus. An interesting case of malformation has been related by Pro- fessor Mussey,b of Cincinnati, which shows, that other nerves, besides the portio mollis of the seventh pair, may, under unusual circumstances, be inservient to audition. In this case there was no appearance whatever of meatus auditorius externus in either ear, and yet the man, twenty-seven years of age, although his sense of hearing was too obtuse for low conversation, could hear suffi- ciently well to prosecute his business — that of a bookseller — without material inconvenience. By covering the head with layers of cloth, it was found that the hearing was manifestly ob- scured. On speaking to him with one end of a stick in the listener's mouth, whilst the other end was applied in succession to different parts of the head and face, it was found, that the part over the mastoid process conducted sound most readily; and that the parts corresponding with the upper two-thirds of the occipital, the mastoid plate of the temporal, and the posterior half of the parietal bone, transmitted sounds more readily than the anterior half of the scalp, the forehead, temples, or any other part of the face. Professor Mussey infers, from the results of his observations on this case, that the nerves, derived from the spinal cord below the foramen magnum of the occipital bone, and reflected in pro- fusion over the scalp, were concerned in this unusual function, and that the branches of the fifth pair were probably the seat of the peculiar faculty on the face.c A case was communicated to the author by the Rev. Dr. Parker, in which, also, there was no evidence of external ear. The hearing was very indistinct. Under the idea, that the internal organs were perfect, and that, to render the hearing so, it was only necessary to perforate the integument so as to admit the air to the tympa- num, Dr. Parker, at the request of the youth, and of his parents, determined to perforate one ear. In accordance with Chinese prejudice in favour ofthe cautery,the caustic potassa was applied, and " as soon as the slough from the first applications was re- moved, the hearing was surprisingly improved." No cavity, how- ever, could be discovered. After different operations, he was able to hear a whisper.*1 * Traite" de Physiologie Medicale et Philosophique, iii. 143 Paris 1832. b American Journal ofthe Medical Sciences, Feb. 1838, p. 378. = See a similar case by Mr. Swan, in Medico-Chirurgica'l Transactions vol. xi. i First Report of the Ophthalmic Hospital, Canton, Feb. 1826. IMMEDIATE FUNCTION OF HEARING. 163 The immediate function of the sense of hearing is to appreciate sound ; and we may apply to it what has been said of the other senses, that, in this respect, it cannot be supplied by any other — that it is instinctive, requires no education, and is exerted as soon as the parts have attained the necessary degree of development. Amongst the advantages afforded by the possession of this sense, which has been properly termed intellectual, are two of the highest gratifications we enjoy — the appreciation of music, and the pleasures of conversation. It is to it that we are indi- rectly indebted for the use of verbal language — the happiest of all inventions — as it has been properly termed, and to which we shall have to advert in the course of our inquiry into the animal functions. Metaphysicians and physiologists have differed considerably in their views regarding the organs more immediately concerned in the appreciations in question. Many, for example, have referred the faculty of music to the ear ; and hence, in common language, we speak of an individual, who has a " musical ear," or the con- trary. Others, more philosophically we think, have considered, that the faculty is seated in the encephalon ; that the ear is merely the instrument for conveying the sonorous undulations, which, in due order, constitute melody, but that the appreciation is ultimately effected in the brain. " That it," (the power of distinguishing the musical relations of sounds,) says, Dr. Brown,a " depends chiefly, or perhaps entirely, on the structure or state of the mere corporeal organ of hearing, which is of a kind, it must be remembered, peculiarly complicated, and therefore susceptible of great original diversity in the parts, and relations of the parts that form it, is very probable; though the difference of the separate parts them- selves, or of their relations to each other, may, to the mere eye, be so minute, as never to be discovered by dissection." Many physiologists of eminence have regarded the complex internal ear as the seat of the faculty ; some looking to the cochlea; others to the semicircular canals; but few referring it to the brain. Sir C. Bell, indeed, asserts, that " we are not perhaps warranted in concluding, that any one part of the organ of hearing bestows the pleasures of melody and harmony, since the musical ear, though so termed, is rather a faculty depending on the mind." Yet afterwards he adds : — " we think that we find in the lamina spiralis (of the cochlea) the only part adapted to the curious and admirable powers of the human ear for the enjoyment of melody and harmony. It is in vain to say, that these capacities are in the mind and not in the outward organ. It is true, the capacity for enjoyment or genius for music is in the mind. All we contend for is, that those curious varieties of sound, which constitute the source of this enjoyment, are communicated through the ear, and that the ear has mechanical provisions for every change of * Lectures on the Philosophy of*he Human Mind, Edinb. 1820 ; and Amer. Edit., vol.i. p. 207, Boston, 1826. 164 SENSE OF HEARING. sensation."3 A cherished opinion of Sir Everard Homeb on this subject has been referred to. Conceiving the membrane of the « tympanum to be muscular, he considers the membrana tympani, with its tensor and radiated muscles, to resemble a monochord, " of which the membrana tympani is the string ; the tensor mus- cles the screw, giving the necessary tension to make the string perform its proper scale of vibrations; and the radiated muscle acting upon the membrane, like the moveable bridge of the mono- chord, adjusting it to the vibrations required to be produced;" and he adds: " the difference between a musical ear and one which is too imperfect to distinguish the different notes in music, will ap- pear to arise entirely from the greater or less nicety with which the muscle of the malleus renders the membrane capable of being truly adjusted. If the tension be perfect, all the variations pro- duced by the action of the radiated muscle will be equally correct, and the ear truly musical." In this view, — as unsatisfactory in its basis as it is in some of the details,— Sir Everard completely excludes, from all participation in the function, the internal ear, to which the attention of physiologists, who consider the faculty to be seated in the ear, has been almost exclusively directed. A single case, however, detailed by Sir Astley Cooper,0 prostrates the whole of the ingenious fabric, erected by Sir Everard. Allusion has already been made to the old established fact, that the mem- brane ofthe tympanum may be destroyed without loss of hearing necessarily following. Sir Astley was consulted by a gentleman, who had been attacked, at the age of ten years, with an inflamma- tion and suppuration in his left ear, which continued discharging matter for several weeks. In the space of about twelve months after the first attack, symptoms of a similar kind took place in the right ear, from which matter issued for a considerable time. The discharge, in each instance, was thin, and extremely offensive ; and in it, bones or pieces of bones were observable. In consequence of these attacks he became deaf, and remained so for three months. The hearing then began to return; and in about ten months from the last attack, he was restored to the state he was in when the case was published. Having filled his mouth with air, he closed his nostrils and contracted the cheeks; the air, thus compressed, was heard to rush through the meatus auditorius with a whistling noise, and the hair, hanging from the temples, became agitated by the current of air, that issued from the ear. When a candle was applied, the flame was agitated in a similar manner. Sir Astley passed a probe into each ear, and thought the membrane of the left side was totally destroyed, as the probe struck against the pe- trous portion of the temporal bone. The space, usually occupied by the membrana tympani, was found to be an aperture without one trace of membrane remaining. On the right side, also, a probe a Anat. and Physiol. 5th. Amer. Edit, by Godman, ii. 273, New York, 1829. b Lect. on Comp. Anat. iii. 268. c Philosoph. Transact, for 1800, p. 151, and for 1801, p. 435. MUSICAL EAR. 165 could be passed into the cavity of the tympanum; but, on this side, some remains of the circumference of the membrane could be dis- covered, with a circular opening in the centre, about a quarter of an inch in diameter. Yet this gentleman was not only capable of hearing everything that was said in company, but was nicely susceptible to musical tones; " he played well on the flute, and had frequently borne a part in a concert; and he sung with much taste and perfectly in tune." But, independently of these partial objections, the views, that assign musical ear and acquired language to the auditory apparatus, appear liable to others that are insuperable. The man who is totally devoid of musical ear, hears the sound distinctly. His sense of hear- ing may be as acute as that of the best musician. It is his apprecia- tion that is defective. He hears the sound, but is incapable of com- municating it to others. The organ of appreciation is — in this, as in every other sense — the brain. The physical part of the organ may modify the impression, which has to be made upon the nerve of sense ; the latter is compelled to transmit the impression as it receives it; and it is not until the brain has acted, that perception takes place, or that any idea of the physical cause of the impres- sion is excited in the mind. If, from faulty organization, such idea be not formed in the case of musical tones, the individual is said not to possess a musical ear, but the fault lies in his cerebral confor- mation. We do not observe the slightest relation between musical talent and delicacy of hearing. The best musicians have not neces- sarily the most delicate sense; and, for the reasons already assign- ed, it will be manifest, why the idiot, whose hearing may be acute, is incapable of singing, as well as of speaking. Again, we do not see the least, ratio in animals between the power and character of their music, and the condition of their auditory sense. We are compelled, then, to admit, that the faculties of music and speech are dependent upon the organization of the brain; that they require the ear as a secondary instrument; but that their degree of perfec- tion is by no means in proportion to the delicacy of the sense of hear- ing. In these opinions, Gall,a Broussais,b Adelon,c and other distin- guished physiologists concur. " Speech," says Broussais, " is heard and repeated by all men, who are notdeprivedof the auditory sense, because they are all endowed with cerebral organization fit to pro- cure for them distinct ideas on the subject. Music, when viewed as a mere noise, is also heard by every one, but it furnishes ideas, sufficiently clear to be reproduced, to those individuals only, whose frames are organized in a manner adapted to this kind of sensation." Yet, although we must regard the musical faculty to be intel- lectual, and consequently elevated in the scale, it is hardly neces- sary to say, that the want of it is no evidence of that mental and » Sur les Fonctions du Cerveau, v. 96, Paris, 1825. b Trait^ de Physiologie, translated by Drs. Bell and La Roche, p. 84, 3d Amer. Edit. Philad. 1832. « Op. citat. i. 383. 166 SENSE OF HEARING. moral degradation, which has been depicted by poets and others.8 In the classification of the objects of human knowledge, music has been ranked with poetry; but we meet with striking evidences of their wide separation. Whilst the professed musician is frequently devoid of all poetical talent, many excellent poets have no musical ear. Neither does the power of discriminating musical tones indi- cate that the possessor is favoured with the finer sensibilities ofthe mind; nor the want of it prove their deficiency. It has been a com- mon remark, that, amongst professed musicians, the intellectual manifestations have been singularly and generally feeble ; a re- sult partly occasioned by their attention having been almost en- tirely engrossed from childhood by their favourite pursuit, but not perhaps to be wholly explained by this circumstance ; and, whilst we find them often unmarked by any of the kindlier sympathies, we see those, that are " not moved with concord of sweet sounds," alike distinguished as philosophers and philanthropists. The de- fect, in these cases, differs probably in an essential manner, from one to which attention has been drawn by the late Dr. Wollaston.h In that communication he describes many curious facts, regarding what he terms a peculiarity in certain ears, which seem to have no defect in the general capacity of receiving sound, or in the perception of musical tones, but are insensible to very acute sounds. This insensibility commences when the vibrations have attained a certain degree of rapidity, beyond which all sounds are inaudi- ble to ears thus constituted. Thus, according to Wollaston, cer- tain persons cannot hear the chirp of the grasshopper ; others, the cry of the bat; and he refers to one case in which the note of the sparrow was inaudible. Dr. Wollaston himself was incapable of hearing any sound higher than six octaves above the middle E of the piano forte. The defect would, at first sight, appear to be referable to the physical part of the ear, rather than to the audi- tory nerve, or to the part of the brain concerned in the apprecia- tion of sounds; the vibrations that are performed with great a " The man that hath no music in himself, Nor is not mov'd with concord of sweet sounds, Is fit for treasons, stratagems and spoils ; The motions of his spirit are dull as night, And his affections dark as Erebus : Let no such man be trusted." Shakspeare, " Merchant of Venice," v. i. " Is there a heart that music cannot melt ? Alas! how is that rugged heart forlorn ; Is there, who ne'er those mystic transports felt Of solitude and melancholy born ! He needs not woo the muse; he is her scorn. The sophist's rope of cobweb he shall twine ; Mope o'er the schoolman's peevish page ; or mourn And delve for life in mammon's dirty mine; Sneak with the scoundrel fox, or grunt with glutton swine." Beattie,« Minstrel." b Philosophical Transactions for 1820, p. 306. JUDGMENT OF DISTANCE, ETC., BY SOUND. 167 rapidity, hot being responded to by the parts of the organ destined for this purpose; and, consequently, never reaching the auditory nerve. Researches, however, by Savart,3 — one of the most dex- terous and ingenious experimenters of the day, — seem to show, that the defective appreciation of acute sounds, in such cases, is not owing to their acuteness, but to their feebleness ; that if the sound can be made sufficiently intense, the ear is capable of hear- ing a note of upwards of forty thousand simple oscillations in a second; and that the cases referred to by Wollaston are, conse- quently, owing to defective hearing, rather then to insensibility to very acute sounds. Another acquired perception of the ear is that of forming a judgment of the distance of bodies. This we do by attending to the loudness of the sound; for we instinctively lay it down as a principle, that a loud sound proceeds from a body that is near us, and a feeble sound from one more remote. This is the cause of numerous acoustic errors, in spite of reason and experience. In the theatres, the deception is often well managed, when the object is to give the idea of bodies approaching. The sound — that of martial music, for example — is rendered faint and sub- dued; and, under such circumstances, appears to proceed from the remote distance; and, by adding gradually and skilfully to its intensity, we are irresistibly led to the belief, that the army is approaching ; and the allusion is completed by the appearance of the military band on the stage, allowing its soul-inspiring strains to vibrate freely in the air. In like manner we are deceived by the ventriloquist. He is aware of the law that guides us in our estimation of distance, and, by skilfully modifying the intensity of his voice, according as he wishes to make the sound appear to proceed from a near or a distant object, he irresistibly leads us into an acoustic error. Education or experience is required to enable us to appreciate distances accurately by this sense, as well as to judge of their posi- tion. In the case,detailed by Magendie,3 of a boy, who, after having been entirely deaf until the age of nine, was restored to hearing by M. Deleau, by means of injections thrown into the cavity of the tympanum through the pharyngeal extremity ofthe Eustachian tube, one of the most remarkable points was his difficulty in ac- quiring a knowledge of the position of sonorous bodies. In form- ing our judgment on this subject we require the use of both ears. In all other cases an impression made upon one only would per- haps be sufficient. The common opinion is, that to judge of the direction of a sound we compare the intensity of the impression on each ear, and form our deductions accordingly; and that if we close one ear we are led into errors, which are speedily dissipated by employing both. Still we are often deceived even under these last circumstances, and are compelled to call in the aid of sight. * Journal de Physiologie de Magendie, v. 367. b Journal de Phisiologie, v. 223. 168 SENSE OF HEARING. The blind afford us striking examples of accuracy, in this respect, in their acquired perceptions by the ear. In the B e 1 i s a r of Zeune, the case of a blind man is cited from Diderot; who, guided by the direction of the voice, struck his brother in a quarrel on the forehead, with a missile, which brought him to the ground.a Mr. Wheatstone supposes, that the perception we have of the direction of sounds arises solely from the portion which is trans- mitted through the solid parts of the head, and which, affecting the three semicircular canals, situate in planes at right angles with each other, with different degrees of intensity, according to the direction in which the sound is transmitted, suggests to the mind the corre- sponding direction. If the sound be transmitted in the plane of either of the semicircular canals, the nervous matter in that canal will be more strongly acted on than that in either of the other two; and if it be transmitted in any plane intermediate between any two ofthe rectangular planes, the relative intensities in these two canals corresponding therewith will vary with the direction of the inter- mediate plane ;b and it has been regarded by Dr. Carpenter0 as a powerful argument in support of this view, that in almost every instance in which these canals exist at all, they hold the same rela- tive position to each other as in man, their three planes being nearly at right angles to one another. He properly, however, adds, that the idea must be regarded as a mere speculation, the value of which cannot be decided without an increased knowledge of the laws ac- cording to which sonorous vibrations are transmitted. If the sonorous vibrations before reaching the ear be deflected from their course we are liable to deception, mistaking the echo for the direct or radiant sound. The ideas of magnitude acquired by the ear are few, and to a trifling extent only. They occasionally enable the blind to judge of the size of apartments, and this they can sometimes do with much accuracy. It is well known, that if a sound be confined within a small space, it appears much louder than when the sonorous undu- lations can extend farther; hence the greater noise, caused directly by a pistol fired in a room than in the open air. The sound indi- rectly produced will necessarily be modified by the different reflec- tions or echoes, that may be excited. By attending to these cir- cumstances — to the loudness of the voice and to the intensitv ofthe reverberations occasioned by the walls, and by calling into their aid the experience they have had under similar circumstances — in other words, by effecting a strictly intellectual process — the blind attain the knowledge in question. The velocity of a body is indicated by the rapid succession of the vibrations that impress the ear, as well as by the change in their intensity if the body be moving along a surface or through the air. A carriage, approaching us with great velocity, is detected by the a Rudolphi, Grundriss, u. s. w. Berlin, 1821, &c. b Journal of Science, New Series, ii. 67, Lond. 1827. c Human Physiology, § 359, Lond. 1842. SENSE OF SIGHT. 169 ear, from the rapidity with which the wheels strike against inter- vening obstacles; and by the gradual augmentation in the intensity of the sound thus produced. When opposite to us the intensity is greatest; and a declension gradually takes place until the sound is ultimately lost in the distance. Lastly ; — by audition we can form some judgment ofthe nature of bodies from the difference in the sounds emitted. It has been already remarked, that the timbre or quality of sound can be ac- curately appreciated. By this quality we can distinguish between the sound of wood or of metal; of hollow or solid bodies, &c.; but in all these cases we are compelled to call into aid our ex- perience— without which we should be completely at a loss — and to execute a rapid, but often very complicated, intellectual operation. Audition may be exercised passively as well as actively ; hence the difference between simply hearing, and listening. We cannot appreciate, in man, the precise effects produced on the different portions ofthe ear by volition ; — whether, for example, the advan- tage be limited to the better direction given to the ear, as regards the sonorous body, and to the avoiding of all distraction, by con- fining the attention entirely to the impressions made on this sense ; or whether, by it, the pavilion may not be made somewhat more tense by the contraction of its intrinsic and extrinsic muscles ; — whether the membrana tympani, and the membrane of the foramen ovale be modified by the contraction ofthe muscles ofthe ossicles; or, in fine, the auditory nerve be rendered better adapted for the recep- tion of the impression, and the brain for its appreciation. All these pointsare insusceptible of direct observation and experiment, and are, therefore, enveloped in uncertainty. In some animals—as the horse—the outer ear becomes an acoustic instrument under the guidance of volition; and is capable of being turned in every direc- tion in which a sonorous body may be placed. Like the other senses, that of hearing is largely improved by edu- cation or cultivation. The savage, who is accustomed, in the still- ness of the forest, to listen to the approach of his enemies or of his prey, has the sense so delicate as to hear sounds, that are inaudible to one brought up in the din of the busy world. The blind, for reasons more than once assigned, afford examples of extreme deli- cacy of this as well as of their other remaining senses. They are necessarily compelled to cultivate it more; and, lastly, the musi- cian, by education, attains the perception of the nicest shades of musical tones. The aptitude is laid in cerebral organization, and is developed by the education of the instrument—the ear — as well as of the encephalic or intellectual organ, without which, as we have seen, no such appreciation could be accomplished. OP THE SENSE OF SIGHT OR VISION. The immediate function of the sense of sight is to give us the notion of light and colours. Like the other senses, it is a modifi- vol. i. — 15 170 SENSE OF SIGHT. cation of that of touch, whether we regard the special irritant — light__as an emanation from luminous bodies, or as the vibration of a subtile, ethereal fluid, pervading all space. Under the latter theory it would most strongly resemble the sense last considered. The pleasures and advantages, derived by the mind through this inlet, are of so signal a kind as to render the organ of vision a subject of universal interest. Every one, who lays the slightest claims to a general education, has made it more or less the subject of study, and is frequently better acquainted with its structure and properties than the medical practitioner. Complicated as its organi- zation may seem, it is, in action, characterized by extreme simplicity; yet, " in "its simplicity," as Arnott3 has remarked, " so perfect, so unspeakably perfect, that the searchers after tangible evidences of an all-wise and good Creator, have declared their willingness to be limited to it alone, in the midst of millions, as their one triumphant proof." Into this structure we shall enquire, so far as is necessary for our purpose, after having described the general properties of light; and'then detail the mode in which its various functions are effected, and the knowledge derived by the mind through its agency. The eye is the organ of vision. It varies materially in different animals : in some consisting of a simple capsule, with the final ex- pansion ofthe nerve of sight distributed on its interior, and com- municating externally by means of the transparent cornea, which admits the light. It is in this simple state, that M. de Blainvilleb assimilates it to a bulb of hair, modified for the new function it has to perform. In man, and in the upper classes of animals, the organ is much more complicated in its structure; and in it we have a still clearer example of the distinction between the physical, and the nervous or vital part of the apparatus, than in any of the other organs of sense, — the former consisting of transparent tunics, and humours, which modify the light according to the laws of op- tics, — the latter being a production or expansion of nervous struc- ture, for the reception of the impression of light, and for con- veying such impression to the proper part of the encephalon. There is, besides, attached to the organ, a number of accessory parts or tutamina, which are more or less concerned in the pro- per performance of the function. It will be necessary, therefore, to give a succinct view, not only of the eye, properly so called, but also of these accessory organs, which serve to lodge, move, protect, and lubricate it. The description will not, however, be clearly understood, without premising some general observations on the properties of light, especially as regards its refraction, on which the phenomena of vision are greatly dependent. 1. OF LIGHT. The sun and the fixed stars are the great sources of light. It is given off also from substances in a state of combustion, and from a Elements of Physics, 2d Amer. Edit. vol. ii. P. i. p. 161, Philad. 1836. b De l'Organization des Animaux, Paris, 1825. LIGHT. 171 phosphorescent bodies; and, by entering the eye directly, or after various reflections or refractions, impinges on the optic nerve, and ^ gives the sensation of light. Two main opinions have been entertained regarding the nature of light; the one, propounded by Newton — that it consists of ex- tremely minute particles, emanating from luminous bodies; the other — that of Descartes, Hook, Huygens, Euler, and others, — that it is a subtile, eminently elastic fluid —an ether — pervading all space, the elastic molecules of which, when put in motion by the oscillations of bodies, impress the eye as sonorous vibrations affect the ear. It is not for us to discuss this question of higher physics. We may merely remark, that difficulties attend both hy- potheses. According to that of Descartes, it is not easy to explain, why an opaque body should prevent the undulations from reach- ing the eye—or the change of direction, which the light expe- riences in passing from one medium into another; whilst, accord- ing to that of Newton, it is difficult to conceive, how a luminous body, as the sun, can shed its immense torrrents of light incessantly, without undergoing rapid diminution; and how, with the extreme velocity of light, these particles should not be possessed of sensible momentum ; for it has been found, that a large sunbeam, collected by a burning-glass, and thrown upon the scale of a balance of ex- treme delicacy, is insufficient to disturb the equilibrium. To the hypothesis of Newton it has also been objected, that the particles, being reflected by thousands of bodies, and in innumerable direc- tions, would necessarily jostle and interfere greatly with each other. This objection is not, however, as valid as it appears at first sight. It will be seen hereafter, that the impression of a luminous object remains upon the retina for the sixth part of a second. Admitting it, however, to impress the eye for the 3-J^th part, three hundred particles, per second, would be sufficient to excite a constant and uniform sensation of the presence of light; and since, as we shall find, it traverses sixty-seven thousand leagues in a second of time, if we divide this by three hundred, we shall find a space of six hundred and seventy miles between each particle ; a distance equal to that— in a straight line—between New York and Savannah ; and if we suppose six particles to be sufficient per second, each will be separated from the other by a space of thirty-three thou- sand five hundred miles! Without deciding in favour of either ofthe great theories, that of Newton admitsof more easy application to our subject, and will, there- fore, be employed in the various explanations that may be required. Light, then, proceeding from a luminous body, impinges on the substances that are within its sphere ; and these, by reflecting the whole or a part of it to the eye, become visible to us. In its course, direct or reflected, its velocity is almost inconceivable. From ob- servations made on the eclipses of Jupiter's satellites, by Romer, Cassini, and other astronomers, it has been calculated, that the light of the sun is eight minutes and thirteen seconds in its passage from that luminary to the earth. The distance between the earth 172 SENSE OF SIGHT. and the sun is thirty-three millions of leagues, so that the velocity of light is sixty-seven thousand leagues, or two hundred thousand miles per second ; in other words, in the lapse of a single second it could pass between Washington and Albany — supposing the distance to be three hundred miles — seven hundred times; and could make the tour of the globe in the time it takes us to wink. In consequence of this extreme velocity, — in all calculations, re- garding the light from bodies on the surface ofthe globe, it is pre- sumed to reach the eye instantaneously ; for, granting that a lumi- nous body at Albany could be seen at Washington, the light from it would reach the eye in the ^th part of a second. Inconceivable as this velocity is, it is far surpassed by that of the attractive power exerted between the heavenly bodies. " I have ascertained," says La Place, " that between the heavenly bodies all attractions are transmitted with a velocity, which, if it be not infinite, surpasses several thousand times the velocity of light; and we know that the light ofthe moon reaches the earth in less than two seconds." An annotator on the works of this distinguished mathematician is more definite, affirming, " that the gravific fluid passes over one million of the earth's semi-diameters in a minute of time." Its velocity is eight millions of times greater than that of light. A series of particles, succeeding each other in a straight line, is called a ray of light. The light which proceeds from a radiant point, forms diverging cones, which would be prolonged indefi- nitely did they not meet with obstacles. In its course, it loses its intensity according to a law, which seems applicable to all influ- ences radiating from a centre. If a taper be placed in the middle of a box, each one of whose sides is a foot square, all the light must impinge upon the sides of the box ; if it be placed in a box, whose sides are two feet square, the light will shine upon them from double the distance, but it will be distributed over four times the surface. The intensity of the light, then, in this case, as in every other, diminishes according to the square of the distance from the luminous body. According to this rule, those planets which are nearer the sun than we are, must receive the light and also the heat — for the same law applies to caloric — in much greater in- tensity ; whilst the more distant luminaries can receive but little caloric, or light, in comparison with our earth ; hence, perhaps, the necessity for the satellites by which they are accompanied, and by whose agency the light of the sun is reflected to the planet, and the deficiency is, in some measure, compensated. In proceeding from a luminous body, the rays, cones, ox pencils of light must traverse intermediate bodies, in order to reach the eye. These bodies are called media. Air is the common medium; and when, in this way, the light has reached the exte- rior of the organ, the farther transmission is effected through dif- ferent transparent humours, which consequently form so many media. In its course through the different media, light may remain unmodified : it may proceed in the same straight line; or it may meet with an obstacle which arrests it altogether, or reflects LIGHT. 173 it; or, again, it may traverse media of different natures and densi- ties, and be made to deviate from its original course, or be refracted. When a ray of light falls upon an Fig. 22. opaque body, as upon a bright me- *>\ tallic or other mir- dicular. Suppose i~' I J to represent a plate of polished metal, or of glass, rendered opaque by a metal spread upon its posterior surface, as in the common looking-glass. The rays, proceeding from an observer at K, will be reflected back to him in the same line K C ; that is, in a line perpendicular to C, the point of incidence. The observer will, therefore, see his own image; but for reasons t.o be mentioned hereafter, under the head of optical illusions, he will seem to be as far behind the mir- ror as he really is before it, or at E. Suppose, on the other hand, that the observer is at A, and that a luminous body is placed at B; in order that the rays, proceeding from it, shall impinge upon the eye at A, it is necessary that the latter be directed to that point of the mirror from which a line, drawn to the eye, and another to the object, will form equal angles with the perpendicu- lar ; in other words, the angle B C K, or angle of incidence, must be equal to the angle of reflection, A C K. In this case, again, the object will not appear to be at B, but in the prolongation of the line A C, at H, as far from the point of incidence, C, as B is. Except in the case of illusions, the study of the reflection of light or catoptrics does not concern vision materially. It is on the principles of dioptrics, that the chief modifications are effected on the progress of the light through the physical part of the organ ; and, without some knowledge of these principles, the sub- ject would be totally unintelligible. It is necessary, therefore, to dwell at some length on this topic. Whenever a ray of light passes through diaphanous or transparent bodies of different densities, it is bent or made to deviate from its course, and such deviation is 15* 174 SENSE OF SIGHT. called refraction ; the ray is said to be refracted ; and, owing to its being susceptible of such refraction, it is held to be refrangible. The point, at which a ray of light enters a medium, is called the point of immersion ; and that, by which it issues from such me- dium, the point of emergence. Instead of considering the medium I J opaque, let us regard it as transparent. C, in this case, will be the point of immersion for the incident rays that meet there; and L and F will be the points of emergence for the rays K E and A C F G, respectively. If a ray of light, as K C, falls per- pendicularly on the surface of any medium, it continues its course through the medium without experiencing any modification, and emerges in the same straight line. Hence a body at L will appear in its true direction and distance to an observer at K looking di- rectly downwards on a pool of water, I J. If, on the other hand, a ray of light, as A C, after having passed through air, falls ob- liquely upon the surface of the water B ; by entering a medium of different density, it is deflected from its course; and, instead of proceeding in the direction C H, it is refracted, at the point of im- mersion, in the direction C F— that is, towards the perpendicular K E. If, again, the ray emerges at F into a medium of the same density as that through which it passed in the course A C, it will proceed in a line parallel to A C, or in the direction F G, or it will wander from the perpendicular. The cause of this difference in the deflections, produced by different media, is not easy of ex- planation. The fact alone is known to us, that bodies refract light differently according to their densities and nature. If the light proceeds from a rarer to a denser medium it is attracted or refracted towards the perpendicular; if, on the contrary, it passes from a denser to a rarer medium, it is refracted from the perpen- dicular. The ray A C passed from a rarer medium, — the air, — into a denser, I J — water ; it was refracted in the direction C F, towards the perpendicular K E. On emerging at F, circum- stances were reversed ; it wandered from the perpendicular M N, and in the direction F G, parallel to A C, because the media, above and below I J, were identical. We can now understand, why water, saline solutions, glass, rock-crystal, &c, have higher refrac- tive powers than air. They are more dense. The nature or character of bodies also influences greatly their refractive powers. Newton observed this, in his experiments upon the subject, and has furnished science with one of its proudest tro- phies, by his prognostic, in the then infant state of chemistry, that water and the diamond would be found to contain combustible in- gredients. The diamond or brilliant is one of the most refractive of known substances, and this is one of the sources of its brilliancy. The opinion of Newton, it is hardly necessary to say, has been triumphantly confirmed. This refraction of the rays, that fall ob- liquely upon a medium, gives rise to numerous optical illusions. The ray proceeding from F, in the bent course F C A, will impinge on an eye at A ; and the object F will appear to be at / The pool will consequently seem shallower. In like manner, an object LIGHT. 175 0 in the air would not be perceptible to an eye in the water at F, in the direction 0 C F ; whilst one at A would be distinctly visi- ble,— the ray from it proceeding in the direction A C F, but ap- pearing to come straight to the eye in the direction 0 C F. . All transparent bodies, at the same time that they refract light, reflect a portion of it. This is the cause ofthe reflections we no- tice on the glass of our windows, and of the image perceptible in the eye. The same substance has always the same refractive power, whatever may be its shape: — in all cases, the sine of the angle of refraction holding the same ratio to the sine of the angle of incidence, whatever may be the incidence. The angle of in- cidence is the angle formed by the incident ray with a perpen- dicular raised from the point of immersion; the angle of refraction that formed by the refracted portion of the ray with the same perpendicular. In Fig. 22, A C K is the angle of incidence of the ray A C ; and L C F the angle of refraction. The sines of these angles respectively are the lines P Q and L F. But although the media may refract the rays of light equally, the form of the refract- ing body will materially modify their arrangement. The perpen- diculars to the surface may approach or recede from each other; and if this be the case the refracted rays will approach or recede from each other likewise. Where the body has plane and parallel surfaces, as in the glass of our windows, the refraction, experienced by the ray on entering the glass, is corrected by that which occurs on its emergence ; and although the light may not pass in one straight line, it proceeds in parallel lines, separated by a space dependent upon the thickness of the refracting body and the obliquity of the incident ray. If the medium be very thin, as in a pane of glass, the rays do not appear deflected from their original direction. In Fig. 22, the in- terval between the direct ray and the ray A C F after its emergence is that between G and H. If the surfaces of the diaphanous body be plane, but in- clined towards Fig. 23. ing that expe- c L .....'""'............. rienced during its passage through the body, is added to it; and the rays are deflected from their course to an extent equal to the sum of the two refractions. The ray A B, Fig. 23, after impinging upon the side D L of the prism, at B, instead of continuing its course in the direction B J, is refract- ed towards the perpendicular C B F, —the medium being denser than air; and on emerging into the rarer medium, instead of con- tinuing its course in the direction G I, it is refracted in the line 176 SENSE OF SIGHT. G H ox from the perpendicular K J. Again, if the surfaces of the medium be convex, the rays are so situate, after refraction, as to converge behind the refracting body into a point called the focus, which is nearer to the Fig. 24. medium the less the. divergence of the rays, or in other words, the more distant the lumi- nous object. Fig. 24 exhibits a pencil of rays, proceeding from a radiant point at A, and meeting at a focus at B ; the dotted lines being the perpendiculars drawn to the surface at the points of im- mersion and emergence. Lastly, if the surfaces of the medium be concave, as in Fig. 25, the luminous rays, proceeding from a radiant point as at A, are rendered so divergent, that if we look for a focus here it must be anterior to the medium or at G. A knowledge of these facts has given occasion to the construction of numerous invaluable optical instruments, adapted to modify the luminous rays, so as to change the situation in which bodies are seen, to augment their dimensions, and to render them more lumi- nous and visible, when remote and minute. It is, indeed, to this branch of science that we are indebted for some of the most im- portant information and advantages, that we possess in the domains of science and art. The simplest of these instruments are bodies, shaped like a lentil, and hence called lenses. They are composed of two segments of a sphere. The medium in Fig. 24 is a double convex lens; that in Fig. 25, a double concave. The manner in which they modify the course of the luminous rays passing through them has been sufficiently described. The study of the refraction of light leads us to the knowledge of an extremely Fig- 25. important fact; D which, when it was first made known by d Newton, ex- cited universal astonishment ; — viz., that a -g. ray of light is itself compo- sed of several coloured rays • ~i~£ differing from \- \.......- each other in ^^ F their refrangi- bility. If a LIGHT. 177 White beam of the sun's light be admitted through the hole of a win- dow-shutter, E F, into a dark chamber, it will proceed in a direct line to P, and form a white spot upon the wall, or on a whitened screen placed there for the purpose. But if a glass prism, B A C, be.placed, so that the light may fall upon its surface, C A, and emerge at the same angle from its second surface,B A, in the direc- tion g G, the beam will expand; and if, after having emerged, it be received on the whitened screen, M N, it will be found to occupy a considerable space ; and, instead of the white spot, there will be an ob- long image of the sun, K L, consisting of seven colours; red, orange, yellow, green, blue, indigo, and violet. Each of these colours admits of no farther decomposition, when again passed through the prism; and the whole lengthened image of the sun is called the prismatic or solar spectrum. In this dispersion of the coloured rays, it will be observed, that the red ray is the least turned from its course; and is hence said to be the least refrangible ; whilst the violet is the most so. Such is the spectrum, as depicted by Newton: since his time it has, by some, been considered to consist of three colours,—red, yel- low, and blue ; as certain of the colours can be composed from others,—the green, for example, from the blue and the yellow. Wol- laston made it to consist of four ; red, green, blue, and violet: Sir J. Herschel of four; red, yellow, blue, and violet: and, more recent- ly, Sir David Brewster has restricted it to three; red, yellow, and blue. The causes which have led to these various divisions, it is not our province to explain. Each of the rays, of which the spectrum is composed, appears to have a different calorific and chemical action ; but this is a sub- ject, that nowise concerns the function under consideration ! The decomposition of light into its constituent rays enables us to explain the cause of the colour of different substances. When white light impinges upon a body, the body either absorbs all the rays that compose it; reflects all; or absorbs some, and re- flects others. If it reflects the whole of the light to the eye, it is of a white colour ; if it absorbs all, or reflects none, it is black ; if it reflects only the red ray, and absorbs all the rest, it is red, and so of the other colours. The cause, why one body reflects 178 SENSE OF SIGHT. R R- R"- Rf one ray, or set of rays, and absorbs others, is totally unknown. It is conceived to be owing to the nature and particular arrange- ment of its molecules. This is probable. But we are still as much in the dark as ever. It is accounting for the ignotumper ignohus. Two other points require a brief notice, being intimately con- cerned in vision ; — the aberration of sphericity, and the aberra- tion of refrangibility. It has been remarked, that the rays of light — after passing through a convex lens, or medium whose sur- faces are convex — converge, and are brought to a focus behind it. The whole of the rays do not, however, meet in this focus. The rays that are nearest the axis, R" F of the lens, Fig. 27, are re- fracted to a focus more remote from the lens, than those that fall on the lens at a distance from the axis. The rays R', R", and R'", are brought to a focus at F, whilst the rays RL,andR"",L' converge at the point /, much nearer the lens. In like manner rays which fall upon the lens in- termediate be- tween the rays R and R', will have their foci intermediate between / and F. This diversity of focal distances is called the spherical aberration, or the aberration of sphericity: the distance / F is the longitu- dinal spherical aberration ; and B A the lateral spherical aberra- tion, of the lens. This aberration is the source of confusion in common lenses ; and, as it is dependent upon the shape of the lens, it has been obviated, by forming these instruments of such degrees of curvature, that the rays, falling upon the centre or margins of the lens, may all be refracted to the same focus. This is effectually accomplished by lenses, whose sections are ellipses or hyperbolas. In a common lens, the inconvenience is obviated by employing lenses of a small number of degrees, or by interposing an opaque body — called, by the opticians, a diaphragm — anterior to the lens, so that the rays of light can only impinge upon the central part, and consequently be refracted to the same focus. This dia- phragm is present in all telescopes, and occupies the situation of the curves D and D', so as only to admit the rays R', R", and R'", to fall upon the lens. Such an apparatus, we shall find,exists in the human eye. Lastly, — it has been already observed, that the different rays, constituting the solar spectrum, are unequally refrangible, — the red being the least, the violet the most so ; hence the cause of their dispersion in the spectrum. It follows from this fact, that, whenever light experiences refraction, there must be more or less LIGHT. 179 dispersion of its constituent rays ; and the object, seen by the re- fracted ray, will appear coloured. This must, of course, occur more particularly near the margins of the lens, where the sur- faces becomes less and less parallel until they meet. The incon- venience, resulting from this dispersion, is called the aberration of refrangibility, or chromatic aberration, and it has been at- tempted to be obviated by glasses, which have been termed, in consequence, achromatic' These are made by combining trans- parent bodies of different dispersive powers, in such sort, that they may compensate each other, and thus the object be seen in its proper colours, notwithstanding the refraction. Dr. Blair found, for example, that by enclosing muriate of anti- mony B E, between two convex lenses of crown glass, AD and C F, the parallel rays R, R E \ and R were re- fracted to a single focus at P without the slightest trace f& ..--""" DEF of secondary co- sift-""" lour. Newton was of opinion, that the light, in traversing a refracting medium, always experiences a dispersion of its rays, proportional to its re- fraction. He therefore believed, that it would be impossible to fabricate an achromatic glass. This is one of the rare cases in which that illustrious philosopher erred. Since his time — and chiefly by the labours of Dollond — such instruments have been formed on the principles above mentioned ; so as to greatly diminish the in- conveniences sustained from theuse of common lenses'; although still not perfectly achromatic. The inconvenience is farther obvi- ated by the diaphragm in telescopes, already referred to. As the dispersion is most experienced near the margin of the lens, it shuts off the rays, which would otherwise fall upon that portion, and diminishes the extent of aberration. The human eye is achromatic. It is obviously essential that it should be so ; and this result is pro- bably owing to a combination of causes. It is formed of media of different dispersive powers. Its lens is constituted of layers of dif- ferent densities, and it is provided with a diaphragm of singularly valuable construction. Such are the prominent points ofthe beautiful science of optics, that chiefly concern the physiologist, as an introduction to vision. Others will have to be adverted to, when we consider the eye in action. 180 SENSE OF SIGHT. 2. ANATOMY OP THE ORGAN OP VISION. The human eye is almost spherical, except for the prominence at its anterior and transparent part — the cornea. It has been com- pared to a telescope, and with much propriety; as many of the parts of that instrument have been added to execute particular offices, which are admirably performed by the eye — the most per- fect of all optical instruments. Every telescope consists, in part, of a tube, which always comprises pieces, capable of readily en- tering into each other. Within this cylinder are several glasses or lenses, placed in succession from one extremity to the other. These are intended to refract the rays of light and to bring them to deter- minate foci. Within the telescope is a kind of partition of paper or metal, having a round hole in its centre, and usually placed near a convex glass, for the purpose of diminishing the surface of the lens accessible to the rays of light, and obviating the spherical aber- ration. The interior of the tube and of the diaphragm is coloured black, to absorb the oblique rays, which are not inservient to vision, and thus to prevent them from causing confusion. This arrange- ment is nearly a counterpart of that which exists in the eye. The tube of the instrument is represented by three membranes in su- perposition, — the sclerotic, choroid, and retina ; the latter being the one, that receives the impression of light. Within this case are four refracting bodies, situate one behind the other; and all intend- ed to bring the rays of light to determinate foci, viz. — the cornea, aqueous humour, crystalline lens, and vitreous humour. Lastly, in the interior of the eye, near the anterior surface of the crystal- line lens, is a diaphragm — the iris, having an aperture in its centre — the pupil. These different parts will demand a more detailed notice. 1. Coats of the Eye, &c. — Before describing the coats of the eye that are usually admitted, it may be remarked, that the eye- ball is invested with a membranous tunic, which separates it from the other structures of the orbit, and forms a smooth, hollow sur- face by which the motions of the eye are facilitated. This invest- ment has been variously called, — the cellular capsule of the eye, the ocular capsule, tunica vaginalis oculi, and the submuscular fascia. The sclerotic is the outermost proper coat of the eye. It is that which gives shape to the organ, and which constitutes the white ofthe eye. It is of a dense, resisting, fibrous nature, belonging to what Chaussier calls the albugineous tissue. Behind, it is pene- trated by the optic nerve ; and before, the cornea is dovetailed into it. It has, by some anatomists, been considered a prolongation of the dura mater, accompanying the optic nerve; whilst the choroid has been regarded as an extension of the pia mater, and the retina of the pulp of the nerve. The sclerotic is the place of insertion for the various muscles that move the eyeball, and is manifestly intended for the protection of the internal parts of the organ. ORGAN OF VISION. 181 Fig. 29. Immediately within the sclerotica — and feebly united with it by vessels, nerves, and cellular tissuea — is the choroid coat; — a soft, thin, vascular, and nervous membrane. It completely lines the scle- rotic, and has consequently the same shape and extent. Behind, it is perforated by the optic nerve; before, it has the iris united with it; and within, it is lined by the retina, which does not how- ever adhere to it, — the black pigment separating them from each other. It is chiefly composed of the , ^ f«** *JSL» „, v«». v.r. Ciliary VeSSelS and nerves, ticosa;. 2, 2. Ciliary nerves. 3. A long ciliary artery and and consists of two distinct nerve- 4- ciliary ligament- 5Iris> *• **&.-{*«»*.) lamina?, to the innermost of which Ruysch — the son—gave the name membrana Ruyschiana. In fishes these laminae are very perceptible, being separated from each other by a substance, which Cuvier considers to be glandular. The choroid is impregnated and lined by a dark-coloured mucous pigment, called pigmentum nigrum. In some cases, as in the albino, this substance which is exhaled from the choroid, is light-coloured, approximating to white. Leopold Gmelin,b conceives, that it approaches the nature of indigo ; Dr. Young,* regards it as a mucous substance, united to. a quantity of carbonaceous matter, upon which its colour depends, and Berzelius,d from his chemical investigations, considers it to consist chiefly of carbon and iron ; but Professor Jacob thinks it obviously an animal principle sui generis, its elements being oxy- gen, hydrogen, carbon, and nitrogen. Dr. Apjohn found 100 parts, in a dry state, leave, when incinerated, 4-46 of a calx consisting of chloride of calcium, carbonate of lime, phosphate of lime, and per- oxide of iron. Mr. T. W. Jones has examined microscopically the layer of black pigment on the inner surface of the choroid. He states that it possesses organization, and constitutes a real membrane, consisting of very minute flat bodies of an hexagonal form, joined together at their edges.e On the outer side of the bottom of the cavity of the eye, there is a small shining space, des- a In the situation of this cellular tissue, Arnold describes a serous membrane, Spinn-webenhaut, Arachnoidea oculi, Lamina fusca scleroticx. — Arnold liber das Auge, Tab. iii. Fig. 2, and Weber's Hildebrandt's Handbuch der Anatomie, iv. 68, Braunschweig, 1832. b Dissert. Sistens Indagationem Chemicam Pigmenti Nigri Oculorum Taurorum. Gotting. 1812. e Medical Literature, p. 521, Lond. 1813. d Medico-Chirurg. Trans, iii. 225. » Art. Eye, by Dr. Jacob, in Cyclop, of Anat. and Physiol. Part x. for June, 1837, p. 181. VOL. I.-- 16 182 SENSE OF SIGHT. titute of this pigment, through which the colours of the membrana Ruyschiana appear. This spot is termed the tapetum. It is met with only in quadrupeds. The retina is the last coat, if we except a highly delicate serous membrane —discovered by Dr. Jacob,a of Dublin, and called after him Tunica Jacobi,— which is interposed between the retina and the choroid coat.b Mr. George H. Fielding, of Hull,* has also affirmed, that immediately behind the retina, and in connexion with it, there is a peculiar membrane, separable into distinct layers from the choroid, and supplied with bloodvessels, which he pro- poses to name membrana versicolor. He presumes, that it re- ceives the vibrations of light, and communicates them to the retina: the eyes, used for experi- ment, were those of the ox and the sheep. The retina lines the choroid; and is a soft, thin, pulpy, and grayish membrane, formed chiefly, if not wholly, by the final expansion of the optic nerve. Ribes,d indeed, esteems it a distinct membrane, on which the optic nerve is distributed; — a structure more con- sistent with analogy. On its 1. Terminating anteriorly in a scalloped border. 2. inner SlirfaCe It IS in Contact Foramen of Sommering. 3. Zonula ciliaris. 4. Crys- "with the membrane of the talhne lens. — {Wilson.) . , . vitreous humour, but they are not adherent. Anteriorly, it terminates near the anterior extre- mity of the choroid, forming a kind of ring, from which an extremely delicate lamina is given off. This is reflected upon the ciliary processes, dips into the intervals separating them, and, according to some anatomists, passes forward as far as the crystalline. Re- cent observers— B. C. R.Langenbeck,Treviranus, Gottsche, Volk- mann, E. H. Weber, Michaelis, and others, have examined mi- nutely into the anatomy of the retina, and have shown that it con- sists of several layers : — Langenbeck says three ; Michaelis, four.e The outer layer of the true retina is considered to be formed by the optic nerve, which, at its entrance into the eye, divides into numerous small fasciculi of ultimate fibrils, that spread them- * Philosoph. Transact, for 1819; Medico-Chirurg. Transactions, xii. Lond. 1823, and Art. Eye, in Cyclop, of Anat. and Phys. p. 186. b Philosophical Transactions, for 1829, p. 300. « Second Report of the British Association, for the Advancement of Science; and Amer. Journal ofthe Med. Sciences, Nov. 1833, p. 220. 11 Memoir, de la Societe Medicate d'Emulation, vii. 86. e J. Muller's Report on the Progress of Anatomico-Physiological Science, for the year 1836, m Muller's Archiv. 1837, Heft 3 ; and Brit, and For. Med. Rev. Jan. 1838, p. 298 ; a!so,W. Clay Wallace, Treatise on the Eye, &c. 2d edit. New York, 1839 ; and Lond. Med. Gaz. Oct. 20, 1838. Fig. 30. ORGAN OF VISION. 183 Part of the retina of a Frog seen from m, - ,. . the outer surface. Magnified 300 times. The surface of the retina, in -{Treviranus.) selves out, and inosculate with each other by an interchange of fibrils, so as Fig. 31. to form a net-like plexus. From this plexus, the fibres of which lie in the plane of the surface of the vitreous hu- mour, a very large number of fibrils arises in a direction perpendicular to the surface, so as to be all directed towards the centre of the eye. These pass through a delicate layer of cellular tis- sue, containing a minute plexus of bloodvessels, and'from this every fibril receives a sheath, which envelopes its extremity, and thus forms a minute papilla. contact with the vitreous humour, is wholly composed of these papillae, which are closely set together and which Dr. Carpentera thinks there can be little doubt are iden tical with the globules of the retina of Weber. The diameter of these globules in man, accord- Fjgi 32. ing to Weber, is from the -g^lh to ^th of an inch. About a sixth of an inch on the outside of the optic nerve, and in the direction of the axis of the eye, or of a line drawn perpendi- cularly through the centre of the cornea, is a yellow spot, about a line in extent, having a depression in its centre. These are the limbus luteus ox macula lutea, and foramen centrale of Sommering.b The yellow spot does not ex- ist in the foetus ;c and the folds, described by Sommering as surrounding the yellow spot, would appear to be a post mortem appearance. In the exami- nation of two convicts, three hours after execution, the foramen was not seen satisfactorily.*1 The retina receives many bloodvessels, which proceed from the central artery ofthe retina, or of Zinn. This vessel — it is im- portant to observe — enters the eye through the centre of the op- tic nerve, the porus opticus — and, before passing directly through the vitreous humour, sends off lateral branches to the retina. 2. Diaphanous parts of the Eye. — The parts which act as refracting bodies, are either transparent membranes, or fluids con- tained in capsules, which give them a fixed shape. These a Human Physiology, p. 262, Lond. 1842. b Sommering, in Comment. Societ. Gotting. torn. xiii. 1795-98 ; A. ab Ammon, de Genesi et Usu Maculae Luteae, &c. Vinar. 1830; J. Muller's Report, in op. cit. and Grube, in Muller's Archiv. 1840, Heft i.; and Brit, and For. Med. Rev., July, 1840,p. 254. ' Rudolphi, Grundriss der Physiologie, B. ii. Abtheil, 1, s. 176, Berlin, 1823. a W. E. Horner, Special and General Anatomy, 5th edit. p. 426, Philad. 1839 ; and J. Pancoast, in Wistar's Anatomy, 8th edit. Philad. 1842. Papillas of the retina of the Frog, seen from the side turned towards the vitreous humour ; the four higher rows are seen side- ways. Magnified 300 times. — (Treviranus.) 184 SENSE OF SIGHT. Fig. 33. parts are the cornea, aqueous humour, crystalline, and vitreous humour. The cornea is the convex transparent part of the eye, advancing in front of the rest of the organ, as a watch-glass does before the case, and appearing like the seg- ment of a smaller sphere super- added to a larger. It was, for a long time, considered to be a prolongation of the sclerotic ; but they are manifestly distinct mem- branes, being separable by mace- ration. The posterior surface is concave, and, between it and the iris, is the small space occupied by the aqueous humour, called the anterior chamber of the eye. The cornea is generally consider- ed to be composed of several thin laminae in super-position, which have been compared to horn, and hence the name of the mem- brane ; but Mr. T.Wharton Jones3 denies this, and describes it as consisting merely of interweaving bundles of fibres. Like the cor- neous tissue in general, it possesses In animals, the density and con- vexity of the cornea vary with the media in which they exist, and with the condition of the other refractive parts of the eye. In old age, the cornea is harder, tougher, and less transparent than in youth, and it frequently becomes completely opaque in its circum- ference, presenting the appearance called arcus senilis, — in Ger- man, Greisenbogen. The aqueous humour is a slightly viscid fluid, which occupies the whole of the space between the posterior surface of the cornea and the anterior surface of the crystalline. This space is divided by the iris into two chambers — an anterior and a posterior — the latter being the small interval between the hinder surface ofthe iris, and the anterior surface of the crystalline. Sir David Brewsterb erroneously asserts that the posterior chamber contains the crys- talline and vitreous humours; and Dr. Arnott,* that the anterior and posterior chambers of the eye are the compartments before and behind the crystalline. Anatomists are not agreed, whether the aqueous humour have a proper membrane, which secretes it, or whether it be not an exhalation from the vessels of the iris and 1 Introduction to W. Mackenzie's Practical Treatise on Diseases of the Eye, Lond, 1§40. b A Treatise on Optics, edit. cit. p. 241. c Elements of Physics, &c. 2d Amer. Edit. vol. ii. P, i. p. 162, Philad. 1836, Posterior Segment of Transverse Section of the Olobe of the Eye seen from within. 1. Divided edge of three tunics. Membrane covering whole internal surface is the retina. 2. Entrance of optic nerve with arteria cen- tralis retinae piercing its centre. 3, 3. Rami- fications of arteria centralis. 4. Foramen of Sommering, in centre of axis of eye ; the shade from sides of the section obscures the limbus luteus which surrounds it. 5. A fold of the retina, which generally obscures the fora- men of Sommering after the eye has been opened. —( Wilson.) neither bloodvessels nor nerves. ORGAN OF VISION. 185 ciliary processes. Ribes, indeed, derives it from the vitreous hu- mour. Howsoever secreted, it is very rapidly regenerated when evacuated; as it must be in every operation for cataract by ex- traction. It is not lodged in cells, and hence readily flows out when the cornea is punctured. The quantity of aqueous humour, iri the adult, is about five or six grains. Its specific gravity is not rigorously established, but it differs slightly from that of water, being a little greater. According to Berzelius, it is composed of water, 98-10 ; a little albumen ; muriates and lactates, 1*15 ; soda, with a substance soluble in water, 0*75.a The crystalline lens is a small body, of a crystalline ap- pearance, and lenti- cular shape, whence its name. It mea- sures in the adult, about 1-33 of an inch in its greatest cir- cumference ; and is about 2h lines thick at its centre. It is situate between the aqueous and vitreous humours, and at about one-third of the antero-posterior diameter of the or- gan. A depression, at the anterior sur- face of the vitreous humour, receives it, and a reflection of the proper mem- brane of this hu- mour passes over it. The crystalline is surrounded by its capsule, the interior of which is bathed by a slightly viscid and transparent secretion, called liquor Morgagnii. The lens is more convex behind than before ; the radius of its anterior surface being, according to Brewster,b 0-30 of an inch ; and that of its posterior surface 0-22 of an inch. It consists of a number of concentric ellip- soid laminae, increasing in density from the circumference to the centre. Some fibres detach themselves from the different laminae to those immediately beneath, constituting the sole bond of union * For some Microscopical Observations on the Anatomy of the Aqueous Capsule, by Dr. Werneck, see Von Amnion's Zeitschrift fiir Ophthalmolog. B. iv. und v. 1837 ; cited in British and Foreign Medical Review, July, 1838, p. '^05. 1 Op. citat. p. 242. See, also, Philos. Transact, for 1835, p. 366. 16* Fig. 34. Longitudinal Section ofthe Globe ofthe Eye. 1. Sclerotic, thicker behind than in front. 2. Cornea, received within anterior margin of sclerotic, and connected with it by means of a bevelled edge. 3. Choroid, connected anteriorly with (4) ciliary ligament, and (5) ciliary processes. 6. Iris. 7. Pupil. 8. Third layer of eye, retina terminating anteriorly by abrupt bor- der at commencement of ciliary processes. 9. Canal of Petit, encir- cles the lens (12); the thin layer in front of this canal is the zonula ciliaris, a prolongation of vascular layer of retina to the lens. 10. Anterior chamberof eye containing aqueous humour; lining mem- brane by which the humour is secreted is represented in diagram. 11. Posterior chamber. 12. Lens, more convex behind than before, enclosed in its proper capsule. 13. Vitreous humour enclosed in hyaloid membrane, and in cells formed in its interior by that membrane. 14. Tubular sheath of hyaloid membrane, which serves for the passage of the artery of capsule of the lens. 15. Neurilemma of optic nerve. 16. Arteria centralis retinae, em- bedded in centre. — {Wilson.) 186 SENSE OF SIGHT. that exists between them. Of old it was believed that the crys- talline was of a muscular structure, and capable of modifying its own convexity, so as to adapt the eye to distances. This was the opinion of Descartes; and it has more recently been revived with modifications by Dr. Young.3 Its muscularity is, however, by no means established, although its fibrous character is unquestionable. The specific gravity of the human crystalline is said by Chene- vixb to be 1-0790. He considered it to be composed chiefly of albumen : according to an analysis,however, of Berzelius0 it would appear to contain 35-9 parts, in the hundred of a matter very analo- gous to the colouring matter of the blood.d The vitreous humour, so called in consequence of its resem- blance to melted glass, occupies the whole ofthe cavity ofthe eye behind the crystalline. It is convex behind, and concaye before, and is invested by a delicate, thin transparent membrane, called tunica hyaloidea, which furnishes prolongations internally, that divide it into cells. It is owing, indeed, to this arrangement ofthe membrane, and not to the density of the humour, that it has the tenacity of the white of egg. Its density does not differ materially from that of the aqueous humour : — their specific gravities being stated at 1-0009, and 1-0003 respectively. The cells, formed by the hyaloid membrane, are not all of the same shape and size. They communicate freely with each other, and are well represented in Fig. 34. At the anterior part, where the hyaloid membrane reaches the margin of the crystalline, it is separable into two laminae ; one of which is reflected over the anterior, the other over t\\e posterior surface of the lens. Between these laminae, and at their junction round the crystalline, a canal exists, into which air may be introduced: it then exhibits a plaited arrangement, and has been called the bullular canal of Petit f and, by the French writers, the canal godronne, or simply the canal of Petit. This canal is generally conceived to be devoid of aperture; but Jacobson affirms, that it has, in its sides, a number of minute foramina, which admit the entrance and exit of the aqueous humour. The composition of the vitreous humour, according to Berzelius/ is as follows : — Water, 98-40 ; albumen, 0-16 ; muriates and lac- tates, 1-42 ; soda, with an animal matter, soluble only in water, 0-02. Its absolute weight is fifteen or twenty times greater than that of the aqueous humour. 3. It was remarked, in the comparison drawn between the eye and the telescope, that a diaphragm exists in the former, called the iris; and sometimes uvea. Generally, however, the latter term is appropriated to the posterior lamina of the iris. By some anatomists, the iris is conceived to be a prolongation of the choroid : by others, to consist of a proper membrane, of a muscular cha- racter ; and, by others again, to be essentially vascular and ner- 1 Philos. Transact, for 1793, p. 169 ; and Med. Literature, p. 521, Lond. 1813. b Philosoph. Transact, for 1803, p. 195. c Medico-Chirurgical Transact, iii. 253. a Werneck, op. cit. <- Memoir de l'Academie des Sciences, Paris, 1723 and 1728, and Haller. Element. Physiol, xvi. 2, 18. f Medico-Chirurgical Transactions, iii. 253. ORGAN OF VISION. 187 Fig. 35. Internal view ofthe Iris. vous; the vessels and nerves being distributed on an erectile tissue.3 There is, in the views of both anatomists and physiologists, much discrepancy regarding the structure and functions of this portion of the eye. Edwards,b of Paris, affirms, that it consists of four laminae, two'of which are extensions of the laminae composing the choroid; a third belongs to the membrane of the aqueous humour, and is reflected over its anterior surface; and the fourth is the proper tissue of the iris. Magendie0 asserts, that the most recent anatomical investigations prove the membrane to be muscular ; and to be composed of two sets of fibres; the outermost radiating, whose office is to dilate the pupil; the innermost circular and con- centric, for the purpose of contracting it. The arrangement of these fibres is presented in Fig. 35 ; which is an internal view of the human iris, mag- nified three diameters ; and Fig. 36, an external view, exhibiting the sur- face to consist essentially of a plexus of bloodvessels ; both are taken from the microscopic investigations of Mr. Bauer, and Sir Everard Home.d These vessels, and nerves, are ramifi- cations of the ciliary,—the nerves arising from the opthalmic ganglion and nasal branch of the fifth pair. Berzelius,e too, affirms, that the iris has all the chemical characters of muscle. The iris is the coloured part of the eye, seen through the trans- parent cornea; and, according to the particular colours reflected from it, the eye is said to be blue, gray, hazel, &c. In its centre is an opening, called the pupil, through which alone the rays of light can reach the lens. This opening can be enlarged or contracted by the contrac- tion or dilatation of the iris; and in this respect it is perpetually varying, according to circumstances. In man, the pupil is circular, but it differs greatly in its dimensions and shape in different animals. On the posterior surface of the iris, or on the uvea, the pigmentum nigrum exists, as on the choroid. This layer has likewise External view of the iris. 1 Lepelletier, Physiologie M6dicale et Philosophique, Paris, 1832, torn. iii. p. 158. b Bullet, de la Societe Philom. etc. 1814, p. 81. c Op. citat. i. 61. d Lectures on Comparative Anatomy, Lond. 1814-1828. See, on the Structure of the Iris, art. Eye, by Dr. Jacob, in Cyclop, of Anat. and Physiol, for June, 1837; Dr. Bolton, in Dunglison's Medical Intelligencer, Dec. 1, 1838; Mackenzie, Practical Treatise on the Diseases of the Eye, 3d edit, by T. Wharton Jones, Lond. 1840; and C. R. Hall, Proceedings ofthe Royal Society, No. 56, Lond. 1843. <= View ofthe Progress of Animal Chemistry, p. 86, Lond. 1813, Fig. 36. 188 SENSE OF SIGHT. some effect in giving colour to the eye; in blue eyes, for instance, the tissue of the iris is nearly white ; the pigmentum nigrum, which appears through it, being the chief cause of its colour. At the point of junction between the ins and the choroid coat, they are united to the sclerotica by a band of cellular substance, called the ciliary ligament; and, from the anterior margin of the choroid, where it unites with the base of the ins, numerous vas- culo-membranous appendages arise, which appear to be prolonga- tions of the anterior margin of the choroid, turning inwards towards the margin of the crys- talline lens, and terminating ab- ruptly, without being attached to that body. They are the ciliary processes. These beau- tiful appendages are from sixty to eighty in number ; and re- semble the disk of a radiated flower. On their posterior sur- face, they are covered by the same kind of pigment as that of the choroid and uvea; and they impart the stain to the mem- branes of the crystalline and vitreous humours. The greatest diversity of opinion, here again, exists regarding both struc- ture and function. By ,some, these processes have been es- teemed nervous; by others, muscular, glandular, and vascular. Sir Everard Home asserts, on the authority of microscopic observations by Mr. Bauer,a that between the processes are bundles of muscular fibres of consider- able length, which originate all around from the capsule of the vitreous humour, pass forward over the edge of the lens, are attached firmly to its capsule, and there terminate. They are unconnected with the ciliary processes, or iris, and he conceives that their contraction will pull the lens towards the retina. In appearance they resemble the choroid, and are probably identical with it in structure. Such is an anatomical view of the physical part of the eye proper, so far as is necessary for the physiological inquirer. We have yet to consider the most important part of the organ; —that which is essentially nervous and vital in its action; and which, as we have seen, goes to constitute one of the membranes of the eyeball — the retina. The optic nerves — the second pair of Willis — arise from the * Op. citat., and Philosoph. Transact, for 1822, p. 78. Fig. 37. Anterior Segment of a Transverse Section of the Olobe ofthe Eye seen from within. 1. Divided edge of the three tunics; sclerotic, choroid (the dark layer), and retina. 2. Pupil. 3. Iris, the surface presented to view in this section being the uvea. 4. Ciliary processes. 5. Scalloped anterior border of the retina. — {Wilson.) ORGAN OF VISION. 189 Fig. 38. anterior part of the corpora quadrigemina,8 and not, as was at one time universally believed, from the thalami nervorum opticorum. Setting out from this point, they proceed forwards to- wards the thalami, to which they adhere; re- ceiving filaments from the corpus genicvlatum ex- ternum, an eminence a little anterior to, and on the outside of, the cor- pora ; and from a layer of cineritious substance, si- tuatebetween thepointof junction of the nerve of each side and the emi- nentiae mammillares — called the tuber cine- reum.b Proceeding for- ward towards the eye, the nerves approach, and form a junction at the sella turcica or on the upper surface ofthe sphe- noid bone. Anterior to this point, they diverge, each passing through the optic foramen to the cor- responding eye ; piercing the sclerotic and choroid at a point about one-tenth of an inch from the axis ofthe eye on the side next the nose, where it has a button-like appearance, and expanding, to form the whole, or a part of the retina (see page 182). When the optic nerve is regarded from the inside, after removing the retina and choroid, it appears in the form of a circular spot, perforated with small holes, from which the medul- lary matter may be expressed. This is the lamina cribrosa of Albums. M. Lassaigne has examined the chemical composition of the optic nerve and retina; and concludes, from his experi- ments, that the retina is formed of the same elements as the cere- bral and nervous substance; differing only in the proportion of the constituents. r It is a question that has often been agitated, whether the optic MrffGaiSS'SaS1 ^ iIlustratinSthisorigin5 byG.Kennion,M.D.,inLond. b Solly, Lond. Med. Gazette, Sept. 24, 1838. Optic Nerves. 1. Upper surface of thalami optici. 2. Middle commis- sureof3d ventricle connecting them. 3. Posterior commis- sure of 3d ventricle. 4. Foramen commune posterius. 5. Corpus geniculatum internum. 6. Corpus geniculatum externum. 7. Corpora quadrigemina. 8. One root of op- tic nerve. 9, The other root. 10. The chiasm or commis- sure. 11. Expansion of the nerve into the retina. 12. Section of the retina, showing its three layers —the exter- nal — ortunica Jacobi; the next the nervous, and the in- ternal the vascular formed by the ramifications of the cen- tral artery of the retina, 13, whichj pierces the optic nerve and runs forward on the centre of the nerve. — (Wilson.) 190 SENSE OF SIGHT. nerves, at their junction on the sella turcica, simply lie alongside each other; or whether they decussate, so that the root of the nerve of the left eye is on the right side; and that of the right on the left. Anatomical investigations have hitherto left the question unsettled, and pathology appears to have furnished proofs on both sides. Thus, where the right eye has been lost for a considerable time, the optic nerve of the same side has been found in a state of atrophy through its whole extent. In other cases of the kind, the posterior portion of the left nerve has been found in this condition.3 Fishes have the nerve arising from one side of the brain, and pass- ing to the eye of the other side; hence crossing, but not uniting. On the other hand, Vesaliusb gives a plate of a case in which he found the optic nerves passing to the eyes of the same side from which they originate without touching at all; and yet without any disturbance of vision. It is not necessary, however, to adduce the numerous cases that have been published in favour ofthe one view or the other. It is impossible to sift those that are entitled to implicit confidence from those that are not. We may merely remark, that certain observations of Valsalva, Cheselden,c and Petitd appear to show, that where the brain is injured, it is the eye of the opposite side that is affected; and, in cases of hemiplegia or paralysis of one side of the body, we certainly have too many instances for testing the accuracy of this opinion. Sbmmeringe — whose correctness as an observing anatomist has never been disputed—affirms, that he had an opportunity of examining seven blind persons, in all of whom the atrophy of the nerve was on the side or root opposite to the eye affected.f Some, again, have advanced an opinion, that the decussation is partial, and concerns only the internal filaments; that the other filaments pass directly on to half the corresponding eye; so that one-half of each eye is supplied by straight fibres proceeding directly from the root of the same side; the other half by those resulting from the decussation of the internal fibres. Messrs. Wollaston,? Berard, Pravaz,h Gall and Spurzheim, Cuvier, Serres, Vicq-d'Azyr, Caldani, Ackermann, the brothers Wenzel; G. R. Treviranus; J. Miiller, and others,1 embrace this opinion for the purpose of explaining the anomaly of vision called hemiopia, in which only one-half the object is seen. Cuvier, Serres, and Caldani also assert, that the}' have noticed the above arrange- a Rudolphi, Grundriss der Physiologie, B. ii. Abth. 1, s. 203. b De Corp. Human. Fabric, lib. iv. c. 4. c Anatomy ofthe Human Body, 13th edit. Lond. 1792. * Memoir, de l'Acad. 1723 and 1728. e Blumenbach, Med. Bibl. ii. 2. s. 368 ; and De Decussatione Nervorum Opticorum. Mogunt. 1786. f See a case elucidative of this point in Lallemand, Sur les Pertes Seminales, or in Dr. Wood's Translation in Dunglison's American Med. Library for 1839, p. 30. s Philosophical Transact. 1824, p. 222. h Archives Generates de M6decine, Paris, 1825, Mai, p. 59. i Hildebrandt's Handbuch der Anatomie, von E. H. Weber, Band. iii. s. 438, Braunschweig, 1832 ; Blumenbach op. citat.; Sir D. Brewster's Natural Magic, Amer. Edit. p. 36, New York, 1833 ; and Pouillet, Elevens de Physique, iii. 338, Paris, 1832. ORGAN OF VISION. 191 ment in the nerves of the horse, when subjected to appropriate maceration. More recently,Mr. H.Mayo8 has stated, that the optic nerve consists in man of three tracts; the innermost of which is wholly a commissure, connecting the two retinae anteriorly, and the optic ganglia posteriorly. The middle tract decussates, and is considered by Mr. Mayo to supply the part of the retina which lies on the inner side of each eyeball, between its anterior border and the entrance of the optic nerve. The external tract, he affirms, does not decussate, but passes on to supply the outer portion of the retina of the same side. Hence the right optic nerve, in Mr. Mayo's view, supplies the right side of each eyeball, and the left the left. Dr. Wollaston himself was affected with hemiopia; and in his case, the loss of vision was sometimes on one side, and sometimes on the other, and he thought, that the phenomena might be ex- plained by the decussation of the optic nerves ; but Messrs. Sollyb and Mayo have known instances of a like affection involving alter- nately the centre and circumference of the retina, and therefore not attributable to any such structural arrangement. These views are opposed, however, by the direct experiments of Magendie.0 He divided, in a rabbit, the right optic nerve, behind the point of decussation, or what has been called the chiasma of the nerves;—the sight of the left eye was destroyed. On cutting the left root, the sight of the right eye was equally destroyed; and on dividing the bond of union, in another rabbit, by a longitudinal incision, made between the nerves, vision was entirely abolished in both eyes ; — a result, which, as he properly remarks, proves not only the existence of decussation, but, also, that it is total, and not par- tial as Wollaston had supposed. . Another experiment, which he instituted, led to a similar result. Fifteen days before examining a pigeon he destroyed one eye. The nerve of the same side, as far as the chiasma, was wasted ; and, behind the chiasma, the root of the opposite side. Rolando and Flourens,d too, found in their experiments, that when one cerebral hemisphere was removed, the sight of the opposite eye was lost. We may conclude, then, in the present state of our knowledge, that there is not simply a junction, or what the French call adossement, of the optic nerves; but that they decussate at the sella turcica.e The eye proper receives numerous vessels, — the ciliary arteries and veins — and several nervous ramifications, the greater part of which proceed from the ophthalmic ganglion ofthe fifth pair. The following are the dimensions, &c, of the organ, on the authority of Petit, Young, Gordon, and Brewster. i London Medical Gazette, Nov. 5, 1841. b The Human Brain, its Configuration, &c, p. 263, Lond. 1836 ; and Carpenter's Human Physiology, Amer. Edit. p. 246, Philada. 1843. e Precis, &c. edit. cit. i. 64. * Recherches Experimentales sur le Systeme Nerveux, 2d edit. Paris, 1842. e See, on this subject, Adelon, Physiologie de l'Homme, i. 402, 2de edit. Paris, 1829, and Bostock's Physiology, edit. cit. p. 709. 192 SENSE OF SIGHT. Eng. Inch. Length of the antero-posterior diameter of the eye - - - - 0*91 Vertical chord of the cornea...... ""™ Versed sine of the cornea.........~'* * Horizontal chord of the cornea......" " ^l Size of pupil seen through the cornea - - - - - OvS/to u-id Size of pupil diminished by magnifying power of cornea to - - 0-^5 to U-U Radius of the anterior surface of the crystalline.....0-30 Radius of posterior surface...... y/** Principal focal distance of lens......- - 1-73 Distance of the centre of the optic nerve from the foramen centrale of Sommering..........®* jj- Distance of the iris from the cornea .......°'10 Distance of the iris from the anterior surface of the crystalline -^ - 0-02 Field of vision above a horizontal line - 50°£ 120° Field of vision below a horizontal line - - - - 70o"^ Field of vision in a horizontal plane .... 150 Diameter of the crystalline in a woman above fifty years of age - - 0-378 Diameter of the cornea --------- 0-400 Thickness of the crystalline........°'172 Thickness of the cornea --------- 0-042 It is proper to remark, that all these measurements were neces- sarily taken on the dead organ, when the parts are by no means in the same relative situation as when alive ; and this is a cause why many of the phenomena of vision can never be determined with mathematical accuracy. 3. ACCESSORY ORGANS. The visual organs, being of an extremely delicate texture, it was of obvious importance, that they should be guarded against deranging influences. They are accordingly provided with nu- merous parts, which afford them protection, and enable them to execute the functions for which they are destined. They are, in the first place, securely lodged in the bony cavities called the orbits, which are of a conical figure, with the apices directed inwards. In the truncated apex the foramen oplicum is situate, by which the optic nerve enters the orbit. Here are, also, the superior orbitar aud spheno-maxillary fissures, through which many vessels and nerves proceed to the eye and its appendages. The base of the orbits is not directly opposite the apices, but tends outwards; so that the axes of these cavities, forming an angle of about 90° with each other, if prolonged, would meet at the sella turcica. The eye, however, is not placed in the direction of the axis ofthe orbit, but straight forward ; and as it is nearly spherical, it is obvious that it cannot completely fill the conical cavity. In Fig. 39, the muscles 9 and 13 indicate the shape ofthe upper and lower surfaces of these cavities ; —the whole ofthe space, between the posterior part of the orbit and these muscles, which is not occupied by the optic nerve, being possessed by an adipous, cellular tissue, on which the eye is placed, as it were on a cushion. Under particular mor- a According to Young, Philos. Transact. P. i. p. 46, Lond. 1801, the field of vision internally is 60°, externally 90° ; according to Purkinje, (Rust's Magazine, B. xx. Berlin, 1825,) internally 60°, externally 100°. ACCESSORY ORGANS OF VISION. 193 bid circumstances, this deposit becomes greatly augmented, so as to cause the eye to start from its socket; constituting the disease called exophthalmos. The parts, however, that are more immediately reckoned amongst the protectors ofthe organ — the tutamina oculi — are the eyebrows, eyelids, and the lachrymal apparatus. The eyebrows or supercilia are situate immediately on the superciliary ridge of the frontal bone. They consist of hair, varying in colour according to the individual, and turned towards the outer angle of the eye; of common integument; of sebaceous follicles, situate at the root of each hair ; and of muscles to move them, — namely, the frontal portion of the occipito-frontalis, the upper edge of the orbicularis palpebrarum, and the corrugator supercilii. Thepalpebrae or eye- lids are, in man, two in number, an upper and a lower, or a greater and a less — the palpebra major vel superior, and the palpebra minor vel inferior —- the former covering three-fourths of the eye ; hence the transverse diameter of the eye is not represented by their union, the latter being much below it, and therefore improperly termed, by Haller, AZquator oculi. By the separation of the eye- lids, we judge, but inaccurately, of the size ofthe eye — one, who is capable of separating them more largely from each other, appear- ing to us to have a larger eye, — and conversely. The edge of the eyelids is thick, rounded, and furnished with hairs, resembling generally, in colour, those of the head. These are the eyelashes or cilia. On the upper eyelid they are curved upwards; on the lower downwards. The eyelids are formed of four membranous layers, in superposition ; and of a fibro-cartilage, which extends along the whole of the edge and keeps them tense. The outermost of these layers is the common integument, the skin of which is very delicate and semitransparent, yielding readily to the motions of the eyelids, and having numerous transverse folds. The cellular tissue, beneath the skin, is very loose, and, under particular circumstances, is infiltrated by a serous fluid, giving the eyelids, especially the lower, a dark appearance : but it never con- tains fat. Beneath the common integument is the muscular stratum, formed by the orbicularis palpebrarum, in the lower eyelid; in the upper, by the same muscle, and the levator palpebrae superioris, (Fig. 39,) which arises from above the foramen opti- cum, and is inserted into the superior edge of the fibro-cartilage of the tarsus. Beneath the orbicularis palpebrarum, again, there is a fibrous layer, which occupies the whole of the eyelids, passing from the edge of the orbit to the tarsal margin, and seems intended to limit the motion of the eyelids, when they approximate each other. The last layer, and that which forms the posterior surface of the eyelids, is a fine, delicate, transparent, mucous membrane, called tunica conjunctiva or tunica adnata ; so named because it joins the eyelids to the globe of the eye. It lines, in fact, the eyelids, and is reflected over the ball; but it has been a matter of contention, whether it passes over the transparent cornea. The vol. i.— 17 194 SENSE OF SIGHT. generality of anatomists say it does ; Ribes,a however, maintains the opinion, that it extends only as far as the circumference of the cornea, and that the cornea itself is covered by a proper membrane. Physiologically, this dispute is of no moment. At its outer sur- face, a humour is constantly exhaled, which keeps it moist, and facilitates the motions of the eyelids over the eyeball. Its loose state also favours these motions. Both eyelids are kept tense by the aid of a fibro-cartilage, situate along the edge of each, and called tarsus. That of the upper eyelid is much more extensive than that of the lower; and both seem as if cut obliquely, at the expense of their inner surface; so that, in the opinion of most anatomists, when the eyelids are brought together, a triangular canal is formed between them and the ball of the eye, which has been conceived useful in conducting the tears towards the lachrymal puncta. Magendieb denies that any such canal exists ; and there seems but little evidence of it, when we examine how the tarsal cartilages come in contact. Such a canal, destined for the purposes mentioned, would, indeed, seem superfluous. Besides the eye- lashes, certain compound follicles, called Meibomian, are situate in the substance of the tarsal cartilages. These are thirty or forty in number in the upper eyelid, and twenty-five or thirty in the lower. They are in particular furrows between the tarsal fibro- cartilages and the conjunctiva, and secrete a sebaceous fluid, called by the French chassie, in the dry state ; by the Germans Aug en butter, (" eyebutter"), and by us, gum of the eye, Which serves the purposes of the follicular secretions in general. The arrangement of the eye- lids differs in different animals. In several, both eyelids move; but, mothers,only one; either the lower rising to join the up- per, or the upper descending to meet the lower. In the sun- fish — tetraodon mola — the eyelid is single and circular, with a perforation in the cen- tre, which can be contracted or enlarged, according to cir- cumstances. In many animals, again, there is a third eyelid, called the nictitating mem- brane, which is of a more de- licate texture and more largely supplied with bloodvessels; and in some animals is trans- parent. In birds it exists, is well seen in the owl. It is at the inner angle of the a Memoires de la Societe Medicale d'Emulation, vol. vii., Paris, 1817 b Precis Elementaire, i. 52. Fig. 39. Muscles of the Eyeball. 1. A small fragment ofthe sphenoid bone around entrance of optic nerve into orbit. 2. Opticnerve. 3. Globe of eye. 4. Levator palpebra? muscle. ■3. Superior oblique muscle. 6. Its cartilaginous pulley. 7. Its reflected tendon. 8. Inferior ob- lique muscle, the small square knob at its com- mencement is a piece of its bony origin broken off. 9. Superior rectus, 10. Internal rectus almost concealed by optic nerve. 11. Part of external rectus, showing its two heads of orisin. 12. Ex- tremity of external rectus at its insertion ; the intermediate portion of muscle having been re- moved. 13. Inferior rectus. 14. Tunica albuginea formed by expansion of tendons of four recti. ACCESSORY ORGAN OF VISION. 195 eye, and is capable of being drawn over the ball like a curtain, by two particular muscles, and of thus freeing the surface ofthe eye from extraneous substances. In man, it is only a vestige, destined to no apparent use. It is called valvula ox plica semilunaris. The eye has its proper muscles, capable of moving it in various directions. Their arrangement is readily understood. They are six in number: — four recti or straight muscles, and two oblique. 1. The rectus superior or levator. 2. The rectus inferior or depressor. 3. The rectus externus or adductor ; and 4. The rectus externus or abductor. They all arise from the base of the orbit, around the optic foramen ; pass forward to vanish on the sclerotica; and, according to some anatomists, extend over, and form a layer to, the cornea. The oblique muscles are— 1. The greater oblique, obliquus superior, patheticus or trochlearis, which arises from the inner side of the foramen opticum, passes forwards to the internal or- bitar process of the frontal bone, where its tendon is reflected over a pulley or trochlea, and crosses the orbit to be inserted into the upper, posterior, and outer part of the globe of the eye. 2. The lesser oblique or obliquus inferior, whose fibres arise from the anterior and inner part ofthe floor ofthe orbit, near the lachrymal groove, pass under the eyeball, and are inserted between the entrance of the optic nerve and insertion of the abductor oculi, and opposite the insertion of the obliquus superior. These muscles have their proper nerves. The third pair — motores oculorum — or com- mon oculo-muscular, are distributed to all the muscles except the trochlearis and abductor ; the fourth pair ox pathetic ox internal oculo-muscular, to the trochlearis singly ; and the sixth pair or external oculo-muscular, to the abductor. Lastly, the office of tutamina oculi is not wholly engrossed by the parts, that have been men- tioned. The apparatus for the secretion of the tears participates in it, by furnishing a fluid, which lubricates the surface of the eye, and keeps it in the necessary de- gree of humidity for the proper performance of its functions. It is a beautiful,and ingenious little apparatus, the structure of which can easily be made intelligible. It consists of the lachrymal gland, the excretory ducts of the gland, the caruncula lachrymalis, the lachrymal ducts, and the nasal duct; in other words, of two sets of parts — one, forming the fluid and pouring it on the anterior Fig. 40. Lachrymal Apparatus: abed. Lachrymal ducts. a a. Puncta lachrymalia. efg hi. Nasal duct. k I. Lachrymal gland. surface of the eye ; the other comprising the organs for its excre- 196 SENSE OF SIGHT. tion. The lachrymal gland is situate in a small fossa or depres- sion at the upper, anterior, and outer part of the orbit. It is an oval body of the size of a small almond ; of a grayish colour, and composed of small, whitish, granular bodies collected into lobes. From these, six or seven excretory ducts arise, which run nearly pa- rallel to each other and open on the inner side of the upper eyelid, near the outer angle of the eye and near the tarsal cartilage. Through these ducts, the tears, secreted by the lachrymal gland, are spread over the tunica conjunctiva. The tears are composed, according to Fourcroy and Vauquelin,a of water, mucus, chloride of sodium, soda, phosphate of lime, and phosphate of soda ; and their taste is mani- festly saltish, although the saline ingredients are described as not exceeding a hundredth part of the whole. They are not secreted by those animals that live in the water. At the inner angle of the eye is the caruncula lachrymalis. It is a collection of small mucous follicles, which secrete a thick, whitish humour, to fulfil a similar office wTith the secretion of the meibo- mian follicles. It completes the circle formed by those follicles around the eyelids. The rosy or pale colour of this body is supposed to indicate strength or debility. This it does, like other vascular parts of the system, and in a precisely similar man- ner. The puncta lachrymalia axe two small orifices, situate near the inner angle of the eye ; the one in the upper, the other in the lower eyelid, at the part where the eyelids quit the globe to pass round the caruncula lachrymalis. They are continually open, and directed towards the eye. Each punctum is the commencement of a lachrymal duct, which passes towards the nose in the sub- stance of the eyelids, between the orbicularis palpebrarum and the tunica conjunctiva. These open, as represented in Fig. 40, into the lachrymal sac, which is nothing more than the commencement of the nasal duct ox ductus ad nasum. The bony canal is formed by the anterior half of the os unguis, and by the superior maxillary bone, and opens into the nose behind the os spongiosum inferius. Through these excretory ducts, all of which are lined by a prolon- gation of the mucous membrane, the tears pass into the nasal fossae. Dr. Horner,b the able professor of anatomy in the University of Pennsylvania, has best described a small muscle, which is evi- dently a part of the lachrymal apparatus, and to which he gives the name tensor tarsi. It is on the orbital face of the lachrymal sac; arises from the superior posterior part of the os unguis ; and, after having advanced a quarter of an inch, bifurcates; one fork being inserted along each lachrymal duct, and terminating at or near the punctum. It is probable, that the function of this muscle is to keep the punctum properly directed towards the eyeball, or, as Dr. Physick has suggested, to keep the lids in contact with the globe. The office, assigned to it by Dr. Horner, of enlarging, a Journal de Physique, xxxix. 256. b Lessons in Practical, Anatomy, 3d edit. p. 116, Philad. 1836; and General Ana- tomy and Histology, 6th edit. ii. 425, Philad. 1843. See, also, Rosenmuller's Hand- buch der Anatomie, dritte Auflage, Leipz. 1819. PHYSIOLOGY OF VISION. 197 by its contraction, the cavity of the lachrymal sac, and thus pro- ducing a tendency to a vacuum, which vacuum can be more readily filled through the puncta than through the nose, owing to the valves or folds of the internal membrane of the sac — is ingenious, but apocryphal. The tensor tarsi muscle is now commonly asso- ciated with the name of Dr. Horner.a 4. PHYSIOLOGY OP VISION. The preceding anatomical sketch will enable the reader to com- prehend this important organ in action. In describing the office executed by its various components, we shall follow the order there observed, premising some general considerations on the mechanism of vision; and afterwards depict the protecting and modifying in- fluences exerted by the various accessory parts : — the different phenomena of vision will next be explained, and lastly, the infor- mation conveyed to the mind by this sense. In tracing the progress of luminous rays through the purely phy- sical part ofthe organ, we shall, in the first instance, suppose* a sin- gle cone to proceed from a radiant point in the direction of the axis of the eye; or, in other words, of the antero-posterior diameter of the organ, B b. Fig. 41. It is obvious, that the rays, which fall upon the transparent cor- nea can alone be inservient to vision. Those, that impinge upon the sclerotica, are reflected ; as well as a part of those that fall upon the cornea, giving occasion, in the latter case, to the ima?e ob- served in the eye, and to the brilliancy ofthe organ. Nor does the whole of the cornea admit the rays, for it is commonly more or less covered above and below, by the free edge of the eyelids. Again, the whole ofthe light, that enters the cornea, does not impinge upon the retina. A portion falls upon the iris, and is reflected back to the eye, in such manner as to give us the notion of the colour of the organ. It is, consequently, the light, which passes through the pupil, that can alone attain the retina. 1 T. W. Jones, art. Lachrymal Organs, Cyclop, of Anat. and Physiol., July, 1840. 198 SENSE OF SIGHT. Some interesting points of diagnosis are connected with the re- flection which takes place from the humours of the eye. If a lighted candle be held before an eye, the pupil of which has been dilated by belladonna, and in which there is no obscurity in the humours or their capsules, three distinct images of the flame are perceptible — two upright and one inverted— one of the former reflected from the cornea, and the other from the anterior part of the crystalline; the third inverted image being caused by the re- flection from the posterior concave surface of the crystalline. M. Sanson has proposed this catoptric method of examining the eye as a means of diagnosis between cataract and amaurosis, —- in the latter all the images being seen : and experience has shown it to be a valuable mode of investigating various conditions of the eye, which might not be readily understood without its agency. If we suppose aluminous cone to proceed from a radiant point B, Fig. 40, directly in the prolongation of the antero-posterior di- ameter of the eye, the axis of this cone will also be the axis of the organ ; so that a ray of light, impinging upon the humours in the direction of this axis, will, as in the case of the lenses previously referred to, pass through the humours without undergoing deflection, and will fall upon the retina at b. This, however, is not the case with the other rays composing the cone. They do not fall perpen- dicularly upon the cornea, and are, consequently, variously refracted in their passage through the cornea, aqueous humour, crystalline, and vitreous humour; but so that they join their axis in a focus at the point where it strikes the retina. The transparent parts ofthe eye, as has been seen, are of different densities, and are consequently possessed of different refractive powers. These powers it has been attempted to estimate; and the following is the result ofthe somewhat discordant evaluations of different experimenters : the power of air being 1-000295. Hawksbee, -Jurin, - -Rochon, Young, - -Chossat, Brewster, - Cornea. Aqueous Humour. CRYSTALLINE LENS. i Vitreous Humour. Capsule. Outer Layers. Centre. 1-393 1-3990 Mean. 1-339 1-33595 1-3333 1-329 1-3333 1-338 1-3366 1-339 1-3767 1-338 1-384 1-3839 1-33595 1-332 1-339 1 1-3394 A ray of light, impinging obliquely on the surface of the trans- parent cornea, passes from a rarer to a denser medium. It will, con- sequently, be refracted towards the perpendicular raised from the point of impact. It will, from this cause, as well as from the con- vexity of the cornea, be rendered more convergent; or, in other words, will approach the axis of the cone. In proceeding through the aqueous humour, little variation will be produced, PHYSIOLOGY OF VISION. 199 as the densities of it and the cornea differ but little : the latter is slightly more refractive, according to the table, and therefore the tendency, that exists, will be to render the ray less convergent. This convergence gives occasion to the entrance of a greater number of rays through the pupil, and necessarily adds to the intensity of the light that impinges on the crystalline. Pursuing the ray through the two chambers of the eye, we find it next impinging on the surface of the crystalline, which possesses a much higher refractive power than the cornea or aqueous humour; in the ratio of 1-384 to 1*336. From this cause, and from the con- vexity of the anterior surface of the lens, the ray is rendered still more convergent or approaches still more the axis of the cone. It is probable, however, that even here some of the light is reflected back, and goes towards the formation of the image in the eye, and the brilliancy of the organ; other reflected rays perhaps impinge upon the pigmentum nigrum lining the posterior surface of the iris, and are absorbed by it. From the crystalline the ray emerges into a medium possessing less refractive power; and, therefore, is deflected from the perpendicular. The shape, however, of the posterior surface of the lens so modifies the perpendiculars, as to occasion such a degree of convergence, that the oblique ray meets the axis at a focus on the retina. (See Figs. 24 and 40.) In this manner two cones are formed; the one having its apex at the radiant point, and its base on the cornea—the objective cone, — the other having its apex on the retina, and termed the ocular cone. These remarks apply chiefly to the cone proceeding in the di- rection of the axis of the different humours, from a single radiant point. It is easy to understand, that every portion of the object ABC, Fig. 40, must be a radiant point, and project so many cones in an analogous manner, which, by impinging upon the retina, form a picture of the object upon that expansion, at g b h. It is important, however, to observe that the rays proceeding from the upper part of the object fall, after refraction, upon the lower part of the retina ; and those from the lower part of the object upon the upper; so that the picture or representation of the object on the retina is inverted. How the idea of an erect object is excited in the mind will be the subject of after inquiry. When rays, as A g and C h, fall obliquely on a lens, and pass through the centre of the lens, they suffer refraction at each of its surfaces, but as the two refractions are equal and in oppo- site directions, the rays may be esteemed to pursue their course in a straight line. The point a, at which these various rays cross, is called the optic centre of the crystalline. Each of these straight rays, proceeding from a radiant point, may be assumed as the axis of all the rays proceeding obliquely from the same point, and the common focus must fall on some part of this axis. In this way the object is represented, in miniature and inverted, on the retina. As, however, the oblique ray has to pass through the cornea and aqueous humour, before it impinges on the crystalline, it under- 200 SENSE OF SIGHT. goes considerable deflection, and consequently it is not accurate to represent it as pursuing a straight course through the different humours, in its way to the retina. The main deflection—as in the case of the rays D t s, and E t r, Fig. 40 — occurs at the entrance of the rays into the cornea. That an inverted representation of external objects is formed within the eye is in accordance with sound theory, and is sup- ported not only by indirect, but by direct experiment. If a double convex lens be fitted into an opening made in the window-shutter of a darkened chamber, luminous cones will proceed from the dif- ferent objects on the outside ofthe house, and will converge within; so that if they be received on a sheet of paper, a beautiful and distinct image of the object will be apparent. This is the well* known instrument, the camera obscura (Fig. 42), of which the organ of sight may be regarded as a modification. Making ab- straction, indeed, of the cornea, and of the aqueous and vitreous humours, the representation of the eye in Fig. 40, with the object, ABC and its image on the retina, is the common camera obscura. The eye is, therefore, more complicated and more perfect than this simple instrument; the cornea with the aqueous and vitreous hu- mours being added for the purpose of concentrating the light on the retina; the latter, in addition, affording a large space for the expansion of the retina, and preventing the organ from collapsing. In the operation for cataract by extraction, which consists in re- moving the lens through an opening, made in the lower part ofthe cornea, the aqueous humour escapes, but is subsequently regene- rated. If, however, too much pressure be exerted on the ball, to force the crystalline through the pupil and the opening in the cor- nea, the vitreous humour is sometimes pressed out, when the eye collapses and is irretrievably lost. Fig. 42. Experiments have also been instituted on this subject, the results of which are even more satisfactory than the facts just mentioned. These have been of different kinds. Some experimenters have formed artificial eyes of glass, to represent the cornea and crystal- PHYSIOLOGY OF VISION. 201 line, with water in place of the aqueous and vitreous humours. Another mode has been to place the eye of an ox or a sheep in a hole in the shutter of a dark chamber, having previously removed the posterior part of the sclerotica, so as to permit the images of ob- jects on the retina to be distinctly seen. Malpighi and Haller em- ployed a more easy method. They selected the eyes of the rabbit, pigeon, puppy, &c, the choroid of which is nearly transparent; and, directing the cornea towards luminous objects, they saw them distinctly depicted on the retina. More recently, Magendie3 has repeated these experiments by employing the eyes of albino ani- mals, as those of the white rabbit, the white pigeon, the white mouse, &c, which afford great facilities for accomplishing the ex- periment, — the sclerotica being thin, and almost transparent; the choroid, also, thin, and when the blood, which gives it colour, has disappeared after the death of the animal, offering no sensible ob- stacle to the passage of light. In every one of these experiments, external objects were found to be represented on the natural and the artificial retina in an inverted position; the image being clearly defined, and with all the colours of the original. Yet how minute must these representations be in the living eye ; and how accurate the mental appreciation, seeing that each impression from myriads of luminous points is transmitted by the retina to the encephalon, and perceived with unerring certainty ! In the prosecution of his experiments —in some of which he was assisted by M. Biot — Magendie found, as might have been expect- ed, that any alteration in the relative proportion or situation of the different humours had a manifest effect upon vision. When a minute opening was made in the transparent cornea, and a small quantity of the aqueous humour permitted to escape, the image had no longer the same distinctness. The same thing occurred when a little of the vitreous humour was discharged by a small incision made through the sclerotica. He farther found that the size of the image on the retina was proportionate to the distance of the object from the eye. When the whole of the aqueous humour was evacuated, the image seemed to occupy a greater space on the retina, and to be less distinct and luminous, and the removal of the cornea was attended with similar results. When the crystalline was either depressed or extracted, as in the opera- tion for cataract, the image was still formed at the bottom of the eye; but it was badly defined, slightly illuminated, and at least four times the usual size. Lastly, — when the cornea, aqueous humour, and crystalline were removed, leaving only the capsule of the crystalline, and the vitreous humour, an image'was no longer formed upon the retina ; the light from the luminous body reached it, but it assumed no shape similar to that of the body from which it emanated. Most of these results — as Magendieb remarks — accord very well with the theory of vision. Not so, the distinctness of the a Precis Elementaire, i. 70. b Ibid. i. 73. 202 SENSE OF SIGHT. image under these deranging circumstances. According to the commonly received notions on this subject, it is necessary, in order to have the object depicted with distinctness on the retina, that the eye should accommodate itself to the distance at which the object is placed. This is a subject, however, that will be discussed pre- sently. Such are the general considerations relating to the progress of luminous rays from an object through the dioptrical part of the organ of sight to the nervous portion — the retina. We shall now inquire into the offices executed by the separate parts, that enter into its composition, where they have not already engaged attention. We have shown, that the cornea, aqueous humour, crystalline, and vitreous humour, are a series of refractive bodies, to concen- trate the luminous rays on the retina; to keep the parietes of the eye distended, and to afford surface for the expansion ofthe retina;— thus enlarging the field of vision. It is probably owing to their different refractive powers, that the eye is achromatic; or, in other words, that the rays, impinging upon the retina, are not decom- posed into their constituent colours, — an inconvenience which appertains to the common lens. (Fig. 27.) The eye is strictly achromatic; and it has been an object of earnest inquiry amongst philosophers, to determine how the aberration of refrangibility is corrected in it. Euler,a first perhaps, asserted, that this is owing to the different refractive powers ofthe humours; and he conceived, that, by imitating this structure in the fabrication of lenses, they might be rendered achromatic. Experience has shown the accu- racy of this opinion. (Fig. 28.) Others have believed that the effect is produced by certain of the humours — as the aqueous and the vitreous — which they have considered capable of correcting the dispersion produced by the cornea and crystalline. Others, again, have placed it in the crystalline, the layers of which being of dif- ferent dispersive powers might correct each other. Lastly, — some have denied altogether the necessity for the eye's being achromatic; asserting, that the depth of the organ is so inconsider- able, that the dispersion of the rays, by the time they reach the retina, ought to be inappreciable. Such was the opinion of D'Alembert. Maskelyneb calculated the amount of the aberra- tion, that must necessarily take place in the eye, and concluded that it would be fourteen or fifteen times less than in a common refracting telescope, and therefore imperceptible. Uncertainty still rests on this subject; and it cannot be removed until the dis- persive and refractive powers of the transparent parts of the organ shall have been mathematically determined ; as well as their exact curvatures. It has been already shown, that the data we possess on this subject from different observers are sufficiently imprecise. Our knowledge, then, is restricted to the fact3 that the eye is * Memoir. Berlin, pour 1747, p. 279 ; and Letters of Euler, by Sir D. Brewster, Amer. Edit. i. 163, New York, 1833. b Philosoph. Transactions for 1789, lxix. 256. PHYSIOLOGY OF THE COATS OF THE EYE. 203 perfectly achromatic, and that, in this respect, it exceeds any instrument of human construction. The views of Euler are the most probable; and the effect doubtless is much aided by the iris or diaphragm, which prevents the rays from falling upon the mar- gins of the lens, where, by the surfaces meeting at an angle, the aberration must necessarily be greatest. Of the coats of the eye, —the sclerotic, as has been remarked, gives form to, and protects the organ. The choroid is chiefly useful by the black pigment, which lines and penetrates it. It will be seen, indeed, that some individuals, on insufficient grounds, have esteemed it the seat of vision. Leaving this question for the moment, and granting, as we shall endeavour to establish, that the impression is received upon the expansion of the optic nerve —the retina, — the use of the choroid would seem to be, in ordinary circumstances, to afford surface for the pigmen- tum nigrum, whose function it is to absorb the rays after they have passed through the retina, and thus to obviate the confusion that would arise from varied reflections, were the choroid devoid of such dark covering. In albinos or white animals, in which the pigment is wanting, this inconvenience is really experienced, so that they become nyctalopes, or at least see but imperfectly during the day. In the night, however, or when the light is feeble, their vision is unimpaired; and hence the albinos of our species have been called by the Germans and Dutch, Kakerlaken, or cockroaches. Sir Everard Home8 is of opinion, that the pigmen- tum nigrum of the eye is provided as a defence against strong light, and that hence it is lightest in those countries least exposed to the scorching effects of the sun. In confirmation of this, he remarks, that it is dark in the monkey, and in all animals that look up- wards, and in all birds exposed to the sun's rays; whilst the owl, that never sees the sun, has no black pigment. It doubtless pos- sesses the function assigned to it by Sir Everard. The use of the shining spot on the outside of the optic nerves, in the eyes of quadrupeds, called the tapetum, has been an inte- resting theme of speculation, and has given rise to much ingenious, and to not a little ridiculous, hypothesis amongst naturalists. The absence of the black pigment necessarily occasions the reflection of a portion of the rays from the membrana Ruyschiana ; and it has been presumed, that these reflected rays, in their passage back through the retina, may cause a double impression, and thus add to the intensity of vision. Another view has been, that the re- flected" rays may pass outwards through the retina without ex- citing any action, to be thrown on the object in order to increase the distinctness of the image on the retina, by an increase of its light. Dr. Fleming,b who usually exhibits much philosophical acumen, and physiological accuracy, thinks it not probable, that both surfaces of the retina are equally adapted for receiving im- » Lectures on Comparative Anatomy, iii. 220, Lond. 1823, b Philosophy of Zoology, i. 192, Edinb. 1822. 204 SENSE OF SIGHT. pressions of external objects, and is of opinion that the rays, in their passage inwards, alone produce the image. More recently, however, M. Desmoulinsa has adduced many facts and arguments to show, that the tapetum really does act the part of a mirror, and, by returning the rays through the retina, subjects it to a double contact. He affirms, that in nocturnal animals, and in many fishes and birds, which require certain advantages to compensate for the conditions of the media in which they are situate, the tapetum is of great extent, and always corresponds to the polar segment of the eyeball, or to the visual axis; that in many animals, as in the cat, the pigmentum nigrum is wholly wanting; and that it is only necessary for the vision of diurnal animals. He farther remarks, that, in man, the pigment diminishes according to age ; and that in advanced life it becomes white; and he ingeniously presumes, that this is a means employed by nature to compensate, in some measure, for the gradual diminution in the sensibility of the retina, — the choroid beneath reflecting more and more of the rays, ac- cording as the pigment is removed from its surface. The views of M. Desmoulins are the most satisfactory of any that have been propounded, and they are corroborated by the experiments of Gruithuisen, Esser, and Tiedemann,b which show, that the phe- nomenon never occurs when the light is totally excluded. Gruit- huisen observed it in the dead as well as in the living animal. Tiedemann perceived it in a cat, which had been decapitated for twenty hours, and it did not cease until the humours had become turbid. The views of these observers impress us the more forcibly, when we compare them with some other fanciful speculations, such as that of M. Richerand,0 who supposes, that the use of the tapetum is to cause animals to have an exaggerated opinion of man ! As if the same exaggerated effect would not be produced whatever were the object that impressed the organ. The iris has been compared, more than once, to the diaphragm of a lens or telescope. Its function consequently must be, — to correct the aberration of sphericity, which would otherwise take place. This it does by diminishing the surface of the lens on which the rays impinge, so that they may meet at the same focus on the retina. Biot has remarked, that this diaphragm is situate in the eye precisely at the place where it can best fulfil the office, and yet admit the greatest possible quantity of light. The iris is capable of contracting or dilating, so as to contract or dilate the pupil. It has been already observed, that the views of anatomists, regarding the muscular structure of the iris, have been very discrepant, and that some esteem it to be essentially vascular and nervous, the vessels and nerves being distributed on an erec- tile tissue. The partisans of each opinion explain the motions of a Magendie's Journal de Physiologie, iv. 89. b Traite Complet de Physiologie de l'Homme, &c, traduit par A. J. L. Jourdan, p. 550. « Adelon, Physiologie de l'Homme, 2de edit. i. 443 ; and Sir E. Home's Lectures on Comp. Anat. iii. 243. ACTION OF THE IRIS. 205 the iris differently. They who admit it to consist of muscular fibres affirm, that the pupil is contracted by the action of the circu- lar fibres, and dilated by that of the radiated. Those, again, that deny the muscularity of the organ say, that contraction of the pupil is caused by the afflux of blood into the vessels, or by a sort of turgescence similar to what occurs in erectile parts in general, and dilatation by the withdrawal of the surplus fluid. Admitting, (and we think this must be conceded,) that the iris is really muscular, we meet with the singular anomaly in its physio- logy— that no ordinary stimulus, applied directly to it, has any effect in exciting it to contraction. It may be pricked with the point of a cataract needle without the slightest motion being ex- cited ; and, from the experiments of Fontanaa and Caldani,b it seems equally insensible, when luminous rays are made to impinge upon it; yet MM. Fowler, Rinhold, and Nysten,c have proved, that it contracts like other muscular parts, on the application of the galvanic stimulus. Like them, too, it is under the nervous influ- ence, its movements being generally involuntary; but, there is some reason to believe, occasionally voluntary. Dr. Roget asserts, that this is the case with his own eye.d In the parrot, and in cer- tain nocturnal birds, its motions are manifestly influenced by voli- tion ;e and, when the cat is roused to attention, the pupil dilates, so as to allow a greater quantity of light to reach the retina. Magendief affirms, that the attention and effort, required to see minute objects distinctly, occasion contraction of the human pupil. He selected an individual whose pupil was very moveable ; and placing a sheet of paper in a fixed direction, as regarded the eye and the light, he marked the state of the pupil. He then directed the person to endeavour, without moving the head or eyes, to read very minute characters traced on the paper. The pupil immedi- ately contracted, and continued so, as long as the effort was main- tained. Many experiments have been made to discover the nerve, which presides over the movements of the iris. These experiments have demonstrated, that if, instea'd of directing a pencil of rays upon the iris, we throw it upon the retina, or through the retina on the choroid, contraction of the pupil is immediately induced. The movements of the iris must, then, be to a certain extent under the influence of the optic nerve. It is found, indeed, that if the optic nerve be divided, in a living animal, the pupil becomes immoveable and expanded. Yet, that the motions of the iris are not solely influenced by this nerve is evinced by the fact, that in many cases of complete amaurosis of both eyes, there has been the freest dila- tation and contraction of the pupil; and also, that the section of the nerve of the fifth pair, which chiefly supplies the iris, equally * Dei Mod dell' Iride, cap. i. p. 7, Lucca, 1765. b Institutiones Physiologic©, &c. Lips. 1785. c Magendie, ibid. i. 75. a Outlines of Physiology, Amer. Edit, by the Author, p. 285, Philad. 1839. * Mayo, Outlines of Physiology, 4th edit. p. 286, Lond. 1837. f Precis Elementaire, 2de e"dit. i. 74. VOL. I. — IS 206 SENSE OF SIGHT. induces immobility of the pupil. The same effect is produced, according to Mr. Mayo,a by dividing the third pair; and if the trunk of the nerve be irritated, contraction of the pupil is seen to follow; and, according to Desmoulins,b in the eagle, whose iris is extremely moveable, the third pair is the only nerve distributed to the organ. The general remark, made by Broussais0 on the organs that combine voluntary and involuntary functions, has been con- sidered to be applicable here ; — that they will be found to possess both cerebral and ganglionic nerves. Accordingly, Magendie*1 conjectures, that those of the ciliary nerves, which proceed from the ophthalmic ganglion, preside over the dilatation of the pupil, or are the nerves of involuntary action ; and that those, which arise from the nasal branch of the fifth pair, preside over the contraction of the pupil. We might thus understand why, in apoplexy, epilepsy, &c, the pupil should be immoveably dilated. All voli- tion and every cerebral phenomenon are abolished by the attack: the nerve of the fifth pair, therefore, loses its influence ; and the iris is given up to the agency of the ganglionic nerves or nerves of involuntary action, proceeding from the ophthalmic ganglion. On the whole, our notions, regarding the motions of the iris, and the nerves that preside over them, must be esteemed vague and unsatisfactory ; and the obscurity is not diminished by a remark of Bellingeri.e The iris, he observes, derives its nerves from the oph- thalmic ganglion, which is formed by the fifth in conjunction with the third pair; and its involuntary motions, he thinks, are regulated by the fifth pair. In those instances, in which the motions of the iris have been found dependent on the will, Bellingeri argues, that the ciliary nerves received no branches from the fifth — a fact, which has been proved by dissection, as well as by the circum- stance that in the parrot, the owl, and the ray genus among fishes — in which the iris is under the will of the animal — there is no ophthalmic ganglion. The iris contracts or dilates according to the intensity of the light that strikes the eye. If the light from an object be feeble, the pupil is dilated to admit more of the luminous rays: on the con- trary, if the light be powerful, it contracts. We see this very mani- festly on opening the eyes, after they have been for some time closed, and bringing a candle suddenly near them. It is one of the means we frequently employ in cerebral disease to judge of the degree of insensibility. We shall presently inquire into the effect of contraction or dilatation of the pupil on distinct vision; and show, that they are actions for accommodating the eye to vision at different distances. * Commentaries, P. ii. p. 5, and Outlines of Human Physiology, &c, 4th edit. p. 287, Lond. 1837. b Anatom. des System. Nerveux ; Paris, 1825. = Traite de Physiologie appliquee a la Pathologie, translated by Drs. Bell and La Roche, 3d edit. p. 77, Phil., 1833. d Precis, &c. ed. cit. i. 77. ' Dissert. Inaugural. Turin, 1823; and Edinb. Med. and Surg. Journal, for July, ACTION OF THE RETINA. 207 We may conclude, then, that the iris is one of the most import- ant parts of the visual apparatus ; and that its functions are multi- ple : — that it is partly the cause ofthe achromatism of the organ, by preventing the rays of greatest divergence from falling near the marginal parts of the crystalline ; — that it corrects the aberration of sphericity ; regulates the quantity of light admitted through the pupil, and accommodates the eye, to a certain extent, to vision at different distances. An enumeration ofthe multiform sentiments, entertained regard- ing the functions of the ciliary processes, will show how little we know, that is precise, on this matter also. They have often been considered contractile; some believing them connected with the motions of the iris, others to vary the distance ofthe crystalline from the retina. Jacobsona makes them dilate the apertures, which he conceives to exist in the canal godronne, so as to cause the admis- sion of a portion of the aqueous humour into the canal, and thus to change the situation of the crystalline. Others believe, that they secrete the pigmentum nigrum ; and others—the aqueous humour. But the processes are wanting in animals, in which the humours, notwithstanding, exist. There is no opinion, perhaps, more pro- bable than that of Haller ;b — that they are destined to assist me- chanically in the constitution of the eye, and have no farther use. The function of the retina remains to be considered. It is the part that receives the impression from the luminous rays, which impression is by the optic nerve conveyed to the brain. This ner- vous expansion was, at one time, universally believed to be the most delicately sensible membrane of the animal frame. Of late, it has been shown by the experiments of Magendie,0 that the sen- sibility of both it and the optio nerve is almost entirely special, and limited to the appreciation of light; — that the general sensibility is exclusively possessed by the fifth encephalic pair; and that the nerve of special sensibility is incapable of executing its functions, unless that of general sensibility be in a state of integrity. That dis- tinguished physiologist found, when a couching needle was passed into the eye at its posterior part, that the retina might be punctured and lacerated without the animal exhibiting evidences of pain. The same result attended his experiments on the optic nerves. These nerves, both anterior and posterior to their decussation, as well as the thalami nervorum opticorum, the superficial layer of the tuber- cula quadrigemina, and the three pairs of motor nerves of the eye, gave no signs of general sensibility. On the other hand, the gene- ral sensibility of the anterior part ofthe eye — of the conjunctiva — is well known. It is such, that the smallest particle of even the softest substance excites intense irritation. This general sensibility Magendied found to be totally annihilated by the division of the fifth pair of nerves within the cranium; so that hard-pointed bodies and even liquid ammonia made no painful impression on the conjunc- 1 Magendie, Precis., edit., cit. i. 78. b Element. Physiol, xvi. 4, 20. e Op. cit. i. 83. d Ibid. i. 494. 208 SENSE OF SIGHT. tiva. Nictation was arrested, and the eye remained dry and fixed like an artificial eye behind the paralysed eyelids. The sight, in this case also, was almost wholly lost; but by making the eye pass rapidly from obscurity into the vivid light of the sun, the eyelids approximated, and, consequently, some slight sensibility to light re- mained ; but it was extremely slight. In this sense, then, as in the senses of hearing and smell, we have the distinction between a special nervous system of sense, and a nervous system of general sensibility, without which the former is incapable of executing its elevated functions. The expansion of the retina occupies at least two-thirds of the circumference of the eyeball. It is of obvious importance, that it should have as much space as possible ; and, in certain animals, in which the sense is very acute, the membrane is plaited, so as to have a much larger surface than the interior of the eyeball ; and thus to allow the same luminous ray to impinge upon more than one point of the membrane. This is seen in the eyes of the eagle and vulture, and in nocturnal animals. The inconceivable acute- ness of the sense of sight in birds of prey, has been already referred to, under the sense of smell. It was there stated, that the strange facts regarding the condor, vulture, turkey-buzzard, &c, which meet in numbers in the forests, when an animal is killed, ought rather, perhaps, to be referred to acuteness of the sense of sight than of smell. Sir Everard Homea affords an addi- tional illustration of this subject. In the year 1778, Mr. Baber, and several other gentlemen, were on a hunting party in the island of Cassimbusar, in Bengal, about fifteen miles north of the city of Marshedabad ; they killed a wild hog of uncommon size, and left it on the ground near the tent. Aahour after, walking near the spot where it lay, the sky perfectly clear, a dark spot in the air, at a great distance, attracted their attention ; it appeared to increase in size, and to move directly towards them; as it advanced it proved to be a vulture flying in a direct line to the dead hog. In an hour, seventy others came in all directions, which induced Mr. Baber to remark, — "this cannot be smell." How inconceivably sensible to its special irritant must this mem- brane be in the human eye, when we consider that every part of an extensive landscape is depicted upon its minute surface; not only in its proper situation, but with all its varied tints ! and how im- practicable is it for us to comprehend,how the infinitely wider range of country can be so vividly depicted on the diminutive eye of the vulture, as to enable it to see its prey from such a remote distance ! If pressure be made on the eyeball, behind the cornea so as to affect the retina, concentric luminous circles will be seen, opposite to the part on which the pressure is applied; and, if the pressure be continued for twenty or thirty seconds, a broad undefined light, which increases in intensity every moment, rises immediately before the eye. If the eyelids be open, and light be present, on a Lectures on Comparative Anatomy, Lond. 1814-1828. ACTION OF THE RETINA. 209 the repetition of the last experiment, a dense cloud arises, instead ofthe broad undefined light, and the eye becomes, in a few seconds, perfectly blind, but in the course of three or four seconds after the finger is removed, the cloud appears to roll away from before the eye. From this, it seems, that sensations of light may be pro- duced by mechanical pressure made on the retina ; in other words, the retina becomes phosphorescent by pressure. The same thing, too-, is observed, if a sudden blow be given on the eye, or if we place a piece of zinc under the upper lip, and a piece of copper above the eye. A flash of light is seen ; produced, doubtless, by the galvanic fluid impressing directly, or indirectly, the optic nerve. The same thing occurs in the act of sneezing, and in forcing air violently through the nostrils. On repeating the experiment of pressing the eyeball, Sir David Brewster3 observed, that when a gentle pres- sure was first applied, so as to compress slightly the fine pulpy substance of the retina, a circular spot of colourless light was pro- duced, though the eye was in total darkness, and had not been ex- posed to light for many hours; but if light be now admitted to the eye, the compressed part of the retina is found to be more sen- sible to the light than any other part, and consequently it appears more luminous. If the pressure be increased, beyond the point mentioned above, the circular spot of light gradually becomes darker, and, at length, black, and is surrounded with a bright ring of light. By augmenting the pressure still more, a luminous spot appears in the middle of the central dark one, and another lumi- nous spot diametrically opposite, and beneath the point of pressure. " Considering the eye," says Sir David, " as an elastic sphere, filled with incomprehensible fluids, it is obvious, that a ring of fluids will rise round the point depressed by the finger, and that the eyeball will protrude all round the point of pressure ; and con- sequently the retina, at the protruded part, will be compressed by the outward pressure of the contained fluid, while the retina on each side, — that is, under the point of pressure, and beyond the protruded part, — will be drawn towards the protruded part or be dilated. Hence the part under the finger, which was originally compressed, is now dilated, the adjacent parts are compressed, and the more remote parts, immediately without this, dilated also." " Now," continues Sir David, " we have observed, that when the eye is, under these circumstances, exposed to light, there is a bright luminous circle shading off externally and internally into total darkness. We are led therefore to the important conclusions, that when the retina is compressed in total darkness it gives out light; that when it is compressed, when exposed to light, its sen- sibility to light is increased; and that when it is dilated under ex- posure to light, it becomes absolutely blind or insensible to all luminous impressions." Having traced the mode in which the general physiology of 1 Letters on Natural Magic, Amer. Edit. p. 27, New York, 1832. 18* 210 SENSE OF SIGHT. vision is effected, and the part performed by each of the consti- tuents of the eye proper, we shall briefly consider the functions of the rest of the visual apparatus, the anatomical sketch of which has been given under the head of accessory organs ; and after- wards inquire into the various interesting and important pheno- mena exhibited by this sense. These organs perform but a secondary part in vision. The orbit shelters the eye, and protects it from external violence. The eyebrows have a similar effect ; and, in addition to this, the hair, with which they are furnished, by virtue of its oblique direction towards the temple, and by the sebaceous secretion that covers it, prevents the perspiration from flowing into the eye, and directs it towards the temple or the root of the nose. By contracting the eyebrows, they can be thrown forwards and downwards in wrinkles ; and can thus protect the eye from too strong a light, especially when coming from above. The eyelids cover the eye during sleep, and preserve it from the contact of extraneous bodies. During the waking state, this protection is afforded by the instantaneous occlusion of the eye- lids, on the anticipation of danger to the ball. The incessant nictation likewise spreads the lachrymal secretion over the sur- face of the conjunctiva, and cleanses it: whilst the movement, at the same time, probably excites the gland to augmented secretion. The chief part ofthe movement of nictation is performed by the upper eyelid ; the difference in the action of the eyelids being estimated, by some physiologists, as four to one. Under ordinary circumstances, according to Adelon,a it is the levator palpebral superioris, which, by its contraction or relaxation, opens or closes the eye ; the orbicularis palpebrarum not acting. If the levator be contracted, the eyelid is raised and folded between the eye and orbit, and the eye is open ; if, on the other hand, the levator be relaxed, or spread passively over the surface of the organ, the eye is closed. In this view, the orbicularis muscle is not contracted, except in extraordinary cases, and under the influence of volition; whilst the closure ofthe eye, during sleep, is dependent upon sim- ple relaxation of the levator. The views of Broussaisb on this subject are, we think, more satisfactory. He considers, that the open state of the eye, in the waking condition, requires no effort; because the two muscles of the eyelids are so arranged, that the action of the levator is much more powerful than that of the orbi- cularis ; and he adduces, in proof of this, that the eyelids, at the time of death, are half open. On the other hand, the closure of the eye in sleep, he conceives to be owing to the contraction of the orbicularis muscle, which acts whilst the others rest. If the open- ing of the eye were wholly dependent upon the action of the leva- tor palpebrss superioris muscle, its relaxation, during insensibility and death, ought to be sufficient to close the eye completely ; and the orbicularis palpebrarum would be comparatively devoid of function ; being only necessary for the closure of the organ under the influence of volition. a Physiologie de l'Homme, 2de edit. i. 419, Paris, 1829. b Edit, citat. p. 188. ACTION OF THE MUSCLES OF THE EYEBALL. 211 It has been found by experiments, instituted by Sir Charles Bell,a and by Magendie,b that nictation is effected under the in- fluence chiefly of the portio dura of the seventh pair, or facial nerve, — one of the respiratory nerves of Sir Charles Bell's system — the respiratory of the face. When this nerve is cut, nictation is completely arrested ; and when the nerve of the fifth pair, also distributed to these parts, is divided, it ceases likewise, but less thoroughly; a very vivid light exciting it, but only at considerable intervals, and imperfectly. We see here something very analogous to the partition of the nerves of the senses into those possessing general, and those conveying special sensibility. Like the latter functionaries, the nerve of the seventh pair appears to be specially concerned in nictation, and not to be capable of executing its office, unless the fifth pair — the nerve of general sensibility—be in a state of integrity. The explanation of Dr. Marshall Hall is differ- ent. It has been before remarked, that if the functions of the brain be suspended or destroyed, the true spinal system being un- injured, the orbicularis palpebrarum will still contract so as to close the eyelids, when the tarsus is touched with any solid body. In this case, neither sensation nor volition can be concerned. It is a reflex action ; the excitor nerves being probably branches of the fifth pair, and the motor,branches of the seventh pair. Hence, when the will ceases to act as in sleep, or in apoplexy, the lids close over the eye to protect it. In the waking state, the levator palpebrae under the influence of the will acts as an antagonist to the orbicu- laris and keeps the eye open; but there is an almost irresistible tendency to close the eye ; and, as in the case of respiration, the muscular contraction can only be restrained to a certain degree : it takes place, whenever the condition of the conjunctiva is such as to occasion an impression to be conveyed along the excitor nerve which demands a reflex movement to modify it; for example, when particles of dust collect upon it; or the surface becomes dry.c The eyelids, by their approximation, can regulate the quantity of light that enters the pupil, when it is injuriously powerful; when feeble, they are widely separated, to allow as much as pos- sible to penetrate the organ. By their agency, again, the most diverging rays from an object can be prevented from falling upon the cornea; and the vision of the myopic or short-sighted can, in this way, be assisted. It is a means of which they often avail themselves. The cilia ox eyelashes, it is probable, are of similar advantage as regards the admission of light into the eye, and have some part, probably, in preventing extraneous bodies, borne about in the air, from reaching the sensible conjunctiva. The muscles of the eyeball have acquired the chief portion of their interest of late years, and largely through the investigations of the eminent physiologist—of whose labours we have so fre- a The Nervous System of the Human Body, Amer. Edit. p. 48, Washington, 1833. & Precis Elementaire, i. 309. c Carpenter, Human Physiology, p. 154, Lond. 1842. 212 SENSE OF SIGHT. quently had occasion to speak — Sir Charles Bell.* The arrange- - ment of the four straight muscles, and especially their names — sufficiently indicate the direction in which they are capable of mov- ing the organ, when acting singly. If any two of them contract together, the eyeball will, of course, be moved in the direction of the diagonal between the two forces ; and if each muscle contracts rapidly after the other, the organ will execute a movement of cir- cumduction. The oblique muscles are antagonists to each other, and roll the eye in opposite directions; the superior oblique di- recting the pupil downwards and inwards ; the inferior upwards and inwards. But as the different straight muscles are capable of carrying the eye in these directions, were we to regard the two sets of muscles as possessing analogous functions, the oblique would appear to be superfluous. This, along with other reasons, attracted the attention of Sir Charles Bell to the subject; and the result of his experiments and reflections was : — that the straight muscles are concerned in the motions of the eye excited by voli- tion : and that the oblique muscles are the organs of its involun- tary motions; and, in this manner, he accounts for several phe- nomena, connected with the play of these organs in health and disease. Whilst the power of volition can be exerted over the recti muscles, the eye is moved about, in the waking state, by their agency; but,"as soon as volition fails from any cause, the straight muscles cease to act, and the eye is turned up under the upper eyelid. Hence this happens at the approach of, and during sleep ; and whenever insensibility occurs from any cause, as in faintness, or on the approach of dissolution ; and that turning up of the eyeball, which we have been accustomed to regard as the expression of agony, is but the indication of a state of incipient or total insensibility. Whenever, too, the eyelids are closed, the eyeball is moved, so that the cornea is raised under the upper eye- lid. If one eye be fixed upon an object, and the other be closed, with the finger so placed as to feel the convexity of the cornea through the upper eyelid, and the open eye be shut, the cornea of the other eye will be found to be elevated. This change takes place during the most rapid winking motions of the eyelids ; and is obviously inservient to the protection of the eye : to the clearing of the eyeball of everything that could obscure vision, and perhaps, as Sir Charles Bell presumes, to procure the discharge from the ducts ofthe lachrymal gland. During sleep, when the closure of the eye is prolonged, the transparent cornea is, by this action, turnedupundertheuppereyelid,whereitis securely longed andkept moist by the secretions ofthe lachrymal gland and conjunctiva. The different distributions of the motor nerves of the eye have been described iti the anatomical sketch. It was there stated, that the superior oblique muscle receives one whole pair of nerves : — the fourth. This nerve, then, it seemed to Sir Charles Bell, must a Op. citat. p. 102, and Anatomy and Physiology, 5th Amer. Edit. ir. 213, New York, 1«27. ACTION OF THE MUSCLES OF THE EYEBALL. • 213 be concerned in the functions we have described; and,as the various involuntary motions of the eyeball are intimately concerned in ex- pression, as in bodily pain, and in mental agony, — in which the action ofthe direct muscles seems, for a time, to be suspended, — he was led to consider the fourth pair as a nerve of expression — a respiratory nerve ; and, hence, intimately connected with the facial nerve of the seventh pair, which, as has already been remarked, is the great nervous agent in the twinkling of the eyelids. Anato- mical examination confirmed this view ; — the roots of the nerve being found to arise from the same column as the other respiratory nerves. The coincidence of this twinkling, and of the motion of the eyeball upwards, was, therefore, easily understood. There is a difficulty, however, here, which has doubtless already suggested itself. The fourth pair of nerves is distributed to the superior ob- lique only; the lesser oblique receives none of its ramifications. They cannot, therefore, be identically situate in this respect. Yet they are both considered by Sir Charles Bell as involuntary muscles. The action, indeed, of the lesser oblique would appear to be even more important than that of the greater oblique, as the function of the former, when acting singly, is to carry the eye upwards and inwards ; and, when the action of its antagonist is abolished, this is more clearly manifested : Sir Charles found, that the effect of divi- ding the superior oblique was to cause the eye to roll more forcibly upwards; — in other words, it was given up, uncontrolled, to the action of the antagonist muscle. This difficulty, although it is not openly stated by Sir Charles, must have impressed him ; as, after having referred to the effect of the division of the superior oblique, he is constrained to suggest an influence to the fourth pair, which would, we think, be anomalous: — that it may on certain occasions cause a relaxation of the muscle to which it goes, and, in such case, the eyeball must be rolled upwards ! In addition to this, too, as Mr. Mayoa has observed, the distribution of the muscular nerves of the eye is not such as to allow of our opposing the straight muscles to the oblique, and one cogent reason is, that the third pair of nerves supplies part of each class. We have still, therefore, much to learn regarding this subject, into which so much interest, and, at the same time, so much un- certainty has been infused.b In some recent experiments on the fresh subject, with Professor Pancoast, who carefully separated the different muscles, with the view of discovering their precise action, it was clearly apparent, that the oblique muscles act in the manner above mentioned ; the superior oblique directing the eye slightly inwards and downwards; and the inferior, rolling it up- wards and inwards, when they acted singly; but when the two " were brought into action simultaneously, they appeared to anta- » Outlines of Human Physiology, 4th edit, p 299, Lond. 1837. b See, on this subject, Carpenter's Human Physiology, p. 185, Philad. 1842 ; MM. Pravaz, Bonnet, Gue"rin, &c, in Archiv. gener. de Med. Mai, 1841, &c, cited in Brit. and For. Med. Rev. Oct. 1841, p. 553; and Valentin, Traite de Nevrologie, trad, par Jourdan, p. 290, Paris, 1843. 214 SENSE OF SIGHT. gonize each other as rotators, but projected the eye forward. It would seem, indeed, that an important use of these muscles is to keep the eye prominent during the action of the straight muscles. These results harmonise greatly with the deductions from expe- riments on living animals by Mr. Bransby Cooper.a He divided the superior and oblique muscles on the eyes of several living rabbits; and inferred, that the oblique muscles, when acting to- gether, suspend the eyeball in a central position in the orbitar cavity, moderate the retracting influence ofthe four straight mus- cles ; and, when acting in succession, without being restricted by the influence of the straight muscles, they roll the eye on its own axis, drawing the globe forward, and at the same time tending, in a great degree, to extend the sphere of vision. The great use of the tears would seem to be to moisten the con- junctiva, and to remove extraneous bodies from its surface, — thus assisting the motions of the eyelids and eyeball, just referred to. The tears are secreted by the lachrymal gland ; and, by means of its excretory ducts, they are poured upon the surface of the tunica conjunctiva, at the upper and outer part of the eye. Their farther course towards the puncta lachrymalia has been the subject of dif- ference of sentiment. The generality of physiologists consider, that, owing to the form ofthe tarsal cartilages, a canal must exist, when the eyelids are closed, of a triangular shape, formed anteriorly by the junction of the cartilages, and behind by the ball of the eye. Magendie,b on the other hand, denies the existence of this canal, and asserts that the tarsal cartilages do not touch by a rounded edge, but by an inner plane surface. If we were to grant the exist- ence of this canal, it could only aid us in our explanation of the course of the tears during sleep. In the waking state, they are not ordinarily secreted in such quantity as to require that much should pass to the puncta; — the movements of nictation spreading them over the surface of the eye, whence they are partly absorbed, and the rest, perhaps, evaporated. Under extraordinary circumstances, however, the gland increases its secretion so much, that the tears not only pass freely through the lachrymal ducts into the nose, but flow over the lower eyelid. The epiphora or watery eye, caused by obstruction of these ducts, also proves that a certain quantity of the secretion must always be passing into the puncta. The physical arrangement of the eyelids and tunica conjunctiva is doubtless the cause of their course in this direction. It has been gratuitously supposed by some, that the humour of Meibomius prevents the tears from reaching the outer surface of the lower eyelid, by acting like a layer of oil on the margin of a vessel filled with water. A similar function has been assigned to the secretion of the caruncula lachrymalis. Both these fluids, however, are probably inservient to other ends. They are readily miscible with water \ become consequently dissolved in the tears, * Guy's Hospital Reports, vol. iii. April and October, 1838. b Precis edit. &c. cit. i. 52. COURSE OF THE TEARS. 215 and, with the assistance of the fluid secreted by the tunica conjunc- tiva, aid the movements ofthe eyelids over the ball of the eye, and keep the tarsal margins and their appendages in the condition re- quisite for the due performance of their functions. The action of the puncta themselves in admitting the tears has received different explanations. Adelon3 regards it as organic and vital. We ought, however, in all cases, to have recourse to this mode of accounting for phenomena as the ultima ratio, and the present appears to us to be a case in which it is singularly unne- cessary. In many of the results of absorption we are compelled to suppose, that a vital operation must have been concerned in the process. Where, for example, as in the case of the lymphatic ves- sels, we find the same fluid circulating, whatever may have been the nature of the substances whence it was obtained, the evidence, that a vital action of selection and elaboration has been going on, is irresistible ; but no such action can have occurred in the case in question. The tears in the lachrymal ducts and in the ductus ad nasum are identical with those spread upon the surface of the eye ; the only difference being in their situation. This is one of the few cases in the human body, which admit of satisfactory explanation on the physical principles of capillary attraction. In vegetables, the whole of the circulation of their juices has been thus accounted for. If we twist together several threads of yarn, moisten them, and put one extremity ofthe roll into a vessel of water, allowing the other to hang down on the outside of the vessel, and to dip into an empty vessel placed below it, we find, that the whole of the fluid, in the first vessel, is in a short time transferred to the second. If, again, we take a small tube, less than the twentieth part of an inch in diameter, which is called capillary, and place it so as to touch the surface of water, we find, that the water rises in it to a height, which is greater, the smaller the bore of the tube. If the diameter of the tube be the fiftieth part of an inch, the water will rise to the height of two inches and a half; if the one hun- dredth part of an inch, to five inches ; if the two hundredth part of an inch, to ten inches ; and so on. Now, the punctum lachry- male is, in our view of the subject, the open extremity of a capil- lary tube, which receives the fluid of the lachrymal gland and conveys it to the nose, the punctum being properly directed towards the eyeball by the tensor tarsi muscle of Horner. Lastly, — the tunica conjunctiva is another part of the guardian apparatus of the eye. It secretes a fluid, which readily mixes with the tears, and appears to have similar uses. Like the mucous membranes in general, it absorbs ; and, in this way, a part of the lachrymal secretion is removed from its surface. An animal, for the same reason, can be readily poisoned by applying hydrocyanic acid to it. As the conjunctiva lines the eyelids, and is reflected over the globe, it supports the friction, when the eyeball or eyelids are moved ; but, being highly polished and always moist, the whole of this is insignificant. 1 Physiologie, 2de edit. p. 421, Paris, 1829. 216 SENSE OF SIGHT. The extreme sensibility of the outer part of the eye appertains entirely to the tunica conjunctiva,'and is dependent on the ophthal- mic branch of the fifth pair. When this nerve was divided in a living animal, Magendie3 found, that the membrane became en- tirely insensible to every kind of contact, even of substances that destroyed it chemically. In his experiments on this subject, he arrived at some singular results, regarding the influence of the fifth pair on the nutrition of the eye. When the trunk of the nerve was divided within the cranium a little after its passage over the petrous' portion of the temporal bone, the cornea was found, about twenty- four hours afterwards, to become troubled, and a large spot to form upon it. In the course of from forty-eight to sixty hours, this part was completely opaque; and the conjunctiva, as well as the iris, was in a state "of inflammation ; a turbid fluid was thrown out into the inner chamber, and false membranes proceeded from the inte- rior surface of the iris. The crystalline and vitreous humours now began to lose their transparency; and, in the course of a few days, were entirely opaque. Eight days after the division of the nerve, the cornea separated from the sclerotica ; and the portions of the humours that remained fluid escaped at the opening. The organ diminished in size, and ultimately became a kind of tubercle, filled with a substance of a caseous appearance. Magendie properly concludes from these experiments, that the nutrition of the eye is under the influence of the fifth pair; and he conceives, that the opacity of the cornea was directly owing to the section of this nerve, and not to a cessation of the lachrymal secretion* or to the prolonged contact of air, caused by the paralysis of the eyelids; inasmuch as when the branches of the nerve proceeding to the eyelids were simply divided, or when the lachrymal gland was taken away, the opacity did not supervene. 5. PHENOMENA OF VISION. It has been more than once remarked, that the retina— the ex- pansion of the optic nerve — is the part of the eye which receives the impressions of luminous rays, whence they are conveyed by the optic nerve to the brain. Yet this has been contested. The Abbe Mariotteb discovered the singular fact, that when a ray of light falls, as he conceived, upon the centre of the optic nerve, it excites no sensation. " Having often observed," he remarks, " on dissections of men as well as of brutes, that the optic nerve does never answer just to the middle of the bottom of the eye; that is, to the place where the picture of the object we look directly upon is made ; and that in man it is somewhat higher, and on the side towards the nose ; to make therefore the rays of an object to fall upon the optic nerve of my eye, and to find the consequence thereof, I made this experiment. I fastened on an obscure wall, about the height of my eye, a small round paper, to a Precis Elementaire, ii. 494. b Philos. Transact, iii. 668, and Memoir, de l'Academie Royale des Sciences, torn i. pp. 68 and 102. EXPERIMENT OF MARIOTTE. 217 serve me for a fixed point of vision. I fastened such another on the side thereof towards my right hand, at the distance of about two feet, but somewhat lower than the first, to the end that I might strike the optic nerve of my right eye, while I kept my left shut. Then I placed myself over against the first paper, and drew back by little and little, keeping my right eye fixed and very steady on the same, and being about ten feet distant, the second paper totally disappeared." The experiment of Mariotte can be readily repeated on the marginal representations of the fleur-de-lis and the anchor. If we close the left eye, and direct the axis of F'g- 43- the right eye steadily ^ *$? towards the anchor, when the page is held at the distance of about ten inches from the eye, the fleur-de-lis will vanish. The distance of the object which disappears from the eye, must be about five times as great as its distance from the other object. In this case the fleur-de-lis and anchor are two inches asunder. It is obvious, from what has been said, regarding the axis of the orbits, and the part of the eyeball at which the optic nerve enters — that rays of light from an object can never fall, at the same time, upon the insensible point of each eye. The defect in vision is, consequently, never experienced except in such experiments as those performed by Mariotte. In one of these he succeeded in directing the rays to the insensible point of both eyes at once. He put two round papers at the height of the eye, and at the distance of three feet from each other. By then placing himself opposite them, at the distance of twelve or thirteen feet, and holding his thumb before his eyes, at the distance of about eight inches, so that it concealed from the right eye the paper on the left hand, and from the left eye the paper on the right, he looked at his thumb steadily with both eyes, and both the papers were lost sight of. These experiments certainly show, that there is a part of the retina or optic nerve which is, in each eye, insen- sible to light; and that this point is on the nasal side of the axis. No sooner, however, had Mariotte published an account of his experiments than it was decided that this spot was the basis of the optic nerve; a conclusion was accordingly drawn, that the nerve is incapable of distinct vision, and this conclusion has been embraced, without examination, in almost all the books of optics to the present time. Although probable, however, it is by no means certain that the light, in these cases, falls upon the base of the nerve. The direction in which the ray proceeds is such that it is reasonable to suppose it does impinge there : the suggestion of M. Tillaye,a that it falls upon the yellow spot of Sommering, can only be explained by presuming him to have been in utter ignorance of its situation, which we have seen to be on the outer i Adelon, Physiologie, 2de edit. i. 448, Paris, 1829. VOL. I. --- 19 218 SENSE OF SIGHT. side of the nerve. But, granting that the light falls on the base of the nerve, it by no means demonstrates, that the nerve is inca- pable of receiving the impression. It has been already shown, that the central artery of the retina penetrates the eye through the "very centre of the nerve; and through the same opening, the central vein leaves the organ. It is probable, therefore, that in these experiments, the ray falls upon the bloodvessels, and not upon the medullary matter of the nerve ; and if so, we could not expect that there should be sensation. That the insensible spot is of small magnitude is proved by the fact, that if candles are sub- stituted for the round papers or wafers, the candle does not dis- appear but becomes a cloudy mass of light. It is true, Daniel Bernouillia considered the part of the nerve insensible to distinct impressions to occupy about the seventh part of the diameter of the eye, or about the eighth of an inch ; but there must evidently have been some error in his calculations, for the optic nerve itself can rarely equal this proportion. The estimate of Le Cat,b who was himself a believer in the views of Mariotte, that its size is about one-third, or one-fourth of a line, is probably still wider from the truth in the opposite direction. Simple experiment, with two wafers placed upon a door at the height of the eye, will show clearly, that both the horizontal and vertical diameters of the spot must be larger than this. The fact, observed by Mariotte, was not suffered to remain in repose. A new hypothesis of vision was formed upon it; and, as he considered it demonstrated, that the optic nerve was insensible to light, he drew the inference, that the retina was so likewise ; and as vision was effected in every part ofthe interior ofthe eye, except at the base ofthe optic nerve, where the choroid is alone absent he inferred that the choroid must be the true seat of vision. The controversy, at one time maintained on this subject, has died away, and it is not our intention to disturb its ashes, farther than to re- mark, that M. De La Hire,c who engaged in it, entertained the opinion, that the retina receives the impression of the light in a secondary way, and through the choroid coat as an intermediate organ ; that by the light striking the choroid coat, the membrane is agitated, and the agitation communicated to the retina. The views of De La Hire are embraced by Brewster,*1 as well as by nu- merous other philosophers. The opinions of Mariotte have now few supporters. The re- marks already made, regarding the optic nerve ; the effect of dis- eases of the retina, of the nerve itself, and of its thalami, compel us to regard its expansion as the seat of vision ; and if we were even to admit, with Mariotte, that the insensible portion is really a part ofthe medullary matter of the nerve, and not a bloodvessel 1 Haller. Element. Physiolog. xvi. 4, 4. b Traite des Sens, Paris, 1767; or English translation, Lond. 1750. c Mem de l'Academie, torn. ix. d Treatise on Optics, Amer. Edit, by A. D. Bache, p, 243, Philad. 1833. CAUSE OF ERECT VISION. 219 existing there, we could still satisfactorily account for the pheno- menon by the anomalous circumstances in which the nervous part of the organ is there placed. The choroid coat, of great import- ance in the function, as well as the pigmentum nigrum, is absent; and hence we ought not to be surprised, that the function is imper- fectly executed ; we say imperfectly, for the experiment with the candles exhibits that the part is not really insensible to Ii°-ht; or is so in a very small portion of its surface only. It may seem at first sight, that the fact of this defect existing only in the centre of the optic nerve, or at the p or us opticus, as it has been termed, where the central artery of the retina enters, and the corresponding vein leaves the organ, militates against the idea of its being caused bv the rays impinging upon these vessels ; as, if so, we ought to have similar defects in every part ofthe retina, where the ramifications of these vessels exist. Circumstances are not here, however, iden- tical. When the ray falls upon the porus opticus, it strikes the vessels in the direction of their length ; but, in the other cases, it falls transversely upon them, pierces them, and impresses the retina beneath ; so that, under ordinary circumstances, little or no difference is perceived between the parts of the retina over which the vessels creep, and the remainder of its extent. We can, how- ever, by an experiment of Purkinje, described by J. G. Stein'buch,a exhibit, that under particular circumstances such difference really exists, and renders the bloodvessels of the organ perceptible to its own vision. If, without closing the eyelids, the left eye be covered with the hand, or some other body, and a candle or lamp be held in the right hand, within two or three inches of the right eye, but rather below it, (keeping the eye directed straight forward') on moving the candle slowly from right to left, (or if the candle be held on the right side of the eye, it may be moved up and down,) a spectrum appears, after a short time, in which the bloodvessels of the retina, with their various ramifications, are distinctly seen, projected, as it were, on a plane without the eye, and greatly mag- nified. They seem to proceed from the optic nerve, and to consist of two upper and two lower branches, which ramify towards the field of vision, where a dark spot is seen, corresponding to the foramen centrale. The origin of the vessels is a dark oval spot, with an areola.b This phenomenon must be accounted for by the parts ofthe retina, covered by the bloodvessels, not being equally fatigued with those that are exposed. It is by no means uncommon for appearances of cobwebs, small tubes with lateral pores, &c, to present themselves before the eyes without changing their position when the eyes are fixed upon an object. These appearances are not owing to any modification in the humours, but are apparently dependent upon the physical con- dition of the retina. Some years ago, a tube of the kind men- * Beitrag zur Physiologie der Sinne, Nurnherg, 1811 » See on the subject of rendering the bloodvessels of the observer's retina apparent YorM836 ' entUleJ Discoveries in LiSht ™* Vision, p. 86, New 220 SENSE OF SIGHT. tioned, but apparently terminating in an open mouth, was the occasion of some uneasiness to the author. This is now no longer seen, but numerous opacities, somewhat resembling plexuses of vessels or nerves, are still apparent.8 ' It has been remarked, that the rays, proceeding from the upper part of an object, impinge upon the lower part of the retina ; and those from the lower part on the upper portion of the retina; hence the image of the object is reversed, as in Fig. 41. It has, accordingly, been asked ; — how it is, that in these circumstances, we see the" object in its proper position, inasmuch as its image is inverted on the retina ? Buffon,b Le Cat,c and others believed, that, originally, we do not see them so inverted ; but that the sense of touch apprises us of our error, and enables us to correct it at so early a period, and so effectually, that we are afterwards not aware of the process: but this cannot apply to the lower animals, and, accordingly, in regard to them the knot has been cut by the sup- position — which is probably correct — that in them it is innate or intuitional.11 Berkeley,e again, asserted, that the position of objects is always judged of, by comparing them with our own; and that, as we see ourselves inverted, external bodies are in the same relation to us as if they were erect. It is not necessary to reply, at length, to these phantasies, which are obviously founded in error. Cases enough have occurred, of the blind from birth hav- ing been restored to sight, to show, that no such inversion, as that described by Buftbn, takes place : the boy, who stoops down, and looks at objects between his legs, although he may be, at first, a little confused, from the usual position of the images on the retina being reversed, soon sees as well in that way as in any other. The truth is, the great error with all these speculatists has been, that they have imagined a true picture to be formed on the retina, which is regarded by the mind, and therefore seen inverted. It need hardly be said, that there is no interior eye to take cogni- zance of this image ; but that the mind accurately refers the im- pression, made upon the retina, to the object producing it; and if the lower part of the retina be impressed by a ray from the upper part of an object, this impression is conveyed by the retina to the brain as it receives it, and no error can be indulged. Professor Alisonf offers an explanation, first suggested to him by Mr. Dick, veterinary surgeon, which turns on the alleged fact, that the course of the optic nerves and tractus optici is such, that impressions on the upper part of the retina are, in fact, impressions on the lower part of the optic lobes, that is, of the sensorium, — and impressions * See, Dr. Alexander, in Boston Med. and Surg. Journal, June 7, 1837, and Jan. 23, 1839, p. 389 ; also, Dunglison's Amer. Med. Intelligencer, i. 145 and 186, Philad. 1838; W. Clay Wallace, Lond. Med. Gaz. Oct. 1838; and Treatise on the Eye, 2d edit., New York, 1839. t M^moires de l'Academie, 1743, p. 231. c Op. citat. a Carpenter, Human Physiology, p. 266, Lond. 1842. e Essay on Vision, 2d edit., Dublin, 1709. f On Single and Correct Vision, by means of double and inverted Images on the Retinae, in Transact, ofthe Royal Society of Edinburgh, vol. xiii. Edinb. 1836. CAUSE OF ERECT VISION. 221 on the outer part of the former are on the inner part of the latter, and conversely. When a cone of light proceeds from a radiant point, as from B, Fig. 41, the whole ofthe rays, — whatever may be their relative obliquity,—are, as we have seen, converged to a focus upon the retina at b, yet the point B is seen only in one direction, in that of the central ray or axis of the cone B b. If we look over the top of a card at the point B, till the edge of the card is just about to hide it; or if, in other words, we obstruct all the rays that pass through the pupil, excepting the uppermost ray, the point is still seen in the same direction as when it was viewed by the whole cone of rays proceeding from B. If we look, again, beneath the card, in a similar manner, so as to see the object by the lowest ray of the cone, the radiant point will be equally seen in the same direction. Hence, says Sir David Brewster,3 it is manifest that the line of visible direction does not depend on the direction of the ray, but is always perpendicular to the retina ; and, as the surface of the re- tina is a portion of a sphere, those perpendiculars must all pass through one point, " which may be called the centre of visible di- rection ; because every point of a visible object will be seen in the direction of a line drawn from this centre to the visible point." The point o, Fig. 41, is, in Sir David's view, this centre of visible direction. Where a luminous cone proceeds in the direction of the axis of the eye, the centre of visible direction will fall in that line, and a perpendicular, drawn from the point b, where the rays of the cone meet at a focus on the retina, will pass through this cen- tre of visible direction o, and the same thing, he conceives, will apply to every other pencil of rays. Thus, the rays from D and E, which fall upon the cornea at /, will be refracted so as to im- pinge upon the retina at s and r respectively, and D and R will be seen in the direction of lines drawn from these points to the centre of visible direction, o. This " law of visible direction," laid down by Sir David Brewster, removes at once, he thinks, every difficulty that besets the subject we have been considering; — the cause of erect vision from an inverted image on the retina. The lines of visible direction necessarily cross each other at the centre of visible direction, so that those from the lower part of the image go to the upper part of the object, and those from the upper part ofthe image to the lower part of the object. The views of Sir David are embraced by Mr. Mayo,b who considers them confirmed by the fact —to which reference has already been made — that any pressure made upon the retina through the eyeball, causes a spectrum to be seen in a direction opposite to the point compressed, as well as by the following experiments of Scheiner, by whom this law of visual direction was first shown. If the head of a pin, strongly illuminated, be viewed with one eye at a distance of four inches, that is, within the common limit of distinct vision, the ob- ject is seen large and imperfectly defined, the outermost cone of 1 Op. citat. p. 246. b Outlines of Human Physiology, 3d edit. p. 277. 222 SENSE OF SIGHT. rays, which enter the pupil from each point, being too divergent to be collected to a focus on the retina. If a card, pierced with a pinhole, be now interposed between the eye and the object, the latter may be seen distinctly defined through the pinhole, by means of rays that have entered the pupil nearly parallel, with a slightly divergent tendency. But the object may be seen by rays passing either through the upper or lower part, the right or left side, or the centre of the pupil. Upon shifting the card for this purpose the object appears to move in an opposite direction. Or, if three pinholes be made, one in the centre, and one at either side, the object appears tripled ; and if one ofthe side holes be closed, the opposite of the three objects disappears : if, for example, the left hand pinhole be closed, the right object disappears. Again, if the head of a pin, strongly illuminated, be viewed at the distance of eighteen inches, its outline is distinct and clear: the rays passing from each point of the object, are brought to a point on the retina, but these rays reach the retina at different angles, and, by inter- posing a card perforated with a single pinhole, the object may be seen by rays, which enter the upper part, or the lower part, or the centre ofthe pupil. No change, however, in the visual place of the object occurs in this instance, as the card is shifted ; nor is the image multiplied when seen through several pinholes in the card. The last experiment, says Mr. Mayo, proves, that the angle at which rays of light fall upon the retina, does not affect our notion of the place of objects, and, taken with the Fig. 44. preceding, establishes as an inductive law, that the retina is so constituted, that, how- ever exerted, each point of it sees in one di- rection only, that direction being a line ver- tical to it; or that in every instance of vision, each point of an object is seen in the direc- tion of a line vertical, to the point of the retina upon which the rays proceeding from it are collected. It would seem, however, to be a forcible objection to this view ofthe subject: that all the objects a, a' and a" on \ \ ''%-a tne line c a", Fig. 44, must fall upon exactly the \ \ same point ofthe cornea,and, therefore, upon \ \ the same point of the retina ; yet, as only one \ \ of these lines b a is perpendicular to the point \ \ „r of the retina on which the rays are collected; \ such a perpendicular would obviously refer \ the position of the object a alone correctly. Moreover, accurate examination would ap- \ n peartoshow that this law of visible direction, a first pointed out by Sir David Brewster, can not be optically correct, as the lines of di- rection cross each other at a point much anterior to the centre of the eyeball. This may be proved by making a diagram of the eye on a large scale,and laying down the course ofthe rays entering the organ, according to the curvatures, and refractive powers of ACCIDENTAL COLOURS. 223 its different parts. In this manner, Volkmann found, that the lines of direction cross each other at a point a little behind the crystalline, and that they will thus fall at such different angles on different points ofthe retina, that no general law can be deduced respecting them.3 A certain intensity of light is necessary, in order that the retina may be duly impressed, and this varies in different animals; some of which, as we have seen, are capable of exercising the function of vision in the night, and have hence been termed nocturnal. In man, the degree of light, necessary for distinct vision, varies ac- cording to the previous state of the organ. A person, passing from a brilliantly illuminated room into the dark, is, for a time, incapa- ble of seeing any thing, but this effect differs in individuals ; some being much more able to see distinctly in the dark than others. This is owing to the retina, in some, being more sensible than in others ; and, consequently, requiring a less degree of light to im- press it. On the other hand, a very powerful light injures the retina, and deprives it, for a time, of its function; hence the un- pleasant impression produced by the introduction of lights into a room, where the company have been previously sitting in com- parative obscurity ; or by looking at the sun. The effect upon the retina, thus induced, is called dazzling. If the light that falls upon the eye be extremely feeble, and we look long and intensely upon any minute object, the retina is fatigued; the sensibility of its central portion becomes exhausted, or is painfully agitated ; and the objects will appear and disappear, according as the retina has recovered or lost its sensibility; a kind of remission seeming to Jake place in the reception of the impressions. These affections are considered by Sir David Brewsterb as the source of many optical deceptions, which have been ascribed to a supernatural origin. « In a dark night, where objects are feebly illuminated, their disappearance and reappearance must seem very extraordinary to a person whose fear or curiosity calls forth all his powers of observation. This defect of the eye must have been often noticed by the sportsman, in attempting to mark, upon the monotonous heaths, the particular spots where moorgame had alighted. Availing himself ofthe slightest difference of tint in the adjacent heaths, he endeavours to keep his eye steadily upon it as he advances ; but whenever the contrast of illumination is fee- ble, he almost always loses sight of his mark, or if the retina does take it up a second time, it is only to lose it again." In all the cases, in which the eye has been so long directed to a minute object, that the retina has become fatigued, on turning the axis of the eye slightly away from the object, the light from it will fall upon a neighbouring part of the retina, and the object will be again perceived; and in the mean time the part, previously in ac- tion, will have recovered from its fatigue. By this fact—- of the retina becoming fatigued by regarding an object for a long time — we explain many interesting phenomena of vision. If the eve be directed, for a time, to a white wafer, laid upon a black ground v 26^ULond ^ST* °f Physi°10^ ^ Ba'^ i ™d Carpenter's Human Physiology' p. Zbb, Lond. 1842. b 0p< citati 250> ' »J» 224 SENSE OF SIGHT. and afterwards to a sheet of white paper, it will seem to have a black spot, of the same size as the wafer upon it; the retina having become fatigued by looking at the white wafer. On the other hand, if the eye be turned to a black wafer, placed upon a sheet of white paper, and afterwards to another part of the sheet, a portion of the paper, of the size of the wafer, will appear strongly illuminated; — the ordinary degree of light appearing intense, when compared with the previous deficiency. It is on this, that the whole theory of accidental colours, as they are called, rests. When the eye has been, for some time, regarding a particular colour, the retina becomes insensible to this colour; and if, after- wards, it be turned to a sheet of white paper, the paper will not seem to be white, but will be of the colour, that arises from the union of all the rays of the solar spectrum, except the one to which the retina has become insensible. Thus, if the eye be directed for some time to a red wafer, the sheet of paper will seem to be of a bluish-green, in a circular spot of the same dimensions as the wafer. This bluish-green image is called an ocular spec- trum, because it is impressed upon the eye and may be retained for a short time; and the colour bluish-green is said to be the ac- cidental colour of the red. If this experiment be made with wafers of different colours, other accidental colours will be observed, varying with the colour of the wafer employed, as in the following table : — Colour of the Wafer. Red, .... Orange, - Yellow, .... Green, .... Blue, .... Indigo, .... Violet, .... Black, .... White, .... If all the colours of the spectrum be ranged in a circle, in the proportions they hold in the spectrum itself, as in the accompany- ing figure, — the accidental Accidental Colour, or Colour of the Ocular Spectrum. - Bluish-green. - Blue. Indigo. - Violet, with a little red. , - Orange-red. - Orange-yellow. - Yellow-green. - White. - Black. Fig. 45. range Black °SipUj Accidental Colours. colour of any particular co- lour will be found directly opposite. Hence the two colours have been termed opposite colours. It will follow, from what has been said, that if the pri- mary colour, or that to which the eye has been first directed, be added to the accidental colour, the result must be the same impression as that pro- duced by the union of all the rays of the spectrum — that POINT OF DISTINCT VISION. 225 «f tnh.Ui. light. The ac-iHontnl r.olour. in other words, is what the primitive colour requires to make it white light. The primitive and accidental colours are, therefore complements of each other ; and hence accidental colours have also been called complementary colours. They have likewise been termed harmonic, because the primitive and its accidental colour harmonize with each other in painting. It has been supposed, that the formation of these ocular spectra has frequently given rise to a belief in supernatural appear- ances ; the retina, in certain diseased states ofthe nervous system, being more than usually disposed to retain the impressions, s6 that the spectrum will remain visible for a long time after the cause his been removed. Such appears to be the views of Drs. Ferriar,a Hibbert,b and Alderson,c — the chief writers, in modern times, on apparitions. This subject may be the theme of future discussion. It may be sufficient at present, to remark, that the great seat and origin of spectral illusions is, in our opinion, the brain, and that the retina is no farther concerned than it is in dreaming or in the hallucinations of insanity. The retina is able to receive visual impressions over its whole surface, but not with equal distinctness or accuracy. When we regard an extensive prospect, that part of it alone is seen sharply, which falls upon the central part of the retina, or in the direction of the axis of the eye : we always, therefore, in our examination of minute objects, endeavour to cause the rays from them to impress this part of the retina; — the distinctness ofthe impression diminish- ing directly as the distance from the central foramen increases. This central point, called the point of distinct vision, is readily dis- criminated on looking at a printed page. It will be found that although the whole page is represented on the retina, the letter to which the axis of the eye is directed is alone sharply and distinctly seen; and, accordingly, the axis of the eye is directed in succession to each letter as we read. In making some experiments on indis- tinctness of vision, at a distance from the axis of the eye, Sir David Brewsterd observed a singular peculiarity of oblique vision, namely, — that when we shut one eye and direct the other to any fixed point, such as the head of a pin, and hence see all other objects within the sphere of vision indistinctly, — if one of these objects be a strip of white paper, or a pin lying upon a green cloth, after a short time, the strip of paper or the pin will altogether dis- appear, as if it were entirely removed — the impression of the green cloth upon the surrounding parts of the eye extending itself over the part of the retina, which the image of the pin occupied. In a short time, the vanished image will reappear, and again vanish. When the object, seen obliquely, is luminous, as a candle, it never vanishes entirely, unless its light is much weakened, by being placed at a great distance; but it swells, and contracts, and » An Essay towards a Theory of Apparitions, Lond. 1813. b Sketches of the Philosophy of Apparitions, Edinb. 1825. c An Essay on Apparitions, &c. Lond. 1823. a Qp. citat. p. 248. 226 SENSE OF SIGHT. is encircled with a nebulous halo; the luminous impressions ex- tending themselves to adjacent parts of the retina not directly in- fluenced by the light itself. From these, and other experiments of a similar character, Sir David infers, that oblique or indirect vision is inferior to direct vision, not only in distinctness, but from its inability to preserve a sustained vision of objects. Yet it is a singular fact, that the in- direct has a superiority over direct vision in the case of minute objects, such as small stars, which cannot, indeed, be seen by direct vision. It is a mode, frequently adopted by astronomers for obtaining a view of a star ofthe last degree of faintness, to direct the eye to another part of the field, and in this way, a faint star, in the neighbourhood of a large one, will often become very conspicuous, so as to bear a certain illumination, and yet it will entirely disap- pear, as if suddenly blotted out, when the eye is turned full upon it; and, in this way, it can be made to appear and disappear as often as the observer pleases. Sir J. F. W. Herschel and Sir James South, who describe this method of observation, attempt to account for the phenomenon, by supposing, that the lateral por- tions of the retina, being less fatigued by strong light, and less exhausted by perpetual attention, are probably more sensible to faint impressions than the central ones ; and the suggestion carries with it an air of verisimilitude. Sir David Brewster, however, — from the result developed by his experiments, that, " in the case of indirect vision, a luminous object does not vanish, but is seen indistinctly, and produces an enlarged image on the retina, beside that which is produced by the defect of convergency in the pen- cils," — concludes somewhat mystically, " that a star, seen indi- rectly, will affect a large portion of the retina from these two causes, and, losing its sharpness, will be more distinct."a In order that the image of any object may impress the retina, and be perceived by the mind, it must, first of all, occupy a space on the retina, sufficiently large for its various parts to be appre- ciated : in the next place, the image must be distinct or sharp ; in other words, the luminous rays that form it, must converge accu- rately to a focus on the retina : lastly, the image must be suffi- ciently illuminated. Each of these conditions varies with the size of the body, and the distance at which it is situate from the eye ; and there are cases, where they are all wanting, and where the object is consequently invisible. An object may be so small, that the eye cannot distinguish it; because the image, formed o'n the retina, is too minute. To remedy this inconvenience, the object must be brought near to the eye, which increases the divergence of the rays and the size of the image ; but if we approach it too close to the eye, the rays are not all brought to a focus on the retina, and the image is indistinct. If, therefore, an object be so small, that, at the visual point, to be presently mentioned, the rays, pro- ceeding from it, do not form an image of sufficient size on the a Op. chat. p. 249. DISTINCT VISION. 227 retina, the object is not seen. To obviate this imperfection ofthe sense, minute bodies may be viewed through a small hole in a piece of paper or card, or with the instrument called amicroscope. By looking through the small aperture in the paper or card, the object may be brought much nearer to the eye; the rays of greatest divergence are prevented by the smallness of the hole from im- pinging upon the retina ; and the rest are converged to a focus upon that membrane, so that a sharp and distinct impression is received. The iris is, in this way, useful in effecting distinct vision; the most divergent rays being — by its contracting the pupil — prevented from falling upon the crystalline. Any object, that does not subtend an angle of the sixtieth of a degree, is invisible ; but it is obvious that the visual power must differ greatly in individuals. Some eyes are much more capable of minute inspection than others; and a greater facility is acquired by practice. Ehrenberg, however, found, that in regard to the extreme limits of vision, there is little difference among persons of ordinarily good sight, whatever may be the focal distance of their eyes. The smallest square magnitude usually visible to the naked eye, either of white particles on a black ground, or of black upon a white ground, is about the -j^th of an inch; but particles, which reflect light powerfully, as gold dust, may be discovered with the naked eye, in common daylight, when not exceeding the TTVjth of an inch; and, when the substance viewed is in lines instead of par- ticles, it may be seen, if held toward the light, when only 4gVom of an inch in diameter.3 Again, there is a point of approximation to the eye beyond which objects cease to be distinctly seen, in consequence of the rays of light striking so divergently upon the eye, that the focus falls behind the retina. This point, too, varies according to the refractive power of the eye, and is therefore different in different individuals. In the myopic or short-sighted eye, it is much nearer the eye than common: in the presbyopic or long-sighted, more distant. The iris, here again, plays an important part, by its action in shutting off the most diverging rays, as above described. There is also a limit beyond which objects are no longer visible. This is owing to the light from the object becoming absorbed before it reaches the retina, or so feeble as not to make the necessary im- pression. The distance, consequently, at which an object may be seen, will depend upon the sensibility ofthe retina, and partly on the colour of the object; — a light colour being visible to a greater distance than a darker. A distant object may also be impercep- tible, owing to the image, traced on the retina, being too minute to be appreciated, for the image diminishes as the distance of the object increases. The range of distinct vision varies, likewise, with the individual, and especially with the myopic and presbyopic; and in such cases the pupil dilates to admit as much light as pos- sible into the interior ofthe eye, and to compensate in some mea- » Carpenter's Human Physiology, p. 264, Lond. 1842. 228 SENSE OF SIGHT. sure for the defect. Between the ranges of distant and near vision, a thousand different instances occur, which are seen more or less distinctly. In all cases, however, the ocular cone must be brought to a focus on the retina, otherwise there cannot be perfect vision. It has been already observed, in the proem on light, that the dis- tance, at which the ocular cone arrives at a focus behind the lens, is always in proportion to the length of the objective cone; or in other words, that the focus of a lens varies with the distance at which a radiant point is situate before it: where the radiant point is near the lens the focus will be more remote behind it, and the contrary. If this occur in the human eye it must necessarily follow ; —either that it is not necessary an object should be im- pressed upon the retina ; or that the eye is capable of accommo- dating itself to distances ; or if it do not occur, we must admit,. that, owing to the particular constitution of the eye, the impres- sions are duly made on the retina, without any necessity for such adaptation. The whole bent of the foregoing observations on vision would preclude the admission of the first of these postu- lates. The second has been of almost universal reception, and has given rise to many ingenious speculations ; and the third has been seriously urged of late years only. It would occupy too much space to dwell, at length, upon the various ingenious discussions, and the many interesting and curious experiments, that have resulted from a belief in the power pos- sessed by the eye of accommodating itself to distances. It is a subject, however, which occupies so large a field in the history of physiological opinions, that it cannot be wholly passed over. The chief views, that have been entertained upon the subject, are : — First. That the cornea or lens must recede from, or approach the retina, according to the focal distance, precisely as we adapt our telescopes, by lengthening or shortening the tube. Secondly. If we suppose the retina to be stationary, the lens must experience a change in its refractive powers, by an alteration of its shape or density; or, Thirdly. In viewing near objects, those rays only may be admitted, which are nearest to the axis of the eye, and which are consequently the least diverging. 1. The hypothesis, that the adjustment of the eye is dependent upon an alteration of the antero-posterior diameter of the organ, or on the relative position of the humours and retina, has been strongly supported by many able physiologists. Blumenbach3 was of opinion, and his views seem to have been embraced by Dr. Hosack,b that the four straight muscles of the eye, by com- pressing the eyeball, cause a protrusion of the cornea, and thus an increase in the length of the axis. Dr. Monro secundusc believed, that the iris, recti muscles, the two oblique, and the orbicularis palpebrarum have all their share in the accommodation; and * Instit. Physiolog. § 276, or Elliotson's translation. h Philosoph. Transact, for 1794, p. 196. c Three Treatises on the Brain, the Eye, the Ear, p. 137, Edinb. 1797. ADAPTATION OF THE EYE TO DISTANCES. 229 Hamberger, Briggs,a and others, that the oblique muscles, being thrown in opposite directions around it, may have the effect of elongating the axis of the eye. Keplerb thought, that the ciliary processes draw the crystalline forwards, and increase its distance from the retina. Descartesc imagined the same contraction and elongation to be effected by a muscularity of the crystalline, of which he supposed the ciliary processes to be the tendons. Por- terfield,d that the corpus ciliare is contractile, and capable of pro- ducing the same effect. Jacobson,e that the aqueous humour, by entering the canal of Petit, through the apertures in it, distends the canal, and pushes the crystalline forwards. Sir Everard Home,1 that the muscular fibres, which he has described as existing be- tween the ciliary processes, move the lens nearer to the retina, and that the lens is brought forward by other means, (which he leaves to conjecture,) when the distance of the object is such as to require its being so. Dr. Knox,? that the annulus albus, or the part which unites the choroid and sclerotic coats, is muscular, and the chief agent in this adjustment. Professor Mile,h of Warsaw, that the contraction of the iris changes the curvature of the cornea; whilst Sir David Brewster* thinks it "almost certain, that the lens is removed from the retina by the contraction of the'pupil." Without examining these and other views in detail, it may be remarked, that the nicest and most ingenious examination by the late Dr. Youngk could not detect any change in the length of the axis of the eyeball. To determine this, he fixed his eye, and at the same time forced in upon the ball the ring of a key, so as to cause a very accurately defined phantom to extend within the field of perfect vision; then looking to bodies at different distances, he expected, if the figure of the eye were modified, that the spot, caused by the pressure, would be altered in shape and dimensions; but no such effect occurred; the power of accommodation was as extensive as ever, and there was no perceptible change either in the size or figure of the oval spot. Sir Everard Home, again, asserts, that all the ingenuity of the distinguished mechanician, Ramsden, was unable to decide, whether, in the adjustment of the eye, there be any alteration produced in the curvature of the cor- nea. These facts would alone induce a doubt of the existence of this kind of adjustment, even if we had not the additional evidence, that many animals are incapable of altering the shape of the eye- ball, by the muscles at least. The cetacea and the ray amongst » Nova Visionis Theoria, Lond. 1685. b Haller, Element. Physiol, xvi. 4, 2. c Opera., Amstel. 1677. a A Treatise on the Eye, the Manner and Phenomena of Vision, Edinb. 1759. e Magendie's Precis, i. 78. f Philosoph. Transact for 1794, 1795,1796, and 1797; and Lectures on Compara- tive Anatomy, iii. 213, Lond. 1823. e Edinb. Philos. Transact, x. 56. b Magendie, Journal de Physiologie, vi. 166 ; aud Elliotson's Human Phvsioloev p. 571, Lond. 1840. J 5J' i Edinburgh Journal of Science, i. 77 ; and a Treatise on Optics, edit, citat. p. 253 * Philos. Transact, for 1795. VOL. I. — 20 230 SENSE OF SIGHT. fishes, and the lizard amongst reptiles, have the sclerotica so inflexible as to render any variation in it impossible. With regard to many of the particular views that have been mentioned, they are mere " cobwebs of the brain," and unworthy of serious argument. In the action of the orbicularis palpebrarum, as suggested by Dr. Monro, there is, however, something so plau- sible, that many persons have been misled by it. He made a set of experiments to show that this muscle, by compressing the eye- ball, causes the cornea to protrude, and thus enables the eye to see near objects more distinctly. When he opened his eyelids wide, and endeavoured to read letters, which were so near the eye as to be indistinct, he failed; but when he kept the head in the same relation to the book, and brought the edges of the eyelids within a quarter of an inch of each other, and then made an exer- tion to read, he found he could see the letters distinctly. But, on this experiment Sir Charles Bell3 properly remarks, that if the eye- lids have any effect upon the eyeball by their approximation, it must be to flatten the cornea; and that the improvement in near vision produced by such approximation, is owing to the most di- vergent rays being shut off, —as in the experiment ofthe pin-hole through paper, — and distinct vision being thus effected. 2. The second hypothesis, which attributes the adaptation to a change of figure in the crystalline itself, has been embraced by all those who regard that body to be muscular: and therefore by Leeuwenhoek and Descartes,b and more lately by Dr. Young.0 These muscular fibres, however, could never be excited by Dr. Young, so as to change the focal power; and their existence is more than doubtful. The increasing density of the lens towards the centre indicates rather a cellular structure, the cells being filled with transparent matter of various degrees of concentration ; and an examination into its intimate physical constituents affords no evidence of muscularity. It is somewhat singular, that on a subject where so many op- portunities have occurred for establishing the fact definitively, such difference of opinion should exist regarding the question, whether an eye from which the crystalline has been removed, as in the operation for cataract, be capable of adjusting itself to near objects. Amongst others, Hallerd and Knox decide the question affirma- tively ; Porterfield, Young, and Travers,e negatively. Magendie, as we have seen, considers the great use of the crystalline to be, — to increase the brightness and sharpness of the image by di- minishing its size. Mr. Travers again, regards adjustment as a change of figure in the lens ; not, however, from a contractile power in the part itself, but in consequence ofthe lamellae, of which it is composed, sliding over each other, when acted upon by exter- nal pressure : whilst upon the removal of this pressure, its elastic 1 Anat. and Physiology, Amer. Edit, by Dr. Godman, ii. 227, New York, 1827. b Boerhaav. Prselect. § 527, torn. iv. p. 92 ; and Haller, Element. Physiol, xvi. p. 2. c Op. citat. and Medical Literature, Lond. 1813. a Element. Physiol, xvi. 4. - A Synopsis ofthe Diseases ofthe Eye, Lond. 1824. ADAPTATION OF THE EYE TO DISTANCES. 231 nature restores it to its former sphericity. The iris is conceived to be the agent in this process ; the pupillary part of the organ being, in the opinion of Mr. Travers, a proper sphincter muscle, which, when it contracts and relaxes, will tend, by the intervention of the ciliary processes, to effect a change in the figure of the lens, which will produce a corresponding change in its refractive power. 3. One of the causes to which the faculty of seeing at different distances has been ascribed is the contraction and dilatation of the pupil. It has been already observed, that when we look at near objects, the pupil contracts, so that the most divergent rays do not penetrate the pupil, and the vision is distinct. Hence, it has been conceived probable —by De La Hire,3 Hallerb and others — that the adjustment of the eye to various distances, within the limits of distinct vision, may be effected by this mechanism, in the same manner as it regulates the quantity of light admitted into the inte- rior of the organ. Certain it is, that if we look at a row of minute objects, extending from the visual point outwards, the pupil is seen to dilate gradually as the axis of the eye recedes from the nearest object. An experiment made by the author, when a student of medicine, on his own eye,c has been quoted by Dr. Fleming,*1 as confirmatory of this view. The extract of belladonna has the power, when ap- plied to the eyelids, of dilating the pupil considerably. This was so applied, and in the space of about twenty minutes the pupil was so much dilated, that the iris was almost invisible. From the time that it became preternaturally dilated, objects, presented to this eye with the other closed, were seen as through a cloud. The focus was found to be at twice the distance of that ofthe sound organ ; but, in proportion as the effects of the belladonna went off, and the pupil approached its natural size, vision became more and more distinct, and the focus nearer than natural. In the open air, all objects except those near, were distinctly seen, but, on entering a room, all was enveloped in mist. There is, indeed, more evidence in favour ofthe utility of contraction and dilatation ofthe pupil in distinct vision, within certain limits at least, than of either of the other supposed methods of adjustment; and, accordingly, the majority of opticians of the present day embrace this view of the subject; but without being able to explain satisfactorily the change in the interior of the eye effected by its movements. " It seems difficult," says Sir David Brewstere — one ofthe latest wri- ters on this subject — " to avoid the conclusion, that the power of adjustment depends on the mechanism, which contracts and dilates the pupil; and as this adjustment is independent of the variation of its aperture, it must be effected by the parts in immediate con- tact with the base of the iris. By considering the various ways, in which the mechanism at the base of the iris may produce the adjustment, it appears to be almost certain, that the lens is removed » Memoir, de l'Acad. des Sciences, de Paris, torn. ix. h Element. Physiol, torn. v. lib. 16, 4. c Annals of Philosophy, x. 432, * Philosophy of Zoology, i. 187, Edinb. 1822. e Op. citat. p. 252. 232 SENSE OF SIGHT. from the retina by the contraction of the pupil." The conclusion, drawn by Sir David, does not, however, impress us with the same degree of certainty. Miiller3 thinks it most probable, that the faculty of the eye, which enables it to adjust itself to different distances, depends on an organ, which has a tendency to act by consent with the iris, but yet is in a certain degree independent of it. Reasoning per exclusionem, he thinks it certainly most probable, that the ciliary body has this motor power, and this influence on the position of the lens; but admits, that we have no positive proof of its possessing contractility. Pouillet, in his lectures before the Facult'e des Sciences of Paris,b explains the matter with no little confidence, by the double effect of the crystalline being composed of different layers, and the mobility ofthe pupil. These layers being thinner towards the axis of the crystalline than near its edges, by detaching them successively, the curvature of the remainder becomes greater and greater, until the most central portion has the shape of a sphere. Hence, he remarks, such an apparatus will not have one focus only, but several, — as many, in fact, as there are superposed layers; — the foci being nearer and nearer as we approach the central spherical portion. This arrangement, he says, enables us to see at all distances, inasmuch as, '• having an infinite number of foci at our disposal, we can use the focus that suits the object we are desirous of viewing." If, for example, it be a near object, the pupil contracts, so as to allow the rays to fall only on the central parts ; if more distant, the pupil is dilated to permit the rays to pass through a part that has a more distant focus. It is obvious, however, that in such a case, the ordinary inconvenience ofthe aberration of sphericity must result; as when the pupil is dilated, the rays must pass through the more marginal, as well as through the central part of the lens. Pouillet himself is aware of this difficulty, but he does not dispose of it phi- losophically. " It may besaid," he remarks, " that in opening the pupil widely, the light is not precluded from passing by the centre, and that a kind of curtain would be required to cover the part of the lens, which is unemployed. To this I reply, that there is no necessity to prevent the rays from passing by the axis of the crys- talline ; for, what is the light, which passes through this small space compared with that which passes through the great zone of the crystalline ? It may be looked upon as null." The whole affair, it must be admitted, is enveloped in perplexity, and it is rendered not the less so by the fact, mentioned by Magen- die, that if we take the eye of an albino animal, and direct it to- wards a luminous object, we find a perfect image depicted on the retina, whatever may be the distance of the object; — the image, of course, being smaller and less luminous when remote, but always distinct. Yet, in this experiment, the eye being dead, there could be neither contraction nor dilatation of the pupil. This result has * Elements of Physiology, by Baly, P. v. p. 1150, June, 1839. b See, also, his Elemens de Physique Experimentale, Paris, 1832, t. iii. p. 331. ADAPTATION OF THE EYE TO DISTANCES. 233 induced Magendie* — and not too hastily, we think — to draw the conclusion, that although theory may suggest, that there ought to be such adaptation, as has been presumed and attempted to be accounted for, observation proves, that this may not be the fact; and, consequently,all the speculations on the subject, however ingenious they may be, must fall to the ground. Dr. Fletcher, too, after alluding to the various hypothesis on the subject, adds, " It appears absurd to attempt to explain a fact which has no real existence, since it has never been proved that the eyeball has any capability of adapting itself to different distances, or that any such adaptation is required."b We are, indeed, not justified, perhaps, in admitting more than a slight accommodation from the contraction of the pupil in viewing near objects, effected in the mode already explained. If the accommodation existed to any material extent, it is difficult to understand, why slight cases of short or long-sightedness should not be rectified. Sir Charles Bellc conceives, " that the mechanism of the eye has not so great a power of adapting the eye to various distances as is generally imagined, and that much of the effect, at- tributed to mechanical powers, is the consequence of the motion of the pupil, the effect of light and of attention. An object looked upon, if not attended to, conveys no sensation to the mind. If one eye is weaker than the other, the object of the stronger eye alone is attended to, and the other is entirely neglected: if we look through a glass with one eye, the vision with the other is not at- tended to." " The mind," he adds, " not the eye, harmonizes with the state of sensation, brightening the objects to which we attend. In looking on a picture or panorama, we look to the, figures, and neglect the background; or we look to the general landscape, and do not perceive the near objects. It cannot be an adaptation ofthe eye, but an accommodation, and association ofthe mind with the state of the impression." The view, which we have expressed upon the subject, is strik- ingly confirmed by the calculations of M. De Simonoff,d a learned Russian astronomer, who asserts, that from a distance of four inches to infinity, the changes in the angle of refraction are so small that the apices of luminous cones, in a properly formed eye, must always fall within the substance of the retina, and hence no variation in the shape of the eye, according to the distance of the object, can be necessary. Such facts amply justify the interrogatory of Biote— whether the aberration of the focus for different distances may not be compen- sated, in the eye, by the intimate composition of the refractive bodies, as the aberration of sphericity probably is ? Yet, if this be the case, how admirable must be the construction of such an instru- ment 1 how far surpassing any effort of human ingenuity! an instru- * Precis Eltmentaire, i. 72. b Rudiments of Physiology, Part. iii. p. 48, Edinburgh, 1837. <= Anat. and Physiology, edit. cit. ii. 230. d Magendie's Journal de Physiologie, torn. iv. and Precis de Physiol, i. 73. e Traite de Physiologie Experimentale, Paris, 1816. 20* 234 SENSE OF SIGHT. ment capable of not only correcting its own aberration of sphericity, and its aberration of refrangibility, but of seeing at all distances.3 It has been before observed, that the visual point varies in dif- ferent individuals. As an average, it may be assumed at eight inches from the eye. There are many, however, who, either from original conformation of the organ, or from the progress of age, wander largely from this average; the two extremes constituting myopy or short-sightedness, and presbyopy or long-sightedness. In the myopy or short-sighted, the visual point is so close, that objects cannot be seen, unless brought near the eye. This defect is owing to too great a refractive Fig. 46. power in the transparent parts of the organ ; or to too great a depth of the humours; or it may be caused by unusual convexity of the cornea or crystalline ; or from the retina being too distant from the crystalline. From any Myopic vision. one or more of these causes, the rays of light, proceeding from distant objects, are brought to a focus before they reach the retina, and the objects consequently are not distinctly visible. (Fig. 46.) To see them distinctly, they must be placed close to the eye, in order that the rays may fall more divergently, and the focus be thrown farther back, so as to impinge upon the retina. The defect may be palliated by the use of concave glasses, which render the rays, proceeding from the object, more divergent. It is by no means unfrequent in youth; and the myope has been consoled with the common belief, that, in the progress of life, and in the alterations that take place in the eye from age, he is likely to see well without spectacles, when others of the same age may find them essential. It is probable, however, that this is, in many cases at least, a vulgar error ; as we have known different myopic sexa- genarians, who have not experienced the slightest improvement in the progress of age. Thepresbyope,presby tic ox long-sighted\ahouTsi\ndex an oxynosite defect. The visual point is much more distant than the average; and he is unable to see an ob- Fig. 47. ject unless it is at some dis- tance. This condition is owing to too feeble a refractive power in the transparent parts of the eye; toinsumcientdepthofthe eye; to too close an approxi- mation between the retina and crystalline: or to too little con- vexity of the cornea or crystalline ; so that the rays of light, pro- ceeding from a near object, are not rendered sufficiently conver- * Letters of Euler, by Sir D. Brewster, Amer. Edit. i. 163, New York, 1833. Presbyopic Vision. MYOPIC AND PRESBYOPIC EYE. 235 gent to impinge upon the retina, but fall behind it. This detect, which is experienced more or less by most people, after middle age, is palliated by the use of convex glasses, which render the rays, proceeding from an object, more convergent, and enable the eye to refract them to a focus farther forward, or on the retina. Although the presbyopic eye is unusual in youth, it is sometimes met with. A young friend, at ten or twelve years of age, was compelled to employ spectacles, adapted to advanced life; and this was the case with several of the members of a family, to whom the arts have been largely indebted in this country. One of them, at twenty, was compelled to wear spectacles which were almost microscopes. Both the myopic and the presbyopic conditions exist in a thou- sand degrees, and hence it is impossible to say, a priori, what is the precise lens, that will suit any particular individual. This must be decided by trial. The opticians have their spectacles arbitrarily numbered to suit different periods of life,'but each person should select for himself such as will enable him to read without effort at the usual distance. A degree of myopy may be brought on by long-protracted attention to minute and near objects ; as we ob- serve occasionally in the watchmaker and engraver ; and again, a person, who has been long in the habit of looking out for distant objects, as the sailor, or the watchman at the signal stations, is ren- dered less fitted for minute and near inspection. During the domi- nation of Napoleon, when the conscript laws were so oppressive, the young men frequently induced a myopic state of the eye, by the constant use of glasses of considerable concavity; this defect being esteemed a sufficient ground of exemption from military service. Another question, which has given rise to much disputation and experiment is, why, as we have two eyes, and the image of an object is impressed upon each of them, we do not see such object double ? Smith3 and Buffonb consider, that in infancy we do see it double ; and that it is not until we have learned by experience, — by the sense of touch for example, — that one object only exists, that we acquire the power of single vision. After the mind has thus become instructed of its error, a habit of rectification is attained, until it is ultimately effected unconsciously. The objections to this hypothesis are many and cogent. We are not aware of any in- stance on record, in which double vision has been observed to occur in those, who, having laboured under cataract from birth, have received their sight by an operation; and we are obviously precluded from knowing the state of vision in the infant, although the simultaneous and parallel motions ofthe eyes, which is mani- festly instinctive, and not dependent upon habit, would induce us to presume, that the images of objects — as soon as the parts have attained the necessary degree of development — are made to fall upon corresponding parts of the retina. It may, also, be remarked, 1 Optics, Cambridge, 1738. b Meraoir.de l'Academ. des Sciences, 1743. 236 SENSE OF SIGHT. in favour of the instinctive nature of this parallel motion of the eyes, that in the blind, —although we may find much irregularity in the motions of the eyeball, owing to no necessity existing for the eyes being directed to any particular point, — the eyeballs move together, unless some deranging influence be exerted. The truth is, as we have already observed, the encephalon is compelled to receive the impression as it is conveyed to it; and even in cases, in which we are aware of an illusion, the perception of the illusion still exists in spite of all experience. If the finger be pressed on one side of the eyeball, an object, seen in front, will appear double, and the perception of two objects will be made in the brain, although we know from experience, that one only exists. This oc- curs in all the various optical illusions to be presently mentioned. The effect of intoxication has been adduced in favour of this hypothesis. It is said that, in these cases, the usual train of mental associations is broken in upon, and hence double vision results. The proper explanation^ however, of this diplopia of the drunkard rests upon other grounds. The effects of inebriating substances on the brain are, to interfere with all the functions of that organ ; and most sensibly with the voluntary motions, which become irregu- larly executed. The voluntary muscles of the eye partake of this vacillation, and do not move in harmony, so that the impressions are not made on corresponding points of the retina, and double vision necessarily results. Another hypothesis has been, that although a separate impres- sion is made upon each retina, — in consequence of the union of the optic nerves, the impressions are amalgamated, and arrive at the encephalon, so as to produce but one perception. This was the opinion of Briggs,3 and Ackermann, and at one time it was generally received. Dr. Wollastonb supposed the consentaneous motion of the eyes to be connected with the partial union of the optic nerves. The anatomical and physiological facts, relating to' the union and decussation of these nerves have already engaged us. By a reference to that subject it will be found, that a true de- cussation takes place between them, yet that each eye has, proba- bly, its distinct nerve from origin to termination; and that no such semi-decussation, as that contended for by Dr. Wollaston, probably exists. These facts are unfavourable to this hypothesis of amalga- mation of impressions ; and, besides, if we press slightly on the eye, we have a double impression, although the relation of the optic nerves to each other is the same ; and, moreover, the same explanation ought to apply to audition, in which we have two distinct impressions, but only a single perception : — yet no one conceives that the auditory nerves decussate. The fusion of the two images into one seems to be entirely a mental operation.6 Another opinion has been maintained;—that we do not actually receive the perception of two impressions at the same time, but that a Nova Visionis Theoria, Lond. 1685. b Philos. Transact, for 1824, p. 222. c Carpenter's Human Physiology, § 338, Lond. 1842. SINGLE VISION. 237 vision consists in a rapid alternation of the eyes, according as the attention is directed to one or other of them by accidental circum- stances. Such was the opinion of Dutours.3 A modification of this view was entertained by Le Cat,b who asserts, that, although the right eye is not always the most powerful, it is the most fre- quently employed; and Gall openly denies, that we use both eyes at the same time, except in the passive exercise of the function. In active vision, he asserts, we always employ one eye only, — sometimes the one and sometimes the other; and thus, as we receive but one impression, we necessarily see but one object. In support of this view, he remarks, that, in many animals, the eyes are situate at the sides of the head, so as not to be capable of being directed together to the same object. In them, consequently, one eye can alone be used; and he considers this a presumption that such is the case in man. He remarks farther, that in many cases we use one eye by preference, in order that we may see better; as in shooting or in taking the direction of objects in a straight line, &c.; and that although, in other cases, both eyes may be open, we still use but one. In proof of this, he says, if we place a small object between the eyes and a lighted body, and look at the latter, the shade does not fall between the eyes, on the root of the nose, as it ought to do if the body were regarded with both eyes, but on each eye alternately, according as the one or the other is directed to it; and, he adds, if, when we squint voluntarily, we see two objects, it is because one eye sees passively, whilst the other is in activity.0 Amongst the numerous objections to this view of the subject, a few may be sufficient. Every one must have observed how much more vividly an object is seen with both eyes than with one only. The difference indeed according to Jurind is a constant quantity ; and, in sound eyes of the ordinary degree of power, amounts to one-thirteenth of the whole effect. But we have experiment to show that a distinct impression is made upon each eye. If a solar beam be admitted into a dark chamber, and be made to pass through two glasses of tolerable thickness, but of different colours, placed close alongside each other, provided the sight be good, and the eyes of equal power, the light, which is perceived, will not be of the colour of either of the glasses, but will be of an intermediate shade ; and, when this does not happen, it will be found that the eyes are of unequal power. When such is the case, the light will be of the colour of the glass that is placed before the stronger eye. These results were obtained in the Cabinet de Physique of the Faculti de Medecine of Paris, by M. Magendie/ in the presence of M. Tillaye the younger. * Memoir, presentees a l'Academie des Sciences, &c. t. iii. and iv. b Op. citat. e Adelon, Physiologie, 2de edit. i. 457, Paris, 1829. d Essay appended to Smith's Optics, Cambridge, 1738 ; and Haller, Element. Physiol, lib. xvi. 4. 6 Precis, &c. i. 86. See, also, Dutours, in Mem. presentees a 1'Academ. iii. 514, and iv. 499. 238 SENSE OF SIGHT. The existence of this double impression is proved in another way. If we place any tall, slender object a few feet before us, and examine its relative situation, compared with a spot on a wall in the distance, we find, that if the spot be hidden by the stick, when both eyes are open, it will become visible to each eye, when used singly ; and will be seen on the side of the stick corresponding to the eye that is employed. But Prof. Wheatstone3 has instituted experiments, which place this matter entirely at rest. He has shown, that in viewing an object having length, breadth and thick- ness, the perspective projections upon the two retinae differ ac- cording to the distance at which the object is placed before the eyes. If it be placed so distant, that to view it, the optic axis must be parallel, the two projections are precisely similar ; but if it be placed so near, that to view it, the optic axis must converge, a different perspective projection is presented to each eye, and these perspectives become more dissimilar as the convergence ofthe optic axis becomes greater. Notwithstanding this dissimilarity between the two pictures, which is in some cases very great, the object is still seen single, although not exactly resembling either of the two pictures on the retinas. Having thus established, that the mind perceives an object of three dimensions by means of the two dis- similar pictures projected by it on the two retinas, Mr. Wheatstone inquired, what would be the visual effect of presenting simulta- neously to each eye, instead of the object itself, its projection on a plane surface as it appears to that eye ? For this purpose he in- vented an instrument which he calls a stereoscope. It consists of two plane mirrors, with their backs inclined to each other at an angle of 90°, near the faces of which two monocular pictures are so disposed, that their reflected images are seen by the two eyes, each looking into one of the mirrors on the same place. The experiment may, however, be sufficiently well made by the sub- joined figures. Fiff. 48. Fix the right eye on the right-hand figure, and the left eye on the left-hand figure ; hold between the eyes, in front of the nose, the board of an octavo book. The two figures will be seen to approximate, and then run into one, representing the skeleton of a truncated four-sided figure in bold relief; a fact, which shows, that the visual appreciation of solidity or projection arises from * Philosophical Transactions, P. ii. Lond. 1838. SINGLE VISION. 239 the combination in the mind of two different images. These could not exist in a person who has never had more than one eye, and therefore from sight alone he could form no notion of solidity. He would have to combine with sight the evidence afforded by touch. All these facts signally demonstrate, that two impressions are really made in all cases, — one on each eye ; — and yet the brain has perception of but one. If the law of visible direction, which Sir David Brewster has pointed out (see page 221), be adopted, the cause of single vision with two eyes must be admitted as a necessary consequence of it. If we are placed at one end of a room, and direct the axis of both eyes to a circular aperture in a window-shutter at the other end, although an image of this aper- ture may be formed in each eye, yet because the lines of visible direction from similar points of the one image meet the lines of visible direction from similar points of the other image, each pair of similar points will appear as one point, and the aperture seen by one eye will exactly coincide with the aperture seen by the other eye. But if, when an object is seen single with both eyes, we press one eye aside, the image formed by that eye will separate from the other image, and the object will appear double; or, if the axis of both eyes be directed to a point either nearer or more remote than the aperture in the window-shutter, then, in both of these cases, the aperture will appear double, because the similar lines of visi- ble direction no longer meet at the aperture.a After all, perhaps, the true condition of single vision is, that the two images of an object should be formed on portions of the two retinae that are ac- customed to act in concert. In cases of convergent strabismus,-the patient does not see double ; but immediately after a successful operation, if the vision of the two eyes be good, he does so ; and this continues until the parts of the two retinas have become habi- tuated to act in concert.b In the course of the preceding remarks, it was stated, that the eyes are not always ofthe same power. The difference is, in- deed, sometimes surprising. M. Adelon0 mentions the case of a person, one of whose eyes required a convex glass, with a focus of five inches; the other a concave glass, with a focus of four inches. In these cases, it is important to use one unassisted eye only; as confusion must necessarily arise from directing both to an object. This is the cause why we close one eye in looking through a tele- scope. The instrument has the effect of rendering the focal dis- tance of the two eyes unequal, and of placing them in the same situation as if they were, originally, of different powers. From what has been said it will be understood, that if from any cause, as from a tumour pressing upon one eyeball, from a morbid debility of the muscles, or from a want of correspondence in the » Optics, p. 44, in Library of Useful Knowledge, Natural Philosophy, vol. i. Lond. 1829, and Treatise on Optics, edit. cit. i> Carpenter's Human Physiology, § 253 and 337, Lond. 1842. e Physiologie, edit. cit. i. 459. 240 SENSE OF SIGHT. sensibility of the two retinas, the eyes be not properly directed to an object, double vision will be the consequence. In almost all casea, however, of distortion ofthe eyeballs, the image will fall upon a part of»one retina, which is more sensible than the portion of the other on which it impinges; the consequence will be, that the mind will acquire the habit of attending to the impression on one eye only; and the other will be so neglected, that it will assume a position to interfere as little as possible with the vision of its fellow — so that, although at first, in squinting, there may be a double impression, vision is ultimately single. Buffon,a who was of this opinion, affirms, that he examined the eyes of many squinters, and found that they were of unequal power; the weaker, in all cases, having turned away from its direction, and generally towards the nose, in order that fewer rays might reach it, and consequently vision be less interfered with. Yet it is always found, if the sound eye be closed, that the other resumes its proper direction ; a fact, which disproves the idea of De La Hire and others, that the cause of strabismus or squinting is a difference of sensibility in the corre- sponding points of the retinae, and that the discordance in the move- ments of the organs occurs, in order that the images may still fall upon points of the retinas, that are equally sensible. According to this view, both eyes must of course act. The fact of the diverted eye resuming its proper direction, when the sound one is closed, is of important practical application. Many ofthe cases of squinting, which occur in infancy, have been induced by irregular action in the muscles of the eyeball; so that some, from accident or from imitation, having been used more frequently than others, the due equilibrium has not beeti maintained ; double vision has resulted; and the affected eye has gradually attained its full obliquity. In these cases, we can, at times, remedy the defect, by placing a bright or conspicuous object in such a position as to exercise the enfeebled muscles ; or, we can compel the whole la- bour of vision to be effected by one eye, and that the affected one, which, under the stimulus, will be correctly exerted, and thus, by perseverance, the inequality may often be obviated. These indeed are the only cases in which we can expect to afford relief; for if the defect be in the interior of the eye, in a radical want of corre- spondence between the retinas, or in inequality of the foci, it is irremediable. It would appear, then, that in confirmed squinting, one eye is mainly, if not solely used, and that vision is single, — that the in- clination of one eye inwards may be so great as to deprive it of function, or so slight as to allow the organ to receive rays from the same object as its fellow; but, in either case, it would seem, that they, who squint habitually, neglect the impressions on the dis- torted eye, and see with but one. We have said, that the eyeball of the imperfect eye is drawn 1 Mem de l'Academie, 1743. b Ibid, tom.ix. 530; also, Jurin, in Essay appended to Smith's Optics, § 178-194. MULTIPLE VISION WITH ONE EYE. 241 towards the nose, in order that as few rays as possible may pene- trate the organ; and the vision of the sound eye be less liable to confusion. Sir Everard Home,3 however, conceives, that it takes this direction in consequence of the adductor muscle being stronger, shorter, and its course more in a straight line than that of any of the other muscles of the eye ; and Sir Charles Bellb ingeniously applies his classification of the muscles of the eye to an explanation of the same fact. He asserts, that the recti muscles of the eyeball are in activity during attention to the impression on the retina, — but that when the attention is withdrawn, the straight muscles are relieved, and the eyeball is given up to the influence of the oblique muscles, the state of equilibrium between which exists, when the eyeball is turned, and the pupil presented upwards and inwards. Lastly, in persons who are in the habit of taking repeated celes- tial observations, or in those who make much use of the micro- scope, the attention is so entirely directed to one eye, that the other is neglected, and, in time, wanders about, so as to produce squint- ing at the pleasure of the individual. In these cases, the eyes be- come of unequal power, so that one only can be employed where distinct vision is required. So far our remarks have been directed to double vision, where both eyes are employed. We have now to mention a very singu- lar fact connected with double and multiple vision with one eye only. If a hair, a needle, or any small object be held before one eye —the other being closed — and within the point of distinct vision, so that the bright light of a lamp or from a window shall fall upon the object, in its passage to the eye, or be reflected from it, we appear to see "riot one object but many. This fact, when it was first observed by the author, appeared to him to have entirely escaped the observation of opticians and physiologists, inasmuch as it had not been noticed in any of the works recently published on optics or physiology. On reference, however, to the excellent " system," of Smith,0 on the former subject, he found in the " Essay upon Distinct and Indistinct Vision," by Dr. Jurin, appended to that work, the whole phenomenon explained, and elucidated at con- siderable length. The elaborate character of the explanation is probably the cause, why the fact has not been noticed by subse- quent writers. The best way of trying the experiment is that suggested by Jurin. Take a parallel ruler, and opening it slightly, hold it directly before the eye, so as to look at a window or lamp through the aperture. If the ruler be held at the visual point, the aperture will appear to form one luminous line ; but if it be brought nearer to the eye, it will appear double, or as two luminous lines, with a dark line between them; and according as the aperture is varied — or the distance from the eye — two, three, four, five or more luminous and dark parallel lines will be perceptible. » Philos. Transact. 1797, and Lectures on Comparative Anatomy, iii. 238, Lond. 1823 b AnaU and Physiol, edit. cit. ii. 235. c Optics, edit, citat, VOL. I. — 21 242 SENSE OF SIGHT. At first sight, it might seem, that this phenomenon should be referred to the diffraction or inflection, which the light experiences in passing by the edges of the small body, — as the hair or needle. Newton had long ago shown, that, when a beam of light shines upon a hair, the hair will cast several distinct shadows upon a screen, and will, of course, present several images to the eye. Dr. Rittenhouse,3 explains, on the same principle, a very curious optical appearance, noticed by Mr. Hopkinson, in which, by the inflection of light, caused by the threads of a silk handkerchief, a multiple image of a distant lamp was presented. The objections, however, to the ex- planation by inflection are, — that the image always appears single, if the object be not within the distance of distinct vision; and, secondly, the same multiple image is presented, when the object is seen by reflection, as when we look at a fine line, drawn upon paper; or at a fine needle held in a bright light. In this case, a considerable number of parallel images of the needle may be seen, all equally or nearly equally distinct, and not coloured. Dr. Jurin considers the phenomena to be caused by fits of easy refraction and reflection of light. Newton demonstrated, that the rays of light are not, in all parts of their progress, in the same dis- position to be transmitted from one transparent medium into another ; and that sometimes a ray, which is transmitted through the surface of the second medium, would be reflected back from that surface, if the ray had a little farther to go before it im- pinged upon it. This change of disposition in the rays, — to be either transmitted by refraction, or to be reflected by the surface of a transparent medium, — he called their fits of easy refrac- tion, and fits of easy reflection; and he showed, that these fits succeed each other alternately at very small intervals in the pro- gress of the rays. Newton does not attempt to explain the origin of these fits, or the cause that produces them ; but it has been suggested, that a tolerable idea of them may be formed by supposing, that each particle of light, after its emanation from a body, revolves round an axis perpendicular to the direction of its motion, and presents alternately to the line of its motion an attractive and a repulsive pole, in virtue of which it will be refracted, if the attractive pole be nearest any refracting surface on which it falls, and reflected, if the repulsive pole be nearest the surface. A less scientific notion of the hypothesis has also been sug- gested ; by supposing a body with a sharp and a blunt end passing through space, and successively presenting its sharp and blunt ends to the line of its motion. When the sharp end encounters any soft body it penetrates it: but when the blunt end encounters the same body, it will be reflected or driven back. In applying this to the phenomenon in question, Jurin presumes, that the light, in passing through the humours of the eye, experiences Jhese fits of easy refraction and easy reflection. This will be ' Amer. Philos. Transact, vol. ii. MULTIPLE VISION WITH ONE EYE. 243 Fig. 49. understood by the marginal figure, Fig. 49. Suppose a num- ber of rays of light to proceed from the point A, and to impinge, with dif- ferent degrees of obliquity, on the denser medium, B C; all the rays which are in fits of easy refraction, will pass through the medium to the point D ; whilst those that are in fits of easy reflec- tion, will be thrown back into the medium A B C; so that we may presume, that all the rays, which fall upon the parts of the medium B C, corresponding to the bases of the dark cones will be reflected back, whilst those that correspond to the bases of the light cones, will pass to a focus at D. Now, if all the bundles of rays, transmitted through the surface B C, be accurately collected into a focus, no other consequence will arise from the other bun- dles of rays having been reflected back, than that the focus will be less luminous than it would have been had all the rays been trans- mitted through it. This explains why, at the distance of distinct vision, we have only a single impression made on the eye. But if we approach the object A, so that the focus is not thrown, — say upon the screen R T, which may be presumed to represent the retina — but behind it; the dark and light spaces will be represented upon the screen, and, of course, in concen- tric circles. This happens to the eye, when the hair or needle or other object is brought nearer to it than the visual point. We can thus understand, why concentric circles, of the nature men- tioned, should be formed upon the retina; but how is it, that the objects seen pre- serve their linear form ? Suppose a b, Fig. 50, to be a luminous cone, which in a fit of easy refraction has impinged upon the retina: and A B, b a, the concentric circles, corresponding to the rays that have been reflected. It is obvious, that every point of the object will be the centre of so many concentric 244 SENSE OF SIGHT. circles on the retina; and if we imagine the fits of easy reflection and refraction to be the same around those points, we shall have the dark and lucid lines represented by the tangents to these cir- cles ; and hence we can comprehend why, instead of having one lucid line e f, we have three, separated by dark lines parallel to them ; and if the light from the luminous point be strong enough to form more lucid rings than are represented in Fig. 50, and the breadth of those rings be not too minute to be perceived, we may have the appearance of five, seven, or more lucid lines, separated by parallel dark lines. We proceed now to consider the advantages, which the mind derives from the possession of this sense, so pre-eminently entitled to the epithet intellectual. Its immediate function is to give us the sensation of light and colour. In this it cannot be supplied by any of the other senses. The action is, therefore, the result of organization; or is a " law of the constitution ;" requires no education ; but is exercised as soon as the organ has acquired the proper development. Yet, occasionally, we meet with singular cases, in which the eye appears to be totally insensible to certain colours, although capable of performing the most delicate functions of vision. Sir David Brewster3 has collected several of these cases from various sources. A shoemaker, of the name of Harris, at Allonby, in Cumberland, could only distinguish black and ivhite ; and, whilst a child, could not discriminate the cherries on a tree from the leaves, except by their shape and size. Two of his brothers were almost equally defective. One of them constantly mistook orange for grass green, and light green for yellow. A Mr. Scott, who describes his own case,b mistook pink for a pale blue, and a full red fox a full green. His father, his maternal uncle, one of his sisters, and her two sons, had all the same defect. A Mr. R. Tucker, son of Dr. Tucker, of Ashburton, mistakes orange for green, like one of the Harrises ; and cannot distinguish blue from pink, but almost always knows yellow. He mistakes red fox brown, orange for green, and indigo and violet for purple. A tailor at Plymouth, whose case isdescribed by Mr. Harvey,c of Ply- mouth, regarded the solar spectrum as consisting only of yellow and light blue ; and he could distinguish, with certainty, only yel- low, ivhite and gray. He regarded indigo and Prussian blue as black, and purple as a modification of blue. Green puzzled him exceedingly; the darker kinds appearing to him brown, and the lighter kinds a pale orange. On one occasion, he repaired an article of dress with crimson instead of black silk; and on another occa- sion patched the elbow of a blue coat with a piece of crimson cloth. A still more striking case is given by Dr. Nichollsd of a a Optics, edit. cit.; Letters on Natural Magic; and art. Optics, in Library of Useful Knowledge. » Philos. Trans, for 1778. c Edinb. Phil. Transact, x. 253, a Medico-Chirurgical Trans, vii. 477, ix. 359. INSENSIBILITY OF THE EYE TO COLOURS. 245 person in the British navy, who purchased a blue uniform coat and waistcoat, with red breeches to match. Sir David Brewster refers to a case that fell under his own observation, where the gentleman saw only the yellow and blue colours of the spectrum. This defect was experienced by Mr. Dugald Stewart,3 who was unable to perceive any difference between the colour ofthe scarlet fruit of the Siberian crab and that of its leaves. Dr. Dalton,b the chemist and philosopher, could not distinguish blue from pink by daylight; and, in the solar spectrum, the red was scarcely visible ; the rest of it appearing to consist of two colours, yellow and blue. Mr. Troughton, the optician, was fully capable of ap- preciating only blue and yellow ; and when he named colours, the terms blue and yellow corresponded to the more or less refrangible rayS : _ all those that belong to the former, exciting the sensation of blueness ; and those that belong to the latter, that of yellowness. Dr. Hays,c who has collected the history of numerous cases of achromatopsia, — as this defect has been termed, — and has added the history of one which fell under his own care,d was led to infer, from all his researches: 1, that entire inability of distinguishing colours may co-exist with perfect ability to perceive the forms of objects; 2, that the defect may extend to all but one colour, and in such case the colour recognised is always yellow ; and, 3, that the defect may extend to all but two colours, and in such case the colours recognised are always yellow and blue. The opinions of philosophers have varied regarding the cause of this singular defect in eyes otherwise sound, and capable of per- forming every other function of vision in the most delicate and accurate manner. By some, it has been presumed to arise from a deficiency in the visual organ ; and by such as consider the ear to be defective in function in those that are incapable of appreciating musical tones, this deficiency in the eye is conceived to be of an analogous nature. " In the sense of vision," says Dr. Bro wn,e " there is a species of defect very analogous to the want of musical ear, — a defect which consists in the difficulty, or rather the incapacity of distinguishing some colours from each other —and colours which, to general observers, seem of a very opposite kind. As the want of musical ear implies no general defect of mere quickness of hear- ing, this visual defect, in like manner, is to be found in persons who are yet capable of distinguishing, with perfect accuracy, the form, and the greater or less brilliancy of the coloured object; and I may a Elements of the Philosophy ofthe Human Mind, ch. iii. i> Manchester Memoirs, v. 28. c Proceedings ofthe American Philosophical Society for August 21,1840 ; and his edit, of Lawrence on Diseases of the Eye, Philad. 1843. a Amer. Journal of the Medical Sciences, August, 1840, p. 277. See, also, on this subject, Seebeck, in PuggendorPs Annalen., 42; and Muller's Physiology, by Baly, p 1213, Part v. Lond. 1839; also, Victor Szokalski, in Bullet. Med. Beige, Fevrier, 1840, p! 35, Mars, 1840, p. 64, Avril, 1840, p. 98, and Mai, 1840, p. 129; Elliotson's Human Physiology, p. 582, Lond. 1840. * Lectures on the Philosophy of the Human Mind, vol. i., Boston, 1826. 21* 246 SENSE OF SIGHT. remark, too, in confirmation of the opinion, that the want of musi- cal tone depends on causes not mental but organic, that in this ana- logous case some attempts, not absolutely unsuccessful, have been made to explain the apparent confusion of colours by certain pecu- liarities of the external organ of sight." Dr. Dalton, who believed the affection to be seated in the physical part of the organ, has en- deavoured to explain his own case, by supposing that the vitreous humour is blue, and therefore absorbs a great portion of the red and other least refrangible rays; and Sir David Brewster, in the Library of Useful Knowledge? appears to think that it may depend upon a want of sensibility in the retinas, similar to that observed in the ears of those who are incapable of hearing notes above a certain pitch ; but as this view is not contained in his more recent Treatise on Optics, it is probably no longer considered by him to be satis- factory. The defect in question—difficult as it is to compre- hend — has always appeared to the author to be entirely cerebral, and to strikingly resemble, as Dr. Brown has suggested, the " want of musical ear." As we have already endeavoured to establish that the latter is dependent upon a defective mental appreciation, the parity ofthe two cases will, of course, compel us to refer the visual defect, or the want ofthe " faculty of colouring," to the same cause. It has been remarked, that the eye in these cases exercises its function perfectly, as regards the form and position of objects, and the degree of illumination of their different portions. The only defect is in the imperfect conception of colour. The nerve of sight is probably accurately impressed, and the deficiency is in the part of the brain whither the impression is conveyed, and where perception is effected, which is incapable of accurately appre- ciating those differences between rays, on which their colour rests; and this we are glad to find is the view taken of it by one of the most eminent philosophers of the present day, Sir J. F. W. Herschel.b The mediate or auxiliary functions of vision are numerous; and hence, the elevated rank that has been assigned to this sense. By it, we are capable of judging, to a certain extent, of the direc- tion, position, magnitude, distance, surface, and motion of bodies. Metaphysicians have differed greatly in their views on this sub- ject ; the majority believing, that, without the sense of touch, the eye is incapable of forming any accurate judgment on these points; others, that the sense of touch is no farther necessary than as an auxiliary; and that a correct appreciation could be formed by sight alone. The few remarks that may be necessary on this subject, will be deferred until the physical and other circumstances, which enable us to judge of distance, &c, have been canvassed. The direction ox position of objects has already been considered, 1 Natural Philosophy, vol. i. — Optics, p. 50, Lond. 1829. b Encyclopaedia Metropolitana, art. Light. APPRECIATION OF DISTANCES. 247 so far as regards the inverted image formed by them on the retina. The errors that arise on this point are by no means numerous, and seldom give rise to much inconvenience, yet, whenever the lumi- nous cone meets with reflection or refraction, before reaching the eye, the retina conveys erroneous information to the sensorium, and we experience an optical illusion. To ascertain the magnitude, distance, and surface of bodies, we are obliged to take into consideration several circumstances con- nected with the appearance of the object, — such as its apparent size, the intensity of light, shade, and colour, the convergence of the axes of the eyes, the size or position of intervening objects, &c. Porterfield3 enumerates six methods, which are employed in ap- preciating distance — 1. The apparent magnitude of objects; 2. The vivacity of their colours ; 3. The distinction of their smaller parts; 4. The necessary conformation of the eyes for seeing dis- tinctly at different distances ; 5. The direction of their axes; and 6. The interposition of objects. Dr. Brownb reduces them to three — 1. The difference of the affections of the optic nerve; 2. The different affections of the muscles, employed in varying the refract- ing power of each eye, according to the distance of objects, and in producing that particular inclination of the axes of the two eyes which directs them both equally on the particular object; and 3. The previous knowledge of the distance of other objects, " which form, with that we are considering, a part of one compound per- ception." Lastly, Dr. Arnott0 enumerates four modes by which this is effected — 1. The space and Fig. 51. place, occupied by objects in the field of view, y, measured by what o I is termed the vi- w sual angle. 2. The intensity of light, shade, and colour. 3. The divergence of the rays of light — and 4. The convergence of the axes of the eyes. This enumeration may be adopted with some slight modifications. The circumstances, in our opinion, to be con- sidered, are : — 1. The visual angle, or that formed by two lines, which shave the extremities of an object and cross at the centre of the crystal- line ; so that the visual angle, subtended by the object, as a d, Fig. 51, is exactly equal to that subtended by its image i u on the re- tina. It is obvious, from this figure, that if all objects were equi- a A Treatise on the Eye, ii. 409. Lond. 1759. b Lectures on the Philosophy of the Human Mind, vol. i. Boston, 1826. c Elements of Physics, new Amer. Edit. Philad. 1841. 248 SENSE OF SIGHT. distant from the eye, and ofthe same magnitude, they would subtend the same angle ; and if not of the same magnitude, the difference would be accurately indicated by the difference in the visual angle subtended by them ; thus, the comparative size of the two crosses a d and b d is represented by that of the images i u and i o. The cross c e, however, which is twice the size of b d, subtends the same visual angle, and is alike represented on the retina by the image i o. It is clear, then, that the visual angle does not, under such circumstances, give us a correct idea of the relative magni- tudes of bodies, unless we are acquainted with their respective distances from the eye ; and, conversely, we cannot judge accu- rately of their distances, without being aware of their magnitudes. A man on horseback, when near us, subtends a certain visual angle, but, as he recedes from us, the angle becomes less and less; yet we always judge accurately of his size, because aware of it by experience ; but if objects are at a great distance, so as not to admit of their being compared with nearer objects by simple vision, we are in a constant state of illusion — irresistibly believing, that they are much smaller than they really are. This is the case with the heavenly bodies. The head of a pin held close to the eye will sub- tend as large a visual angle as the planet Jupiter, which is one thou- sand two hundred and eighty-one times bigger than this earth, and is eighty-six thousand miles in diameter. In like manner, a five- cent piece, held at some distance from the eye, will shut off the sun, although its diameter is eight hundred and eighty-eight thousand miles. The sun and moon, again, by subtending nearly the same visual angle, appear to us of nearly the same size ; and the illusion persists in spite of our being aware of the mathematical accuracy, with which it has been determined, that the former is ninety-six millions of miles from us, and the latter only two hundred and forty thousand. The visual angle, again, subtended by an object, differs greatly according to the position of the. object. A sphere has the same appearance or bulk, when held at'a certain distance from the eye, whatever may be the position in which it is viewed; and, ac- cordingly, the visual angle, subtended by it, is always identical. Not so, however, with an oval. If held, so that the rays from one of its ends shall impress the eye, it will occasion a circular image, and subtend a much smaller angle than if viewed sideways, when the image will be elliptical, or oval. The same thing must occur with every object, whose longitudinal and transverse diameters differ. It is obvious, that if any such object be held in a sloping position to- wards the eye, it will appear more or less shortened; precisely in the same manner as the slope of a mountain or inclined plane would appear much greater, if placed perpendicularly before the eye. This appearance is what is called foreshortening ; and it may be eluci- dated by the following figure. Suppose a man to be standing on a level plain, with his eye at c (Fig. 52), looking down on the plain. The portion of the surface a d, which is next to him, will be seen with- APPRECIATION OF DISTANCES. 249 Fig. 52. out any foreshortening; but if we suppose him to regard successively the portions dfifg, and g b of the plain, the angle, subtended by each portion, will di- minish ; so that if the angle a c d be 45°, d c /will be 18°; fcg 8°, and so on; until, at length, the obliquity will be so great, that the angle becomes inappreciable. This is the cause why, if we look obliquely upon a long avenue of trees, we are unable to see the intervals between the farthest in the series; although that between the nearest to us may be readily distin- guished. In all paintings, of animals especially, the principle of foreshortening has to be rigidly attended to : and it is owing to a neglect of this, that we see such numerous distorted representa- tions — of the human figure particularly. It has been already stated, that objects appear smaller according to their distance ; hence, the houses of a street, or the trees of an avenue, that are nearest to us, or in the foreground, will form the F'g- 53- largest images on the re- tina, and there will be a gradual diminution, so that, if we could imagine lines to be drawn along the tops and bottoms of the objects, and to be suffi- ciently prolonged, they would appear to meet in a point, as in Fig. 53. The art which traces ob- jects, with their various degrees of apparent dimi- nution on account of distance, and of foreshortening on account of obliquity of position, is called perspective. 2. The intensity of light, shade, and colour.— It has been shown, that the intensity of light diminishes rapidly, according to the distance of the body, from which it emanates; so that it is only one-fourth as powerful when doubly distant, one-sixteenth when quadruply distant, and so on. This fact is early recognised ; and the mind avails itself of it to judge, with much accuracv, of rela- tive distances. It is, however, a pregnant source of optical illusions. In a bright sunshine, the mountains appear much nearer to ns than when seen through the haze of our Indian summer.* In a row a A delightful season, in the southern and western parts of North America more especially, generally occurring in October or November; and having nothing similar to it, so far as we are aware, in any other part of the globe. It is dependent upon some 250 SENSE OF SIGHT. of lamps along a street, if one be more luminous than the rest, it will seem to be the nearest; and, in the night, we incur the strangest errors, in judging of the distance of any luminous body. The sky appears nearer to the earth directly above, than it does towards the horizon ; because the light from above having to pass only through the atmosphere, is but slightly obstructed, whilst a portion only of that, which has to pass through the dense hetero- geneous air, near the surface of the earth, arrives at the eye. The upper part of the sky being, therefore, more luminous, seems nearer; and, in the same manner, we explain, in part, why the sun and moon appear larger at rising and setting. The shade of bodies keeps pace with their intensity of light; and accordingly, the shadows of objects near us, are strongly de- fined ; — whilst in the distance they become confused, and the light altogether so faint, that the eye at last sees an extent of distant blue mountain or plain; " appearing bluish," says Dr. Arnott,3 " because the transparent air, through which the light must pass, has a blue tinge, and because the quantity of light arriving through the great extent of air is insufficient to exhibit the detail." " The ridge called Blue Mountains," he adds, " in Australia, and another of the same name in America, and many others elsewhere, are not really blue, for they possess all the diversity of scenery, which the finest climates can give; but to the discoverer's eye, bent on them from a distance, they all at first appeared blue, and they have ever since retained the name." As regards the Blue Ridge of America, Dr. Arnott probably labours under misapprehension. Within a very few miles from the whole of this extensive chain, as well as from a distance, the blue tinge is perceptible, especially when the air is dense 'and clear, soon after the sun has descended behind it; so that the name is as appropriate in the vicinity as it was when " the discoverer's eye was bent on it from a distance." It is obvious, that without the alternation of light and shade we should be unable to judge,by the eye, of the shape of bodies; to dis- tinguish a flat circle from a globe ; or any of the prominences and depressions, that are everywhere observable. The universe would appear a flat surface, the outlines of which would not even be per- ceptible ; and the only means of discriminating objects would be by their difference of colour. It is partly by attending to the vary- ing intensity of light and shade, that the painter succeeds in repre- senting the near as well as the distant objects in an extensive land- scape : those in the foreground are made bold and distinct; whilst the remote prospect is made to become gradually less and less dis- tinct, until it fades away in the distance. This part of his art is called aerial perspective. meteorological condition of the atmosphere, and occurs only when the wind is south- erly, or from the warmer regions; disappearing immediately as soon as it veers to the north. By some, this phenomenon has been supposed to be caused by the large fires in the western prairies : but the warmth that attends the haze cannot be explained on this hypothesis, independently of other sufficient objections to it. » Op. cit. APPRECIATION OF DISTANCES. 251 3. Convergence of the axes. — When objects are situate at a moderate distance from us, we so direct the eyes, that if the axes were prolonged they would meet at the object. This angle will, of course, vary inversely as the distance ; so that if the axes be turned to a nearer object, the angle will be greater; if to one more distant, less. By this change in the direction of the axes the mind is capable of judging, to a certain extent, of near distances. A definite muscular effort is required for each particular case ; and the difference in the volition necessary to effect it enables the brain to discriminate, precisely in the same manner as it judges of the height of a body, by the muscular action required to carry the axis from one extremity of the object to the other.a We have the most satisfactory evidence, that such convergence of the axes is indispensable for judging accurately of distance, in near vision. If we fix a ring to a thread suspended from a beam, or attach it to a stand, and endeavour, with-one eye closed, to pass a hook, fixed to the extremity of a rod four or five feet long, into the ring, we shall find it impracticable unless by accident or by touching the ring with the rod. The hook will generally be passed on the far or near side of the ring ; but if we use both eyes, we can readily succeed. They, however, whose eyes are of unequal power, can- not succeed with both eyes. This is strikingly corroborated by the difficulty experienced by those who have lost an eye. Magendieb says it sometimes takes a year, before they can form an accurate judgment ofthe distance of objects placed near the eye. We know, however, one or two interesting examples, in which the power was never regained; notwithstanding every endeavour to train the remaining organ. It need scarcely be said, that the convergence of the axes is no guide to us in estimating objects, which are at such a distance, that the axes are nearly parallel,— as the sun and moon, or any of the celestial luminaries. 4. The interposition of known objects. — Another mode of estimating the magnitude or distance of objects is, by a previous knowledge of the magnitude or distance of interposed or neigh- bouring objects ; and if no such objects intervene, the judgment we form is extremely inaccurate. This is the reason, why we are so deceived in the extent of an unvaried plain or in the distance at which a ship on the ocean may be from us : it is also another cause, why the sky appears to us to be nearer at the zenith than it is at the horizon. The artist avails himself of this means of j udging of magnitude in his representations of colossal species o f the animal or vegetable kingdom, or of the works of human labour and ingenuity ; by placing a well known object along side of them as a standard of comparison. Thus, the representation of an elephant or a giraffe might convey but imperfect notions to the mind, with- out that of his keeper being added as a corrective. It is in consequence ofthe interposition of numerous objects, that * Sir C. Bell, in Philos. Transact, for 1833. t Precis, &c. i. 88. 252 SENSE OF SIGHT. we are able to judge more accurately of the size and distance of those that are on the same level with us, than when they are either much above or much below us. The size and distance of a man on horseback are easily recognised by the methods already men- tioned, when he is riding before us on a dreary plain; the man and horse appearing more diminutive, but, being seen in their usual position, they serve as mutual sources of comparison. When, however, the same individual is viewed from an elevated height, his apparent magnitude, like that of the objects around him, is strikingly less than the reality.a The apparent diminution in the size of objects seen from a height is not to be wholly explained by the foreshortening, which deprives us of our usual methods of judging. It is partly owing to the absence of intervening bodies; and still more perhaps to our not being accustomed to view objects so circumstanced. Simi- lar remarks apply to our estimates of the size and distance of objects placed considerably above us. A cross, at the summit of a lofty steeple, will not appear more than one-fourth of its real size, making allowance for the probable distance ; yet a singular ano- maly occurs here : — the steeple itself seems taller than it really is, and every one supposes that it would extend much farther along the ground, if prostrated,, than it would in reality. The truth, however, is, that if the steeple were laid along the ground, unsur- rounded by objects to enable us to form an accurate judgment, it would appear to be much shorter than when erect, on the princi- ples of foreshortening, already explained. The cause of this small apparent magnitude of the cross and upper part of the steeple is, that they are viewed without any surrounding objects to compare with them : they, therefore, seem to be smaller than they are; and, being smaller, the mind irresistibly refers them to a greater dis- tance. For these reasons, then, it becomes necessary,that figures, placed on lofty columns, should be of colossal magnitude. It is owing partly to the intervention of bodies, that the sun and moon appear to us of greater dimensions, when rising or setting, although the visual angle, subtended by them, may be the same. " The sun and moon," says Dr. Arnott,b " in appearance from this earth are nearly ofthe same size, viz.: — each occupying in the field of view about the half of a degree, or as much as is occupied by a circle of a foot in diameter, when held one hundred and twenty- a Beautifully and accurately is this effect depicted by the great dramatist: — " How fearful And dizzy 'tis to cast one's eyes so low ! The crows and choughs, that wing the midway air, Show scarce so gross as beetles. Half way down Hangs one that gathers samphire; dreadful trade ! Methinks he seems no bigger than his head. The fishermen, that walk upon the beach, Appear like mice; and yon tall anchoring bark, Diminish'd to her cock; her cock a buoy Almost too small for sight." King Lear. b Op. cit. APPRECIATION OF MOTION, ETC., OF BODIES. 253 five feet from the eye — which circle, therefore, at that distance, and at any time, would just hide either of them. Now, when a man sees the rising moon apparently filling up the end of a street, which he knows to be one hundred feet wide, he very naturally believes, that the moon then subtends a greater angle than usual, until the reflection occurs to him, that he is using, as a measure, a street known, indeed, to be one hundred feet wide, but of which the part concerned, owing to its distance, occupies in his eye a very small space. The width of the street near him may occupy sixty degrees in his field of view, and he might see from between the houses many broad constellations instead of the moon only; but the width of the street afar off may not occupy, in the same field of view, the twentieth part of a degree, and the moon, which always occupies half a degree, will there appear comparatively large. The kind of illusion, now spoken of, is yet more remarkable, when the moon is seen rising near still larger known objects — for in- stance, beyond a town or a hill which then appears within a lumi- nous circle." Such are the chief methods by which we form our judgment of the distance and magnitude of bodies ; — 1st, by the visual angle — 2dly, by the intensity of light, shade, and colour — 3dly, by the convergence ofthe axes ofthe eyes — and 4thly, by the interposi- tion of known objects. The eye also enables us to appreciate the motion of bodies. This it does by the movement of their images upon the retina; by the variation in the size of the image ; and by the altered direction of the Ught in reaching the eye. If a body be projected with great force and rapidity, we are incapable of perceiving it; — as in the case of a shot fired from a gun, especially when near us. But if it be projected from a distance, as the field of view is very exten- sive, it is more easy to perceive it. The bombs, sent from an enemy's encampment, can be seen far in the air, in the darkness of night, for some time before they fall; and afford objects for in- teresting speculation regarding their probable destination. To form an accurate estimation of the motion of a body, we must be ourselves still. When sailing on a river, the objects, that are stationary on the banks, appear to be moving, whilst the boat, which is in motion, seems to be at rest. Bodies, that are moving in a straight line to or from us, scarcely appear to be in motion. In such cases, the only mode we have of detecting their motion is by the gradual increase in their size and illumination, when they approach us; and the converse, when they are receding from us. If at a distance, and the visual angle between the extreme points of observation be very small, the motion of an object will likewise appear extremely slow ; hence the difference between a carriage dashing past us in the street, and the same object viewed from a lofty column. A balloon may be moving along at the rate of nearly one hundred miles per hour; yet, except for its gradual diminution in size and in intensity of light, it may appear to be at rest; and, vol. i. — 22 254 SENSE OF SIGHT. when bodies are extremely remote from us, however astonishing may be their velocity, it can scarcely be detected. Thus, the moon revolves round the earth at the rate of between thirty and forty miles a minute — above forty times swifter than the fleetest horse; yet her motion, during any one moment, completely escapes detec- tion ; and the remark applies still more forcibly to those lumina- ries, which are at a yet greater distance from the earth. These are cases in which the body moves with excessive velocity, yet the image on the eye is almost stationary; but there are others,in which the real motion is extremely slow, and cannot be at all observed, as that of the hour-hand of a clock or watch. It will be obvious, from all the remarks that have been made, regarding the information derived by the mind from the sense of sight, that a strictly intellectual process has to be executed, without which no judgment can be formed; and that nothing can be more erroneous than the notion, — at one time prevalent,— that the method by which we judge of distance, figure, &c, is in- stinctive or dependent upon an original " law of the constitution," and totally independent of any knowledge gained through the medium of the external senses. It has already been remarked, that metaphysicians may be considered as divided into those, who believe that, without the sense of touch, the eye would be incapa- ble of forming any accurate judgment on these points; and those who think, that the sense of touch is no farther necessary than as an auxiliary, and that a correct appreciation can be formed by sight alone. Molyneux,3 Berkeley,b Condillac,0 &c, support the former view; Gall,d Adelon,e &c, the latter. Ofthe pre- cise condition of the visual perception during early infancy, we are of course entirely ignorant. So far as our own recol- lections would carry us back, we have always been able to form a correct judgment of magnitude, distance, and figure. Observa- tion, however, of the habitudes of infants would seem to show, that their appreciation of these points — especially of distance — is singularly imprecise ; but whether this be owing to the sense not yet having received a sufficient degree of assistance from touch, or from want of the necessary development in the structure or func- tions of the eyeball or its accessory parts, we are precluded from judging. The only succedaneum is the information to be obtained, regarding their visual sensations, from those who have been blind from birth, and have, been restored to sight by a surgical operation. Although in the numerous operations of this kind, which have been performed, it might seem, that cases must have frequently occurred for examining into this question, such is not the fact; and meta- physicians and physiologists have generally founded their obser- vations on the celebrated case described by Cheselden.f The sub- 1 Locke's Essay on the Human Understanding, book ii. chap. 9. b Essay on Vision, 2d edit., Dublin, 1709. <= Traite des Sensations, Part. i. 1 Sur les Fonctions du Cerveau, i. 80, Paris, 1825. « e Physiologie de l'Homme, edit. cit. i. 466. f The Anatomy ofthe Human Body, 13th edit., Lond. 1792. APPRECIATION OF MAGNITUDE, ETC. 255 ject of this was a young gentleman, who was born blind, or lost his sight so early, that he had no remembrance of ever having seen, and was " couched," so says Cheselden, "between thirteen and four- teen years of age." Magendiea affirms, that there is every reason to believe that the operation was not that for cataract, but consisted in the incision of the pupillary membrane. It need hardly be re- marked, that Cheselden must be the best possible authority on this subject. " When he first saw," says Cheselden, " he was so far from making any judgment about distances, that he thought all objects whatever touched his eyes, (as he expressed it,) as what he felt did his skin, and thought no objects so agreeable as those which were smooth and regular, though he could form no judg- ment of their shape, or guess what it was in any object that was pleasing to him. He knew not the shape of any thing, nor any one thing from another, however different in shape or magnitude ; but upon being told what things were, whose form he before knew from feeling, he would carefully observe, that he might know them again; but having too many objects to learn at once, he forgot many of them ; and, (as he said,) at first he learned to know, and again forgot a thousand things in a day. At first he could bear but very little light, and the things he saw he thought extremely large ; but, upon seeing things larger, those first seen he conceived less, never being able to imagine any lines beyond the bounds he saw ; the room he was in, he said, he knew to be but part of the house, yet he could not conceive that the whole house could look bigger." A much more interesting case, in many respects, than this of Cheselden's, which has always appeared to us too poetical, was laid before the Royal Society of London, in 1826, by Dr. Wardrop.b It was that of a lady born blind, who received sight at the age of forty-six, by the formation of an artificial pupil. During the first months of her infancy, this lady was observed to have something peculiar in the appearance of her eyes; and, when about six months old, a Parisian oculist operated on both eyes, with the effect of complete destruction of the one, and not the slightest improve- ment to the other. From this time, she continued totally blind, being merely able to distinguish a very light from a very dark room, but without the power of perceiving even the situation of the window through which the light entered, though, in sunshine, or bright moonlight, she knew its direction ; she was, therefore, in greater darkness than the boy in Cheselden's case, who knew black, white, and scarlet, apart from each other ; and, when in a good light, had that degree of sight, which usually exists in an eye af- fected with cataract; whilst in this lady the pupil was completely shut up, so that no light could reach the retina, except such rays as could pass through the substance of the iris. After a third ope- ration had been performed for the formation of an artificial pupil, she returned from Dr. Wardrop's house in a carriage, with her eyes » Precis, &c. i. 95. h Philosoph. Transact. 1826, p. 529. 256 SENSE OF SIGHT. covered with only a loose piece of silk. The first thing she noticed was a hackney-coach passing by, when she exclaimed, " What is that large thing that has passed by us?" In the course of the evening she requested her brother to show her his watch, and she looked at it a considerable time, holding it close to her eye. " She was asked what she saw, and she said there was a dark and a bright side ; she pointed to the hour of twelve and smiled. Her brother asked her if she saw anything more ; she replied yes, and pointed to the hour of six, and to the hands of the watch. She then looked at the chain and seals, and observed that one of the seals was bright, which was the case, being a solid piece of rock crystal." On the third day she observed the doors on the opposite side of the street, and asked if they were red. They were of an oak colour. In the evening, she looked at her brother's face, and said she saw his nose ; he asked her to touch it, which she did ; he then slipped a handkerchief over his face, and asked her to look again, when she playfully pulled it off, and asked, " What is that ?" On the thirteenth day, she walked out with her brother in the streets of London when she distinctly distinguished the street from the foot pavement, and stepped from one to the other, like a person accus- tomed to the use of her eyes. " Eighteen days after the last ope- ration," says Dr. Wardrop, " I attempted to ascertain, by a few experiments, her precise notions of the colour, size, and forms, position, motions, and distances of external objects. As she could only see with one eye, nothing could be ascertained respecting the question of double vision. She evidently saw the difference of colours; that is, she received and was sensible of different impressions from different colours. When pieces of paper, one and a half inch square, differently coloured, were presented to her, she not only distinguished them at once from one another, but gave a decided preference to some colours, liking yellow most, and then pale pink. It may be here mentioned, that, when desirous of examining an object, she had considerable dif- ficulty in directing her eye to it, and finding out its position, moving her hand as well as her eye in various directions, as a person, when blindfolded or in the dark, gropes with his hand for what he wishes to touch. She also distinguished a large from a small object, when they were both held up before her for com- parison. She said she saw different forms in various objects, which were shown to her. On asking what she meant by different forms, such as long, round, and square, and desiring her to draw with her finger those forms on her other hand, and then presenting to her eye the respective forms, she pointed to them exactly ; she not only distinguished small from large objects, but knew what was meant by above and below; to prove which, a figure drawn with ink was placed before her eye, having one end broad and the other narrow, and she saw the positions as they really were, and not inverted.(! !) She could also perceive motions ; for when a glass of water was placed on the table before her, on approaching APPRECIATION OF MAGNITUDE, ETC. 257 her hand near it, it was moved quickly to a greater distance, upon which she immediately said, ' you move it ; you take it away.' She seemed to have the greatest difficulty in finding out the dis- tance of any object; for, when an object was held close to her eye, she would search for it by stretching her hand far beyond its position, while on other occasions she groped close to her own face for a thing far remote from her." The particulars of this case have been given at some length, inasmuch as they are regarded by Dr. Bostock*— and appa- rently by Dr. Wardrop himself — as strikingly confirmatory of those of Cheselden, than which we cannot imagine any thing more dissimilar. It will have been noticed, that, from the very first after the reception of sight, she formed an imperfect judg- ment of objects, and even of distances, although she was devoid of the elements necessary for arriving at an accurate estimate of the latter — the sight of both eyes. This was, doubtless, the chief cause of that groping for objects, which is described by Dr. Wardrop. Of forms, too, she must have had at least an imperfect notion, for we find, that on the thirteenth day after the operation, she stepped from the elevated foot-pavement to the street, " like a person accustomed to the use of her eyes." The case is, we think, greatly in favour ofthe view, that the sight does not require much education to judge with tolerable accuracy of the position, magnitude, distance, surface, and motion of bodies ; and that, by a combination of the methods we have already pointed out, or of some of them, this imperfect knowledge is obtained, without the aid of any of the other senses ; but is of course ac- quired more easily and accurately with their assistance, especially with that of touch. What other than visual impressions could have communicated to the mind of Miss Biffin — whose case was referred to under another head — the accurate and minute infor- mation which she possessed regarding the bodies surrounding her, at all distances ? Or how does the animal, immediately after birth, acquire its knowledge of distance ? We observe the young of some animals immediately after they are extruded from the uterus, turn round and embrace the maternal teat; whilst others, as the partridge, follow the mother immediately after they have burst the shell. The experience required for obtaining an imper- fect knowledge of distance, shape, &c, must, therefore, be trifling ; although an accurate acquaintance may demand numerous, and careful comparisons. This first degree of knowledge is probably obtained, by comparing the visual angle with the intensity of light, shade, and colour —the more accurate appreciation following the use of the other methods already described. That the conver- gence of the axes requires education is demonstrated in the case of the infant. It has been remarked, that the eyeballs harmonize a Physiology, 3d edit. p. 703, Lond. 1836. See, also, the case of a gentleman born blind, and successfully operated upon in the 18th year of his age, by Dr. J. C. Franz, in Proceedings ofthe Royal Society, 1840-41, No. 46. 258 SENSE OF SIGHT. instinctively in their parallel motions; but the convergence requires an effort of volition, and it is some time before it can be effected, which is probably the great cause ofthe mal-appreciation of near distances, which we notice in the infant; whilst it seems to exhibit its capability of judging more correctly of objects, that are somewhat more remote, and where less convergence, and con- sequently less muscular effort, is necessary. The numerous optical illusions, which we have been compelled to describe, in the progress of the preceding remarks, will render it necessary to refer to but few under this head. It has already been said, that we lay it down as a rule, that the progress of light to the eye is always in a straight line from the luminous object; and, accordingly, if the course of the rays be modified before they reach the organ, we fall into an optical illusion. Such modifica- tions arise either from the reflection or refraction of the rays pro- ceeding from the object that causes the sensation. By reflection of the rays, we experience the illusion caused by mirrors. A ray of light, K C, Fig. 22, falling upon a plane mirror, I J, is reflected back in the same line ; but, as we have seen, the object will not appear to be at K, but at E. Again, a ray of light proceeding obliquely from B, and impinging on a plane mirror at C, will be reflected in the direction of Fig. 54. C A; but to the eye at A, the ..... object B will appear to be at H, in the prolongtion of the ray that reaches the eye. If the mirror be concave, the object will appear magni- D;......""" fied, provided the light from the upper part of the object, as A B, Fig. 46, be reflected to an eye at F, and that from the lower part of the object meet the other at this point. To an eye so placed, the object will appear magnified and seem to be at C D, or in the prolongation of the rays which fall upon the cornea. If the mirror be convex, for like reasons, the cross will seem to be smaller. The cornea constitutes a mirror of this class, in which we have an accurate miniature representation of objects. Rays, that are refracted in passing through different media, also give rise to visual illusions. We have seen, that the ray from an object at F, Fig. 22, in the pool of water, I J, does not proceed into the air in the direction of F C 0, but in that ofthe line F C A ; and if we suppose the eye to be placed at A, the object will not be seen at F, but will appear to be at /; the pool will, consequently, appear shallower than it really is, by the space at which / is situate above the bottom. We can now understand why rivers appear shallower than they really Fig. 55. OPTICAL ILLUSIONS. 259 are, when viewed obliquely ; and why the lower end of a pole immersed in water, should, when seen obliquely, appear to be bent towards the surface. In shooting fish in the water, or in attempting to harpoon them, this source of error has to be corrected. Those birds, too, that live upon the inhabitants of the water, will have to learn, from experience, to obviate the optical illusion ; or to descend perpendicularly upon their prey, in which direction, as we have seen, no refraction takes place. Similar remarks apply to the fish that leap out ofthe streams to catch objects in the air. The Chastodon rostra- tus, about six or eight inches long, frequents the sea-shores in the East Indies : when it observes a fly, sitting on the plants that grow in shallow water, it swims to the distance of five or six feet, and then, with surprising dexterity, ejects out of its tubular mouth a single drop of water, which never fails to strike the fly into the sea where it soon becomes its prey.3 Hommel —a Dutch governor — put some of these fish into a tub of water, and then pinned a fly on a stick within their reach. He daily saw the fish shoot at the fly, and with such dexterity, that they never failed to hit their mark.b Pallas describes the Siaena jaculatrix as securing flies by a similar contrivance. If the light, before reaching the eye, passes through bodies of a lenticular shape, it undergoes modifications, which have given occasion to the formation of the useful instruments, that have been devised for modifying the sphere of vision. If the lens be double convex, the body, seen through it, appears larger than it is, from the illusion, so often referred to, that we always refer the object in the direction of the line, that impinges upon the retina. The object, consequently, appears to be greatly augmented. (See Fig. 28.) For the same reasons an object seems smaller to the eye at A, Fig. 25, when viewed through a double concave lens. Again, if the light, before reaching the cornea, be made to pass through a diaphanous body, which is itself coloured, and consequently allows only the rays of its own colour to traverse it, the object is not seen of its proper colour, but of that ofthe transparent body. An impression of light continues to affect the retina for the sixth part (M. D'Arcy says the seventh part) of a second. If, therefore, a live coal be whirled round a circle, six or seven times in a second, it will seem to be a continuous circle of fire. It is owing to this circumstance, that meteors seem to form a line of light,—as in the case of the falling star, — and that the same impression is conveyed by a sky-rocket in its course through the air. We have an eluci- dation of this fact in the instrument or toy — called, by Dr. Paris, the thaumatrope — which consists of a circle, cut out of a card, and having two silken strings attached to opposite points of its diameter: by twisting these with the finger and thumb the card may be twirled round with considerable velocity. On one side of a Fleming's Philos. of Zoology, i. 195. t> Philos. Trans, liv. 89. c Ibid. lvi. 186; also, Mr. Sharon Turner's Sacred History of the World, Amer. Edit. i. 205, New York, 1832. 260 ADDITIONAL SENSES. the card an object is drawn — as a chariot —and on the other, the charioteer. If the card be twirled round six or seven times in a second, the charioteer will be seen in the chariot, — the duration of the impressions on the retina being such as to cause the figures, drawn on both sides of the card, to be seen at the same time. The phantasmascope and anorthoscope act upon similar principles. It is by accurate attention to various optical illusions, and to the laws of the animal economy on which they are founded, that many of them can be produced in the arts at pleasure. Painting is, in truth, little more than depicting on canvass the various optical errors, which we are habitually incurring. To conclude, — the sense of sight differs materially in the scale of animals : in few is the organization more perfect or the function better executed than in man. Situate at the upper and anterior part of the body, it is capable of directing its regards over a large extent of surface; of converging the axes of the two organs upon objects in various situations, which cannot be effected by many animals; and it is very moveable, and under the domination of a muscular apparatus of admirable arrangement. Still, it is not as delicately organized as in some animals, which are capable of see- ing objects at a distance, that would be totally beyond the reach of the visual powers of man. Like the other senses, sight can be exerted actively and pas- sively ; hence the difference between simply seeing and looking. In the latter, the eye is directed to the object by the proper mus- cles ; and it is not improbable but that the nerve may be aroused to a more accurate and delicate reception of impressions, as we have some reason for believing it to be in the case of the other senses. Like them, it admits of great improvement by education. The painter, and the worker in colours are capable of nice dis- crimination, and detect the minutest shades of difference with the greatest facility. In savagelife, where the tracks or marks through the almost interminable forests, or over the pathless wilds, are the only guides, the greatest acuteness of vision is necessary; and, accordingly, we find the North American Indian, in this respect, eminently distinguished. The mariner, too, accustomed to look out for land, or for a hostile sail, will detect it in the distant hori- zon long before it can be perceived by the landsman, and will appreciate its distance and course with signal accuracy,— educa- tion, in this case, not only communicating to his eye facility in being impressed, but improving the intellectual process, by which he arrives at the estimation of distances. ADDITIONAL SENSES. The five senses, which have been considered, constitute as many special nervous systems, each concerned in its appropriate function; and,although conveying ideas of the external world to the brain, and connected with that organ, they are to a certain extent independent of ADDITIONAL SENSES. 261 it. The generality of physiologists admit only these five; but some have suggested others, differing, in general, however, from the five, in having no organ at the surface of the body exclusively con- cerned in the function. Buffon regarded as a sixth sense, the intense sensation experienced during the venereal act; but this can only be esteemed a peculiar variety of tact in the mucous mem- brane of the genital organs; — differing from ordinary tact in those parts, by requiring in both sexes a special condition of the mem- brane ; and, in the male, one such, that the sperm, when excreted, shall make the necessary impression upon it; and, consequently, appertaining to both the external and internal sensations;—the state ofthe membrane being referrible to the latter, and the effect ofthe contact of the sperm to the former. Some have spoken of a sense of heat and cold: — this we have described under the head of tact; — others of a muscular sense, by which we acquire a knowledge of the motions to which muscular contractions give rise, and thus learn to apportion the effort to the degree of effect to be pro- duced. Animal magnetizers,again, have suggested a sixth sense, to which man owes the capability of being acted upon by them: but this is entirely supposititious, and the facts admit of a more ready and satisfactory explanation. A sense of hunger has been de- scribed as situate at the upper orifice of the stomach : — a sense of thirst in the oesophagus, and a pneumatic sense in the lungs; bu t all these are more properly internal sensations. The German physiologists have suggested another sense, which they term coenassthesis.a This is not seated in any particular part ofthe body, but over the whole system, and hence termed " com- mon." It is indicated by the lightness and buoyancy, which we occasionally experience, apparently without any adequate cause, as well as by a sense of lassitude and fatigue, unconnected with, muscular action or disease. To it, likewise, belongs the invo- luntary shuddering, glow, or dullness, experienced under similar circumstances. It is manifestly one of the numerous internal sen- sations felt by the frame, and every portion of it, according as they are in a perfect state of health, or labouring under some cause of irritation or oppression; but can scarcely be regarded as an addi- tional or sixth sense.b It has been supposed, that certain animals may possess other senses than the five mentioned. Of this we can have no positive evidence. We are devoid of all means of judging of their sensa- tions ; and if we meet with an additional organ, which seems adapted for such a purpose, we have nothing but conjecture to guide us. Under the sense of touch it was said, that the bat a Gemeingefuhl, Gemeinsinn, KorpergefUhl, Lebenssinn, Individual itatssinn, and S e I b s t g e f u h 1 (" common feeling, common sensation ; bodily feeling, feeling of life, sense of life, sense of individuality, and self- feeling"). b Purkinje, art. Coensesthesis, in Encycl. Worterb. der Medicinisch. Wissenschaft. viij. 116, Berlin, 1832; and MUller's Elements of Physiology, by Baly, P. v p 1087* Lond. 1839. ' 262 ADDITIONAL SENSES. is found to be capable of avoiding obstacles, placed in its way intentionally, when the eyes, nostrils, and ears have been closed up; and it readily returns to the holes in the caverns to which it is ha- bituated. Spallanzani supposed that this was owing to its being possessed of a sixth sense. We have seen, that the circumstance is explicable by unusual delicacy of one of the external senses. Again; the accuracy with which migratory animals return to their accustomed haunts has given rise to the notion of a sense of locality, which is presumed to preside over this faculty. This is, doubtless, however, a cerebral faculty. Quadrupeds, the ape not excepted, have two bones in the face, in addition to those found in man. These contain the roots of the dentes incisores, when such are present; but they exist in animals also that are destitute of teeth. They are termed ossa intermaxil- laria, ossa incisoria, and ossa labialia, and are situate, as their names import, at the anterior part of the jaw, and between the ossa maxillaria or jaw bones. Jacobson3 considers them to be an organ of sense, as they communicate with the exterior, and are largely supplied with vessels and nerves. Accordingly, this has been esteemed a sensitive apparatus, connected with the season of love in animals ; and, by other naturalists, as a sense intermediate between those of taste and smell, and intended to guide the animal in the proper selection of food. It need hardly be said, that this is all imaginary. Adelon,b it was remarked, makes two divisions of the external sensations: — those that convey information to the mind; and those that do not. The former have engaged attention; the latter will net occupy us long. They comprise but two —itching and tickling. Both of these occur in the skin and mucous membranes, ^tnd near the communication of the latter with the skin ; or, in other words, near the termination of the outlets which they line. Itching, however, is not always an external sensation, — that is, not always caused by the contact of a body external to it. It fre- quently arises from an altered condition of the organic actions of the part in which it is experienced, as in cutaneous affections; in itching at the nose produced by irritation in the intestinal canal; itching at the glans penis in cases of calculi of the urinary bladder, &c, but commonly the sensation is caused by an extraneous body; and we are irresistibly led to scratch, no matter how it may be produced. When it arises extraneously, it can generally be readily allayed; but, when dependent upon a morbid condition of the texture of the part, it becomes a true disease, and the source of much suffering. If the itching be accompanied with a feeling of motion, or of purring in the part, it is called tingling. This kind of purring often occurs without itching. Tickling or titillation is always caused by the contact of some extraneous substance, and is therefore a true external sensation. » Annales du Musee, xviii. 412. b Physiologie de l'Homme, 2de e"dit. i. 481, Paris, 1829. INTERNAL SENSATIONS. 263 Although occurring in the skin, and in the commencement or ter- mination of the mucous membranes, all parts are not equally sus- ceptible of it; and some, — as the lining membrane of the genital organs, — are only, or chiefly so, under particular circumstances. The sides, palms of the hands, and soles of the feet, are the most sensitive in this respect; not, perhaps, because the nerves are more numerous in those parts, but because, owing to thinness or suppleness of skin, or to other inappreciable circumstances, they are more susceptible of this kind of excitation. We find, too, that individuals differ as much as the parts of the body do in this respect, some being not ticklish, or incapable of being thrown into the spasm, which the act, nay, even the threatening of the act, produces in others. Cases are on record, in which prolonged titillation has produced general convulsions, and even death. Le Cat3 terms it an hermaphroditic sensation, inasmuch as, on the one hand, it excites laughter; and, on the other, is insupportable; and, consequently, appears to be intermediate between pleasure and pain. b. Internal Sensations. The external sensations make us acquainted with the universe surrounding us; and convey to the mind a knowledge of every thing that can be, in any manner, inservient to our necessities. Such necessities have, however, to be suggested to the mind, before it reacts through the aid of the organs of prehension or otherwise on external bodies, and this is accomplished by the agency of the internal or organic sensations. Without the intervention of any external cause, every organ of the body is capable of transmitting to the brain a number of differ- ent impressions, many of which impel the organ to acts that are necessary not only for the preservation of the individual and of the species, but also for the perfect development of the faculties. Such are the sensations of hunger and thirst; the impulse that leads to the union of the sexes : and the feeling we have of the necessity for intermission in the exercise of the muscles and of the intellect. They have been divided into three species by some physiologists : the first arousing, or giving impulse to, the action of organs; and warning the brain of the different necessities of the system. They have been called wants or instinctive desires.h Such are hunger, thirst, the desire to evacuate the urine and fasces; that of respira- tion, the venereal appetite, accouchement, &c. They belong to those that arise, when it is necessary the organs should act. The second species occur during the action of organs. They are often obscure, but sometimes very acute. Amongst these are the im- pressions accompanying the different excretions,—as that of the • sperm, urine, &c, (although, as we have seen, these partly belong to the external sensations); the impressions that warn us of our * Traite" des Sens, Paris, 1767. b Adelon,art. Besoins, in Dict.de Medecine, i. 367, Paris, 1821 ; and Physiologie de l'Homme, i. 482. 264 INTERNAL SENSATIONS. partial or general movements, of the progress of digestion, and of the intellectual labours. The last species succeed to the action of organs, especially when such action has been too long continued ; hence the inward feeling of fatigue, after too long exertion of the functions of the senses, of the intellectual and moral faculties, and of the organs of muscular motion; the necessity of repose after prolonged muscular exertion ; and of sleep, to recruit the nervous system, and to fit it for the exertions it has to make during the waking condition. The mode in which these sensations are effected is analogous to that of the external sensations. There is an impression on the part to which the sensation is referred; an action of perception, accomplished by the brain, and one of transmission, executed by a nerve passing between the two parts. The two last actions are probably executed in the same manner as they are in the external sensations. The first, or the mode in which the impression is effected, and the character of the impression itself, are much more obscure. In the external sensations, we can refer the impression to a known irritant, — special in some of the senses: — more general in others. We know, that light impresses the retina: — aerial undulations the acoustic nerve, &c. ; but, in the internal sensations or sentiments, as some of the French writers term them, the source of the irritation is in some modified action of the part itself, in the very tissue of the organ, and hence the result is said to be organic. In the internal sensation of hunger, for example, the impression is engendered in the organ, — how, we know not, — is thence conveyed to the brain ; and the sensation is not effected until the latter has acted. The same may be said of all the other internal sensations. They differ, in other respects, also, from the external sensations. Whilst the latter may be entirely passive, or be rendered active by volition, without either action being the cause of particular pleasure or inconvenience, the former are but little influenced by volition. Constituting the wants — the instinctive desires — which impel to acts, that are necessary for the preserva- tion and full development of the individual and of the species, such independence is of course essential. On many of them, how- ever, habit or accustomed volition has a certain degree of influence : and they can unquestionably be augmented or moderated by licen- tious indulgence or restraint. The influence of habit is exemplified by the regularity with which the appetite returns at stated inter- vals ; and by the difference between that of the gourmand and of the temperate individual. It is most strikingly evidenced, how- ever, in its influence over the moral wants ; which may even spring up from social indulgence, and hence are not instinctive or organic: we are every day, indeed, compelled to notice the striking differ- ence between the individual, who practises restraint upon his wants, and the libertine, who, like the animals surrounding him, gives unbridled sway to his natural and acquired appetites. All the internal sensations, when satisfied or responded to in MORBID SENSATIONS. 265 moderation, communicate a feeling of pleasure; but if resisted, pain results. If hunger be prolonged, there is a general feeling of uneasiness, which rapidly abates after food is received into the sto- mach in due proportion; but if satiety be produced, uneasiness follows ; and this applies to all the appetites or wants. The par- ticular internal sensations will engage us, when the functions to which they belong fall under consideration. Like the external sensations they must, of course, administer to the intellect; to an extent which will be seen hereafter. Their influence and nature were entirely neglected, until of comparatively late years. At- tention has been directed to them chiefly through the labours of Cabanis3 and of Destutt-Tracy,b and they now form subjects for interesting speculation with the metaphysician. . The morbid sensations belong more particularly to pathology : a brief notice of them will consequently be all that is necessary here. They are comprised under the term pain. In its enlarged signifi- cation, this word, as is well known, means every uneasy or dis- agreeable sensation or moral affection ; — thus including sadness, anger, terror, as well as the painful impressions feTt in the extre- mities or trunks of the nerves. It is the latter only — or physical pain — that concerns us at present. Like every other sensation, although it may be referred exclusively to the part impressed, pain requires the intervention ofthe brain: for if the nerves, proceeding from a part to that organ, be cut, tied, compressed, or stupified by narcotics; or if the action of the brain itself be blunted from any cause, as by the use of opium, or by any compression, accidental or other, the sensation is no longer experienced. We can thus understand why pain is less felt during sleep ; and the astonishing cases of resistance to pain, which we witness in the lunatic, and in religious or other enthusiasts, who have been subjected to bodily torture. An opposite condition of the nervous system is the cause of the great sensibility to impressions, which we witness in the nervous and hysterical. It is obvious, that pain may be either an external or internal sen- sation, according as the cause of irritation is extraneous, or seated in the tissue of organs; and that it must vary considerably, both as regards the precise irritant, and the part affected ; hence the dif- ference between the pain caused by a burn, and that by a cutting instrument; and the immense variety of pains to which the human frame is subject, and the attentive study of which is so indispensa- ble to the pathologist. So much for the sensations. These, we have seen, are innume- rable, for each sense is capable of myriads of different impressions. We now pass to the consideration of those functions which enable man—although worse provided with means of defence and offence than the beasts surrounding him, and possessing no covering, to protect him from the summer's heat or the winter'scold * Rapport du Physique et du Morale de 1'Homme, torn, ii., Paris, 1802. b Elemens d'Ideologie, 2de edit., Paris, 1804. vol. I. — 23 266 MENTAL FACULTIES. __to provide himself means of defence; to render the animals around him subservient to his use; to cover his nakedness and protect himself against atmospheric changes; to devise every mechanical art; to fathom the laws, that govern the -bodies by which he is surrounded, and to establish himself undisputed master ofthe earth. OF THE MENTAL FACULTIES. The external senses convey to the brain the different impressions made upon them by surrounding bodies ; but, of themselves, they would be unable to instruct the mind regarding the universe. It is necessary, that the brain should act before any perception, any idea of them can exist. The mental faculties, in other words, convert the impressions into such ideas. The internal sensations, on the other hand, consist, as we have seen, of the numerous wants and appetites necessary for the preservation of the individual and of the species. In addition to these, man possesses another series of faculties, which influence his character and disposition, and direct his social existence : these are the affective ox emotive facul- ties, or the faculties of the heart. The study of these different mental and moral phenomena embraces what has been called psychology, from a notion that they are exclusively dependent upon the mind. The notion was, at one time, universal, and hence the appellation metaphysician, applied to such as were considered to proceed in their investigations of those subjects beyond what was physical, material, or corporeal. There is no subject, which has given occasion to so much excite- ment and controversy, as that of the connexion of the mental facul- ties with the encephalon. " It has unfortunately happened," says Dr. Bostock,3 " that this subject, which is one of great interest and curiosity, has seldom been viewed with that philosophical spirit which should always direct our investigations, and by which alone we can expect to arrive at truth. It is admitted, that certain errors may be so interwoven with our accustomed associations, on topics connected with morals and religion, as to render it doubtful, on some occasions, how far we ought to attempt their removal: but if this concession be made on the one hand, it is incumbent upon us, on the other, not to inflame the prejudices, which may exist on these topics, but to use our endeavours to correct all undue excite- ment, and thus to bring the mind into that tranquil state, which may enable it to receive truth without fear of injury." In such a spirit ought every discussion on this interesting subject to be con- ducted ; and in such a spirit will the few remarks, which follow, be offered. The chief opinions, which have been indulged on this subject. are,— 1st. That all the mental phenomena are immaterial and the exclusive product of the mind. 2dly. That the sentient principle, within us, requires the intervention of an organ, through which it acts; in other words, that mind is a principle superadded to or- ganization ; and 3dly. That where there is no organization there is a Physiology, 3d edit. p. 744, Lond. 1836. MENTAL FACULTIES. 267 no perception:—that wherever an organized structure, like the brain, exists, perception exists ; that where the organization is imperfect, perception is imperfect; where the organization is sound and vigorous, perception is clear and vigorous ; where it is impaired, perception is impaired; and that, when the organization ceases, perception ceases also. This last view is materialism. It sup- poses that a certain condition of matter is capable of thinking, reasoning, and understanding. The doctrine,—that our intellectual and moral acts are super- added to organization, during life, and that there is an organ ofthe body concerned in their manifestation, — is the one em- braced by the generality of physiologists, and is most consistent with reason and analogy ; it is but justice, however, to admit that the views of those, who consider that a certain organization produces thought, are not deserving of the anathemas which have been directed against them on the score of irreligion. The charge would rather apply to those who could doubt the power of Omnipotence to endow matter with such attributes. Were the mental and moral phenomena the exclusive products of the imma- terial principle within us, they would hardly form subjects for physiological inquiry. That they are allied to organization is in- ferred for the following reasons. As they constitute so many func- tions, were they not provided with an organ or organs, they would form so many exceptions ; — each of the sensations requiring an organ for its accomplishment. Again, our inward feeling induces us to refer them to a particular part ofthe frame: whilst thought ap- pears to us to be effected within the head, the chief effects of the passions are felt in the region of the heart or stomach. The facul- ties, moreover, are not the same in every individual. One man is a poet, another a mathematician; or one is benevolent, another cruel. If these faculties were the exclusive product of the mind, and of course not to be ascribed to diversity of organization, we should have to admit, that each individual has a different imma- terial principle, and of course, that there must be as many kinds as there are individuals. Lastly. The faculties vary in the same individual according to circumstances. They are not the same in the child as in the adult; in the adult as in one advanced in life ; in health as in disease ; in waking as in sleep. During an attack of fever they become temporarily deranged, and are permanently so in all the varieties of insanity.3 These facts are inexplicable under the doctrine, that they are the exclusive product of the mind or immaterial principle. An immaterial or spiritual principle ought to be immutable; yet we should have to suppose it capable of alteration ; of growing with the growth of the body, and of be- coming old with it; of being awake or asleep ; sound or diseased. All these modifications, we must presume, are impressed by vary- ing organization — of the brain in particular. We may conclude, then, that the intellectual and moral faculties are not the exclusive * Adelon, art. Encephale, Diet, de Medecine, vol. vii.; and Physiologie de l'Homme, torn. i. edit. cit. 268 MENTAL FACULTIES. product ofthe mind, but that they require the intervention of an organ; and that this organ is the encephalon, or a part of it — the brain — is announced by many circumstances. In the first place, they are phenomena of sensibility, and hence we should be disposed to refer them to a nervous organ; and being the most elevated phenomena of the kind, to the highest of the nervous organs. In the second place, inward feeling induces us to refer them thither. We not only feel the process there, during meditation, but the sense of fatigue, which succeeds to hard study, is experienced there likewise. The brain, again, must be in a state of integrity, otherwise the faculties are deranged ; or, for the time, abolished. In fever, the brain becomes affected di- rectly or indirectly, and the consequence is — perversion ofthe intellect, in the form of delirium. If the organ be more perma- nently disordered, as by the pressure of an exostosis or of a tumour, or by some alteration in its structure or functions — less apprecia- ble in its nature—insanity, in some of its forms, may be the result. In serious accidents to the encephalon, we observe the import- ance of the cerebral organ to the proper exercise of the mental faculties most clearly evinced. A man falls from a height and fractures his skull. The consequence of this is depression of a portion of bone, which exerts a degree of compression upon the brain; or extravasation of blood from some of the encephalic vessels, attended with similar results. From the moment of the infliction of the injury, the whole of the mental and moral mani- festations are suspended, and do not return until the compressing cause is removed by the operation of the trephine. Richerand cites the case of a female, who had a portion of the brain acci- dentally exposed, and in whom it was found, that pressure upon the brain completely deprived her of all consciousness, which was not restored until the pressure was removed. A similar case occurred to Professor Wistar; and another is related by Lepel- letier.3 A patient of a Dr. Pierquien had an extensive caries of the os frontis, with a perforation of the bone, which exposed the brain covered by its membranes. When she slept soundly, the organ sank down; when she dreamed, or spoke with feeling, turgescence and marked oscillations were perceptible ; when the brain was pressed upon, she stopped in the middle of a sentence or of a word, and when the pressure was removed, she resumed the conversation, without any recollection of the experiment to which she had been subjected. We notice, however, an important dif- ference in the effect, according to the suddenness or tardiness with which the pressure is produced. Whilst a sudden compression suspends the intellectual and moral manifestations for a time ; slow pressure, produced by the gradual formation of a tumour, may exist without exhibiting, in any manner, the evidences of its pre- sence. Accordingly, the anatomist is sometimes surprised to dis- cover such morbid formations in the brains of those who have never laboured under any mental aberration. 1 Physiologie Medicale, &c. iii. 242, Paris, 1832. MENTAL FACULTIES. 269 A negative argument in favour of this function of the brain has been deduced from the fact, that disease of other portions of the body, even of the principal portions, may exist and pass on to a fatal termination, leaving these faculties almost wholly unimpaired. Such is proverbially the case with phthisis pulmonalis, the subject of which may be flattering himself with hopes never to be realized, and devising schemes of future aggrandizement and pleasure, until within a few hours of his dissolution. The intellectual faculties differ in each individual, and vary materially with the sex. The brain is, in all these cases, equally different. Much may depend upon education; but it may, we think, be laid down as an incontrovertible position, that there is an original difference in the cerebral organization of the man of genius and of him who is less gifted ; and that, as a general prin- ciple, in the former the brain is much more developed than in the latter. Whilst the brain ofthe man of intellect may measure from nineteen to twenty-two inches in circumference, that of the idiot frequently does not exceed thirteen, or is not greater than in the child one year old. It was an ancient observation, that a large development of the anterior and superior parts of the head is a characteristic of genius; and, accordingly, we find, that all the statues of the sages and heroes of antiquity are represented with high and prominent foreheads. In the older poets, we meet with many evidences, that the height of the forehead was regarded as an index of the intellectual or moral character of the individual.3 The relation between the size of the head and the mental mani- festations has, indeed, interwoven itself into our ordinary modes of speech. Perhaps, as a general observation, it may be found true, that the mental capacity is in a ratio with the size of the brain, compared to that of the rest ofthe body. " Let it not be believed," says a distinguished writer,b " an affair of accident, that a head of considerable dimensions is found, from time to time, to coincide with a distinguished genius. Although the amour propre may object, the law is general. I have neither met in antiquity, nor in modern times, a man of vast genius, whose head ought not to be ranged in the latter class, which I have just established, especially if attention be paid to the great development of the forehead. Look at the busts and engravings of Homer, Socrates, Plato, De- mosthenes, Pliny, Bacon, Sully, Galileo, Montaigne, Corneille, Racine, Bossuet, Newton, Leibnitz, Locke, Pascal, Boerhaave, a Thus Shakspeare: " We shall lose our time, And all be turn'd to barnacles, or to apes, With foreheads villanous low." Caliban, in " Tempest." — Act iv. And again: — " Ay, but her forehead's low, and mine's as high." Julia, in the " Two Gentlemen of Verona." — Act iv. b Gall, Sur les Fonctions du Cerveau, ii. 312, Paris, 1825. 23* 270 MENTAL FACULTIES. Haller, Montesquieu, Voltaire, J. J. Rousseau, Franklin, Diderot, Stoll, Kant, Schiller, &c. Yet we are not always accurate in estimating the size of the brain from the development of the head. Dr. Sewall3 has clearly shown, that skulls ofthe same dimensions, as measured by the craniometer, differ largely as to the quantity of cerebral substance which they are capable of containing. With the assistance of Dr. Thomas P. Jones, of Washington, and of Professor Ruggles,of the Columbian College, he instituted various experiments. In the first series, he ascertained the volume of each skull, brain included ; in the second series, the volume of-the brain alone, or the capacity of the cere- bral cavity ; and in order to render the difference in capacity more obvious, the volume of each skull, brain included, was reduced to the dimensions of 70 fluid ounces. The results of the experiments on five skulls, delineated in the plates of Dr. Sewall's work, were as follows: Volume of Skull, Brain included. Volume of Brain. Plate II. ... 70 oz. - - - - 56-22 oz. III. .... do. - - - - 51-72 IV.....do. .... 46-21 V. .... do. - - - - 34-79 VII.....do. .... 25-33 In two of these skulls, consequently, of the same external dimen- sions, there was a difference in the volume of brain of 31-S9 oz. Dr. Sewall infers from his observations, that no phrenologist, how- ever experienced, can, by any inspection ofthe living head, ascer- tain whether a person has a skull of one inch or one-eighth of an inch in thickness; or whether he has 56-22 ounces of brain, or only 25-33 ounces. To the view that the mental capacity is in a ratio with the size of the brain there must be numerous exceptions; for, indepen- dently of bulk, there may obviously be an organization, productive of the same results, and in which the largely developed organ may be greatly deficient. Size is only one of the elements of the activity of an organ. The difference between the moral of the male and the female is signal; and there is no less in the shape of the encephalon in the two sexes. Observation, not only by anatomists but by sculptors and painters, shows, that the superior and'anterior parts ofthe brain are less developed in the female, whose forehead is, therefore, as a general rule, smaller ; and that the posterior parts are larger than in the male. In the system of Gall, the anterior and superior parts are considered to be connected with the intellectual manifestations, which are more active in man ; whilst the posterior are concerned in the softer feelings, which predominate in the character of the female. The mental and moral faculties vary, also, in the same individual, according to age, health and disease; and in the waking and sleeping state. In all these conditions, we have reason 1 An Examination of Phrenology, in two Lectures, 2d edit. p. 66, Boston, 1839. MENTAL FACULTIES. 271 to believe, that the state of the encephalon is as various. The anatomist notices a manifest difference between its organization in the infant and in the adult or the aged. Like the other organs of the body, it is gradually developed until the middle period of life; after which it decays along with the rest of the frame. Our ac^ quaintance with the minute organization of the body does not enable us to say on what changes these differences are dependent. We see them only in their results. By the minutest examination of the special nerves of the senses we are incapable of saying, why one should be able to appreciate the contact of sapid bodies — another that of light, &c. During sleep, again, in which the func- tions of the brain are more or less suspended, the condition of the organ is modified ; and mania or delirium probably never occurs, without the physical condition ofthe brain having undergone some change, directly or indirectly. It is true, that, on careful exami- nation of the brains of the insane, it has often happened that no morbid appearance has presented itself; but the same thing has been observed on inspecting those, who have died of apoplexy or paralysis; in which cases, not a doubt is entertained that the cause is seated in the encephalon, and that it consists in a physical altera- tion of its tissue. These are a few of the cases, which make us sensible of the limited nature of our powers of observation. They by no means encourage, in the most skeptical, the belief, that the tissue of the organ is not implicated. The investigations of the morbid anatomist consequently afford us but few data, on which to form our opinions on this subject. The effect of intoxicating substances must be mainly exerted on the brain. When taken in moderation, we find all the faculties excited ; but, if pushed too far, the intellectual and moral manifes- tations become perverted. This can only be through the action of those substances upon the cerebral organ. We can thus under- stand, how regimen may cause important modifications in the brain. Climate has probably a similar influence : hence, the dif- ference between the characters of different nations and races. The skull of the Mongol is strikingly different from that of the Kelto- Goth or of the Ethiopian ; and the brain, as well as its functions, exhibits equal diversity. Again, it has been argued, that the facts we notice in the animal kingdom are in favour of the brain being the organ concerned in the manifestations of the mind ; that, if each animal species has its own psychology, in each the encephalon has a particular organization ; and that, in all those which exhibit superior powers, the brain is found large and more complicated. To a great extent this is doubtless true. Nothing, indeed, seems more erroneous than the notion, that even sensibility to pain is equal in every variety of the animal creation. As we descend in the scale, we find the nervous system becoming less and less complicated, until ulti- mately it assumes the simple original character, which has laid the foundation for one of the divisions of Sir Charles Bell's sys- 272 MENTAL FACULTIES. tern; and although it is impossible to change places with the ani- mal, we have the strongest reasons for believing, that the sensi- bility diminishes as we descend ; and that the feeling, expressed by the poet, that the beetle, which we tread upon — " In corporal sufferance finds a pang as great As when a giant dies" — however humane it may be, is physiologically untrue. The frog will continue sitting, apparently unconcerned, for hours after it has been eviscerated; the tortoise walks about after losing its head; and the polypus, when divided by the knife, forms so many sepa- rate animals. Redi removed the whole of the brain from a com- mon land tortoise: the eyes closed to open no more, the animal walked as before, but, as it were, groping its way for want of vision. It lived nearly six months after. All have noticed the independence of the parts of a wasp, when the head has been severed from the body. The head will try to bite, and, for a con- siderable period, the abdomen will attempt to sting. An illustrative instance of this kind occurred to Dr. Harlan.3 He cut off the head of a rattlesnake, and grasping the part of the neck, attached to the head, with his finger and thumb, the head twisted itself violently, endeavouring to strike him with its fangs. A live rabbit was after- wards presented to the head, which immediately plunged its fangs deep into the rabbit; and when the tail was laid hold of, the head- less neck bent itself quickly round as if to strike him. The instances of a similar kind, which occur to the naturalist, are numerous and interesting; and afford signal evidence of crea- tive wisdom, in endowing the frames of those beings of the animal kingdom, that are most exposed to injury and torture, with a less sensible organization. On all the above accounts, then, we may conclude, — that the brain is the organ, through which the mind acts, in the production of the different mental and moral manifes- tations.b Yet, amongst those who admit the accuracy of this con- clusion, a difference of sentiment exists : some conceiving that other organs participate in the function. Some have ascribed to each of the known temperaments as many intellectual and moral dispositions. Others have affirmed, that, if the brain be manifestly the organ of the intellect, the passions must be referred to the organs of internal or organic life ; whilst others, again, have con- sidered the brain as a great central apparatus, for the reception and elaboration of the different impressions, made upon the exter- nal senses; thus conceiving the latter to be direct agents in the execution of the function, as well as the brain. The influence of the temperaments upon the mental and bodily powers is much less invoked at the present-day than it was of old. The ancients regarded organized bodies as an assemblage of ele- ments,endowedwith different qualities, but associated and combined a Medical and Physical Researches, p. 503, Philad. 1835. b Gall, Sur les Fonctions du Cerveau, ii. 69, Paris, 1825; Adelon, art. Encephale, Diet, de Medec. vii. 517; and Physiologie de l'Homme, ed. cit. i. 496. MENTAL FACULTIES. 273 so as to moderate and temper each other. Modern physiologists mean, by the term, the reaction of the different organs of the body upon each other, consistent with health; so that if one set or appara- tus of organs predominates, the effect of such predominance may be exerted on the whole economy. In the description of the tem- peraments, in different authors, we find a particular character of intellectual and moral faculties assigned to each. The man ofthe sanguine temperament is described as of ready conception, reten- tive memory, and lively imagination, inclined to pleasure, and generally of a good disposition, but inconstant and restless. He of the bilious, on the other hand, is said to be hasty, violent, ambi- tious, and self-willed; whilst the lymphatic bestows feeble pas- sions, cold imagination, tendency to idleness ; and the ^melancholic disposes to dulness of conception, and to sadness and moroseness of disposition. Galla has animadverted on this assignment of any intellectual or moral faculty to temperament. If we look abroad, he affirms, we find the exceptions more numerous than the rule itself; so numerous, indeed, as to preclude us from establishing any law on the subject; and, moreover, the idiot, who possesses a temperament like other persons, has no intellectual faculties. The temperament doubtless influences the brain within certain limits, as it does other functions : this, he suggests, it probably does by impressing them with a character of energy or of languor, but without, in any respect, regulating the intellectual sphere of the individual; and it may be regarded as one of the media of con- nexion between the mind and the body. Bichat,b again, maintained, that whilst the encephalon is evi- dently the seat of the intellectual functions, the organic nervous system, and, consequently, the different organs of nutrition, which are supplied from this system, are the seat of the emotions or pas- sions. That distinguished physiologist, than whom, as Corvisart wrote to the First Consul, in announcing his death, " personne en si peu de temps n'a fait tant de choses et aussi bien,,,K rests his views upon the three following considerations: — 1st. That whilst inward feeling induces us to refer the intellectual acts to the brain, the passions are felt in the viscera of the thorax or abdomen. 2dly. That the effects of intellectual labour are referred to the encephalon, as indicated by the redness and heat of the face and the beating of the temporal arteries, in violent mental contentions, &c.: whilst the passions affect the organic functions, the heart is oppressed, and its pulsations are retarded or suspended ; the respi- ration becomes hurried and interrupted; the digestion impeded or deranged, &c.; and, 3dly. That whilst our gestures and lan- guage refer the intellect to the encephalon, they refer the emotions to the nutritive organs. If, we wish to express any action of the mind, or are desirous of recalling something that has escaped the memory, the hand is carried to the head, and we are in a con- a Op. citat. ii. 140. L Sur la Vie et la Mort, Part i., Paris, 1806. c Elogo de Xavier Bichat, par Miquel, p. 58, Paris, 1823. 274 MENTAL FACULTIES. stant habit of designating a strong or weak intellect by the terms a "strong or weak head;" and we say, that the possessor has " much or little brain." On the other hand, if we be desirous of depicting the passions, the hand is carried to the region of the stomach or heart; and the possessor of benevolent or uncharitable sentiments is said to have a good or a bad heart. Bichat properly adds, that this idea is not novel, inasmuch as the ancients con- ceived the seat of the passions to be in the epigastric centre; that is, in the nervous plexuses situate in that region: he remarks, that, amidst the varieties presented by the passions, according to age, sex, temperament, idiosyncrasy, regimen, climate, and dis- ease, they are always in a ratio with the degree of predoniinance of the different nutritive apparatuses; and he concludes with a deduction, which ought not to have been hazarded without full reflection — that as the functions of the nutritive organs, in which he ranges the passions, are involuntary, and consequently unin- fluenced by education, education can have no influence over the passions, and the disposition is consequently incapable of modifi- cation. The answer of Gall* and Adelonb to the views of Bichat appears to us irrefragable. How can we conceive that viscera, whose functions are known, and which differ so much from each other, are the agents of moral acts ? The passions are sensorial phenomena, and like all phenomena of the kind must be pre- sumed to be seated in essentially nervous organs. Again, when an injury befals the brain, and the intellectual faculties are per- verted or suspended by it, the same thing happens to the affec- tive faculties; and if the viscera fulfil the high office assigned to them, why are not the passions manifested from the earliest infancy, a period when the viscera are in existence and very active ? The argument of Bichat — that the phenomena which attend and succeed to the passions, are referable to the or- gans of internal life—is not absolute. The functions of animal life are frequently disturbed by the passions, as well as those of or- ganic life. It is not uncommon for them to induce convulsions, mania, epilepsy, and other affections of the encephalon. The effect here, as Adelon remarks, is mistaken for the cause. The heart certainly beats more forcibly in anger, but the legs fail us in fear ; and if we refer anger to the heart, we must, by parity of reasoning, refer fear to the legs. By reasoning of this kind, the passions might be referred to the whole system, as there is no part which does not suffer more or less during their violence. The error arises from our being impressed with the most prominent effect of the passion — the feeling accompanying it — and this is the cause of the gesture and the descriptive language, to which Bichat has given unnecessary weight in his argument. If, then, the views of Bichat a Op. citat. i. 94. b Art. Enceph. (Physiol.) in Diet, de Med. vii. 521, and Physiologie de l'Homme, edit. cit. i. 510. ORGAN OF INTELLECT. 275 regarding the seat of the passions, be unfounded, the mischievous doctrine deduced from them—that they are irresistible, and can- not be modified by education — falls to the ground. His notion was, that the nutritive organs are the source of irritative irradia- tions, which compel the brain to form the determinations that constitute the passion, and to command the movements by which it is appeased or satisfied. A similar view is embraced by Brous- sais,* who, however, conceives, that the passions can be fomented and increased by attention, until they become predominant. Daily experience, indeed, shows us the powerful effect produced on the passions by a well-directed moral restraint. How many gratifying instances have we of persons, whose habitual indulgence of the lowest passions and propensities had rendered them outcasts from society, having become restored to their proper place in the com- munity by exerting the due control over their vicious inclinations and habits ! We can not only curb the expression of the passions, as we are constantly compelled to do in social intercourse ; but we can even modify the internal susceptibility, by well-directed habits of repression. Lastly. Many physiologists, we have seen, have considered the brain as a great nervous centre for the reception and elaboration of the different impressions, conveyed thither by the external senses; and absolutely requiring such impressions for the mental manifes- tations. They consequently rank, amongst the conditions necessary for such manifestations, not only the brain which elaborates them, but the parts that convey to it the impressions or materials on which it has to act; and they conceive, that a necessary connexion exists between these two orders of parts. The supporters of these opinions ascribe the differences, observed in the intellectual and moral faculties of different individuals, as much to diversity in the number and character of the impressions, as to differences in the encephalon itself. They do not all, however, agree as to the source of the impressions, which they conceive to be the raw material for the intellectual and moral manifestations. Condillacb and his school admit only one kind; — those proceeding from the external senses; and which they term external impressions. Cabanis,c on the other hand, in addition to these, admits others proceeding from every organ in the body, which he terms internal impressions, in contra- distinction to the first. The school of Condillac set out with the maxim ascribed to Aris- totle, " nihil est in intellectu quod non prius fuerit in sensu ;" and they adopt, as an elucidation of their doctrine, the ingenious idea of Condillac — of a statue, devoid of all sensation, which is made to receive each of the five senses in succession ; and which, he attempts to show, from the received impressions, can gradually 1 Examen des Doctrines Me"dicales, ii. 388, and Physiology applied to Pathology, Drs. Bell and La Roche's translation, p. 136, Philadelphia, 1832. b Traite des Sensations, torn. i. 119. c Rapport du Physique et du Moral de l'Homme, 4eme edit, par G. Pariset, Paris, 1824. 276 MENTAL FACULTIES. develope the different intellectual and moral faculties. All these, he affirms, are derived from the impressions made on the external senses; and he considers, that the whole of human consciousness is mere sensation variously transformed. The views of Condillac have been largely embraced, with more or less modification; and, at the present day, many metaphysi- cians believe, that the impressions of the senses are the necessary and exclusive materials for all the intellectual acts. Condillac's case ofthe statue seems, however, to be by no means conclusive. It must, of course, be possessed of a centre for the reception of the impressions made upon the different senses, otherwise no percep- tion could occur; and if we can suppose it possible for such a monstrous formation, as a being totally devoid of the -external senses, to exist, such a being must not only be defective in the nerves which, in the perfect animal, are destined to convey the impressions to the brain, but probably in the cerebral or percipient part likewise. From defective cerebral conformation, therefore, the different mental phenomena might not be elicited.3 If, how- ever, we admit in such case the possibility of the cerebral struc- ture,— particularly those portions that are especially concerned in the function of thought, — being properly organized, it appears to us, that certain mental or moral manifestations ought to exist- Of course, all knowledge ofthe universe would be precluded, because deprived of the instruments for obtaining such knowledge ; but the brain would still act, as regarded the internal sensations. In order that such a being may live, he must be supplied with the necessary nourishment; he must possess all those internal sensa- tions or wants that are inseparably allied to organization; he must consequently feel the desires of hunger and thirst: but we have seen that these sensations require the intervention of the brain as much as the external sensations. Supposing him, again, to sur- vive the period of puberty, he must experience the instinctive changes, that occur at this period, and which are doubtless de- pendent upon encephalic organization. In this assumed case, then, a certain degree of mental action might exist; and, under the supposition of a properly organized brain, ideas — limited, it is true, in consequence ofthe privation ofthe ordinary inlets of know- , ledge — might be formed; and memory, imagination, and judg- ment, be compatible within certain limits. The objections to the idea, that the intellectual and moral sphere of man and animals is proportionate to the number and perfection of the external senses are overwhelming.11 Many animals have the same number of senses as man, and frequently have them more perfect; yet, in none is the mental sphere co-extensive. The idiot, too, has the external senses as delicate as the man of genius, and often much more so ; many of those of the greatest talents having the senses extremely obtuse. It has been already remarked, that the superiority of the human intellect has been referred entirely to 1 Adelon, op. citat. i. 519. b Helvetius, De l'Homme, &c, torn. i. MENTAL SPHERE OF THE DEAF AND DUMB. 277 the sense of touch, and to the happy organization of the human hand; but the case of Miss Biffin, and others, and that of the young artist cited by Magendie,3 completely negative this presump- tion. The senses are important secondary instruments, indispen- sably necessary for accomplishing certain faculties of the mind ; but, in no way, determining its power. The example of the deaf and dumb is illustrative of this matter.b If a child be born deaf, he is necessarily dumb, inasmuch as he is unable to hear those sounds which, by their combination, consti- tute language, and he cannot therefore imitate them ; yet this con- nexion between the functions of hearing and speech was not well known to the ancients. For a length of time, these objects of compassionate interest were esteemed to be beyond the powers of any kind of intellectual culture, and were permitted to remain in a state of the most profound ignorance. The ingenuity of the scientific philanthropist has, however, devised modes of instruc- tion, by which their mental manifestations have been exhibited in the most gratifying manner, and in one which proves that the sense of hearing is not absolutely necessary for mental development; but that its place may be supplied, to a great extent, by the proper exercise of others. The deaf and dumb, being deprived of the advantages of spoken language, are compelled to have recourse to the only kind available to them — that addressed to the eye. In this typical way, by a well-devised system of instruction, they can be taught to preserve their ideas, and to multiply them, as we do, by t wo combined methods — the spoken and the written language — without one or the other of which the human mind would have remained in perpetual infancy. Thus, the deaf and dumb have not only our ideas, but the same words to convey them to others. Yet the deaf and dumb are not so much the objects of our com- miseration as those who have been deprived, from birth or from early infancy, of both the senses of sight and hearing, and who have thus been devoid of two ofthe most important inlets for the entrance of impressions from the surrounding world. In such case, it is obvious, they are shut out from all instruction, except what can be afforded by the senses of touch, smell, and taste ; yet even here we have the strongest evidence of independent intellect. One of the most striking cases of this kind is that of the Scottish boy Mitchell, the object of much interest to Spurzheim and to Dugald Stewart,0 both of whom have described his case in their writings. It is matter of uncertainty, whether either his deafness or blindness was total. The evidences of the sensation of hearing were, in a high degree, vague and unsatisfactory, but he gave more convincing proofs of the possession of partial vision. He could, for example, distinguish day from night; and, when quite young,amused himself a See page 107 of this volume. b Gall, op. cit. i. 119. c Elements ofthe Philosophy ofthe Human Mind, &c.; Transactions ofthe Royal Society of Edinburgh, vol. vii.; and Dr. Gordon, ibid. vol. vi.; also, History of James Mitchell, a boy born blind and deaf, by James Wardrop, London, 1813. VOL. I.— 24 278 MENTAL FACULTIES. with looking at the sun through crevices in the door,and by kindling a fire. At the age of twelve, the tympanum of both ears was perforated, but without any advantage. In his fourteenth year, the operation for cataract was performed on the right eye, after which he recognised more readily the presence of external objects, but never made use of his sight to become acquainted with the qualities of bodies. Before and after this period, red, white, and yellow particularly attracted his attention. The senses, by which he judged of external bodies, were those of touch and smell. His desire to become acquainted with objects was signal. He exa- mined every thing he met with, and every action indicated reflec- tion. In his infancy, he smelt at everyone who approached him, and their odour determined his affection or aversion. He always recognised his own clothes by their smell, and refused to wear those which he found to belong to others. Bodily exercises, such as rolling down a small hill, turning topsy-turvy, floating wood or other objects on the river that passed his father's house, gathering round, smooth stones, laying them in a circle, and placing himself in the middle, or building houses with pieces of turf, &c, were always a source of amusement to him. After the operation on his right eye, he could better distinguish objects. His countenance was very expressive, and his natural language was not that of an idiot, but of an intelligent being. When hungry, he carried his hand to his mouth, and then pointed to the cupboard, where the provisions were kept; and, when he wished to lie down, he re- clined his head on one side upon his hand, as if he wished to lay it upon the pillow. He easily recollected the signification of sounds that had been taught him, all of which were of course of the tac- tile kind. To make him comprehend the number of days before an event would happen, they bent his head as a sign that he would have to go to bed so many times. Satisfaction was expressed by patting him on the shoulder or arm, and discontent by a sharp blow. He was sensible to the caresses of his parents, and sus- ceptible of different emotions — of hatred, passion, malice, and the kindlier feelings. He was fond of dress, and had great fears of death, of the nature of which he had manifestly correct notions. Mitchell's case has been pregnant with interest to the metaphysi- cian, but it is not so elucidative as it would have been had the privation of the senses in question been total. There is, in the American Asylum at Hartford in Connecticut, a being, not less deserving of attention, than the one to whom allu- sion has just been made.3 Her name is Julia Brace. She is the daughter of John and Rachel Brace, natives of Hartford, and was born in that town in June, 1807 ; so that she is now, (1843,) thirty- six years old. At four years of age she was seized with typhus fever ; was taken sick on the evening of Monday, November 29, 1811, and, on the Saturday morning following became both blind a Twenty-first Report ofthe Directors ofthe American Asylum at Hartford, for the Education and Instruction of the Deaf and Dumb, p. 15, Hartford, 1837. MENTAL SPHERE OF THE DEAF, DUMB AND BLIND. 279 and deaf Prior to her illness, she had not only learned to speak, but to repeat her letters, and to spell words of three or four sylla- bles ; and, for some time after the loss of her sight and hearing, she was fond of taking a book, and spelling words and the names of her acquaintances. She retained her speech pretty well for about a year, but gradually lost it, and appears to be now con- demned to perpetual silence. For three years she could still utter a few words, one of the last of which was " mother.'" At first she was unconscious of her misfortune, appearing to think, that a long night had come upon the world; and often said, <; It will never be day." She would call upon the family to " light the lamp," and was impatient at their seeming neglect, in not even answering her. At length, in passing a window, she felt the sun shining warm upon her hand, and pointed with delight to indicate that the sun shone. From the January after her illness, until the following August, she would sleep during the day, and be awake through the night; and it was not until autumn, by taking great pains to keep her awake during the day, that she was set right. At present, she is as regular in this respect as other persons. From the period of her recovery, she seemed to perceive the return of Sabbath; and, on Sunday morning, would get her own clean clothes, and those of the other children. If her mother was reading, she would find a book, and endeavour to do so likewise. The intervention of a day of fasting or thanksgiving confused her reck- oning, and some time elapsed before she got right. During the first winter after her recovery, she was irritable almost to madness; would exhibit the most violent passion, and use the most profane language. The next summer she became calmer; and her mother could govern her, to some extent, by shaking her, in sign of dis- approbation ; and stroking or patting her head, when she con- ducted herself well. She is now habitually mild, obedient, and affectionate. During the first summer after her illness, she was very unwilling to wear clothes, and would pull them off violently. At length, her mother took one of her frocks and tried it on her sister, with a view of altering it for her. Julia had ever been re- marked for her sense of justice in regard to property. This seemed to be awakened, and she took the frock and put it on herself. After this she was willing to wear clothes, and even cried for new ones. She has ever since been fond of dress. At nine years of age, she was taught to sew ; and, since that time, has learned to knit. She has been a resident for several years in the American Asylum at Hartford, where she is supported in part, by the volun- tary contributions of visiters; and, in part, by her own labours in sewing and knitting. A language of palpable signs was early established, as a means of communication with her friends; and this has been so improved as to be sufficient for all necessary pur- poses. Her countenance, as she sits at work, is said to exhibit the strongest evidence of an active mind, and a feeling heart: " thoughts and feelings," says a writer who describes her case, 280 MENTAL FACULTIES. " seem to flit across it like the clouds in a summer sky: a shade of pensiveness will be followed by a cloud of anxiety or gloom ; a peaceful look will perhaps succeed ; and, not unfrequently, a smile lights up her countenance, which seems to make one forget her misfortunes. But no one has yet penetrated the darkness of her prison house, or been able to find an avenue for intellectual or moral light. Her mind seems, thus far, inaccessible to all but her Maker." A still more interesting example is cited by Dr. Abercrombie,8 from the Medical Journals of the time. A gentleman in France is asserted to have lost every sense except the feeling of one side of his face ; yet his family acquired a method of holding commu- nication with him, by tracing characters upon the part which re- tained its sensation. These cases are not, perhaps, so unfrequent as has been supposed. Dr. Howe, the superintendent of the Per- kins Institution and Massachusetts Asylum for the Blind, states, that four cases in New England, besides that of Julia Brace, have come within his own observation. One of these had been in 1S41 upwards of three years under his care; and the results of his diligence and judgment in this instance have furnished more grati- fying results to the psychologist and philanthropist than any other, perhaps, on record. Laura Bridgman, the subject of the case, was born in Decem- ber, 1829 ; at two years of age, her eyes and ears inflamed, sup- purated, and their contents were discharged. At the expiration of two more years of suffering, it was discovered, that her sense of smell was almost wholly destroyed, and, consequently, that her taste was much blunted. She had, therefore, but one sense re- maining — that of touch — by which she could become acquainted with the external world. Whilst at home, before her reception into the Asylum, she would explore the house, become familiar with the form, density, weight, and temperature of every article she could lay her hands upon; followed her mother,felt her hands and arms, and endeavoured to repeat every thing herself. She even learned to sew a little, and to knit. She exhibited warm affection towards the members of her family ; but the means of communicating with her were limited. When it was desired, that she should go to a place, she was pushed; or, that she should approach, she was drawn towards the person. Gently patting on the head signified approbation ; on the back, disapprobation. She had made, however, a natural language of her own, and had a sign to express her idea of each member of the family, — such as drawing her finger down each side of her face, to allude to the whiskers of one ; twirling her hand and arm around, in imitation of the motion of the spinning-wheel, for another, &c. In October, 1837, she was received into the Institution for the Blind, in Boston. The first experiments made with her consisted 11 Inquiries concerning the Intellectual Powers, &c., Amer. Edit, p. 56, New York, 1832. MENTAL SPHERE OF THE DEAF, DUMB AND BLIND. 281 in taking articles in common use, such as knives,forks, spoons, keys, &c, and pasting labels upon them with their names printed in raised letters. These she felt very carefully, and speedily found, that the crooked lines spoon differed as much from the crooked lines k e y, as the spoon differed from the key in form. Then small detached labels, with the same words printed upon them, were put into her hands, and she soon observed, that they were similar to the ones pasted on the articles. She showed her per- ception of this similarity by laying the label key upon the key, and the label spoon upon the spoon. In this manner she pro- ceeded to acquire a knowledge of language; and now she uses the manual alphabet of the deaf mutes with great facility and rapidity : she has increased her vocabulary so as to comprehend the names of all common objects. She can count to high numbers: she can add and substract small numbers. But the most gratify- ing acquirement which she has made, and the one which has given her the most delight, is the power of writing a legible hand, and expressing her thoughts upon paper. She writes with a pen- cil in a grooved line, and makes her letters clear and distinct. She is very expert with her needle ; knits very easily, and can make twine bags and various fancy articles very prettily ; is very docile; has a quick sense of propriety ; dresses herself with great neatness, and is always correct in her deportment. No definite course of instruction can be marked out; for her inquisitiveness is so great, that she is very much disconcerted if any question, which occurred to her, is deferred until the lesson is over. It is deemed best to gratify her, if her inquiry has any bearing on the lesson ; and often she leads her teacher far away from the objects with which he commenced. With regard to the sense of touch it is very acute, even for a blind person. It is shown remarkably in the readiness with which she distinguishes persons. There are forty inmates in the female wing, with all of whom, of course, she is acquainted; whenever she is walking through the passage-way, she perceives by the jar of the floor, or the agitation of the air, that some one is near her, and it is exceedingly difficult to pass her without being recognised. Her arms are stretched out, and the instant she grasps a hand; a sleeve, or even-part ofthe dress, she knows the person and lets them pass on with some sign of recognition. The details concerning this interesting being, and her gradual progress in moral and intellectual culture, can be learned from the annual reports ofthe Institution which Dr. Howe superintends.3 How strongly do these cases demonstrate the independence of the organ of intellect: requiring, indeed, the external senses for its perfect development, but still capable of manifesting itself with- out the presence of many, and probably of any, of them; and how inaptly, although humanely, does the law regard such beings ! "A a Annual Reports of the Trustees of the Perkins Institution, and Massachusetts Asylum lor the Blind to the Corporation, for the years 1837,1838, 1839,1840,&c.,&c. 24* 282 MENTAL FACULTIES. person," says Blackstone,3 " born deaf, dumb, and blind,\s looked upon by the law as in the same state with an idiot, he being sup- posed incapable of any understanding, as wanting all those senses which furnish the human mind with ideas." But if he grow deaf, dumb, and blind, not being born so, he is deemed non compos mentis, and the same rules apply to him as to other persons sup- posed to be lunatics. With regard to the deaf and dumb, they are properly held to be competent as witnesses, provided they evince sufficient understanding, and to be liable to punishment for a breach of the criminal laws. Cabanisb embraces the views of Condillac regarding the external senses; but he thinks, that the impressions from these are insuffi- cient to constitute the materiel of the mental and moral manifes- tations. In confirmation of this opinion, he observes, that the young infant, and animals at the very moment of birth, frequently afford evidences of complicated intellectual processes ; and yet the exter- nal senses can have been scarcely at all impressed. How can we, he asks, refer to the operation of the external senses the motions of the foetus in utero, which are perceptible to the mother, for the latter half of utero-gestation : or the act of sucking executed from the first day of existence ? Can we refer to this cause the fact of the chick, as soon as it is hatched, pecking the grain that has to nourish it ? or that, so frequently quoted from Galen, ofthe young kid, scarcely extruded from the maternal womb, which was able to select a branch of the cytisus from other vegetables presented to it ? Man and animals, continues Cabanis, during the course of their existence, experience mental changes as remarkable as they are frequent; yet nothing in the condition of the senses can account for such difference. For example, at the period of puberty, a new appetite is added; and this, even, when the being is kept in a complete state of isolation. This, he argues, it is impossible to refer to any change in the external senses; which, if they furnished the materials at all, must have been doing so from early infancy ; and he concludes, that the difference observable in the mental mani- festations, according to sex, temperament, climate, state of health or disease, regimen, &c, cannot be referable to the senses, as they remain the same ; and that, consequently, we must look elsewhere for the causes of such difference. These Cabanis conceives to be the movements by which the organs of internal life execute their functions. Such movements, he says, although deep-seated and imperceptible, are transmitted to the brain, and furnish that organ with a fresh set of materials. At puberty, for example, when the testicles become developed, and their function is established by the secretion of sperm, the organic movements in the process of this secretion are the materials of the new desires, which appear at that age. These impressions Cabanis calls internal, in contradis- tinction to the external, or those furnished by the five senses ; and he considers, that, whilst the external senses serve as the base of all a Commentaries on the Laws of England, i. 304. b Rapport du Physique et du Moral, edit. cit. VIEWS OF CABANIS. 283 that we include under the term intellect, the internal impressions are the materials of what are called instincts ; and, as the organs ot internal life, whence the internal impressions proceed, vary more than the senses, according to age, sex, temperament, climate, re- gimen, &c., it is more easy, he thinks, to find in them organic modifications, which coincide with those exhibited by the mind under these various circumstances. In proof of these opinions, Cabanis adduces, besides others, the following specious affirmations. First. As the venereal appetite appears in man and animals synchronously with the development of the testicles, and is never exhibited when the testicles are re- moved in infancy, we have reason to believe, that the impressions, which constitute the materials for this new catenation of ideas, must proceed from the testicles. Secondly. Numerous facts demon- strate, that the condition of the uterus has much influence on the mental and moral manifestations of the female. For example, the period ofthe development of that organ is the one at which new feelings arise, and when the whole of those manifestations assume more activity ; and there is generally a ratio between their activity and that of the uterus. If the state of the uterus be modified, as it is at the menstrual period, or during pregnancy, or after delivery, the mind is so likewise. All these facts ought to induce a belief, he thinks, that impressions are continually emanating from this organ, which, by their variety, occasion the diversity in the state of mental and moral faculties, observed in these different cases. Thirdly. It is impossible in the hypochondriac and melancholic con- stitutions, to mistake the influence exerted upon the mind by the ab- dominal organs ; according as these organs execute their functions more or less perfectly, the thinking faculty is more or less languid or brilliant; and the affections are more or less vivid and benevolent, or the contrary; hence the expressions melancholy* and hypochon- driasis^ assigned to the state of mind characterizing these consti- tutions, and which denote that the cause must be referred to the organs of the abdomen. The origin of the alternations of inactivity and energy in the intellect, of benevolent and irascible fits of hu- mour, as well as of insanity, are also referable, he says, to the ab- dominal viscera. Hence, Cabanis concludes,it is evident that the ab- dominal organs are to the brain the source of fortuitous and abnor- mous impressions, which excite it to irregular acts ; and is it not,' he asks, probable, that what takes place in excess, in these morbid movements, may happen to a less and more appropriate extent in a state of health ; and that thus impressions may emanate, in a continuous manner, from every organ of the body, which may be indispensable to the production of the mental and moral faculties ? Cabanis, therefore, considers that the axiom of Aristotle should be extended; and that the statue of Condillac is incomplete, in not having internal organs for the emanation of the internal impres- sions, which are the materials of the instincts. In this way he * From y.ihdL(, " black," and xo\», " bile." b Disease of the hypochondres. 284 MENTAL FACULTIES. accounts for the instincts, which, by some metaphysicians, have been looked upon as ordinary judgments, so rapidly executed, that the process has ceased from habit to be perceptible. Finally, he remarks, there is a ratio between the duration and intensity ofthe intellectual results and the kind of impressions, which have con- stituted the materials of them. All the mental and moral acts, for instance, that are derived from impressions engendered in the very bosom of the nervous system or in the brain, — such as those of the maniac, — are the strongest and most durable. After these come the instincts, of which the internal impressions are the mate- rials. They are powerful and constant. Lastly; the acts of the in- tellect are more transient, because they emanate from the external impressions, which are themselves fickle, and somewhat superficial. According to the views, then, of Cabanis and his followers, amongst the organic conditions of the mental and moral mani- festations must be placed, not only the encephalon and the external senses, but the different organs of the body, which fur- nish the different internal impressions. The influence of the ex- ternal senses on the intellectual and moral development has already been canvassed: we have seen, that they are only secondary instruments for making us acquainted with external bodies, but in nowise regulate the intellectual or moral sphere. The notion of internal impressions is ingenious, and has led to important improve- ments in the mode of investigating the different mental and moral phenomena. It was suggested, as we have seen, by Cabanis, in consequence of the external senses appearing to him insufficient to explain all the phenomena. By Gall, Adelon,3 and others, how- ever, all these cases are considered explicable by the varying con- dition of the brain itself. In the foetus in utero, in the new-born animal, there are already parts of the brain, they say, sufficiently developed and capable of action ; and, accordingly, we witness the actions to which reference has been made by Cabanis ; and if the intellectual and moral manifestations vary according to sex, temperament, climate, regimen, state of health, &c, it is because the encephalon is, under these circumstances, in different condi- tions. The chief facts, on which Cabanis rests his doctrine, are, — the coincidence between the development ofthe testicle and the appearance of the venereal appetite ; and the suppression of this appetite after castration. It must be recollected, however, that these are not the only changes, that happen simultaneously at puberty. The voice also assumes a very different character; but the change in the voice is not a cerebral phenomenon. It is depend- ent upon the development of its organ, the larynx. Yet castra- tion, prior to puberty, has a decided effect upon it; preventing it from becoming raucous and unmelodious. All these developments are synchronous, but not directly consequent upon each other. The generative function has two organs, — one encephalic, the other external ; and it is not surprising, that both of these should * Physiologie de l'Homme, 2de e"dit. i. 251. PHYSIOLOGY OF THE MENTAL FACULTIES. 285 undergo their development at the same period. We shall see hereafter, that Gall offers reason for believing, that the instinct of propagation has its seat in the cerebellum; and as the most intimate connexion and dependence must exist between the ence- phalic and the external apparatus, it would not be surprising, that the removal of the latter should prevent the development of the former, and of the instinct of which it is the organ. If, however, the operation of castration be performed after puberty, the instinct need not be suppressed, because the necessary development has already taken place,and the cerebellum may be in a condition for fulfilling the function. The continuance of the instinct, however, under such circumstances, Adelon conceives to be strong evidence against the existence of such internal impressions ; whilst the influence which Cabanis has ascribed to the uterus in females, and to the abdominal organs in the melancholic and hypochondriac, have been esteemed to belong to that excited by the temperament, or by the different organs of the body on the brain ; a subject which has already fallen under discussion. On the whole, then, we are perhaps justified in concluding, that the encephalon alone is the organ of the intellectual and moral faculties. The interesting topic of the various instinctive opera- tions of the frame will be considered in another part of this work. We shall there find, that instinct cannot well be defined, in the language of Broussais,3 to consist in sensations originating in the internal and external sensitive surfaces, which solicit the cerebral centre to acts necessary for the exercise of the functions — such acts being frequently executed without the participation of the mind, and even in its absence — inasmuch as it is not confined to beings possessed of brain, but exists also in the vegetable. Having now decided upon the organ of the mental and moral faculties, according to the system adopted in this work, it would be necessary to describe its anatomy ; but this has been done elsewhere. 1. PHYSIOLOGY OF THE INTELLECTUAL AND MORAL FACULTIES. When the organ of the intellect is exposed by accident, and we regard it during the reception of a sensation, the exercise of voli- tion, or during any intellectual or moral operation, the action is found to be too molecular to admit of detection. At times, during violent mental contention, a redness has been apparent, as if the blood were forced more violently into the vessels; but no light has been thrown by such examinations on the wonderful ac- tion, which constitutes thought. We ought not, however, to be surprised at this, when we reflect, that the most careful examination of a nerve does not convey to us the slightest notion how an impression is received by it from an external body ; and how such impression is conveyed to the brain. All that we witness in these » Physiol, applique'e a la Pathologie, ch. vii.; or Drs. Bell and La Roche's trans- lation, Philad., 1832. 286 MENTAL FACULTIES. cases is the result; and we are thus compelled to study the intel- lectual and moral acts by themselves, without considering the cerebral movements concerned in their production. Such study is the basis of a particular science—metaphysics, ideology, ox phi- losophy. Apart from organization, this subject does not belong to physiology; but as some of the points of classification, &c, are concerned in questions that will fall under consideration, it may be well to give a short sketch ofthe chief objects of metaphysical in- quiry ; which are, indeed, intimately connected in many of their bearings, — as commonly treated of by the metaphysician, — with our subject. Broussais has considered, that metaphysics and phy- siology should be kept distinct; and that all the investigations of the metaphysician should be confined to the ideal. " I wish me- taphysicians, since they so style themselves," he remarks, some- what splenetically, " would never treat of physiology ; that they would only occupy themselves with ideas as ideas, and not as modifications of our organs; that they would never speak either of the brain, the nerves, the temperaments, or of the influence of climates, of localities, or of regimen; that they would never in- quire whether there are innate ideas, or whether they come through the medium of the senses ; that they would not undertake to follow their developments according to age or state of health ; for I am convinced that they cannot reason justly on these points. Such questions belong to physiologists, who can unite a knowledge of the moral nature with that of the structure of the human body." " It is possible," he adds, " that particular circumstances may oblige them to introduce physiological considerations into their calculations ; as when it is necessary to estimate the influence of certain laws or customs in relation to temperature, to the nature ofthe soil, the prevailing diseases, &c, but then they should avail themselves of the experience of physiologists and physicians."3 A more appropriate recommendation would have been, that the metaphysician should make a point of becoming acquainted with physiological facts and reasoning ; and, conversely, that meta- physics should form a part of the study of every physiologist. The cerebral manifestations comprise two very different kinds of acts; — the intellectual and the moral; the former being the source of all the knowledge we possess regarding ourselves and the bodies surrounding us ; the latter comprising our internal feel- ings, appetites, desires, and affections, by which we are incited to establish a relation with the beings around us : — the two sets of acts respectively embracing the qualities of the mind and of the heart.h If we attend to the different modes in which the intellectual ma- nifestations are evinced in our own persons, we shall find that there a De l'lrritation et de la Folie, Paris, 1828 ; or Dr. Cooper's translation, Columbia, S. C. 1831. b Adelon, Facultes de l'Esprit et de l'Ame.in Diet, de Me"d. viii. 469, Paris, 1823 ; and Physiologie de l'Homme, edit. cit. i. 527. FACULTIES THAT CONSTITUTE THE INTELLECT. 287 are several operalions, which differ essentially from each other. We are conscious of the difference between perceiving an impres- sion made upon one of the external senses, which constitutes per- ception, and the recalling of such impression to the mind, — which is the act of memory; as well as the distinction between feeling the relations, which connect one thing to another, constituting judgment; and the tendency to act in any direction, which we call will. The consciousness of these various mental acts has in- duced philosophers to admit the plurality of the intellectual acts, and to endeavour to reduce them all to certain primary faculties ; in other words, to faculties which are fundamental or elementary ; and which, by their combination, give rise to other and more com- plex manifestations. To this analytical method they have been led by the fact, that these different acts, which they have esteemed elementary, exhibit great variety in their degrees of activity; that one, for example, may be impressed with a character of great energy — as the memory — whilst another, as the judgment, may be singularly feeble,—and conversely. Broussais, indeed, con- ceives, that without the memory we cannot exercise a single act of judgment; since it is always necessary, in order to judge, that we should experience two successive perceptions; that is, that we should feel them alternately, which we could not do, unless pos- sessed of the faculty of renewing that, which we felt an instant before ; or, in other words, unless we possessed memory. Hence the loss of this faculty, he says, necessarily occasions that of judg- ment, and reduces man to a state of imbecility. To a certain ex- tent this is doubtless true. Total privation of memory must be attended with the results described; that is, if the individual re- tains no consciousness of that which has impressed him previously ; for it is obvious, that in such a case, there can be no comparison. A man, however, may have an unusual memory for certain things and not for others ; he may astonish us by the extreme accuracy of his recollection of numbers, places, or persons, and yet he may be singularly deficient in judging of ordinary matters;—his memory suggesting only one train of objects for comparison. In enumerating the faculties,which, by their union, constitute the intellect, we observe the greatest discrepancy amongst metaphysi- cians ; some admitting will, imagination, understanding, and sensi- bility ; others sensibility, imagination, memory, and reason ; others will, intelligence, and memory ; and others,again, imagination, re- flection, and memory. The views of Condillac3 on this subject have perhaps excited more attention than those of any other individual. Professing, as we have seen, that all our ideas are derived from suc- cessive operations of the senses and the mind, he admits the following constituent faculties ofthe intellect: —sensation, attention, compa- rison, judgment, reflection, imagination, and reason. Sensation he defines — the faculty ofthe mind, which affords the perception of any sensitive impression. Attention, the faculty of sensation,applied a Op. citat. 288 MENTAL FACULTIES. exclusively to a determinate object; being, as the word imports, the tension of the mind upon a particular object. Comparison, the faculty of sensation, applied to two objects atonce. Judgment, the faculty by which the mind perceives the connexions, that exist between the ob- jects compared. Reason, the faculty of running through a succession of judgments, which are connected with, and deduced from each other. Reflection, as the word indicates, the faculty by which the mind returns upon itself, upon its own products, to prove their cor- rectness, and to subject them again to its power; and imagination, to which Condillac attaches memory, — the faculty possessed by the mind of reproducing at will the different impressions, and all the products of its own operations. With regard, to the order of catenation of these different faculties, he considers sensation to be first put in play ; and if, amongst the perceptions, there is one, of which we have a more lively consciousness, and which attracts the mind to it alone, it is the product of attention ; then comes com- parison, which is nothing more than a double attention ; compa- rison is irresistibly succeeded by judgment; if, from one judg- ment, we pass to another deduced from it, we reason; if the mind turns back on its own products, we reflect ; and lastly, if the mind spontaneously awakens its different perceptions, imagination is in action. All these faculties are thus made to be deduced from each other; to originate in the first, or in sensation ; and all are this first sensation successively transformed. The doctrine of Condillac, abstractly considered, has already engaged attention. The division of the faculties, which, he con- ceives, by their aggregation, to form the intellect, is simple and in- genious, and appears to be more easily referable to physiological principles than that of other metaphysicians; accordingly, it has been embraced, with more or less modification, by certain physio- logical writers. The power of reflection, according to Broussais, is the charac- teristic of the human intellect; and to reflect is to feel. Man not only feels the stimulation produced by external organs, and by the movements of his own organs, which constitutes sensation ox per- ception, but he is conscious that he has felt these stimulations; or, in other words, he feels that he has felt; he has consequently a perception of his actual perception. This, he says, constitutes mental reflection. This process man can repeat as often as he thinks fit, and can observe all his sensations, and the different modes in which he felt', whilst occupied with his feelings. From this study he derives an idea of his own existence. " He distin- guished himself in the midst of creation, and paying regard only to his own existence, compared with all that is not himself, he pro- nounces the word I, (moi,) and says, lam; and viewing himself in action, says, I act, I do," &c. Perception of himself and of other bodies procures him what are denominated ideas. This is, therefore, another result of reflection; or, in other words, of the faculty he possesses of feeling himself feel. But man feels, besides, CLASSIFICATION OF THE AFFECTIVE FACULTIES. that he has already felt — this constitutes memory. In comparing two perceptions with each other, which are felt in succession, a third perception results, which is judgment. Consequently, to judge is only to feel. Hence, he concludes," sensation,reflection, andjudgment are absolutely synonymous,and present to the physi- ologist nothing more than the same phenomenon. The will, or that faculty by virtue of which man manifests his liberty by choosing, among different perceptions, the one he must obey — that faculty, which gives him the power of resisting, to a certain extent, the suggestions of instinct, is founded on reflection. Consequently, when we consider it in a physiological point of view, we can only discover in it the faculty of feeling ourselves, and of perceiving that we feel ourselves." Some ofthe later French metaphysicians have proposed certain modifications of the system of Condillac. M. De La Romiguiere,a for instance, denies that sensation is the original faculty, and he derives all from attention. The mind, he remarks, is passive during the reception of sensation, and does not commence action until directed to some object, or until it attends. According to him, the intellect consists of only three faculties—attention; comparison or double attention; and reason or double comparison. Judgment, imagination, and memory are not primary faculties: judgment is the irresistible product of comparison ; memory is but the trace, which every perception necessarily leaves behind it; and imagina- tion is but a dependence on reason. M. Destutt-Tracy,b again, reduces the number of primary faculties to four—perception, memory, judgment, and will ox desire. According to hitn, atten- tion is not an elementary faculty. It is but the active exercise of the intellectual faculties. The same applies to reflection and reason, which are only a judiciously combined employment of those facul- ties ; and to comparison and imagination, both of which enter into the judgment. This division is embraced by Magendie.0 Stewart'sd classification is into, 1, Intellectual powers, and, 2, Active and moral powers ; including, in the former, perception, attention, conception, abstraction, the associating principle, memory, imagi- nation, and reason. Browne reduces all the intellectual states to simple suggestion and relative suggestion, — comprising in the for- mer, conception, memory, and imagination, — in the latter, judg- ment, reason, abstraction, and taste. Abercrombief considers the mental operations to be chiefly referable to four heads, — memory, abstraction, imagination, and reason ox judgment ; whilst Kant has twenty-five primary faculties or forms ; pure conceptions or ideas a priori. These are a few only of the discrepant divisions of psychologists. » Legons de Philosophic, i. 4eme lecon. b Elemens d'Ideologie, 2de edit. Paris, 1804. c Precis Elementaire, i. 196. a Elements of the Philosophy of the Human Mind, 3d edit. Lond. 1808 ; and Amer. Edit, Brattleborough, Vt. 1813. e Lectures on the Philosophy ofthe Human Mind, Amer. Edit. Boston, 1826. f Inquiries concerning the Intellectual Powers, Amer. Edit. p. 91, New York, 1832. VOL. I. — 25 290 MENTAL FACULTIES. The list might have been extended by the classifications of Aris- totle, Bacon, Hobbes, Locke, Bonnet, Hume, Vauvenargues, Dide- rot, Reid, and others. Perhaps the most prevalent opinion at present is, that the original faculties are —perception, memory, judgment, and imagination. It is impossible for us, were it even our province, to reconcile these discrepancies. They are too con- siderable for us to hope, that this will ever be effected by meta- physical inquiry. We must, therefore, look to physiological inves- tigation, if not with well-founded — with the only — hopes, we can entertain, for the elucidation of the subject; and we shall find presently, that the minds of metaphysical physiologists have been turned in this direction, and that many interesting facts and specu- lations have been the result. A second topic of metaphysical inquiry regards the formation of the intellectual notions we possess. On this, there have been two principal opinions; some, as Plato, Descartes, the Kantists, Kanto- Platonists, &c, believing in the existence of innate ideasof things;— others, as Bacon, Locke, and Condillac, denying the existence of such innate ideas, and asserting that the human intellect, at birth, is a tabula rasa, and that the mind has to acquire and form all the ideas it possesses from impressions made on the senses. The truth includes probably both these propositions,— the action ofthe senses and of the intellectual faculties being alike necessary ; the former receiving the external and internal impressions, and transmitting them to the mind, which, through the cerebral organ, produces the different intellectual acts. Under the texms affective faculties, affections, and passions axe comprehended all those active and moral powers, which connect us with the beings that surround us, and are the incentives to our social and moral conduct. To this class belong — the feeling, which attaches the parent to the child ; that which draws the sexes toge- ther ; and the feeling of compassion, by which we are led to assist a suffering fellow-creature. They are, in truth, internal sensations, but of a higher cast than those of hunger and thirst; the latter being purely physical and announcing physical necessities ; the for- mer suggesting social and moral relations. Such affective faculties are the foundation of what are called moral wants; and, like the internal sensations in general, are the source of pleasure, when satisfied, — of pain, when resisted ; and it is only when they are extreme and opposed, that they acquire the name of passions.* The analysis of these is attended with the same difficulties as that of the intellectual faculties. Their plurality is universally admitted, but still greater discrepancy exists as to their precise number and connexion.11 Many moralists have united the moral faculties under the head of will or desires. Condillac6 is one of those. Every sensation, he observes, has the character of pleasure or pain, none being indifferent; as soon, therefore, as a sensation is experienced, a From potior, I suffer. b Adelon, art. Affection, in Dictionnaire de Medecine, lere edit.; and Physio/og-ie de l'Homme, edit. cit. i. 537. * Op. citat. MENTAL SPHERE HOW REGULATED. 291 the mind is excited to act. This tendency is at first but slightly marked, and is only an uneasiness {malaise): but it soon increases, becomes restlessness or inquietude ; in other words, a difficulty exP?nenced DY the mind of remaining in the same situation. This gradually becomes desire, torment, passion, and finally will, ex- cited to the execution of some act. Some have endeavoured, by ultimate analysis, to derive all the affective faculties of the mind tr°m one principal faculty — that of self-love,—the inward feeling, which induces all men to attend to themselves, their own preser- vation, and welfare. All the faculties, they assert, are returns of this self-love upon itself; and, as in the case of the intellectual faculties, attempts have been made to classify them ; but no two scarcely agree. Some have divided them into the agreeable and the distressing; others into those of love and hatred; many— regarding their effects upon society — into the virtuous, vicious, and mixed ; — the first comprising those that are useful to society, — as filial, parental and conjugal love, which form the foundation of families; goodness, pity, and generosity, which, by inducing men to assist each other, facilitate the social condition; and the love of labour, honour, and justice, which have the same result, by con- stituting so many social guarantees. The vicious passions, on the contrary, are such as injure man individually, and society in gene- ral, as pride, anger, hatred, and malice. Lastly, the mixed pas- sions are such as are useful or injurious, according to their use or abuse ; such as ambition, which may be a laudable emulation, or an insatiable passion, according to its extent and direction. Again, the passions have been divided into the animal or such as belong to physical man, and the social or such as appertain to man in society. The first are guides to him for his own preservation as well as for that ofthe species. To them belong fear, anger, sad- ness, hatred, excessive hunger, the venereal desires when vehe- ment, jealousy, &c. In the second are included all the social wants, when inordinately experienced. These vary according to the state of civilization of the individual and the community. Ambition, for instance, it is said, may be regarded, when inordinate, as ex- cessive love of power: — avarice, as an exaggeration of the desire for fortune: — hatred, and vengeance, as the natural and impetuous desire of injuring those that injure us, &c. Stewart's3 division of the active and moral powers embraces, 1. Instinc- tive principles, and 2. Rational principles: the former including appetites, desires, and affections, the latter self love and the moral faculty; all of which Brownb comprises under emotions, imme- diate, retrospective, or prospective ; — and lastly, Abercrombiec refers all the principles, which constitute the moral feelings, to the following heads: 1. The desires, the affections, and self-love; 2. The will; 3. The moral principle, and 4. The moral relation of man towards the Deity. It is obvious that the analysis of the moral faculties has been » Op. citat. . b Op- citat. <= Philosophy ofthe Moral Feelings, Amer. Edit. p. 35, New York, 1833. 292 MENTAL FACULTIES. still less satisfactorily executed than that of the intellectual; and that little or no attempt has been made to specify those that are primary or fundamental, from those that are more complex. The remarks, consequently, which were made regarding the only quarter we have to look to, for any improvement in our knowledge of the intellectual acts, apply a fortiori to the moral; although it must be admitted, that the difficulties attendant upon the investi- gation of the latter are so great as to appear to be almost, if not wholly, insuperable. As the brain, then, is admitted to be the organ of the intellectual and moral faculties, its structure probably varies according to the number and character of those ; and if there be primary or funda- mental faculties, each may be conceived to have a special organ concerned in its production, as each of the external senses has an organ concerned in its production. According to this view, the cerebral organization of animals ought to differ according to they psychology : where one is simple the other should be so likewise. This seems, so far as we can observe, to be essentially the fact. " In the series of animals," says Adelon,3 " we observe the brain more complicated as the mental sphere is more exten- sive ; and in this double respect a scale of gradation may be formed from the lowest animals up to man. If he have the most extensive moral sphere, if he alone possess elevated notions of religion and morality, he has also the largest brain, and one composed of more parts; so that if the physiology of the brain were more advanced, we might be able, by comparing the brains of animals with his, to detect the material condition, which constitutes humanity. If the brain were not constructed, a priori, for a cer- tain psychology, as the digestive apparatus is for a certain alimen- tation, if the mental and moral faculties were not as much innate as the other faculties, there would be nothing absolute in legislation or morals. The brain and its faculties are, however, in each ani- mal species, in a ratio with the role, which such species is called upon to fulfil in the universe. If man be, in this respect, in the first rank ; if he convert into the delicate affections of father, son, husband, and country, those brute instincts, by which the animal is attached to its young, its female, or its kennel; if, in short, he possess faculties which animals do not, — religious and moral feelings, with all those that constitute humanity, — it is owing to his having a more elevated vocation; to his being not only the king of the universe, but destined also for a future existence, and specially intended to live in society. Hence it was necessary, that he should not only have an intellect sufficiently extensive to make all nature more or less subject to him, but also a psychology such, that he might establish social relations with his fellows. It was necessary, that he should have notions of the just and the unjust, and be able to elevate himself to the knowledge of God; — to those sublime feelings, which cause him so to regulate his conduct » Art. Enceph. in Diet de Me"d. vii. 526; and Physiologie de l'Homme, edit. cit. i. 542. SIZE OF THE BRAIN. 293 as to maintain with facility his mortal connexions, and to deserve the future life to which he is called." But if the intellectual sphere be regulated by the cerebral deve- lopment, can we not, it has been asked, estimate the connexion between them ? And if there be different primary cerebral facul- ties, each of which must have an organ concerned in its produc- tion, can we not point out such organ in the brain ? Several in- vestigations of this character have been attempted, with more or less success : generally, however, they have added but little to our positive knowledge, and this, principally, from the intricacy of the subject. Until of late years, attention was chiefly paid to the mass and size of the encephalon: and it was, at one time, asserted, that the larger this organ, in any species or individual, the greater the intellect. Man, however, has not absolutely the largest ence- phalon although he is unquestionably the most intelligent of beings. The weight of the encephalon of a child six years of age is given by Haller at two pounds three ounces and a'half; whilst that of the adult is estimated by Sommering at from two pounds three ounces, to three pounds three ounces and three quarters ;a by Tiedernannb at from three pounds three ounces, to four pounds eleven ounces troy—the brain of the female weighing, on an average, from four to eight ounces less than that of the male. The average weight, after the meninges have been stripped off, is, in the healthy adult male, according to Lelutc about 1346 grammes, or three pounds and a half avoirdupois; of which the cerebrum weighs 1170, the cerebellum 176 grammes. In the female, the weight of the encephalon he found to be about Tyh less than in the male. The encephalon of the elephant, according to Haller, weighs from seven to ten pounds. This, consequently, overthrows the proposition ; and besides, in certain insects with very minute brains, the bee and the ant, we meet with evidences of singular in- telligence. The proposition was therefore modified, and it was laid down, that the larger the encephalon, compared with the rest of the body, the greater the mental sphere. When the subject was first investigated in this way, the result, in the case of the more common and domestic animals, was considered so satisfactory, that, without farther comparison, the proposition was considered to be established. More modern researches have shown, that it admits of numerous exceptions, and that several ofthe mammalia, and many diminutive and insignificant animals have the advan- tage over man in this respect. It has, indeed, been properly observed by Mr. Lawrence,41 that it cannot be a very satis- factory mode of proceeding to compare the body, of which the i Weber's Hildebrandt's Handbuch der Anatomie, Band iii. 423; Rudolphi, Grun- driss, u. s. w. ii. 11. t> Proceedings of the Royal Society for 1836; also, Das Him des Negers, mit des Europaers und Orang-outangs vergleichen, Heidelb. 1837, cited in Brit, and For. Med. Rev., for Oct. 1839, p. 374. c Gazette Medicale ; and Medico-Chirurgical Review for Oct. 1837, p. 507. a Lectures on Physiology, Zoology, &c, p. 191, Lond. 1819. 25* 294 MENTAL FACULTIES. 4T 2 2 TT4 t0 76 T4oto 5¥0 _I_ 228 1 1T2 1 7S 1 4'T J_ £72 1 ■5TI to 1 Too 1 _ 2 90 1 •9-4 I 1 93 weight varies so considerably, according to illness, emaciation, or embonpoint, with the brain, which is affected by none of these circumstances, and appears to remain constantly the same. This is the cause, why, in the cat, the weight of the encephalon, com- pared with that of the body, has been stated as 1 to 156 by one comparative anatomist, and as 1 to 82 by another; that of the dog as 1 to 305 by one, and as 1 to 47 by another, &c. The following table, taken chiefly from Haller3 and Cuvier,b ex- hibits the proportion which the encephalon bears to the rest ofthe body, in man and certain animals. Child, 6 years old ... . ^ Elephant . . Adult........^T Stag .... Gibbon........4V Roebuck (young) Sapajous, from Apes..... Baboons . . . Lemurs ...... "TlT to -g\ Bat (vespertilio).....9^ Mole........-j'e Bear.........?|T Hedgehog.......ffa Fox.........,£T Wolf.........^0 Beaver .... Hare..... Rabbit .... Rat..... Mouse .... Wild Boar . . . Domestic do. . . Sheep Ox.......TT„ to ¥£o Calf.........2Tf Horse Ass . yihrl0 Dolphin Eagle .....• T?4 -1 1 ! -I- • • • 27' ST'ffS' iT>2 1_ ......2^o Goose........X60 Cock........3r7 Canary Bird......T\ Humming bird.....TVa Turtle...... Tortoise . . . ... Frog...... Shark...... Pike...... Carp...... __1 TTffT 1 2 2To" 1 T72 __] 2 4"9iT 1 lTo? In 9 males, between 27 and 50 years of age, who died immedi- ately, or within a few hours after accidents and other external causes of death, and who had been previously in good health, Dr. John Reidd obtained the following results;— the weight used being avoirdupois: — Average weight of body (9 weighed) 134 lbs. 3£ oz. Average of en- cephalon (6 weighed) 3 lbs. 4 oz. 4 jdr Average of cere- bellum (4 weighed) 5 oz. 7i dr. with pons and medulla heart (9 (5 weighed) weighed) 6 oz. 6 dr., 12 oz. 6 dr. or, taking the average of the four cases only in which the cerebel- lum was taken, 6 oz. 7] dr. Relative weight of body to encephalon, (6 weighed).....as 1 to 40f ---------------------to heart, (9 weighed).......as 1 to 173^ --------------of encephalon to cerebellum, (4 weighed) - - - as 1 to 9| --------------^— to cerebellum with pons and ? l t R 6 medulla, (5 weighed) £ " T9 * Element. Physiol, x. sect. 1. b Logons d'Anat. Comp. ix. art. 5. c On the authority of ex-President Madison. ' Lond. and Edinb. Monthly Journal of Mel Science, April, 1843, p. 322. Average of cerebellum'Average of SIZE OF THE BRAIN. 295 It has been the general belief, that the brain of the negro is infe- rior to that of the white variety of the species; but some obser- vations of M. Tiedemann led him to the belief, that there is no per- ceptible difference either in the average weight or average size of the brain in the two varieties, and that the nerves compared with the size of the brain are not larger in the former than in the latter. In the external form of the brain of the negro a very slight differ- ence only could be traced by him ; but, he affirmed, that there is absolutely no difference in its external structure, nor does the negro brain exhibit any greater resemblance to that of the ourang-outang than the brain of the European, excepting, perhaps, in the more symmetrical disposition of its convolutions. Tiedemann's obser- vations were made, however, upon very few subjects ; and his own facts do not bear out all his deductions. He admits, that the ante- rior part ofthe hemisphere was something narrower than is usually the case in Europeans, " which," says Dr. Combe,3 " as the ante- rior portion is the seat of intellect, is really equivalent to conceding that the negro is naturally inferior in intellectual capacity to the European !" M. Tiedemann established the fact, that the average capacity of the Ethiopian skull is somewhat less than that of the European, and that a large size is considerably less common among them than among any other races of mankind.b Wrisberg and Sommering0 proposed another point of compari- son — the ratio of the mass of the encephalon to that of the rest of the nervous system ; and they asserted, that, in proportion as any animal possesses a larger share of the former; or, in other words, in proportion as the percipient and intellectual organ exceeds the other or the organ ofthe external senses — the mental sphere may be expected to be more diversified and developed. But although man is, in general, pre-eminent in this respect, he is not absolutely so. It would be still more important to know the ratio, that the cerebrum or brain proper bears to the cerebellum and medulla oblongata. The first is essentially the organ of intellect; and the most striking character of the human brain is the large develop- ment ofthe cerebral hemispheres, of which we have no parallel in the animal kingdom. The last is the encephalic part in which all the nerves of the senses arise or terminate. The assertion, that man has the largest cerebrum in proportion to the cerebellum, is not accurate. The Wenzelsd found the ratio, in man, to be as 6TS2V or 8*gT to 1; in the horse, 4\ to 1; in the cow, 5^ to 1; in the dog,~6/_ to 1 ; in the cat, 4T4? to 1 ; in the mole, 3f to 1; and in the mouse, 6| to 1. Nor is it true that man has the largest cerebrum in proportion to the medulla oblongata and medulla spinalis; although to this position there are perhaps fewer objections than to any of the others. None of them, it is obvious, are distinctive between man and animals, or assist us in a Phrenological Journal, No. liv. Dec, 1837. b Brit, and For. Med. Rev. for Oct. 1839, p. 379. <= Corpor. Human. Fabric, iv. § 92; and Blumenbach's Comp. Anat. by Lawrence, p. 292. Lond. 1807. i De Penitiori Structur. Cerebr. Hominis et Brutorum, tab. iv. 296 MENTAL FACULTIES. solving the great problem of the source and seat of the numerous psychological differences we observe in different animals and men. Various plans have been devised for appreciating the compara- tive size of the cranium — which is generally in a ratio with that of the brain, — and of the bones of the face. As the former contains the organ of the intellect, and the latter those of the external senses and of mastication, it has been presumed, that the excess of the former would indicate the predominance of thought over sense ; and, conversely, that the greater development of the face would place the animal lower in the scale. One of these methods, which was first proposed by Camper,a is by taking the course of the facial line, and the amount of the facial angle. The facial line is a line drawn from the projecting part of the forehead to the alveoli of the incisor teeth of the upper jaw; and the facial angle is that formed between this line and another drawn horizontally backwards from the upper jaw. The course of the horizontal line and its point of union with the facial line are not uniform in all the figures given by Camper: some- times it is made to pass through the meatus auditorius externus, but it often falls far below it; yet Dr. Bostock thinksb" we cannot hesitate to admit the correctness of Camper's observations, and we can scarcely refuse our assent to the conclusion that he deduces from them." In man, whose face is situate per- pendicularly under the cra- nium, the facial angle is very large. In animals the face is placed in front of the cranium ; and, as we descend from man the angle becomes less and less, until it is finally lost; the cranium and face being, in most rep- tiles and fish,completely on a level. The marginal figure exhibits the difference be- tween the facial angle of those of European descent, and that of the negro. By covering with the finger the parts below the nose alternately, we have the countenance of the white or of the negro, in which the facial angle differs as much as 10°, or 15°. Fig. 57 exhibits the facial line and angle of the ourang- a Dissertation Physique de M. Camper, sur les Differences Reelles que Presentent les Traites du Visage, &c, traduit du Holiandois, par D. B. Q. Disjonval, Autrecht, 1791 ; and Gall, sur les Fonctions, &c, ii. 301. b Physiology, 3d edit. p. 804, Lond. 1836. Facial Line and Angle of Man. CAMPER'S FACIAL LINE AND ANGLE 297 Fig. 57. outang. Those animals that have the snout long, and the facial angle consequently small, have been proverbially esteemed foolish,3 — such as the snipe, stork, crane, &c,; whilst superior intelligence is ascribed to those in which the angle is more largely developed — as the elephant and the owl; although in them, the large facial angle is caused by the size ofthe fron- tal sinuses, or by the wide separation between the two tables of the skull, and is necessarily no index of the size of the brain. Yet, from this cause, per- haps, the owl was chosen asan emblem of the goddess of wisdom ; and the elephant has received a name in the Malay language, indicating an opinion, that he is possessed of reason. The following table exhibits the facial angle in man and certain animals, taken by a line drawn parallel to the floor of the nostrils, and meeting another, drawn from the greatest prominence of the alveoli of the upper jaw to the prominence of the forehead : Facial Line and Angle of the Ourang- Outang. Man .... 65° to 85° and more. Sapajou.........65° Ourang-outang.....56° or 58° Guenon.........57° Mandril.......30° to 42° Coati..........28° Polecat.........31° Pug dog.........35° Mastiff.........41° Hare..........30° Ram..........30° Horse.........23° The facial angle may, then, exhibit the difference between man and animals ; and, to a certain extent, between the species or in- dividuals of the latter ; but, farther, it is of little or no use.b In man it may be considered to vary from 70° to 85° in the adult, but in children it reaches as high as 90°; — a sufficient proof that it cannot be regarded as a measure of the intellect. In the European, it is, on the average perhaps, 80°, in the Mongol, 75°, and in the negro, 70°, not many degrees above the ourang-outang.0 It is found, however, that the skulls of different nations, and of indivi- duals of the same nation, may agree in the facial angle, whilst there may be striking distinctions in the shape ofthe cranium and face, in the air and character of the whole head, as well as in the particular features, — the inclination of the facial line being ob- viously more dependent on the prominence of the upper jaw and frontal sinuses than on the general form of the head. The ancients were impressed with the intellectual air exhibited by the open facial angle ; for we find in all their statues of legislators, sages, a Lawrence, op. citat. p. 168. b Dr. Morton, in his splendid work, Crania Americana, Philad. 1839, describes a " Facial Goniometer," originally suggested by Dr. Turnpenny, of Philadelphia, which is admirably adapted for measuring the facial angle. c Prichard's Physical History of Mankind, i. 288, 3d edit. Lond. 1836. 298 • MENTAL FACULTIES. and poets, an angle of at least 90°, and in those of heroes and of superhuman natures it is carried as high as 100°. This angle, ac- cording to Camper, never existed in nature ; and yet he conceives it to be the beau ideal of the human countenance, and to have been the ancient model of beauty. It was, more probably, the model of superior intellectual endowment, although ideas of beauty might have been connected with it. Every nation forms its no- tions of beauty, derived from this source, chiefly from the facial angle to which it is accustomed. With the Greeks it was large, and therefore the vertical facial line was highly estimated. For the same reason, it is pleasing to us ; but such would not be the universal impression. Savage tribes on our own continent, have preferred the pyramidal shape of the head, and made use of every endeavour, by unnatural compression in early infancy, to produce it; whilst others, not satisfied with the natural shape of the frontal bone, have forced back the forehead, either by applying a flat piece of board to it, like the Indians of our own continent, or by iron plates, like the inhabitants of Arracan. By this practice, the Caraibs are said to be able to see over their heads. Daubenton,a again, endeavoured, by taking the occipital line and angle, to measure the differences between the skulls of man and animals. One line is drawn from the posterior margin of the foramen magnum of the occipital bone to the inferior margin of the orbit, and the other from the top of the head to the space between the occipital condyles. In man, these condyles, as well as the foramen magnum, are so situate, that a line drawn perpendicular to them would be a continuation of the spine ; but in animals they are placed more or less obliquely; the perpendicular would neces- sarily be thrown farther forward, and the angle be thus rendered much more acute.b Blumenbach says, that Daubenton's method may be adapted to measure the degrees of comparison betwixt man and brutes, but not the varieties of national character ; for he found it different in the skulls of two Turks, and of three Ethiopians. The methods of both Camper and Daubenton he discovered to be insufficient to indicate the varieties in the national and individual character. He accordingly, describes a new method,— which he calls the norma verticalis.0 It consists in selecting two bones, the frontal from those of the cranium, and the superior maxillary from those of the face, and comparing these with each other, — by re- garding them vertically, — placing the great convexity of the cra- nium directly before him, and marking the relative projections of the maxillary bone beyond the arch of the forehead. The Geor- a Memoires de l'Academie des Sciences de Paris, 568, Paris, 1764. b By some writers, Daubenton's method is said to consist of " a line drawn from the posterior margin of the occipital foramen to the inferior margin of the orbit; and another drawn horizontally through the condyles of the occipital bone." It is obvious, that little or no comparative judgment of the cranium and face could be formed from this. Decad. Collectionis suae Craniorum diversarum Gentium; and De Gener.Human. Var. Nativ., edit. 3a, Gotting. 1795. COMPARATIVE SIZE OF THE CRANIUM AND FACE. 299 gian is thus found to be characterized by the great expanse of the Uv?P(£ t • °Uter part of the cranium» which hides the face. In the Ethiopian, the narrow, slanting forehead allows the face to appear, whilst the cheeks and jaws are compressed laterally and elongated in front; and in the Tungoose, the maxillary, malar, and nasal bones are widely expanded on each side; and the two last rise to the same horizontal level with the space between the frontal sinuses — the glabella. Blumenbach's method, however, only affords us the comparative dimensions of the two bones in one direction. It does not indicate the depth of the maxillary bone or of the os frontis, or their comparative areas. The view thus obtained is therefore partial. Finding the inapplicability of other methods to the greater part of the animal creation, — to birds, reptiles, and fishes, for example, — Cuviera suggested a comparison between the areas of the face and cranium under the vertical section of the head. The result of his observations is, — that, in the European, the area of the cra- nium is four times that of the face, — excluding the lower jaw. In the Calmuck, the area of the face is one-tenth greater than in the European; in the negro, one-fifth, and in the sapajou, one-half. In the mandril, the two areas are equal; and, in proportion as we descend in the scale of animals, the area of the face gains over that of the cranium ; in the hare, it is one-third greater; in the ruminant animals double; in the horse, quadruple, &c.; so that the intelli- gence of the animal is said to be greater or less, as the preponder- ance of the area of the face over that of the skull diminishes or increases. The truth, according to Sir Charles Bell,b is, that the great dif- ference between the bones of the cranium and face in the European and negro is in the size of the jaw bones. In the negro, these were found to bear a much greater proportion to the head and to the other bones of the face than those of the European skull; and the apparent size of the bones of the negro face was discovered to proceed solely from the size and shape ofthe jaw bones, whilst the upper bones of the face, and, indeed, all that had no relation to the teeth and to mastication, were lessthan those of the European skull. Other methods, of a similar kind, have been proposed by natu- ralists, as by Spigel,c Herder,d Mulder,e Walther/ Doornik,£ Spix,h a Legons d'Anatomie Compar., No. viii. art. i. torn. ii. p. 1. b Anatomy of Expression, 2d edit., Lond. 1824. c Linese Cephalometricae Spigelii, in Spigel. de Human. Corpor. Fabric, i. 8. d JVackenlinien (Lines nuchales Herderi) in Herder's Ideen zur Philosophic der Geschichte der Menschheit, Th. iii. s. 186, Tubing. 1806. e Vorderhauptwinkel (Angulus sincipitalis Mulderi,) in Art. Kopflinien, in Pierer's Anat. Physiol. Real Worterb. iv. 524, Leipz. 1821. f Schadelwinkel (Angulus Cranioscopicus Waltheri,) in Walther's Kritische Dar- stellung der Gallschen Anat. Physiol. Untersuch. des Gehirnund Schadelbaues, s. 108, Zurich, 1802. e Wijsgeerig Natuurkundig Onderzoek aangande den Oorsprongliken Mensch en de Oorspronglike Stammen van deszelfs Geslacht, Amsterd. 1808. b Cephalogenesis, Monach. 1815. 300 MENTAL FACULTIES. and Oken,a but they are all insufficient to enable us to arrive at an accurate comparison. Blumenbach asserts, that he found the facial and occipital angles nearly alike in three-fourths of known animals. Moreover, it by no means follows, that, in the same species, there should be a correspondence between the size of the cranium and face. In the European, the face may be unusually large; and yet the mental endowments may be brilliant. Leo X. and Montaigne and Leibnitz, Racine, Haller, Mirabeau and Franklin, had all large features.b All the methods, again, are confined to the estimation ofthe size ofthe whole encephalon ; whereas we have seen, that the brain alone is concerned in the intellectual and moral manifestations ; although Gall includes, also,the cerebellum. It has already been remarked, that no animal equals man in the develop- ment of the cerebral hemispheres. In the ape, they are less pro- minent ; and below it in the scale of creation, they become less and less ; the middle lobes are less arched downwards ; and the poste- rior lobes are ultimately wanting, leaving the cerebellum uncover- ed ; the convolutions are less and less numerous and deep, and the brain at length is found entirely smooth. The experiments of Rolando of Turin, and of Flourense of Paris, are likewise confirm- atory of this function of the brain proper. These gentlemen ex- perimented upon different portions of the encephalon, with the view of detecting their functions ; endeavouring, as much as pos- sible, not to implicate any part except the one which was the sub- ject of investigation ; and they found, that if the cerebral hemi- spheres were alone removed, the animal was thrown into a state of stupor or lethargy; was insensible to all impressions; was to every appearance asleep, and evidently devoid of all intellectual and affective faculties. On the other hand, when other parts of the encephalon were mutilated, — the cerebellum, for example — leaving the cerebral hemispheres uninjured, the animal was deprived of some other faculties, — that of moving, for instance — but retained its consciousness, and the exercise of all its senses. M. Desmoulins,d in his observations on the nervous system of vertebrated animals, is in favour of a view, originally suggested by M. Magendie,e that the intellectual sphere of man and animals depends exclusively on the cerebral convolutions; and that exami- nation of the convolutions will point out the intellectual differences, not only between different species, but between individuals of the same species. According to him, the cerebral convolutions are numerous in animals in proportion to their intelligence ; and, in animals of similar habitudes, have a similar arrangement. In the same species, they differ sensibly, according to the degree in which the individuals possess the qualities of their nature; — for example, a Lehrbuch der Zoologie, Abth. ii. s. 660. A description of all these methods is given by Choulant, in Pierer, loc. cit. b Gall, Sur les Fonctions du Cerveau, ii. 296. c Recherches Experimentales sur le Systeme Nerveux, 2de edit. Paris, 1842. d Anatomie des Systemes Nerveux des Animaux a Vertebres, Paris, 1325. e Precis Elementaire, edit cit. i. 185. VIEWS OF DESMOULINS AND GALL. 301 they vary in the foetus and in the adult; are manifestly less numer- ous and smaller in the idiot, and become effaced in protracted cases of insanity. He farther remarks, that the morbid conditions of the encephalon, which occasion mental aberration, are especially such as act upon the convolutions; and that, whilst apoplectic ex- travasation into the centre ofthe organ induces paralysis of sensa- tion and motion, the least inflammation of the arachnoid membrane causes delirium. Hence, he deduces the general principle, that the number and perfection of the intellectual faculties are in proportion to the extent of the cerebral surfaces. This view of M. Desmoulins, so far as regards the seat of the intellectual and moral faculties, accords with one to which attention must now be directed, and which has given rise to more philoso- phical inquiry, laborious investigation, and, it must be admitted, to more idle enthusiasm and intolerant opposition, than any of the psychological doctrines advanced in modern times : — we allude to the views of Dr. Gall.a These are, 1st, That the intellectual and moral faculties are innate. 2dly, That their exercise or mani- festation is dependent upon organization. 3dly, That the brain is the organ of all the appetites, feelings and faculties ; and, 4thly, That the brain is composed of as many particular organs as there are appetites, feelings, and faculties, differing essentially from each other. The importance of Gall's propositions ; the strictly physio- logical direction which they have taken, — the only one, as we have said, which appears likely to aid us in our farther acquaint- ance with the psychology of man, — require that the physiological student should have them placed before him as they emanated from the author. The work of Gall, however, on the functions of the brain, comprises six octavo volumes, not distinguished for un- usual method or clearness of exposition. Fortunately, the distin- guished physiologist, Adelon, to whom we have so frequently referred, has spared us the necessity of a tedious and difficult analysis, by the excellent and impartial view which he has given in the Dictionnaire de Medecine,b which has been since trans- ferred to his Physiologie del'Homme; both being abridgments of the Analyse d'un Cours du Dr. Gall, published by him in 1S0S. The foundation of this doctrine is, that the brain is not a single organ, but is composed of as many nervous systems as there are primary and original faculties of the mind. In the view of Gall, the brain is a group of several organs, each of which is concerned in the production of a special moral act: and, according as the brain of an animal contains a greater or less number of these organs, and of a greater or less degree of development, the animal has, in its moral sphere, a greater or less number of, or more or less active, faculties. In like manner, as there are as many sensorial nervous systems and organs of sense as there are external senses, so there a Sur les Fonctionsdu Cerveau, Paris, 1825. b Art. Encephale (Physiologie), Paris, 1823, and art. Facultes de l'Esprit etde l'Ame, &c, in Diet, de Me"decine, viii. 469, Paris, 1823. VOL. I. — 26 302 MENTAL FACULTIES. are, it is maintained, as many cerebral nervous systems as there are special moral faculties or internal senses. Each moral faculty has, in the brain, a nervous part, concerned in its production, as each sense has its special nervous system; the sole difference being, that the nervous systems ofthe senses are separate and distinct, whilst those ofthe brain are crowded together in the small cavity of the cranium, and appear to form but one mass. The proofs adduced by Galla in favour of his proposition, are the following : — 1st. It has been established as a principle, that the differences in the psychology of man and animals correspond to varieties in the structure of the encephalon, and that the latter are dependent on the former. Now, the differences of the brain con- sist less in changes of the general form of the organ than in parts, which are present in some and not in others ; and if the presence or absence of such parts is the cause why certain animals have a greater or less number of faculties than others, they ought cer- tainly to be esteemed the special organs of such faculties. 2dly. The intellectual and moral faculties are multiple. This every one admits. Each, consequently, ought to have its special organ; and the admission of a plurality of intellectual and moral faculties must induce that of a plurality of cerebral organs, in the same manner as each external sense has its proper nervous system. 3dly. In different individuals of the same species, — in different men, — much psychological variety is observable. The cause of this is doubtless in the brain ; but we can hardly ascribe it to a difference in the general shape of the organ, the form of which is sensibly the same. It is owing rather to differences in the separate parts ofthe brain. Are not such parts, therefore, he asks, distinct nervous systems? 4thly. In the same individual — in the same man —the intellectual and affective faculties have never the same degree of activity ; whilst one predominates, another may be feeble. Now, this fact, which is inexplicable under the hypothesis, that the brain is a single organ, is readily intelligible under the theory ofthe plurality of organs. Whilst the cerebral part, which is the agent of the one faculty, is proportionably more voluminous or more active, that which presides over the other is less so. Why, he asks, may not this happen with the cerebral organs, as with the other organs of the body — the senses, for example ? Cannot one of these be feeble and the other energetic? 5thly. In the same individual, all the faculties do not appear, nor are they all lost at the same periods, Each age has its own psychology. How can we, then, explain these intellectual and moral varieties according to age, under the hypothesis, that the brain is a single organ ? Under the doctrine of the plurality of cerebral organs, the expla- nation is simple. Each cerebral system has its special period of development and decay. 6thly. It is a common observation, that when we are fatigued by one kind of mental occupation, we have recourse to another; yet it often happens, that the new labour, * Op. cit. ii. 394. VIEWS OF GALL. 303 instead of adding to the fatigue experienced by the former, is a relaxation. This, Gall remarks, would not be the case, if the brain were a single organ and acted as such, but it is readily expli- cable under the doctrine of plurality of organs. It is owing to a fresh cerebral organ having been put in action. 7thly. Insanity is frequently confined to one single train of ideas, as in the variety, called monomania, which is often caused by the constancy and tenacity of an original exclusive idea. This is frequently removed by exciting another idea opposed to the first, and which distracts the attention from it. Is it possible, Gall asks, to comprehend these facts under the hypothesis of the unity of the brain. Sthly. Idiocy and dementia are often only partial; and it is not easy to conceive, under the idea ofthe unity of the brain, how one facultv remains amidst the abolition of all the others. 9thly. A wound or a physical injury of the brain will frequently modify but one faculty, paralysing or augmenting it, and leaving every other uninjured. lOthly, and lastly. Gall invokes the analogy of other nervous parts ; and, as the great sympathetic, the medulla oblon- gata, and medulla spinalis are — in his view at least—groups of special nervous systems, it is probably, he says, the same with the brain. Such are the main arguments employed by Gall for proving, that the brain consists of a plurality of organs, each of which is concerned in the production of a special intellectual or moral faculty, and should they not carry conviction, it must be admitted, that many of them are ingenious and forcible, and all merit attention. It is a prevalent idea, that this notion of a plurality of organs is a phantasy, which originated with Gall. Nothing is more erroneous : he has adduced the opinions of numerous writers who preceded him, some of whom have given figures ofthe cranium, with the seat ofthe different organs and faculties marked upon it. To this list we might add numerous others. Aristotle, in whose works we find the germs of many discoveries and speculations, thought that the first or anterior ventricle of the brain was the ventricle of common sense ; because from it, according to him, the nerves of the five senses branched off. The second ventricle, connected by a minute opening with the first, he fixed upon as the seat of imagination, judgment, and reflection ; and the third ventricle, as a storehouse into which the conceptions of the mind, digested in the second ven- tricle, were transmitted for retention and accumulation ; in other words, he regarded it as the seat of memory. Bernard Gordon, in a work written in 1296, gives nearly the same account ofthe brain. It contains, he says, three cells or ventricles. In the anterior partof the first ventricle lies common sense; the function of which is to take cognizance ofthe various forms and images, received by the several senses. In the posterior partof the first ventricle he places phantasia ; and in the anterior part of the second, imaginativa: in the posterior part of the middle ventricle lies estimativa. It would be a waste of time and space, to adduce the absurd 304 MENTAL FACULTIES. Fig. 58. notions entertained by Gordon on this subject He thinks there are three faculties or virtues, — imaginatio, cogitalio, and memoria,— each of which has a special organ engaged in its production. For many centuries it was believed, that the cerebrum was the organ of perception, and the cerebellum that of memory. Albert the Great, in the thirteenthcentury,sketchedaheadon which he represented the seat of the differentintellectual faculties. In the forehead and first ventricle he placed common sense and imagination; in the second, intelligence and judg- ment; and in the third, memory and the motive force. The head in the margin (Fig. 58) is from an old sketch contained in the Book Rari- ties, of the University of Cambridge. Servetus conceived, that the two anterior cerebral cavities are for the reception of the images of external objects; the third is the seat of thought; the aqueduct of Sylvius, the seat of the soul, and the fourth ventricle that of memory. In 1491, Peter Montagnana published an engraving, in which were repre- sented the seat of the sensus communis, a cellula imaginativa, cellula estimativa seu cogitativa, a cellula memorativa, and a cellula rationalis. A head by Ludovico Dolci exhibits a similar arrange- ment. (Fig. 59.)a The celebrated Dr. Thomas Wil- lis, in 1681, asserted, that the cor- pora striata are the seat of percep- tion ; the medullary part ofthe brain that of memory and imagination ; the corpus callosum that of reflec- tion : and the cerebellum, according to him, furnished the vital spirits necessary for the involuntary mo- tions.11 It would appear, too, that Swedenborg, half a century before the promulgation of Gall's theory, maintained the doctrine, that every man is born with a disposition to all sorts of evil, which must be a See Burton's Anatomy of Melancholy, 11th edit. i. 32, Lond. 1813. Also, Mar. garita Philosophica, lib. ix. cap. 40, Basil. 1508, cited by Dr. John Redman Coxe, in Dunglison's American Medical Intelligencer, i. 58, Philad. 1838. b Gall, Sur les Fonctions du Cerveau, ii. 350, Paris, 1835. Old Phrenological Head. Fig. 59. Olfactus Cnistus Head by Dolci, AD. 15G2. PHRENOLOGY. 305 checked by education, and as far as possible rooted out; and that the degree of success or of failure in this respect would be indi- cated by the shape of the skull. " The peculiar distinctions of man," he argued, " will and the understanding, have their seats in the brain, which is excited by the fleeting desires of the will, and the ideas of the intellect. Near the various spots where these irritations produce their effects, this or that part of the brain is called into a greater or less degree of activity, and forms along with itself corresponding parts of the skull.""* This view, that exercise of the cerebral organs occasions their development in bulk, and want of due exercise their decrease, is now maintained by many phrenologists, but denied by others. The above examples are sufficient to show, that the attempt to assign faculties to different parts of the brain, and, consequently, the belief, that the brain consists of a plurality of organs, had been long indulged by anatomists and philosophers. The views of Gall are resuscitations of the old ; but resembling them little more than in idea. Those of the older philosophers were the merest phantasies, unsupported by the slightest observation : the specula- tions of the modern physiologist have certainly been the result of long and careful investigation, and of deep meditation. Whilst, therefore, we may justly discard the former, the latter are worthy of rigid and unprejudiced examination. Admitting, with Gall, the idea of the plurality of organs in the brain, the inquiry would next be,— how many special nervous systems are there in the human brain, and what are the primary- intellectual and moral faculties over which they preside ? This Gall has attempted. To attain this double object, he had two courses to adopt; either, first of all, to indicate anatomically the nervous systems that constitute the brain, and then to trace the faculties of which they are the agents; or, on the contrary, to point out first the primary faculties, and afterwards to assign to each an organ or particular seat in the brain. The first course was impracticable. The cerebral organs are not distinct, isolated in the brain : and if they were, simple inspection could not indicate the faculty over which they preside; any more than the appear- ance of a nerve of sense could indicate the kind of sensation for which it is destined. It was, only, therefore, by observing the faculties, that he could arrive at a specification of the cerebral organs. But here, again, a source of difficulty arose. How many primary intellectual and moral faculties are there in man ? and what are they ? The classifications of the mental philosophers, differing, as we have seen they do, so intrinsically and essentially from each other, could lead him to no conclusion. He first, how- ever, followed the notions on which they appeared to be in accord- ance ; and endeavoured to find particular organs for the faculties of memory, judgment, imagination, &c. But his researches in this direction were fruitless. He, therefore, took for his guidance 1 Dr. Sewall, Examination of Phrenology, 2d edit., p. 14, Boston, 1833. 26* 306 MENTAL FACULTIES. the common notions of mankind ; and having regard to the favour- ite occupations, and the different vocations of individuals, to those marked dispositions, which give occasion to the remark, that a man is born a poet, musician, or mathematician, he carefully examined the heads of such as presented these predominant qualities, and endeavoured to discover in them such parts of the brain as were more prominent than usual, and which might be considered as spe- cial nervous systems, — the organs of these faculties. After multi- tudinous empirical researches on living individuals, on a collection of crania, and on casts made for the purpose, attending particularly to the heads of such as had one of their faculties predominant, and who were, as he remarks, geniuses on one point, — to the maniac, and the monomaniac ; —after a sedulous study, likewise, of the heads of animals, comparing especially those, that have a particu- lar faculty, with such as have it not — in order to see if there did not exist in the brain of the former some part which was wanting in that of the latter ; by this entirely experimental method, he ven- tured to specify, in the brains of animals and man, a certain num- ber of organs ; and, in their psychology, as many faculties, truly primary in their character. But} in order that such a mode of investigation be applicable it must be admitted, 1st. That one of the elements ofthe activity of a function is the development of its organ. 2dly. That the cere- bral organs end, and are distinct, at the surface of the brain. 3dly. That the cranium is moulded to the brain, and is a faithful index of its shape ; for it is, of course, through the skull and the integu- ments covering it, that Gall attempts, in the living subject, to ap- preciate the state of the brain. Within certain limits, these posi- tions are true. In the first place, we judge of the activity of a function, by the size ofthe organ that executes it: the greater the olfactory nerve, the more acute we expect to find the sense of smell. In the second place, according to the anatomical theory of Gall, the cerebral convolutions are the final expansions of the cere- brum : if we trace back the original fasciculi, which, by their ex- pansions, form the hemispheres of the brain, they are observed to increase gradually in size in their progress towards the circumfer- ence of the organ, and to terminate in the convolutions. Lastly, to a certain extent the cranium is moulded to the brain; and par- ticipates in all the changes, which the latter undergoes, at different periods of life, and in disease. For example, during the first days after the formation of the brain in the foetus, the cranium is mem- branous, and has exactly the shape of that viscus. On this mem- brane, ossific points are deposited, so that, when the membrane has become bone, the cranium has still the shape of the brain. In short, nature having made the skull to contain the brain, has fitted the one to the other, and this so accurately, that its internal surface exhibits sinuosities, corresponding to the vessels that creep on the surface; and digitations, corresponding to the cerebral convolu- tions. The brain, in fact, rigidly regulates the ossification of the PHRENOLOGY. 307 cranium; and when, in the progress of life, the brain augments, the capacity of the cranium is augmented likewise; not by the effect of mechanical pressure, but owing to the two parts being catenated in their increase and nutrition. This remark applies not only to the skull and brain, regarded as a whole, but to their sepa- rate parts. Certain portions of the brain are not developed simul- taneously with the rest ofthe organ ; and the same thing happens to the portions of the skull that invest them. The forehead, for example, begins to be developed after the age of four months: but the inferior occipital fossae do not increase in proportion until the period of puberty. Again; when the brain fades and wastes in advanced life, the cavity of the cranium contracts, and its ossifica- tion takes place on a less and less outline. In advanced life, how- ever, according to Gall, the correspondence between the brain and the inner table of the skull is alone maintained; the outer table appearing to be a stranger to all nutritive movement, and preserv- ing its dimensions. Lastly, the cranium partakes of all the varia- tions experienced by the brain in disease. If the brain be wanting, as in the acephalous monster, the cranium is wanting also. If a •portion of the brain exist, the corresponding portion of the cra- nium exists. If the brain be smaller than natural, as in the idiot, the cranium is so likewise. If the brain, on the contrary, be dis- tended by hydrocephalus, the cranium has a considerable capacity : and this, not owing to a separation, at the sutures, of the bones composing it, but owing to ossification taking place on a larger outline. If the brain be much developed in any one part, and not in another, the cranium is protuberant in the former; restricted in the latter. Lastly, in cases of mania, the cranium is often affected ; seeming, for example, to be unusually thick, dense, and heavy. These reasons, adduced by Gall, may justify the admission, that, within certain limits, the skull is moulded to the brain ; and, if we admit this, the method followed by him of specifying the organs of the mental faculties may be conceived practicable. Such is the basis of the system of craniology, proposed by Gall. It also bears the name cranology, organology,phrenology, and cra- nioscopy : though, strictly speaking, it is by cranioscopy that we acquire a knowledge of craniology, or the art of prejudging the intellectual and moral aptitudes of man and animals, from an exa- mination of the cranium. It is, of course, limited in its application. Gall admits, that it is not available in old age —owing to the phy- siological fact before stated, — that the external table of the skull is no longer modified by the changes, that happen to the brain ; and he acknowledges, that its employment is always difficult, and liable to numerous errors. We cannot touch the cranium directly, for it is covered by hair and integument. The skull is, likewise, made rough, in particular parts, by muscular impressions, which must not be confounded with what are termed protuberances ; __in other words, with the prominences, that are formed by a cor- responding development of the brain. In this respect, craniology 308 MENTAL FACULTIES. presents more difficulties in animals, from their heads being more covered with muscles, and from the inner table of the skull being, alone, in a ratio with the brain beneath. Other errors again may be incurred from the existence of the frontal sinuses, of the superior longitudinal sinus, and from the possible separation of the hemi- spheres at the median line. The difficulty is, of course, extremely great in appreciating the parts of the brain, that are situate behind the eyes; and craniology must be entirely inapplicable to those organs of the brain, that do not terminate at its base. Gall has taken especial pains to remark, that by craniology we can only prejudge the dispositions of men, not their actions ; and that we can appreciate but one of the elements of the activity of organs — their size — not what belongs to their intrinsic activity, and to the impulse or spring they may receive from the tempera- ment, or general formation. Setting out, however, from the prin- ciple, that the predominance of a faculty is in a great measure dependent on the development of the portion of the brain which is its organ, he goes so far as to. partioijilarize, in this development, what is owing to the length of the cerebral fibres, and what to their breadth; referring the activity of the faculty to the former circum- stance, and its intensity to the latter. In applying cranioscopy to animals; he observes,that the same cerebral organ frequently occu- pies parts of the head, which seem to be very different, on account of the difference between station in animals and man, and ofthe greater or less number of systems, that compose their brain. The cerebral organs, enumerated by Gall, with the correspond- ing faculties, are as follows: — the numbers corresponding with those ofthe accompanying plate. 1. Instinct of generation, of reproduc- f tion i umativeness. Instinct of pre- V Seated in the cerebellum. It is manifested pagation ; venereal instinct. J at the surface of the cranium by two round {German.) Zeugungstrieb, N protuberances, one on each side of the nape Fortpflanzungstrieb, J ofthe neck. Geschlechtstrieb. V^ 2. Love of progeny; philoprogenitive- C ness. J Indicated at the external occipital protube- (G.) Jungenliebe, Kinder- y ranee. 1 i e b e. h (. 3. Attachment, friendships £. 5 About the middle of the posterior margin of (G.) Freundschaftsinn. C the parietal bone ; anterior to the last. 4. Instinct of defending self and pro- ( perty ; love of strife and combat; \ Seated a little above the ears; in front of the combativeness ; courage. J last, and towards the mastoid angle of the (G.) M u t h, R a u f s i n n, ^ parietal bone. Zanksinn. (_ f" Greatly developed in all the carnivorous ani- 5. Carnivorous instinct; inclination] mals; forms a prominence at the posterior to murder; destructiveness; cruelty. J and superior part of the squamous surface of (G.) Wurgsinn, Mordsinn. the temporal bone, above the mastoid ^ process. 6. Cunning ; finesse ; address ; secre- C tiveness. j Above the meatus- auditorius externus, upon (G.) List, Schlauheit, K 1 u g- j the sphenoidal angle of the parietal bones. h e i t. C fUAX 1() LOGICAL DIVISION of GALL. Tag! .308. *OJ^ l E.TLimm Sc » THE CEREBRAL ORGANS ENUMERATED BY GALL. 309 7. Desire of property ; provident in- stinct ; cupidity ; inclination to rob- bery ; acquisitiveness. (G.) Eigenthumssinn, Hang zu stehlen, Einsammlungs- sinn, Diebsinn. 8. Pride ; haughtiness ; love of au- thority ; elevation. (G.)Stolz, Hochmuth, Ho- hen sin n, Herrschsucht. 9. Vanity ; ambition ; love of glory. (G.) Eitelkeit, Ruhmsucht, E h r g e i t z. 10. Circumspection ; foresight. (G.) B ehu t s amkeit V o r sicht, Vorsichtigkeit. (_ 11. Memory of things; memory of (~ facts; sense of things ; educability ; \ perfectibility ; docility. J (G.) Sachged'achtniss, E r- ] ziehungsfahigkeit, Sach- | s in n. 12. Sense of locality; sense of the relation of space ; memory of places. (G.) Ortsinn, Raumsinn. Anterior to that of cunning, of which it seems to be a prolongation, and above that of me- chanics, with which it contributes to widen the cranium, by the projection, which they form at the side of the frontal bone. \ Behind the top of the head, at the extremity < of the sagittal suture, and on the parietal / bones. f" Situate at the side of the last, near the < posterior internal angle of the parietal (_ bones. < Corresponds to the parietal protuberances. Situate at the root of the nose, between the two eyebrows, and a little above them. 13. JMemory of persons ; sense of per- sons. (G.) Personensinn. 14. Sense of words ; sense of names; verbal memory. (G.) Wortgedachtniss, Na- me n s i n n. 15. Sense of spoken language; talent of philology ; study of languages. (G.) Sprachforschungssinn, Wortsinn, Sprachsinn. 16. Sense ofthe relations of colour talent of painting. (G.) F a r b e n s i n n. 17. Sense of the relations of tones; musical talent. (G.) T o n sinn. 18. Sense ofthe relations of numbers; mathematics. (G.) Zahlensinn. 19. Sense ofmechanics ; sense of con- struction ; talent of architecture; industry. (G.) K u n s t s i n n, B a u si n n. 20. Comparative sagacity. (G.) Vergleichender Scharf- si n n. 21. Metaphysical penetration ; depth of mind. (G.) Metaphysischer Tief- s i n n. 22. Wit. (G.) W i t z. 23. Poetical talent. (G.) Dichtergeist. "Answers to the frontal sinuses, and is indi- cated externally by two prominences at the inner edge of the eyebrows, near the root of the nose, and outside the organ of memory of things. At the inner angle of the orbit. Situate at the posterior part of the base of the two anterior lobes of the brain, on the fron- tal part of the bottom of the orbit, so as to make the eye prominent. 1 Also at the top of the orbit, between the pre- l ceding and that of the knowledge of colour. f The middle part of the eyebrows ; encroach- ing a little on the forehead. \ A little above and to one side of the last; ) above the outer third of the orbitar arch. < On the outside of the organ of the sense of (_ the relations of colour, and below the last. S A round protuberance at the lateral base of } the frontal bone, towards the temple, and ^ behind the organs of music and numbers. C At the middle and anterior part of the frontal } bone, above that ofthe memory of things. r In part, confounded with the preceding. In- N dicated, at the outer side of this last, by j two protuberances, which give to the fore- t head a peculiar hemispherical shape. r At the lateral and outer part of the last; and ^ giving greater width to the frontal promi- ( nences. c On the outer side of the last; divided into £ two halves by the coronal suture. 310 MENTAL FACULTIES. 24. Goodness ; benevolence; mild- ness ; compassion; sensibility ; moral sense ; conscience ; bonhom- mie. (G.)Gfutmiithigkeit, Mitlei- den, moralischer Sinn, Gewissen. 25. Imitation ; mimicry. (G.) Nachahmungssinn. 26. God and religion ; theosophy. (G.) Theosophisches Sinn. 27. Firmness ; constancy ; perseve- rance ; obstinacy. (G.) Stetigkeit, fester Sinn. Fig. 60. I Indicated by an oblong prominence above the organ of comparative sagacity ; almost at the frontal suture. At the outerside of the last. At the top of the frontal bone and at the su- rior angles of the parietal bones. The top of the head; at the anterior and most elevated part of the parietal bones. Fi». 61. Phrenological Organs according to Spurzheim. 1. Amativeness. 2. Philoprogenitiveness. 3. Inhabitiveness. 4. Adhesiveness or Attachment 5. Combativeness. 6. Destructiveness. 7. Constructiveness. 8. Acquisitiveness. 9. Secretive ness. 10. Self-esteem. 11. Love of Approbation. 12. Cautiousness. 13. Benevolence. 14 Vene ration. 15. Firmness. 16. Conscientiousness or Justice. 17. Hope. 18. Marvellousness. 19. Wit 20. Ideality. 21. (mitation. 22. Individuality. 23. Form. 24. Size. 25. Weight and Resistance 2H. Colour. 27. Locality. 23. Numeration. 29. Order. 30. hventuality. 31. Time. 32. Melod\ or Tune. 33. Language. 34. Comparison. 35. Causality. Melody CEREBRAL ORGANS ACCORDING TO SPURZHEIM. 3^ The first nineteen of those according to Gall are common to man and animals: the remaining eight, man possesses exclusively. They are, consequently, the attributes of humanity. Spurzheim,8 a fellow-labourer with Gall, who accompanied him in his travels, and was associated with him in many of his publica- tions, has added some other faculties, so as to make the whole num- ber thirty-five;. but they have not been embraced by Gall in his most recent publication, whence many of these details are taken ; and, indeed, many of the positions of Spurzheim are repudiated by several of Gall's followers.b The organs admitted by Spurzheim are given on the opposite page : the numbers corresponding with those of the accompanying figures. On the situation of the different cerebral organs, Gall remarks, — 1st. That those which are common to man and animals are seated in parts ofthe brain that are common to both: — at the posterior inferior, and anterior inferior, portions. On the contrary, those, that are exclusive to man, are situate in parts of the brain, which exist only in him ; — in the anterior superior parts, which form the forehead. 2dly. The more indispensable a faculty, and the more important to the animal economy, the nearer is its organ to the median line and to the base of the brain. 3dly, and lastly. The organs of the faculties, that aid, or are similar to each other, are generally situate in proximity. In his exposition of each of these organs, and of the reasons that induce him to assign it as the seat of a special faculty, he sets out by demonstrating the necessity of the faculty, which he regards to be fundamental and primary, and to which he assigns a special nervous system or organ in the brain. 2dly. He endeavours to show, that this faculty is really primary. He considers it to be such, whenever psychological facts show, that it has its exclusive source in organization; for example, when it is not common to all animals and sexes ; when, in the individual pos- sessing it, it does not exhibit itself in a ratio with the other faculties with which he is endowed ; when it has its distinct periods of development and decrease, and does not, in this respect, coincide with the other faculties ; when it can be exerted alone, be diseased alone, continued sound alone, or be transmitted alone from parent to child, &c. Lastly, he points out the part of the brain, which he considers to be its organ, founding his decision on numerous em- pirical observations of the brains of men and animals, that have possessed, or been devoid of, the faculty and organ in question ; or have had them in unequal degrees of development. It is impossible, in a work of this kind, to exhibit all the views of Gall, and the arguments he has adduced in favour of the exist- ence of his twenty-seven faculties. The selection of one — the in- stinct of generation —will be sufficient to show how he treats of the whole. Gall's instinct of generation is that, which in each ani- mal species impels the individuals of different sexes towards each » Phrenology, Amer. Edit, Boston, 1833. b Elliotson, Human Physiology, p. 384, and 1147, London, 1840. 312 MENTAL FACULTIES. other for the purpose of effecting the work of reproduction. The necessity for such an inclination for the general preservation of ani- mals is manifest. It is to the preservation of the species what the sensation of hunger is to that of the individual. Again, it is cer- tainly primary and fundamental, for it is independent of all ex- ternal influence. It does not make its appearance until puberty, and it disappears long before other faculties. In many animals it returns periodically. In each animal species, and in each indi- vidual, it has a special and different degree of energy; although external circumstances may be much the same in all, or at least may not present differences, in any manner proportionate to those of the instinct. It may be either alone active, amidst the languor of other faculties, or may be alone languishing. Lastly, it can- not be referred to the genital organs, for it has been observed in children, whose organs have not been developed ; it has frequently continued to be felt in eunuchs; and has been experienced by females who, owing to original monstrosity, have had neither ovary nor uterus.(?) The part of the brain which is the organ of this instinct, is, according to Gall, the cerebellum. His reasons for this belief are the following. 1st. In the series of animals a cerebellum exists only in those, which are reproduced by copulation, and which, consequently, must have the instinct in question. 2dly. There is a perfect coincidence between the periods at which the cerebellum becomes developed, and the appetite appears. In infancy, it does not exist, and the organ is therefore small. 3dly. In every species of animal and in every individual, there is a ratio between the size of the cerebellum and the energy of the inclination. In males, in whom it is generally more imperious, the cerebellum is always larger. 4thly. A ratio exists between the structure of the cerebel- lum and the kind of generation. In oviparous animals, for in- stance, the cerebellum is smaller at its median part; and it is only in the viviparous, that the hemispheres exist. 5thly. A similar ratio exists between the cerebellum and the external genital organs. If the latter are extirpated at an early age, the development of the cerebellum is arrested, and it continues small for the remainder of life. Neighbouring parts, too, which are attributes of the male sex, as the horns of the stag, and the crest of the cock, are often simi- larly stunted. On the other hand, the cerebellum, in its turn, exerts an intimate influence on the venereal appetite, and modifies the external genital organs. Injuries of the cerebellum either render the individual impotent, or excite erotic mania. In nym- phomania, the patient often complains of acute pain in the nape of the neck ; and this part is more tumid and hot in animals at the rutting season. Gall asserts, that he had noticed in birds, that the cerebellum differs both in size and excitation, during the season of love, from what it is at other times ; and he affirms, that if erec- tion be observed in those who are hanged, or in consequence of the application of a blister or a seton to the nape of the neck, or of the use of opium, or, who are threatened with apoplexy, especially SITUATION OF THE CEREBRAL ORGANS. 313 ' when the apoplexy is cerebellous,a or, during sleep, the effect is, in all these cases, owing to congestion of blood in the brain in general, and in the cerebellum in particular. From these data. Gall concludes, that the cerebellum is the organ of the instinct of reproduction ; and he remarks, that as this organ presides over one of the most important faculties, it is situate on the median line ; and at the base of the skull. In this manner, he proceeds, with more or less success, in his investigation of other cerebral organs and faculties. But Gall does not restrict himself to the physiological applications of his system. He endeavours, likewise, to explain the differences, that exist between him and other philosophers. He altogether rejects the primary faculties of instinct, intelligence, will, liberty, reason, perception, memory, judgment, &c. of the metaphysician, as mere generalizations of the inind, or common attributes of the true primary faculties. Whilst, in the study of physics, the general and special qualities of matter have been carefully distinguished, and the latter have been regarded as alone founding the particular nature of bodies, the metaphysician, says Gall, has restricted him- self to general qualities. For example, it is asserted, that " to think is toyee/." Thought is doubtless a phenomenon of sensibility; but it is a sensitive act of a certain kind. To adhere rigidly to this expression, says Gall, is but to express a generality, which leaves us in as much ignorance as to what thought is, as we should be of a quadruped or bird, by saying that it is an animal; and as, to be- come acquainted with such animals, their qualities must be speci- fied, so to understand thought, the kind of sensation must be speci- fied, that constitutes it. Instinct, according to him, is a general expression, denoting every kind of internal impulse -, and conse- quently there must be as many instincts as there are fundamental faculties. Intelligence is likewise a general expression, designating the faculty of knowledge ; and, as there are many instincts, so there are many kinds of intelligence. Philosophers, he thinks, have erroneously ascribed instinct to animals, and intelligence to man. All animals have, to a certain extent, intelligence; and in man many faculties are instincts. Neither is the will a fundamental faculty. It is only a judgment, formed amongst several motives, and the result ofthe concourse of actions of several faculties. There are as many desires as faculties ; but there is only one will, which is the product of the simultaneous action of the intellectual forces. So that the will is frequently in opposition to the desires. The same thing applies to liberty and reason; the former merges a See a case of Arachnitis Cerebelli — in which there was genital excitement — by the author, in Lond. Med. Rep. for Oct. 1822; also, Abercrombie on Diseases of the Brain, 3d edit. p. 60, Lond. 1836 ; and Stokes's Lectures on the Theory and Practice of Physic, Amer. Med. Lib. Edit. p. 214, Philad. 1837. For some cases of cerebellous disease, without genital excitement, see Huplay, in Archives Generates de Medecine, Nov. 1836 ; also MUIIer's Elements of Physiology, by Baly, 1st edit. p. 833, London, 1838. VOL. I. — 21 314 MENTAL FACULTIES. into what has been said of the will, and the latter is only the judgment formed by the superior intellectual faculties. In this respect, however, he remarks, it must not be confounded with intelligence : many animals are intelligent, but man alone is ra- tional. On the other hand, what are termed, in the intellect, perception, memory, judgment, imagination, &c, are attributes common to all the intellectual faculties, and cannot, consequently, be considered primary faculties. Each faculty has its perception, memory, judg- ment and imagination ; and, therefore, there are as many kinds of perception, memory, judgment, and imagination, as there are pri- mary intellectual faculties. This is so true, Gall remarks, that we may have the memory and the judgment perfect upon one point, and totally defective upon another. The memory of tones, for in- stance, is not the same as that of language ; and he, who possesses the one, may not have the other. The imaginations, again, of the poet, musician, and philosopher, differ essentially from each other. These faculties are, therefore, according to him, nothing more than different modes of the activity of all the faculties. Each faculty perceives the notion to which it has been attracted, or has percep- tion; each preserves and renews the recollection of this notion, or has memory. All are disposed to act without being excited to action from without, when the organs are largely developed or have considerable intrinsic activity, which gives rise to imagina- tion ; and, lastly, every faculty exerts its function with more or less perfection, whence results judgment. Attention, in his view, is only the active mode of exercise of the fundamental faculties of the intellect; and, being an attribute of all, it cannot be called a primary faculty. As regards the affective faculties, or what have been called the passions and affections, Gall, in the first place, asserts, that the term passion is faulty, when used to indicate a primary faculty. It ought only to designate the highest degree of activity of any faculty. Every faculty requires to be put into action, and ac- cording to the degree of activity which it possesses, it is a desire, a taste, an inclination, a want, a passion. If it be only of the medium energy, it is a taste. If, on the other hand, it be ex- tremely active, it is a passion. There may, consequently, be as many passions as there are faculties. We speak of a passion for study, or a passion for music, as we do of the passion of love, or that of ambition. Gall objects, also, to the word affection, which, according to him, expresses only the modifications the primary faculties may present, according to the mode in which the external and internal influences affect them. Some of these modes are common to all the faculties, as those of pleasure and pain. Every faculty may be the occasion of the one or the other. Other affec- tions are special to some faculties; as pretension, which, he says, is an affection of pride, and repentance an affection of the moral VIEWS OF GALL. 315 sense. Finally, these affections are simple or compound: simple when they only bear upon one faculty, as anger, which is a sim- ple affection of the faculty of self-defence ; — compound, when several faculties are affected at the same time, as shame, which is an affection of the primary faculties of the moral sense and of vanity. Gall reproaches the moralists with having multiplied too much the number of the primary affective faculties : — in his view, the modifications of a single faculty, and the combination of several, give rise to many sentiments, that are apparently different. For instance, the primary faculty of vanity begets coquetry, emulation, and love of glory. That of self-defence gives rise to temerity, courage, a quarrelling spirit, and fear. Contempt is the product of a combination of the faculties of pride and of the moral sense, &c. Lastly, as regards their psychological differences, Gall divides all men into five classes. First. Those in whom all the faculties of humanity predominate ; and in whom, consequently, organiza- tion renders the development of the mind and the practice of virtue easy. Secondly. Those in whom the organs of the animal facul- ties predominate ; and who, being less disposed to goodness, will need the aid of education and legislation. Thirdly. Those in whom all the faculties are equally energetic, and who may be either excellent individuals, or great criminals, according to the direction they may take. Fourthly. Those who, with the rest of the faculties nearly equal and mediocre, may have one predomi- nant. Fifthly, and lastly. Those who have the faculties alike mediocre : — this is the most numerous class. It is rare, however, he remarks, that the characters and actions of men proceed from a single faculty. Most commonly, they are dependent upon the combination of several; and, as the possible combinations of so many faculties are almost innumerable, the psychological varieties of mankind may be extremely various. Again, as each of the many organs of the brain may have, in different men, a particular degree of development and activity, seeing that each of the facul- ties, which are their products, has most commonly a special shade in every individual; as these organs can establish between each other a considerable number of combinations ; and as men, inde- pendently of the differences in their cerebral organization, which gives rise to their dispositions, never cultivate and exert their faculties in an equal and similar manner, it may be conceived, that nothing ought to be more variable than the intellectual and moral characters of men ; and we may thus explain, why there are not two men alike in this respect. Such is an imperfect sketch of the physiological doctrine of Gall, which we may sum up in the language of the author, in his Revue Sommaire, appended to his great work.a " I have established, a Sur les Fonctions du Cerveau, vi. 500, Paris, 1825. 316 MENTAL FACULTIES. by a great number of proofs, as well negative as positive, and by the refutation of the most important objections, that the brain alone has the immense advantage of being the organ of the mind. Farther researches on the measure of the degree of intelligence of man and animals have shown, that the brains of animals are more simple or more complex, as their instincts, desires, and faculties are more simple or more compound ; that the different regions of the brain are concerned in different categories of function; and, finally, that the brain of every species of animal, and, consequently, that of man, constitutes an aggregation of as many special organs, as there are essentially different moral qualities and intellectual faculties in the man or animal. The moral and intellectual dispo- sitions are innate. Their manifestation is dependent upon orga- nization. The brain is the exclusive organ of the mind. Such are four incontestable principles, forming the whole physiology of the brain ; and he adds, " the detailed development of the physiology ofthe brain has unveiled the deficiencies ofthe hypotheses of phi- losophers regarding the moral and intellectual powers of man; and has been the means of bringing to light a philosophy of man, founded on his organization, and, consequently, the only one in harmony with nature." It is impossible to enter, at length, into the various facts and hypotheses developed in the preceding exposition. The great points of doctrine in the system of Gall, are : — First. That the brain consists of a plurality of organs, each engaged in a separate, distinct office, — the production of a special intellectual or moral faculty. Secondly. That each of these organs ends at the peri- phery of the brain, and is indicated by more or less development of the part; and Thirdly. That, by observation of the skull, we may be enabled to detect the protuberance, produced by such cerebral development, and thus to indicate the seat of the cerebral organs ofthe different faculties. It has been shown, in the preceding history, that the notion of the plurality of organs has prevailed extensively in all ages ; and whatever may be the merit of the arguments adduced by Gall on this subject, it is difficult not to conceive, that different primary faculties may have their corresponding organs. Simple inspection of the brain indicates that it consists of numerous parts, differing essentially in structure and appearance from each other; and it is but philosophical to presume, that these are adapted to equally dif- ferent functions, although our acquaintance with "the physiology of the organs may not be sufficiently extensive to enable us to designate them. Of the innate character of several of the facul- ties, described by Gall, it is scarcely possible for us to admit a doubt. Take, for instance, the instinctst of generation and of love of progeny. Without the existence of these instincts, every animal species would soon be extinct. It seems fair, then, to pre- sume, that these instincts or innate faculties may have encephalic EXAMINATION OF THE VIEWS OF GALL 317 organs, specially concerned in their manifestation. Gall places them in the posterior part of the head, — the instinct of generation in the cerebellum; and his causes for so doing have been cited ; yet, striking as his statements in regard to the encephalic seat of the instinct of generation seems to be, it has been contested by many physiologists: by Broussais, Foville and Pinel-Grandchamp, Rolando, Flourens, Desmoulins, and others; and, not only by argument, but by that which must ultimately test the validity of the doctrines of the phrenologist—direct experiment. It is affirmed, indeed, that the genital excitement which is supposed by the followers of Gall to be seated in the cerebellum, can be equally produced by irritating the posterior column of the spinal marrow, and it would seem, that coincidence of disease of the spinal cord, with affection of the genital organs is much more frequent.3 According to Burdach, indeed, the proportion of cases of disease of the cerebellum, in which there is any manifest affection of the sexual organs is really very small, not above one in seventeen. The results, too, of unprejudiced observation, as to the compara- tive size of the cerebellum in different animals, are by no means favourable to the phrenological doctrine. There are many highly salacious animals—as the kangaroo, and the monkey, which are not distinguished for unusual size of cerebellum. A strong argument, as before observed, in favour of this function of the cerebellum, has been founded on the assertion, over and over again repeated, that the cerebellum, in animals that have been castrated young, is much smaller than in the entire male ; but'the results of the experiments of M. Lassaigne, suggested by M. Leuret,b are directly opposed to this. His experiments were made on ten stallions, of the ages of from nine to seventeen years; on twelve mares, aged from seven to sixteen years; and on twenty-one geldings, aged from seven to seventeen years. The weight of the cerebrum, estimating the cerebellum as 1, was thus expressed. Average. Highest. Lowest. Stallions - 7-07 - 7-46 - 6-25 Mares . 6-59 - 7-00 - 509 Geldings - 5-97 - 7-44 - 5-16 The average proportional size of the cerebellum in geldings was therefore positively greater than in entire horses and mares. It was also found to be absolutely heavier in the following pro- portions. Average. Highest. Lowest. Stallions - 61 65 - 56 Mares - 61 - 66 - - 58 Geldings - 70 - 76 - - 64 It would seem that the dimensions of the cerebrum are usually reduced by castration; as in the following table. » Muller's Elements of Physiology, by Baly, p. 833, Lond. 1838. >> Anat. Compar. du Systeme Nerveux, torn. i. p. 427. 21* 318 MENTAL FACULTIES. Average. Greatest. Least. Stallions - 433 485 - 350 Mares - 402 432 - 336 Geldings - 419 566 - 346 These observations are certainly entirely opposed to the statements of the phrenologists; and are more favourable to the idea of the cerebellum being connected with muscular power. Geldings, as is well known, are employed in active labour, whilst stallions are rarely called upon to exert much effort, being kept especially to propagate their kind.a The views, however, regarding the in- fluence of the cerebellum, some of which have an essential bearing on this question, will be given under the head of Muscular Motion. In regard, too, to the cerebral seat of the love of progeny or philoprogenitiveness, as it is termed, it is a fatal objection, that, although the instinct is strongly developed in the lower animals, the posterior lobes recede as we descend in the scale from man, and ultimately leave the cerebellum uncovered. One of the greatest objections that has been brought against the system of Gall is the independence in it of the different faculties of each other. Each is made to form a separate and independent state, with no federative jurisdiction to produce harmony in their actions, or to regulate the numerous independent movements and complicated associations, which must inevitably occur in the vari- ous intellectual and moral operations. Gall appears indeed to have lost sight of the important doctrine of association, which applies not only to the ideas, but to every function of the frame; and with which it is so important, for the pathologist particu- larly, to be acquainted. The second point of doctrine, — that each ofthe cerebral organs ends at the periphery ofthe brain, and is indicated by more or less development ofthe part, — is attended with equal difficulties. It is admitted, as we have seen, by the most eminent physiologists, that the exterior part ofthe brain is probably chiefly, concerned in the mental and moral manifestations. Almost all believe, that this function is restricted to the brain proper. Gall and his fol- lowers include the cerebellum. Yet we meet with cases, which appear to militate strongly against this notion. Hernia of the brain is one of these : in this, owing to a wound of the cranium and dura mater, a portion ofthe cerebral substance may protrude and be removed; yet the individual may do well, and to all ap- pearance retain his faculties unimpaired. This is explained by the craniologist, by presuming, that as the fibres of the brain are vertical, their extremities have alone been removed, and a suffi- cient amount of fibres may have remained for the execution of the function ; and he farther entrenches himself in the difficulty of observing accurately, in these cases, whether the faculties be really in their pristine integrity. He asserts, that it is frequently ex- tremely difficult to prove the existence of mental aberration; that a Carpenter's Human Physiology, p. 210, London, 1842. EXAMINATION OF THE VIEWS OF GALL. 319 the precise line of demarcation between reason and unsoundne ss of mind is not easily fixed; and that commonly, in these cases, attention is paid only to the most general qualities, and if t he patient be seen to take food and medicine when offered to him, to reply to questions put to him, and have consciousness, the moral sense is esteemed to be free, and in a state of integrity. It must, however, be admitted, that the explanation of the craniologist on these topics is feeble and unsatisfactory. It is, of course, gratui- tously assuming, that observation in such cases has been insuffi- cient ; and if he find, that the fact in question militates against the faith he has embraced, he is too apt to deny its authenticity alto- gether. With all the candour which Gall possessed, this failing is too perceptible in his writings. Again, in many ofthe cases of severe injury of the brain, which are on record, but one hemisphere was implicated; and accord- ingly, the impunity of the intellectual and moral manifestations has been ascribed to the cerebrum being a double organ ; so that, al- though one hemisphere may have been injured, theother,containing similar organs, may have been capable of carrying on the function; as one eye can still execute the function of vision, when the other is diseased or lost. Cases, however, have occurred in which the faculty has been lost, when only one hemisphere was implicated. Such cases are given by Mr. Combe. One interesting example, the author heard Mr. Combe relate. A gentleman suddenly forgot all words but yes and no, and after death a lesion was found in the left hemisphere of the brain, involving the phrenological organ of language. The explanation by Mr. Combe of this phenomenon is plausible but not probable. It appears to me, he observed, " that the lesion's being on one side only accounts for his power of understanding words, while he had not the power of employing them."a Many cases, again, are recorded, in which injury was sustained by both hemispheres, and in corresponding parts ; yet the faculties persisted ;b whence Miiller has concluded, that the histories of in- juries ofthe head are directly opposed to the existence of special regions of the brain, destined for particular mental faculties. Cases of hydrocephalic patients are likewise cited, who have pre- served their faculties entire. These Gallc explains, by affirming, that the brain is not dissolved in the fluid of the dropsy ; that it is 1 Combe's Lectures, by Boardman, p. 261, New York. b See a fatal case of disorganization of the brain, without corresponding derange- ment of the intellectual and moral acts, by Dr. G. W. Boerstler, of Lancaster, Ohio, in Dunglison's American Medical Intelligencer, No. 1, for April l, 1837. Mr. Combe, in his work,__Motes on the United States of J\'orth America, during a phreno- logical visit in 1838-39-40; Phila. 1841 —refers to a case of injury of both he- mispheres, which he thinks, from examining the case, was confined almost entirely to the organs of Eventuality. The man recovered, and was exhibited to Mr. Combe with a history of his case by Drs. Knight and Hooker, of New Haven. In the opinion of the latter, the intellectual faculties were not impaired. — vol. ii. p. 276. c Op. citat. ii. 263. 320 MENTAL FACULTIES. only deployed, and distended by the presence of the fluid ; and as the distension takes place slowly, and the pressure is moderate, the organ may be so habituated to it as to be able to continue its func- tions. Lastly, some experiments of Duverney* have been adduced as objections to the view of Gall. These consisted in removing the whole of the brains of pigeons; yet no change seemed to be produced in their faculties; but, in reply to this, it is asserted, that Duverney could only have removed some of the superficial parts of the organ ; for, whenever the experiment has been repeated, so as to implicate the deeper seated portions, opposite results have been obtained. The truth is, that under any view of the subject these facts are equally mysterious. We cannot understand why, in particular cases, such serious effects should result from severe injury done to the brain ; and, in others, the comparative immunity attendant upon injury to all appearance equally grave. Pressure, of what- ever nature, seems to be more detrimental than any other variety of mechanical mischief; and it is not uncommon for us to observe a total privation *of all mental and moral acts, by the sudden effu- sion of blood, — of no greater magnitude than that of a pea,— into the substance of the brain ; whilst a gun-shot wound, that may occasion the loss of several tea-spoonfuls of brain, or a puncture of the organ by a pointed instrument, may be entirely consistent with the existence of perfect consciousness. The doctrine, that, by observation of the skull, we may be able to detect the protuberance produced by the cerebral organs of the different faculties, has, as we have seen, laid the foundation for the whole system of craniology, with all the extensions given to it by absurdity and vain enthusiasm. It has been before remarked, that the size of an organ is but one of the elements of its activity ; that, by cranioscopy, we can of course judge of this element only; and it need scarcely be said, that myriads of observations are necessary before we can arrive at any accurate specification of the seats of the cerebral faculties, even were we to grant, that separate organs can be detected by the mode of examination proposed by the cranio- scopist. Gall, indeed, asserts, that the whole " physiology of the brain is founded on observations, on experiments, and on researches a thousand and a thousand times repeated on man and animals;" yet the topographical division of the skull, which he has proposed, can hardly be regarded otherwise than premature, to say the least of it ;b and the remark of course applies a fortiori to that of Spurzheim. It is indeed difficult to grant, that the same convolutions can be the cerebral organs of distinct faculties; and if the views now adopted by many of the phrenologists, be admitted, that the number and size of the convolutions and the depth of the anfractuosities a Adelon, Physiologie de l'Homme, 2de 6dit. i. 502, Paris, 1829. b Elements of Physiology by Baly, p. 837, Lond. 1838. EXAMINATION OFTHE VIEWS OF GALL. 321 be any index of the development of an organ; it is obviously impossible by an examination of the skull to form the slightest judgment on these points. Leuret and Carpenter* are of opinion, that comparative anatomy and psychology — which have been so much invoked — when their evidence is fairly weighed, are very far from supporting the % system. Flourensb has recently op- posed it vigorously on anatomical, physiological, and pyschological grounds; and Mullerc thinks Magendie very right in placing cranio- scopy in the same category with astrology and alchemy. The author would not go so far, but he must candidly admit that year after year's observation and reflection render him less and less disposed to consider that even the fundamental points of the doc- trine are founded on a just appreciation of the encephalic functions. It is the mapping of the skull, accompanied by the self-conceit and quackery of many of the soi-disant phrenologists or craniologists, which has excited the ridicule of those, who are opposed to the doctrine of innate faculties, and to the investigation of points con- nected with the philosophy of the human mind in any other mode than that to which they have been accustomed and are adapted. Were we, indeed, to concede, that the fundamental princi- ples of craniology are accurate, we might hesitate in adopting the details; and still more in giving any weight to it as a practical science. Gall and Spurzheim would rarely venture to pronounce on the psychical aptitudes of individuals from an examination of their skulls; and when they did, they frequently failed. « When Gall," says Dr. Burrows,13 " was in England, he went in company with Dr. H. to visit the studio of the eminent sculptor, Chantry. Mr. C. being at the moment engaged, they amused themselves in viewing the various efforts of his skill. Dr. Gall was requested to say, from the organs exhibited in a certain bust, what was the predominant propensity or faculty of the individual. He pronounced the original must be a great poet. His attention was directed to a second bust. He declared the latter to be that of a great mathematician, the first was the bust of Troughton, and the second that of Sir Walter Scott!" This kind of hasty judgment, from manifestly inadequate data, is the every-day practice of the itinerant phrenologist, whose oracular dicta too often draw down ridicule not only upon the empiric him- self, but on a system which is worthy of a better fate. Ridicule is, indeed, the harmless but attractive weapon, which has usually been wielded against it; and too often by those, who have been ignorant both of its principles and details. It is not above twenty years since one of the most illustrious poets, that Great Britain has produced, included, in his satire, the stability of the cow-pox, galvanism, and gas, along with that of the metallic tractors of Perkins — * Human Physiology, p. 226, Lond., 1842. b Journal des Savans, Nov. 1841, & Fevr. & Avnl, 1842. c Op. citat. p. 837. a Commentaries on the Causes, Forms, Symptoms and Treatment of Insanity, Lond. 1828. 322 MENTAL FACULTIES. " The cow-pox, tractors, galvanism, and gas, In turns appear to make the vulgar stare Till the swoll'n bubble bursts, and all is air :" JByron's " English Bards and Scotch Reviewers." Yet how secure in its operation, how unrivalled in its results, has vaccination every where exhibited itself! The indiscriminate divination from measurement of heads has been a sad detriment to phrenology as a branch of physiologi- cal science, and has been grievously deplored by enlightened physiologists. " Highly as we estimate the discovery of Gall," , — says one of the ablest of phrenologists3 — " immense as we re- gard the advantages which may be ultimately derived from phre- nology, we confess, that we wish to see it less regarded, studied, and pursued as a separate science, and more as a branch of gene- ral physiology;" and he adds, " In reviewing the circumstances, which have tended to lower phrenology in the estimation of scien- tific men, and, consequently, to retard both its progress as a science, and the general recognition of its leading truths, we should but very imperfectly perform our task, if we did not refer, in the strongest possible terms of reproof and condemnation, to the too prevalent proceeding of examining living heads in minute detail and indis- criminately, and supplying the owners with an account of the 'development,' often on the receipt of a fee, varying in amount, as there is furnished or omitted a general deduction as to the charac- ter and probable conduct of the individual, with or without the ' philosophy,' according to the phraseology of practitioners of this art. We unhesitatingly maintain, that the science is not sufficiently advanced to supply evidence of its truth from every head, or from any one head, and consequently, that such practice, as a general one, is so much pure charlatanism. Where any strongly marked peculiarity of individual character exists, its outward sign, in ap- propriate subjects, will certainly be detected; but, from the very nature of the thing, these cases must constitute, not the rule, but the exception. The practice we condemn, however, makes no distinction of instances. Injudicious zeal, the common ally of igno- rance, a wish for effect, not unfrequently more sordid motives, stimulate the self-styled phrenologist in this empirical career; and, as a matter of course, the errors and mistakes perpetually made are constantly appealed to as indicative of the sandy foundations of the entire phrenological edifice. We write advisedly in this our unqualified reprobation of the popular custom of ' taking develop- ments.' We believe it to be an extension of the practical applica- tion of phrenology much beyond its legitimate bounds; and we appeal to any one having acquaintance with its results, whether any thing like uniformity — the true test of accuracy — is obtained in the majority of cases, even when the most experienced and dex- terous pronounce their judgment, if their explorations be conduct- ed separately. We ourselves have even witnessed the greatest * British and Foreign Medical Review, July, 1842. EXAMINATION OF THE VIEWS OF GALL. 323 possible discrepancies. Nay, we have seen the same phrenologist, furnish one character from the head, and a totally different one from the cast, whilst in ignorance of the original of this latter. This we have known to happen, not merely in the practice of one of your shilling-a-head itinerants, but in that of one not unknown to fame in the annals of the science." Such are the views of one, who, unlike the author, expects much from phrenology, and has done much to give it countenance. Yet men will still form their judgments in this manner; and a solitary coincidence, as in all similar cases, will outweigh a dozen failures. The views of Gall require numerous and careful experiments, which it is not easy for every one to institute ; and this is one of the causes, why the minds of individuals will long remain in doubt regarding the merits or demerits of the system. From mere meta- physicians, who have not attended to the organization and func- tions of the frame, especially of its encephalic portion, it has ever experienced the greatest hostility; although their conflicting views regarding the intellectual and moral faculties was one of the grounds for the division of the phrenologist. It is now, however, we believe, generally admitted by the liberal and scientific, that if we are to obtain a farther knowledge of the mental condition of man, it must be by a combination of sound psychological and phy- siological observation and deduction. It is time, indeed, that such a union should be effected, and that the undisguised and inveterate hostility, which exists between certain of the professors of these interesting departments of anthropology, should be abolishedi " To fulfil, definitely, the object we had proposed to ourselves," says Broussais,a "we must infer from all the facts and rea- soning comprised in this work, — 1st. That the explanations of psychologists are romances, which teach us nothing new. 2dly. That they have no means of affording the explanations they promise. 3dly. That they are the dupes of the words they employ in disserting on incomprehensible things. 4thly. That the physi- ologist alone can speak authoritatively on the origin of our ideas and knowledge; and 5thly. That men, who are strangers to the science of animal organization, should confine themselves to the study of the instinctive and intellectual phenomena, in their rela- tions with the different social states of existence." This is neither the language nor the spirit that should prevail among the promoters of knowledge. Lastly. Physiologists have inquired whether there be not some particular portion of the brain, which holds the rest in subser- vience ; some part in which the mind exclusively resides; — for such was probably the meaning of the researches of the older physiologists into the seat of the soul. It is certain, that it is seated in the encephalon, but not in the whole of it; for the organ may be sliced away, to a certain extent, with impunity. Gall, we have seen, does not admit any central part of the encephalon, * De l'lrritation et de la Folie, Paris, 1828: or Amer. Edit, by Dr. T. Cooper, Columbia, N. C, 1831. 324 MUSCULAR MOTION. which holds the others in subordination. He thinks, that each cerebral organ, in turn, directs the action of the others according as it is, at the time, in a state of greater excitation. On the other hand, different physiologists admit of a central cerebral part, which they assert to be the seat of the 4^, moi or mind. They differ, however, regarding the precise situation of its domicile. At one time, the notion prevailed, that the seat of perception is not in the brain itself, but in its investing membranes. Descartes," again, embraced the singular hypothesis, that the pineal gland is enti- tled to this pre-eminence. This gland is a small projection, seen in Fig. 4 (page 56), at the posterior part of the third ventricle, and, consequently, at the base of the brain. Being securely lodged, it was conjectured by that philosopher, that it must be inservient to some important purpose ; and, upon little better grounds, he supposed, that the soul is resident there. The conjecture was considered to be confirmed by the circumstance, that, on examining the brains of certain idiots, the pineal gland was found to contain a quantity of sabulous matter. This was supposed to be an ex- traneous substance, which,owing to accident or disease, was lodged in the gland and impeded its functions; and the inference was thence drawn, that the part, in which such functions were im- peded, was the seat of the soul. Nothing, however, is now better established than that the pineal gland of the adult always contains such earthy matter.b Others, again, as Bontekoe,c La Peyronie,*1 and Louis, placed the mind in the corpus callosum ; Vieussens in the centrum ovale ; Digbye in the septum lucidum ; Drelincourtf in the cerebellum ; Ackermann in the Sinneshiigel* (promi- nence or tubercle of the senses); Sommeringh in the fluid of the ventricles; and the greater part of physiologists in the point where the sensations are received and volition sets out,—the two func- tions, which, together, compose the sensorial power of Dr. Wilson Philip.1 Darwin had previously employed this term in a more extended sense, as including the power of muscular contraction ; but in Dr. Philip's acceptation, it is restricted to those physiological changes in which the mind is immediately concerned.14 The discrepancy among physiologists sufficiently demonstrates, that we have no positive knowledge on the subject. a De Passion. Anim., Amst. 1664. b Sommering, De Lapillis vel prope vel intra Glandulam Pinealem sitis. Mogunt, 1785. |= Haller, Bibl. Anat. i. 673. a Mem. de l'Academ. des Sciences, Paris, 1741. <= Ofthe Nature of Bodies and the Nature of Man's Soul, Lond. 1658. f Opera. Anat. Ludg. Bat. 1684. s This term he applies to the optic thalami and corpora striata ; because, according to the received opinion, the optic nerves arise from the optic thalami; and the olfactory nerves from the corpora striata. — Gall, Sur les Fonctions du Cerveau, ii. 57, Paris, ]825. h De Corp. Human. Fabric, iv. § 98. ! An Experimental Inquiry into the Laws of the Vital Functions, p. 186, Lond. 1817. k Darwin's Zoonomia, Lond. 1796 ; Dr. Philip, ibid.; and especially his paper on the Powers of Life, in the Lond. Med. Gazette, for March 18 and 25, 1837; also his Treatise on Protracted Indigestion, &c, Amer. Edit. Philad. 1843. MUSCLES. 325 CHAPTER II. OP MUSCULAR MOTION, ESPECIALLY LOCOMOTILITY OR VOLUNTARY MOTION. The functions which we have hitherto considered are prelimi- nary to those that have now to attract attention. The first in- struct us regarding the bodies that surround us; the second en- able us to act upon them; to execute all the partial motions, that are necessary for nutrition and reproduction; to move about from one place to another, &c, &c. All these last acts are of the same character : they are all varieties of muscular contraction ; so that sensibility and voluntary motion, or muscular contraction, executed by the muscular system of animal life, comprise the whole of the life of relation. Magendie includes the voice and movements under the same head; but there is convenience in separating them, and in treating the functions of locomotility and expression distinctly, as has been done by Adelon.a 1. ANATOMY OP THE MOTORY APPARATUS. The organs essentially concerned in this function are — the encephalon, the spinal marrow, the nerves, and the muscles. The three first of these have been sufficiently described. The last, therefore, will alone engage us. 2. OF THE MUSCLES. The muscles constitute the flesh of animals. They are distin- guished by their peculiar structure and composition; being formed of the elementary or primary fibrous tissue, already described. This tissue has the power of contracting, and thus of moving the parts into which it is inserted; hence, muscles have been termed active organs of locomotion, in contradistinction to the bones, ten- dons, and ligaments, which are passive. The elementary constituent of the whole muscular system is this primary, fibrous, or muscular tissue, the precise size and inti- mate texture of which have been the occasion of innumerable researches ; and, as most of them have been of a microscopic cha- racter, they are highly discrepant. A brief detail of these specu- lations will exhibit this truth. Leeuwenhoekb asserts, that some thousands of the ultimate fila- ments are required to form the smallest fibre that is visible to the naked eye. He describes the fibre as serpentine and cylindrical; and affirms, that the fibres lie parallel to each other, are of the same shape in all animals, but differ greatly in their size. The size, however, bears no proportion to that of the animal to which » Physiologie de l'Homme, 2d edit. ii. 1 and 204, Paris, 1829. >> Arcana Naturae, p. 43. VOL. I. — 28 326 MUSCULAR MOTION. they belong. Muysa affirmed, that each apparent fibre is com- posed of three kinds of fibrils, progressively smaller than each other ; and that those of the medium size, although not larger than the ninth part of a very delicate hair, are composed of one hundred filaments. He supposed the ultimate filament to be always of the same size. Prochaskab says, that the ultimate fibre or filament is discernible, and that it is about the Tyh part of the diameter of the red globules of the blood in thickness ; and MM. Prevost and Dumas,c from the result of their microscopic observations, affirm, that 16,000 fibres may be contained in a cylindrical nerve, one millimeter, or 0-039 of an inch, in diameter. The microscopic examinations of Mr. Skeyd have led him to infer, that there is a distinction between the muscular fibres of animal and of organic life ; the former having, in man, an average diameter of ^otn of an inch. Each of these muscular fibres is divisible into bands or fibrillse, each of these again subdivisible into about 100 tubular filaments, arranged parallel to each other: the diameter of each filament is T^-0^th part of an inch, or about a third part of that of a blood globule. The muscles of organic life he found to be composed, not of fibres similar to those described, but of filaments only; these filaments being interwoven, and forming a kind of untraceable network. The fibres of the heart appeared to possess a somewhat compoundcharacter of texture: the muscles of the pharynx exhibited the character of those of animal life : whilst those of the oesophagus, the stomach, the intestines, and the arterial system possessed that of inorganic life. He was unable to determine the exact nature of the muscular fibres of the iris. The intimate structure of the filaments has likewise given rise to extraordinary contrariety of sentiment; — some as Santorini, Heister, Cowper,e Vieussens, Mascagni/ Prochaska,s Borelli,h John Bernouilli, &c, believing them to be hollow ; others, as Sir A. Carlisle,1 Fontana,k solid ; some believing them to be straight; others zigzag, spiral, or waved; some jointed ; others knotted, &c, &C1 Borelli and J. Bernouilli announced, that each fibre consists of a series of hollow vesicles, filled with a kind of spongy substance or marrow ; — the shape of these vesicles being, accord- ing to the former, rhomboidal, — according to the latter spheroidal. Deidier conceived it to be a fasciculus, composed of an artery, vein, and lymphatic, enveloped by a nervous membrane, and held together by nervous filaments: — Prochaska, to consist of blood- a Investigatio fabrics quae in partibus musculos componentibus exstat, p. 274, Lugd. Bat. 1841. b De Came Musculari, p. 25, Vienn. 1778. c Annales de Chimie, torn, xviii.; Magendie's Journal de Physiologie, torn. iii. d Transactions of the Royal Society, for 1836. e Myotomia Reformata, Lond. 1724. f Prodromo, p. 97. b Oper. Minor. P. i. 198. h De Motu Animalium; Addit. Johan. Bernouilli, M.D. Meditationes Mathematic. Musculorum, Lugd. Bat. 1710. ' Phil. Trans, for 1805, p. 6. * Sur les Poisons, torn. ii. 228 1 Elliotson's Physiology, p. 476. MUSCLES. 327 vessels turned spirally around an axis of gelatinous or fibrinous substance, into the interior of which the blood rushed at the time of contraction. He says, that the visible fibres are not cylindrical, as they had been described by many observers, but of a polyhe- dral shape ; and that they are generally flattened, or thicker in one direction than in the other. They are not all of the same diameter, but differ in different animals, and in different parts of the same animal: they are smaller, too, in young subjects. The filaments or ultimate fibres, which can only be seen with the microscope, have the same shape as the visible fibres ; they are, however, always of the same magnitude. Sir A. Carlisle,8 — whose opi- nions, on many subjects at least, are not entitled to much weight, — describes, the ultimate fibre as a solid cylinder, the covering of which is a reticular membrane, and the contained part a pulpy substance, regularly granulated, and of very little cohesive power when dead. The extreme branches of the bloodvessels and nerves, he says, are seen ramifying on the surface of the mem- brane enclosing the pulp, but cannot be traced into the substance of the fibre. Mr. Bauerb and MM. Prevost and Dumas,c again, differ essentially from the observers already mentioned. Mr. Bauer found, that the muscular fibre was composed of a series of globules, arranged in straight lines; the size ofthe globule being j^i^th Part °f an mcn m diameter ; and lastly, Raspaild considers that the intimate structure ofthe muscular tissue, when it is in its most simple state, consists of a bundle of cylinders, intimately agglutinated together, and disposed, in a very loose spiral form, around the ideal axis of the group. These tubes are filled with a substance not wholly miscible with water, and may be regarded as elongated vesicles, united at each end to other vesicles of a similar character. When a muscular fibre is seen through an ordinary microscope, it appears to be composed of longitudinal filaments, each consist- ing of a string of globules, about ■g-sVsth of an inch in diameter. " But with a better instrument," says Mr. Mayo,e " such as that which Mr. Lister possesses, the delusion vanishes, and the parallel lines, which traverse the fibre, appear perfectly clean and even. Mr. Lister politely gave me an opportunity of examining this appear- ance, which was discovered by himself and Dr. Hodgkin." The latest researches of Mr. Bowmanf and others are as follows. When the smallest fibre, that can be seen by the naked eye is ex- amined by the microscope, it is found to consist of a number of » Op. citat. t> Sir E. Home, Lectures on Comp. Anat. v. 240, Lond, 1828. c Appendix to Edwards de l'lnfluence des Agens Physiques sur la Vie, Paris, 1824. d Chimie Organique, &c. p. 211, Paris, 1833. e Outlines of Human Physiology, chap. iii. 3d edit. London, 1833. See, also, Mr. Skey, Philosophical Transactions, for 1837, p. 104 ; and, on the whole subject, Henle, Allgemeine Anatomie u. s. w. S. 585, Leipz. 1841. t Philosophical Transactions for 1840; also in Todd and Bowman's Physiological Anatomy and Physiology of Man, Part 1, Lond. 1843. 328 MUSCULAR MOTION. Fig. 63. Fasciculus of Fibres of Voluntary Muscle ; the fibres separated at one end, into brush-) ike bundles of fibrillae. —(Baly.) Ulj '"' cylindrical fibres lying parallel to each other, and closely bound to- gether. These fibres present striae — one set of which is longitudinal, the other transverse. When the fibres are separated from each other, and examined more closely, they may be resolved into fibrillae, which, so far as at present known, are the ultimate elements of mus- cular structure. They are re- presented in the marginal figure. The fibrillae are bound together by a delicate tubular sheath or sarcolemma, which may be dis- tinctly seen, when the two ends of a fibre are drawn apart. The contained fibrillse will rupture, whilst the sheath remains entire, as represented in Fig. 64. Fig. 64. During the act of contraction, it is also sometimes observed to rise up in wrinkles, upon the surface of the fibre, as in Fig. 76. It is distinct from the cellular tissue that binds the fibres into fasciculi. It does not appear to be perforated either by nerves or capillary vessels • and evidently has no share in the contraction of the fibre. Although commonly described as cylindrical, these fibres would seem to be rather of a polygonal Fis- 65- form, their sides being flattened against those of adjoining fibres. Their size varies greatly in different classes of animals, and even in the same animal and the same mus- cle. Mr. Bowman found them to vary,in the human male, from T%T to r%2 °f an inca 5 in the female, from ih t0 nhi and ^ has been estimate Fibre of human muscle broken across ; the frag- ments connected by the untorn sarcolemma. - [Bowman.) h Transverse Seetion of Fibres from the Pectoral Muscle of a Teal. MUSCLES. 329 Fig. 66. Transverse Section of Ultimate Fibres of Biceps. — {Bowman.) The Fig. 67. ed, that each fibre may be composed of from 500 to 800 fibrillae Illustration, Fig. 65, of a trans- verse section of the fibres from the pectoral muscle of a teal, and Fig. 66, of a transverse section of the ultimate fibres of the biceps, exhibit well the irregular shape and size, and the cut extremities of the fibrils that go to the constitution of the fibre. The fibrillae do not appear to be hollow, as has been conceived by some. Under the microscope each fibre exhibits a close alternation of light and dark lines crossing it transversely, which are presumed to be owing to the arrangement of beaded fibrillas, as shown in Fig. 67 beaded enlargements of the fibrillae seem to adhere closely to each other, so that when the extremities of a fibre are drawn apart, it will not unfrequently happen, that the disks formed by them will separate. It has been affirmed, indeed, that the primitive component segments ofthe fibrillas are the ultimate elements of the fibre ; these segments being connected longitudinally, so as to constitute the fibrillas, the distinctness of which is marked, even in the complete Fig. 68. fibre by longitudinal striae; whilst they also adhere laterally, so as to form disks, the partial separa- tion of which gives origin to the trans- verse striae.b The muscular fibres of organic life present no trans- verse strise, and the longitudinal striae are very faint.0 Their size, too, is usually much less than that of the fibres of animal life. Their precise arrangement, as seen by Mr. Skey, has been given already The views of histologists on the whole of this subject are, how- a Carpenter, Human Physiology, § 369, Lond. 1842 ; and Mr. Paget, Brit, and For. Med. Rev. July, 1842, p. 274. b Carpenter, op. cit. § 370 c Gerber, Elements of General and Minute Anatomy, by Gulliver, p. 232, Lond. 1342. 28* Fragment of Muscular fibre from macerated heart of Ox, showing formation of strise by aggregation of beaded fibrillae. — (Bowman.) Portion of Human Muscular fibre, separating into disks, by cleavage in direction of transverse striae. — {Bowman.) 330 MUSCULAR MOTION. Fig. 69. ever, sufficiently discrepant. Dr. Martin Barry3 has recently re- vived a view of Dollinger, that the blood corpuscle is the imme- diate agent in the construction of many tissues, particularly the muscular — the elementary fibre of which —called by him a spi- ral fibre— may even be detected in, the nucleus of the corpuscle. Very recently, Mr. Bowmanb has affirmed, that the muscular fibre always presents, upon and within it, longitudinal dark lines, along which it will generally split up into fibrillae, but it is by a fracture alone, that such fibrillae are obtained. They do not exist as such in the fibre. He farther observed, that it occasionally happens that no disposition whatever is shown to this longitudinal cleavage ; but that, on the contrary, violence causes a separation along the trans- verse dark lines, whichalways intersect the fibre in a plane perpendi- cular to its axis. By such a cleavage, disks and not fibrillae are obtained ; and this cleavage is as material as, although less fre- quent than, the former. Hence, he esteems it as proper to say, that the fibre is a pile of disks, as that it is a bundle of fibrillae, but that it is, in fact, neither one nor the other ; but a mass on the struc- ture of which there is an intimation of the ex- istence of both, and a tendency lo cleave in the two directions. If there were a general dis- integration along all the lines in both directions, there would result a series of particles, which might be termed primi- tive particles or sarcous elements, the union of which would constitute the mass of the fibre; these elementary par- ticles being arranged and united together in the two directions. Gerber,c again, is dis- posed to consider, that the " cross-streaking" seems frequently to depend on the presence of a wrinkled fascicular sheath; a Philosophical Transactions, for 1842, Pt. i. p. 89. b Physiological Anatomy and Physiology of Man, Part 1, Lond. 1842. c Op. cit. p. 251. Fragments of Striped Elementary Fibres, Showing a Cleavage in Opposite Directions ; Magnified 300 Diameters. a. Longitudinal cleavage. The longitudinal and trans- verse lines are both seen. Some longitudinal lines are darker and wider than the rest, and are not continuous from end to end: this results from partial separation ofthe fibrillae. c. Fibrillar, separated from one another by violence at the broken end of the fibre, and marked by transverse lines equal in width to those on the fibre, c' c" represent two appearances commonly presented by the separated single fibrillae. (More highly magnified.) At c\ the borders and transverse lines are all perfectly rectilinear, and the included spaces perfectly rectangular. At c", the borders are scal- loped, the spaces bead-like. When most distinct and definite the fibril I a presents the former o£ these appearances. — b. Transverse cleavage. The longitudinal lines are scarcely visible, a. Incomplete fracture following the opposite sur- faces of a disk, which stretches across the interval and re- tains the two fragments in connection. The edge and sur- face of this disk are seen to be minutely granular, the gra- nules corresponding in size to the thickness of the disk, and to the distance between the faint longitudinal lines, b. An- other disk nearly detached, b'. Detached disk more highly magnified, showing the sarcous elements. — {Todd and Bowman.) MUSCLES. 331 " for when," he says, " the more superficial fibres chance to be removed, and the deeper ones exposed, these appear cylin- drical, and the bundle at the part is longitudinally streaked. At the extremity of a torn fasciculus, too, the peripheral fibres often appear so distinctly marked off from the internal and more pulpy substance, that the existence of a more compact transversely streaked sheath can scarcely be called in question." Lastly, Dr. Goddard3 is of opinion from his own observations, that the trans- verse striae seem to be produced by a delicate thread of cellular tissue wound spirally around the ultimate fibrils, so as to hold them in a bundle. Such is the transition state in which this ques- tion of general anatomy is now placed. The ultimate fibres, or filaments, when united in bundles, form fasciculi or lacerti : and these, by their aggregation, constitute the various muscles. Each fibre, each lacertus, and each muscle, is surrounded by a sheath of cellular tissue, which enables them to move readily upon each other, and preserves them in situ. The fibres are not the same at the extremities as they are at the middle. The latter only consist of the proper muscular tissue ; the extremities being formed of cellular tissue. If we examine a muscle, we find, that the proper muscular fibres become gradually fewer, and at length cease to be perceptible, as they approach the tendon at one or other extremity. In this way, the cellular mem- brane, which surrounds every fibre, becomes freed from the mus- cular tissue ; its divisions approximate, and become closely united and condensed, so as to form the cord ox tendon, which, of course, holds a relation to each fibre of the muscle ; and when they all contract, the whole force is exerted upon it. The microscopic observations of Mr. Bowman exhibited to him, that the component fibres of the tendinous structure are arranged with great regu- Fig. 70. Attachment of Tendon to Muscular Fibre, in Skate. — (Bowman.) larity, parallel to each other, and are attached to the end ofthe sarco- lemma, which terminates abruptly, as in Fig. 70, which shows the a Wilson's Anatomist's Vade Mecum, by Dr. Goddard, Amer. Edit., p. 142, Philad. 1843. 332 MUSCULAR MOTION. attachment of the tendon to the muscular fibre in the skate. This arrangement will explain the close union which exists between the muscle and its tendon, and which has given occasion to the belief, that the latter is only the former condensed. An examination of someof the physical and vital properties ofthe two will show, that they differ as essentially as any two of the con- stituents of the body that could be selected. The tendon consists chiefly of gelatin, and does not exhibit the same irritability; whilst the muscle is formed essentially of fibrin, and contracts under the will, as well as on the application of certain mechanical and chemical irritants. The differences, in short, that exist between the two, are such as distinguish the primary fibrous and cellular tissues; yet the opinion of their identity prevailed in antiquity, was embraced by Boerhaave and his school, and, as Dr. Bostocka observes, was so generally admitted, even in the middle ofthe last century, that Haller,b and Saba tierc scarcely ventured to give a decided opposition to it. Similar remarks are applicable to the notion of Cullen,d that muscles are only the moving extremities of nerves. The fibres of the muscle were supposed by him to be continuous with those of the nerve ; to be, indeed, the same substance, but changed in structure, so that when the nerve is converted into muscle, it loses the power of communicating feeling, and acquires that of pro- ducing motion. Every muscle and every fibre of a muscle is probably supplied with bloodvessels, lymphatics and nerves. These cannot be traced into the ultimate filament, but, as this must be possessed of life and be contractile under the will, it must receive through the bloodvessels and nerves the appropriate vital agency. MM. Dumas and Pr6vost,e and Mr. Bowman,—as has been said, — affirm, that the microscope shows, that neither the one nor the other ter- minates in the muscle. The vessels merely traverse the organs ; the arteries terminating in corresponding veins ; so that the nutri- tion of muscles is effected merely by the transudation of plas- tic materials through the parietes of the artery, in the same manner as various other parts — teeth, hair, cartilages, for ex- ample — are probably nourished. A similar distribution they assign to the nerves. All the branches, they assert, enter the mus- cle in a direction perpendicular to that of the fibres composing it ; and their final ramifications, instead of terminating in the muscu- lar fibres, surround them loopwise, and return to the trunk that furnished them, or anastomose with some neighbouring trunk. In their view, each nervous filament, distributed to the muscles, sets out from the anterior column of the spinal marrow, forming part of a nervous trunk, turns round one or more muscular fibres, a An Elementary System of Physiology, p. 84, 3d edit. London, 1836. b Elem. Physiol, ii. 1, 18. <= Traite complet d'Anatomie, i. 242, Paris, 1791. d Institutions of Medicine, § 29, 94. e Magendie's Journal de Physiologie, torn. iii. MUSCLES. 333 and returns along the same or a neighbouring trunk to the poste- rior column of the marrow. The red colour of muscles is usually ascribed to the blood dis- tributed to them, as it may be removed by repeated washing and maceration in water or alcohol, without the texture of the muscle being modified. By some, it has been thought, that a quantity of red blood remains attached to the fibres, and is extravasated from the vessels ; by others, it is presumed, with more probability per- haps, to be still contained in the vessels. Bichata conceived, that the colour is dependent upon some foreign substance combined with the fibre ; and he grounds his opinion upon the circumstance that, in the same animal, some of the muscles are always much redder than others; and yet they do not appear to have a greater quantity of blood sent to them; and also that, in different classes of animals, the colour of the muscles does not appear to corre- spond with the quantity of red blood circulating through their ves- sels. The fact, however, that, when muscles have been long in a state of inaction, they become pale ; and that, on the other hand the colour becomes deeper, when they are exercised, is an addi- tional evidence, that their colour is dependent upon the blood they receive, which is found to diminish or increase in quantity, accord- ing to the degree of inactivity or exertion. Muscles differ, like the primary fibre, at their extremities and centre ; the former being composed of condensed cellular mem- brane, the latter of the muscular or fibrous tissue. The centre of a muscle is usually called its venter or belly, and the cellular tex- ture at the extremities is variously termed ; — the part from which it appears to arise, being called the head ox origin; and that, into which it is inserted, the tail, termination or insertion. These terms are not sufficiently discriminative. We shall find, that a muscle is capable of acting in both directions, so that the head and the tail — the origin and insertion — may reciprocally change places. In ordinary language, however, the extremity at which the albugineous tissue, (if we adopt Chaussier's nomenclature,) assumes a rounded form, so as to constitute a cord or tendon, is called the insertion. When this tissue is expanded into a mem- brane, it is termed an aponeurosis : and in this state it exists at the head or origin of the muscle ; so that by tendon and aponeu- rosis the muscles are inserted into the parts, which they are de- stined to move, if we except those that are inserted into the skin. Muscles are divided into simple and compound. The simple axe those whose fibres have a similar course and arrangement. They may be either flat or ventriform, or radiated or penniform. The compound arise from different parts; their origins are, conse- quently, by distinct fasciculi, or they may terminate by distinct insertions. Fig. 71, which is a representation of the biceps — a flexor muscle of the forearm — is one of these. It has, as its a Anat. General, torn. ii. 334 MUSCULAR MOTION. name imports, two heads running into one belly. It is, also, an example of the ventriform muscle. Fig. 71. Compound Ventriform Muscle. In the pectoralis major, Fig. 72, we have an example of the radiated muscle, or of one in which the fibres converge towards their tendinous insertion. Double Penniform Muscle. They are, again, partitioned into the long, broad, and short. The long muscles are situate chiefly on the limbs, and are concerned in locomotion. The broad generally form the parietes of cavities: they are not so much enveloped as the long muscles by strong fibrous aponeuroses or fasciae, owing to their being obviously less liable to displacement; and the short muscles are situate in parts, where considerable force is required, and but little motion; so that their fibres are very numerous and short. The number of muscles of course varies in different animals; and is in proportion to the extent and variety of motion they are called upon to execute. In man, the number is differently esti- mated by anatomists; some describing several distinct muscles under one name; and others dividing into many what ought to belong to one. According to the arrangement of Chaussier, three hundred and sixty-eight distinct muscles are admitted; but others reckon as many as four hundred and fifty. MUSCLES CONVERTED INTO ADIPOCIRE. 335 When muscles are subjected to analysis, they are found to con- sist of fibrin ; osmazome ; jelly ; albumen ; phosphates of soda, ammonia and lime ; carbonate of lime ; chloride of sodium, phos- phate, and lactate of soda; and, according to Fourcroy and Vau- quelin,8 sulphur and potassa are present. The great constituents ofthe pure muscular tissue are,—fibrin, and probably osmazome; — the gelatin, which is met with, being ascribable to the cellular membrane that envelopes the muscular fibres and lacerti. The membranous structures of young animals contain a much greater quantity of jelly than those ofthe adult; and it is probably on this account, that the flesh ofthe former is more gelatinous ; — not be- cause the muscular fibre contains more gelatin. Thenard assigns the muscles, on final analysis, the following constituents : —fibrin, albumen, osmazome, fat, substances capable of passing to the state of gelatin, acid (lactic), and different salts. They have likewise been analyzed by Berzelius and Braconnot.b It must be borne in mind, however, as Raspailc has properly remarked, that all these are the results of the analysis of the muscle, as we meet with it. The analysis of the muscular fibre has yet to be accomplished. In this, too, and every analogous case, the analysis only affords us evidence of the constituents of the dead animal matter; and some of the products may even have been formed by the new affinities, resulting from the operations of the analyst. They can afford but an imperfect judgment of the constitution of the living substance. The muscular structure is liable to a singular kind of conversion, under particular circumstances, to which it may be well to advert. When, about the latter part ofthe last century, it was determined, for purposes of salubrity, to remove the bodies from the churchyard of Les Innocens at Parisd — which had been the cemetery for a considerable part of the population of Paris for centuries — the whole area, occupying about seven thousand square yards, was found converted into a mass, consisting chiefly of animal matter, and raising the soil several feet above the natural level. On open- ing the ground, to remove the prodigious collection of dead bodies, they were found to be strangely altered in their nature and ap- pearance. What had constituted the soft parts of the body was converted into an unctuous matter, of a gray colour, and of a pecu- liar, but not highly offensive, smell. According to their position in the pits, — for the bodies were deposited in pits or trenches, about thirty feet deep, each capable of holding from twelve hundred to fifteen hundred bodies, — and according to the length of time they had been deposited, this transformation had occurred to a greater or less extent. It was found to be most complete in those bodies, which were nearest the centre of the pits, and when they * Annales de Chimie, lvi. 43. b Muller's Handbuch der Physiologie, Baly's translation, P. i. p. 369, Lond. 1837 ; and Dr. T. Thomson, Chemistry of Animal Bodies, p. 273, Edinb. 1843. * Op. citat. p. 214. « Thouret, Journal de Physique, xxxviii. 255. 336 MUSCULAR MOTION. had been buried about three years. In such case, every part, ex- cept the bones, the hair, and the nails, seemed to have lost all its properties, and to be converted into this gras des cimetilres, which was found to be a saponaceous compound, consisting of ammonia, united to adipocire,— a substance, as its name imports, possessing properties intermediate between those of fat and wax. When the adipocire was freed from the ammonia, and obtained in a state of purity, it was found to resemble strongly spermaceti, both in phy- sical and chemical qualities. It was afterwards discovered, that the conversion of muscular flesh into adipocire might be caused by other means. Simple immersion in cold water, especially in a running stream, was found by Dr. Gibbesa to produce the conver- sion more speedily than inhumation. It can be caused, too, still more rapidly by the action of dilute nitric acid. The chemical is not the only interest attached to this substance. It has been adduced in a court of justice, for the purpose of enabling some judgment to be formed regarding the period that a body may have been immersed in the water. It is probable that this must differ greatly according to various circumstances; — the time that has elapsed between the death of the individual, and the period of immersion ; the conditions of the fluid as to rest or motion, tem- perature, &c.; and the temperature of the atmosphere ; so that any attempt to fix a period for such conversion must be liable to much inconclusiveness. Yet the opinion of a medical practitioner, on this subject, has been the foundation of a juridical decision. At the Lent" assizes, holden at Warwick, England, in the year 1805, the fol- lowing case came before the court. A gentleman, who was in- solvent, left his home with the intention,—as was presumed from his previous conduct and conversation, — of destroying him- self. Five weeks and four days after that period, his body was found floating down a river. The face was disfigured by putre- faction, and the hair separated from the scalp by the slightest pull; but the other parts of the body were firm and white, with- out any putrefactive appearance. On examining the body, it was found that several parts of it were converted into adipocire. A commission of bankruptcy having been taken out against the de- ceased a few days after he left home, it became an important question to the interest of his family, to ascertain whether or not he were living at that period. From the changes sustained by the body, it was presumed that he had drowned himself on the day he left home ; and to corroborate the presumption, the evidence of Dr. Gibbes was requested, who, from his experiments on this sub- ject, it was thought, was better acquainted with it than any other person. Dr. Gibbes stated on the trial, that he had procured a small quantity of this fatty matter, by immersing the muscular parts of animals in water for a month, and that it required five or six weeks to make it in any large quantity. Upon this evidence, the jury were of opinion that the deceased was not alive at the » Philosophical Transactions for 1794 and 1795. BONES. 337 time the commission was taken out, and the bankruptcy was ac- cordingly superseded !a 3. OF THE BONES. The bones are the hardest parts of the animal frame ; and, con- sequently, serve as a base of support and attachment to the soft parts. They constitute the framework ofthe body, and determine its general shape. The principal functions they fulfil are, — to form defensive cavities for the most important organs ofthe body — the encephalon, spinal marrow, &c. — and to act as so many levers for transmitting the weight of the body to the soil, and for the different locomotive and partial movements. To them are attached the different muscles, concerned in those functions. In man and the higher classes of animals, the bones are, as a general rule, within the body; his skeleton is, consequently, said to be internal. In the Crustacea, the testaceous mollusca, and in certain insects, the skeleton is external, the whole of the soft parts being contained within it. The lobster and crab are familiar instances of this arrangement. The stature of the human skeleton is various, and may be taken, on the average, perhaps, — in those of European descent, — at about five feet eight or nine inches.b We find, however, examples of considerable variation from this average. A skeleton of an Irish giant, in the museum of the Royal College of Surgeons of London, .measures eight feet four inches. On the other hand, Bebe, the dwarf of Stanislaus, king of Poland, was only thirty-three inches high ; and a Polish nobleman, Borwlaski, measured twenty-eight French inches. He had a sister, whose height was twenty-one inches.0 The bones may be divided into the short, broad ox flat, and long. The short bones are met with in parts of the body, which require to be both solid and moveable:—in the hands and feet,for example, and in the spine. The flat or broad bones form the parietes of cavi- ties, and they aid materially in the movements and attitudes, by affording an extensive surface for the attachment of muscle. The long bones are chiefly intended for locomotion, and are met with only in the extremities. The shape of the body, or shaft, and of the extremities merits attention. The shaft or middle por- tion is the smallest in diameter, and is usually cylindrical. The extremities, on the other hand, are expanded; a circumstance, which not only adds to the solidity of the articulations, but dimi- nishes the obliquity of the insertion of the tendons, passing over them, into the bones. In their interior is a medullary canal or cavity, which contains the medulla, marrow or pith : — a secre- tion, whose office will be a theme for after inquiry. One great a Male's Epitome of Forensic Medicine, in Cowper's Tracts on Medical Jurispru- dence, Philad. 1819; Beck's Medical Jurisprudence, 5th edit. ii. 164 ; also, Devergie, in Annales d'Hygiene Publiuue, 1829. b See Quetelet, Sur l'Homme, &c, Paris, 1835; and Prof. Forbes, in Lond. and Edinb. Philos. Magaz., March, 1837, p. 197. c Lectures on Physiology, Zoology, &c, by W. Lawrence, p. 434, Lond. 1819. VOL. I.— 29 338 MUSCULAR MOTION. advantage of this canal is, that it makes the bone a hollow cylin- der, and thus diminishes its weight. On many of the bones, prominences and cavities are perceptible. The eminences bear the generic name of apophyses ox processes. Their great use is, to cause the tendons of muscles to be inserted at a much greater angle into the bones they have to move. It may be seen hereafter, that the nearer such insertion is to the perpendicular to the lever, the greater will be the effect produced. The cavities are of various kinds. Some are articular : others for the insertion, reception, or transmission of parts. Those of insertion and reception afford space for the attachment of muscles ; those of transmission, &c, are frequently incrusted with cartilage, converted into canals by means of ligament, and furnished with a synovial membrane, which lubricates them, and facilitates the play of the tendons, for the passage of which they are destined. The mechanical structure of bone is a laminated framework, in- crusted by an earthy substance, and penetrated by exhalant and absorbent vessels, arteries, veins, and nerves. Herissant,a appears to have been one of the first who stated, that bone is essentially composed of two substances:—the one a cartilaginous basis or parenchyma, giving form to the part, — the other a peculiar earthy matter deposited in this basis, and communicating to it its hardness. These two constituents can be readily demonstrated ; the first, by digesting the bone in dilute muriatic acid, which dissolves the earthy part, without acting on the animal matter; and the second, by. burning the bone, until all the animal matter is consumed, whilst the earthy part is left untouched. If we take a long bone and divide it longitudinally, we find, that it is composed of three different substances, all of which may, how- ever, be regarded as the same osseous tissue, in various degrees of condensation. These are, — the hard or compact substance, the spongy or areolar, and the reticulated. The first is in the most condensed form ; it exists at the exterior of the bone, and consti- tutes almost the whole of the shaft. The second is seen towards the extremities of the long bone, and in almost the whole of the short bones. In it, the laminse are less close, and have a cancel- lated appearance, — the cellules bearing the name of cancelli. The reticulated substance is a still looser formation ; the laminae being situate at a considerable distance, and the space betwe^a filled up with a series of membranous cells, which lodge the marrow. The marginal figures on the next page represent a longitudinal and a transverse section of the same bone in which this arrangement is well exhibited. We have seen the advantages of the expanded extremities of long bones, as regards the insertion of muscles ; but it is obvious, that if these portions ofthe bone had consisted of the heavy com- pact tissue, the increased weight of the limbs would have destroyed the advantages, which would otherwise have accrued ; whilst, if the shaft of the bone, exposed, as it is, to external violence, haa * Memoir, dc l'Academ. des Sciences de Paris, p. 322, pour 1758. BONES. 339 consisted of the spongy tissue only, it would not have been able to offer the necessary resistance. It is, therefore, formed almost en- tirely of the compact tissue ; so that a section of one inch in height, taken from the body of the bone, will not differ essentially in weight from Fis- 74- an inch taken from the extremity. Nor does the cavity, within the bones, diminish their strength as might be at first sight presumed. By enlarging the circumference, the contrary effect is produced ; for we shall see, in the mechanical proem to the particular movements, that of two hollow co- lumns, formed of an equal quantity of matter and of the same height, that, which has the larger cavity, is actually the stronger. A very important use of the cancellated or spongy texture of the bones was suggested by a dis- tinguished individual of this country, to whom surgical science,inparticular, has been so largely indebted. Dr. Physicka asserts, that it serves to dimi- nish, and, in many cases, to prevent, concussion of the brain, and of the other viscera, in falls and blows. The sections of a Bone. demonstration, Which he gives Of 1-2. Longitudinal section ofthe extremity. ,. . . , , ..■ /■ ^ -r^ 3. Transverse section of the body. this, is simple and satisfactory. If we suspend a series of six ivory balls by threads; raise the ball at one extremity, and allow it to fall on the next to it, we find, that the farthest ball in the series is impelled to a distance, which corresponds with the momentum communicated by the first ball to the second. But if we substitute, for the middle ball of the series, a ball made ofthe cellular structure of bone, we find that almost the whole of the momentum is lost in this osseous structure; espe- cially, if it be previously filled with tallow or well soaked in water, so as to bring it to a closer approximation to the natural living condition. Bones consist of earthy salts and animal matter intimately blended. The latter is chiefly cartilage, gelatin, and the peculiar fatty matter — the marrow. On reducing bones to powder and digesting them in water, the fat rises and swims upon the surface, and the gelatin is dissolved. According to the analysis of Berze- lius, 102 parts of dry human bones consist of animal matter, 33-3 ; phosphate of lime, 51-04, carbonate of lime, 11-30; fluoride of calcium, 2 ; phosphate of magnesia, 1-16 ; soda, chloride of sodium, and water, 1-2. Dr. Reesb likewise detected fluoride of calcium, a Horner's Special and General Anatomy, 5th edit.. Philad. 1843. b Medico-Chirurgical Transactions, vol. xxi.; see, also, Dr. T. Thomson, Chemistry of Animal Bodies, p. 239, Edinb. 1843. 340 MUSCULAR MOTION. but it was not uniformly present. Fourcroy and Vauquelin, how- ever, did not discover any fluoric acid, but they found oxides of iron and manganese, silica, and albumen. Hatchett detected, also, a small quantity of sulphate of lime. Schregera gives the following as the proportions of the animal and earthy parts of bone : IJfFAIfTS. ADULTS. AGED. Animal matter - - - 47-20 20-18 12-20 Earthy matter - - - 48-48 74-84 84-10 95-68 95-02 96-30 The bones are enveloped by a dense fibrous membrane, termed, in the abstxact,periosteum, but assuming different names according to the part it covers. On the skull, it is called pericranium : and its extensions over the cartilages of prolongation, are called peri- chondrium. The chief uses of this expansion are, to support the vessels in their passage to and from the bone, and to assist in its formation ; for we find, that if the periosteum be removed from a bone, it becomes dead at the surface previously covered by the mem- brane,and exfoliates. In the foetus, it adds materially to the strength of the bone, prior to the completion of ossification. In the long bones, ossification commences at particular points ; one generally in the shaft, and others at the different .articular and other processes. These ossified portions are, for some time, separated from each other by the animal matter, which alone composes the intermediate portions ofthe bone; and, without this fibrous envelope, they would be too feeble perhaps to resist the strains to which they are exposed. The periosteum, moreover, affords a convenient insertion for the muscles destined to act upon the bones ; and enables them to slide more readily when in action ; hence friction is avoided. The cavity of long bones is lined by a membrane — called the medullary membrane or internal periosteum — which is supplied with numerous vessels, adheres to the internal surface of the bone, and is not only concerned in its nutrition, but also in the secretion of the marrow, — and likewise of a kind of oily matter, which dif- fers from marrow merely in being more fluid, and is contained in the cells formed by the spongy substance, and in the areolae ofthe compact substance. This is called the oil of bones. The marrow is considered to be lodged in membranous cells, formed by an extension of the internal periosteum; whilst, accord- ing to Howship,b the oil of bones is probably deposited in longitu- dinal canals, which pass through the solid substance ofthe bone, and through which its vessels are transmitted. The nature and fancied uses of the marrow and of the oil of bones will be considered in another part. . The bones, periosteum, and marrow are, in the sound state, * See, on the Histology of Bone, Miescher de Ossium Genesi, Structura et Vita, Dissert. Anat. Phys. Inaugural, p. 47, Berol. 1836 ; Purkinje and Deutsch, De Peni- tiori Ossium Structura, Vratisl. 1834; and Dublin Journal of Med. Science, Sept. 1836; E. Wilson, Anatomist's Vade Mecum, Amer. Edit, by Dr. Goddard, p. 19, Philad. 1843; Mr. Paget, Brit, and For. Med. Rev., July, 1842, p. 268 ; and Todd and Bowman, Physiological Anatomy and Physiology of Man, p. 97, Lond, 1843. b Medico-Chirurg. Transact, vii. 393. ANALYSIS OF BONES. 341 amongst the insensible parts of the frame. They are certainly not sensible to ordinary irritants; but, when morbid, they exhibit in- tense sensibility. This, at least, applies to the bones and perios- teum ; the sensibility, which has been ascribed to the marrow, in disease, being probably owing to that of the prolongations of the membrane, in which it is contained. The number of the bones in the body is usually estimated at two hundred and forty, exclusive of the sesamoid bones, which are always found in pairs at the roots of the thumb and great toe, be- tween the tendons of the flexor muscles and joints,and, occasionally, at the roots of the fingers and small toes. The bones are connected by means of articulations, or joints, which differ materially from each other. To all the varieties, names are appropriated, which form a difficult task for the memory of the anatomical student. Technically, every part at which two bones meet and are connected is called an articulation, whether any degree of motion be permissible or not. This, indeed, is the foundation of the division that prevails at the present day, — the articulations being separable into two classes ; the immoveable or synarthroses ; and the moveable or diarthroses. The synarthroses are variously termed, according to their shape. When the articular surfaces are dovetailed into each other, the joint is called a suture. This is the articulation that prevails between the bones of the skull. Harmony is when the edges ofthe bones are even, and merely touch, as in the bones of the head in quadrupeds and birds. When a pit in one bones receives the projecting extremity of another, we have a case of gomphosis. It is exhibited in the union between the teeth and their sockets. Lastly, schindylesis is when the lamina of one bone is received into a groove of another; as in the articulation of the vomer, which separates the nasal fossae from each other. The moveable articulations comprise two orders: — the amphiarthroses, in which the two bones are intimately united by an intermediate substance, of a soft and flexible character, as in the junction of the vertebrae with each other; and the diar- throses, properly so called. The last admit of three subdivisions — the enarthroses, or ball and socket joints; the condyloid, in which, owing to the head being oval, the movements are not as easy in all directions as when it is spherical; and the ginglymoid or ginglymus, in which the motion can occur in only one direction as in a hinge. The farther subdivision of the joints belongs more to anatomy than physiology. The articular surfaces of the bones never come into immediate contact. They are tipped with a firm, highly elastic substance, called cartilage; which, by its smoothness, enables the bones to move easily upon each other, and may have some influence in deadening shocks, and defending the bones, which it covers. The arrangement of the cartilage varies according to the shape of the extremity ofthe bone. If it be spherical, the cartilage is thick at the centre, and gradually diminishes towards the circumference. 29* 342 MUSCULAR MOTION. In the cavity the reverse is the case ; the cartilage is thin at the centre, and becomes thicker towards the circumference ; and on a trochlea or pully, its thickness is nearly every where alike. An admirable provision against displacement of the bones at the articulations exists in the ligaments. These, by the French anato- mists, are distinguished into two kinds —the fibrous capsules, and the ligaments properly so called. The former are a kind of cylindrical sac, formed of a firm, fibrous membrane ; open at each extremity, by which they closely embrace the articular end ofthe bones; and loose, when the joint admits of much motion. In this way, the articulation is completely enclosed ; they generally bear the name of capsular ligaments. The ligaments, properly so called, are bands of the same kind of tissue, which extend from one bone to another; by their resistance preserving the bones in situ.; and by their suppleness admitting of the necessary motion. The interior of all these articulations is lubricated by a viscid fluid, called synovia. This is secreted by a peculiar membrane of a serous nature ; and its use is to diminish friction, and, at the same time, to favour adhesion. The mode in which it is secreted, and its chief properties and uses, will be the subject of future inquiry. In certain ofthe moveable articulations, fibro-cartilaginous sub- stances, frequently called interarticular cartilages, are found be- tween the articular surfaces, and not adherent to either of them. These have been supposed to form a kind of cushion, which, by yielding to pressure, and returning upon themselves, may thus protect the joints to which they belong; and, accordingly, it is as- serted, that they are met with in the joints, which have to sustain the greatest pressure ; but Magendiea properly remarks, that they do not exist in the hip-joint, or in the ankle-joint, which have con- stantly to support the strongest pressure. The use, which he suggests, is more specious; — that they may favour the extent of motion, and prevent displacement. The stability of the joints is likewise aided by the manner in which the muscles or tendons pass over them. These are con- tained in an aponeurotic sheath, to prevent their displacement; and thus the whole limb becomes well protected, and dislocation infrequent, even in those joints, as that of the shoulder, which, as regards their osseous arrangement, ought to be very liable to dis- placement. It has been suggested by Weber, that the head of the thighbone is retained in situ, not by the power of the muscles or ligaments, but by the pressure of the surrounding atmosphere ; and Lauer,b who repeated Weber's experiments under the directions of Fricke, of Hamburg, is of opinion, that the pressure of the atmosphere must be classed among the means by which the lower extremity is kept in apposition with the trunk ofthe body. 1 Precis Elementaire, 2de edit. i. 292, Paris, 1823. b Zeitschrift fur die gesammte Medicin, Band ii. Heft 3. PHYSIOLOGY OF MUSCULAR MOTION. 343 4. PHYSIOLOGY OF MUSCULAR MOTION. By voluntary motion, or that which is effected by the muscular system of animal life, we mean a contraction of the muscles under the influence of volition or the will. This influence is propagated along the nerves to the muscles, which are excited by it to con- traction. The encephalon, spinal marrow, nerves, and muscles are, therefore, the organs of voluntary contraction. Volition is one of the functions of the encephalon, and might have been, with much propriety, included under the physiology of the intellectual and moral acts; but as it is so intimately concerned with muscular motion, it was judged advisable to defer its consi- deration until the present occasion. That it is a product of ence- phalic action is proved by many facts. If the brain be injured in any manner ; — by fracture of the skull, for example, or by effu- sion of blood, producing apoplectic pressure on some part of it; — or if it be deprived of its functions by the use of a strong dose of any narcotic substance ; — or if, again, it be in a state of rest, as in sleep : — volition is no longer exerted, and voluntary motion is impracticable. This is the cause why the erect attitude cannot be maintained during sleep ; and why the head falls forward upon the chest, when the somnolency is to such an extent as to deprive the extensor muscles of the back and head of their stimulus to activity.a That an emanation from the encephalon is necessary is likewise proved by the effect of tying, cutting, compressing, or stupifying the nerve proceeding to a muscle ; it matters not that the will may act; the muscle does not receive the excitation,and no motion is produced; a fact which proves, that the nerves are the channels of communication between the brain and the muscles. If, again, we destroy the medulla oblongata and medulla spinalis, we abolish all muscular motion, notwithstanding the brain may will, and the muscles be in a state of physical integrity ; because we have destroyed the parts whence the nerves proceed. In like manner, by successively slicing away the medulla spinalis from its base to the occiput, we paralyse, in succession, every muscle of the body, which receives its nerves from the spinal marrow. Experiments of different physiologists have confirmed the view, that the encephalon is the chief seat of volition. When it has been sliced away to a certain extent, the animal has been thrown into a state of stupor, attended with the loss of sensibility, of the power of locomotion, and especially of spontaneous motion; and in writing, dancing, speaking, singing, &c, we have indisputable evidence of its direction by the intellect. It is not so clear, that the seat of volition is entirely restricted to the encephalon. There are many actions of the yet living trunk, which appear to show, that an obscure volition may be exerted, even after the brain has been separated from the rest of the body; and acephalous children » Adelon, art. Encephale (Physiol.) in Diet, de Med. vii. 516, Paris, 1823 ; and Physiol, de l'Homme, ii. 25, 2de edit. Paris, 1829. 344 MUSCULAR MOTION. have not only moved perceptibly when in utero, but at birth. Without referring to the lower classes of animals, which, as we have already had occasion to remark, execute voluntary motions for a long time after they have been bisected, every one must have noticed the motions of decapitated fowls, which will continue for a time, to run and leap, and, apparently, to suffer uneasiness in the incised part. The feats of the Emperor Commodus are elucidative of this matter. Herodian relates, that he was in the habit of shooting at the ostrich, as it ran across the circus, with an arrow having a cutting edge; and, even when the shaft was true to its destination, and the head was severed from the body, the ostrich usually ran several yards before it dropped. Kaauw Boerhaave — nephew of the celebrated Hermann, and himself an eminent medical teacher at St. Petersburg — asserts, that he saw a cock, thus decapitated, run a distance of twenty-three feet afterwards. Some cases are also recorded of men walking a few steps after decapitation, striking their breasts, &c. ; but they can scarcely be regarded as authentic* In those countries where judicial execution consists in decapitation by the sword, sufficient opportunities must have presented themselves for testing this question; but no zealous Xaturforscher appears to have been present to record them. Similar opportunities have likewise occurred under the operations ofthe guillotine. Legallois,b in some experiments, which he instituted, for the purpose -of determining the nervous influence on the heart, &c, found, that rabbits, which he had decapitated and deprived of their hinder extremities, but still kept alive by artificial respiration, moved their fore paws whenever he stimulated them by plucking some of their hairs. With regard to complete acephali, or those foetuses which are totally devoid of encephalon,—although they may vegetate in utero, they quickly expire after birth, owing to their being^devoid of the organs ofthe animal functions, and to the consequent impossibility of respiring. Some monsters have, however, been born without the brain, but with part of the encephalon. These have been called, by way of distinction, anencephali or hemicephali. Where the medulla oblongata exists, they possess the nervous system of the senses, and are, consequently, able to live for some time after birth, and to exert certain muscular movements, such as suckine, moving the limbs, evacuating the excretions. &c. Adelon asserts, that none of these facts ought to shake the proposition, which he embraces,—that in the superior animals, and consequently in man, the medulla spinalis and the nerves are merely the conductors of volition, or of the locomotive will ; and that, in the encephalon alone, volition is produced. His arguments on this point, how- ever,are not characterized by that ingenuousness and freedom from * Adelon, op. citat. ii. 2S : and Dr. J. R. Coxe, in Dunglisun's Amer. Med. Intelii- gencerfor May 15. 1S37. i CEuvres. Paris, 1824. VOLITION SEATED IN THE ENCEPHALON. 345 sophism, for which his physiological disquisitions are generally dis- tinguished. " First of all," he observes, " the fact ofthe progression and motions of men and quadrupeds, after decapitation, is mani- festly apocryphal; and even if we must admit, that certain ani- mals still execute some movements after decapitation, are such movements evidently regular and ordained ? And, supposing them to be so, may not this have arisen from the conformation of the parts, or from habits contracted by the organs ? This last appears to us most probable ; for if, from any cause whatever, the mus- cles of a part contract, they will cause the part to execute such motions as the joints, entering into its composition, require ; and which may, therefore, be similar to those that the will produces." He farther attempts to deny the facts related of the lower classes of animals, and asserts, that " they are not evinced in the experi- ments instituted in our day." The cases, which are adduced to prove the defective sensibility of the lower tribes of animated nature, are, however, incontestable ; — the trunk ofthe wasp will attempt to sting after the head is removed; and the experi- ment, which was made by Dr. Harlan,a in the presence of Capt. Basil Hall, certainly demonstrates something like design in the headless trunk. Our conclusion ought probably to be, from all these cases,— that volition is chiefly seated in the encephalon, but that an obscure volition may, perhaps, originate farther down the cere- bro-spinal axis. This conclusion, of course, applies only to the higher classes of animals; for we have seen, that the polypus is capable of division into several portions, so as to constitute as many distinct beings ; and it is probable that the principal seat of volition may extend much lower down in the inferior tribes. Attempts, and of a successful nature, have been made to dis- cover, whether the whole brain be concerned in volition, or only a part. Portions of the brain have been disorganized by disease, and yet the individual has not been deprived of motion ; at other times, as in paralysis, the faculty has been impaired; and again, considerable quantities of brain have been lost, owing to accidents, (in one case the author knew nineteen tea-spoonfuls,) with equal immunity, as regards the function in question. The experiments, executed on this subject, go still farther to confirm the idea, that volition is not seated exclusively in the encephalon. Rolando and Flourensb performed several, with the view of detecting the seat of the locomotive will; or of that which presides over the general movements of station and progression ; and they fixed upon the cerebral lobes. Animals, from which these were removed, were thrown into a sleepy, lethargic condition ; were devoid of sensation and spontaneous motion, and moved only when provoked. On the other hand, Magendie0 affirms, that the cerebral hemispheres may be cut deeply in different parts of their upper surface, without any evident alteration in the movements. » Medical and Physical Researches, Philad. 1835. b Op. citat. c Precis Elementaire. 346 MUSCULAR MOTION. Even their total removal, if it did not implicate the corpora striata, he found to produce no greater effect; or, at least, none but what might be easily referred to the suffering induced by such an experi- ment. The results, however, are not alike in all the classes of vertebrated animals. Those detailed were observed on qua- drupeds, and particularly on dogs, cats, rabbits, Guinea-pigs, hedge-hogs, and squirrels. In birds, the removal or destruction of the hemispheres — the optic tubercles remaining untouched — was often followed by the state of stupor and immobility, described by Rolando and Flourens ; but, in numerous cases, the birds ran, leaped, and swam, after the hemispheres had been removed, the sight alone appearing to be destroyed. In reptiles and fish, the removal of the hemispheres seemed to exert but little effect upon their motions. Carps swam with agility ; frogs leaped and swam as if uninjured, and the sight did not appear to be affected. Magendiea properly concludes, from these experiments, that the spontaneity of the movements does not belong exclusively to the hemispheres; that in certain birds, as the pigeon, the adult rook, &c, this seems to be the case ; not so in other birds ; but as regards the mammalia, reptiles, and fish, — at least such of them as were the subjects of his experiments, — his conclusion is applicable. Of the nature of the action of the brain, in producing volition, we know nothing. It is only in the prosecution of direct experi- ments upon the organ, that we can have an opportunity of seeing it, during the execution of the function; but the process is too minute to admit of observation. Our knowledge is confined to the fact, that the encephalon does act, and that some influence is pro- jected from it along the muscles, which excites them to action, and accurately regulates the extent and velocity of muscular contrac- tion. Yet volition is not the sole excitant of such contraction. If we irritate any part of the encephalon or spinal marrow, or any of the nerves proceeding from them, we find, that muscular move- ments are excited; but they are not regular, as when under the influence of volition. The whole class of involuntary motions, or rather of those executed by the muscular system of organic life, is of this kind, including the action of many of the most important organs — the heart, intestines, bloodvessels, &c. All the involun- tary muscles equally require a stimulus to excite them into action ; but, as their name imports, they are removed from the influence of volition. In certain diseased conditions, we find, that all the voluntary muscles assume involuntary motions ; but this is owing to the ordinary volition being interfered with, and to some direct or indirect stimulation affecting the parts of the cerebro-spinal axis concerned in muscular contraction ; or, if the effect be local, to some stimulation of the nerve proceeding from the axis to the part. Of this kind of general involuntary contraction of voluntary muscles, we have a common example in the convulsions of chil- dren ; and one of the partial kind, in cramp or spasm. The will, then, is the great but not the sole regulator of the c Ibid. i. p. 336. NERVOUS CENTRE OF MUSCULAR CONTRACTION. 347 supply of voluntary nervous influence. This is confirmed by ex- periment. If a portion of the spinal marrow be divided, so as to separate it from all communication with the encephalon, the mus- cles cannot be affected by the will; but they contract on irritating the part of the spinal marrow, from which the nerves proceed. It has, hence, been presumed, by some physiologists, that volition is only the exciting and regulating cause of the nervous influence ; and that the latter is the immediate agent in producing contraction ; and they affirm, that as, in the sensations, the impression is made on the nerve, and perception is effected in the brain ; so, in mus- cular motion, volition is the act of the encephalon, and the nervous influx corresponds to the act of impression. With regard to the seat of this nervous centre of muscular con- traction, much discrepancy has arisen amongst recent physiolo- gists. It manifestly does not occupy the whole encephalon ; as certain parts of it may be irritated, in the living animal, without exciting convulsions. Parts, again, may be removed without pre- venting the remainder from exciting muscular contraction when irritated. In the experiments of Flourens, the cerebral lobes were removed, yet the animals were susceptible of motion, when stimu- lated ; and, whenever the medulla oblongata was irritated, convul- sions were produced. Its seat is not, therefore, in the whole ence- phalon. Rolando refers it to the cerebellum. He asserts that, on removing the cerebellum of living animals, without implicating any of the other parts of the encephalon, the animals preserved their sensibility and consciousness, but were deprived of the power of motion. This occurred to a greater extent in proportion to the severity ofthe injury inflicted on the cerebellum. If the injury was slight, the loss of power was slight; and conversely. Im- pressed with the resemblance between the cerebellum of birds and the galvanic apparatus ofthe torpedo; and taking into considera- tion the lamellated structure of the cerebellum, which, according to him, resembles a voltaic pile ; and the results of his experiments, which showed, that the movements diminished in proportion to the injury done to the cerebellum, Rolando drew the inference, that this part ofthe encephalon is an electro-motive apparatus, for the secretion of a fluid analogous to the galvanic. This fluid is, according to him, transmitted along the nerves to the muscles, and excites them to contraction. The parts of the encephalon, con- cerned in volition, would, in this view, regulate the quantity in which the motive fluid is secreted, and govern the motions ; whilst the medulla oblongata which, when alone irritated, always occa- sions convulsions, would put the encephalic extremity of the con- ducting nerves in direct or indirect communication with the loco- motive apparatus. This ingenious and simple theory is, however,overthrown by the fact mentioned by Magendie,3 that he is annually in the habit of exhibiting to his class animals deprived of cerebellum, which are 1 Precis, &c. i. 340. 348 MUSCULAR MOTION. still capable of executing very regular movements. For example, he has seen the hedgehog and Guinea-pig, deprived not only of brain but of cerebellum, rub its nose with its paw, when a bottle of strong acetic acid was held to it; and he properly remarks, that a single positive fact of this kind is worth all the negative facts that could be adduced. He farther observes, that there could be no doubt of the entire removal of the brain in his experiments. These experiments of Magendie are equally adverse to the hypothesis of Flourens, that the cerebellum is the regulator or balancer of the movements. Some anatomical observations, however, by Mr. Solly,3 would seem to show, that there is a direct communication between the motor tract of the spinal marrow and the cerebellum. The corpora pyramidalia have been generally supposed to be formed by the entire mass of the anterior or motor columns of the spinal cord, but Mr. Solly shows, that not more than one-half of the anterior column enters into the composition of these bodies; and that another portion, which he terms the " anterolateral co- lumn," when traced on each side in its progress upwards, is found to cross the cord below the corpora olivaria, forming, after mutual decussation, the surface of the corpora restiformia; and ultimately being continuous with the cerebellum. Others, again, have estimated the encephalon to be the sole organ of volition, and have referred the nervous action, which produces the " locomotive influx," as it is termed, exclusively to the spinal marrow ; and hence, they have termed the spinal marrow, and the nerves issuing from it, the " nervous system of locomotion." It is manifest, however, that the encephalon must participate with the medulla spinalis in this function ; inasmuch as not only does direct irritation of several parts of the former excite convulsions, but we see them frequently as a consequence of disease of the ence- phalon ; yet, as has been remarked, there is some reason for be- lieving, that, in the upper classes of animals, an obscure volition may be exercised for a time, even when the encephalon is sepa- rated from the body. It need scarcely be said, that we are as ignorant of the character of this influx, as we are of that of the nervous phenomena in general. The parts of the encephalon and spinal marrow, concerned in muscular motion, are very distinct from those that receive the im- pressions of external bodies. The function of sensibility is com- prised in the medulla oblongata and in the posterior column of the spine, whilst the encephalic organs of muscular motion appear to be the corpora striata, the thalami nervorum opticorum, at their lower part, the crura cerebri, the pons varolii, the peduncles of the cerebellum, the lateral parts of the medulla oblongata, and the an- terior column of the medulla spinalis. This is proved by direct experiment, as will be seen presently; and, in addition to this, pathology furnishes us with numerous examples of their distinct- ness. In various cases of hemiplegia or palsy of one side of the a Transactions ofthe Royal Society for 1836 ; and Solly on the Brain, Lond. 1836. NERVOUS CENTRE OF MUSCULAR CONTRACTION. 349 body, — which is of an encephalic character, — we find motion al- most lost, yet the sensibility slightly or not at all affected; and, on the other hand, instances of loss of sensation have been met with, in which the power of voluntary motion has continued. The recent discoveries in the system of vertebral nerves exhibit clearly how this may happen ; and that a considerable space may exist between the roots of a nerve, one of which shall be destined for sensation, the other for motion; yet both may pass out enveloped in one sheath ; — the same nervous cord thus conveying the two irradia- tions, if they may be so termed. According to Sir Charles Bell's system (p. 64), the spinal column is divided into three tracts ; the anterior for motion ; the posterior for sensibility; and the two are kept separate and united by the third—the column for respiration. The experiments performed of late years, — by the French phy- siologists especially, — for the purpose of discovering the precise parts of the encephalon concerned in muscular motion, have at- tracted great and absorbing interest. We wish it could be said, that the results have been such as to afford determinate notions on the subject. According to those of Flourens, the cerebral lobes preside over volition, and the medulla oblongata over the locomotive in- flux ; to the latter organ he assigns, also, sensibility. We have seen, that the results of his experiments have been contested, and with them, of course, his deductions. The facts and arguments, which we have stated, will have shown, too, that the last proposi- tion is alone correct — which refers sensibility to the medulla ob- longata ; and even it is not restricted to that organ, or group of organs — whichsoever it may be considered. MM. Foville and Pinel Grand-Champa have affirmed, that the cerebellum is the seat of sensibility. To this conclusion they were led by the remarks they had made, in the course of their practice, that the cases of paralysis of sensibility, which fell under their notice, succeeded more especially to morbid conditions of the en- cephalon. In this view they conceive themselves supported by the discovery of columns in the spinal marrow destined for parti- cular functions; and, as the posterior column is found to be the column of sensibility, and the cerebellum seems to be formed from this column, they think if ought to be possessed of the same functions. Adelonb remarks, that Willis professed a similar notion, and that he considered the cerebral lobes to be the point of depar- ture for the movements, and the cerebellum the seat of sensibility. In his first volume, however, he had cited, more correctly, the views of Willis. " Willis says positively," he remarks, " that the corpora striata are the seat of perception ; the medullary mass of the brain, that of memory and imagination ; the corpus callosum, that of reflection ; and the cerebellum, the source of the motive spirits." Willis, in truth, regarded the cerebellum as supplying animal spirits to the nerves of involuntary functions, as the heart, intestinal canal, &c. The opinions of Foville and Pinel Grand- Champ are, however, subverted by the experiments of Rolando, 1 Sur le Systeme Nerveux, Paris, 1820. b Op. citat. ii. 38. VOL. I. — 30 350 MUSCULAR MOTION. Flourens, and Magendie, which show,that sensation continues, not- withstanding serious injury to, and even entire removal of, the cere- bellum. By other physiologists, the two functions have been assigned re- spectively to the cineritious and medullary parts of the brain; some asserting, that the seat of sensibility is more especially in the latter, and the motive force in the former. According to Treviranus, the more medullary matter an animal has in its brain and spinal marrow, in proportion to the cineritious, the greater will be its sensibility. To this, however, M. Desmoulins3 properly objects, that in many animals, the spinal marrow is composed exclusively of medullary matter ; and consequently they ought not only to be the most sensible of all, but to be wholly devoid of the power of motion. Others, again, as MM. Foville and Pinel Grand-Champ have reversed the matter; assigning sensibility to the cineritious substance, and motility to the medullary. From those conflicting opinions, it is obviously impossible to sift anything categorical; except that we are ignorant of the special seat of these functions. A part of the discrepancy, in the results, must be ascribed to or- ganic differences in the animals which were the subjects of the experiments. This was strikingly exemplified in those instituted by Magendie, which have been cited. Similar contrariety exists in the experiments and hypotheses, regarding the particular parts of the encephalon, that are concerned in determinate movements of the body. The results of many of those are, indeed, so strange, that did they not rest on such eminent authority, they might be classed among the romantic. It has been already remarked, that Rolando considered the cere- bellum to be an electro-motive apparatus, producing the whole of the galvanic fluid necessary for the motions. Flourens, on the other hand, from similar experiments, independently performed, and without any knowledge of those of Rolando, affirmed it to be the regulator and balancer of the locomotive movements ; and he asserted, that, when removed from an animal, it could neither maintain the erect attitude, nor execute any movement of loco- motion ; nor, although possessing all its sensations, could it fly from the danger it saw menacing- it. The same view has been advocated by Bouillaud, who has detailed eighteen experiments, in which he cauterized the cerebellum, and found that, in all, the functions of equilibration and progression were disordered. The experiments of Magendieb on this subject, are pregnant with im- portant novelty. We have already referred to those that concern the cerebral hemispheres and cerebellum, as the encephalic organs of the general movements, in the mode suggested by Rolando and Flourens, and others. Magendie affirms, in addition, " that there exist, in the brain, four spontaneous impulses or forces, which are situate at the extremity of two lines, cutting each other at right an- gles; the one impelling forwards; the second backwards; the third 1 Anatomie des Systemes Nerveux, &c, Paris, 1825. b Op. citat. i. 345. See, also, Nonat, Gazette Medicale, October 19. 1839. NERVOUS CENTRE OF MUSCULAR CONTRACTION. 351 from right to left, causing the body to rotate; and the fourth from left to right, occasioning a similar movement of rotation." The first of these impulses he fixes in the cerebellum and medulla oblon- gata ; the second in the corpora striata ; and the third and fourth in each of the peduncles of the cerebellum. 1. Forward Impulse. — It has often been observed by those who have made experiments on the cerebellum, that injuries of that organ cause the animals to recoil, manifestly against their will. Magendie3 asserts, that he has frequently seen animals, wounded in the cerebellum, make an attempt to advance, but be immediately compelled to run back ; and he says that he kept a duck for eight days, the greater part of whose cerebellum he had removed, which did not move forwards during the whole of that time, except when placed upon water. Pigeons, into whose cere- bella he thrust pins, constantly walked, and flew backwards, for more than a month afterwards. Hence, he concludes, that there exists, either in the cerebellum or medulla oblongata, a force of impulsion, which tends to cause animals to go forward. He thinks it not improbable that this force exists in man; and he states, that Dr. Laurent, of Versailles, exhibited to him, and to the Acadimie Roy ale de Midecine, a young girl, who, in the attacks of a nervous disease, was obliged to recoil so rapidly that she was incapable of avoiding bodies or pits behind her ; and was, consequently, ex- posed to serious falls and bruises. This force, he affirms, only exists in the mammalia and in birds;—certain fish and reptiles, on which he experimented, appearing to be unaffected by the entire loss of the cerebellum. 2. Backward Impulse. — When the corpora striata are removed, Magendieb found, that the animal darted forward with great ra- pidity ; and, if stopped, still maintained the attitude of running. This was particularly remarked in young rabbits; the animal appearing to be impelled forward by an inward and irresistible power ; and passing over obstacles without noticing them. These effects were not found to take place, unless the white, radiated •part of the corpora striata was cut: if the gray matter was alone divided, no modification was produced in the movements. If only- one of the corpora was removed, it remained master of its move- ments, and directed them in different ways; stopping when it chose ; but, immediately after the abstraction of the other, all regu- lating power over the motions appeared to cease, and it was irre- sistibly impelled forwards. In the disease ofthe horse, called, by the French, immobility, the animal is often capable of walking, trotting, and galloping forward with rapidity; but he does not back; and frequently it is impracticable to arrest his progressive motion. Magendie0 asserts, that he has opened several horses which died in this condition ; and that he found, in all, a collec- tion of fluid in the lateral ventricles, which had produced a morbid change on the surface of the corpora striata, and must have ex- erted a degree of compression upon them. * Precis, i. 341. b Op. cit. i. 337. c Ibid] p. 338. 352 MUSCULAR MOTION. Similar pathological cases appear to occur in man. Magendie relates the case of a person, who became melancholic, and lost all power over his movements; continually executing the most irre- gular and fantastic antics; and frequently compelled to walk ex- clusively forwards or backwards until stopped by some obstacle. In this case, however, the patient got well; and accordingly there was no opportunity for investigating the encephalic cause. M. Itard, also, describes two cases, in which the patients were im- pelled, in paroxysms, to run straight forward, without the power of changing their course, even when a river or precipice was immediately before them. A case is related by M. Piedagnel,3 which is more to the purpose than those just mentioned, inasmuch as an opportunity occurred for post mortem inquiry. The subject of it was, also, irresistibly impelled to constant motion. " At the time of the greatest stupor," says M. Piedagnel, " he suddenly arose ; walked about in an agitated manner ; made several turns in his chamber, and did not stop until he was fatigued. On an- other occasion the room did not satisfy him; he went out, and walked as long as his strength would permit. He remained out about two hours, and was brought back on a litter." M. Piedagnel adds, " that he seemed impelled by an insurmountable force," which kept him in motion, until his powers failed him. On dis- section, several tubercles were found in the right cerebral hemi- sphere, especially at its anterior part; and at the side of the corpora striata. These had produced considerable morbid changes in that hemisphere; and had, at the same time, greatly depressed the left. From these facts, Magendie infers it to be extremely probable, that, in the mammalia and in man, a force of impulsion always exists, which tends to impel them backwards, and which is, consequently, the antagonist to the force seated in the cerebellum. 3. Lateral impulse. — Again, if the peduncles of the cerebellum — the crura cerebelli — be divided in a living animal, it immediate- ly begins to turn round, as if impelled by some considerable force. The rotation or circumgyration is made in the direction of the divided peduncle ; and, at times, with such rapidity, that the ani-' mal makes as many as sixty revolutions in a minute. The same kind of effect is produced by any vertical section of the cerebellum, which implicates from •before to behind the whole substance of the medullary arch, formed by that organ above the fourth ventricle, but the movement is more rapid, the nearer the sec- tion is to the origin of the peduncles; in other words, to their point of junction with the pons varolii. Magendieb affirms, that he has seen this movement continue for eight days without stop- ping, and apparently, without suffering. When any impediment was placed in the way, the motion was arrested ; and, under such circumstances, the animal frequently remained with its paws in the air, and ate in this attitude. What he conceives to have been one » Journal de Physiologie. torn. iii.; and Precis Elementaire, i. 338. b Precis, &c. i. 343. NERVOUS CENTRE OF MUSCULAR CONTRACTION. 353 of his most singular experiments was, — the effect of the division of the cerebellum into two lateral and equal halves: the animal ap- peared to be alternately impelled to the right and left, without re- taining any fixed position: if he made a turn or two on one side, he soon changed his motion and made as many on the other. M. Serres3 — who is well known as a writer on the comparative ana- tomy of the brain, and must have had unusual opportunities for observation at the Hospital La Pitie, to which he is attached — gives the case of an apoplectic, who presented, amongst other symp- toms, the singular phenomenon of turning round, like the animals in the experiments just described ; and, on dissection, an apoplec- tic effusion was found in this part ofthe encephalon. On dividing the pons varolii vertically, from before to behind, Magendieb found, that the same rotary movement was produced : when the section was to the left of the median line, the rotation was to the left, and conversely; but he could never succeed in making the section accurately on the median line. From these facts he concludes, that there are two forces, which are equilibrious by passing across the circle formed by the pons varolii and cere- bellum. To put this beyond all question, he cut one peduncle, when the animal immediately rolled in one direction; but on cutting the other, or the one on the opposite side, the movement ceased, and the animal lost the power of keeping itself erect, and of walking. From the results of all his experiments, Magendie infers, that an animal is a kind of automatic machine, wound up for the perform- ance of certain motions, but incapable of producing any other. The marginal figure of the base of the brain will explain,more di- rectly, the impulses descri- bed by that physiologist. The corpora striata are situate in each hemisphere, but their united impulses may be represented by the arrow A ; the impulse seat- ed in the cerebell um, by the arrow B; and those in each peduncle of the cerebellum, p,p, by the arrows C and D respectively. When the impulse backwards is from any cause destroyed, the animal is given up to the forward impulse, or to that represented by the arrow DirectionofEncePha,icImPulses. according to Magendie. a Magondie's Journ. de Physiol, iv. 405. •> Precis, &c. p. 344. 30* 354 MUSCULAR MOTION. B, and conversely. In like manner, the destruction of one lateral impulse leaves the other without an antagonist, and the animal moves in the direction of the arrow placed over the seat of the impulsion that remains. In a state of health, all these impulsions being nicely antagonized, they are subjected to the influence of volition ; but in disease they may, as we have seen, be so modified as to be entirely withdrawn from its control. These four are not the only movements excited by particular injuries done to the nervous system. Magendie3 states, that a cir- cular movement, to the right or left, similar to that of horses in a circus, was caused by the division of the medulla oblongata, to the outer side ofthe corpora pyramidalia anteriora. When the section was made on the right side, the animal turned, in this fashion, to the right; and to the left, if it was made on that side. Pathology has, likewise, indicated the brain as the seat of differ- ent bodily movements. Diseases of the encephalon have been found not only to cause irregular movements or convulsions, but, also, paralysis of a part of the body, leaving the rest untouched. Hence it has been concluded, that every motion of every part has its commencing point in some portion of the brain. The ancients were well aware, that in cases of hemiplegia the encephalic cause ofthe affection is found in the opposite hemisphere. Attempts have accordingly been made to decide upon the precise part of the encephalon, where the decussation takes place. Many have conceived it to. be in the commissures; but the greater number, perhaps, have referred it to the corpora pyramidalia. These, the researches of Gall and Spurzheimb had pointed out as decussating at the anterior surface of the marrow,6 and as being apparently continuous with the radiated fibres ofthe corpora striata ; and an opinion has prevailed, that the paralysis is ofthe same side as the encephalic affection or of the opposite, according as the affected partof the brain is a continuation of fasciculi, which do not decus- sate— of the corpora olivaria, for example — or of the corpora pyramidalia, which do. Serres,d however, affirms, that affections of the cerebellum, pons varolii, and the tubercula quadrigemina, exert their effects upon the opposite side of the body, and he sup- ports his opinion by pathological cases and direct experiment. Magendie,e again, divided one pyramid from the fourth ventricle ; yet no sensible effect was produced on the movements; certainly there was no paralysis, either on the affected side or on the oppo- site : more than this, he divided both pyramids about the middle, and no apparent derangement occurred in the motions; a slight difficulty in progression being alone observable. The section of the posterior pyramids was equally devoid of perceptible influence on the general movements; and to cause paralysis of one half the body, it was necessary to divide the half of the medulla oblongata, » Ibid. p. 345. b Recherches Sur le Systeme Nerveux, &c, sect, vi., Paris, 1809. <= See, also, Berard, Chassaignac, and Montault, in Archives Generates de Medecine, Ffivrier, 1835. a Anatomie Comparee du Cerveau, Paris, 1824. « Ibid. p. 347.' ENCEPHALOID SEAT OF MUSCULAR MOTION. 355 and then the corresponding side became — not immoveable, for it was affected by irregular movements; and not insensible, for the animal moved its limbs when they were pinched, — but incapable, of executing the determinations ofthe will. These views are not exactly in accordance with the general idea, that disease, confined to one hemisphere of the brain, or cerebellum, and to one side ofthe mesial plane in the tuber'annu- lare, constantly affects the opposite side, whilst disease, confined to one of the lateral columns of the medulla oblongata and medulla spinalis, affects the corresponding side ofthe muscular system : — the encephalon having a crossed, — the medulla a direct ef- fect.3 The crossing of the fibres at the anterior surface of the marrow would not, however, account for the loss of sensation in hemiplegia. Mr. Hiltonb has more recently examined carefully the continuation upwards ofthe anterior and posterior columns of the spinal marrow into the medulla oblongata, and found, that the de- cussation at the upper part of the spinal marrow belonged in part to the column for motion, and in part to the column for sen- sation ; and farther, that the decussation is only partial with re- spect to either of these columns. The result of the examination of morbid cases has induced some physiologists to proceed still farther in their location of the encephalic organs of muscular motion; and to attempt an ex- planation of paraplegia, or of those cases, in which one half the body, under the transverse bisection, is paralysed. MM. Serres, Foville, and Pinal Grand-Champ assert, that the anterior radiated portion ofthe corpora striata presides over the movements of the lower limbs ; and the optic thalamus over those of the upper; and that according as the extravasation of blood, in a case of apoplexy, occurs in one of these parts, or in all, the paralysis is confined to the lower or to the upper limbs, or extends to the whole body. In 1768, Saucerottec presented a prize memoir to the Academic Royale de Chirurgie, of Paris, in which a similar view was ex- pressed. He had concluded, from experiments, that affections of the anterior parts of the encephalon paralysed the lower limbs, whilst those ofthe posterior parts paralysed the upper. M. Cho- part, — in a prize essay, crowned in 1769, and contained in the same volume with the last—refers to the result of some experi- ments by M. Petit, of Namur; which appeared to show, that para- lysis of the opposite half of the body was not induced by injury of the cerebral hemisphere, unless the corpora striata were cut or removed. The experiments by Saucerotte were repeated by M. Foville, and are detailed in a memoir, crowned by the Academie Royale de Medecine, of Paris, in 1826. They were attended with like results. In cats and rabbits, he cauterized, in some, the ante- » See Lectures on the Nervous System and its Diseases, by Marshall Hall, M.D. &c, Lond. 1836, p. 34, or Amer. Edit. Philad. 1836. b Proceedings of the Royal Society. No. 34, for 1837-8 ; see, also, Solly on the Brain, p. 145, Lond. 1836 ; and Dr. Jqhn Reid, Edinb. Med. and Surg. Journ., Jan 1841. p. 12. c Prix de l'Academie Royale de Chirurgie, vol. iv.p. 373. Paris, 1819. 356 MUSCULAR MOTION. rior part of the encephalon ; in others, the posterior part; and in every one of the former, paralysis of the posterior ; in the latter, of the anterior extremities succeeded. Having, in one animal, muti- lated the whole of the right hemisphere, and only the anterior part of the left, he found that the animal was paralysed in the hinder extremities, and in the paw of the left fore-leg, but that the paw of the right remained active.3 Lastly, the motions of the tongue, or of articulation, are some- times alone affected in apoplexy. The seat of this variety of mus- cular motion has been attempted to be deduced from pathological facts. Foville places it in the cornu ammonis and temporal lobe ; and Bouillaudb in the anterior lobe of the brain, in the medullary substance; the cineritious being concerned, he conceives, in the intellectual part of speech. It is sufficiently obvious, from the whole of the preceding detail, that the mind must still remain in doubt, regarding the precise part of the encephalon engaged in the functions of muscular motion. The experiments of Magendie are, perhaps, more than any of the others, entitled to consideration. They appear to have been insti- tuted without any particular bias ; to subserve no particular theory; and they are supported by pathological facts furnished by others. He is, withal, a practised experimenter, and one to whom phy- siology has been largely indebted. His vivisections have been more numerous, perhaps, than those of any other individual. His investigations, however, on this subject clearly show, that owing to the different structures of animals, we cannot draw as extensive analogical deductions from comparative anatomy and physiology, as might be anticipated. The greatest source of discrepancy,indeed, between his experiments and those of MM. Rolando and Flourens, appears to have been the employment of different animals. Where the same animals were the subjects of the vivisections, the results were in accordance. The experiments demand careful repetition, accompanied by watchful and assiduous observation of patholo- gical phenomena; and, until this is effected, we can, perhaps, scarcely feel justified in deducing, from all these experiments and investigations, more than the general propositions regarding the influence of the cerebro-spinal axis on muscular motion, which we have already enunciated. The nerves, it has been shown, are the agents for conducting the locomotive influence to the muscles. At one time, it was universally believed, that the same nerve conveys both sensation and volition; but the pathological cases, that not unfrequently occurred, in which either sensation or voluntary motion was lost, without the other being necessarily implicated, and, of late years' the beautiful additions to our knowledge of the spinal nerves, for which we are mainly indebted to Sir Charles Bell,c and Magen- 1 Adelon, Physiologie de l'Homme, edit. cit. ii. 44. b Magendie's Journal de Physiologie, torn. x. c The Nervous System, &c. 3d edit. Lond.-1837. See, also, Narrative ofthe Dis- coveries of Sir Charles Bell in the Nervous System, by A. Shaw, London, 1839. STATE OF MUSCLES IN ACTION. 357 die,3 have satisfied the most skeptical, that there are separate nerves for the two functions, although they may be enveloped in the same neurilemma, or nervous sheath ; or in other words, may con- stitute the same nervous cord. We have more than once asserted, that the posterior part of the spine, with the nerves proceeding from it, is chiefly concerned in the function of sensibility ; and that the anterior column, and the nerves connected with it, are inser- vient to muscular motion; whilst a third column intervenes, which, in the opinion of Sir Charles Bell, is the source of all the respiratory nerves, and ofthe various movements connected with respiration and expression. It is proper here again, to observe, that although these two distinguished physiologists agree in their assignment of function to the anterior and posterior columns ofthe spinal marrow, Bellingerib has deduced very different inferences from the same experiments. He asserts, that having divided, on living animals, either the anterior roots of the spinal nerves, and the anterior column ofthe medulla spinalis, or the posterior roots of these nerves, and the posterior column of the marrow, he did not occasion, in the former case, paralysis of motion, and in the latter, of sensation ; but only, in the one,.the loss of all the move- ments of flexion ; and in the other, of those of extension. In his view, the brain and its prolongations, as the crura cerebri, corpora pyramidalia, the anterior column of the spinal marrow, and the nerves connected with it, preside over the movements of flexion; and, on the contrary, the cerebellum and its extensions, as the pos- terior column of the medulla spinalis, and the nerves connected with it, preside over the movements of extension : he infers, in other words, that there is an antagonism between these sets of nerves. The primd facie evidence is against the accuracy of Bel- lingeri's experiments. The weight of authority in opposition to him is, in the first place preponderant; and in the second place, it seems highly improbable, that distinct nerves should be em- ployed for the same kind of muscular action. Moreover, in some experiments on the frog, Professor Mullerc has established the correctness of the views of Bell. It seems, that the different phy- siologists, who engaged in the inquiry before he did, employed warm-blooded animals in their experiments, and he imagines, that the pain, resulting from the necessarily extensive wounds, may have had such an effect on tfee nervous system as to modify, and perhaps even counteract, the results. Miiller employed the frog, whose sensibility is less acute, and its tenacity of life greater. If the spinal marrow of this animal be exposed, and the posterior roots of the nerves of the lower extremities be cut. not the least * Precis Elementaire, &c. i. 216, 2de edit. >> Exper. Physiol, in Med. Spinal. August, Taurin. 1825 ; Ragionamenti, Sperienze, &<••, comprovanti l'Antagonismo Nervoso, &c. Torino, 1833; and an Analysis of the same, in Edinb. Med. and Surg. Journ., Jan. 1835, p. 160. e Annates des Sciences Natur. xxiii.: see, also, Panizza, in Edinb. Med. and Surg. Journ. vol. xlv. 358 MUSCULAR MOTION. motion is perceptible when the divided roots are excited by mecha- nical means, or by galvanism. But if the anterior roots be touched, the most active movements are instantly observed. The move- ments may also be excited by the galvanic pile. These experi- ments, Miiller remarks, are so readily made, and the evidence they afford is so palpable, that they leave no doubt as to the correctness ofthe views of Sir Charles Bell.3 Recent experiments, by M. Magendie, and by Dr. Kronenberg,b of Moscow, show, that a portion of the fibres of the sensitive roots extends to the point of union between them and the ante- rior roots, and is reflected to the anterior column of the spinal marrow ; —the return or reflection of the fibres taking place near the junction of the two roots. This arrangement of the fibres accounts for the fact, often noticed by physiologists, that some degree of sensibility appears to be manifested, in experiments on animals, when the motor roots of the nerves are irritated. The sensibility ofthe portio dura has been long known, and was pro- perly ascribed to its receiving filaments of the fifth pair. The supposed motor properties of the posterior roots may be accounted for under Dr. Marshall Hall's views ofthe nervous system, before described, (p. 71,) since irritation of these will cause reflex actions through the motor nerves distributed to the same parts.6 In the ordinary cases of the action of a voluntary muscle, the nervous influence, emanating from some part of the cerebro-spinal axis, under the guidance of volition, proceeds along the nerves, with the rapidity of lightning, and excites the muscle to contraction. The muscle, which was before smooth, becomes rugose, the belly more tumid, the ends approximate, and the whole organ is ren- dered thicker, firmer, and shorter. The recent researches of Mr. Bowman have shown, that in the state of contraction the transverse striae, before described as existing in each fibre, approach each other; whilst its diameter is increased ; hence the solid parts are more closely approximated, and the fluid which previously existed between them is pressed out so as to form bullae in the sarcolemma,as represent- Fig. 76. Muscular fibre of Dytiscus in contraction. — {Bowman.) edinFig. 76,from Mr. Bowman. The marginal representations,Fig. 77, of the muscular fibre of the skate at rest and in contraction are, also,from Mr. Bowman. It isproper to remark, however, that these * See the remarks already made on Sir C. Bell's System of the Nerves, at page 64 ; also, Elements of Physiology, by Baly, p. 644, Lond. 1838. b Muller's Archiv. Heft v. 1839. e British and Foreign Medical Review, April, 1840, p. 547 ; and Carpenter's Hu- man Physiology, § 89, Lond. 1842. STATE OF MUSCLES IN ACTION. 359 representationsare of muscular fibres,when in an unnatural condition, Fig. 77. : ""1 :^-TPS separated, that is, from the rest of the economy, and it cannot be considered established that contraction excited by the agency of the nerves is accomplish- ed in precisely the same manner.3 With regard to the precise degree of contraction or shortening, which a mus- cle experiences, some difference of sen- timent has prevailed. Bernouilli and Keill,b estimated it at one-third of the length; and Dumasc carried it still higher. It must, of course, be propor- tionate to the length of the fibres, — being greater, the longer the fibres. It has, also, been a subject of experiment and speculation, whether the bulk and the specific gravity of a muscle are augmented during its contraction. Bo- rellid and Sir Anthony Carlisle*3 affirm, that its size is increased. In the experiments of the latter, the arm was immersed in a jar of water, with which a barometrical tube was connected; and when the muscles were ofT^T*™"$£$S&?£S£ made to contract strongly, the level of of contraction (2,3,4). -(Bowman.) the water in the tube was raised. Glisson, however, from the same experiment, deduced opposite conclusions; Swammerdam and Er- mann/appear to be of hisopinion,and Sir Gilbert Blane,&Mr. Mayo,h Barzellotti,1 and MM. Dumas and Prevost,k during the most careful experiments, could see no variation in the level of the fluid ; and, consequently, do not believe, that the size of a muscle is modified by its contraction. Sir Gilbert Blane inclosed a living eel in a glass vessel filled with water, the neck of which was drawn out into a fine tube ; then, by means of a wire, introduced into the vessel, he irritated the tail of the animal, so as to excite strong con- traction, during which he noticed, that the water in the vessel remained entirely stationary. He, likewise, compared the two sides of a fish, one of which had been crimped, and thus brought into a state of strong contraction ; the other left in its natural con- » Carpenter, op. cit., § 371, 372. See, also, Mr. Paget, Brit, and For. Med. Rev., July, 1H42, p. 276. b Tentamina-Medico-Physica, Lond. 1718. « Principes de Physiologie, &c, 2de edit. Paris, 1806. a De Motu Animalium, addit. J. Bernouillii, Medit. Mathem. Muscul. L. B. 1710. e Philos. Transact, for 1805, p. 22, 23. t Gilbert's Annalen, p. 40. s A Lecture on Muscular Motion, &c. Lond. 1778 ; and Select Dissertations, &c. p. 239. »> Anatomical and Physiological Commentaries, i. 12 ; and Outlines of Human Physiology, 3d edit. p. 35, Lond. 1833. 1 Esame di alcune moderne Teorie intorno alia Causa prossima della Contrazione moscolare, Siena, 1796. k Op. citat, and Magendie's Precis, &c. i. 222. 360 MUSCULAR ACTION. dition : their specific gravity was precisely the same. The expe- riment of Barzellotti was the following. He suspended, in a glass vessel, the posterior half of a frog, filled the jar with water, and closed it with a stopper, traversed by a narrow, graduated tube. The muscle was then made to contract by means of galvanism, but in no case was the level of the liquid in the tube changed. It may, then, be concluded, that the bulk of a muscle is not greater when contracted than when relaxed. During contraction, the muscle is sometimes so rigid and elastic as to be capable of vibration when struck. The ordinary firm state is well exhibited by the masseter,when the jaws are forcibly closed, and some men possess the power of producing sonorous vibrations by striking the contracted biceps with a metallic rod. It has been a matter of dispute whether the quantity of blood, circulating in a muscle, is diminished during its contraction, At one time, it was universally believed, that such dirninution existed, and accounted for the diminished size 0f the muscle during con- traction. This last allegation we have already shown to be inac- curate ; and no correct deduction can, consequently, be drawn from it. Six Anthony Carlisle3 adopted the opinion, that the mus- cles become pale during contraction ; but he offers no proof of it. The probability is, that he implicitly obeyed, in this respect, the dicta of his precursors, without observing the incongruity of such a supposition with his idea, that the absolute size ofthe muscle is augmented during contraction. The truth is, we have no evidence, that the colour of a muscle, or the quantity of blood circulating in it, is at all altered during contraction. Bichatb who adopted the opinion, that the blood is forced out during this state, relies chiefly upon the fact, known to every one, that, in the operation of blood- letting from the arm, the flow of blood is augmented by working the muscles ; but the additional quantity expelled in this case is properly ascribed, by Dr. Bostock,c to the compression ofthe large venous trunks, by the swelling out of the bellies of the muscles. The prevalent belief, amongst physiologists of the present day, is, that there is no change of colour in the muscle during con- traction. When the extremities of a muscle are made to approximate, the belly, of course, swells out, and would probably expand to such an extent, that the fasciculi, of which it is composed, would sepa- rate from each other, were it not for the cellular membrane and aponeuroses, with which they and the whole muscle are enveloped. The phenomena, attendant upon the relaxation of a muscle, are the reverse of those, that accompany its contraction. The belly loses its rugose character, becomes soft, and the swelling subsides, the ends recede, and the organ is as it was prior to contraction. It is obvious, however, that after a part, as the arm, has been bent by the contraction of appropriate muscles, simple relaxation would not be sufficient to restore it to its original position ; for although 1 Op. citat. p. 27. b Anat. General, torn. ii. c Physiology, 3d edit. 94, Lond. 1836. THEORIES OF MUSCULAR CONTRACTION. 361 the relaxation of a muscle has been regarded, by Bichat and others, to be, in part, at least, an active effort, and to consist in something more than the mere cessation of contraction, the evidence in favour of this view is extremely feeble and unsatisfactory. The arrange- ment of the muscular system is, in this as in every other respect, admirable, and affords signal evidence of Omnipotent agency. The arm, as in the case selected above, has not only muscles to bend, but also to extend it; and, accordingly, when it has been bent, and it becomes necessary to extend it, the flexor muscles are relaxed and rest, while the extensors are thrown into action. This disposition of antagonist muscles prevails in almost every part of the frame, and will require notice presently. Muscles are not, however, the sole agents in replacing parts. Many elastic textures exist, which, when put upon the stretch by muscular contraction, have a tendency to return to their former condition, as soon as the extending cause is removed. Of this, a good example occurs in the cartilages of prolongation, which unite the ribs to the sternum. During inspiration, these elastic bodies are extended; and, by returning upon themselves, they become active agents of expiration; tending to restore the chest to its un- expanded state. The production of the phenomena of muscular contraction is, so far as we know, unlike any physical process with which we are acquainted. It has, therefore, been considered essentially organic and vitaf; and, like other operations of the kind, will probably ever elude our researches. Yet here, as on every obscure subject, hypotheses have been innumerable; varying according to the fashionable systems of the day, or the views of the propounder. They who believed that the musclar fibre is hollow, or vesicular, ascribed its contraction to distension, by the influx of the animal spirits, or of the blood; and relaxation to the withdrawal of those fluids. Such were the hypotheses of Borelli,3 Stuart,b and others. Independently, however, of the great objection to these views,— that we have no positive evidence of the existence of rhomboidal or other vesicles, or of the tubular form of the elementary fibre, — it is obvious, that the explanation is defective, inasmuch as we have still to look to the cause, which produces this mechanical influence. Again, how are we to account, under this hypothesis, for the surprising efforts of strength executed by muscles ? The mechanical influence of animal or other spirits — granting for a moment their existence — might develope a certain degree of force; but how can we conceive them able, as in the case of the muscles inserted into the foot, to develope such a force as to project the body from the ground ? In all these cases, a new and occult force is generated in the brain; and this, by acting on the muscular fibre, is the grand, efficient cause of the contraction. Moreover, what an inconceivable amount of fluids would be necessary to a De Motii Animalium, Lugd. Bat. 1710. •> De Structura et Motu Musculari, Lond. 1738. VOL. I.--- 31 362 MUSCULAR MOTION. produce the contraction of the various muscles, which are con- stantly in action ; and what, it has been asked, becomes of these fluids when relaxation succeeds to contraction? Some have affirmed, that they are absorbed by the venous radicles; others, that they run off by the tendons ; and others, again, that they be- come neutralized in the muscle, and communicate to it the greater size it possesses, in proportion as it is more exercised. These phantasies are too abortive to require comment. When chemical hypotheses were in fashion in medicine, physio- logy participated in them largely. At one time it was imagined that an effervescence was excited in the muscle by the union of two substances, one of which was of an acid, the other of an alka. line nature. Willis, Mayow, Keill,3 Bellini,b &c, supported opi- nions of this kind ; some ascribing the effervescence to a union of the nervous fluid with the arterial blood ; others to a union of the particles ofthe muscular fibre with the nervous fluid ; and others, to the disengagement of an elastic gas, primitively contained in the blood, and separated from it by the nervous spirits. It would, however, be unprofitable, as well as uninteresting, to repeat the different absurdities of this period—so prolific in physical ob- scurities. Medicine has generally kept pace with physics, and where the latter science has been dark and enigmatical, the former has been so likewise. In physiology, this is especially apparent; most ofthe natural philosophers of eminence having applied their doctrines in physics to the explanation of the different functions of the human frame. Newton, Leibnitz, and Descartes, were all speculative physiologists. The discovery of electricity gave occa- sion to its application to the topic in question; and it was ima- gined, that the fibres of the muscle might be disposed in such a manner, as to form a kind of battery, capable of producing con- traction by its explosions; and after the discovery of galvanic electricity, Vallic attempted to explain muscular contraction, by supposing, that the muscles have an arrangement similar to that of the galvanic pile. Hallerd endeavoured to resolve the problem by his celebrated doctrine of irritability, which will engage attention hereafter. He conceived, that the muscles possess, what he calls, a vis insita; and that their contraction is owing to the action of this force, excited by a stimulus, which stimulus is the nervous influx directed by volition. This, it is manifest, affords us no new light on the mysterious process. It is, in fact, cutting the gordian knot. We should still have to explain the precise mode of action of this vis insita.e The hypothesis of Prochaskaf is entirely futile. He gratui- tously presumes, as we have seen, that the minute ramifications of * Tentamin. Medico-Physic, No. v., Lond. 1718. b Bostock,op.cit. p. 111. c Experiments in Animal Electricity, Lond. 1793. d Element. Physiol, xi. 214 ; and Oper. Minor., torn. i. e Dr. M. Hall, art. Irritability, Cyclop, of Anat. and Physiol., July, 1840. r De Came Musculari, § ii. Vienn. 1778. ELECTRICAL THEORY OF MUSCULAR CONTRACTION. 353 the arteries are every where connected with the ultimate mus- cular filaments, twining around them, and crossing them in all directions. When these vessels are rendered turgid by an influx of blood, — by passing among the filaments, he conceives they must bend the latter into a serpentine shape, and thus diminish their length, and that of the muscle likewise. Sir Gilbert Blane3 again, throws out a conjecture, deduced from those experiments, in which he found that the actual bulk of a muscle is not changed during contraction, but that it gains in thickness exactly what it loses in length—that this maybe owing to the muscle being composed of particles of an oblong shape; and that when the muscle is contracted, the long diameter ofthe particle is-removed from a perpendicular to a transverse direction. But the same objection applies to this as to other hypotheses on the subject; that it is entirely gratuitous — resting on no anatomical support whatever. There are two views which may be esteemed the most preva- lent at the present day ; the one, which considers muscular con- traction to be a kind of combustion ; the other, that it is produced by electricity. The former, which was originally propounded by Girtanner,b and zealously embraced by Beddoes, who was more celebrated for his enthusiasm than for the solidity of his judgment, has now but few supporters. This hypothesis supposes, that muscular contraction depends upon the combustion of the com- bustible elements of the muscle, hydrogen, and carbon, by the oxygen of the arterial blood; the combustion being produced by the nervous influx, which acts in the manner of an electric spark ; — at least, such is the view adopted by Richerand,0 one of the most fanciful of physiological speculators. Of course, we have neither direct nor analogical evidence of any such combus- tion, which, if it existed at all, ought to be sufficient, in a short space of time, to entirely consume the organs that afford the ele- ments. The idea is as unfounded as numerous others that have been entertained, and is worthy only of particular notice, from its being professed in one of the few works, which we possess on physiological science. The second hypothesis refers muscular contractions to electricity. Attention has been already directed to the electroid or galvanoid character of the nervous agency ; and we have some striking examples on record of the analogous effects produced by the physi- cal and by the vital fluid on the phenomena under consideration. It has been long known, that when nerves and muscles are ex- posed in a living animal, and brought into contact, contractions or convulsions occur in the muscles. Galvanid was the first to point this out. He decapitated a living frog, removed the fore- paws, and quickly skinned it. The spine was divided, so as to a Op. citat. b Journal de Physique, xxxvii. 139. c Elements of Physiology, § 163. a Mem. sull' Electricita Animate, Bologn. 1797. 364 MUSCULAR MOTION. leave the spinal marrow communicating only with the hind extre- mities by means of the lumbar nerves. He then took, in one hand, one ofthe thighs of the animal, and the vertebral column in the other, and bent the limb until the crural muscles touched the lumbar nerves. At the moment of contact, the muscles were strongly convulsed. The experiment was repeated by Volta,a Aldini,b Pfaff,c Humboldt,d and others, and with like results. Aldinie observed convulsions in the muscles by the contact of those organs with nerves, not only in the same frog, but also in two dif- ferent frogs. He adds, that he remarked them when he put the nerves of a frog in connexion with the muscular flesh of an ox recently killed. Humboldt made numerous experiments of this kind on frogs. He found convulsions supervene when he placed upon a dry plate of glass a posterior extremity whose crural nerves had been exposed, and touched the nerves and the muscles with a piece of raw muscular flesh, insulated at the extremity of a stick of sealing-wax. Convulsions likewise occurred, when, instead of one piece of flesh, he used three different pieces to form the chain, one of which touched the nerve, the other the thigh, and the third the two others. The experiments were repeated by Ritter with similar results, but they were only found to succeed, when the frogs were in full vital activity, especially in spring, after pairing ; when the animal was of sufficient size, and its preparation for the experiment had been rapidly effected. From all these experiments it might be inferred, that parts of an animal may form galvanic chains, and produce a galvanic effect, which, independently of any mechanical excitation, may give rise to the contraction of muscles. This excitation of elec- tricity in chains of animal parts, M. Tiedemann thinks, ought not to be esteemed a vital act. Its effects only — the contractions ex- cited in the muscles — are dependent on the vital condition of the muscles and nerves. He considers, that the electricity, excited in chains of heterogeneous animal parts, may be modified and aug- mented by the organic or living forces; and that, moreover, in certain animals, organs exist, the arrangement of which is such as to excite electricity during their vital action —as in the differ- ent kinds of electrical fishes ; but in some experiments, instituted by M. Edwards/ the same effects, as those above referred to, were produced by touching a denuded nerve with a slender rod of silver, copper, zinc, lead, iron, gold, tin, or platinum, and drawing it along the nerve for the space of from a quarter to a third of an inch. He took care to employ metals of the greatest purity, as a Memoriasull' Electricita Animale, 1782. •> Essai Theoretique et Experiment sur le Galvanisme, Paris, 1804. c Ueber thierische Electricitat und Reizbarkeit, Leipz. 1795. 4 Versuche ueber die gereizte Muskel, und Nervenfaser, Posen und Berlin, 179 7. e Traite complet de Physiologie de l'Homme, par Tiedemann, traduit par Jourdan p. 559, Paris, 1837. f Appendix to Edwards on the Influence of Physical Agents on Life,__Hodgkin and Fisher's translation, Lond. 1832. EFFECT OF ELECTRICITY ON THE NERVES. 355 they were furnished him by the assayers of the mint. But it was not even necessary that the rod should be metallic ; he succeeded with glass or horn. All these metals, however, did not produce equally vigorous contractions. Iron and zinc were far less effec- tive than the others, but no accurate scale could be formed of their respective powers. Much difference is found to exist, when electricity is employed, according as the nerve is insulated or not; for as the muscular fibre is a good conductor of electricity, if the nerve be not insu- lated, the electricity is communicated to both nerve and muscle, and its effect is consequently diminished. It became, therefore, interesting to M. Edwards to discover, whether any difference would be observable, when one metal only was used, according as the nerve was insulated or not. In the experiments above re- ferred to, the nerve was insulated by passing a strip of oiled silk beneath it. A comparison was now instituted between an animal thus prepared, and another whose nerves instead of being insu- lated, rested on the subjacent flesh. He made use of small rods, with which he easily excited contractions, when he drew them from above to below, along the denuded portion of nerve which was supported by the oiled silk, but he was unable to excite them, when he passed the rod along the nerve of the other animal which was not insulated. His experiments were then made on two nerves of the same animal, and he found that after having vainly attempted to produce contractions by the contact of a nerve rest- ing upon muscle, they could still be induced if the oiled silk were had recourse to, and he was able to command their alternate ap- pearance and disappearance, by using a non-conductor or a con- ductor for the support of the nerve. Somewhat surprised at these results, M. Edwards was stimulated to the investigation, — whether some degree of contraction might not be excited by touching the uninsulated nerve, and having remarked, that con- tractions were most constantly produced in the insulated nerve by a quick and light touch, he adopted this method on an animal whose nerve was not insulated, and frequently obtained slight contractions. All his experiments on this subject seemed to prove, that cseteris paribus, the muscular contractions, produced by the contact of a solid body with a nerve, are much less considerable, or even wholly wanting, when the nerve, in place of being insu- lated is in communication with a good conductor, and it would seem to follow, as a legitimate conclusion, that these contractions are dependent on electricity ; facts, which it is well to bear in mind, in all experiments on animals where feeble electrical influ- ences are employed.3 Galvanic electricity, we shall see hereafter, is one of the great tests of muscular irritability, and is capable of occasioning con- tractions for some time after the death of the animal, as well as of » See Dr. Coldstream, art. Animal Electricity, in Cyclop. Anat. and Physiol. P. ix. p. 93, Jan. 1837 ; and J. Miiller, Elements of Physiology, by Baly, p. 261, Lond. 1838. 31* 366 MUSCULAR MOTION. maintaining, for a time, many of the phenomena peculiar to life. Hence the reason, why muscular contraction, which is provoked by this nervous, electroid fluid, has been regarded as an electrical phenomenon. Much discrepancy has, however, arisen amongst the partisans of this opinion, regarding its modus operandi. Rolando, we have seen, assimilates the cerebellum to an electro- motive apparatus, which furnishes the fluid that excites the mus- cles to contraction. Some have compared the spinal column to a voltaic pile, and have supposed the contraction of a mus- cle to be owing to an electric or galvanic shock. The views of MM. Dumas and Prevost3 are amongst the most novel. By a microscope, magnifying ten or twelve diameters, they first of all examined the manner in which the nerves are arranged in a muscle ; and found, as has been already observed, that their ramifications always entered the muscle in a direction perpen- dicular to its fibres. They satisfied themselves, that none of the nerves really terminate in the muscle; but that the final ramifica- tions embrace the fibres, like a noose, and return to the trunk that furnishes them, or to one in its vicinity, — the nerve setting out from the anterior column of the spinal marrow, and returning to the posterior. On farther examining the muscles at the time of their contraction, the parallel fibres, composing them, were found, by the microscope, to bend in a zigzag manner, and to exhibit a number of regular undulations; such flexions forming angles, which varied according to the degree of contraction, but were never under fifty degrees. The flexions, too, always occurred at the same parts of the fibre, and to them the shortening of the muscle was owing, as MM. Dumas and Prevost proved by calcu- lating the angles. The angular points were always found to cor- respond to the parts where the small nervous filaments enter or pass from the muscles. They therefore believed, that these fila- ments, by their approximation, induce contraction ofthe muscular fibre; and this approximation they have ascribed to a galvanic current running through them; which, as the fibres are parallel and very near each other, they have thought, ought to cause them to attract each other, according to the law laid down by Ampere, that two currents attract each other when they move in the same direction. The living muscles are consequently regarded by them, as galvanometers, and galvanometers of an extremely sensible kind, on account of the very minute distance and tenuity of the nervous filaments. They moreover affirm, that, by anatomical arrangement, the nerve is fixed in the muscle in the very position required for the proper performance of its function ; and they esteem the fatty matter, which envelopes the nervous fibres, and which was discovered by Vauquelin, as a means of insulation for preventing the electric fluid from passing from one of the fibres to the other. Soon after hearing of Ampere's discovery of the attraction of a Journal de Physiologie, torn. iii. 301 ; and Magendie's Precis, i. 220. CHEMICAL THEORY OF MUSCULAR CONTRACTION. 367 electrical currents, it occurred to Dr. Roget,3 that it might be pos- sible to render the attraction between the successive and parallel turns of heliacal or spiral wires very sensible, if the wires were sufficiently flexible and elastic ; and, with the assistance of Dr. Faraday, his conjecture was put to the test of experiment, in the laboratory of the Royal Institution of London. A slender harpsi- chord-wire, bent into a helix, being placed in the voltaic circuit, instantly shortened itself whenever the electric stream was sent through it ; but recovered its former dimensions the moment the current was intermitted. From this experiment it was supposed, that possibly some analogy might hereafter be found to exist be- tween this phenomenon and the contraction of muscular fibres. The views of Dumas and Prevost have been altogether denied by M. Raspail,b inasmuch as it is impossible, he says, to distin- guish, by the best microscope, the ultimate muscular fibre from the small nervous fibrils by which those gentlemen consider them to be surrounded loopwise. He farther affirms, that the zigzag form is the necessary result of the method in which they performed their experments, and is produced by the muscular fibre adhering to the glass on which it was placed. His own idea, founded on numerous observations, is, that the contraction of the fibre in length is always occasioned by its extension in breadth under the influence of the vital principle. Independently, however, of Ras- pail's objection, the circumstance, that,in this mode of viewing the subject, the muscle itself is passive, and the nerve alone active, is a weighty stumbling-block in the way of the views of both MM. Dumas and Prevost, and of Dr. Roget. It is proper, too, to remark, that Person0 was unable to detect any galvanic currents in the nerves by the most sensible galvanometer; and that other stimuli besides galvanism are capable of exciting the muscular fibre to contraction. This we daily see in experiments on the frog, by dropping salt on the denuded muscle. J. Miillerd hence infers, that a nerve of motion, during life, and whilst its excitability or irritability continues, is so circumstanced, that whatever suddenly changes the relative condition of its molecules excites a contractipn at the remote end of the muscle, and that electrical, chemical, and mechanical irritants are, in this respect, similarly situate. With regard to the hypothesis, which ascribes muscular contrac- tility to the chemical composition of the fibre, or that which main- tains, that the property is dependent upon the mechanical structure ofthe fibre, they are undeserving of citation, notwithstanding the respectability of the individuals, who have written and experi- mented on the subject. They merely seem to show, that here, as in every case, a certain chemical and mechanical constitution is * Electro-Magnetism, p. 59, in 2d vol. of Nat. Philosophy, Library of Useful Know- ledge, Lond. 1832. b Chimie Organique, p. 212, Paris, 1833. « Journal de Physiologie, torn. x. Paris, 1830. a Art. Electricitat (thierische) in Encyclopad. Worterb. der Medicin Wissench. x. 545, Berlin, 1834. 368 MUSCULAR MOTION. necessary, in order that the vital operation, peculiar to the part, may be developed. But not only is it necessary, that the muscle shall possess a pro- per physical organization, it must, likewise, be endowed with one, that is essentially vital — in other words, with irritability or con- tractility. The cause of the ordinary contraction of muscles is, doubtless, the nervous influx, but if we alter the condition of the muscle, by tying the vessels that supply it with blood, although the nervous influx may be properly transmitted to it, there will be no contraction. We moreover find, that after a muscle has acted for some time, it becomes fatigued, notwithstanding volition may regularly direct the nervous influx to it; and that it requires repose, before it is again capable of executing its functions. In the upper classes of animals, contractility remains for some time after dissolution ; in the lower classes, especially in the am- phibia, the period during which it is evinced, on the application of appropriate stimuli, is much greater. From experiments on the bodies of executed criminals, Nysten found that the irritability ceased in the following order. The left ventricle of the heart first; the intestinal canal at the end of forty-five or fifty-five minutes; the urinary bladder at nearly the same time; the right ventricle after the lapse of an hour; the oesophagus at the end of an hour and'a half; the iris a quarter of an hour later; the mus- cles of animal life somewhat later; and lastly, the auricles of the heart, especially the right, which, in one instance, under the in- fluence of galvanism, contracted sixteen and a half hours after death. These results are singular, and the experiments merit re- petition. It is, indeed, strange, that nerves of organic life, appa- rently circumstanced so much alike, should vary so greatly in the length of time during which ihey retain their irritability. One ofthe most interesting of the many experiments that have been made on the bodies of criminals recently deceased, for the purpose of exhibiting the effects of galvanism on muscular irrita- bility, is detailed by Dr. Ure.a The subject was a murderer, named Clydesdale, a middle-sized athletic man, about thirty years of age. He was suspended from the gallows nearly an hour, and made no convulsive struggle after he dropped. He was taken to the theatre of the Glasgow University in about ten minutes after he was cut down. His face had a perfectly natural aspect, being neither livid nor tumefied ; and there was no dislocation of the neck. In the first experiment, a large incision was made into the nape of the neck, close below the occiput, and the spinal marrow was brought into view. A considerable incision was made, at the same time, into the left hip, through the glutaeus maximus muscle, so as to expose the sciatic nerve,baud a small cut was made in the 1 Art. Galvanism, in Diet, of Chemistry, Hare and Bache's Amer. Edit. Philad. 1821. . b It is not necessary, in these experiments, to expose the nerve. The author has long known, that, in the case ofthe frog, this is needless, and, in his experiments, has been in the habit of acting under this knowledge. The experiments made on EFFECTS OF GALVANISM. 369 heel, from neither of which any blood flowed. A pointed rod, connected with one end of a galvanic battery, of two hundred and seventy pairs of four-inch plates, was now placed in contact with the spinal marrow, whilst the other rod was applied to the sciatic nerve. Every muscle ofthe body was immediately agitated with convulsive movements, resembling a violent shuddering from cold. The left side was most powerfully convulsed at each renewal of the electric contact. On removing the second rod from the hip to the heel, the knee being previously bent, the leg was thrown out with such violence as nearly to overturn one of the assistants, who in vain attempted to prevent its extension. In the next experiment, the left phrenic nerve was exposed at the outer edge of the sterno-thyroideus muscle. As this nerve is distri- buted to the diaphragm, and communicates with the heart through the pneumogastric nerves, it was expected that, by transmitting the galvanic fluid along it, the respiratory process might be renewed. Accordingly, a small incision having been made under the cartilage of the seventh rib, the point of one rod was brought into contact with the great head of the diaphragm, whilst the point of the other was applied to the phrenic nerve in the neck. The diaphragm, which is a main agent in respiration, was instantly contracted, but with less force than was expected. " Satisfied," says Dr. Ure, " from ample experience on the living body, that more powerful effects can be produced in galvanic excitation, by leaving the ex- treme communicating rods in close contact with the parts to be operated on, while the electric chain or circuit is completed, by running the end of the wires along the top of the plates in the last trough of either pole, the other wire being steadily immersed in the last cell of the opposite pole, I had immediate recourse to this method. The success of it was truly wonderful. Full, nay labo- rious breathing, instantly commenced. The chest heaved and fell; the belly was protruded and again collapsed, with the relaxing and retiring diaphragm. This process was continued without interrup- tion, as long as I continued the electric discharges. "In the judg- ment of many scientific gentlemen who witnessed the scene, this respiratory experiment was perhaps the most striking ever made with a philosophical apparatus. Let it also be remembered, that for full half an hour before this period, the body had been well- nigh drained of its blood, and the spinal marrow severely lacer- ated. No pulsation could be perceived, meanwhile, at the heart or wrist; but it may be supposed, that but for the evacuation of the blood, — the essential stimulus of that organ, — this phenome- non might also have occurred." In a third experiment, the supra-orbital nerve was laid bare in three criminals, — two of whom were executed at Philadelphia, and the third at Lan- caster, Pennsylvania — showed, indeed, that the effect was even greater when the nerves were not exposed. It was found, too, to be more marked when the current was transmitted from the peripheral extremity of a nerve towards its centre. See Bell's Select Medical Library, for Oct. 1839; Amer. Journ. of Med. Sciences, May, 1840, p. 13 ; and Medical Examiner, Jan. 23d and 30th, 1841. 370 MUSCULAR MOTION. the forehead. The one conducting rod being applied to it, and the other to the heel, most extraordinary grimaces were exhibited. Every muscle in the face was simultaneously thrown into fearful action. " Rage, horror, despair, anguish, and ghastly smiles, united their hideous expression in the murderer's face, surpassing far the wildest representation of a Fuseli or of a Kean." At this period, several of the spectators were forced to leave the room from terror or sickness, and one gentleman fainted. The last experiment consisted in transmitting the electric power from the spinal marrow to the ulnar nerve as it passes by the internal condyle at the elbow, when the fingers moved nimbly, like those of a violin performer; and an assistant who tried to close the fist, found the hand open forcibly in spite of every effort to prevent it. When the one rod was applied to a slight incision in the tip of the forefinger, the fist being previously clenched, that finger was instantly extended; and from the con- vulsive agitation of the arm, he seemed to point to the different spectators, some of whom thought he had come to life. The experiments of Dr. Ure have been several times repeated in this country, on the bodies of criminals, and with analogous results.3 What important reflections are suggested by the perusal of such cases ! The strict resemblance between the galvanic and the nervous fluids,b and the absorbing idea, to the philanthropist, that galvanism may be found successful in resuscitating the appa- rently dead, in cases where other means would probably fail ! Unfortunately, it can rarely happen, that the means will be at hand, and can, consequently, be available. It must, however,-be borne in mind, that, in the case just narrated, many of the effects were produced two hours after respiration had been finally arrested. An experiment, described by Dr. George Fordyce,c signally ex- hibits the power of the contractility, which is resident in the tissue. He slightly scratched, with a needle, the inside of a heart removed from the body, when it contracted so strongly as to force the point of the needle deep into its substance. This experiment has been often cited, for the purpose of showing, that the mechanical effect, in such cases, is infinitely greater than the mechanical cause pro- ducing it; and hence, as we have endeavoured already to show, that all mechanical explanations must be insufficient to account for the phenomena of muscular contraction ; we are compelled, indeed, to infer, that a new force must always be generated. Between twenty and thirty years ago, a cause was tried before the Court of Exchequer in England, in which a better knowledge ofthe properties of muscle might have led to a different result. According to the English law, where a man marries a woman, seised of an estate of inheritance, and has, by her, issue born alive, which a Dr. W. Dunbar, in Baltimore Med. and Surg. Journal, i. 245, Bait. 1833, and the Journals referred to in the preceding page. b See, on this subject, the remarks at page 89 ; and Richerand's El£mens de Physi- ologie, edit de Berard aine, p. 260, § clxvii. Bruxelles, 1837. c Philos. Transact, for 1788, p. 25. RELAXATION OF MUSCLES. 371 was capable of inheriting her estate ; in such case he shall, on the death of his wife, hold the lands for his life, as tenant by the cour- tesy of England. It has, consequently, been a point of moment for the husband to show that the child was born alive ; and the law authorities have, with singular infelicity, attempted to define what shall be regarded evidences of this condition. According to Blackstone,3 " it must be born alive. Some have had a notion that it must be heard to cry, but that is a mistake. Crying, in- deed, is the strongest evidence of its being born alive, but it is not the only evidence." According to Coke,b " if it be born alive it is sufficient, though it be not heard to cry, for peradventure it may be born dumb.0 It must be proved that the issue was alive ; for mortuus exitus non est exitus: so as the crying is but a proof that the child was born alive, and so is motion, stirring, and the like." This latitudinarian definition has given occasion to most erroneous decisions, as in the trial alluded to, in which the jury agreed that the child was born alive ; because, although, when immersed in a warm bath, immediately after birth, it did not " cry or move, or show any symptoms of life ;" yet, according to the tes- timony of two females,— the nurse and the cook, — there twice appeared a twitching and tremulous motion of the lips; and this was sufficient to make it fall under Lord Coke's definition. It is manifest, that, granting such motion to have actually occurred, it was of itself totally insufficient to establish the existence of vitality. We have seen, that on the application of stimuli, the muscles of a body may be thrown into contraction for two hours after the ces- sation of respiration. Instead, therefore, of referring the irritability to the existence, at the time, of the vital principle, it must be re- garded simply as an evidence, that the parts have previously and recently formed part of a living system. The contraction of a muscle is followed by its relaxation ; — the fibres returning to their former condition. This appears to be a passive state ; and to result from the suppression of the nervous influx by the will; —in other words, to be produced by the simple cessation of contraction. Some have, however, regarded both states to be active, but without any proof. Barthezd maintains, that the relaxation of the muscle is produced by a nervous action the reverse of that which occasions its contraction ; the will re- laxing the muscles as well as contracting them. The muscle is the only part susceptible of contraction. The tendon conveys the force, developed by it, passively to the lever, which has to be moved. It has been recently ascertained by MM. Becquerel and Breschet,e » Commentaries, B. ii. 127. b Institutes, 30, a. <= It need scarcely be said, that the deaf-dumb cry at the moment of birth the same as other children. The natural cry is effected by them as well as by the infant that possesses all its senses. It is the acquired voice, alone, which they are incapable of attaining. a Nouveaux Elemens de la Science de l'Homme, Paris, 1806. e Archiv. du Museum, torn. i. p. 402. 372 MUSCULAR MOTION. that a muscle during contraction augments in temperature. This increase is usually more than one degree of Fahrenheit, but at times when the exertion has been continued for five minutes — as in the case of the biceps of the arm, in sawing wood, it has been double that amount.3 Lastly, a sensation instructs the mind that a muscle has con- tracted, and this has given rise to the notion of a muscular sense, and a sensation of motion: — the Muskelsinn, Bewe- gungssinn or muscular sense of Gruithuisen, Lenhossek,b Brown,c Sir C. Bell,d and others writers. It appears to be an in- ternal sensation, produced by the muscle pressing on the sensible parts surrounding it; which parts convey the sensation to the brain. It is by this muscular sense that the brain learns to adapt the effort to the effect to be produced. Without it no precision could exist in the movements of the muscles, and every manual effort — whether of the artist or the mechanic — would be con- fused and disorderly. The step, too, would be unsteady and in- secure. "In chewing our food," says Dr. A. Combe,6 " in turning the eyes towards an object looked at, in raising the hand to the mouth, and, in fact, in every variety of muscular movement which we perform, we are guided by the muscular sense in proportioning the effect to the resistance to be overcome ; and where this har- mony is destroyed by disease, the extent of the service rendered us becomes more apparent. The shake of the arm and hand which we see in drunkards, and their consequent incapability of carrying the morsel directly to the mouth, are examples of what would be of daily occurrence, unless we were directed and assisted by a muscular sense." It enables us to form ideas of force and resist- ance, by conveying to our minds a distinct idea of the effect re- quired. The force or intensity of muscular contraction is dependent upon two causes; — the physical condition ofthe muscle, and the energy of the brain. A muscle, which is composed of large, firm fibres, will contract, — the energy of the brain being equal, — more forcibly than one with delicate, loose fibres. Volition generally determines the degree of power developed by the voluntary mo- tions ; and is accurately regulated so as to raise a weight of one pound or of one hundred. Again, we notice astonishing efforts of strength in those that are labouring, at the time, under strong cerebral excitement; under mania, rage, delirium, &c. In such cases, the delicate muscles of the female are capable of contracting with a force far transcending that of the healthy male. The power of muscular contraction is, therefore, in a compound ratio with the strength of the organization of the muscle, and the degree of exci- tation of the brain. When both are considerable, the feats of * Todd and Bowman, Physiological Anatomy and Physiology of Man, Pt. l,p. 184, Lond. 1843. '" Rudolphi, Grundriss der Physiologie. c Lectures on Moral Philosophy. d The Hand, &c, Amer. Edit. p. 145, Philad. 1833. e Principles of Physiology, 5th edit. p. 131, Edinb. 1836. FORCE OF MUSCULAR CONTRACTION. 373 strength surpass belief; and where both are small, the results are insignificant. The extensors of the knee and foot occasionally contract with so much violence as to fracture the patella and the tendo-achilles, respectively. The force, developed in the calf of the leg, must be great, when a person stands on tiptoe with a bur- den on his head or shoulders ; or when he projects his body from the soil, as in leaping. Rudolphi3 asserts, that he has seen a horse, which fractured its under-jaw by biting a piece of iron. It has been a question, whether the power of a muscle is greater or less at different degrees of contraction, the same stimulus being applied. To determine this, Schwannb invented an apparatus, which should accurately measure the length ofthe muscle, and the weight, which it would balance by its contraction; and, from his experiments, it appeared that a uniform increase of force is attended with a nearly uniform increase in the length of the muscle. The explanation of this by Dr. Carpenter is probably just; — viz., that, as the observations of Mr. Bowman have clearly shown, there must be a considerable displacement of the constituents of every fibre during contraction, it is easy to understand, that the greater the contraction the more difficult must any farther contraction become. " If, between a magnet and a piece of iron attracted by it, there were interposed a spongy elastic tissue, the iron would cease to approach the magnet at a point, at which the attraction of the magnet would be balanced by the force needed to compress still farther the intermediate substance."0 We have a number of feats of surprising strength on record: several of which are collected by Sir David Brewster.d Of these, the cases of John Charles Van Eckeberg, who travelled through Europe under the appellation of Samson, and of Thomas Topham, are the most authentic and extraordinary. Dr. Desaguliers saw Topham, by the strength of his fingers roll up a very strong and large pewter dish. He broke seven or eight short and strong pieces of tobacco-pipe with the force of his middle finger, having laid them on his first and third finger. Having thrust under his garter the bowl of a strong tobacco-pipe, his legs being bent, he broke it to pieces by the tendons of his hams without altering the flexure of his knee. He broke another such bowl between his first and second fingers, by pressing his fingers together sideways. He lifted a table six feet long—which had half a hundred weight hanging at the end of it — with his teeth, and held it in a hori- zontal, position for a considerable time, the feet of the table resting against his knees. He took an iron kitchen poker, about a yard long, and three inches in circumference, and, holding it in his right hand, he struck upon his bare left arm, between the elbow and wrist, till he bent the poker nearly to a right angle. He took such another poker, and holding the ends of it in his hands, and a Grundriss der Physiologie, Berlin, 1821, u. s. w. «> J. Miiller, Physiology, p. 903. c Carpenter, Human Physiology, § 394, Lond. 1842. a Letters on Natural Magic, Amer. Edit. p. 222, New York, 1832. VOL. I. — 32 374 MUSCULAR MOTION. the middle against the back of his neck, he brought both ends of it together before him; and afterwards pulled it nearly straight again. He broke a rope, about two inches in circumference, which was in part wound about a cylinder of four inches in diameter, having fastened the other end of it to straps that went over his shoulders. Lastly, he lifted a rolling-stone, eight hundred pounds in weight, with his hands only, standing in a frame above it, and taking hold of a chain that was fastened to it. That much depends upon physical organization, as regards the force of muscular contraction, is evinced by the fact of the great difference in this respect in the various races of mankind. On our own continent, numerous opportunities have occurred for wit- nessing the inferiority, in strength, of the aborigines to the white settlers. Peron3 took with him, in his voyage round the world, one of Regnier's dynamometers, which indicates the relative force of men and animals. He directed his attention to the strength of the arms and ofthe loins, making trial on several individuals of different nations; viz., twelve natives of Van Diemen's land, seventeen of New Holland, fifty-six of the island of Timor, seven- teen Frenchmen belonging to the expedition, and fourteen Eng- lishmen in the colony of New South Wales. The following was the mean result: Strength A ( Of the Arms. > Ofthe Loins. Kilogrammes.^ 50-6 Myriagrammes. - 50-8 10-2 58-7 - - - 11-6 - 69-2 15-2 71-4 - - - 16-3 1. Van Diemen's Land, ... 2. New Holland, .... 3. Timor, ..... 4. French,..... 5. English,..... The highest numbers, in the first and second divisions, were respectively 60 and 62 ; the lowest in the fifth, 63 ; in the highest S3, for the strength of the arms. In the power of the loins, the highest amongst the New Hollanders was 13; the lowest of the English 12-7.c The force of muscular contraction, is, also, largely increased by the proper exercise of the muscles. Hence the utility of the ancient gymnasia. In early times, muscular energy commanded respect and admiration. It was regarded as the safeguard of families, and the protection of nations; and it was esteemed a matter of national policy to encourage its acquisition. In modern times, the invention of gunpowder having altered the system of » Voyage, &c, torn. i. chap. xx. p. 446 ; and t. ii. p. 461. See, also, Lawrence's Lectures on Physiology, &c. p. 404, Lond. 1819. b The approximate value of a kilogramme is about two pounds avoirdupois :__of a myriagramme about twenty. c See Quetelet, Sur l'Homme, &c, Paris, 1835; and Prof. Forbes, of Edinburgh, in the London and Edinburgh Phil. Magazine, for March, 1837, p. 197 ; and Dungli- son's American Med. Intelligencer, for May 15, 1837, p. 74; in which are detailed experiments on the weight, height, and strength of above eight hundred individuals, natives of England, Scotland, Ireland, and Belgium. DURATION OF MUSCULAR CONTRACTION. 375 warfare, and given to agility the superiority, which strength com- municated in personal combats, institutions for the development of the muscular system have been abandoned, until of compara- tively late years. They afford us striking examples of the value of muscular exertion, not only in giving energy and pliancy to the frame, but as a means of preserving health. The mean effect ofthe labour of an active man, working to the greatest possible advantage, and without impediment, is generally estimated to be sufficient to raise ten pounds, ten feet in a second for ten hours in a day ; or to raise one hundred pounds, which is the weight of twelve wine gallons of water, one foot in a second, or thirty-six thousand feet in a day; or three millions, six hun- dred thousand pounds, or four hundred and thirty-two thousand gallons, one foot in a day. Dr. Desaguliers affirms, that the weakest men, who are in health, and not too fat, lift about one hundred and twenty-five pounds : and the strongest of ordinary men four hundred pounds. Topham lifted eight hundred. The daily work of a horse is estimated to be equal to that of five or six men. In insects, the force of muscular contraction appears to be greater in proportion to their size than it is in any other animals. The Lucanus cervus or Stag Beetle, has been known to gnaw a hole of an inch diameter in the side of an iron canister in which it had been confined,3 and many striking examples of a similar kind are given hereafter under the head of Flying. In the duration of muscular contraction, we notice considerable difference between that of the voluntary and of the involuntary muscles ; the latter being much more rapid and alternating. The same remark applies to the voluntary muscles, when excited by some other stimulus than that of the will. Contraction, excited by volition, can be maintained for a considerable time : of this we have examples in bearing a burden, the act of standing, holding the arm extended from the body, &c. In all these cases, the con- tractility of the muscles is sooner or later exhausted, fatigue is experienced, and it becomes necessary to give them rest; the power of contractility, however, is soon resumed, and they can be again put in action. This law of intermission in muscular action appears absolute ; — relaxation being followed by contrac- tion, in every organ, from the commencement of life until its final cessation. The intermission has, indeed, by many physiologists, been held to prevail — to a slight extent only, it is true — during, what we are in the habit of considering, continuous, muscular contraction. In proof of this, they cite the fact, that when we put the tip of the finger into the meatus auditorius externus, we hear a kind of buzzing or humming, which does not occur when an inert body is introduced.1* There are, however, other actions going on in the finger, besides this of muscular contraction ; and a Carpenter, Human Physiology, § 396, Lond. 1842. b Wollaston, in Philosoph. Transact, for 1810, p. 2. 376 MUSCULAR MOTION. the buzzing might, with as much propriety, be referred to the noise made by the progression of fluids in the vessels, as to the oscillations of muscular contraction and relaxation. We know not, in truth, whence the sound immediately proceeds. In the velocity of muscular contraction, much difference also exists, according to the stimulus which sets it in action. If we apply galvanism to a muscle, we find the contractions at first ex- ceedingly rapid ; but they become progressively feebler, and require a stronger stimulus, until their irritability appears to be exhausted. Irritating the nerve in these cases, is found to produce a greater effect, than when the stimulus is applied directly to the muscle. The velocity of voluntary contraction is, of course, variable, being regulated entirely by the will. We have, in various classes of the animal kingdom, remarkable instances of this velocity. The mo- tions of the racer, of the greyhound, of the practised runner, of the fingers in playing upon musical instruments — as the violin, flute, piano-forte, — and in writing; of the voice in enunciation, and of the upper and lower limbs in striking, leaping, and kicking, convey a general notion of this rapidity of contraction, and how nicely, in many cases, it must be regulated by volition. The fleetest race- horse, on record, was capable of going, for a short distance, at the rate of a mile per minute ; yet this is trifling, when compared with the velocity of certain birds — which can, with facility, wheel round and round the most rapid racer in circles of immense dia- meters, — and with that of numerous small insects, which accom- pany us, when we travel with great rapidity — even against the wind — with apparent facility. It has frequently excited surprise, how the migratory birds can support themselves so long upon the wing, as to reach the country of their migration, and, at the same time, live without food during their aerial voyage. The difficulties of the subject have impelled many to deny the fact of their migration ; and have excited others to form extravagant theories to account for the preservation of the birds during the winter months; but if we attend to their excessive velocity, the difficulties, in a great measure, vanish. " Nothing," says Wilson,3 " is more common in Pennsylvania than to see large flocks of the bluebirds, in spring and fall, passing at considerable heights in the air, — from the south in the former, from the north in the latter season. The Bermudas are said to be six hundred miles from the nearest part of the continent. This may seem an extraordinary flight for so small a bird ; but it is a fact that it is performed. If we suppose the bluebird to fly only at the rate of a mile a minute, which is less than I have actually ascertained them to do over land, ten or twelve hours would be sufficient to accomplish the journey." Montagu, a celebrated ornithologist, estimates the rapidity with which a hawk and many other birds occasionally fly, to be not less than one hundred and fifty miles an hour ; and that one hundred miles per hour is certainly not beyond * American Ornithology, ii. 178. !**• VELOCITY OF MUSCULAR CONTRACTION. 377 a fair computation for the continuance of their migration. Major Cartwright, on the coast of Labrador, found by repeated observa- tions, that the flight of the eider duck is at the rate of ninety miles an hour, yet it has not been esteemed very remarkable for its swiftness. Sir George Cayley computes the rate of flight, even of the common crow, at nearly twenty-five miles an hour. Spallan- zani found that of the swallow about ninety-two miles an hour; and he conjectures, that the velocity of .the swift is nearly three times greater. A falcon, belonging to Henry IV. of France, escaped from Fontainbleau, and was, in twenty-four hours after- wards, at Malta — a distance computed to be not less than one thousand three hundred and fifty miles, making a velocity of nearly fifty-seven miles an hour, supposing the falcon to have been on the wing the whole time; but, as such birds never fly by night, if we allow the day to have been at the longest, his flight was per- haps at the rate of seventy-five miles per hour. It is not probable, however, as Montagu observes, that it either had so many hours of light in the twenty-four to perform its journey, or that it was retaken at the moment of its arrival.3 A society of pigeon fanciers from Antwerp despatched ninety pigeons from Paris, the first of which returned in four hours and a half, at a rate of nearly fifty miles an hour. Out of one hundred and ten pigeons, carried from Brussels to London in the summer of 1830, and let fly from London on July 19th, at a quarter before nine, a.m., one reached Antwerp, one hundred and eighty-six miles distance, at eighteen minutes past two, or in five and a half hours, being at the rate of nearly thirty- four miles an hour. In another case, one went from London to Maestricht, two hundred and sixty miles, in six and a quarter hours. In January, 1831, two pigeons, carried from Liskeard to London, were let loose in London, One reached Liskeard, two hundred and twenty miles distant, in six hours; the other in a quarter of an hour more.b There is an instance of the migratory or passenger pigeon — the Columba migratoria of Wilson — having been shot in Fifeshire, in Scotland. It was the first ever seen in Great Britain, and had been forced over, it was imagined, by unusually strong westerly gales.c The velocity of the contraction of the muscles of the wings, in these rapid flights, is incalculable. The possible velocity, in any case, must be greatly dependent upon habit. Nothing can be more awkward than the first attempts at writing, drawing, play- ing on musical instruments, or performing any mechanical process in the arts; and what a contrast is afforded by the astonishing celerity, which practice never fails to confer, in any one of those varieties of muscular contraction ! In running, leaping, wrestling, dancing, or any other motion ofthe body, one person can execute a Fleming's Philosophy of Zoology, ii. 42, Edinb. 1822. b Turner's History ofthe World, Amer. Edit. i. 259, New York, 1832. • New Monthly Magazine for 1826. 32* 378 MUSCULAR MOTION. with facility, what another, with equally favourable original powers, cannot effect, because he has not previously and frequently made the attempt. Prize-fighting affords an instance of this kind of muscular velocity and precision acquired by habit, — the prac- tised boxer being able to inflict his blow and return his arm to the guard so quickly as almost to elude the sight. By considering the muscular motions, employed in transporting the body of the fleetest horse, Haller has, concluded that the elevation of the leg must have been performed in Tyh part of a second. He calculates, that the rectus femoris—the large muscle which is attached to the knee-pan and extends the leg — is shortened three inches in the ¥yh part of a second in the most rapid movements of man. But, he adds, the quickest motions are executed by the muscles, concerned in the articulation of the voice. He himself, in one ex- periment, pronounced fifteen hundred letters in a minute ; and as the relaxation of a muscle occupies as much time as its contrac- tion, the contraction of a muscle, in pronouncing one of these letters, must have been executed in •jo1ootn Part °fa mhnite ; and in much less time in some letters, which require repeated contrac- tions of the same muscle or muscles, as r. If the tremors, that occur in the pronunciation of this letter, be estimated at ten, the muscles concerned in it, must have contracted, in Haller's experi- ment, in 3o^otn Part °f a minute.3 It has been calculated, that all the tones, of which the human voice is capable, are produced by a variation of not more than one-fifth of an inch in the length of the vocal cords; and that in man, the variation required to pass from one interval to another will not be more than ^Vo^ 0I" an inch.b These cases are, however, far exceeded by the rapidity of the vibrations of the wings of insects, which can be estimated from the musical tone they induce, experiment having shown the number of vibrations required to produce any given note. The vibrations of their wings have thus been found to amount to seve- ral thousands per second. It has been the opinion of many physiologists and metaphysi- cians, that muscular contraction is only within certain limits of velocity directed by volition ; and that when it exceeds a certain velocity, it evidently depends upon habit. The effects of volition have, in this respect, been divided into the immediate and remote. Of the first we have examples in the formation of certain vocal and articulate sounds, and in certain motions of the joints, as in the production of voice, speech, and locomotion. In the second, those actions are included which we conceive to be within our power, but where we think only ofthe end to be obtained, with- out attending to the mechanical means. " In learning a language, for example," says Dr. Bostock,6 " we begin by imitating the pro- 1 Elementa Physiologia;, &c. xi. 2, Lausan. 1757-1766. b Carpenter, Human Physiology, § 397, Lond. 1842. c Physiology, edit. cit. p. 774, Lond. 1836. ELEMENTARY PRINCIPLES OF MECHANICS. 379 nunciation of the words, and us a direct effort to put the organs of speech in the proper form. By degrees, however, we become familiar with this part of the operation, and think only of the words, that are to be employed, or even the meaning, that is to be conveyed by them. In learning music, we begin by imitating particular motions of the fingers, but at length the fingers are dis- regarded, and we only consider what sounds will follow from cer- tain notes, without thinking of the mechanical way in which the notes are produced." In these, however, and in all other cases that can be brought forward, it is difficult to conceive how the effect can be produced without the agency of volition, — obscure it is true, but still in action. The case of reading is often assumed, as confirming the view that invokes habit: yet, if a letter be in- verted, we immediately detect it; and although, by habit, we may have acquired extreme facility in playing the notes of a rapid musi- cal movement, no doubt, we think, ought to exist, that an effort of volition is exerted on each note composing it, — inasmuch as there is no natural sequence of sounds, and hence there appears no cogent reason, why one should follow rather than another, unless a controlling effort of the will were exerted. With regard to the extent of muscular contraction, this must of course be partly regulated by volition ; but it is also greatly owing to the length of the muscular fibres. The greater the length, of course the greater the decurtation during contraction. We shall see, likewise, that this depends upon the kind of lever, which the bone forms, and the distance at which the muscle is inserted from the joint or fulcrum. Before passing to the examination of special movements, it will be necessary to consider briefly a few elementary principles of mechanics, most of which are materially concerned in every ex- planation, and without some knowledge of which such explana- tion would of course, be obscure or unintelligible. Were we, as Magendie3 has remarked, to investigate narrowly every motion of the body, we should find the applicability to them of almost all the laws of mechanics. If we take a rod of wood or metal,of uniform matter throughout, and support it at the middle, either like the beam of a balance, or on a pointed body, we find, that the two ends accurately balance each other ; and if we add weights at corresponding parts of each arm of the beam, that is, at parts equidistant from the point of sus- pension, the balance will still be maintained. The point, by which the beam is suspended, or at which it is equilibrious, is called the centre of gravity of the beam ; and, in every mass of matter, there is a point of this kind, about which all the parts balance or are equilibrious ; or, in other words, they have all this centre of gravity or of inertia. The centre of gravity, in a mass of regular form and 1 Precis, &c. edit. cit. i. 276. 380 MUSCULAR MOTION. Fig. 79. uniform substance, as in the parallelograms, Figs. 78 and 79, is easily determined, inasmuch as it must necessarily occupy the centre c ; but in bodies, that are irregular, either as regards density or form, it has to be determined by rules of calculation, to be found in all works on physics, but which it is unne- cessary to adduce here. The nearer the centre of gravity is to the soil on which the body rests, the more stable is the equili- brium. In order that the Figures 78 and 79 shall be overturned from left to right, the whole mass must turn upon e as upon a pivot; the centre of gravity describing the curve c b, and the whole mass being lifted in the same degree. In Fig. 78, the curve is nearly horizontal, owing to the narrowness of the base and the height of the centre of gravity. In Fig. 79, on the other hand, whose base is broad and the centre of gravity low, the curve rises considerably ; the resistance to overturning is consequently nearly equal to the whole weight of the body, and the equilibrium is necessarily firm. The condition of equilibrium, of a body resting upon a plane, is such, that a perpen- dicular, let fall from the centre of gravity, shall fall within the points by which it touches the plane. This perpendicular is called the vertical line or line of direction, being that in which it tends natu- rally to descend to the earth ; and the space comprised between the points by which the body touches the soil is called the base of sus- tentation. We can now understand, why a wagon, loaded with heavy goods, may pass with safety along a sloping road; whilst, if it be load- ed to a greater height with a lighter substance, it may be readily overturned. When the wagon is loaded with metal, the centre of gravity is low as at c, Fig. 80; the vertical line c p falls consi- derably within the base of sustentation; and the centre describes a rising path; but in the other case the centre is thrown higher, to a ; and the vertical line falls very near the wheel, or on the outside of it, and consequently ofthe base, whilst the centre describes a falling path. Of two hollow columns, formed of an equal quantity of the same matter and of the same height, that, which has the largest cavity, will be the stronger of the two ; and of two columns of the same diameter, but of different heights, the higher will be the weaker. All bodies tend to continue in the state of motion or of rest, so as to render force necessary to change their state. This property Fig. 80. ELEMENTARY PRINCIPLES OF MECHANICS. 381 is called the inertia of motion, or of rest, as the case may be. When a carriage is about to be moved by horses, considerable ef- fort is necessary to overcome the inertia of rest; but if it move with velocity, effort is also required to arrest it, or to overcome the inertia of motion. We can thus understand, why, if a horse start unexpectedly, it is apt to get rid of its burden; and why an unprac- tised rider is projected over his horse's head if it stop suddenly. In the former case, the inertia of rest is the cause of his being thrown; in the latter, the inertia of motion. The danger of attempting to leap from a carriage, when the horses have taken fright, is thus, likewise, rendered apparent. The traveller has acquired the same velocity as the vehicle ; and if he leap from it, he is thrown to the ground with that velocity ; thus incurring an almost certain injury to avoid one more remotely contingent. The force, momentum, or quantity of motion in a body is mea- sured by the velocity, multiplied into the quantity of matter. A cannon-ball, for example, may be rolled so gently against a man's leg, as not even to'bruise it; but if it be projected by means of gunpowder it may mow down a dense column of men, or pene- trate the most solid substances. If a man be running, and strike against another, who is standing, a certain shock is received by both ; but if both be running in opposite directions with the same velocity, the shock will be doubled. The subject of the direction of forces applies to most cases of muscular movements. Where only one force acts upon a body, the body proceeds in the direction in which the force is exerted, as in the case of a bullet fired from a gun ; but if two or more forces act upon it at the same time, the direction of its motion will be a middle course between the directions of the separate forces. This course is called the resulting direction, that is, resulting from the composition of Fis- 81- the forces. Let us suppose two forces a T and b T in Fig. 81, acting upon the body T, which may be regarded as the tendon of a muscle, and the two forces as the power developed by muscular fibres holding the same situation ; the result will be the same, whether they act together or in succession. For example, if the force a T is sufficient to draw T to a, and im- mediately afterwards the force b T be exerted upon it, the tendon will be at c, the place towards which it would be drawn by the simultaneous action of the two forces or fibres. If, therefore, we complete the figure, by drawing a c equal and parallel to T b, and c b equal and paral- lel to a T, we have the parallelogram of forces, as it is called, of which the diagonal shows the resultant of the forces, and the course of the body on which they act. In the case, assumed in 382 MUSCULAR MOTION. Fig. 81, the forces are equal. If not so, the parallelogram may result as in Fig. 83 ; in which T c will, again, be the resultant of the forces a T and T b, or we may have the ar- rangement in Fig. 82. By these parallelograms, we are enabled, also, to resolve the resultant into its component forces. Suppose, for example, we are desirous of knowing the quantity of force in the resultant, T c, Fig. 81, which is capable of acting in the directions T a and T b; it is only necessary to draw, from the point c, c a parallel to T b, and c b parallel to T a; and the lines T a and T 6,cutoff by these, will be the forces into which it may be resolved. The same applies to Figs. 82 and 83, and to every other of the kind. Friction is the resistance necessary to be overcome in making one body slide over another ; and adhesion is the force, which unites two polished bodies when ap- g> 83, plied to each other,—a force, which is measured by the perpendicular effort necessary for separating the two bodies. The more polished the sur- faces in contact, the greater is the adhesion, and the less the friction; so that where the object is merely to facilitate the sliding of one surface over another, it will be always advan- tageous to make the surfaces polished, or to put a liquid between them. A beam or rod of any kind, resting at one part on a prop or sup- port, which thus becomes its centre of motion, is a lever. The ten inch beam, P W, Fjg- 84. Fig. 84, is a le- ver, of which F may be consi- dered the prop or fulcrum; P, the part at which the power is applied, and W, the point of application of the weight or resistance. In every lever we distinguish three points ; — the fulcrum, power, and resistance ; and, according to the relative position of these points, the lever is said to be of the first, second, or third kind. In a lever ofthe first kind, the fulcrum is between the resistance and the power, as in Fig. S4 : F being the fulcrum on which the beam rests and turns; P, the power ; and W, the weight or re- Lever of the first kind. ELEMENTARY PRINCIPLES OF MECHANICS. 383 sistance. We have numerous familiar examples of this lever ; — the crowbar in elevating a weight; the handle of a pump; a pair of scales; steelyard, &c. A lever of the second kind has the resistanceW, Fig. 85, between Fig. 85. the power P and the fulcrum F ; the fulcrum and 'TIT': v..... iiiimumuuimujuiiiiiiiiiiiiiiiiiuniuniiiiniiiia muimimnnnn 111111111111111111111 W power occupy- ing each one extremity. The Lever of the seCond kind. rudder of a ship, a wheelbarrow, and nut-crackers, are varieties of this kind of lever. In a lever ofthe third kind, the power P is between the resistance W, and the fulcrum F, Fig. 86 ; the resistance and the fulcrum oc- • cupying each one extremity ofthe le- Fig. 86. ver. In the two last levers, the weight and the power change places. — Tongs and shears are levers of this kind; and also a long ladder raised against a wall by the efforts of a man : here the fulcrum is at the part ofthe ladder, which rests on the ground ; the power is exerted by the man ; and the resistance is the ladder above him. In all levers are distinguished, — the arm of the power, and the arm of the resistance. The former is the distance comprised be- tween the power and the fulcrum, P F,Figs. 84, 85, and 86 ; and the latter is the distance W F, or that between the weight and the fulcrum. When, in the lever of the first kind, the fulcrum occu- pies the middle, the lever is said to have equal arms ; but if it be nearer the power or the resistance, it is said to be a lever with unequal arms. The length of the arm of the lever gives more or less advan- tage to the power or to the resistance, as the case may be. In a lever of the first kind, with equal arms, complete equilibrium would exist, provided the beam were alike in every other respect. But if the arm of the power be longer than that of the resist- ance, the resistance is, to the power as the length of the arm of the power is to that of the arm of the resistance; so that if the former be double or triple the latter, the power need only be one-half or one-third of the resistance, in order that the two forces may be in equilibrium. A reference to the figures will exhibit this in a clear light. The three levers are all presumed to be of equal substance throughout, and to be ten inches, or ten 384 MUSCULAR MOTION. feet, in length. The arm of the power, in Fig. 84, is the dis- tance P F, equal to eight of those divisions: whilst that of the resistance is W F, equal to two of them. The advantage of the former over the latter is, consequently, in the proportion of eight to two, or as four to one ; in other words, the power need only be one-fourth of the resistance, in order that the two forces may be equilibrious. In the lever of the second kind, the proportion of the arm P F of the power, is to that, W F, of the resist- ance, as ten — the whole length of the lever — to two; or as five to one: whilst, in the lever of the third kind, it is as two to ten, or as one to five; in other words, to be equilibrious, the power must be five times greater than the resistance. We see, therefore, that, in the lever of the second kind, the arm of the power must necessarily be longer than that of the resist- ance, since the power and the fulcrum are separated from each other by the whole length of the lever: hence, this kind of lever must always be advantageous to the power; whilst the lever of the third kind, for like reasons, must always be unfavour- able to the power, seeing that the arm of the resistance is the whole length of the lever, and, therefore, necessarily greater than that of the power. It can now be understood, why a lever of the first kind should be the most favourable for equilibrium; one of the second kind for overcoming resistance; and one of the third kind for rapidity and extent of motion: for whilst, in Fig. 86, the power is moving through the minute ark at P, in order that the lever may assume the position indicated by the dotted lines F w, the weight or resist- ance is moving through the much more considerable space W w. The direction in which the power is inserted into the lever, likewise demands notice. When it is perpendicular to the lever, it acts with the greatest advantage; the whole of the force deve- loped being employed in surmounting the resistance ; whilst, if inserted obliquely, a part of the force is employed in tending to move the lever in its own direction; and this part ofthe force is destroyed by the resistance of the fulcrum. Lastly, the general principles of equilibrium in levers consists in this: — that whatever may be the direction in which the power and resistance are acting, they must always be to one another inversely as the perpendiculars drawn from the fulcrum to their lines of direction. In Fig. 86, for example, the line of direc- tion of the upper weight isWio; that of the power P p; and to keep the lever in equilibrium in this position, the forces must be to one another inversely as F w to F p. In applying these mechanical principles to the illustration of muscular motion, we must, in the first place, regard each moveable bone as a lever, whose fulcrum or centre of motion is in its joint; the power at the insertion of the muscle ; and the resistance in its own weight and in that of the parts which it supports. In different APPLICATION OF MECHANICAL PRINCIPLES. 385 parts of the skeleton we find the three kinds of levers. Each of the vertebrae of the back forms, with the one immediately beneath it, a lever of the first kind ; the fulcrum being seated in the middle of the under surface of the body of the vertebra. The foot, when we stand upon the toe, is a lever of the second kind ; the fulcrum being in the part of the toes resting upon the soil, the power in the muscles inserted into the heel, and the resistance in the ankle joint, on which the whole weight of the body rests. Of levers of the third kind we have numerous instances ; of which the deltoid, to be described presently, is one, In this, as in other cases, the applicability of the principle, laid down regarding the arms of the lever, &c, will be seen, and we shall find, that, in the generality of cases, the power is inserted into the lever so near to the fulcrum, that considerable force must be exerted to raise an inconsiderable weight; — that so far, consequently, mechanical disadvantage is occasioned ; but we shall find, that such disadvantages enter into the economy of nature, and that they are attended with so many valuable concomitants, as to compensate richly for the expense of power. Some of these causes, that tend to diminish the effect of the forces, we shall first consider, and afterwards attempt to show the advantages resulting from these and similar arrange- ments in effecting the wonderful, the complicate, operations ofthe muscular system. In elucidation of this subject let us take, with Haller,3 the case of the deltoid — the large muscle, which constitutes the fleshy mass on the top ofthe arm, and whose office it is to raise the whole of the upper extremity. Let W F, Fig. 87, represent the os humeri, with a weight W at the eibow, to be raised by the deltoid muscle D. The fulcrum F is necessarily, in this case, in the shoulder joint; and the muscle D is inserted much nearer to the fulcrum than to the end of the bone on which the weight rests; the arm of the power P F, (supposing, for a moment, that it is acting at this part with every advantage, which we will see presently, it is not,) is, consequently, much shorter than that ofthe resistance WF, which, Fig. 87. as in all levers of the third kind, occupies the whole length of the lever. In estimating the effect from this cause alone upon the power to be exerted by the del- toid ; we may suppose, that the arm of the power is to that of the resistance as 1 to 3; the deltoid being inserted into the humerus about one-third down. Now, if we raise a weight of fifty-five pounds in this way, and add five pounds for the weight of the limb, (which may be conceived to act entirely at the end of the bone,) the power, which the deltoid must exert, to produce » Elementa Physiologije, xi. 2. vol. i.—33 AF 386 MUSCULAR MOTION. the effect, is not equal to sixty pounds, but to three times sixty, or one hundred and eighty pounds. Fig. 88. Action of the Deltoid. A, the Scapula ; B, the Os humeri; C, the Deltoid. Figure 88, strikingly exhibits the disadvantages of the deltoid, so far as regards the place of its insertion into the lever ; but many muscles have insertions much less favourable than the deltoid. The biceps, D, for example, in Fig. 89, — the muscle which bends the forearm on the arm, — is attached to the forearm ten times nearer the elbow-joint, or the fulcrum, than to the extremity of the lever; and if we apply the argument to it, — supposing the weight of the globe, in the palm of the hand, to be fifty-five pounds and the weight of the limb five pounds, — it would have to act with a force equal to sixty times ten, or six hundred pounds, to raise the weight. Muscles, again, are attached to the bones at Unfavourable angles. If they were inserted at right angles in the direction of P P, Fig. 87, the whole power would be effectually applied in moving the Fig. 89. A, the Os humeri; B, the Ulna; C, the Radius; D, the Biceps; E, insertion ofthe Biceps into the Radius. limb. On the other hand, if the muscle were parallel to the bone, the resistance, it is obvious, would be infinite, and no effect could result. In the animal, it rarely happens that the muscle is inserted APPLICATION OF MECHANICAL PRINCIPLES. 387 at the most favourable angle: it is generally much smaller than a right angle. Reverting to the deltoid, this muscle is inserted into the humerus at an angle of about ten degrees. Now, a power acting obliquely upon a lever, is to one acting perpendicularly, as the sine of inclination, represented by the dotted line F s, Fig. 86, to the whole sine P P. In the case of the deltoid the proportion is as 1,736,482 to 10,000,000. Wherefore, if the muscle had to contract with a force of one hundred and eighty pounds, owing to the disadvantage of its insertion near the fulcrum, it would have, from the two causes combined, to exert a force equal to 1,058 pounds. Again, the direction, in which the fibres are inserted into the tendon, has great influence on the power developed by the muscle. There are but few straight muscles, in which all the fibres have the same direction as the tendon. Fig. 90 will exhibit the loss of power, which the fibres must sustain in proportion to the angle of insertion. The fibre / F would, of course, exert the whole force upon the tendon, whilst the fibre t 90° would, by its contrac- tion, merely displace the tendon. Now, the force exerted is, in such case, to the effective force, — that is, to that which acts in moving the limb, — as the whole sine t F is to the sines of the an- gles at which the fibres join the tendon, represented by the dotted lines. Borelli and Sturm have calculated these proportions as [ follows: —At an angle of 30°j 'F t v they are as 100 to 87 ; at 45° as 100 to 70; at 26° as 100 to 89 ; at 14° as 100 to 97, and at 8° as 100 to 99. The largest angle, formed by the outer fibres of the deltoid, is estimated by Haller at 30°: the smallest about 8°. If this disad- vantage be taken into account, the deltoid will have to contract, with a force equal to 1,284 pounds, to raise fifty-five pounds at the elbow. It is farther contended by Borelli, Sturm, and Haller, that the force of the muscle, as estimated in the preceding calcu- lations, must be doubled, seeing that it has to exert as much force in resisting the bone which affords a fixed point at one extremity, as in elevating the weight at the other. This estimate, if admitted, would elevate the force, which must be exerted by the deltoid in raising the fifty pounds, to 2,568 pounds. Lastly. Much force is spent when a muscle passes over many joints. Antagonist muscles must, likewise, exert an influence of this kind, consuming a certain portion of the force developed in the contraction of the muscle. On the other hand, there are arrangements which augment the 388 MUSCULAR MOTION. power developed by muscles ; as the thick articular extremities of bones; the patella'and the sesamoid bones in general; all of which enlarge the angle, at which the tendon is inserted into the bone or lever. The projecting processes for muscular attachments, as the trochanters, the protuberance of the os calcis, the spinous processes of the vertebrae, &c. augment the arm of the lever, and are thus inservient to a like valuable purpose. The smoothness of the 4 articular surfaces of bones, — tipped, as they are, with cartilage, and the synovia, which lubricates the joints, by diminishing the friction, also aid the power, as well as the bursae mucosae, which are interposed wherever there is much pressure or friction, The trochleae or pulleys act only in directing the force, without augmenting its amount; and the same may be said of the bony canals and tendinous sheaths, by which the tendons of the muscles, especially those passing to the fingers and toes, are kept in their prbper course. Still, it must be admitted, that, as regards the effort to be exerted by the muscles, it must, in almost all cases, be much greater than the resistance it has to overcome. The very fact of the lever of the third kind being that which prevails in our move- ments exhibits this. The mere mechanician has conceived this to be an unwise construction; and that there is a needless expense of force for the attainment of a determinate end. In all cases we find, that the expense of power has been but little regarded in the construction of the frame ; nor is it necessary that it should have been. It must be recollected, that the contraction of the muscle is under the influence of volition, and that, within certain limits, the force, to be employed, is regulated by the influx sent by it into the muscles. The great object in the formation of the body, ap- pears to have been — to unite symmetry and convenience, with the attainment of great velocity and extent of motion, so that whilst the power is moving through but a small space, the weight or resistance shall move rapidly through one more extensive. We have seen that, in these respects, the lever ofthe third kind is most fitting. With any other, indeed, less power might be required; but there would be less extent of motion and less velocity, whilst the symmetry and convenience of the body would be destroyed. Suppose, for example, that in in Fig. 89, the biceps—instead of being inserted at E, near the elbow — had passed on to the wrist, or, to simplify the matter, to the extremity of the member; it would assuredly have acted with more force — the lever having been changed into one of the second kind — but the hand would have lost that velocity and extent of motion, which are so important to it; and the course of the muscle would have been so modified as to convert the convenient and symmetrical member into a cum- brous, webbed instrument, badly adapted for the multitudinous purposes to which it has to be applied. The same effect results, as Sir Charles Bell3 has remarked, from * Animal Mechanics, Library of Useful Knowledge, p. 27, Lond. 1829. APPLICATION OF MECHANICAL PRINCIPLES. 389 Fig. 91. Fig. 92. the.course of the ten- dons and their con- finement by sheaths, strengthened by liga- ments. If the tendon A, Fig. 91, took the shortest course to its termination at B, it would draw up the toe with more force ; but the toe would lose its velocity of movement: To favour this velo- city, we find that the majority of muscles are inserted obliquely into their levers, and the fibres into the tendons. By this arrangement, as we have proved, considerable loss of power results ; but, in the majority of cases, the motion is effected by a less degree of decur- tation than if the muscles were straight. Let A B and C D, Figs. 92 and 93, be parts of two ribs, that are parallel, and will continue parallel till they are brought into contact by the action of the straight muscle E F ; or by that of the oblique muscles F G and F H. Now it is obvious, that when the point E comes in con- tact with F, the length of the straight muscle E F must be null; whilst that of the oblique muscles will only have experienced a decurtation equal to G g and H h, Fig. 92 ; and to F g and FA,Fig.93. It is clear, also, that, Fis-93- in these cases, the straight mus- clescan never so contract as to ad- mit of a close ap- proximation of the ribs ; whilst the oblique mus- cles will admit ofthistoamuch greater extent. We can, therefore, understand, why the intercostal 33* 390 MUSCULAR MOTION. Fig. 95. A C rrrTTTTrr J?_____________Gr 1m11u1111iii11111111111111111111111111111111l1liii.u11111111iHi11111111111111.il!; jr. muscles pass obliquely from one rib to another, as at D and IJ C, Fig. 94, instead of in a direction perpendicular to the two ribs, as at A. There are cases, however, in which a straight muscle may pass between two parallel ribs, and carry them through a given space, with less decurtation of fibres, than any oblique muscle, which has the same origin, but is inserted at a greater distance from the centre of motion, and acts through the medium of a longer lever. Moreover, a muscle, with a less degree of obliquity, may be so situate as to carry the bones through a given space with a less decurtation of fibres than any other muscle having the same origin, but a much greater degree of obliquity. Suppose A B and C D, Fig. 95, to be two parallel ribs, of which A B is moveable about A, as a centre; and sup- pose it to be brought, by the action of the straight muscle E F, and of the oblique muscles E G and E H, into the position A/ The points of insertion of the muscles will now be at a, c, and e, after having traversed the spaces F a, G c, and H e. If we, now, from the point E, as a centre, describe the arcs c b and e d; the spaces d H and b G will indicate the degree of decurtation, which the oblique muscles have experienced, and a F that of the straight muscle. This figure also shows, that when the muscles change the relative position of any two bones, they at the same time, change the direction of their own action, and vary their lever. When the rib A B is brought into the position, Afi the muscles E G and E H,by being brought down to c and e, have assumed the positions E c and E e, and have, consequently, changed their length, situation, obliquity, and leverage. Again, of the muscles, that are attached to ribs that are parallel, equally moveable, and situate at right angles to the spine, those which pass perpendicularly from one rib to the other will act upon each with equal leverage, and each will approach the other with the same velocity ; whilst those, which pass obliquely from one to the other, will make them approach with different velocities; a principle which is strikingly applicable to the intercostal muscles. Let us suppose A B and C D, Fig. 96, to be two parallel ribs, arti- nuiiiiiiiiiiiiiiimiiiiiiiiiiiiTl APPLICATION OF MECHANICAL PRINCIPLES. 391 & A minim railiilillliTlti^j^Einiiiiimiiiii'iiiniHiiiiiiiiiiiiiiimiiiiiiiHiiii B ni'iin iili!liiiiiiiiiiii!iiiiiniiiii(iiiliiiiiiHiiiiiiiiiiiiiMii!iiiiiiiHiniiiiiiiiiiiiiiiiiiiiiiiTi53nni'Hiiiiri culated with the spine at A and C, and that they are equally move- able on these cen- tres of motion. Fig. 96. Let D B repre- sent a straight muscle, passing directly from the one rib to the other; and D E an oblique mus- cle. The levers of D B, accord- ing to the me- chanical princi- pies laid down, will be A B and C D, perpendiculars drawn from the centres of motion to the line of direction of the power. These levers, being parallel, are of course equal, but the levers of D E will be C F and A G, perpendiculars drawn from the centres of motion to the line of direction of the power. These levers are of differentlengths, and, accordingly, the muscle must act with different degrees of force on the two ribs; so that it will cause C D, on which it acts with the longest lever, to approach A B faster than it makes the latter approach the former, -— in the ratio ot C b to A C, or with three times the velocity. In all muscular motions, the levers of the power and of the re- sistance are undergoing variations; so that the degree of power, necessary to be developed in one position of the member, may be much less than in another. The case of the biceps, already re- ferred to, will elucidate this. Let E C, Fig. 97, represent the os humeri; E A the forearm ; E the elbow joint; W, a weight or resistance hung at the wrist, and D the biceps muscle, inserted at b, a tenth of the distance down the forearm. It is manifest that the force, necessary for bending the arm, ** • must be much great- er when it is in the position A E than in that of E a. The le- ver of the resistance, in the former case, is the whole length of the forearm ; or, in other words, the per- pendicular drawn from the fulcrum to the line of direction of the weight W; but, when the arm is # . raised to a, the lever of the resistance is no longer E A; it is E 392 MUSCULAR MOTION. Fig. 98. H!- but not only is the lever of the resistance shortened; that of the power is augmented. The lever of the biceps, when the forearm is horizontal, is the dotted perpendicular, drawn from the fulcrum at the elbow to the line of direction of the muscle ; but when the forearm is bent to the position E a, the disposition of the muscle is also modified. It assumes the position, occupied by the dotted line, which is farther distant from the fulcrum, and the lever ot the power is consequently increased. In this case, then, of the action of the biceps, in proportion as we raise the arm, the me- chanical disadvantages become less and less; the lever of the power increasing, whilst that of the resistance diminishes. In many of the changes of position of a body, whilst a bone is turning upon its centre of motion, the centre itself is often describing, at the same time, a curve. In Fig. 98, let A B represent the foot, B C the tibia, C D the thigh bone, and D E the trunk; and let us suppose it is required to bring the body to the erect position B F ; so that B C shall correspond to B G, C D to G I, and D E to I F. The point C will describe the curve C G ; and, whilst it is accom- plishing this, the point D is likewise mov- ing ; so that the latter, instead of describ- ing the curve D H, which it would do, were the centre of motion C fixed, pro- ceeds along the curve D I; the point E, again, is subjected to the like influence, and instead of describing the curve E K, which it would do if the centre D were fixed, rises along E F. The motions, produced by the mus- cles, may be either simple or compound. The simple muscles admit of variety; some being straight, composed of parallel fasciculi, others reflected in their course, and others, again, are cir- cular. In the straight muscles, each fibre, by its contraction, draws the tendon in its own direction ; and the effect ofthe whole is to bring it towards the centre ofthe muscle. In a long muscle, the whole contractile effort is concentrated on the tendon, in con- sequence of the course of the fibres being parallel to that of the tendon. In most of the broad muscles, on the other hand, as the attachments at both extremities are usually at different points, all the fibres do not concur in one effort. Different sets of fibres may have a very different action from others, and they are capable of being thrown separately into contraction. The ordinary direc- tion, in which a muscle acts, is from its tendinous, back to its aponeurotic, attachment — that is, from the moveable to the more fixed part; and, in a straight muscle, this direction can be accu- E PREPONDERANCE OF FLEXORS. 393 rately appreciated. It must be borne in mind, however, that the muscle can act in an inverse direction also. When the whole of the fibres, composing a broad muscle, are brought to act on the tendon, as in the case of the deltoid, we find, by the composition of forces, that the middle line of direction must be taken for the purpose of estimating their line of action. A part, however, may act and carry the arm upwards and outwards; whilst the opposite fibres may move it upwards and inwards. Where a muscle is reflected, like the superior oblique of the eye, and the peronei muscles, — the line of motion will be from the insertion to the point of reflection; precisely as a rope, passing over a pulley, raises the weight in a line drawn from the weight to the pulley. The circular muscles, which have no precise origin or inser- tion, are inservient to the contraction of the apertures around which they are placed. In executing the complex movements of any part of the frame, a combination of the action of the different muscles, attached to the part, generally occurs, rendering the process one of a compli- cated character. This, if no other cause existed, would render it extremely difficult to calculate the precise degree of force, which particular muscles, alone or in combination, are capable of exert- ing. The mathematical physiologists made multifarious attempts in this direction; but their conclusions were most discrepant. When we bear in mind, that the force, capable of being exerted by any muscle, is dependent upon the proper organization of the muscle, and likewise upon the degree of energy of the brain, it will be apparent, that all attempts of this kind must be futile. We can determine, with nicety, the effect of which the parts are capable, supposing them inanimate structures. We can calculate the disadvantages, caused by the insertion of the power near the fulcrum; by the obliquity of the line of action of the power, &c.; but we have not the slightest data for estimating the effect, pro- duced by the nervous influx, — by that mysterious process, which generates a new force, and infuses it into the muscles, in a manner so unlike that in which the ordinary mechanical powers are ex- erted. The data, necessary for such a calculation, would be the precise influx from the brain, — the irritability of the muscle, — the mechanical influences, dependent on the straight or oblique direction of the fibres composing the muscle, as regards the ten- don,— the perpendicular or oblique direction in which the tendon is attached to the bone, — the particular variety of lever, — the length ofthe arm ofthe power and that of the resistance, — the loss sustained from friction, and the diminution of such loss caused by the cartilages that tip the bones, and by the synovia, &c. — data, which it is impossible to attain; and hence the solution of the problem is impracticable. One great source of the combination of muscular motions is, the necessity for rendering one of the attachments fixed, in order that gg4 MUSCULAR MOTION. the full force may be developed on the other. In but few of the muscles is the part, whence the muscle originates, steady. To these few, the muscles of the eye which arise from the inner part of the orbit and pass forward to be inserted into the organ, belong. To show how distant muscles may be concerned in this fixation of one end of a muscle, when it is excited to the develop- ment of plenary power, we will take the case of the deltoid. This muscle arises from the scapula and clavicle, and is inserted into the os humeri; but the scapula and clavicle, themselves, are not entirely fixed; and, accordingly, if the deltoid were to contract alone, it would draw down the scapula and clavicle, as well as elevate the humerus. If, therefore, it be important to produce the latter effect only, the scapula and clavicle must be fixed by appro- priate muscles ; as by the rhomboidei, trapezius, &c. These mus- cles, however, arise from various vertebrae of the neck, which are themselves moveable. It becomes necessary, therefore, that the neck should be fixed by its extensors, which arise from the lumbar and dorsal regions. By the united action of all these muscles, the deltoid is able to exert its full effect in elevating the humerus. But the deltoid, like other muscles, is capable of acting inversely ; as in the case of a person lying on the ground, and attempting to raise himself, by laying hold of any object above him. The hand and forearm are thus rendered firm, and the deltoid now contracts from origin to insertion, and, consequently, elevates the scapula and clavicle. Again, if a person, in the recumbent posture, endea- vours to bend the head forwards, the recti muscles of the abdomen are firmly contracted, for the purpose of fixing the sternum, whence the sterno-cleido-mastoidei muscles in part arise, which can then exert their full power in bending the neck forwards. These instances will be sufficient to exemplify the mode in which the muscular motions are combined. The same principle prevails over the whole body ; and where a greater number of parts has to be moved, the case must, necessarily, be still more complex.3 When a part, moveable in various directions, is drawn towards any point, it must be rendered steady, and be prevented from de- viating, by the muscles on each side ; and the extent of its motion may be partly regulated by the action of antagonist muscles. Sup- posing, for instance, that the head is inclined forwards, there must be muscles, not only to move it in that direction, but also to pre- vent it from inclining to the right or left, and to limit the motion forwards ; although doubt may arise, whether this be not entirely effected by the nervous influx, sent by volition to the flexors of the head. Hence, some anatomists have considered, that there must, in these cases, be movers, directors, and moderators. In sleep, the muscles are perhaps in the most complete state of relaxation ; and, hence, this condition has been invoked, as afford- ing evidence of the comparative preponderance of particular an- a For an elaborate article on Animal Motion, Animal Dynamics, Locomotion, or Progressive Motion of Animals, by J. Bishop, see Cyclopaedia of Anatomy and Physiology, Pt. xxiii. p. 407, for April, 1842. ATTITUDES. 395 tagonizing muscles, — the flexors and extensors, for example. In perfect sleep, when no volition is exercised over the muscles, we find the body reposing in a state of semiflexion, — which seems to show, that the flexor muscles have slightly the advantage over the extensors. Richerand,3 has assigned the following reasons for this preponderance. First. The number of flexors is greater than that of extensors. Secondly. The fibres, composing them, are more numerous and longer : — take, for example, the sartorius, gracilis, semi-tendinosus, semi-membranosus, and biceps, which are the flexors of the leg, and the rectus and triceps cruris, which are its extensors. Thirdly. Their insertion is nearer the resistance and farther from the centre of motion, which adds to their force. Fourthly. Their insertion into the bones is at a larger angle, and nearer to the perpendicular; and Fifthly. Their arrangement is such, that the continuation of the movement of flexion renders them perpendicular to the bones to be moved. The explanation, afforded by Richerand, applies, on the whole, to the case he has selected, but there are many exceptions to it. The extensors of the thigh, foot, and jaw, are decidedly predominant; and, accord- ing to Adelon,b experiments, instituted by Regnier with his dyna- mometer, make the extensors some kilogrammes more powerful than the flexors. In our various attitudes, the movements of flex- ion certainly prevail largely ; but as the power of contraction is regulated by volition, it is unnecessary to inquire, whether there be any physical predominance in the flexors over the extensors, as has been attempted by Richerand. We have already seen, that we can in no way attain a knowledge of the degree of force, which any one muscle of the body is capable of developing. 5. ATTITUDES. The attitudes, which man is capable of assuming, are of different kinds. They may all, however, be reduced to two classes — the active and the passive ; the former, including those that require a muscular effort; and the latter comprising only one variety, — that in which the body is extended horizontally on the soil, and where no effort is necessary to maintain its position. We shall begin with the most ordinary attitude ; — that of stand- ing on both feet. This requires considerable muscular effort .to preserve equilibrium. The base of sustentation — being the space comprised between the feet plus that occupied by the feet them- selves — is small; whilst the centre of gravity is very high. The body, again, does not consist simply of one bone, but of many; all of which have to be kept steady by muscular effort; and it is ne- cessary that the vertical line shall fall within the base of susten- tation, in order that equilibrium may be preserved. » Recueil des Memoires de la Society Medicale de Paris, an. "vii. (1799,) and Ele- mens de Physiologie, 13eme edit, par M. B£rard, aine ; edit. Beige, p. 253, § clx., Bruxelles, 1837. b Physiologie de l'Homme, 2de £dit. ii. 117, Paris, 1829 ; and art, Dynamometre, in Diet, des Sciences Medicales. 396 MUSCULAR MOTION. That standing is the effect of the action of the different extensors is proved by the fact, that if an animal be killed suddenly, or stunned, so that volition is no longer exerted over the extensors, it immediately falls forward. The head, which is intimately united with the atlas or first verte- bra of the neck, forms with it a lever ofthe first kind, the fulcrum of which is in the articulation of the lateral parts of the atlas and vertebra dentata; whilst the power and the resistance occupy the extremities of the lever; and are situate — the one at the face, the other at the occiput. The fulcrum being nearer the occiput than it is to the anterior part of the face, the head has a tendency to fall forwards. This can be readily seen by supporting a skull on the condyles; yet Mr. Abernethya affirms, that " the condyles are placed so exactly parallel in the centre of gravity, that when we sit upright, and go to sleep in that posture, the weight of the head has a tendency to preponderate equally in every direction, as we see in those who are dozing in a carriage" ! In the living subject, the preponderance anteriorly is not as great as it is in the skeleton, because the greater part of the encephalon is lodged in the poste- rior portion ; but the fact, that when we go to sleep in the upright position the head drops forward, is sufficient evidence that it still exists ; and that in the waking state the head is kept in equili- brium on the vertebral column by the contraction of the extensor muscles of the head, which are situate at the back part of the neck, and are inserted into the head ; — as the splenius, complexus, tra- pezius, and posterior recti. These muscles are inserted perpen- dicularly into the lever or bone to be moved, which is an advan- tage, and some compensation for the shortness of the arm of the lever by which they act. In quadrupeds, the head, not being in equilibrium on the spine, Fig. 99. Ligamentum Nuchae. these muscles are very large and strong ; the spinous and trans- verse processes of the vertebrae and the occipital depressions are » Physiological Lectures, exhibiting a view of Mr. Hunter's Physiology, &c. Lect. 3, Lond. 1817. ATTITUDES. 397 larger; and, in addition, they have a strong ligament — the pos- terior cervical or ligamentum nuchse, (N, Fig. 99,)— which ex- tends from the spinous processes of the vertebrae to the occiput, and aids in supporting the head. The vertebral column supports the head, and transmits the weight to its lower extremity. The tendency of the column is to bear forwards: the upper limbs; the neck; the thorax with its contents; the greater part of the contents of the abdomen ; and the head itself, by reason of its tendency to fall forwards, all either directly or indirectly exert their weight upon it. Hence the ne- cessity for its great firmness and solidity, which are readily ap- preciated, if we examine the mode of junction of the different vertebrae, with the strong, ligamentous bands connecting them ; — the whole having the form of a pyramid, whose base rests upon the sacrum, with three curvatures in opposite directions, which give it more resistance than if it were straight, and enable it to support very heavy burdens, in addition to the weight of the organs pressing upon it. The tendency of the spine to fall forward is resisted by the extensor muscles, which fill the vertebral fossae or gutters—the sacro-lumbalis, longissimusdorsi, multifidus spinae, &c, which pass from the sacrum to the lower vertebrae of the spine, and from the lower to the upper. Each vertebra, in this action, constitutes a lever of the first kind ; the fulcrum of which is in the intervertebral cartilage ; the power in the ribs, and other parts that draw the body forwards; and the resistance in the muscles attached to the spinous and transverse processes. The vertebral column, regarded as a whole, may be considered a lever of the third kind; the fulcrum of which is in the union between the last lumbar vertebra and the sacrum, the power in the parts drawing the spine forwards, and the resistance in the muscles of the back. It is on the lower part of the lever that the power acts most forcibly ; and it is there, that the pyramid is thicker, and that the spinous and transverse processes are larger, and more horizontal. We can, accordingly, Fig. too. comprehend why fatigue should be experienced in the loins and sacrum, when we have been, for a long time, in the erect attitude. It need scarcely be said, that the longer and more horizontal the spinous processes, the greater will be the arm of the lever ; and the less the muscu- lar force necessary to produce a given effect. The weight of the whole ofthe upper part Of the body is transmitted tO the Lateral View of a Dorsal Vertebra. pelvis; Which, resting Upon the thigh l.Thebody. 6. Spinousprocess. 7. , • i .. Extremity of transverse process. 8 boiieS as Upon piVOtS, represents a Superior articular processes. 9 Info lever of the first kind, the fulcrum of rior articular p™****- vol. I. — 34 398 MUSCULAR MOTION. Fig. 101. Lateral View of a Lumbar Vertebra. 1. The body. 5. Spinous process. 6. Transverse process. 7. Superior articular processes. 8. Inferior articular processes. which is in the ilio-femoral articulations; the power and resist- ance being situate before and behind. The pelvis supports the weight of a part of the abdominal viscera; and the sacrum that of the vertebral column, which, by reason of its shape, transmits the weight equally to the ossa femorum,through the medium of the ossa ilii. When the pelvis is, therefore, in equili- brium on the heads of the thigh bones, this is owing to many causes. The abdominal viscera, pressing upon the anterior part of the pelvis, which is naturally inclined forwards, tends to depress the os pubis; whilst the vertebral column, by its weight, tends to press down the sacrum. As the weight of the latter is much more considerable than that of the former, muscles would seem to be required to keep it in equi- librium, as well as muscles passing from the femur to be inserted into the os pubis, by the contraction of which the excess of weight of the vertebral column may be counterbalanced. Such muscles do exist, but, as Magendiea remarks, they are not the great agents in producing the equilibrium of the pelvis on the thigh bones; for the pelvis, instead of having a tendency to be depressed posteriorly, would appear to bear forwards, inasmuch as the muscles, that re- sist the tendency which the spine itself has to bear forwards, have their fixed point on the pelvis; and, consequently, exert a considera- ble effort to draw it upwards. The strong glutaei muscles, which form the nates, and are inserted into the os femoris, are the great agents of the equipoise ; and as the hip-joint is nearer to the pubis than it is to the sacrum, these muscles act with a greater leverage. The thigh bones transmit the weight ofthe trunk to the tibia ; and here we see the ad- vantage ofthe neck of the thigh bone, which, as represented in Fig. 102, B, joins the shaft of the bone at a considerable angle. The trochanters D and C are for muscular attach- ments ; and are, of course, advantageous to the muscles, which are inserted into them. The cervix femoris directs the head of the bone, A, obliquely upwards and inwards, so that, whilst it supports the vertical pressure of the pelvis, it resists the separation of the ilia, which the pressure of the sacrum, with its su- perincumbent weight, has a tendency to produce. But another and important advantage is, that of affording additional strength in * Precis, &c, edit. cit. i. 296. Fig. 102. Upper Portion of Thigh Bone. ATTITUDES. 399 adventitious circumstances. When we are standing perfectly erect, the necks of the thigh bones are very oblique, compared with the line of direction of the body ; but if we are thrown forcibly to one side, the line of direction of gravitation corresponds more nearly with that of the neck of the thigh bone, and fracture is rarely pro- duced in this manner. The most common cause of fracture of the neck of the thigh bone is, slipping off a curbstone in towns, or unexpectedly slipping from a slight elevation, with one foot, upon a firm substance beneath ; and the fracture, in such case, is generally transverse. The advantage of this arrangement of the neck of the thigh bone has been compared not inaptly to that re- sulting from the dishing of a wheel; or the oblique position ofthe spokes from the nave outward to the felly, which strengthens the wheel so essentially, against the strains produced by the wheel sinking with force into a rut or other hollow.3 The femur trans- mits the weight of the body to the large bone of the leg — the tibia; but, from the mode in which the pelvis presses upon it, its lower extremity has a tendency to bear forwards. This is pre- vented by the action of the extensors of the leg— the rectus and triceps cruris — whose power is augmented by the presence of the patella, a sesamoid bone, seated behind their tendon. The muscles of the posterior part of the leg, which are attached to the condyles of the thigh bone, aid also in preserving the equilibrium. The tibia is the sole agent for the transmission of the superin- cumbent weight to the foot. Its upper extremity has, however, a tendency to bear forwards like the lower part of the os femoris. This is prevented by the contraction of the gastrocnemii, tibialis posticus, and the other muscles on the posterior part of the leg. The foot sustains the whole weight ofthe body; and its shape and structure are well adapted for the purpose. The sole has some extent, which contributes to the firmness of the erect attitude. The skin and epidermis are thick; and beneath the skin is a thick, adipous stratum, in greater quantity at the parts of the foot which come in contact with the soil. This fat forms a kind of elastic cushion, adapted for deadening or diminishing the effect of pres- sure. The whole of the sole of the foot does not come in contact with the ground. The weight is transmitted by the heel, the outer margin, the part corresponding to the anterior extremity of the metatarsal bones, and the extremities or pulps of the toes. The tibia transmits the weight to the astragalus ; and, from this bone, it is distributed to the others that compose the foot; but the heel conveys the largest share. When the foot rests upon a flat surface, it is entirely passive ; but when it is upon a slippery soil, the flexors of the toes, especially of the great toe, are firmly contracted, so as to fix the shoe, as far as possible, and render the attitude more stable. The use of shoes interferes largely with the exercise ofthe toes which, in the savage, are capable of diversified and considerable action. i See Fig. 80; also, Sir C. Bell, Animal Mechanics, p. 21, Library of Useful Knowledge, Lond. 1829. 400 MUSCULAR MOTION. The use of the fibula is, to serve, as its name imports, the pur- pose of a clasp. The tibia exerts its pressure chiefly towards the inner part ofthe foot, and, consequently, were it not'for the fibula, which passes down below the articulation, dislocation outwards would be constantly menacing us. The fibula has no participation in the transmission of the weight to the ground. The conditions for equilibrium, as applicable to man, have been already indicated. If the base of sustentation be rendered exten- sive in any one direction, by widely separating the feet, the attitude is more firm in one direction, but less so in the other. It is as firm as possible in every direction, when the feet are turned forwards in a parallel manner, and are separated by a space equal to the length of one of them. Whatever diminishes the base of sustentation, diminishes, in like proportion, the stability of the erect attitude. Hence the difficulty of walking on stilts or on wooden legs, on the toes,tightrope, &c. It seems that the inhabitants of Les Landes,3 in the southwest of France, are enabled by habit to use stilts with singular facility. The sandy plains, that bear this name, afford tolerable pasturage for sheep; but, during one part ofthe year, they are half covered with water; and during the remainder, they are very unfit walking ground, on account ofthe deep, loose sand, and thick furze. The natives, in consequence, habituate themselves to the use of stilts or wooden poles, the former of which are put on and off as regularly as the other parts of their dress. With these they walk readily over the loose sand or through the water, with steps eight or ten feet long. The difficulty, in this kind of progres- sion, does not arise solely from the smallness ofthe base of susten- tation, but from the greater height to which the centre of gravity is thrown which renders the equilibrium unstable. Standing on one foot is necessarily more fatiguing, as it requires the strong and sustained contraction of the muscles, which surround the hip-joint, to keep the pelvis in equilibrium on the os femoris ; especially as the body has a strong tendency to fall to the side that is unsupported. The muscles, that prevent the trunk from falling in this direction, are the glutaei, the gemelli, the tensor vaginae femoris, the pyramidalis, the obturators, and the quadratus femoris. The use of the neck of the thigh bone and of the great trochanter is here manifest. The base of sustentation, in this case, is the space occupied by the foot in contact with the soil simply; and it need hardly be said, that if this be still farther diminished, by attempting to stand on the toes, the attitude cannot be sustained. In the attitude on the knees, the centre of gravity is brought lower, but the base of sustentation is smaller than on the feet. The patella has to bear the chief pressure; and as it is not provided with such a fatty cushion as exists at the sole of the foot, the posi- tion becomes painful and the surface soon abraded. These remarks apply to the case, in which the knees only come in contact with the soil. When the feet are allowed to touch by the points of the toes, the attitude is much more easy and firm, as "the base of susten- » Arnott, Elements of Physics, 3d Amer. Edit. i. 15, Philad. 1835. ATTITUDES. 401 tation is largely augmented, — comprising the space between the knees and toes plus the space occupied by those parts. The sitting posture admits of variety, and is easily intelligible. In every variety in which the back is unsupported, the weight of the body is conveyed to the soil by the pelvis; and the broader this base the firmer the attitude. When we sit upon a stool without any back, and with the legs raised from the ground, the whole of the weight is conveyed by the parts in contact with the seat; but if the feet touch the ground, the weight of the lower extremities is transmitted to the soil by the feet, whilst the pelvis transmits that of the upper part of the body. In both these cases, if the attitude be long maintained, fatigue is felt in the back, owing to the con- tinued action of the extensor muscles in keeping the body erect. Sitting in an ordinary chair differs somewhat, in part of the body being supported. Fatigue is then felt in the neck, which is unsupported, and requires the sustained contraction of the extensor muscles of the head. To support all the parts, as far as possible, the long-backed chairs have been introduced, which sustain the whole body and head ; and, by being provided with rockers, a position approach- ing to the easiest of all attitudes can be assumed. To produce a similar effect in a common chair, the body is often thrown back until the chair rests on its hinder legs only. When the feet of the individual are on the ground, this position is stable ; the base of sustentation being large, and comprised between the legs of the chair and the feet of the individual, added to the space occu- pied by the parts themselves, that are in contact with the soil; but as soon as he raises his feet, the equilibrium is destroyed from the impracticability of making the vertical line fall within the base of sustentation, which is now reduced to the space occupied by the legs of the chair plus the space between them. In all the varieties ofthe sitting posture, equilibrium is facilitated by the centre of gravity being brought nearer .to the ground. Lastly. The horizontal posture is the only one that requires no muscular effort. Hence it is the attitude of repose and of the sick and the feeble. The base of sustentation is here extremely large ; and the centre of gravity very low. Accordingly, the atti- tude can be maintained for a long time; the only inconvenience being, that which results to the skin from prolonged pressure on those parts that chiefly convey the weight to the bed,—as the back of the pelvis, the region of the great trochanter, &c. — an inconvenience, which attracts the attention of the physician, more or less, in all protracted and consuming maladies. The reason, why we prefer soft, elastic beds, is not simply to prevent abrasion of those parts of the body that are most exposed to pressure, but to enable a greater portion of the body to transmit the weight; and thus to occasion a more equable partition of the pressure. There are numerous other attitudes, which may be assumed; as, that upon one knee, on the head, astride, &c.; but they do not 34* 402 MUSCULAR MOTION. need explanation, their physiology being obvious after what has been said. 6. MOVEMENTS. The movements, of which the body is susceptible, are of two kinds —partial and locomotive ; the former simply changing the relative situation of parts of the body ; the latter the relation of the whole body to the soil. Many of the partial movements con- stitute an inherent part of the different functions, and are consi- dered under those heads. In the erect attitude, whilst the body holds the same corre- spondence with the soil, the position of the upper parts of the body may be varied in all directions, provided the vertical line falls within the base of sustentation. Accordingly, to produce this effect, if the upper part of the body be inclined in one direction, the lower part will have to be thrown more to the opposite. The head may be turned forwards, backwards, or to one side ; and it is capable of a rotatory motion to the right and left. The three first movements occur in the articulation of the occipital bone and atlas, when they are slight; but if to a greater extent, the whole of the cervical vertebrae participate in them. The rota- tory motion is effected essentially in the articulation between-the first and the second vertebrae ; the latter of which has an arrange- ment admirably adapting it for this purpose. A tooth-like or odontoid process arises from its anterior part, on which the pos- terior surface of the anterior part of the atlas or first vertebra turns as on a pivot. This arrangement has obtained the second ver- tebra the name vertebra dentata : and its function, that of axis. Rotation to the right is effected by the contraction of the left sterno-mastoid and splenitis, and ofthe rightcomplexus,to the leftby the action of the opposite muscles of the same name. The motions of the head aid the senses of sight, hearing, and smell; and are useful in the production ofthe different vocal tones, by occasioning elongation or decurtation of the trachea and vocal tube. They are, likewise, inservient to expression. The spine, as a whole, and each of the vertebrae composing it, are capable of flexion, extension, lateral inclination, and circum- duction. These motions occur in the fibro-cartilages between the vertebrae; and they are more easy and extensive, in proportion to the thickness and width of the cartilages. This is one cause why the motions of the cervical and lumbar portions of the verte- bral column are freer than those of the dorsal. The interverte- bral substances ox fibro-cartilages possess a remarkable degree of elasticity. They yield somewhat, however, to prolonged pres- sure ; and hence, after long continuance in the erect attitude, our stature may be sensibly curtailed. We can thus understand, that at night we may be shorter than in the morning. Buffon asserts, that the son of one of his most zealous collaborateurs, M. Gue- neau de Montbeillard, — a young man of tall stature, — lost an inch and a half after having danced all night. The loss must MOVEMENTS. 403 be partly ascribed to the condensation ofthe adipous tissue beneath the foot. During the flexion of the spine, these cartilages are depressed on the side of the flexure, but they rise on the other ; and, by their elasticity, they are important agents in the restora- tion of the body to the erect position. Where they are thickest the greater extent of motion is permitted, and this is a cause, why the spine admits of the greatest motion anteriorly. In rotation, the whole is pressed upon and undergoes elongation in the direc- tion of its constituent laminae. In old age, the cartilages become shrivelled ; and this, with the loss of muscular power, is one of the causes why old people bend forwards. When we assume different positions with the trunk, the centre of motion of the vertebrae becomes modified. If we bend for- wards, it is thrown on the anterior part of the body of the verte- brae, if to one side, on the articulating processes, &c. Each vertebra, we have seen, is a lever of the first kind; and as the centre of motion becomes altered the leverage must be so likewise. It is when the body has been bent forwards, and the object is to re- store it to the erect position, that the power acts with the greatest advantage, — the fulcrum being thrown to the anterior partof the body of the vertebra, and the arm of the power being the dis- tance between' this point and the extremity of the spinous process, into which the power is inserted. Each vertebra has but a slight degree of motion; but the sum of all their motions is considerable ; and is estimated by multiply- ing the single motion by the number of vertebrae. The result, however, can only be regarded as approximate, as the extent of motion, of which the different vertebrae are capable, necessarily varies. The arrangement of the spinous processes of the verte- brae — especially of the dorsal — prevents any considerable flexion of the body backwards : and when we find the tumbler bending his body back until his head touches his heels, it is owing to the arrangement of the spine having been modified, in early life, by constant efforts of this kind, until there are no longer obstacles to the movement.. The motions of the vertebrae are frequently united to those of the pelvis on the thigh bones, so that they seem to be more extensive than they really are. This is the case, when we make a low bow. The motions of the spine are inservient to those of the head, and of the superior and inferior extremities. The upper limbs are capable of various motions ; some of which have been already described, and others will be hereafter. They are useful in the different attitudes ; and, at times, by transmitting to the soil a part of the weight of the body, and thus enlarging the base of sustentation, — as when we employ a stick, rest on the hands and knees, or support the head on one or both elbows. They are of great use, likewise, in preserving equilibrium when we walk on a very narrow base; serving in part the purpose of the pole, employed by the dancer on the tight rope. The lower extremities are, of course, locomotive organs; but 404 MUSCULAR MOTION. they are susceptible of partial movements likewise; as when we kick with one foot, try the consistence of the ground, cross the legs, tread the foot-board of a lathe, &c. Thus much for the attitudes. We shall now consider the mode in which the relation of the body to the soil is altered, comprising the physiology of walking, leaping, running, swimming, flying, &c, which constitute the different varieties of locomotion or progression. 7. LOCOMOTIVE MOVEMENTS. a. Walking. Walking is a motion on a fixed surface, the centre of gravity being alternately moved by one of the extremities and sustained by the other, without the latter being, at any time, completely off the ground. It consists of a succession of steps, which are effect- ed — in the erect attitude and on a horizontal surface — by bend- ing one of the thighs upon the pelvis and the leg upon the thigh, so as to detach the foot from the ground by the general decurta- tion of the limb. The flexion of the limb is succeeded by its being carried forward; the heel is then brought to the ground, and, suc- cessively, the whole ofthe inferior surface ofthe foot. If the bones of the leg were perpendicular to the part which first touches the ground, we should experience a Fis- 103. jolt, but, instead of that, the foot descends in an arc of a circle, the centre of which is the point of the heel. In order that the limb shall be thus carried forward, the pelvis must have described a movement of rotation on the head of the thighbone ofthe limb, which has Movement ofthe Foot in Walking. not been moved,and have carried forward the corresponding side of the body. As yet, only one limb has advanced.' The base of sustentation has been modified, but there has been no progression. The limb, remaining behind, has now to be raised and brought for- ward, so as to pass the other, or to be on the same line with it, as the case may be; and this finishes the step. In order to bring up the limb, which is behind, the foot must be successively detached from the soil, from the heel to the toe. In this way, an elongation of the limb is produced, which assists in advancing the correspond- ing side of the trunk, and excites the rotation of the pelvis on the head of the thigh bone first carried forward. A succession of these movements constitutes walking; the essence of which consists in the heads of the thigh bones forming fixed points, on which the pelvis turns alternately, as upon a pivot, describing arcs of circles, which are more extensive in proportion to the size of the steps. Walking in a straight line requires, that the arcs of circles de- WALKING. 405 scribed by the pelvis, and the extension of the limbs when carried forward, shall be equal; otherwise, the body will be directed to- wards the side opposite to that of the limb, whose movements are more extensive. Without the aid of vision, it would be imprac- ticable for us to make the arcs equal ; or, in other words, to walk straight forward. Walking backwards differs somewhat from this. The step is commenced by bending the thigh upon the pelvis, and, at the same time, the leg upon the thigh. The extension of the thigh on the pelvis succeeds, and the whole limb is carried backwards, the leg is afterwards extended upon the thigh, the point of the foot is brought to the ground, and the remainder of its under surface in succession. The other foot is then raised on its point, by which the corresponding limb is elongated; the pelvis, being pushed backwards, makes a rotation on the limb which is behind, and is, by the action of appropriate muscles, carried on a level with, or behind, the other, to afford a new pivot in its turn. Walking laterally is different from the two last in no arcs being described. In this case, one of the thighs is first slightly bent upon the pelvis, in order to detach the foot from the ground; the whole limb is then moved away by the action of the abductors, and is brought down to the ground. The other limb follows. If we walk up hill, the fatigue is much augmented; because the flexion of the limb, first carried forward, has to be more considera- ble ; and the limb, that remains behind, has not only to cause the pelvis to execute the movement of rotation, but it has to raise the whole weight of the body, in order to transport it upon the limb, which is in advance. To aid in throwing the weight forward, the body is bent forward, so that the centre of gravity may be as favour- ably disposed as possible; and the extensor muscles of the leg carried forward are powerfully contracted to raise the trunk; hence, the feeling of fatigue, which we experience in the knee and anterior part of the thigh, on ascending a long flight of stairs. Fatigue is likewise felt in the calf of the leg, on account of the strong efforts developed in extending the foot, and projecting the body forwards. Walking down hill is, also, more fatiguing than on level ground. In this case, there is a tendency in the body to fall forward; great effort is, consequently, required to keep the vertical line within the base of sustentation; and, accordingly, the muscles, employed in the extension ofthe head and vertebral column, experience fatigue. In all these kinds of progression, the character of the soil is a matter of importance. It must be firm enough to afford support to the limb that presses upon it, otherwise fatigue is experienced, and progression is slow and laborious. This occurs, whenever the soil is too soft or too smooth; the former yielding to the foot, and the latter presenting no inequalities, by which the foot can attach itself. The soil, too, has some influence, in particular cases, by virtue of its elasticity. Such, at least, is the opinion of Borelli ;a but Barthezb a De Motii Animalium, &c. Lugd. Bat. 1710. b Nouveaux Elemens de la Science de l'Homme, Paris, 1806. 406 MUSCULAR MOTION. thinks, that the inflnence of the soil is limited to the degree in which it furnishes a firm support. If the soil, again, be moveable, as the deck of a vessel, the line of gravity is apt to fall outside the base of sustentation; and to avoid this, the base is enlarged by sepa- rating the legs so as to give a characteristic air to the gait of the mariner; — and, lastly, if the base be very narrow, as on the tight rope, the steps are obliged to be rapid, and the arms are aided — in modifying the centre of gravity, as may be required — by the use of a long and heavy pole. b. Leaping? In the action of leaping, the whole body is raised from the ground; and is, for a short period, suspended in the air. If? consists, essen- tially, in the sudden extension of the limbs, after they have under- gone an unusual degree of flexion. Leaping may be effected direct- ly upwards, forwards, backwards, or laterally. In the ordinary case of the vertical leap, the head is slightly bent on the neck; the vertebral column is curved forwards; the pelvis is bent upon the thigh; the thigh upon the leg; and the leg upon the foot; the heel generally pressing but lightly on the soil, or not touching it at all. This state of general flexion is suddenly suc- ceeded by a quick extension of all the bent joints; so that the dif- ferent parts of the body are rapidly elevated, with a force surpass- ing their own gravity, and to an extent dependent upon the force developed. In this general muscular movement, the muscles that form the calf of the leg, and are inserted into the heel, have to deve- lope the greatest force, inasmuch as they have to raise the whole body, and to give it the impulse, which surmounts its gravity. They are, however, favourably circumstanced for the purpose ; — being remarkably strong; inserted perpendicularly into the heel; and having the advantage of a long arm of a lever. Figure 98 will show, that whenever the body is bent in the position it assumes preliminary to a leap, opposite impulses must be commu- nicated, by the restoration of the different parts to the vertical line B F. The leg B will tend to impel the body backwards, by fol- lowing the curved line C G. CD, on the other hand, by describing the curve D I, will tend to impel it forward; whilst the head and trunk, represented by the line D E, will describe the curve E F, and give an impulse backwards. Every vertical leap must, there- fore, be a mean between these different impulses, or rather the backward and forward impulses must destroy or neutralize each other; and that which is concerned in the elevation of the trunk be alone effective. In the forward leap, the movement of rotation of the thigh pre- dominates over the impulses backwards, and the body is projected forward. On the other hand, the impulses of the vertebral column, and of the leg on the foot prevail in the backward leap. The length of the lower limbs is favourable to the extent of the leap. The 1 J. Bishop, Cyclop. Anat. and Physiol. P. xxiii. p. 407, April, 1842. LEAPING. 407 forward leap, in particular, is greatly dependent upon the length of the femur, the part in which the forward impulse is situate. It does not appear, that any kind of impulse is communicated to the body by the surface on which we rest, at the moment of leap- ing, unless it be very elastic. In this last case, however, its reaction is added to the effort of the muscles, that occasion the elevation of the body; hence, the wonderful leaps of the performers in our circuses and on the tight rope. On the other hand, if the soil do not afford the necessary resistance, and do not yield to the feet, leaping is almost or wholly impracticable. The upper extremities are not without their use in leaping. They are brought close to the body, whilst the joints are bent, and are separated from it, at the moment when the body leaves the soil. By being held firmly in this manner, they allow the muscles, that pass from the os humeri to the trunk, to exert a degree of traction upwards, and thus to assist the extensors of the foot in the projec- tion of the body. It is with this view, that the ancients employed their «XTTjpsj, {halteres oxpoisers) in leaping; and that the moderns use bricks, stones, or other solid heavy bodies, with a like intent. It is likewise manifest, that by steadying the arms, and then moving them rapidly backwards, a backward impulse may be given to the upper part of the trunk. The effect of a run before we leap, is to add to the force — developed by muscular contraction — that of the impulse acquired by the body whilst running. The leap is, under such circumstances, necessarily more extensive. Some of the smaller animals surprise us by the extent of their leap. The jumping maggot, found in cheese, erects itself upon its anus, forms its body into a circle, by bringing its head and tail into contact, and, having contracted every part as much as possi- ble, unbends with a sudden jerk, and darts forward to an aston- ishing distance. Small animals, indeed, leap much farther than the larger in proportion to their size ; and, as Mr. Sharon Turner has remarked,a "exhibit muscular powers still more superior to those of the greatest animals than their comparative minds." He has given some amusing representations of this difference: for example, Linnaeus observes, that if an elephant were as strong in proportion as a stag beetle, he would be able to tear up rocks and to level mountains. A cock-chafer is, for its size, six times as strong as a horse.b The flea and the locust leap two hundred times their own length, as if a man should leap three times as high as St. Paul's.0 The cuckoo-spit froghopper will sometimes leap two or three yards, which is more than two hundred and fifty times its own length, as if a man should vault at once a quarter of a mile.d Mouffete relates, that an English mechanic made a golden chain as long as a finger, with a lock and key, which was dragged by a » Sacred History ofthe World, Amer. Edit. p. 372, New York, 1832. " Kirby and Spence's Introduction to Entomology, iv. 190. c Nat. History of Insects, i. 17. d Insect Transformations, v. 6, p. 179. e Theatr. Insect. 275. 408 MUSCULAR MOTION. flea; and Latreille3 mentions a flea of moderate size, dragging a silver cannon on wheels, that was twenty-four times its own weight. This cannon was charged with powder and fired, without the flea seeming to be alarmed. c. Running. This variety of progression consists of a series of low leaps, performed by each leg in alternation. It differs from walking, in the body being projected forward at each step, and in the hind- foot being raised before the fore-foot touches the ground. It is more rapid than the quickest walk, because the acquired velocity is preserved and increased, at each bound, by a new velocity. Running, therefore, cannot be instantaneously suspended, although a stop may be put to walking at any moment. In running, the body is inclined forward, in order that the centre of gravity may be in a proper position for receiving an impulse in that direction from the hind-leg; and the fore-leg is rapidly ad- vanced to keep the vertical line within the base of sustentation, and thus prevent the body from falling. There is, consequently, in running, a moment in which the body is suspended in the air. d. Swimming. Although Magendieb affirms, that the human body is, in gene- ral, specifically heavier than water, and that consequently, if left to itself in a considerable quantity of that fluid, it would sink to its lowest portion, the question respecting its specific gravity has not ,been rigorously determined ; and many eminent practical philoso- phers have even held an opinion the reverse of that of Magendie. Borellic accords with him ; and a writer of a later period, Mr. Robertson,d who details a set of experiments on this subject, seems to have originally coincided with him also. He weighed, how- ever, ten different individuals in water, comparing the weight with that of the fluid displaced by their bodies; and he affirms, that. with the exception of two, every man was lighter than his equal bulk of fresh water, and much more so than his equal bulk of sea water; — " consequently," he says, " could persons, who fall into water, have presence of mind enough to avoid the fright, usual on such accidents, many might be preserved from drowning." In corroboration of this inference, Mr. Robertson relates a circum- stance connected with his own personal knowledge. A young gentleman, thirteen years of age, little acquainted with swimming, fell overboard from a vessel in a stormy sea; but having had presence of mind enough to turn immediately upon his back, he remained a full half hour, quietly floating on* the surface of the water, until a boat was lowered from the vessel. He had used » Nouv. Diet. d'Histoire Natur. xxviii. 249, and Kirby, op. cit. b Precis Elementaire, i. 333. c \)e Motu Animalium, c. 23, de Natat. Prop. 217. d Philos. Transact, vol. 1.; and Dr. Dalton, in Manchester Memoirs, vol. x. SWIMMING. 409 the precaution to retain his breath, whenever a wave broke over him, until he again emerged. A case is given in the Rev. Mr. Maude's Visit to Niagara, in 1803, which is strikingly corroborative of Mr. Robertson's view of this matter. The author was on board a sloop on Lake Cham- plain, when a boy, named Catlin, who was on deck cutting bread and cheese with a knife, was knocked overboard by the captain jibbing the boom. He missed catching hold of the canoe, which was dragging astern, and an attempt of Mr. Maude's servant to untie or cut the rope, which fastened it, that it might drift to his assistance, also failed. Catlin was known to be unable to swim. It was in the night and very dark, and it was with difficulty that the captain, who considered that there was no hope of saving his life, was at last prevailed upon to go in the canoe to attempt it. He succeeded, however, in picking the boy up, and brought him on board again in about a quarter of an hour. " Catlin's relation," proceeds Mr. Maude, " almost exceeds probability. He had heard my exclamation to seize the canoe, which he was on the poiut of doing, when it gave a sudden swing and baffled him; but, finding he could support his head above water, he dismissed all fear, expecting that the canoe would come every moment to his assistance. When he no longer heard our cheers from the sloop, hope began to fail him, and he was on the point of resigning him- self to a watery grave, when he heard the captain's life-restoring voice. On telling Catlin that we despaired of his safety, as we understood that he could not swim, he replied; ' nor can I. I was never before out of my depth ; but I am fond of bathing, and have often seen lads what they call tread the water, that's what I did.' The truth of this account was made manifest, by the boy not only retaining his hat on his head, but its being perfectly dry ; and what adds to the singularity of this event, the boy never quitted his grasp of the knife, that he was eating his bread and cheese with." Knight Spencer found, that he was buoyant on the surface of the sea, when he held stones, weighing six pounds avoirdupois, in his hands. In the water, however, the stones lost two pounds five ounces in weight, so that he was really freighted with no more than three pounds eleven ounces. He himself weighed one hundred and thirty pounds.a Dr. Franklin,b again, whilst he con- siders the detached members of the body, and particularly the head, as of greater weight than their bulk of water, acknowledges the body, in the aggregate, to be of less specific gravity, by reason of the hollo wness of the trunk. He thinks, that a body, immersed in water, would sink up to the eyes, but that if the head were inclined back, so as to be supported by the water, the mouth and nostrils would remain above,— the body rising one inch at every inspiration, and sinking one inch at every expiration; and also, » Fleming's Philos. of Zoology, vol. i. Edinb. 1822. b Works, iii. 374, Philad. 1808; and Sparks's Edit. vi. 289, Boston, 1838. VOL. I.---35 410 MUSCULAR MOTION. that clothes give additional weight in the water, although, in step- ping out of it, the case is quite otherwise. He concludes, there- fore, that if a person could avoid struggling and plunging, he might remain in the posture described with safety. That the body is to a certain degree buoyant, he refers to the experience of every one, who has ever attempted to reach the bottom of deep water, the effort required sufficiently proving that something resists our sinking. The truth would appear to be, that there is only a slight dif- ference between the specific gravity of the human body and that of water; but that the former is something greater, otherwise there would be no reason, why the dead body should sink to the bottom, as it is known to do. It would seem, however, where the deposition of fat is excessive the body may be of less specific gravity than water.3 The old notion was, that, in the living state, the specific gravity of the body is decidedly less ; but that, in death from drowning, a quantity of water always enters the lung and stomach, and that thus, these cavities, being no longer occu- pied with air, the buoyancy is lost and the body sinks. Nothing is now better established than that no water gets into the stomach, except what is accidentally swallowed during the struggling, and, that no water must be looked for in the lungs; a quantity of frothy mucus being all that is generally perceptible there. Yet, in courts of justice, the absence of water in these situations has been looked upon as evidence, where a body has been found in the water, that death had not occurred from drowning; and attention has, consequently, been directed to other causes, which might have produced it; the presumption being, that the person had been first killed, and then thrown into the water for the pur- pose of averting suspicion. Another erroneous opinion, at one time prevalent, was, that if a person goes alive into water he will sink ; if dead, he will swim ; and that, therefore, it is necessary, that some weight should be attached to a body, when committed to the deep, to make it sink. All these fallacious notions are dwelt upon in a case, deeply in- teresting to all jurists, medical and others ; that of Spencer Cow- per,Esq., a member ofthe English bar, who, with three other in- dividuals, was tried at Hertford Assizes, in 1699, for the murder of Mrs. Sarah Stout.t> The speeches ofthe counsel, with the evi- dence of many of the medical witnesses, sufficiently testify the low condition of medico-legal knowledge at that period. Mr. Jones — the counsel for the prosecution — affirmed, that " when her (Mrs. Stout's) body came to be viewed, it was very much wondered at ; for, in the first place, it is contrary to nature, that any persons, that drown themseives, should float upon the water. We have sufficient evidence," he adds, « that it is a thing that never was : * See vol. ii. under Adipous Exhalation. " Hargrave's State Trials, vol. v.; Beck's Medical Jurisprudence, 6th edit. ii. 205, Albany, 1838. ' SWIMMING. 411 if persons go alive into the water, then they sink; if dead, then they swim." In confirmation of this strange opinion, two seamen were examined, one of whom deposed as follows: —" In the year '89 or 90, in Beachy fight, I saw several thrown overboard during the engagement, but one particularly I took notice of, that was my friend and killed by my side. I saw him swim for a considerable distance from the ship, &c. Likewise in another engagement, where a man had both his legs shot off and died instantly, they threw over his legs; though they sunk, I saw his body float; likewise I have seen several men, who have died natural deaths at sea ; they have, when they have been dead, had a considerable weight of ballast made fast to them and so were thrown over- board ; because we hold it for a general rule that all men swim if they be dead before they come into the water, and, on the con- trary, I have seen men when they have been drowned, that they have sunk as soon as the breath is out of their bodies," &c. The weights, are, however, attached to the dead, when they are thrown into the sea, not for the purpose of facilitating their descent, but to prevent them from rising, when putrefaction renders them buoyant, by the disengagement of air into the splanchnic cavities. On the same trial, Drs. Coatsworth, Burnet, Nailor, and Wood- house deposed, that when a person is drowned, water will be taken into the stomach and lungs, and, as none was found in the case of Mrs. Stout, they were of opinion, that she came to her death by other means. From all that has been said, it would appear, that the great re- quisite for safety to the inexperienced, who may fall accidentally into the water, is a firm and sufficient conviction of the fact, that the living body naturally floats, or that it can be easily made to do so. This conviction being acquired, no more than a common share of presence of mind would seem to be necessary to insure, that the portion of the body, which is the great outlet of the re- spiratory organs, shall be above the surface. The movements, adapted to the progression of the body, are to be acquired in the same manner as a child learns to walk; pro- ficiency in this, as in every thing else, being the result of practice. Swimming nearly resembles leaping, except that the effort in it does not take place from a fixed surface. Both the upper and lower extremities participitate in it. Whilst the former are brought to a point anterior to the head, and form a kind of cut- water, the lower extremities are drawn up and suddenly extended, as in leaping. The water, of course, yields to their impulse, but not as rapidly as it is struck, and hence the body is projected for- wards. The upper limbs are now separated, and carried circu- larly and forcibly round to the sides of the body, by which the impulse is maintained ; the legs, are in the mean time drawn up ; and, by a succession of these movements, progression is effected, the hands and feet being turned outwards to present as large a resisting surface as possible. The chest is, at the same time, 412 MUSCULAR MOTION. kept dilated, to augment the bulk of the body, and, of course, to render it specifically lighter, and the head is raised above the sur- face to admit of respiration. This action is analogous to that of the propulsion of a boat by oars. The body resembles the boat; and the upper and lower extremities are the oars or sculls. The practised swimmer can execute almost as many movements in the water as he can on land. e. Flying. If the human body sinks in water, how little can it be suscep- tible of suspension in the air by its own unassisted muscular powers. This is a mode of progression, which is denied to man; and, accordingly, most of the attempts at flying, since the mythi- cal exploits of Daedalus and Icarus, have been confined to ena- bling the body to move from one place to another, by means of ropes and appropriate adjuncts. Years ago, a native of this country exhibited a curious variety of progression, at Dover, Eng- land. He was called the " flying phenomenon.-" and his plan, so far as we can recollect, was to have a rope extending from the heights to the beach beneath, along which he descended, by means of rings attached to different parts of his person, which had the rope passing through them. The sources of difficulty, in flying, are ; — the great weight of the body, and the insufficient force, which the muscles are capa- ble of exerting. It is by no means impossible, however, that by some contrivance, of which the lightest gases might form a part, and by an imponderous apparatus, which would enlarge the surface of the upper extremities, progression, in this manner, might be effected;—but to a limited and unmanageable extent, only. f. Other Varieties of Muscular Action. Connected with this subject, we may refer, briefly, to some varieties of muscular action, the nature of which will be easily intelligible. In bearing a load, we have simply a variety of walking in the erect attitude, with this addition, that the extensor muscles of the head, neck, or back, — according to the part on which the burden may be placed, — have to contract forcibly to support it. The position of the individual has, also, to be so regulated, that the centre of gravity shall be always over the base of sustentation. Hence, if the load be on a man's back, he leans forward ; if borne before him, he leans backward; and this is the cause of the portly and consequential appearance of the corpulent. If the load be on his head, he stands as upright as possible, for a like reason. In propelling a body forwards, either by the hands or shoulders the feet are firmly fixed on the ground ; the limbs are in a state' of semi-flexion, and the centre of gravity is directed forwards, so as to aid the force that has to be developed by the muscles The limbs are then suddenly extended, the body is thrown for- OTHER VARIETIES OF MUSCULAR ACTION. 413 ward, and the whole power exerted on the obstacle which has to be moved. On the other hand, when we drag a weight after us, or attempt to dislodge a stake from the earth; the feet are equally fixed firmly on the ground, but the body is in a state of extension, and is directed as far as practicable backwards, in order that the tendency to fall, owing to the centre of gravity overhanging the base of sustentation, may aid the force that has to be developed by the muscle of the arms, which embrace the substance to be moved, or are attached to it indirectly. The flexor muscles are then power- fully contracted, and the whole force is exerted upon the object. As, in both these cases, there is danger of falling should the body yield suddenly, the feet are so placed as to obviate this, as far as possible; by being separated in the direction in which the force is exerted. Squeezing consists in laying hold of the object, either between the arms and body, or by the fingers; and then forcibly contract- ing the flexor muscles. In all these, and other varieties of strong muscular contraction, the respiration is interrupted, in order that the thorax may be rendered fixed, and serve as an immoveable point of origin for the muscles of the head, shoulders, and arms. This is effected by taking in a full inspiration; strongly contract- ing the respiratory muscles ; and, at the same time, closing the glottis to prevent the exit ofthe air. Lastly, as organs of prehension, the upper extremities are of ad- mirable organization: possessing great mobility; and, at the same time, solidity. The joint at the shoulder allows of extensive mo- tion ; and the bones, to which the arm is attached at this joint — the scapula and clavicle — are themselves moveable. The forearm is, likewise, susceptible of various movements on the arm, of which those of pronation and supination are not the least important; whilst the hand possesses every requisite for an organ of prehension. It is composed of numerous bones, and is capable of being applied to the most irregular surfaces. The great superiority of the human hand arises, however, from the size and strength of the thumb, which can be brought into a state of opposition to the fingers; and is, therefore, of the highest use in enabling us to seize hold of, and grasp spherical bodies; to take up any object; to lay firm hold of whatever we seize, and to execute the various useful, and ornamental processes of the arts. These processes require the most accurate, quick, and combined movements of the muscles. How quick for example is the motion ofthe hand in writing, and in executing the most rapid movements on the piano-forte ! How accurate the muscular contraction, which stops the precise part of the violin-string to bring out the note or semi-tone in allegro movements; and what a multitude of combinations must be in- voked in all these cases ! As an organ oftouch,the advantages ofthe upper extremity have 35* 414 MUSCULAR MOTION. already been depicted ; and much of what was then said applies to it as an organ of prehension. " In this double respect," observes Adelon,8 " man is the best provided of all animals. How much, in fact, does he stand in need of an ingenious instrument of prehen- sion ! As we have several times remarked, he has, in his organi- zation, neither the offensive nor defensive arms, that are bestowed on other animals. Naked from birth, and exposed to the incle- mencies of the atmosphere, without means of attack or defence against animals, he must incessantly labour to procure what he requires. It was not, consequently, enough that he should possess an intellect, capable of making him acquainted with, and of ap- propriating to himself, the universe. He must have an instrument adapted for the execution of all that his intellect conceives. Such instrument is his upper extremity. In short, whilst other animals find every thing in nature — necessary for their different wants — more or less prepared, man, alone, is obliged to labour to procure what he requires. He must make himself clothes, construct his habitations, and prepare his food. He is the labouring and pro- ducing animal,par excellence; and hence he needs not only an intellect to conceive, but an instrument to execute." 9. OF THE FUNCTION OF EXPRESSION OR OF LANGUAGE. Under this head will be included those varieties of muscular contraction, by which man and animals exhibit the feelings that impress them, and communicate the knowledge of such feelings to each other. It comprises two different sets of actions : — those that are addressed to the ear or the phenomena of voice: and those that are appreciated by the senses of sight and touch — or the gestures. Of these we shall treat consecutively. a. Ofthe Voice. By the term voice — or by phonation, a term proposed by Chaussier — is meant the sound produced in the larynx, whilst the air is passing through it, either to enter, or issue from, the trachea. 1. ANATOMY OF THE VOCAL APPARATUS. The apparatus, concerned in the production of the voice, is com- posed, in man, of the muscles concerned in respiration; of the larynx ; and of the mouth and nasal fossae. The first are merely agents for propelling the air through the instrument of voice. They will fall under consideration when we are on the subject of respira- tion ; whilst the anatomy of the mouth and nasal fossae have been, or will have to be, described in other places. The larynx, and its primary dependencies, which are immediately concerned in the production of voice, will, therefore, alone engage us at present. The larynx is situate at the anterior part of the neck, and forms a Physiologie de l'Homme, ii. 201, 2de e"dit. Paris, 1839. 1 VOICE — ANATOMY OF THE VOCAL APPARATUS. 415 the projection so perceptible in that ofthe adult male, called pomum Adami. An attentive examination of the various parts which compose it, so far as they concern its physio- logical relations, will be necessary : it will exhibit the imperfect know- ledge of several writers on the voice, and the false and insufficient views that have been entertained on the subject. If we look along the larynx from the trachea, of which it is a con- tinuation, we find that the tube becomes gradually narrower from side to side ; and at length, presents an oblong cleft, called the glottis, the sides of which are the essential organ of voice. The larynx is composed of four cartilages — the cricoid, thyroid, and arytenoid. The cricoid is the lowest of these, and is the inferior part of the organ ; —that by which it joins the trachea. It is shaped like a ring, whence its name, but is much deeper behind than before. The thyroid is situate above the cricoid, with which it is articulated in a moveable manner, by means of its inferior cornua. In this manner, the lower front margin ofthe thyroid, which is commonly separated by a short space from the upper margin of the cricoid, may be made to ap- proach to or recede from it; as may be readily ascertained by placing the finger against the small depression felt externally, and observing its change of size when various tones are sounded. It will be observed that the higher the tone the more the cartilages approximate, and that they separate in proportion to the depth of the tones. The thyroid is the large cartilage that occupies the anterior, prominent, and lateral part of the larynx. The arytenoid cartilages are two in number. They are much smaller than the others, and are articulated with the posterior partof the cricoid; — also, in a moveable manner. Around this articulation is a syno- vial capsule, — close before and behind, but loose within and with- out. Before it, is the thyro-arytenoid ligament; and, behind, a strong, ligamentous fascia, called, by Magendie,3 from its attach- ments— crico-arytenoid. Three fibro-cartilages likewise, form » Precis Elementaire, i. 235. External view of the Larynx. Os hyoides. 2. Lesser cornu of do. 3. Greater cornu of do. 4. Extremity of the epiglottis. 5. Hyo-thyroid membrane. 6. Thyroid cartilage, 7. Cricoid cartilage. 8. Trachea. 41g MUSCULAR MOTION. part of the constituents of the larynx. These are — the epiglottis, and two small bodies, that tip the arytenoid cartilages, and are met with only in man — the capitula Santorini or the supra-ary- tenoid cartilages, or the capitula cartilaginum arytenoidarum. Fig. 105. External and Sectional Views of the Larynx. An b, the cricoid cartilage; e c g, the thyroid cartilage; g, its upper horn; c, its lower born, where it is articulated with the cricoid ; r, the arytenoid cartilage ; e f, the vocal ligament; a k, crico-thyroideus muscle ;f em, thyro-arytenoideus muscle ; x e, crico-arytenoideuslateralis; s, trans- verse section of arylenoideus transversus; m n, space between thyroid and cricoid; b l, projection of axis of articulation of arytenoid with thyroid. — {Willis.) On examining the interior of the larynx, we discover, that there are two clefts, — one above the other ; the uppermost being usually oblong-shaped, ten or eleven lines long, and two or three broad, having the shape of a triangle, the apex of which is forwards. It is circumscribed, anteriorly, by the thyroid cartilage and epiglottis; posteriorly, by the arytenoid cartilages; and, laterally, by two folds of the mucous membrane, which pass from the epiglottis to each arytenoid cartilage, and are called the superior ligaments of the glottis, and the superior vocal cords. A few lines below this is a second cleft, also oblong from before to behind and of a trian- gular shape, the base of which is behind. It is bounded anteriorly by the thyroid cartilage ; posteriorly, by a muscle extending from one arytenoid cartilage to the other — the arylenoideus; and, laterally, by two folds, formed ofthe thyro-arytenoid ligament, pass- ing from the anterior part of the arytenoid cartilage to the poste- rior part of the thyroid, and of a muscle of the same name. These folds are called the inferior ligaments or lips of the glottis, or VOICE — ANATOMY OF THE VOCAL APPARATUS. 417 Fig. 106. the inferior vocal cords. They are represented by T V, in Fig. 106, and by B B, Fig. 107. Between these two clefts are the sinu- ses ox ventricles of the larynx, V V,Fig. 107. The inferior, exterior and superior sides of these are formed by the thyro-arytenoid muscle. By means of these ligaments — superior and inferior — the lips of the superior and infe- rior apertures are perfectly free, and unencumbered in their action.3 Anatomical descriptions will be found to give differ- ent significations to the word glottis. Some have applied it to the upper cleft, some to the lower; some, again, to the ventricles of the larynx ; and others to the whole space, comprised between the infe- rior ligaments and the top of the larynx. It is now, generally perhaps, restricted to the part of the larynx engaged in the production of voice, or usually considered to be so engaged, — that is, the space between the inferior ligaments with the ligaments themselves; and in this signification it will be employed by us. The mucous membrane, which lines the larynx, is continuous, above, with that of the mouth ; below, with that of the trachea. It contains several mucous follicles, some of which are agglomerated near the supe- rior ligaments of the glottis and the envi- rons of the ventricles of the larynx, seem- ing to constitute distinct organs, which have been called arytenoid glands. A similar group exists between the epiglottis behind, and the os hyoides and thyroid cartilage before, which has been termed the epiglottic gland. The uses of this body are not clear. Magendieb conceives, that it favours the frequent slidings of the thyroid cartilage over the posterior surface of the os hyoides ; that it keeps the epi View of Larynx from above. o e h, the thyroid cartilage, embracing the ring of the cricoid r u x w, and turning upon the axis x z, which passes through the lower horns, c. Fig. 105 ; n f, n f, the arytenoid cartilages, connected by the arytenoideus transversus; t v, t v, the vocal liga- ments ; n x, the right cricoarytenoideus lateralis (the left being removed): v kf the right thyro-aryte- noideus (the left being removed); n I, n I, the crico- arytenoidei postici; b b, the crico-arytenoid liga- ments. — {Willis.) Fig. 107. T Section ofthe Larynx. a Mr. Hilton, in Guy's Hospital Reports, No. v.for October, 1837, p. 519. b Precis, &c i. 237. 418 MUSCULAR MOTION. Fig. 108. glottis separated above from this bone; and, at the same time, furnishes it a very elastic support, which may aid it in the functions it has to exe- cute, connected with voice and degluti- tion. The larynx is capable of being moved as a whole, as well as in its component cartilages. It may be raised, depressed, or carried forwards or backwards. The movements, however, which are most concerned in the production of the voice, are such as are effected by the action of the intrinsic muscles, as they have been termed. These are, 1st. The crico-thy- roid, a thin, quadrilateral muscle, which arises from the anterior surface of the cricoid cartilage, and is inserted into the lower and inner border of the thyroid. Magendie3 affirms, that its use is not, as generally imagined, to depress the thy- roid on the cricoid, but to elevate the cri- coid and approximate it to the thyroid, and even to make it pass slightly under its inferior margin. The effects of its con- traction must be to render the vocal liga- ments tense. 2dly. The crico-arytenoidei postici, and the crico-arytenoidei late- rales ; the former of which pass frOm the posterior surface ofthe cricoid to the outer angle of the base of the arytenoid; and the latter from the upper border of the side of the cricoid to the outer angle of the base ofthe arytenoid. The use ofthe crico-arytenoidei postici is to carry the arytenoid cartilages backwards, separa- ting them at the same time from each other, and thus opening the glottis; the action of the crico-arytenoidei laterales is like that of the arytenoidei to bring to- „. . , gether the inner edges of the arvte- Ongin and Distribution of the Eighth0 • j t-, j i , aLyl* Pair of Serves. noid cartilages and close the glottis. 1,3,4. Medulla oblongata. 1. The corpus pyramidale of one side. 3. Corpus olivare 4 Cor- pus restiforme. 2. Pons Varolii. 5. Facial nerve. 6. Origin of the glosso-pharyngeal nerve 7. Ganglion of Andersch. 8. Trunk of the nerve. 9. Spinal accessory nerve. 10. Ganglion of the pneumogastric nerve. 11. Its plexiform ganglion. 12. Its trunk. 13. Its pharyngeal branch forming the pharyngeal plexus (14), assisted by a branch from the glosso-pharyngeal (6) and one fromi the superior laryngeal nerve (15). 16. Cardiac branches. 17. Recurrent laryngeal branch. 18. Anterior pulmonary branches. 19. Posterior pulmonary branches. 20. Oesophageal plexus ■il. Gastric branches. 22. Origin of the spinal accessory nerve. 23. Its branches distributed to the sterno-mastoid muscle. 24. Its branches to the trapezius muscle. —{Wilson.) » Precis, &c. i. 236. VOICE — ANATOMY OF THE VOCAL APPARATUS. 41 g 3dly. The arytenoid muscle — of which there is only one. It extends across from the arytenoid cartilage to the other; and, by its contraction, brings them towards each other. 4thly. The thyro-arytenoid muscle, which, according to Magendie,3 is the most important to be known of all the muscles of the larynx, as its vibrations produce the vocal sound. It forms the lips of the glottis, and Magendie describes it as constituting, also, " the infe- rior, superior, and lateral parietes ofthe ventricles ofthe larynx." Generally, it is considered to arise from the posterior surface of the thyroid cartilage, and the ligament connecting it with the cricoid, and to be inserted into the anterior edge of the base ofthe arytenoid. By drawing the point of the thyroid back, it must relax the vocal ligaments. Lastly. The muscles of the epiglottis —the thyro-epiglottideus, aryteno-epiglottideus superior, aryteno- epigloltideus inferior (Hilton's muscle)b and some fibres that may be looked upon as the vestiges of the glotto-epiglotticus, which exists in many animals. These muscles, — the position of which is indicated by the name, —by their contraction, modify the situa- tion ofthe epiglottis. The principal governors ofthe pitch ofthe voice, which is almost wholly regulated by the degree of tension of the vocal ligaments, are the crico-thyroid and thyro-arytenoid. The respective action of the different muscles has been given in a tabular form.c Govern the Pitch of the Notes. ., . , ... TDepress the front of the thyroid cartilage on the cricoid and rico-t vroi ei ) stretch the vocal ligaments; assisted by the arytenoideus Sterno-thyroidei ) , ., • . ■ ' J J J (_ and crico-arytenoidei postici. I Thyro-arytenoidei $ Elevate the front of the thyroid, and draw it towards the Thyro-hyoidei \ arytenoid, relaxing the vocal ligaments. Govern the Aperture ofthe Glottis. Crico-arytenoidei postici . . Open the Glottis. Crico-arytenoidei laterales . . C Press together the inner edges of the ary- ' Arytenoideus £ tenoid cartilage and close the glottis. The intrinsic muscles ofthe larynx receive their nervous influence from the eighth pair. (Fig. 108.) Shortly after this nerve has issued from the cranium it gives off a branch called the superior laryn- geal, which is distributed to the arytenoid and crico-thyroid mus- cles ; and, after its entrance into the thorax, it furnishes a second, which ascends towards the larynx, and is, on that account, called the recurrent ox inferior laryngeal. It is distributed to the crico- arytenoidei postici and crico-arytenoidei laterales, and to the thyro-arytenoid muscles. No ramification of this nerve, according to Magendie, goes to the arytenoid, or crico-thyroid muscles. In these views, he is supported by Cloquetd and many others. Other •■ Precis, &c. 236, and his Memoire sur l'Epiglotte. b Wilson's Anatomist's Vade-mecum, Amer. edit., p. 483, Philad. 1843. c Carpenter's Human Physiology, § 403, Lond. 1842. a Traite" d'Anatomie Descriptive, ii. 622, Paris, 1816, and Ley, in Appendix to Essay on Laryngismus Stridulus, p. 451, Lond. 1836. 420 MUSCULAR MOTION. distinguished anatomists, however, maintain that the arytenoidei muscles receive a filament from each of the inferior laryngeals.8 Dr. Reid asserts, that he has repeatedly satisfied himself ofthe existence of this arytenoid branch of the inferior laryngeal, and the dissection is one, he says, which can leave no kind of doubt on the matter.b In each animal species, the glottis has a construction correspond- ing to the kind of voice that has to be elicited ; and, when it is examined in a living animal — on dogs for example — it enlarges and contracts alternately,—the arytenoidcartilagesseparating when the air enters the lungs, and approximating during expiration. To the trachea the larynx is attached by a fibrous membrane, which unites the cricoid with the first ring of the trachea; and, above, it is connected with the os hyoides by a similar membrane — the hyo-thyroid, No. 5, Fig. 104, as well as by the thyro-hyoid muscle.0 PHYSIOLOGY OF THE VOICE. The production ofthe voice requires, that air shall be sent from the lungs, which, in passing through the glottis, may throw certain parts into vibration, and afterwards make its exit by the vocal tube — that is, by the mouth and nasal fossae. Simple expiration does not, however, produce it, otherwise we should have the vocal sound accompanying each contraction of the chest. Volition is necessary to excite the requisite action ofthe muscles ofthe larynx ; as well as those of respiration ; and by it the tone and intensity of the voice are variously modified. That the voice is produced in the larynx, we have both direct and indirect testimony. An aperture made in the trachea, beneath the larynx, deprives both man and animals of voice. This occurs also, if the aperture be made in the larynx beneath the inferior ligaments; but if made above the glottis, so as to implicate the epiglottis and its muscles, the superior ligaments of the glottis, and even the upper portions of the arytenoid cartilages, the voice con- tinues. Magendie,d and J. Cloquet refer to the cases of two men, who had fistulae in the trachea; and who were unable to speak unless the fistulous openings were accurately stopped by some mechanical means. If, again, we take the trachea and larynx of an animal or of man, and blow air forcibly into the tracheal ex- tremity towards the larynx, no sound is produced, except what i See Bichat, Traite d'Anatomie Descriptive, iii. 216; J. F. Meckel, Handbuch, u. s. w. and Jourdan's translation, iii. 66 ; Rudolphi, Grundriss der Physiologie, ii. 374; Swan's Demonstration of the Nerves, &c. PI. xvi. Fig. 7 ; and Cruveilhier, Anatomie Descriptive, iv. 963, Paris, 1835, cited by Dr. J. Reid, in Edinb. Med. and Surg. Journ. for Jan. 1838, p. 138. See, also, on the distribution of the superior laryngeal and recurrent nerves, C. E. Bach, in Muller's Archiv. fur Physiol. 1836, and Lond. Med. Gaz. May, 1837; and Mr. John Hilton, op. citat. b For an excellent description of the anatomy of the vocal apparatus, see J. Bishop, art. Larynx, Cyclop, of Anat. and Physiol., Sept. 1840. c Willis, in Cambridge Philosoph. Transact, for 1832, iv. 323. d Precis, &c. i. 241. See, also, his Journal de Physiologie, ix. 119. VOICE — PHYSIOLOGY. 421 results from the friction of the air against the sides of the larynx. But if we approximate the arytenoid cartilages, so that they touch at their inner surfaces, a sound will be elicited, bearing some resemblance to the voice of the animal to which the larynx be- longs ;a the sound being acute or grave according as the cartilages are pressed against each other with more or less force ; and varying in intensity, according to the degree of force with which the air is sent through the tube. In this experiment, the inferior ligaments can be seen to vibrate. Paralysis of the intrinsic muscles of the larynx likewise produces dumbness ; and this can be effected artificially. Much discussion at one time prevailed, regarding the effect of tying or cutting the nerves distributed to these muscles. The experiments of Haigh- tonb induced him to think, that the recurrent branches of the par vagum supply parts, which are essentially necessary to the forma- tion of the voice; whilst the laryngeal branches seemed to him to affect only its modulation or tone. Subsequent experiments have sufficiently shown, that if both the recurrent nerves and the supe- rior laryngeal be divided, complete aphonia must result. Magen- die0 found, indeed, that when both recurrents, —which he considers are distributed to the thvro-arytenoid muscles, — are cut, the voice is usually lost; whilst if one only be divided, the voice is but half destroyed. He noticed, however, that several animals, in which the recurrents had been cut, were still capable of eliciting acute sounds, when labouring under violent pain, — sounds, which were very analogous to those, that could be produced mechanically with the larynx of the dead animal, by blowing into the trachea and approximating the arytenoid cartilages; and this he attempts to explain by the distribution of the nerves to the larynx. The recur- rents being divided, the thyro-arytenoid muscles are no longer capable of contracting, and hence aphonia results; but the aryte- noid muscle, which receives its nerves from the superior laryngeal, still contracts, and, during a strong expiration, brings the arytenoid cartilages together, so that the chink or cleft of the glottis is suffi- ciently narrow for the air to cause vibration in the thyro-arytenoid muscles, although they may not be in a state of contraction. From these, and other experiments, Bellingerid infers, that the superior laryngeal nerve is the antagonist of the inferior laryngeal or recur- rent,— the former producing constriction, the latter dilatation of the glottis. They, however, who affirm, that the distribution of the laryngeal nerves is not the same as that described by Magendie and others, assign different functions to the particular nerves. Thus, Mr. Hilton,e infers from his observations —first, that the superior larvngeal nerve is a nerve of sensation; because, independently » Biot, Traite Etementaire de Physique, i. 462. b Memoirs of the Medical Society of London, iii. 435. «= Precis, &c. l. 243. a Ragionamenti, Sperienze, &c. comprovanti l'Antagomsmo Nervoso, &c, Torino, 1833 ; noticed in Edinb. Med. and Surg. Journal, p. 172, Jan. 1835. « Op. cit. p. 518, and Mr. Cock, on the Crico-Thyroideal Nerve, a branch ol the superior laryngeal, ibid. p. 313. vol. I. — 36 422 MUSCULAR MOTION. of the crico-thyroideal nerve, it is distributed exclusively to the mucous membrane, cellular tissue and glands; and secondly, that the inferior or recurrent nerve must be the proper motor nerve to the larynx, as it alone supplies all the muscles which act imme- diately upon the column of air passing to and from the lungs. Dr. Reid,a too, concludes from his various experiments,^?^/, that the superior laryngeal furnishes one muscle only with motor filaments,— the crico-thyroid. Secondly, that the superior laryngeal furnishes all, or at least, nearly all, the sensitive filaments of the larynx, and also some of those distributed upon the mucous surface of the pharynx. Thirdly, that the inferior laryngeal or recurrent furnishes the sensitive filaments to the upper part of the trachea, a few to the mucous surface of the pharynx, and still fewer to the mucous surface of the larynx ; and Fourthly, that when any irritant is ap- plied to the mucous membrane of the larynx in a healthy state, this does not excite the contraction of the muscles, which move the arytenoid cartilages by acting directly upon these through the mucous membrane, but the contraction takes place by a reflex action, in the performance of which, the superior laryngeal is the sensitive, and the inferior laryngeal the motor nerve. It is obvious from this discrepancy amongst observers, that we have yet much to learn before we can pronounce with certainty on the precise function of those nerves. Every part ofthe larynx, with the exception ofthe inferior liga- ments may be destroyed, and yet the voice may continue. Bichat split the upper edge of the superior ligaments of the glottis, without the voice being destroyed; and the excision of the tops of the arytenoid cartilages had no more effect. Magendie divided, with impunity, the epiglottis and its muscles, and voice was accomplish- ed, until he cut the middle of the arytenoid cartilages or split the thyroid cartilages longitudinally, when he, of course, destroyed the glottis. Lastly, when the larynx is exposed in a living animal, so that the different parts can be readily seen at the time when voice is accomplished, — the superior ligaments, according to Bichat and Magendie, who have performed the experiment, are manifestly unconcerned in the function, whilst the inferior ligaments distinctly vibrate. These ligaments must, therefore, be regarded as the essen- tial organs of voice.b The interesting, but difficult problem now presents itself; to de- termine the precise mechanism of the vibration of those ligaments; and what kind of instrument the vocal organ must be regarded. The latter question, on which, it might be conceived, so much physical evidence must exist, has been a topic of dissension, and is by no means settled at this day. Aristotle,0 Galen,d and the older writers in general, looked upon the larynx as a wind instrument of the flutee kind, in which the interior column of air is the sono- rous body; the trachea, the body of the flute, and the glottis the a Op. cit. p. 145. b Precis &c. i. 242. c Opera, lib. ii. Problemat. § xi. a Opera : de Larynge, lib vii. e The flute, here alluded to, is the common flute or fltUe a bee, in which the em- bouchure is at one extremity. VOICE — MECHANISM. 423 beak. The air, they conceived, when forced from the lungs, in passing through the glottis or beak, is broken by the inferior liga- ments of the larynx; vibrations are, consequently, produced, and these vibrations give rise to the sound. Fabricius, of Acqua- pendente,a was one of the first to object to this view of the subject. He properly remarked, that the trachea cannot be regarded as the body of the flute, but as a porte-vent to convey the air to the glottis. He was of opinion, that the glottis corresponds to the beak of the flute, and that the vocal tube or all that part above the glottis resem- bles the body of the instrument. Similar opinions, with more or less modification, have been adopted by Blumenbach,b Sommer- ing,0 Savart,*1 &c. About the commencement of the last century, Dodarte laid before the Academic des Sciences of Paris, three memoirs on the theory of the voice, in which he considered the larynx to be a wind instrument of the horn, and not of the flute, kind ; the inferior ligaments of the glottis being to the larynx what the lips are to the performer on the horn. In 1741, Ferrein/ in a. communication, also made to the Academie des Sciences, maintain- ed, that the larynx is a stringed instrument; — the sound resulting from the oscillation caused in what he called the cordse vocales or the inferior ligaments of the larynx by the air in expiration ; and a modification of this view was professed by Dr. Young.s At the present day, the majority of physiologists and natural phi- losophers regard the larynx as a wind instrument, but of the reed kind ; such as the clarionet, hautboy, &c, and they differ chiefly from each other, in explaining the various modifications of the tone and quality ofthe voice ; for almost all are agreed, that it is produced by the vibrations of the inferior ligaments of the glottis.h Piorry, and Jadelot consider the glottis to be an instrument sui generis, eminently vital, and which, of itself, executes the movements necessary for the production of vocal sounds ; but all we know of the physiology ofthe production of the voice is— that the expired air is sent into the larynx by the muscles of expiration, — that the intrinsic muscles of the larynx give to the inferior ligaments suffi- cient tension to divide the air, and that the air receives the vibra- tions, whence sound results. The process is, however, very complex. Before a single word can be uttered, a series of actions must be executed : these, as stated by Sir C. Bell,1 consist in the compres- sion of the chest, the adjustment of the glottis, the elevation and depression of the larynx, and the contraction of the pharynx,— actions which will be readily understood after what has been already said on the mechanism of phonation. a De Locutione, &c. in Oper. Lugd. Bat. 1737. b Physiology by Elliotson, 4th edit. p. 140, Lond. 1828. c Icones Organorum Gustus et Vocis, Francof. 1808 ; and Corp. Human. Fabric. vi. 93. d Journal de Physiologie, v. 367. e Memoir, de l'Acad. Royale des Sciences, 1700, p. 244 & 1707, p. 409. f Ibid, for 1741, p. 409, and Haller, Elem. Phys. ix. 3. e Lectures on Natural Philosoph. i. 400, and Philos. Trans, for 1800, p. 141. h Mr. Willis, in Cambridge Philosophical Transactions, vol. iv. > Philos. Transact, for 1832, p. 299 ; and Nervous System, 3d edit. Lond. 1837. 424 MUSCULAR MOTION. 1. Intensity or Strength ofthe Voice. The strength of a sound depends upon the extent of the vibra- tions of the body producing it. In the case of the voice, it is partly dependent upon the force with which the air is sent from the lungs, and partly on the size of the larynx. A strong, active person, with a capacious chest and prominent pomum adami,— in other words, with a large larynx, — is of an organization the most favourable for a strong voice. But if this same individual, thus favourably organized, be reduced in strength by sickness, his voice is enfee- bled; because, although the formation of his larynx may be favour- able, he is incapable of sending the air through it with sufficient force to excite extensive vibrations of the vocal ligaments. The voice of the male is much stronger than that of the female, of the eunuch, or of the child. This is greatly owing to his larynx being more developed. The change of the voice in the male at puberty is owing to the same cause,— the prominence ofthe pomum adami, which is first observed at this age indicating the elongation, which has supervened in the lips of the glottis. As voice is com- monly produced, both ligaments of the glottis participate; but if one should lose its power of vibrating, from any causes, as from paralysis of one-half the body, the voice loses, cseteris paribus, one-half its intensity. Magendie3 affirms, that this is manifested by cutting one of the recurrents of a dog. 2. Tone of the Voice. Nothing can exceed the human organ of voice in variety of tones, and in execution. Dr. Barclaybhas endeavoured to calculate the dif- ferent changes of which it is susceptible, proceeding on the principle, that where a number of moveable parts constitute an organ destined to some particular function, and where this function is varied and modified by every change in the relative situation of the moveable parts, the number of changes, producible in the organ, must at least equal the number of muscles employed, together with all the combinations of which they are capable. The muscles, proper to the five cartilages of the larynx, are, at least, seven pairs; and fourteen muscles, that can act separately or in pairs, in combina- tion with the whole or with any two or more of the rest, are esti- mated to be capable of producing upwards of sixteen thousand different movements — not reckoning as changes the various de- grees of force and velocity, with which they are occasionally brought into action. These muscles, too, are only the proper muscles of the larynx, or the muscles restricted in their attach- ments to its five cartilages. They are but a few of the muscles of voice. In speaking, we use a great many more. Fifteen pairs of different muscles, attached to the cartilages, or to the os hy- oides, and acting as agents, antagonists, or directors, are constantly a Precis, &c. i. 245. b The Muscular Motions of the Human Body, Edinb. 1808. VOICE — TONE. 425 employed in keeping the cartilages steady, in regulating their situation, and moving them as occasion requires — upwards and downwards, backwards and forwards, and in every intermediate direction, according to the course of the muscular fibres, or in the diagonal between different fibres. These muscles, independently of the former, are susceptible, it is calculated, of upwards of 1073,841,800 different combinations; and, when they co-operate with the seven pairs of the larynx, of 17592186,044,415 ; exclu- sive of the changes that must arise from the different degrees of force, velocity, &c, with which they may be brought into action. But these muscles are not the whole that co-operate with the larynx, in the production of the voice. The diaphragm, the abdominal muscles, the intercostals, and all, that directly or indi- rectly act on the air, or on the parts to which the muscles of the glottis or os hyoides are attached, — in short, all the muscles that receive nerves from the respiratory system of Sir Charles Bell, — contribute their share. The numerical estimate would, conse- quently, require to be largely augmented. Mr. Bishop computes the number of muscles brought into action at the same time in the ordinary modulations of the voice to be one hundred.* Such calculations are, of course, only approximate, but they show the inconceivable variety of movement of which the vocal apparatus is directly or indirectly susceptible. The tone of the voice has been a great stumbling-block to the physiologist and natural philosopher. The mode, in which it is produced, and the parts, more immediately concerned in the func- tion, have been the object of the various theories or hypotheses, from time to time enunciated regarding the voice. Galen, under his theory, that the larynx is a wind instrument of the flute kind, of which the glottis is the beak and the trachea the body of the flute, ascribed the variety of tones to two causes — to variation in the length of the musical instrument and in the embouchure. In the theory of Dodart, in which the human vocal instrument was likened to a horn, the inferior ligaments of the glottis being compared to the lips ofthe performer, no importance was attached to variation in the length of the instrument. He attributed the variety of tones to simple alteration in the embou- chure or mouth-piece ; in other words, to changes in the size of the glottis, by the action of its appropriate muscles ; and the rising and falling of the larynx, he regarded as serving no other purpose than that of influencing, mechanically, the size of the aperture of the glottis; whilst Ferrein, who regarded the larynx as a stringed instrument, accounted for the variety of tones by the different degrees of tension and length of the inferior ligaments of the glottis or of the vocal cords. In the production of acute tones, these cords were stretched and shortened. For grave tones, they were relaxed, and, consequently, longer. He was of opinion, that the length of the vocal tube had no influence on the tone. In later years, i The London and Edinburgh Philosoph. Magazine, &c, for Sept. 1836, p. 209. 36* 426 MUSCULAR MOTION. several new views have been propounded on this subject, and chiefly by Cuvier, Dutrochet, Magendie, Biot, Savart, &c. — men of the highest eminence in various departments of physical science. Cuviera attributes the variety of tones, in the first place, to the varied length of the vocal tube, and to differences in the size of the aperture of the glottis ; and, secondly, to the shape and con- dition of the external aperture of the tube — that is, of the lips and nose. The larynx he regards as a wind instrument, in which the inferior ligaments act, not as cords, but like the reed of a clarionet, or the lame of an organ pipe. The lungs and their external mus- cular apparatus constitute the reservoir of air and the bellows; the trachea conducts the air, and the glottis is the embouchure with its reed; the mouth and the whole of the space,comprised between the glottis and the opening of the lips, being the body of the instrument; whilst the openings of the nostrils are lateral holes, which permit the size of the instrument to be varied. The tones are changed by three causes, of a similar character to those that modify them in musical instruments; — the length of the body of the instrument, the variableness of the embouchure, and of the aperture at the lower extremity of the instrument. The condition of the external aperture of the vocal tube has, doubtless, much to do with the character of the tone produced by the glottis ; but its influence appears to be greatly limited to giving it rotun- dity, volume, or the contrary, as will be seen hereafter ; although analogy would seem to show, that the tone may be varied by more or less closure of the aperture. Many different notes can be produced in the first joint of a flute, if we modify the size of the opening at its extremity by passing the thumb more or less within it. It is doubtful, however, whether in man the altered size of the external aperture or the elongation or decurtation of the tube exert as much influence in the production of acute or grave sounds as Cuvier imagines. Dutrochet,b again, believes, that the vocal tube has no influence in the production of tones, and that the larynx is a simple vibra- ting instrument, uncomplicated with a tube, the vocal sound being caused by the vibrations into which the vocal cords are thrown by the impulse of the expired air. In his experiments, he saw the inferior ligaments vibrate ; and he concludes, that the tone of the voice depends upon the number of vibrations of these liga- ments in a given time, and that the number will necessarily vary considerably, as the dimensions of the ligaments, — that is, their length and thickness,—and their elasticity, are susceptible of incessant changes, by the contraction of the thyro-arytenoid muscle, of which they are essentially composed, — the ligament, covering the muscle, serving only " to prevent the collisions of the * Lecons d'Anatomie Comparee, torn. iv. 445. >> M6m. pour servir a l'Histoire Anat. et Physiol, des Vegetaux et des Animaux, t. ii. Paris, 1837 ; and Adelon, Physiologie de l'Homme, £dit. cit. ii. 239. VOICE—TONE. 427 muscles at the time of vibration," — as well as by that of the other intrinsic muscles of the larynx. MM. Biot and Magendie8 dissent from Dutrochet in some im- portant points. Like him, they do not consider the human larynx to constitute a stringed instrument. They regard it as a variety of reed instrument, but they consider the vocal tube to be of moment in the production of the voice. The objections they urge, against the view of its resembling a stringed instrument, are, — not only the kind of articulation between the arytenoid and cricoid cartilages, which admits of motion inwards and out- wards only ; but they ask how the vocal cords can retain the length they would require for the production of grave tones; and how these cords could elicit sounds of a volume so considerable as those of the human voice. They esteem it, consequently, as a reed instrument — of such nature as to be capable of affording very grave tones with a pipe of little length ; and such that the same tube, almost without varying its length, is susceptible, not only of furnishing a certain series of sounds in harmonic progression, but all the imaginable sounds and shades of sounds, in the compass of the musical scale which each voice embraces. The theory of the reed instrument MM. Biot and Magendie apply to the human vocal apparatus. The lips of the glottis are the reed, and the thyro-arytenoid muscles render them fit for vibrating. In his experiments, made on living dogs, Magendie saw, that when grave sounds were produced, the ligaments of the glottis vibrated in their whole extent, and the expired air issued through the whole of the glottis. In acute sounds, on the other hand, they vibrated only at their posterior part, and the air passed out through the part only that vibrated, the aperture being, con- sequently, diminished ; and, when the sounds became very acute, the ligaments vibrated only at their arytenoid extremity, and scarcely any air issued; so that tones beyond a certain degree of acuteness, cannot be produced in consequence of the com- plete closure of the glottis. The arytenoid muscle, whose chief use is to close the glottis at its posterior extremity, he conceives to be the principal agent in the production of acute sounds, and this idea was confirmed by the section of the two laryngeal nerves, that give motion to this muscle, which was followed by the loss of the power of producing almost all the acute tones; the voice, at the same time, acquiring a degree of habitual graveness, which it did not previously possess. The influence of contraction of the thyro-arytenoid muscles on the tones, he properly considers, is exerted in increasing or diminishing the elasticity of the ligaments, and thus, in modifying the rapidity of the vibrations, so as to favour the production of acute or grave tones. He thinks, too, that the contraction of these muscles concurs greatly in closing, in part, the glottis, particularly its anterior half; although the course of its fibres, it appears to us, ought rather to widen the » Precis Elementaire, &c. i. 248. 428 MUSCULAR MOTION. aperture. The trachea or porte-vent has usually been thought to exert no influence on the nature of the sound produced. It has been conceived, however, by Grenie and others, that its elongation or decurtation may occasion some modification. Thus much for the reed : — MM. Biot and Magendie, however, include, in their theory of the voice, the action of the vocal tube, likewise. This tube, being capable of elongation and decurtation, of being dilated or contracted, and susceptible of assuming an infinite number of shapes, they think it well adapted for fulfilling the functions of the body of a reed instrument, — that is, if placed in harmonic relation with the larynx, — and thus of favouring the production of the numerous tones of which the voice is capable 'y of augmenting the intensity of the vocal sound by assuming a conical shape with a wide external aperture; of giving rotundity and sweetness by the proper arrangement of its external outlet, or of entirely subduing it by the closure of the outlet. The larynx rises in the production of acute sounds; and falls in that of grave. The vocal tube is, consequently, shortened in the former case ; elongated in the latter. It experiences also a simultaneous change in its width. When the larynx descends, — in other words, when the vocal tube is elongated, the thyroid cartilage is depressed and separated from the os hyoides by the whole height of the thyro- hyoid membrane. By this separation, the epiglottic gland is carried forwards, and lodged in the concavity at the posterior sur- face of the os hyoides. The gland drags after it the epiglottis ; and a considerable enlargement in width occurs at the inferior part of the vocal tube. The opposite effect results when the larynx rises. The use of the ventricles of the larynx, Magendie3 considers to be, to isolate the inferior ligaments, so that they may vibrate freely in the air. Lastly, in this theory the epiglottis has a use assigned to it which is novel. In certain experiments, insti- tuted by Grenieb for the improvement of reed instruments — being desirous of increasing the intensity of sound without chang- ing the reed in any respect, he found, that to succeed in it he was compelled to augment gradually the strength of the current of air ; but this augmentation,by rendering the sounds stronger, made them rise. To remedy this inconvenience, Grenie found no means answer, except that of placing obliquely in the tube, immediately below the reed, a supple, elastic tongue^nearly as we see the epi- glottis above the glottis. From this, Magendie0 infers, thaUthe epiglottis may assist in giving to man the faculty of increasing or inflating the vocal sound, without its mounting; but, as Mr. Bishop*1 properly remarks, neither the elevation nor depression of the epiglottis can affect or regulate the vibrations of the glottis. Such are the main propositions of the theory of the voice by » Precis, &c. i. 252 ; see, also, Sir C. Bell, Philos. Transact, for 1832 ; and Nervous System, 3d edit. p. 484, Lond. 1837. b Biot, Precis Elementaire de Physique, p. 399. • Ibid. i. 252. 4 London and Edinburgh Philosophical Magazine, p. 205, for Sept. 1836. VOICE — TONE. 429 Biot, and Magendie. The larynx represents a reed with a double tongue; the tones of which are acute, in proportion to the decur- tation of the laminae; and grave in proportion to their length. They admit, however, that, although the analogy between the organ of voice and the reed is just, the identity is not complete. The ordinary reeds are composed of rectangular laminae; fixed at one side, but loose on the three others; whilst, in the larynx, the vibrating laminae, which are likewise nearly rectangular, are fixed by three sides and free by one only. Moreover, the tones of the ordinary reed can be made to rise or to descend by varying its length, whilst in the laminae of the larynx the width varies. Last- ly, say they, in musical instruments, reeds are never employed, whose moveable laminae can vary in thickness and elasticity every moment, as is the case with the ligaments of the glottis ; so that, although we may conceive, that the larynx can produce the voice and vary its tones, in the manner of a reed instrument, we are unable to demonstrate the particulars of its mode of action. All the more modern theories — detailed above, at more or less length — agree, then, in considering the larynx to be a wind instru- ment and of the reed kind; they differ, chiefly, in the part which they assign to the vocal tube in causing the variation of tones. M. Savarta has propounded a theory of the human voice, in which he differs from Cuvier, Dutrochet, and Magendie ; — denying that the mechanism of the voice resembles that of the reed instru- ment, and returning to the old idea, which referred the vocal organ to an instrument of the flute kind. The sounds of the human voice have, he remarks, a peculiar character, which no musical instru- ment can imitate; and this must necessarily be the case, as they are produced by a mechanism founded on principles, which do not serve as a basis for any of our instruments. He conceives, that the production of the voice is analogous to that of the sound in the tube of a flute, and that the small column of air, contained in the larynx and mouth, by the nature of the elastic parietes which bound them, as well as by the mode in which it is thrown into vibrations, is susceptible of rendering sounds of a particular nature, and, at the same time, of a much more grave character than the dimensions would seem to admit. In the tube of a flute, the column of air within is the sonorous body. A sound is first produced at the embouchure of the instru- ment, by the division, which the air experiences when blown into it; and this sound excites similar sonorous undulations in the column of air, which fills the tube. The sound, resulting in this way, is more grave in proportion to the length of the tube; and in order to vary its tones, the instrument has apertures in its sides, by means of which the length may be modified. In assimilating the human vocal apparatus to a flute, the great difficulty has been to explain how, with so short a tube as the » Journal de Physiologie, v. 367, Paris, 1825 ; and Annates de Physique et de Chimie, xxx. 64, and xxxii. 430 MUSCULAR MOTION. Fig. 109. Fig. 110. vocal tube in man, and one so little variable in length, tones so different, and especially so grave, can be produced. To account for this, Savart establishes the existence of a number of physical facts, previously unknown or unnoticed. In organ pipes of great length, the velocity of the current of air, which acts as a motor, has but little influence on the number of oscillations. When the length of the pipe is, for instance, twelve or fifteen times greater than its diameter, it is difficult to vary the sound a semitone. When the air is forcibly driven in, it rises an octave; and, when the velocity is diminished, the sound becomes more feeble; but is depressed an almost imperceptible quantity. In short pipes, on the contrary, the influence of the velocity of the current of air is much greater, and several tones can be elicited. The bird-call used by sportsman, is illustrative of this principle. It is a small instrument, employed for imitating the notes of certain birds ; consisting of a cylindrical tube, about three-fourths of an inch in diameter, and a third of an inch high ; closed at each end by a thin, flat plate, which is pierced, at its centre, by a hole about the sixth of an inch in diameter. Sometimes, it has the shape represented in the lower of the marginal figures. By placing this instrument between the teeth and lips, and forcing air, with more or less strength, through the two apertures, dif- ferent sounds can be produced. This is more certainly effected, by attaching a porte-vent to the whistle, as A A, Fig. 110, when it is capable of producing all the sounds comprised in [an extent of from an octave and a half to two octaves. M. Savart found, that, other things being equal, the diameter ofthe apertures has4an appreciable influence on the acuteness or grave- ness of the sounds, which are more grave when the orifices are larger. The nature of the parie- tes of the instrument appeared, also, to exert some effect on the number of oscillations, and on the quality of the sounds ; and if, in the hemispheral whistle, Fig. 110, the plain plate was replaced by a thin leaf of some extensible substance, as parchment, the sounds issued more rapidly, and were usually more grave, full, and agreeable, than when they were formed of a more solid substance. It is an opinion generally admitted, that the material, which composes an organ pipe, has no influence on the number of vibra- tions, which the column of air, contained in it, is capable of exe- cuting. This is true as regards long pipes; but, according to Savart, it is not so with the short, and the nature of the bisea u* * The biseau or languette is the diaphragm placed between the body of an organ pipe and its foot. A.\ Sections of a Bird-call. VOICE—TONE. 431 he conceives, may have a great influence, even on the sound of long pipes. For instance, if we substitute, for the stiff lamina, which forms the biseau of an organ pipe two feet long and two inches on the side, a lamina, formed of some elastic substance, as skin or parchment, and so arranged as to admit of being stretched at pleasure—by gradually increasing the tension ofthe membrane, at the same time that we increase the velocity of the current of air, the tone may be made to vary a fourth, and even a fifth. In still shorter tubes, the much greater influence of the velocity of the current of air being united to that of the tension of the biseau, the result is still more evident. Thus, the sound of a cubical tube may easily be lowered an octave, when the parietes of the biseau are"susceptible of different degrees of tension; but when all the parietes, which compose a short pipe, are of a nature to enter into vibration along with the air they contain, and when their degree of tension can be, moreover, varied, they have such an influence on the number of vibrations, that the sound may be greatly modi- fied. Short tubes, open at both extremities, and formed of elastic parietes, are also susceptible of producing a great number of sounds, even when they are only partly membranous, and the quality of the sound of membranous tubes is said to be somewhat peculiar; partaking of that of the flute, and of the free reed. Again, in order that a mass of air shall enter into vibration, a sound must be pro- duced in some part of it. In an organ pipe, for example, a sound is first excited at the embouchure, and this throws the column of air, within the instrument, into vibration. Every sound, indeed, produced at the orifice of a column of air, throws it into vibration, provided its dimensions be adapted to the length of the waves produced directly : — hence the utility of a musical pipe having parietes susceptible of varying in dimension and in tension, what- ever may be the character of its embouchure. Lastly.—The funda- mental note of a tube closed at one end, and whose diameter, is every where the same, is an octave lower than the sound of the same tube, when open at both extremities. But this is not the case with tubes that are of unequal diameter,conical and pyramidal, ^ &c, when made to vibrate at their narrowest part. The tone' produced in such case will increase in graveness, according to the difference between its narrow and expanded portions. These different physical conditions Savart invokes to account for the different tone of the human voice, — under the theory, that the vocal organ — composed of the larynx, pharynx, and mouth — forms a conical tube, in which the air is set in vibration by a move- ment similar to that which prevails in organ pipes. The trachea is terminated above bv a cleft — the glottis — which is the inferior aperture of the vocal instrument. This cleft, which is capable of beino- rendered more or less narrow, plays the same part as the lumiere des tvyaux a bouche, or the narrow space in the organ pipe at the edge of the biseau or languette, along which the air passes. The air clears it, traverses the ventricles of the larynx, or 432 MUSCULAR MOTION. the cavity of the instrument, and strikes the superior ligaments. These surround the upper aperture of the instrument, and fulfil the same function as the biseau of the organ pipe. The air, con- tained in the interior of the larynx, now vibrates, and sound is produced. This sound acquires intensity, because the waves, that constitute it, are extended into the vocal tube situate above the larynx, and excite, in the column of air filling it, a movement similar to that occasioned in the tube of a flute ; except, that the tone can be much varied, because the larynx, being a short tube, can give rise to various tones by simple modification in the velocity of the air sent through it; and, moreover, the vocal tube has the same power, its parietes being membranous, of a vibratory nature, and capable of different degrees of tension. The inferior or outer part ofthe vocal tube is equally constituted of elastic parietes, sus- ceptible of varied tension; and the mouth, by modifying the di- mensions of the column of air within the vocal tube, exerts an influence on the number of vibrations, which the column is capable of experiencing; whilst the lips can convert the channel at pleasure into an open or closed conical tube. Certain sounds, Savart affirms, are produced altogether in the ventricles of the larynx — those of pain, and the falsetto voice, for example. They can be elicited, even when the vocal tube has been removed ; and there are ani- mals, in which the vocal organ is reduced to the ventricles of the larynx-—frogs for instance. Savart, consequently, considers,that the human vocal organ has, in its essential parts, CC,BB, Fig. 107, a striking analogy to the action ofthe bird-call; and, in this way, he explains the use of the superior ligaments C C, which are entirely overlooked in the different theories ofthe voice previously propounded. We have given Savart's view at some length, in consequence of its ingenuity, and of its seeming to explain as well as any other theory the varied tones of which the human voice is susceptible. It cannot, however, be esteemed established, inasmuch as it is diametrically opposed, in many of its points, to the observations .and vivisections of distinguished physiologists ; who, it has been seen, affirm, that voice is produced solely by the inferior ligaments; that all the parts above these may be destroyed, and yet voice continue ; and that a wound in the ventricles, which permits the exit of air through the parietes of the larynx, does not destroy the function. Our notions on this point must not, therefore, be considered definite. Farther experiments are necessary ; and, in all deductions from them, great importance will have to be attached to the vital action ofthe organs, especially ofthe intrinsic muscles, which are capable of modifying the situation of parts, and the character of the function in myriads of inappreciable ways." 3. Timbre or Quality of the Voice. In the preliminary essay on sound, attached to the physiology of audition, it was remarked, that the cause of the different tim- VOICE — TIMBRE. 433 bres of sound, in the various musical instruments, had hitherto re- mained unexplained. The same remark is applicable to the timbre ofthe voice. Each individual has his own, by which he is distin- guished from those around him; and it is the same with each sex and period of life. In this, the larynx is, doubtless, concerned ; but in what manner is not clear. The feminine timbre or stamp, which characterizes the voice of the child and of the eunuch, would appear to be generally connected with the cartilaginous condition of the larynx ; whilst the masculine voice, which is sometimes met with in the female, is connected with the osseous condition of these parts, and especially of the thyroid cartilage. An infinity of modi- fications may also be produced by changes in the thickness, elasti- city, and size of the lips of the glottis. The vocal tube probably exerts great influence in this respect, by its shape as well as by the nature of the material composing it. Such conditions, at least, appear to modify the timbre of our wind instruments. The timbre of a flute, made of glass or brass, is very different from that of one formed of wood, although the instruments may resemble each other in every other respect. The form of the body of the instrument has, also, considerable effect. If it be conical, and wider towards its outlet, as in the clarionet, or hautboy, the quality of the sound is shrill. If it be entirely cylindrical, as in the flute, we have the soft quality, which characterizes that instrument; and on the other hand, if the tube be expanded at its middle portion, the quality of the sound is raucous and dull. It is probable, therefore, that" we must reckon, amongst the elements ofthe varying character ofthe timbre or stamp of the voice, the different conditions of the vocal tube, as to length, width, and form ; and that we must likewise include the position and shape of the tongue, of the velum palati, and of the mouth and nose, the presence or want of teeth, &c, all of which circumstances modify the voice considerably. The first modification takes place, probably, in the ventricles of the larynx, in which the voice acquires more rotundity and expansion." It was remarked by Dr. Isaac Parrish,a that a peculiar change of voice was induced in tw'o cases by the excision of the tonsils. It was rendered shrill and whistling. By the generality of physiologists, it is conceived, that the voice enters the different nasal fossae, and, by resounding in them, a timbre or character is given to it, which it would not otherwise possess. According to this belief, when the voice is prevented from passing through the nose, from any cause, it acquires the nasal twang; or, by a singular inaccuracy of language, we are said " to talk through the nose." Magendie,b however, considers, that, whenever the sound passes through the nasal fossae, the voice becomes disagree- able and nasal. Simple experiment, by holding the nose, exhibits, that, in the enunciation of the true vocal sounds, unmodified by the action ofthe organs of articulation, the timbre or quality is ma- il Quarterly Summary ofthe Transactions ofthe College of Physicians of Philadelphia, Nov. and Dec. 1841, and Jan. 1842, b Precis Elementaire, i. 254. VOL. I. — 37 434 MUSCULAR MOTION. terially altered; and we shall see, hereafter, that there are certain letters, which do not admit of enunciation, unless the nasal fossae be pervious — the m, the n, and the ng, for example. It would seem that, under ordinary circumstances, the sound, after it is pro- duced in the larynx, flows out by both channels ; and that, if we either shut off the passage through the nose altogether, or attempt to pass the sound more than usually through the nasal fossae, the voice becomes nasal. The fine, sharp voice prior to puberty is especially owing to the narrowness of the glottis, to the shortness of the ligaments, and, according to Malgaigne,a to want of deve- lopment of the nasal cavities. At puberty, the size ofthe opening of the larynx is doubled ; the ligaments enlarge, and the passages of the nose are augmented. The timbre now becomes raucous, dull and coarse, and for a time its harmony is lost. M. Bennati,b himself an excellent theoretical and practical musician, whose voice marks three octaves, advises, that the voice should not be much exerted during this revolution. He has known perseverance in singing at this time completely destroy the voice in several in- stances. Not only does the voice, when produced in the larynx, pass out by the vocal tube, but it resounds along the tracheal and bronchial tubes, giving rise to the resonance or thrill, which is audible in certain parts of the chest, more especially, when the ear or the stethoscope is placed over them; and, when cavities exist in the lungs, in persons labouring under pulmonary consumption, if the ear be placed upon the chest, immediately over one of these cavi- ties, the voice will appear to come directly up to the ear. The same thing happens, if the stethoscope be used. In this case, the voice will appear to pass directly through the tube to the ear, when the extremity of the instrument is applied over the vomica, so as to give rise to what Laennec terms pectoriloquy. Adelon0 con- ceives, that this distribution of the sound along the trachea or porte-vent and the lungs may induce a belief, that the condition of these organs has some effect on the timbre ofthe voice. In speaking of the timbre ofthe voice in different individuals, we have had in view the natural quality, not that which is the result of imitative action, and which can be maintained for a time only. Many ofthe conditions, which have been described as regulating the timbre, are voluntary, especially that of the shape of the vocal tube. In this way we can modify the timbre and imitate voices very different from our own. The table d'hote of many of the hotels of continental Europe is enlivened by the presence of indi- viduals, capable of not only imitating various kinds of birds, but the timbres of different musical instruments; and the success which has attended the personation of the different voices of public speakers, by Matthews, Yates, and others, is sufficient evidence of a Archives Generates de M£decine, p. 201 and 214, Fevrier, 1831. b Recherches sur le M6canisme de la Voix Humaine, Paris, 1832. c Physiologie de l'Homme, edit. cit. ii. 204. VOICE—TIMBRE. 435 the fidelity of their representations. We see the difference between the natural and imitative voice strongly exemplified in one of the feathered songsters of our forests, the turdus polyglottis or mock- ing bird, which is capable of imitating, not only the voices of other birds, but sounds of other character, which cannot be regarded in the light of accomplishments. There is a singular variety of the imitative voice, now employed only for purposes of amusement — but, of old, perhaps, used in the Pagan temples, by the priests, to infuse confidence in the oracular dicta of the gods — which requires some notice ; it is engrastim- isrn or ventriloquism. Both these terms, by their derivation, indi- cate the views at one time entertained of its physiology, namely, that the voice of the ventriloquist is made to resound in the abdo- men, in some inexplicable manner, so as to give rise to the peculi- arity it exhibits. This singular view seems to have been once embraced by M. Richerand.3 " At first," says he, " I had con- jectured, that a great part of the air expelled by expiration did not pass out by the mouth and nostrils, but was swallowed and carried into the stomach : and, being reflected in some part of the diges- tive canal, gave rise to a real echo ; but, having afterwards more attentively observed this curious phenomenon on Mr. Fitzjames, who exhibits it in its greatest perfection, I was soon convinced, that the name of ventriloquism is by no means applicable." M. Riche- rand was probably the last remnant of the ancient vague hypothe- sis, and his views soon underwent a conversion. Another, equally unfounded notion, at one time entertained, was, that the ventriloquist possesses a double or triple larynx. It is now universally admitted, that the voice is produced at the ordi- nary place, and that it is modified in its intensity and quality by actions of the larynx and of the vocal tube, so as to give rise to the deceptions we experience. It is known, that our appreciation of the distance and nature of a sonorous body is formed from the intensity and quality of the sound proceeding from it. We instinc- tively believe, that a loud sound proceeds from a near object, and a feeble sound from one more remote ; accordingly, if the intensity and quality of the sound, from a known body, be such as to im- press us with the idea, that it is more remote than it really is, we incur an acoustic illusion. The ventriloquist takes advantage of this source of illusion; and, by skilfully regulating the force and timbre of his voice, irresistibly leads us into error. Mr. Dugald Ste wartb gives some striking examples of this kind of illusion. He mentions having seen a person, who, by counterfeiting the actions of a performer on the violin, whilst he imitated the music by his voice, riveted the eyes of the audience on the instrument, although every sound they heard proceeded from his own mouth. Mr. Savile Carey, who imitated the whistling of the wind through a » Elemens de Physiologie, edit. 13eme, par M. Berard aine, edit. Beige, cxciv. p. 300, Bruxelles, 1837. b Elements of the Physiology of the Human Mind, 3d edit., Lond. 1808 ; Amer. Edit. Brattleborough (Vermont), 1813. 436 MUSCULAR MOTION. narrow chink, told Mr. Stewart, that he had frequently practised the deception in the corner of a coffee-house, and that he seldom failed to see some of the company rise to examine the tightness of the windows, whilst others, more intent on the newspapers, con- tented themselves with putting on their hats, and buttoning their coats.a It is to account for the mode in which this is effected, that different hypotheses have been, from time to time, entertained. Haller, Nollet, Mayer,b and others, believed, that the voice is formed during inspiration ; but this does not seem to be the case. Voice can certainly be effected during inspiration ; but it is raucous, unequal, and of trifling extent only. Dumas and Lauth0 consider ventriloquism to be a kind of rumination of sounds ; the voice, formed in the larynx, being sent into the interior of the chest, at- taining there a peculiar timbre, and issuing of a dull character. Richerand is of opinion, that the whole mechanism consists in a slow, gradual expiration, which is always preceded by a deep in- spiration. By means of this, the ventriloquist introduces into his lungs a considerable quantity of air, the exit of which he carefully regulates. Mr. Goughd attempts to explain the phenomenon upon the principle of echoes: —the ventriloquist, he conceives, selects a room, well disposed for echoes in various parts of it, and produces false voices, by directing his natural voice in a straight line to- wards such echoing parts, instead of in a straight line towards the audience, who are supposed, by Mr. Gough, to be placed designedly by the ventriloquist on one or both sides of him. A sufficient answer to this is, that the practised ventriloquist is careless about the room chosen for his exhibitions; and that he habitually performs in rooms, where this system of echoes would be totally impracticable. But it is well to inquire what the ventriloquists themselves have said of the mechanism of their art. We pass over the explanation of Baron von Mengen, an Austrian'colonel, who forms a kind of vocal organ between his tongue and his left cheek, if we under- stand his description correctly, and keeps a reservoir of air in his throat to throw the organ into vibration. His object must evi- dently have been to mislead. In 1811,M. L'Espagnol, a young physician, maintained a thesis on this subject before the Faculle de Midecine of Paris, which may be regarded as, at least, an honest exposition of his belief, regarding the mode in which the phenomenon was effected in his own person. According to him, the whole is dependent upon the action of the velum pendulum palati. In the ordinary voice, he remarks, a part of the sound passes directly through the mouth whilst another resounds in the nasal fossae. If we are near the person who is speaking, these two sounds strike equally and » Brewster, Natural Magic, Amer. Edit., p. 158, New York, 1832. >> Haller, Element. Physiol., torn. ix.; and Lepelletier, Physiologie Medicate, &c, c Memoir, de la Societe des Sciences Agricol. de Strasbourg, i. 427. •i Manchester Memoirs, 2d edit. v. 622, Lond. 1789. VOICE — VENTRILOQUISM. 437 almost synchronously upon the ear; but if we are at a distance, we hear only the first ofthe two sounds, when the voice appears more feeble, and, especially, has another timbre, which experience makes us judge to be thatof the voice at a distance. The differ- ence, says M. L'Espagnol, between the voice that proceeds from a near, and that from a more distant object is, that in the former we hear the mixture of the two sounds ; whilst in the latter we hear that sound only, which issues directly from the mouth. Now, the secret of the ventriloquist is, to permit this direct sound only to pass to the ear, and to prevent the nasal sound from being pro- duced, or at least from being heard; and this is done by the elevation of the velum pendulum palati; the vocal sound does not then re- sound in the nasal fossae; the direct sound is alone produced; the voice has the feebleness and timbre that belong to the distant voice, and is judged to proceed from a distance ; and if, during the performance, the voice seem to come from any determinate place, it is owing to the ventriloquist attracting attention to it ; the voice itself need only appear to proceed from a distance ; and this it does more or less, according as the pendulous veil has more or less completely prevented the vocal sound from issuing by the nasal fossae. The ventriloquist, thus, according to M. L'Espagnol, makes the voice nearer or more remote at pleasure, by raising or depressing the velum palati. He denies, that he speaks with his mouth closed ; and affirms, that he articulates, but to a trifling extent only. M. Comte, another ventriloquist, and of some celebrity, who has endeavoured to explain the physiology of his art, affirms, that the voice takes place as usual in the larynx ; but that it is modified by the action of other parts of the apparatus ; that inspiration directs it into the thorax, where it resounds; and that both strength and flexibility are required in the organ to produce this effect. This, however, is no explanation. It is now universally admitted, that the voice of the ventriloquist is produced in the larynx ; and that its character and intensity are modified by the action of other parts ofthe apparatus, but the particular action that produces it is not elucidated by any of these attempted explanations ofthe ventrilo- quist. About twenty-five years ago, Dr. John Mason Good,3 in some lectures delivered before the Surrey Institution of London, sug- gested that the larynx alone, by long and dexterous practice, and, perhaps, by a peculiar modification in some of its muscles or car- tilages, may be capable of answering the purpose, and of supply- ing the place, of the associate organs of the mouth. In confirma- tion of this view, he remarks, that, in singing, the glottis is the only organ made use of, except where the notes are articulated ; and it is apparently the sole organ employed in the mock articu- lations of the parrot and other imitative birds; some of which a Book of Nature, ii. p. 264, Lond. 1826 ; and Study of Medicine, Physiological Proem to Class ii. 37* 438 MUSCULAR MOTION. have exhibited unusual powers. A parrot belonging to a Colonel O'Kelly, could repeat twenty of the most popular English songs, and sing them to their proper tunes.3 The larynx, too, is the sole organ of all the natural cries; and hence, it has been imagined, by Lord Monboddo,b to have been the chief organ of articulate language, in its rudest and most barbarous state. " As all natural cries," he observes, "even though modulated by music, are from the throat and larynx, or knot of the throat, with little or no ope- ration of the organs of the mouth, it is natural to suppose, that the first languages were, for the greater part, spoken from the throat; and that what consonants are used to vary the cries, were mostly gutterals ; and that the organs of the mouth would at first be but very little employed." Certain it is, that privation of the tongue does not necessarily induce incapacity of articulation ; whether the defect be congenital, or caused after speech has been acquired. Professor John Thomson found the speech but little impaired after bullets had carried away more or less of the tongue.0 Under the Sense of Taste, several authentic cases were stated of individuals, who were deprived of this organ, who yet possessed the faculty of speech, To these we may add one other, which excited unusual interest at the time, and was examined under circumstances that could admit of no deception. The case forms the subject of various papers, by Dr. Parsons.*1 A young woman, of the name of Margaret Cutting, of Wickham market, near Ipswich, in Suffolk, when only four years old, lost the whole of her tongue, together with the uvula, from a cancerous affec- tion ; but still retained the powers of speech, taste, and deglutition without any imperfection ; articulating as fluently and correctly as other persons; and even those syllables that commonly require the aid of the tip of the tongue for accurate enunciation. She also sang admirably ; articulating her words whilst singing; and could form no conception of the use of a tongue in other people. Her teeth were few, and rose scarcely higher than the surface of the gums, owing to the injury to the sockets from the disease that had destroyed the tongue. The case, when first laid before the Royal Society, was attested by the minister of the parish ; by a medical practitioner of repute, and by another respectable individual. The society, however, were not satisfied, and they appointed commis- sioners to inquire into the case, whose report coincided minutely with the first; and, to set the matter completely at rest, the young woman was shortly afterwards conveyed to London, and examined, in person, before the Royal Society.e These cases are not so extraordinary as they appear to be at first sight; when we consider, that the tongue is not the sole organ • Good's Book of Nature, ii. 248. b Origin and Progress of Language, Lond. 1774— 1792. c Report of Observations made in the British Hospital, in Belgium, after the Battle of Waterloo, Edinb., 1816. ' Philosoph. Transact, for 1742 and 1747. e Elliotson, Human Physiology, p. 507, Lond. 1840. VOICE — VENTRILOQUISM. 439 of articulation, but that it shares the function with the various parts that compose the vocal tube. In reality, of the twenty-four articu- late sounds, which our common alphabet comprises, there are but few in which the tongue takes a distinct lead, as the /, d, t,r, &c, • though it is auxiliary to several others ; but the guttural or pala- tine, g, h, k,q; the nasal, as m, and n; the labial, as b,p,f, v; and most of the dental, together will all the vowels, are but little indebted to its assistance. From these, and other concurrent facts, Dr. Gooda concludes, that ventriloquism appears to be an imitative art, founded on a close attention to the almost infinite variety of tones, articulations, and inflexions, which the glottis is capable of producing in its own region alone, when long and dexterously practised upon ; and in a skilful modification of these vocal sounds, thus limited to the glottis, into mimic speech, passed for the most part, and whenever necessary, through the cavity of the nostrils, instead of through the mouth. It is possible, he adds, though no opportunity has hither- to occurred of proving the fact by dissection, that those who learn this art with facility, and carry it to perfection, possess some pecu- liarity in the structure of the glottis, and particularly in respect to its muscles or cartilages. Magendie,b and Rullier,0 however, affirm, that the quiescence of the lips, observed in the practised ventriloquist when enunciating, is more apparent than real; and that if he be capable of pronouncing without moving his lips, it is because he is careful to make use of words in which there are no labial consonants, or which do not absolutely require the movement of the lips in their formation. Rullier, indeed, denies positively, that the ventriloquist can speak without opening his mouth and moving his lips; but he affirms, that he uses his jaws, mouth and lips, as little as possible in articulation ; and he ascribes the common belief in their perfect quiescence to the habit, acquired by the ven- triloquist, of restraining their movements, united to the care he takes in concealing them; and of giving to his face an impassive expression, or one very foreign to the verbal expression to which he is giving utterance. On the whole, the explanation of Dr. Good appears most satis- factory :— the larynx or glottis affording to some individuals a facility in acquiring the art, which others do not possess, in the same manner as it makes some capable of singing, whilst others are ever incapacitated. It is probable, however, that there may be a greater degree of obscure action about the parts composing the vocal tube, than Dr. Good is disposed to admit; and that this may be materially concerned in giving the voice its peculiar quality and intensity ; and eliciting some of the sounds which might not be so easily produced by the action of the glottis alone. Sir David Brewster*1 observes, that when the ventriloquist utters sounds from * Op. citat. ii. 259. b Precis, &c. i. 265. c Art. Engastrimysme, in Diet, de Medecine, torn. viii. Paris, 1823. <> Letters on Natural Magic, p. 169, Amer. Edit., New York, 1832. 440 MUSCULAR MOTION. the larynx without moving the muscles of his face, he gives them strength by a powerful action of the abdominal muscles : and Bennati affirms, that the ventriloquist uses chiefly the pharyngeal voice, of which mention will be made under the head of Singing. Such is the history ofthe simple voice, as effected in the larynx. Articulate sounds may, however, be produced in the vocal tube alone. Whistling, for example, is caused by the expired air being broken or divided by the lips, which act the part of the lips of the larynx in the production of voice. Whispering, consists in the articulation ofthe air of expiration. It is wholly accomplished in the vocal tube ; and, hence, the im- practicability of singing in a whisper ; singing being produced in the glottis. The sound of sighing is produced by the rushing of the air along the air passages, and especially along the vocal tube. In laughing, crying, and yawning, the voice is likewise concerned ; but the phy- siology of these functions of expression will fall more appropriately under the head of respiration. Having described the different views, that have been entertained, with regard to the production of voice, we shall now inquire into the function in connexion with expression. In this respect, it admits of division into the natural or inarticulate voice, and into the artificial or articulate. 4. OF NATURAL OR INARTICULATE LANGUAGE. This, which is sometimes termed the cry or native voice, is an inappreciable sound, entirely produced in the larynx, requiring few or none of the organs of articulation to aid in its formation. As, however, it is caused by different degrees of contraction of the intrinsic muscles of the larynx, it is susceptible of a thousand dif- ferent tones. It is elicited independently of all experience or education ; seems to be inseparably allied to organization; and, con- sequently, occurs in the new-born infant, in the idiot, in the deaf from birth, and in the wild man, if any such there be, as well as in the civilized individual. The natural voice differs as much as the sentiments it is employed to express. Each moral affection has its appropriate cry; — the cry of joy is very distinct from that of grief; — of surprise from that of fear, &c.; and the pathologist finds, in the diseases of children more especially, that he can occa- sionally judge of the seat of a disease by the character of the cry, to which the little sufferer gives utterance; in other words, that there is, in the language of Broussais, a cry peculiar to the suffer- ing organ. By the cry, our vivid sensations are expressed, whether they be of the external or internal kind; agreeable or painful; and by it we exhibit all our natural passions, and most simple instinctive de- sires. Generally, the most intense sounds, to which the organ of voice can give utterance, are embraced in the natural cry ; and, in VOICE — ARTICULATE LANGUAGE. 441 its character, there is frequently something, which annoys the ear and produces more or less effect on those within its sphere. It is, indeed, by its agency, that sympathetic relations are established between man and his fellows; and between animals of the same kind. The language, possessed by the greater part of animals, is, as already remarked, this natural voice, differing according to vary- ing organization, and, therefore, instinctive ; hence the various notes of birds ; and the different ranges, which we find the voice to possess in the different species. Yet each species has one, by which it is distinguished, and which it possesses, even when brought up in the same cage with one of another species ; or hatched, and attended to, by a foster mother, endowed with very different vocal powers. In the case of a goldfinch and chaffinch, this has been put directly to the proof; and it is well known, that the cuckoo, which is never hatched or nurtured by its own parent, still retains the note, which has acquired it its name in almost every language of the globe. It is, probably, by this natural cry, and not from any signs addressed to the eye, that the process of pairing is effected and that the female is induced to select her mate. The vocabulary of the common cock and hen is quoted as perhaps the most exten- sive of that of any tribe of birds with which we are acquainted; or rather, as Dr. Good remarks,3 we are better acquainted with the extent of its range than with that of any other. The cock has his watch-word for announcing the morning; his love-speech and his terms of defiance. The voice of the hen, when leaving her nest, after laying, is far different from that which she assumes, when the brood is hatched, and both are very different from her cries, when her young are placed in jeopardy. Even the chick exhibits a variety in its voice, according to the precise emotion it expe- riences. All these sounds are such as the larynx of the animal permits alone to be produced ; and hence we can understand why, so far, they should be mere modifications of the natural voice; but it is more than probable, that the chick learns the adoption of a particular sound by the parent, to express a particular emotion, as an affair of education. It can scarcely indeed, be conceived, that the clucking of the hen, when she meets with food proper for her offspring, can be understood at first by the chick. But as soon as it traces the connexion between the sound produced and the object of such sound, it comprehends the signification ever afterwards. There are sounds, which, from their discordant and harsh cha- racter, affect most animals perhaps, independently of all expe- rience. The cry of terror or of pain, appears to occasion, sympa- thetically, disagreeable effects on all that are within its sphere. 5. ARTIFICIAL OR ARTICULATE LANGUAGE. Speech is, likewise, a vocal sound ; but it is articulated, in its passage through the vocal tube ; and is always employed to con- vey ideas, which have been attached to it by the mind. It is a » Book of Nature, ii. 277, Lond. 1826. 442 MUSCULAR MOTION. succession of articulate sounds, duly regulated by volition, and having determinate significations attached to them. The faculty of speech has been assigned, by some philosophers, chiefly to the organ of hearing. It is manifest, however, that this, like the musical ear, is referable to a higher organ. The brain must attach an idea to the impression made upon it by the sound that impinges upon the organ of hearing; the sound thus becomes the sign of such idea, and is reproduced in the larynx, at the will of the individual. Of the intellectual character of the process, we have the most decisive evidence. The infant, of tender age, has the ear and the voice well developed, yet it is long before he is capable of speech ; this does not happen, indeed, until he dis- covers the meaning of the sounds addressed to him, and finds his own larynx capable of producing similar sounds, which can be made subservient to his wishes. It is thus, by imitation, that he acquires the faculty of speech. Again, the idiot, notwithstanding his hearing may be acute, and his voice strong, is incapable of speech; and, in the maniacal and delirious, the language parti- cipates in the derangement and irregularity ofthe ideas. The brain must, therefore, be regarded as the organ ofthe faculty of language, and the ear, larynx, and vocal tube as its instruments. Man, who is endowed with the most commanding intellect, has the vocal ap- paratus most happily organised for expressing its various combi- nations ; and, according to Gall, if the ourang-outang and other animals are incapable of speech, it is because they have not the intellectual faculty of language. In proof, that it is not to the vocal organ that this deficiency must be ascribed, he remarks, that animals may be made to enunciate several of the words of human speech, and to repeat them to music. The case of the far-famed parrot of Colonel O'Kelly has already been referred to. Mr. Her- bert saw this parrot, about the year 1799: it then sang perfectly about fifty different tunes, solemn psalms, and humorous or low bal- lads, articulating every word as distinctly as a man, without a single mistake, beating time with its foot, turning round upon its perch, and marking the time as it turned. If a person sang part of a song it would take it up where he left off; and when moulting and un- willing to sing, turned its back and said, "Poll's sick." Gall, amongst other cases, cites that of a dog mentioned by Leibnitz, which could articulate some German and French words. This dog, of which Leibnitz was an " eye-witness," was at Zeitz, in Misnia. A young child had heard it utter some sounds, which he thought resembled German, and this led him to teach it to speak. At the end of about eight years, it had learned thirty words, some of which were, tea, coffee, chocolate, assembly. It spoke only after its master had pronounced the word, and appeared to do so only on compulsion, although it was not ill used.b In the " Dum- fries Journal," Scotland, for January, 1829, mention is made of a a In a note to the Rev. Gilbert White's Natural History of Selborne, p. 227. b Letter to the Abbe Saint Pierre, Oper. ii. 180. VOICE — ARTICULATE LAN G UAGE. 443 dog, then living in that city, which could utter distinctly the word " William," the name of the young man to whom it was much attached.8 There is no doubt, however, that in numerous animals, speech would be impracticable, owing to defective organization, even were they gifted with adequate intellect. It is difficult — perhaps impossible — to say, how man came to select certain sounds as the types of certain intellectual acts ; nor is it a matter which strictly concerns the physiologist. We may remark, however, that whilst some contend, that speech is a science which was determined upon, and inculcated, at an early period of the world, by one or more superior persons, acting in concert, and inducing those around them to adopt their articulate and arbitrary sounds; others affirm, that it has grown progressively out of the natural language, as the increasing knowledge and in- creasing wSnts of mankind have demanded a more extensive voca- bulary.1* The first view is that of Pythagoras and Plato; but it was opposed by Lucretius and the Epicureans, on the ground, that it must have been impossible for any one person or synod of per- sons to invent the most difficult and abstruse of all human sciences, with the paucity of ideas, and of the means of communicating them which they must have possessed; and that even allowing they could have invented such a science, it must still have been utterly impossible for them to teach it to the barbarians around them. The opinions of those philosophers, who confine themselves to the phenomena of nature,and hold themselves uncontrolled by other authority, accord with those ofthe Epicureans. In the origin of language, it is probable, that words were suggested to mankind by the sounds, which were heard around them : — by the cries of quadrupeds ; — the notes of the birds of the forest; —the noises emitted by the insect tribe; —the audible indications from the elements, &c. These, being various, probably first of all suggested discriminative names,deduced from the sounds heard. It is this imitation of the noise, made by objects, that con- stitutes the figure of speech, called onomatopoeia, — the " vox repercussa naturx," or " echo of nature," as Wachter0 has defined it. Daily experience shows us, that this source of words is strictly phy- siological. Children always designate a sonorous object by an imitation of the sounds given off by it; and the greater number of sonorous bodies have had names, radically similar, given to them in languages differing most from each other. We say the serpents "hiss," the bees "hum," the storm "blusters," thewind ''whistles," the hogs " grunt," the hen " cackles," the man " snores," &c, words used, originally, not perhaps in these very shapes, but varying ac- cording to the varying idiom of the language, to imitate the sounds » Sharon Turner's Sacred History of the World, p. 280, Amer. Edit. New York, 1832. b Harris's Hermes, Book iii. p. 314 ; Beattie's Theory of Language, p. 246, Lond. 1803 ; Good's Book of Nature, ii. 283, Lond. 1826. c GJossarium Germanicum, Lips. 1737. 444 MUSCULAR MOTION. elicited from these objects. Such words are numerous in all lan- guages, and have been adopted to depict both the sound emitted, and the sonorous body itself; but, in some cases, the word, imita- ting the sound, has survived its transmission from language to lan- guage to the most modem times, whilst the name of the object, whence it proceeded, has experienced considerable mutation. The Sanskrit, the antiquity of which will not be contested, has a num- ber of such words —as wilala, the cat — kukada, the hen — and waihu, the wind; in the last of which the sound of the w, (oo,) imitates that of the passage of the air, and is found in the word corresponding to wind, (ooind,) in many languages. The Hebrew and the Greek have numerous phonetic words, but no language is richer, in this respect, than the Teutonic, in all its ramifications, including the English. The animal kingdom affords us many examples, of which the following is one. Cuckoo. — This word is nearly the same in almost all languages. Greek, kokku^ ; Latin, cucullus ; Irish, cuach; Bask, cucua ; Sclavonic, kukulka, kukuscka, &c.; Hungarian, kukuk; Hebrew, cacatha; Syriac, coco ; Arabic, cuchem; Persian, kuku; Koriak, kaikuk; Kamtschadale, koakutschith ; Kurile, kakkok; Tartar, kauk ;; German, kuckucks or guckguck ; Dutch, koekoek ; whence our words cuckoo and cuckold, and the Scottish, gouckoo, go-wk, or golk ,• French, cocu ; &c. In the greater part of languages, words, expressive of the cries of animals, are accurate imitations. Of this, the following are a few examples. Bleating of sheep---Greek, 0\>,^j.ojuan; Latin, balare } Italian, belare ; Spanish, belar; French, btler ; German, bib ken ; Dutch, bleeten ; Saxon, blxtan, &c. Howling of wolves. — Greek, oKokv£a>; Latin, ululare; German, heulen ; Dutch, huilen; Spanish, aullar; French, hurler, &c. Hence the word oivl. Neighing of the horse. — Latin, hinnire; French, hennir ; German, -wiehem ; Saxon, hnxgan, <&c. Clocking, ox clucking of hens. — Latin, glocire; French, glousser ; Greek, KMiiizgiiv ; German,glucken; Dutch, klokken ; Saxon, cloccan, &c. To croiv, like a cock. — Greek, */>*(*&>; German, krcihen ; Dutch, kraayen; Saxon, craiv, &c, whence the word croto, the bird. The Latin words tinnimentum, tinnitus, tintinnabulum, &c, from tinnio, " I ring," are all from the radical tin ; imitating the sound rendered on striking a metallic vessel. The gurgling of water, the clanging of arms, the crash of falling ruins, are of the same character; and the game trictrac, formerly tictac, seems to have been so called, from the noise made in putting down the men or dice. In whatever manner language was first formed, it is manifest, that the different sounds could make but a transient impression, until they were reduced to legible characters, which could bring them back to the mind. On our continent, the fact has often been noticed of a tribe of Indians separating themselves into two parties, and re- maining distinct for years. In such case, the language has become so much modified, that after the lapse of a considerable period they have scarcely been able to comprehend each other. Hence, the importance of the art of writing, —certainly the most valuable of human inventions. Of this, there have been two kinds,—the imita- VOICE — ARTICULATE LANGUAGE. 445 live or alphabetical, — and the symbolical, allegorical or emblema- tical, which latter consists of hieroglyphics, or designs representing external objects, or of symbolical allegories. The former or the written representation of spoken sounds alone concerns us. To attain this, every compound sound has been reduced to certain ele- mentary sounds, which are represented by signs, called letters. These elementary sounds, by combination, form syllables ; and the syllables, by combination, words. The number of elementary sounds, admitted in each language, constitutes its alphabet, which differs more or less in certain languages; but as it is entirely a matter of human invention, and as the elementary sounds, of which the human voice is capable, are alike in the different races of mankind, we see readily, that the alphabets of the different languages must strikingly correspond, although the combinations of the letters con- stituting syllables and words may vary essentially. Into the origin of the written legible language, it is not necessary for us to inquire. We may remark, however, that the invention has been considered so signally wonderful as to transcend the human powers; and hence St. Cyril, Clement of Alexandria, Eusebius, Isidore, and in more modern times, Messrs. Bryant, Costard, &c, have been of opinion, that the knowledge of letters was first com- municated to Moses by the Almighty himself, and that the decalogue was the earliest specimen of alphabetic writing. Many passages, however, in the writings of Moses, show unequivocally, that written records must have existed prior to his time. In the passage in which writing is first mentioned in the sacred volume, the art is alluded to as one of standing: — " And the Lord said unto Moses, ' Write this for a memorial in a book or table;' " and in a subsequent chapter — " And thou shalt make a plate of pure gold; and grave upon, like the engravings of a signet, Holiness to the Lord."a The English alphabet is considered to consist of twenty-six let- ters. It may, however, by ultimate analysis, be reduced to twenty- five simple sounds — A, B, D, E, F, G, H, I, J, K, L, M, N, 0, P, R, S, T, U, V, Z, Ch, Sh, Th, and Ng. To these letters arbitrary names have been assigned, as Bee (B,) See (C,) Dee (D,) &c, which ex- press very different sounds from those that belong to the letter when it forms part of a word or syllable. The word bad is not pronounced bee-a-dee ; as the child, just escaped from learning his alphabet, must imagine ; hence, he has to unlearn all that he has acquired, or to imagine, that the different letters have very different sounds, according to the situation in which they may be placed. To obviate this inconvenience, many individuals are in the habit of teaching their children syllabically from the very first, by which they acquire the true sound, attached to each letter of the alphabet. In the preceding enumeration of the simple sounds, which consti- tute the alphabet, C, Q, W, X, and Y, have been excluded, for the following reasons. C has always the sound of either S or K, as in » Good, op. citat. ii. 304. VOL. I. — 38 446 MUSCULAR MOTION. cistern ox consonant. Q has the sound of koo, as in quart, (kooart;) W of oo, as in word, (oourd;) X of ks, or Z, as in vex, (vecks,) or Xerxes, (zerkses;) whilst Y has the sound of I or E, as in wry or yard, (wri or eeard.) Ch, Sh, and Th, have been added, as being true alphabetic or simple sounds. Letters have been usually divided into two classes, — vowels and consonants. The vowels or vocal sounds axe so called, because they appear to be simple modifications of the voice, formed in the larynx, uninterrupted by the tongue and lips, and passing entirely through the mouth. Such at least is the case with those that are reckoned pure vowels. These, in the English alphabet, are five in number,— A, E, I, 0, and U. W and Y are, likewise, vowel sounds in all situations. In enunciating A, as in fate, the tongue is drawn backwards and slightly upwards, so as to contract the passage immediately above the larynx. In sounding E, the tongue and lips are in their most natural position, without exertion. I is formed by bringing the tongue nearly into contact with the bony palate, 0, by the contraction of the mouth being greatest immedi- ately under the uvula, the lips being also somewhat contracted. In the production of U, the contraction is prolonged beneath the whole of the soft palate. From these principal vowels, all the other vowel sounds of the language may be formed, by considering them as partaking more or less of the nature of each. These are, in our language, fourteen in number; besides compound sounds, as in oil and pound. Of these fourteen, four belong to A; two to E; two to I; three to 0 ; and three to U. Fate. Far. O, as in - \ A, as in 1 Fast. C Fall. E, as in - - S ^e- U. as in " " £Met. I. Mi. - . l$£ The vowels are more easy of pronunciation than the consonants. They merely require the mouth to be opened; and howsoever it may be arranged in the enunciation of the different vowels, the vocal tube is simply modified, to vary the impression, which has to be made on the organ of hearing. The shape of the cavity is altered, but the passage of the air continues free, and the vo'ice, consequently, issues in an unrestrained manner. Hence, perhaps, the physiological origin of the Danish word Aa, " a river" — a generic term, which became afterwards applied to three rivers in the Low Countries, three in Switzerland, and five in Westphalia — the sound of the two broad A's flowing without obstacle, like a river. Time passes away in a similar manner; hence, for a like reason, the Greek «« which signifies " always, perpetually ;" and the German je, which has the same signification. The consonants are more difficult of enunciation than the vowels; as they require different, and sometimes complex,and delicate move- VOICE — ARTICULATE LANGUAGE. 447 ments ofthe vocal tube ; and, on this account, are not acquired so early by children. The term consonant is derived from one of its uses, — that of binding together the vowels, and being sounded with them. By most, and according to Mr. Walker,a by the best grammarians, w and y are consonants when they begin a word; and vowels when they end one. Dr. Lowth,b however, a man of learning and judgment, who certainly would not suffer in a comparison with any of his opponents, regards them, as we do, to be always vowels. Physiologically it is not easy to look upon them in any other light. Yet Mr. Walker exclaims,— " how so accurate a grammarian as Dr. Lowth could pronounce so definitely on the nature of y, and insist on its being always a vowel, can only be accounted for by considering the small attention which is generally paid to this part of grammar." No stronger argument, however, could be used against the useless expenditure of time on this subject, than the conclusion to which Mr. Walker himself has arrived; and for which he can find no stronger reasons, than that " if w and y have every property of a vowel, and not one of a consonant; why, when they begin a word, do they not admit of the euphonic article an before them ?" The consonants are usually divided into mutes, semi-vowels, and liquids. Mutes are such as emit no sound without a vowel; b,p, t, d, k, and c and g hard. Semi-vowels are such as emit a sound, without the concurrence of a vowel, as f v, s, z, x, g soft or j. Liquids axe such as flow into, or unite easily with, the mutes, as I, m, n, r. These letters issue without much obstacle ; and hence perhaps their name. In tracing the mode in which the different consonants are arti- culated, we find, that certain of them are produced by an analo- gous action of the vocal tube ; so that the physiology of one will suffice for the other also. For instance, the following nearly cor- respond : — p f t s k ch &&&&&& b v d z g j. B and P are produced when the lips, previously closed, are sud- denly opened. B differs from P in the absence, in the latter, of an accompanying vocal sound. F and V are formed by pressing the upper incisor teeth upon the lower lip. They are, consequently, not well enunciated by the aged, who have lost their teeth. F differs from V only in the absence of an accompanying vocal sound. T and D are formed by pressing the tip of the tongue against the gums behind the upper incisor teeth: D is accompanied by a vocal sound ; T not. S and Z are produced by bringing the point of the tongue nearly in contact with the upper teeth, and forcing the air against the edges of the teeth with violence. S differs from Z in the absence of the vocal sound. K and G are formed by pressing the middle of the tongue against the roof of the mouth* near the * Preface to his Dictionary. b Introduction to English Grammar, p. 3. 448 MUSCULAR MOTION. throat; and separating the parts a little more rapidly to form the first, and more gently to form the last of those letters. In K, the accompanying vocal sound is absent. Ch and J are formed by pressing t to sh; and d to zh. In Ch, there is no accompanying vocal sound. SH and ZH are formed in the same part of the tube as s and z. TH is formed by protruding the tongue between the incisor teeth, and pressing it against the upper incisors to produce its sound in think. Its sound in that, is effected by pressing the tongue behind the upper incisor teeth. In the former case, it is unaccompanied by a vocal sound. In M, the lips are closed, as in B and P, and the voice issues by the nose. N is formed by resting the tongue against the gums, as in the enunciation of / and d; and breathing through the nose with the mouth open. In L, the tip of the tongue is pressed against the palate, the sound escaping laterally. In forming the letter K, the middle and point of the tongue strike the palate with a vibratory motion ; the tip being drawn back. Lastly, in the formation of H, the breath is forced through the mouth, which is every where a little contracted. It need hardly be said, that the enunciation of these letters requires, that the vocal tube, or the parts concerned in the function, shall be in a sound condition.3 Wolfgang von Kempelen,b in a work on the mechanism of hu- man speech, &c, which is considered classical in Germany, divides the consonants into four classes. 1. Mules, (g an z stumme,) as K, P, T. 2. Explosives, (windmitlauter,) as F, H, Ch, S, and Sh. 3. Vocal consonants, (stimmitlauter,) as B, D, G, L, M, and N ; and 4. Vocal Explosives, (wind und stimra- lauter,) as R, I, W, V, Z. Dr. Thomas Young has, likewise, divided the English consonants into classes; of which he enume- rates five. 1. Pure semi-vowels, as L, R, V, Z, and J. 2. Nasal semi-vowels, as M and N. 3. Explosive letters, as B, D, and G. 4. Susurrant letters, as H, F, X, and S: and, 5. Mutes, as P, T, K; but the most satisfactory classification, in a physiological, as well as philological point of view, is according to the parts of the vocal tube, more immediately concerned in their articulation. Labial. Dento-labial. Lingua-dental. Linguo-palatal. Guttural. B M P F V Th D JLN RSTZ Ch Sh Ng G K That this physiological arrangement has had much to do with the formation of congenerous tongues more especially is exhibited by the facts, connected with the permutation or change of letters ; when a word passes, for example, from one of the Teutonic or Romanic languages to another. •' The changes of vowels," says a See Mayo, Outlines of Human Physiology, 3d edit. p. 357, Lond. 1833; also, Haller, Element. Physiol, ix. 4. b Ueber der Mechanismus der Menschlichen Sprache, Wien. 1791; and Rudolphi, Grundriss der Physiologie, Berlin, 1821, u. s. w. VOICE — ARTICULATE LANGUAGE. 449 Mr. Lhuyd,a " whether by chance or affectation, are so very easy and so common in all languages, that in etymological observations, they need not, indeed, be much regarded; the consonants being the sinews of words, and their alterations therefore the most per- ceptible. The changes of consonants also into others of the same class, (especially labials, palatals, and Unguals,) are such obvious mistakes, that there is no nation where the common people in one part or other of their country, do not fall into some of them." A few examples will show to what extent this permutation occurs between letters of the same class in different languages. In this view, we may regard the labials and dento-labials as belonging to the same class. P into B. — Greek, fcxe^ ; Latin, phlebs. Latin, (and Greek,) episcopus ; English, bishop ; Anglo-Saxon, biscop ; German, b i s c h o f. P into F and V. — Latin, pater; German, vater; Dutch, vader ; English, father. T. into S. — German, be sser; English, better. German, wasser; English, ■water. D into Th. — German, das; Dutch, dat; English, that. T into Z. — German, z u n g; Dutch, tong ; English, tongue. German, z w e i g; English, twig. L into R. — Spanish, Gil Bias ; Portuguese, Gil Bras. Latin, arbor ; Spanish, albero. C or K into G. — Latin, hemicraninm; French, migraine. Latin, cibarium ; French, gibier. Latin, acer ; Italian, agro. Latin, alacer ; Italian, allegro. Greek, kvx.voc ; Latin, cygnus. The most harmonious languages are such as have but few con- sonants in their words, compared with the vowels; hence the mu- sical superiority ofthe Greekand Italian, over the English, German, &c. " Among certain northern nations," says M. Richerand,b " all articulated sounds appear to issue from the nose or the throat, and make a disagreeable pronunciation, doubtless because it requires greater effort; and he who listens, sympathizes,in the difficulty, which seems to be felt by him that speaks ;"—and he adds,— " would it not seem that the inhabitants of cold countries have been led to use consonants rather than vowels, because as the pro- nunciation does not require the same opening of the mouth, it does not afford the same space for the continual admission of cold air into the lungs ?" The whole of Richerand's remarks on this topic are singularly fantastic and feeble, and unworthy of serious dis- cussion. In regard to the consonants, it has been presumed, that some common imitative principle must have existed with all nations, so as to cause them to conform in adopting such as produce a certain sound to convey the same effect to the ear. Dr. John Wallis,0 turned his attention to this matter, chiefly as regards the English language, and he has collected a multitude of examples to show, that a certain collocation of consonants, at the commencement of a word, generally designates the class of ideas, intended to be con- veyed by it. For instance, he remarks that: — a Archseologia Britannica, Oxford, 1707. b Elemens de Physiologie, edit. cit. p. 298. c Grammatica Linguae Anglicanae, &c, edit. 6, Lond. 1765- 38* 450 MUSCULAR MOTION. Str, always carries with it the idea of great force and effort: — as strong, strike, stripe, strife, struggle, stretch, strain, &c. St, the idea of strength, but in less degree — the vis inertix, as it were: — as stand, stay, stop, stick, stutter, stammer, stumble, stalk, steady, still, stone, &c. Thr, the idea of violent motion : — as throw, thrust, throb, threat, throng, &c. Wr, the idea of obliquity or distortion : — as wry, wreathe, -wrest, wring, wrestle, wrench, wriggle, wrangle, &c. Br, the idea of violent — chiefly sonorous —fracture or rupture: — as break, brittle, brust, or burst, brunt, bruise, broil, &c. Cr, the idea of straining or dislocation, chiefly sonorous: — as crack, creak, crackle, cry, crow, crisp, crash. Other words, beginning with those consonants, communicate the idea of curvature, as if from curvus ; — as crook, cringe, crouch, creep, crawl, cripple, crumple, crotchet, &c. Others, again, denote decussation, as if from crux : <— as cross, cruise, crutch, crosier. Shr the idea of forcible contraction : — as shrink, shrivel, shrug, shrill, &c. Gr, the idea of the rough, hard, onerous and disagreeable, (either owing to the letter of roughness r, or from gravis,) — as grate, grind, gripe, grapple, grieve, grunt, grave, &c. Sw, the idea of silent agitation or of gentle lateral motion: — as sway, stvag, swerve, sweat, swim, swing, swift, &c. Sm, a very similar idea to the last: — as smooth, small, smile, smirk, &c. CI, the idea of some adhesion or tenacity: — as cleave, clay, cling, climb, cloy, cluster, close, &c. Sp, the idea of some dispersion or expansion, generally quick, (especially with the addition of the letter r,) — as spread, spring, sprig, sprinkle, split, splinter, spill, &c. SI, the idea of a gently gliding or slightly perceptible motion : — as slide, slip, slip- pery, slime, sly, slow, sling, &c. Lastly, Sq, Sk, Scr, denote violent compression : — as squeeze, squirt, squeak, squeal, skreek, screw, &c. Some other interesting observations on the collocation of conso- nants, at the termination, and in the body, of words, are contained in the grammar of Wallis. His remarks, however, are chiefly con- fined to his own tongue. The President De Brosses,a has taken a wider range, with a similar object, and endeavoured to discover, why certain consonants, or a certain arrangement of consonants in a word, should designate certain sensible properties, in all lan- guages. Why, for instance, the st should enter into most words signifying firmness and stability : — as in the Sanskrit, stabatu, to stand, stania, a town, &c. ; in the Greek, «tt«a», a column, mpm, solid, immoveable, o-tsi/)«, sterile,remaining constantly without fruit, *4, a vein ; ^KtytBm, a burning river in the infernal regions : — in the Latin, flamma,flame ; fluo,\ flow ; flatus, wind ; fluctus, wave, &c.: —in the German, f 1 o s s e n, to float; f 1 o t e n, to play on the flute ; f I u s s, a river; f 1 u g, flight, &c.; and in the French and English words of the same meaning. Lastly, the idea of rough- ness and asperity is conveyed by the letter, r, as in the words rude, rough, rock, romp, &c. How different, for example, in smoothness are the two following lines, in which the S predomi- nates; from those that succeed them, where the R frequently and perhaps designedly, occurs: " Softly sweet in Lydian measures, Soon he soothed his soul to pleasures;" And — " Now strike the golden lyre again, A louder yet, and yet a louder strain ; Break his bands of sleep asunder ; And rouse him like a rattling peal of thunder." Dry den's " Alexander's Feas-t." The remarks that have been made, suggested by those of Wallis and of M. de Brosses, must not, however, be received too abso- lutely. In the condition in which we find languages at the present day, it would be impossible that they should hold good universally; but they will tend to show, that the physiology of the voice is intimately connected with this part of philology; and that the sounds emitted by the agency of particular parts of the vocal tube, may have led to the first employment of those sounds, according to the precise idea it may have been desired to convey; — gutturals, for example, for sounds conveying the notion of hollowness : — resisting dentals, that of obstacles, &c. The words mama and papa axe composed of a vowel and consonant, which are the easiest of enunciation, and which the child, consequently, pronounces and unites earlier than any other. Hence they have become the in- fantile appellations for mother and father with many nations. President de Brossesb affirms — and he has adduced numerous examples to prove his position — that in all ages, and in every » Op. citat. i. 261. b Op. cit. i. 244. 452 MUSCULAR MOTION. country, a labial, or, in default of it, a dental, or both together, are used to express the first infantile words papa and mama ; but, it is scarcely necessary to say, that the child, when it first pronounces the combinations, attaches no such meaning to them, as the parent fondly imagines. There is a rhetorical variety of onomatopoeia, frequently con- sidered under the head of alliteration, but by no means deriving its chief beauties from that source. It happens when a repetition of the same letter concurs with the sonorous imitations already described; as in the following line in one of the books of the JEneid of Virgil; — " Luc/an*es ventos tempesfatesque sonoras," in which the frequent occurrence of the letter of firmness and sta- bility, T, communicates the idea of the striking of the winds on objects. In the " Andromaque" of Racine, a line of this character occurs: " Pour qui sont ces serpens qui sifflent sur vos tetes,"a in which the sound impressed on the ear has some similarity to the hissing of serpents : and in the " Poeme des Jardins" of the Abbe De Lille, there is the following example: — " Soit que sur le Zimon une riviere /ente, Derou/e en paix les p/is de son onde indo/ente ; Soit qu'a travers les rocs un torrent en courroux Se brise avec fracas."b In the first two lines the liquid L denotes the tranquil flow of the river ; whilst in the two last, the letter of roughness and asperity, R, resembles the rushing of the stream like a torrent. The remarks already made will have exhibited the radical difference in the ideas communicated by the sound of those letters, by the common con- sent of languages. In the German this variety of expression is often had recourse to; and by none more frequently than by the poet Biirger.0 The English language affords a few specimens, but not as many as might be imagined. Of simple alliteration, there are many ; some that give delight; others that do violence to the sug- gestive principle ; but there are comparatively few, where the words are selected, which, by their sound, convey to the mind the idea to be communicated. The galloping of horses maybe assimi- lated by a frequent succession of short syllables ; slow, laborious progression by the choice of long; but, in the onomatopoeia in question, the words themselves must consist of such a collocation of •one consonant, or of particular consonants, as adds force to the a " For whom are those serpents that hiss o'er your heads." b Which may be translated as follows : — " If o'er the deep slime a river laves In peace the folds of its sluggish waves; Or o'er the rocks a torrent breaks In wrath obstrep'rous." c Art. Alliteration, and Onomatopoeia, in Encyclopedic, par Diderot, D'Alembert, &c, and in Allegemeine Deutsche Real-Encyclopadie fur die gebildeten Stande, (Con' versations Lexikon,) Aufl. 8, Leipz. 1837. VOICE — SINGING. 453 idea communicated by the words collectively. Of this, we have a good example, in the lines before cited, in which the repetition of the letter R, in the phonetic words, adds considerable force to the idea intended to be conveyed by the passage — " Break his bands of sleep asunder; And rouse him like a rattling peal of thunder," and in Byron's " Darkness," " Forests were set on fire — but hour by hour They fell and faded — and the crackling trunks Extinguish'd with a crash — and all was black." 6. SINGING. The singing voice differs from the other sounds produced by the glottis, in consisting of appreciable sounds, the intervals of which can be distinguished by the ear, and which admit of unison. Under the sense of hearing we endeavoured to show, that the musical ear is an intellectual faculty ; and that the ear is only the instrument for attaining a knowledge of sounds, which are subse- quently reproduced by the larynx, under the guidance of the intel- lect. In this respect, therefore, there is a striking resemblance between the faculty of music and that of spoken language. Like the spoken language, singing admits of considerable differ- ence, as regards intensity, timbre, &c. Voices are sometimes divided into the grave and the acute; the difference between them amounting to about an octave. The former is the voice of the adult male ; but it is capable of producing acute sounds, by assum- ing the falsetto, which Savarta conceives to be produced in the ventricles of the larynx; Bennati in the pharynx. The mode, however, in which the falsetto voice is produced is by no means determined. It has given rise to great diversity of views.b The acute voice is that of the grown female, of children, and of eunuchs. According to Pouillet,0 the gravest sound of the voice of a man makes 190 vibrations per second; the most acute 678 per second; whilst the female voice makes 572 vibrations for the gravest, and 1606 for the most acute. By adding all the tones of an acute to those of a grave voice, they are found to embrace nearly three octaves; but, according to Magendie, it does not appear, that such a compass of voice, in pure and agreeable tones, has ever existed in the same individual.*1 On the other hand, Biot calculated three octaves and a half to be the extreme range ; but this, Mr. Bishope says, he knows from experience to be too low an estimate. Some singers can descend sixteen tones below the medium; others can rise sixteen above it. The former are called tenor bass ; the lat- ter soprano; but hitherto no example has occurred of a person, who could run through the thirty-notes. The musician establishes certain distinctions in the voice ; such » Magendie's Journal de Physiologie, torn. v. Paris, 1825. b Miiller, Physiology, B. iv.; and Carpenter, Human Physiology, § 411,Lond. 1842. c Elemens de Physiologie Experimentale, torn. iii. 130, Paris, 1832. a Precis Elementaire, i. 262. « The London and Edinburgh Philosophical Magazine, for October, 1836, p. 272. 454 MUSCULAR MOTION. as counter, tenor, treble, bass, &c. We find it, also, differing con- siderably in strength, sweetness, flexibility, &c.a The singing voice, according to Bennati,b is not limited to the larynx; the pharynx is likewise concerned. The voice, elicited in those two different parts, has long been termed voce di petto, and voce di testa. Bennati calls the former laryngeal notes, or notes of the first register; the latter supra-laryngeal, or notes of the second register ; and Lepelletier designates them laryngeal and pharyngeal respectively, — comprising in the dependencies of the pharynx, — the tongue, the tonsils, and the velum palati, by means of which the latter class of sounds is elicited. The laryngeal voice, which is always more elevated by an octave in the female than in the male, is most commonly met with. It furnishes the types called, 1. Alt or soprano; 2. Counteralt; 3. Tenor; 4. Tenor Bass. The pharyngeal voice presents only modifications of these types. It is met with in but few persons in its finest development. It has usually been supposed to be formed by the superior liga- ments of the larynx, or in the ventricles ; but these gentlemen esteem it demonstrated, that it is formed at the guttural aperture, circumscribed by the base of the tongue, the velum palati, its pillars, and the tonsils. By it is produced the baritenor, the con- traltino tenor, and the soprano sfogato. Bennati concludes his memoir on the human voice by remarking, — that not only are the muscles ofthe larynx inservient to the modulation ofthe notes of song, but those of the os hyoides, tongue, and of the superior, ante- rior, and posterior part of the vocal tube are called into action, without the simultaneous and properly associated operation of which the degree of modulation requisite for song could not take place. When the voice is raised in the scale from grave to acute, a cor- responding elevation takes place in the larynx, towards the base of the cranium. By placing the finger on the pomum adami, this mo- tion can be easily felt; at the same time, the thyroid cartilage is drawn up within the os hyoides, and presses on the epiglottis ; the small space between the thyroid and the cricoid closes; the pharynx is contracted; the velum pendulum is depressed and carried for- wards ; the tonsils approach each other ; and the uvula is folded on itself. The reverse of these phenomena takes place during the descent of the voice.0 It has been already remarked, that the natural voice or cry is connected with the organization of the larynx. So far as it can be modified into tones independently of the participation of the intellect, a natural singing voice may be said to exist. To repeat, however, any song, requires both ear and intelligence; and, there- fore, singing may be said to have originated in social life. It can be employed, as.it is in many of our operas, to depict the different intellectual and moral conditions, " And bid alternate passions fall and rise." a Magendie's Journ.de Physiologie, x. 179. b Recherches sur le Mecanisme de la Voix Humaine, Paris 1832. • Bishop, and Bennati, in op. cit. GESTURES —MUSCLES OF THE FACE. 455 When the air is accompanied by the words, or is articulated, we are capable of expressing, by singing, any of the thoughts or feelings, that can be communicated by ordinary artificial language. Declamation is a kind of singing, except that the intervals between the tones are not entirely harmonic, and the tones them- selves not wholly appreciable. With the ancients, it has been imagined, declamation differed much less from singing than with the moderns, and that it probably resembled the recitative of the operas. The ingenious work of Dr. James Rush of Philadelphia,3 may be consulted on this subject, with great advantage. b. Gestures. Under this appellation, and that of muteosis, are comprised all those functions of expression, which are addressed to the sight and the touch. It comprises not only the partial movements of the face, but also those ofthe up- per extremities ; besides the in- numerable outward signs cha- racterising the various emotions. In many tribes of animals, the conventional language appears to* be almost, if not entirely, confined to the gestures; and even in man—favoured, beyond all animals, in the facility of communicating his sentiments by the voice — the language of gestures is rich and comprehen- sive. It is in the gestures of the face chiefly, that man far exceeds other animals. This is, indeed, in him, the great group of organs of expression. In animals, the function is distributed over dif- ferent parts ofthe body, the face assuming but little expression, whilst the animal is labouring under any emotion, if we make exception of the brute passion of anger and of one or two others. Hence it is, that, by some natura- lists, man has been defined, by way of distinction, " a laughing and crying animal." In animals, almost all the facial expression of internal feeling is confined to the eye and the mouth, but, in addition, the attitude of the body is » Philosophy of the Human Voice, Philad. 1827. Muscles of the Head and Face. 1. Frontal portion of the occipito-frontalis. 2. Occipital portion. 3. Aponeurosis. 4. Orbi- cularis palpebrarum, which conceals the corru- gator supercilii and tensor tarsi. 5. Pyramidalia nasi. 6. Compressor nasi. 7. Orbicularis oris. 8. Levator labii superioris alseque nasi. The figure 'is placed on nasal portion. 9. Levator labii superioris proprius; the lower part of the levatoran^uli oris is seen between muscles 10 and 11. 10. Zygomaticus minor. 11. Zygoma- ticus major. 12. Depressor labii inferioris. 13. Depressor anguli oris. 14. Levator labii inferioris. 15. Superficial portion of masseter. 16. Its deep portion. 17. Attrahens aurem. 18. Buccinator. 19. Attollens aurem. 20. Tem- poral fascia which covers in temporal muscle. 21. Retrahens aurem. 22. Anterior belly of digastricus muscle; the tendon is seen passing through its aponeurotic pulley. 23. Stylo- hyoid muscle pierced by posterior belly of digas- tricus. 24. Mylo-hyoideus muscle. 25. Upper part of sterno-mastoid. 26. Upper part of trapezius. The muscle between 25 and26 is the splenius.— {Wilson.) 456 MUSCULAR MOTION. variously modified, and the hair is raised by the panniculus car- nosus — as we see on the back of the dog, when the animal is enraged. In the human countenance, alone, in the state of society, can the passions be read, — the rest of the body being covered by clothing ; and even were it not, the absence of a coat of hair, and of a panniculus carnosus, would enable it to minister but little to expression. The skin of the face is very fine, and on certain parts, as the lips and cheeks, it is habitually more or less florid, and admits of considerable and expressive variations in its degree of colour. The union of the different parts, composing the face, gives occasion to numerous reliefs, which are called traits ox fea- tures ; and, beneath the skin, are many muscles, capable, by their contraction, of modifying the features in a thousand ways. To comprehend fully the physiology of the facial expression of the passions, a few observations on the muscles of the human face will be necessary. (Fig. 111.) The eyebrow is a part greatly concerned in expression ; and cer- tain muscles are attached to it for the purpose of moving it. The fasciculus of fibres, which descends from the frontal muscle, and is attached to the side of the nose, has been esteemed, by some, a distinct muscle, and to have a distinct operation. It draws the inner extremity of the eyebrow downwards. When the orbicu- laris palpebrarum, and the last muscle act, there is a heavy low- ering expression. If they yield to the action of the frontal muscle, the eyebrow is arched, and there is a cheerful, inquiring expres- sion. If the corrugator supercilii acts, there is more or less of mental anguish, or of painful exercise of thought. If it combines with the frontalis, the forehead is furrowed, and there is an up- ward inflection of the inner extremity of the eyebrow, which indi- cates more of querulous and weak anxiety. " The arched and polished forehead," says Sir Charles Bell — of whose elegant and accurate Essays we shall occasionally avail ourselves on this branch of our subject — " terminated by the distinct line of the eyebrow, is a table, on which we may see written, in perishable characters, but distinct while they continue, the prevailing cast of thought; and by the indications here, often the mere animal activity, displayed in the motions of the lower part of the face, has a meaning and a force given to it. Independent of the actions of the muscles, their mere fleshiness gives character to this part of the face. The brow of Hercules wants the elevation and form of intelligence; but there may be observed a fleshy fulness on the forehead, and around the eyes, which conveys an idea of dull brutal strength, with a lowering and gloomy expression, which accords with the description in the Iliad." Sir Charles separates the orbicularis palpebrarum into two muscles; — the outer, fleshy, circular band, which runs round the margin of the orbit; and the lesser band of pale fibres, which lies upon the eyelids. These last are employed in the act of closing the eyelids, but the former is 1 Essays on the Anatomy and Philosophy of Expression, 2d edit. Lond. 1824. GESTURES — MUSCLES OF THE FACE. 457 only drawn into action in combination with the other muscles' of the face in expressing passion, or in some convulsive excitement ofthe organ. In laughing and crying, the outer and more power- ful muscle is in action, gathering up the skin about the eye, and forcing back the eyeball itself. In drunkenness, the power of volition over this muscle is diminished; and there is an attempt to raise the upper eyelid by a forcible elevation of the eyebrow. The muscles ofthe nostrils are; 1st, the levator labii superioris alseque nasi, which, as its name imports, raises the upper lip and nostril; 2dly, the compressor nasi, a set of fibres which compress the nostril; and 3dly, the depressor aim nasi, which lies under the orbicularis oris, and whose function is indicated by its name. The three muscles serve to expand and contract the opening or canal of the nostril; moving in consent with the muscles of respiration; and thus the inflation of the nostrils indicates general excitement, and animal activity. The muscles of the lips are; 1st, the levator labii proprius, which raises the upper lip ; 2dly, the levator anguli oris, which raises the angle of the mouth ; and 3dly, the zygomatic muscle, which is inserted into the angle of the mouth. Sometimes an addi- tional muscle of the name exists : — zygomaticus minor. These last muscles raise the upper lip and the angle of the mouth, so as to expose the canine teeth. If they be in action contrary to the orbicularis oris, there is a painful and bitter expression; but if they be influenced along with the orbicularis oris, and orbicularis pal- pebrarum,— if the former of these muscles be relaxed, and the latter contracted, — there is a fulness of the upper part of the face, and a cheerful, smiling expression of countenance. The orbicu- laris oris closes the mouth; and, when allowed to act fully, purses the lips. The nasalis labii superioris draws down the septum of the nose. The triangularis oris or depressor labiorum, indicates, by its name, its function. The quadratus menti is a depressor of the lower lip. The levatores menti, by their action, draw up the chin, and project the lower lip ; and the buccinator is chiefly for turning the alimentary bolus in the mouth; and, in broad laughter, retracts the lips. The orbicularis muscle is affected in the various emotions of the mind; trembling and relaxing in both grief and joy : it relaxes pleasantly in smiling. The union of these various muscles at the angle of the mouth produces the fleshy prominence, noticed in those who have thin faces; and who are, at the same time, muscular. When the cheeks are fat and full, the action of these muscles produces the dimpled cheek. The angle ofthe mouth is full of expression, according as the orbicularis, or the superior or inferior muscles inserted into it, have the preponderance. Lastly, the temporal is a strong muscle, which raises the lower jaw. It is assisted by the masseter, a deep-seated muscle, which lies on the outside ofthe lower jaw, arises from the jugum, and is inserted into the angle of the jaw. vol. i. — 39 458 MUSCULAR MOTION. Fig. 112. Two different nerves are distributed to these muscles; — the fifth pair; and the portio dura or facial of the seventh ; the latter of which, according to the experiments of Sir Charles Bell, is concerned in the instinctive movements of expression ; and comparative anatomy exhibits, that the number and intricacy of these nerves vary in proportion to the animal'spower of expression. The nerves of the face and neck of the monkey are numerous, and have frequent connexions ; but, on cutting the seventh pair, or respiratory nerve of the face of Sir Charles Bell's system, the fea- tures are found to be no longer influenced by the passions. Yet the skin continues sensible, and the muscles of the jaws and tongue are capable of the actions of chewing and swallowing. If the re- spiratory nerve of one side be cut, the expression of that side is destroyed; whilst the chattering, grinning, and other movements of expression continue on the other. In a dog, too, if the respira- tory nerve of the face be cut, he will fight as bitterly, but with no retraction of his lips, sparkling of his eye, or drawing back of the ears. The face is in- animate, though the muscles of the face and jaws, so far as they are liable to be influenced through other nerves, continue their offices. The game-cock, in the position of fighting, spreads a ruff of fea- thers around his head. The position of his head and the raised feathers are the expres- sions of hostile excite- ment, but on the divi- sion of the respiratory nerve, the feathers are no longer raised, al- though the pugnacious disposition continues. It has been found, and moreover, that if the Distribu'ion of the Facial Nerve. Facial nerve, escaping from stylomastoid foramen, crossing ramus of lower jaw ; the parotid gland has been re- p-alvanif infliipnpp Lp moved in order to see the nerve more distinctly. 2. Posterior & v alJ1^ "Juuencc uc auricular branch; the digastric and stylo mastoid filaments are passed from One divid- seen near origin of this branch. 3. Temporal branches, com- j . • e , municatingwith(4)branchesoffrontal nerve. 5. Facial branches 6Q extremity Ot tne re- communicating with (6) infra-orbital nerve. 7, Facial branches, qnirntnrxT- noriro tr> the communicating with (8) mental nerve. 9. Cervico-facial ^"o-^'iy UCIVC uj Hie branches communicating with (10) superficialis colli nerve, and Other, the facial eX- forming a plexus (11) over submaxillary gland. Distribution of . ', branches of the facial in a radiated direction over side of face preSSlOn TetUmS ; aild, constitutes the pes anserinus. 12. Auricularis magnus nerve, ;n pprtnin nacoc nf in one of ascending branches of cervical plexus. 13. Occipitalis ^cl ldul Ld&es VI Ill- minor, ascending along posterior border of sterno-mastoid mus- complete hemiplegia cle. 14. Superficial and deep descending branches of cervical . r • . ' plexus. 15. Spinal accessory nerve, giving off a branch to ex in Which the eXpreS- ternal surface of trapezius muscle. 16. Occipitalis major nerve, „;„_ ,„„.,„„„„*„ _r 4l„ posterior branch of second cervical nerve. —{Wilson.) olve U1U veilieillb OI me GESTURES — NERVES OF THE FACE. 459 face were alone rendered impracticable, the disease was found to have implicated only the respiratory or facial nerve. The views of Sir Charles Bell, regarding the connexion, alleged by him to subsist, between the seventh pair and the associated movements of respira- tion, have, however, been contradicted by the experiments of Mr. Mayo,a and his inferences regarding the fifth pair—as being jointly a nerve of sensation and voluntary motion — have been considered to require qualification. By dividing the portio dura ofthe seventh pair in the ass, and on both sides instead of one, as done by Sir Charles Bell, Mr. Mayo found, that the nerve presides over simple voluntary motion only; and by a similar division of the second and third branches of the fifth, at their points of convergence, he showed, that the lips were deprived of sensation, not of motion. "No doubt, I believe," says Mr. Mayo, " is now entertained,that the inference which I drew from these experiments is correct; — namely, that the portio dura ofthe seventh pair is a simple volun- tary nerve, and that the facial branches of the fifth are exclusively sentient nerves." In the prosecution of his inquiries, Mr. Mayo observed, that the masseter muscle, the temporal, the pterygoids, and the circumflexus palati receive no branches from any nerve except the fifth, and yet that they receive twigs from the ganglio- nic portion of the nerve; and thence he concludes, that almost all the branches of the large or ganglionic portion of the fifth pair are nerves of sensation, whilst those ofthe small fasciculus ox ganglion- less portion are nerves of motion. This smaller portion of the fifth pair issues from the peduncles of the brain, constitutes a gangliform plexus with the inferior maxillary only, presents the common as- pect of most nerves of the body, and is distributed to the chief muscles concerned in the process of mastication. Hence it was termed by Bellingeri,b nervus masticatorius, and by Sir Charles Bell, long afterwards, the motor or manducatory portion of the fifth nerve. To this smaller fasciculus ofthe fifth, twigs from the ganglionic portion of the nerve are distributed. The ganglionic portion, and the portio dura of the seventh, Mr. Mayo conceives to be voluntary nerves to parts, which receive sentient nerves from the larger or ganglionic portion of the fifth.c The facial nerve, however, after it has passed through the parotid gland, becomes sensory also, owing to its having received a twig from the fifth pair.d Pathology affords us numerous examples of injury done to the facial nerve. In some of these cases, the nerve itself may be in a morbid condition in some portion of its course; in others, the part ofthe encephalon, whence the nerve originates, may be the seat of the lesion. The prognosis will, of course, vary according to the 1 Outlines of Human Physiology, 4th edit. p. 254, Lond. 1837. ■j Dissert. Inaugur. Turin. 1823 ; and Edinb. Med. and Surg. Journ. July, 1834. c See Panizza's Experiments upon the Seventh or Facial Nerve, in Lon. Med. Gaz, Sept. 26, 1835, and Miiller, Elements of Physiology, by Baly, p. 666, Lond. 1838; also, Valentin, Traite de Nevrologie, traduit par Jourdan, pp. 388, 417, Paris, 1843. DUt m0r<3 S0 tha" tha* ©f the O3S0- iate. "aoK&P^Mnd of the rest of the digestive sins seen situated in the niche be- tube ; and it is remarkable for the deve- tween the two pillars. 8. Root of 1 c ■. • i • i r tongue, partly concealed by the uvu- lopment of its veins, which form a very ^n^lou!:: i^oSSt distincl network. Around this is the of larynx. 12. Opening into the muscumr layer, the circular fibres of oesophagus. 13. External surface of „. • , r. i ■ ■ j j ■ ,. t oesophagus, h. Trachea.—cWilson.) wnich are otten divided into three mus- cles, — the superior, middle, and inferior constrictors. The longitudinal fibres form part of the stylo-pha- ryngei and palato-pharyngei muscles. The pharynx is raised by the action of the two last muscles, as well as by ail those that are situate between the lower jaw and os hyoides, which cannot raise the latter without, at the same time,raising the larynx and pharynx. These muscles are : — the mylo-hyoideus, genio-hyoideus, and the anterior belly of the digastricus. The oesophagus is a continuation ofthe pharynx ; and extends DIGESTIVE ORGANS. 481 to the stomach, where it terminates. Its shape is cylin- drical, and it is connected with the surrounding parts by loose and extensible cellular tissue, which yields readily to its movements. On entering the abdomen, it passes between the pillars of the diaphragm, with which it is intimately united. The mucous membrane, lining it, is pale, thin, and smooth ; forming longitu- dinal folds, well adapted for favouring the dilatation of the canal. Above, it is confounded with that of the pharynx ; but below, it forms several digitations, terminated by a fringed extremity, which is free in the cavity of the stomach. It is well supplied with mucous follicles. The muscular coat is thick ; its tex- ture denser than that of the pharynx, — and cannot, like it, be separated into distinct muscles, but consists of circular and longitudinal fibres ; the former of which are more internal, and very numerous; the latter ex- ternal, and less numerous. Fig. 121 exhibits the situation and arrangement of the two sets of fibres. 3. The stomach is situate in the cavity of the abdo- men, and is the most dilated portion of the digestiye tube. It occupies the epigastric region, and a part of the left hypochondre. Its shape has been compared, not inappropriately, to that of the bag of a bag-pipe. Fig. 122. Fig- 121- Section of the (Esophagus. a b. Internal cir- cular fibres. c. External lon- gitudinal fibres. Stomach seen externally. A A Anterior surface. B. Enlargement at the lower part. D. Cardiac orifice. E. Commence- ment of duodenum. F and C Coronary Vessels. H. Omentum. VOL. I. — 41 482 DIGESTION. It is capable of holding, in the adult male, when moderately dis- tended, about three pints. The left half of the organ has always much greater dimensions than the right. The former has been called the splenic portion, because it rests upon the spleen ; the latter the pyloric portion, because it corresponds to the pylorus. The inferior border of the stomach, which is convex, is termed the great curvature or arch ; the superior border, the lesser cur- vature or arch. The two orifices are the oesophageal, cardiac or upper orifice, formed by the termination of the oesophagus ; and the intestinal, pyloric or inferior orifice, which communicates with the small intestine. The three coats, which constitute the parietes of the stomach, are arranged in a manner the most favourable for permitting variation in the size of the organ. The outermost ox peritoneal coat consists of two laminae, which adhere but slightly to the organ, and extend beyond it, where they form the epiploons or omenta, the extent of which is in an inverse ratio to the degree of distension of the sto- mach. The omentum majus or gastro-colic epiploon is the part that hangs down from the stomach in Fig. 122. The mucous or lining membrane is of a whitish, marbled, red ap- pearance, having a num- Flg* 123, her of irregular folds, situ- ate especially along the inferior and superior mar- gins of the organ. These folds are evident, also, at their splenic extremity; and are more numerous and marked, the more the stomach is contract- ed. They are radiated to- wards the cardiac—longi- tudinal towards the py- loric, grifice. This mem- brane, like every other of the kind, exhales an albuminous fluid from a Vertical and Longitudinal Section of Stomach and Duodenum, miilf itnrlp nf rlolir«n tt> trilli made in such direction as to include the two orifices of Stomach. UJiu|,1iluucul ueilCcue Vim, 1. Oesophagus; upon its internal surface the plicated ar- rangement of cuticular epithelium is shown. $. Cardiac orifice of the stomach, around which the fringed border of cuticular epithelium is seen. 3. Great end of stomach. 4. Its lesser or pyloric end. 5. Lesser curve. 6. Greater curve. 7. Dilatation at lesser end of stomach which received from Willis the name of antrum of pylorus. This mav be regard- „ ed as the rudiment of a second stomach. 8 Rugs of the manY follicles, which are stomach formed by mucous membrane: their longitudinal di- p«5npr>inll\r nVmnrlnnr in rection is shown. 9. Pylorus. 10. Oblique portion of duodenum. ^P^^Y aDUndam in (Fig. ex- which are as perceptible in the stomach as in any part ofthe digestive tube. It contains, likewise, 11. Descending portion. 12. Pancreatic duct, and ductus com- the pyloric portlOll. ( munischoledochusclose to their termination. 13.Papilla upon -, r,A \ c l l which ducts open. 14. Transverse portion of duodenum. 15. 1*4.J Several, alSO, Commencement of jejunum. In interior of duodenum and ior inthp vioinitTr nf the jejunum, the valvuke conniventes are seen. — {Wilson.) U1 Ule VlCimiy OI me cardiac orifice, but in the rest of the membrane they are few in number. The pylorus, or the part at which the stomach terminates in the DIGESTIVE ORGANS. 483 small intestine, is marked, externally, by a mani- fest narrowness, as at 9, Fig. 123. Internally, the mucous membrane forms a circular fold, which has been called the valve of the pylorus, between the two laminae of which, a dense, fibrous tissue exists. This has been called, by some authors, the pyloric muscle. The muscular coat, which is situate without the mucous coat, — as in the parts ofthe digestive tube already described, — consists of several la- minae of fibres, less distinct than those of the oeso- phagus ; or rather more irregularly distributed. The most common opinion is, that there are three laminae: — an external, longitudinal series; a middle, transverse stratum; and an inner stra- tum with the fibres running longitudinally. Both circular and longitudinal fibres are separated from each other, especially in the splenic portion ; the separation augmenting or diminishing with the varying size of the stomach. The bloodvessels and nerves of the stomach are more numerous than those of any other organ of the body. The arteries are disposed along the curvatures. On the lesser curvature are, — Kglps^|jP the coronaria ventriculi, and the pyloric branch b of the hepatic artery ; on the great curvature, the ^ZffarfrZ fyiTus. right gastro-epiploic, which is a branch of the he- a. Magnified about three patic; and the left gastro-epiploic, — a branch of Jj^dswuifihVr Tacemi1 the splenic. The splenic artery, too, furnishes f°rm ends di|t«nd?d wi^ r r J_' » fluid, magnified about 20 numerous branches to the left cul-de-sac diameters. behind. These are called vasa brevia or gastro-splenic. The nerves of the stomach are of two kinds. Some proceed from the great sympathetic, from the coeliac plexus, and accompany the arteries through all their ramifications. Others are furnish- ed by the pneumogastric or eighth pair ; the two nerves of which surround the cardiac orifice like a ring. The number of the nerves, and the variety of sources whence they are derived, explain the great sympathetic influence exerted upon the stomach by affections of other parts of the system. It sympathizes, indeed, with every protracted morbid change in the individual organs; and hence it was termed, by Hunter, the centre of sympathies. Like the teeth, the human stomach holds a medium place be- tween that of the carnivorous and herbivorous animal. As the former makes use of aliment, which is more readily assimilated to its own nature, and more nutritious, it is not necessary, that it should take food in such large quantity as the latter, or that it should remain so long in the stomach. On this account, the organ is generally of much smaller size. On the other hand, the herbi- vora, subsisting solely upon grass, which contains but a small quantity of nutritious matter, and that not easy of assimilation, it 484 DIGESTION. is important that the quantity taken in should be ample ; that it should remain for some time in the organ, subjected to the action of its secretions ; and, in the ruminant class, be returned into the mouth, to undergo fresh mastication. In this class, the stomach, taken altogether, is of prodigious ex- tent. In the ox, which we may take as an example of the general structure of the organ, it consists of four separate compartments. The first stomach, A A, Fig. 125, is the ventriculus or paunch, which is much the largest of the four. Externally, it has two sacs or appendices; and, internally, it is slightly divided into four compartments. The second stomach is the reticulum, bonnet or honeycomb bag, B, which appears to be a globular appendix to the paunch. It is situate to the right of the oesophagus, G, and has usually a thicker muscular coat than the paunch. Its inner Section ofthe Stomach ofthe Ruminant Animal. lined by a true niU- DIGESTIVE ORGANS OF THE RUMINANTIA. 485 cous or secreting membrane. There is, in the interior arrange- ment ofthe stomachs of the ruminant animal, a singular provision, by which the food can be either received into the first and second stomachs or be carried on into the third, if its character be such as to be fitted at first for the action of trie omasum. From the oe- sophagus, in Fis- 127- is thrown back with velocity from the stomach into the mouth, where it is " rumi- nated," and then swallowed and passed on into the third sto- mach,— the groove or gutter being so contracted as to form a channel for its passage through the two first. In the third and fourth stomachs, more especially in the latter, true digestion takes place. When the food is of such a character as not to require rumination, it can be sent on directly into the third stomach, by the arrangement just described. In the bird tribes, we see an admirable adaptation ofthe struc- 41* 486 DIGESTION. Fig. 128. ture to the functions, which the digestive organs have to execute. Animals of this class may be divided into the granivorous and the carnivorous. It is in the former, that we are so much impressed with the organization of this part of their economy. The grain, on which they feed, although more nutritious than the grass, which constitutes the aliment of the herbivorous quadruped, re- quires equal difficulty in being assimilated to the nature of the being it has to nourish. Added to this, it is in such a condition, that the juices of the digestive organs cannot readily act upon it. The bird,having no masticatory apparatus within the mouth, the grain must of ne- cessity be swal- lowed whole. But we find, that lower down in the alimentary tube a powerful masticatory ap- paratus exists, which has fre- quently been considered as a part of the diges- tive stomach, but really seems de- stined for masti- cation only. The following is the arrangement of their gastric ap- paratus. The oesopha- gus terminates at the -bottom of the neck in a large sac — the ingluvies,ox crop Interior of the Gastric Apparatus of the Turkey. or craw— which is of the same structure with the oesophagus, but thinner. On the inner side ofthe crop are numerous glands, with very distinct orifices in large birds, which secrete a fluid to assist in the solution of the food. To the crop succeeds another cavity, in the shape of a funnel, called ventriculus succenturiatus, infun- dibulum or second stomach. This is seated in the abdomen, and is generally smaller than the former. It is usually thicker than the oesophagus, partly owing to its numerous glands, which are very large and distinct in many birds. In the ostrich, they are as DIGESTIVE ORGANS OF THE GALL1NACEA. 4S7 large as the garden-pea, and have very manifest orifices. The infundibulum terminates in the ventriculus callosus, gizzard or third stomach — the most curious of all the parts of the appa- ratus. Figs. 127 and 128 afford an external and internal view of the gastric apparatus of the turkey; a, representing the oeso- phagus immediately below the crop, covered with a cuticle ; b, the openings of the gastric glands in the second stomach, placed on a surface, that has no cuticular covering; c, horny ridges, between the gastric glands and the lining of the gizzard ; d, a minutely granulated surface, between the cavity of the gizzard and the duodenum; and e, the inner surface of the duodenum. The figure accurately represents the mode in which the second stomach terminates in the gizzard, and the latter in the duode- num ; the gizzard forming a kind of pouch depending from the alimentary canal. The gizzard is usually of a globular figure, flattened at the sides, and is considered to consist of four muscles, remarkable for their great thickness and strength ; — a large hemi- spherical pair at the sides and a small pair situate at the extremi- ties of the stomach. The gizzard is covered, externally, by a beautiful tendinous expansion : and is lined by a thick, strong, callous coat, which appears to be epidermeous in its characters. On this are irregularities, adapted to each other on the opposite surfaces. The cavity of the organ is remarkably small, when compared with its outward magnitude, and its two orifices, re- presented in Fig. 127, are very near each other. In the pouch, formed by the small muscles at the lower part of the gizzard, numerous" pebbles are contained, which seem to be indispensable to the digestion of certain tribes, by acting as substitutes for teeth. In the gizzard of the turkey, Mr. Hunter counted two hundred ; in that ofthe goose, one thousand. The prodigious power, with which the digastric muscle, as it has been termed, acts, and the callous nature of the cuticle, are strikingly manifested by certain experiments, instituted by the Academia del Cimento,h and by Redi, Reaumur,0 and Spallan- zani.d They compelled geese and other birds to swallow needles, lancets, and other hard and pointed substances. In a few hours afterwards, the birds were killed and examined. The needles and lancets were uniformly found broken off and blunted, without the slightest injury having been sustained by the stomach. In the carnivorous bird, the food being readily assimilated, in consequence of its analogy to the substance ofthe animal, the gas- tric apparatus is as simple as it is in the carnivorous mammalia. The oesophagus is of great size for receiving the large substances swallowed by these animals, and for enabling the feathers and other matters, that cannot be easily digested, to be rejected by the » Roget, Animal and Vegetable Physiology, edit, citat. ii. 126, b Exper. fatte nell' Acad, del Cimmto, 2da ediz.,Firenz. 1691. c Memoir de l'Acad. pour 1752, p. 266, and p. 461. & Experiences sur la Digestion, par Senebier, Genev. 1783. 488 DIGESTION. mouth. The stomach is a mere musculo-membranous sac; but the secretion from it is of a potent character, so as to enable the animal to dispense with mastication, and yet to admit of the sto- mach and intestines being disposed within a small compass, so as to give them the necessary lightness to fit them for flight. We can thus, from organization, generally discover the kind of food for which an animal is naturally destined; — in other words, we can say whether it is naturally granivorous, or carnivorous. There are some striking facts, however, exhibiting the signal changes exerted, even on organization, by restricting an animal to diet of a different character from that to which it has been accus- tomed ; or to one which is foreign to its nature. In birds of prey, the digastric muscle has the bellies, which compose it, so weak, that according to Sir Everard Home,3 nothing but an accurate ex- amination can determine its ex- istence. But if a bird of this kind, from want of animal food, be compelled to live upon grain, the bellies of the muscle become so large, that they would not be re- cognised as belonging to the sto- mach of a bird of prey. Mr. Hunter kept a sea-gull for a year upon grain; and found the strength of the muscle very much augmented. This wondrous adaptation of structure to the kind of food, which the animal is capable of obtaining, is elucidated in the cases of the South Ame- rican and the African ostrich. The former is the native of a more productive soil than the latter ; and, accordingly, the gas- tric glands are less complex and numerous; and the triturating organ is less developed.11 4. The intestines are the low- est portion of the digestive appa- ratus; constituting a musculo- membranous canal, which extends from the pyloric orifice of the stomach to the anus. The human intestines are six or eight times longer than the body ; and hence the number of convolutions in the abdominal cavity. They are attached to the vertebral column by folds of the peritoneum, called the mesentery ; and according to the length of these folds or duplicatures the intestine is bound down, or floats in the abdominal cavity. Their structure is nearly alike throughout: a mucous membrane.lines them: immediately 1 Lectures on Comparative Anatomy, i. 271, Lond. 1814. »> Ibid. i. 293. Fig. 129. Abdominal Viscera. A. A. Liver. B. Gall-bladder. C C. Sto- mach. D, D, D, D. Small intestines. E. Com- mencement of the large intestines. F, F, F. Colon. G. H. Sigmoid flexure of the colon. I, I. Rectum. K. Anus with sphincter ani. L, L. Levatores ani. DIGESTIVE ORGANS. 4S9 without this is a muscular coat; and, externally, a serous coat, formed by a prolongation of the peritoneum. The mucous mem- brane is soft and velvety, and is the seat of a similar secretion to that of other membranes of the same class. The muscular coat is composed of the two planes of fibres, so united that they cannot be separated, — the innermost consisting of circular, and the outermost of longitudinal fibres, the arrangement of which differs in the small and large intestines., The serous or peritoneal coat receives the * intestine between two of its laminae, which, in their passage to it, form the mesentery. The serous coat only comes in direct contact with the intestine at the sides and forepart. Behind, or on the mesen- teric side, is a vacant space, by which the vessels and nerves reach the intestine. These form their first network between the serous and muscular coats ; their second, between the muscular and mucous. Between the upper four-fifths of the intestinal canal, and the lower fifth, there is a well-marked distinction ; not only as regards structure and magnitude, but function. This has given occasion to a division of the canal into the small intestine and.the large ; and these, again, have been subdivided in the various modes, which will successively fall under consideration. As the small intestine fills so large a portion of the whole intestinal canal, its convolutions occupy considerable space in the abdominal cavity,— in the middle, the umbilical, and the hypogastric regions,—and terminate — in the right iliac region—in the large intestine (see Fig. 129). Its calibre differs in different parts ; but it may be re- garded on the average as about one inch. It is usually divided, arbitrarily, into three parts; — the duodenum, jejunum, and ileum. The duodenum is so called, in consequence of its length having been estimated at about twelve fingers' breadth. It is larger than the rest of the small intestine ; and has hence received, also, the name of the second stomach, and of ventriculus succenturiatus. It is more firmly fixed to the body than the other intestines ; and does not, like them, float loosely in the abdomen. In its course, until its termination in the jejunum, it describes a kind of Italic c, the concavity of which looks to the left. From this shape it has been separated into three portions ; — the first situate horizontally beneath the liver: the second descending vertically in front of the right kidney ; and the third in the transverse mesocolon. Its mu- cous membranea presents a number of circular folds, very near each other, which have been called valvulse conniventes. (Fig. 123.) By some anatomists, however, this name is not given to the irregular rugae of the mucous coat; but to the folds of the lining membrane of the jejunum. The valvulse are not simple rugae, passively formed by the contraction of the muscular coat. They are dependent upon the original formation of the mucous membrane; and are not 1 See, on the mode of exhibiting the epidermis, and on thi folliclesof the mucous coat of the stomach and intestines, Dr. Horner, General Anat. and Histology, 6th eiit. ii. 54, Philad. 1843 ; Dr. R. B. Todd, Lond. Med. Gaz., Dec. 13, 1839 ; and Dr. Sprott Boyd, Edinb. Med. and Surg-. Journ. vol. xlvi.; also, Wagner, Elements of Physiology, by Willis, § 134, Lond. 1842. 490 DIGESTION. Fig. 130. m^ to- aw effaced, whatever may be the distension of the intestines. On and between these duplicatures, the different exhalant and absorbent vessels are situate, forming, in part, the villi of the intestine. These villi give to the membrane a velvety ap- pearance, and are not simply composed of exhalants and absorbents, but of nerves ; all of which are distributed on a cellular and perhaps on an erectile tissue. In its healthy state, when successfully injected, the membrane appears to consist almost entirely of a cribriform intertexture of veins.3 It was formerly believed, that the villi are not supplied with bloodvessels. In each villus, however, there is a minute plexus of bloodvessels, the larger branches of which, when distended with blood, may even be seen by the naked eye. The mar- ginal illustration exhibits the vessel of one ofthe intestinal villi ofthe hare, from Wag- ner, after an extremely beautiful dry pre- paration by Dollinger, magnified about 45 diameters ; and Fig. 131, A, the apex of an intestinal villus from the duodenum of a human female, also magnified about 45 diameters. B exhibits a mesh of the vas- cular network, a a, filled up with delicate vesicular tissue. The most obvious use of these villi, as Dr. Rogetb and Dr. Horner suggested, is to increase the surface from which the se- cretion is prepared. Within the membrane are numerous follicles, which, with the ex halants, secrete a mucous fluid, called by Haller succus intestinalis. Their entire number in the whole alimentary canal is estimated by Dr. Horner to be 46,900,000. At about four or five fingers' breadth from the pylorus, the duodenum is perforated by the termination of the biliary and pancrea- tic ducts, which pour the bile and pan- creatic fluids into it. (Fig. 123.) Generally, these ducts enter the intestine by one open- ing ; at times, they are distinct, and lie along- side each other. The structure ofthe duo- denum is the same as that of the whole of the intestinal canal. The muscular coat is, however, thicker, and the peritoneal coat only covers its first portion, passes before the second, and is totally wanting in the a American Journal of the Medical Sciences, May, 1835, p. 62. b Op. cit. ii. 246. a, a. Veins filled with white injection. b, b. Arteries filled with red. A beautiful rete of capillaries between the two. have DIGESTIVE ORGANS. 491 third, which we have described as included in the transverse me- socolon. The other two portions of the small intestine are of consider- able length; the jejunum commencing at the duodenum, and the ileum terminating, in the right iliac fossa, in the first of the great intestines—the caecum. They occupy the middle and almost the whole of the abdomen, being surrounded by the great intes- tine E F F F G H I, Fig. 129. The jejunum is so called, from being generally found empty ; and the ileum,' from its numerous windings. The line of demarcation, however, between the duodenum and jejunum, as well as between the latter and the ileum, is not fixed : it is an arbitrary division. The jejunum has, in- ternally, the greatest number of valvulae conniventes and villi. The ileum is the lowest portion. It is of a paler colour, and has fewer valvulae conniventes. The jejunum is situate at the upper partof the umbilical region; the ileum at the lower part of it, extending as far as the hypogastric and iliac regions. The mucous membrane of the jejunum and ileum resembles, in essential respects, that of the duodenum ; the valvulas conniventes are, how- ever, more numerous in the jejunum than in the duodenum ; and, in the course of the ileum, they gradually disappear, and are replaced by simple longitudinal rugae. The villi, too, which are chiefly destined for chylous absorption, abound in the jejunum, but gradually disappear in the ileum. The mucous membrane of both is largely supplied with follicles, called the glands of Peyer, Brunner, and LieberkUhn, some, if not all, of which are probably concerned in secreting the succus entericus or succus intestinalis, — a mucous fluid, to which Haller attached unnecessary import- ance in digestion. Leluta estimates the number of these glands, in the small intestine, at 40,000. Dr. Horner considers the follicles, in every instance, to be formed of meshes of veins, the arteries en- tering only inconsiderably into their composition ; and about in the same proportion as they do in other erectile tissues.15 The glands, as they are termed, of the small intestine have long been known under the name of the follicles of LieberkUhn. These become especially evident when the mucous membrane is inflamed, being then filled with an opaque whitish secretion, which is absent in the healthy state.c The true glands of Brunner are chiefly in the duodenum. They are situate in the submucous tissue, where they form a continuous layer of white bodies surrounding the intestine. They are not larger than a hemp-seed : each consisting of numerous minute lobules, the ducts of which |: open into a common excretory duct. They ^^MK^SI^t" are complex structures, differing from the fltSui?th £ioiew!S Other glands and follicles Of the intestines, secretion in fever.-(BocAOT.) i Gazette Medicale, Juin, 1832. b Op. citat. ii. 54. c Boehm, cited in Brit, and For. Med. Rev., vol. 1 ; and Carpenter, Human Physi- ology, § 705, Lond. 1842. 492 DIGESTION. Conglomerate gland of Brunner, magnified 100 times. — {Boehm.) Nothing is positively known of the nature of their secretion, rhe glands of Peyer form large patches on the mucous membrane, where they are called glandulse agminatse. When examined in a healthy mucous membrane, they have the appearance of circular white, slightly raised, spots, about a line in diameter, over which the mucous membrane is lest studded with villi, and often wholly without them. On rupturing one of the white bodies, a cavity is found, but it has no excretory duct. It contains a grayish- white mucous matter. There are likewise solitary glands in both the small and large intestines. The use of these glands is un- known. Wagner3 has well observed, that the intimate structure of the whole of the glandular Fig. 134. bodies just mentioned requires farther study, and is almost as little known as their indi- vidual functions. The muscular coat of the small intestine is composed of circular and longitudinal fibres; and the outer coat is formed by the prolonga- tion ofthe peritoneum, which, after having surrounded the intestines, completes the me- sentery, by which the gut floats, as it were, in the abdo- minal cavity. The large intestine termi- nates the intestinal canal. It is much shorter than the small, and considerably more capacious,being manifestly intended, in part, as a reservoir. It is less loose in the abdominal cavity than the portion of the tube which we have described. It commences at the right iliac fossa, (Fig. 129, E,) ascends along the right flank, as far as the under, surface of the liver; crosses over the abdomen to gain the left*flank, along which it descends into the left iliac region, and thence through the pelvis, along the hollow of the sacrum, to terminate at the anus. Like the small intestine it is divided into three portions ; the czecum, the colon, and the rectum. The caseum or blind gut is the part of the great intestine into which the ileum opens. It is about four fingers' breadth in length, and nearly double the diameter of the small intestine. It occupies the right iliac fossa, in which it is bound down, so as not to be able to change its position. The extremity of the ileum joins the caecum, at an angle ; and if we examine the interior of the caecum, at the point of j unction, we find a valvular arrangement, 1 Elements of Physiology, translated by R. Willis, § 137, Lond. 1842. Portion of one of the patches of Peyer's glands from the end of the ileum: highly magnified. The villi are also shown. —{Boehm.) DIGESTIVE ORGANS. 493 which has been called the valve of Tulpius, valve of Bauhin,ileo- cascal valve, &c. Fig. 135 exhibits the nature of this arrangement. At the point of union of the two intestines, a soft eminence exists, flattened from above to below, and elliptical transversely, which is divided into two lips. One of these seems to belong to the ileum and colon—hence called ileo-colic ; the other to the ileum and caecum, and termed, ileo-csecal. From the disposition of these lips a valve results, so constituted, that the lips, which form it, separate when the faecal matters press from the small to the large intes- tine ; whilst they approximate, cross, and completely prevent all retrogression, when the faeces tend to pass from the great intestine to the small. At the extremities of this valve are smah tendons, which give it strength, and have been termed frsena or retina- culaofthe valve of Bauhin. Although this valvular arrangement prevents the ready return ofthe excrementitious matter into the Fig. 135. small intestine, we have many opportunities, in pathology, for discovering that it is not effectual in all cases. In stricture of the large intes- tine, stercorace- ous vomiting is a frequent con- comitant, and there have been instances of sub- , Commencement of the Large Intestines.— Valve of Tulpius. Stances, tniOWn AC. Small intestine. B. Large intestine. D. Appendix vermiformis into the rectum, c«ci. having been evacuated by the mouth. At the posterior and left side of the caecum, a small process de- taches itself, called, from its resemblance to a worm, appendix ver- miformis ; and, from its connection with the caecum, appendix cseci. It is convoluted, variable in its length, and attached, by its sides,;to the caecum. Its free extremity is impervious ; the other opens into the back part of the caecum. This appendage to the caecum has all the characters of an intestine. Various hypotheses have been in- dulged regarding its uses. Some have conceived it to be a reser- voir for the faeces, but its diminutive size, in the human subject, precludes this idea ; others have thought, that it secretes a ferment, necessary to faecal formation ; and others, again, a mucus for pre- ventin°- the induration, which might result from the detention of the faeces in the caecum. The opinion — that it is a mere vestige of the useful and double caeca, which exists in certain animals — vol. i. — 42 494 DIGESTION. is as philosophical as any. M. De Blainville,8 indeed, regards it as • the true caecum, and what is named the caecum as the commence- ment of the colon. It is manifestly of but little importance, as it has been found wanting or obliterated in many subjects, and has been extirpated repeatedly with impunity. The colon is by much the longest of the large intestines, (F F F G H, Fig. 129.) It is a continuation of the caecum, from which it cannot be distinguished; but is considered to commence at the termination of the ileum. From the right iliac fossa it ascends along the right lumbar region, over the kidney, to which it is con- nected. It is, in this part, called the colon dextrum, ascending ox right lumbar colon. From the kidney it passes forwards and crosses the abdomen in the epigastric and hypochondriac regions, being connected to the duodenum. This portion is called the great arch of the colon, or colon transversum. The right portion of the great arch is situate under the liver and gall-bladder ; and hence is found after death tinged yellow, owing to the transuda- tion of bile. The left portion of the arch is situate under the sto- mach ; and, immediately below it, are the convolutions of the jejunum. In the left hypochondre, the colon turns backward under the spleen, and descends along the left lumbar region, anterior to the kidney, to which it is closely connected. This portion is termed the colon sinistrum, descending or left lumbar colon. In the left iliac region, it forms two convolutions, which have been compared to the Greek s, or to the Roman s; and hence this part of the in- testine has been designated the sigmoid flexure, or Roman s, or iliac turn of the colon. This flexure varies greatly in length in different persons, extending frequently into the hypogastric region, and, in some instances, as far as the caecum. The colon, through its whole extent, is fixed to the body by the mesocolon. The coats of the great intestine are the same in number and structure with those of the small, but they are thinner, and not as easily separable by dissection. The mucous membrane is less villous and velvety. The most characteristic difference, however, in the general appearance of the great and small intestines, is the pouched or cellular aspect of the former. These pouches are reservoirs for the excrement, and in them it becomes more indu- rated, by the absorption of the fluid portions. In torpor of this part of the intestinal canal, the faeces are, at times, retained so long, that they form hard balls or scybala; and are not unfrequently the occasion of the inflammation of the lining membrane of the large intestine, which constitutes dysentery. The longitudinal mus- cular fibres are concentrated into three ligamentous bands or fas- ciculi, which run the whole length of the intestine. These fasci- culi, being shorter than the intestine, pucker it, and are the occasion of the pouched or saccated arrangement. The inner or circular muscular fibres are, like those of the small intestine, uni- formlyspread over the surface, and stronger than those ofthe latter. 1 De l'Organisation des Animaux, &c, Paris, 1825. DIGESTIVE ORGANS. 495 Lastly, in the great intestine, especially in the colon, are numerous processes of the peritoneum containing fat, and hence called appen- diculae epiploicae, or appendiculae pinguedinosas. These are seen in greatest abundance in the right and left lumbar portions of the colon. The rectum terminates the intestinal canal, and extends from the termination of the'colon to the anus. It commences about the fifth lumbar vertebra, and descends vertically into the pelvis, fol- lowing the concavities ofthe sacrum and coccyx; and,consequently, is not straight, as its name would import. At its upper part, there are a few appendiculae epiploicae ; and a small duplicature of the mesentery, called mesorectum, attaches it to the sacrum. It differs from the other intestines in becoming wider in its progress downwards, and in its parietes being thicker. The lower part of the mucous membrane exhibits several longitudinal folds or rugae, called " columns,'' which have been considered as the effect of the contraction of the circular fibres of the muscular coat. At the lower ends of the wrinkles between the columns are small pouches, from two to four lines in depth, the orifices of which point up- wards. They are occasionally the seat of disease, and when enlarged give rise to painful itching. The nature of this affection was first pointed out by Dr. Physick, and the remedy consists in slitting them open.a The longitudinal fibres of the muscular coat have a different arrangement from that which prevails in the other portions of the large intestine. They are distributed over the whole surface, as in the small intestine — or rather, as in the oeso- phagus. At the anus, an arrangement of the muscular coat pre- vails, which has been pointed out by Professor Horner.b The longitudinal fibres, having reached the lower margin of the internal sphincter, turn under this margin between it and the external sphincter, and then ascend upwards for an inch or two in contact with the mucous coat, into which they are finally inserted by fasciculi, which form the base ofthe columns ofthe rectum : many ofthe fibres, however, terminate also between the fasciculi of the circular fibres. The circular fibres are more and more marked, as they approach the outlet, and, by circumscribing the margin of the anus, they form the sphincter ani muscle. Immediately within the anus is the widest portion of the rectum ; and, in this part, accumulations of indurated faeces sometimes take place in old people to a surprising extent, owing to torpor of the muscular powers, concerned in the expulsion of the faeces. The mucous coat of the rectum is thick and red, and abounds in follicles. Lastly, there are a few muscles, which are concerned in the act of expelling the faeces. These require a short reference. 1. The sphincter ani or coccygeo-anal, which keeps the anus constantly closed, except during defecation. 2. The levator ani or subpubio- * Horner, General Anatomy and Histology, 6th edit. vol. 2, Philad. 1843; Dr. Reynell Coates, in Cyclopaed. of Pract. Med. and Surg. art. Anus, Philad. 1835 ; and Wilson's Anatomist's Vade Mecum, Amer. Edit, by Dr. Goddard, p. 510, Philad. l843> b Op. cit. p. 39. 496 DIGESTION'. coccygeus, which, with the next muscle, constitutes the floor of the pelvic and abdominal cavities. It restores the anus to its place, when pushed outwards during defecation. 3. The coccygeus or ischio-coccygeus, which assists the levator ani in supporting or raising the lower extremity of the rectum; and 4. The transversus perinei or ischio-perineal, some fibres of which unite both with the bulbo-cavernosi and with the sphincter ani muscles; and,con- sequently, it is associated slightly with the action of both one and the other. In regard, again, to the intestinal canal, we find, that man holds a medium place between the carnivorous and herbivorous animal, although approximating more to the latter. In the carnivorous animal —for reasons more than once mentioned — it is unnecessary that the food should remain long, and, accordingly, the canal is very short. In the herbivora, on the other hand, and for opposite reasons, the canal is long, and there is generally a large caecum and a pouched colon. Cuviera has given tables of the length of the canal, compared with that of the body ; but where the com- parison has been applied to man, the length of the body has included that of the legs. Instead, therefore, of the canal, in man, being considered to bear the proportion of six to one, it ought to be doubled, or to be as twelve to one ; a proportion somewhat greater than prevails in the simiae or ape tribe. It is not, how- ever, in length always, that the canal of the herbivorous exceeds that of the omnivorous animal; but, as a general rule, it may be affirmed, that the capacity of the canal is much more considerable. 5. The abdomen, in which the principal digestive organs are situate, and whose parietes exert considerable influence on the digestive function, will require a brief description. It is that division ofthe body, which is betwixt the thorax and pelvis; and is bounded, above, by the arch of the diaphragm; behind, by the vertebral column ; laterally, and anteriorly, by the abdominal muscles; and, below, by the ossa ilii, os pubis, and by the cavity of the pelvis. To connect the knowledge ofthe internal parts ofthe abdomen with the external, it is customary to mark certain arbitrary divisions on the surface, which have been called regions. The epigastric region is at the upper portion of the abdomen, under the p°oint of the sternum, and in the angle formed by the cartilages of the ribs. The hypochondriac regions are covered by the cartilages of the ribs. These three regions — the epigastric, and right and left hypochondre —constitute the upper division of the abdomen, in which are seated the stomach, liver, spleen, pancreas, duode- num, and part of the arch of the colon. The space surrounding the umbilicus, between the epigastric region and a line drawn from the crest of one os ilii to the other, is the umbilical region. Here the small intestines are chiefly situate. This region is'bounded by lines, raised perpendicularly to the spine of the ilium; and the a Legons d'Anatomie Comparee, Paris, 1799. DIGESTIVE ORGANS. 497 Fig. 136. lateral portions, on the outside of these lines, form the iliac regions, behind which again, are the lumbar regions, or the loins. In these, the colon and kidneys are chiefly situate. The hypo- gastric is, likewise,divided into three regions, — the pubic in the middle, in which the blad- der is situate ; and an inguinal on each side. The muscles, that constitute the abdominal parietes, are, first of all, above, the diaphragm, which is the boundary between the thorax and abdomen ; con- vex towards the chest, and con- siderably concave towards the abdominal cavity. Below, if we add the pelvic cavity,— which, as it contains the rectum, and muscles, concerned in the evacuation of the faeces, it may be proper to do, — the cavity is bounded by the perineum, formed chiefly of the levatores ani and coccygei muscles. Be- hind, laterally, and anteriorly, from the lumbar vertebrae round to the umbilicus, the parietes consist of planes of muscles, and aponeuroses in superposition Reflections ofthe Peritoneum- and united at the median line,T™'n3verselcof™. L. Liver. S. Stomach. C D. Transverse duodenum. P. by a SOlid, aponeurotic band,PTancreas- }■ Sma" intestines. K. Rectum. B. J t /■ 1 -i Urinary bladder. 1. Anterior layer of peritoneum, extending from the CartllagO-en- lining under surface of diaphragm. 2. Posterior 'f r.»-»i,'o ,-,f iu0 of-avr>nm *.-v tl-ialayer' •*■ The two layers passing to posterior bor- SHOrmiS 01 Hie Siemum IO Hie uer of liver, and forming the coronary ligament. alba 4. Lesser omentum: the two layers passing from ' under surface of liver to lesser curve of stomach. 5. The two layers meeting at greater curve, then ,' *. passing downwards and returning upon themselves, reckoning forming (O) greater omentum. 7^Transverse meso- pro- pubes, called the tinea The abdominal muscles perly so called, are, thp nlanp<5 from within tn vvith-colon- 8> Posterior layer traced upwards in front U1C pidlieis 1IUII1 W1U11I1 IO WIUl-ofD, the transverse duodenum ,andP, the pancreas, OUt,--- the greater Oblique lilUS- t0 become continuous with the posterior layer (2). 77, , n ,,. 2 jL 9. Foramen of Winslow ; the dotted line, bounding Cle, the leSSer Oblique, and trie this foramen inferiorly, marks the course of hepa- / / ii»i.oi.i./,/,'t. -nrliinli aro oitnaro l'c artery forwards, to enter between layers ofles- iranSVerSailb, WUILII die MlUcUt: ger omentum 10 Mesentery encircling small in- Chiefly at the Sides Of the abdo- tesline. ll. The rectovesical fold, formed by de- J . . , scending anterior layer. 12. The anterior layer meil • --and the rectUS and py- traced upwards upon internal surface of abdominal • / 7- „u;„u ~~„,-,^-.,- *u_ parietes to the layer (1), with which the examina- ramidahs, which occupy the fioncoinmenced/_ <»&„,,.) anterior part. The greater ob- lique, obliquus externus, ox costo-abdominalis ;—the lesser ob- lique, obliquus intemus or ilio-abdominalis, and the transversalis, transversus abdominis or lumbo-abdominalis, support and com- 42* 498 DIGESTION. press the abdominal viscera ; assist in the evacuation of the faeces and urine, and in the expulsion of the foetus ; besides other uses, connected with respiration and the attitudes. The rectus, pubio- sternalis or sterno-pubialis; and the pyramidalis or pubio-sub- umbilicalis, are more limited in their action, and compress the fore- part of the abdomen ; besides having other-functions. Lastly, a serous membrane — the peritoneum—lines the abdo- men, and gives a coat to most of the viscera. The mode, in which its various reflections are made, is singular, but easily intelligible from the accompanying figure. (Fig. 136.) It has neither beginning nor end, constituting, like all the serous membranes, a shut sac, and, in reality, having no viscus within it. If we assume the diaphragm as the part at which it commences, we find it continued from the surface of that muscle over the abdominal muscles, D ; then reflected, as exhibited by the dotted line, over the bladder, E; and, in the female, over the uterus, G; from thence over the rec- tum, F ; the kidney, H ; enveloping the intestine, B, and consti- tuting, by its two laminae, the mesentery, C ; giving a coat to the liver, A; and receiving the stomach between its duplicatures. The use of this membrane is to fix and support the different viscera ; to constitute, for each, a pedicle, along which the ves- sels and nerves may reach the intestine; and to secrete a fluid, which enables them to move readily upon each other. When we speak ofthe cavity of the peritoneum, we mean the inside of the sac; and when it is distended with fluid, as in ascites, the fluid is contained between the peritoneum lining the abdominal mus- cles, and that which forms the outer coat of the intestines. The omenta or epiploa are fatty membranes, which hang over the face of the bowels, and are reflections, formed by the peritoneum after it has covered the stomach and intestines. Their names will suffi- ciently indicate their situation: — the lesser epiploon or omen- tum,— the omentum hepato-gastricum ; the greater or gastro- colic ; and the appendices or appendiculae epiploicae, which last have already been referred to, and may be regarded as so many small epiploons. The abdomen is entirely filled by the contained viscera. There are several apertures into it; three, above, in the diaphragm, for the passag#of the oesophagus, vena cava inferior, and aorta ; one anteriorly in the course of the linea alba, but which is closed after birth, — the umbilicus; and two anteriorly and inferiorly; the one — the abdominal, inguinal or supra-pubian ring — which gives passage to the vessels, nerves, &c. of the testicle ; and the other — the crural arch —through which the vessels and nerves pass to the lower extremity. Lastly, two others exist in the infe- rior paries, for the passage of the obturator vessels and nerves, and of the sciatic arteries and nerves, respectively. Such is a brief view of the various organs concerned in digestion. To this might have been added the general anatomy of the liver and pancreas, — each of which organs furnishes a fluid, which is a material agent in the digestive process, —and of the spleen, which FOOD OF MAN". 499 has been looked upon by some as inservient, in some manner, to the same function. As, however, the function of these organs will be considered in another place, we defer their anatomy for the present. 2. OF THE FOOD OF MAN. The articles, inservient to the nourishment of man, have usually been considered to belong entirely to the animal and the vegetable kingdoms ; but there seems to be no sufficient reason for excluding those articles of the mineral kingdom that are necessary for the due constitution of the different parts of the body. Generally, the term food or aliment, is applied to substances, which, when received into the digestive organs, are capable of being converted into chyle; but, from this class again, the products of the mineral kingdom cannot, with entire propriety, be excluded. Animals are often characterized by the kind of food on which they subsist. The carnivorous feed on flesh ; the piscivorous on fish ; the insectivorous on insects ; the phytivorous on vegetables; the granivorous on seeds; the frugivorous on fruits ; the grami- nivorous and herbivorous on the grasses ; and the omnivorous on the products of both the animal and vegetable kingdoms. In anti- quity, we find whole tribes designated according to the aliment they chiefly used. Thus, there were the ^Ethiopian and Asiatic ichthyo- phagi or fish eaters ; the hylophagi, who fed on the young shoots of certain trees; the elephantophagi, and struthiophagi, the elephant and ostrich-eaters, &c, &c. We have already shown, that the digestive apparatus of man is intermediate between that of the carnivorous and the herbivorous animal; that it partakes of both, and that man may, consequently, be regarded omnivorous; that is, capable of subsisting on both the products of the animal and vegetable kingdoms ; — an important capability, seeing, that he is destined to live in arctic regions, in which vegetable food is not to be met with, as well as in the torrid zone, which is more favourable for vegetable, than for animal, life. The nature of the country must, to a great extent, regulate the food of its inhabitants, for although commerce can furnish us with articles of luxury, and with many, which are looked upon as necessaries, no nation is entirely indebted to it for its supplies; besides, numerous extensive tribes of the human family are denied the advantages of commerce, and compelled to subsist on their own resources. This is the great cause, why the Esquimaux, the Samoiedes, &c, live wholly on animal food ; and why the cocoa- nut, the plaintain, the banana, the sago, the yam, the cassava, the maize and the millet, form the chief articles of diet with the natives of torrid regions. In certain countries, the scanty supply of the useful and edible animals has given occasion to certain prohibitory dietetic rules and regulations, which have been made to form a part of the religious creed, and, of course, are most scrupulously observed. Thus, in 500 DIGESTION. Hindusthan, animal food is not permitted to be eaten ; but the milk of the cow is excepted. Accordingly, to ensure the necessary sup- ply of this fluid, the cow is made sacred; and its destruction a crime against religion. Amongst the laws of the Egyptians are similar edicts, but they seem to have been chiefly enacted for poli- tical purposes, and not in consequence of the unwholesome charac- ter ofthe interdicted articles. The same remark applies to many of the dietetic rules of Moses, for the regulation of the tables of the Hebrews. Blood was forbidden, in consequence, probably, of the fear entertained, that it might render the people too familiar with that fluid, and diminish the horror, which was inculcated against the shedding of blood : the parts of generation were excluded from the table, because the taste might interfere with the reproduction of the species, if it should become indulged, &c, &c. We have said, that, in his arrangement of the digestive organs, man is intermediate between the carnivorous, and the herbivorous, animal. Not the slightest ground is afforded, by anatomy, for the opinion of Rousseau, that man was, originally, herbivorous ; or for that of Helvetius,a that he was exclusively carnivorous. Broussonet affirms, that he is more herbivorous than carnivorous; since, of his thirty-two teeth, twenty resemble those ofthe herbivorous, whilst twelve only resemble those of the carnivorous animal. Accord- ingly, he infers, that, in the origin of society, his diet must have been exclusively vegetable. Mr. Lawrence,b too, concludes, that, whether we consider the teeth and jaws, or the immediate instru- ments of digestion, the human structure closely resembles that of the simiae — the great archetypes, according to Lord Monboddoc and Rousseau, of the human race — all of which are, in their natu- ral state, completely herbivorous. Again, we observe a wide discrepancy between man and animals in the variety of their aliments. Whilst the latter are generally restricted to either the animal or the vegetable kingdom, and to but a small part of one or the other, man embraces an extensive range, and by means of his culinary inventions, can convert a variety of articles from both kingdoms into materials of sustenance. But it has been argued by those, who are sticklers for the natural, that man probably confined himself, primitively, like animals, to one kind of food ; that he adhered to this whilst he remained in his natural state, and that his omnivorous practices are a proof of his degeneracy. Independently, however, of all arguments deduced from organization, experience sufficiently shows the inaccuracy of these assertions. If we trace back nations to their state of infancy, we find, that then, as in their more advanced condition, the diet was animal, or vegetable, or both, according to circumstances. Of this fact we have some signal examples, in a part of the globe where the lights of civilization have penetrated to a less extent than in most others; and where the influence of circumstances, a De l'Homme, ii. 17. x b Lectures on Physiology, Zoology, &c, p. 221, Lond. 1819. « On the Origin and Progress of Language, v. 1. FOOD OF MAN. 501 that prevailed in ancient periods, has continued, almost unmodi- fied, until the present time. Agatharchidesa describes the rude tribes, who lived on the coast of the Red Sea, and subsisted on fish, under the name ichthyophagi. Along both banks of the Asta- boras, which flows on one side of Meroe, dwelt another nation, who lived on the roots of reeds growing in the neighbouring swamps. These roots they cut to pieces with stones, formed them into a tenacious mass, and dried them in the sun. Close to them were the hylophagi, who lived on the fruits of trees, on vege- tables growing in the valleys, &c. To the west of these were the hunting nations, who fed on wild beasts, which they killed with the arrow. There were, also, other tribes, who lived on the flesh of the elephant and the ostrich,— the elephant'ophagi and stru- thiophagi. Besides these, he mentions another and less populous tribe, who fed on locusts, which came in swarms from the southern and unknown districts. The mode of life, with the tribes described by Agatharchides, does not seem to have varied for the last two thousand years. Although cultivated nations are situate around them, they have made no progress themselves. Hylophagi are still to be met with. The Dobenahs, the most powerful tribe amongst the Shangallas, still live on the elephant; and, farther to the west, dwells a tribe, who subsist, in the summer, on the locust; and, at other seasons, on the crocodile, hippopotamus, and fish.b In the infancy of society, mankind were probably almost wholly carnivorous; as the tribes least advanced in civilization still are at the present day. For a time, man, in most situations, may have confined himself to the vegetable banquet prepared for him by his bounteous Maker ; but, as population increased, the means of sub- sistence would be too scattered for him, and it would become ne- cessary to crowd together a number of nutritious vegetables into a small space, and to cultivate the earth, so as to multiply its pro- duce ; but this would imply the existence of settled habits and in- stitutions which could only arise after society had made some progress. Probably, much before this period, it would have been discovered, that certain of the beasts ofthe forest, and ofthe birds of the air, and some of the insect tribes, could minister to the wants of man, and form agreeable and nutritious articles of diet; and thus would arise their adoption as food. On the coasts of the ocean, animal food was perhaps employed from the period of the first settlement; as well as on the banks of the large streams which are so common in Asia, — the cradle of mankind. The fish, left upon the land after the periodical inundations of the rivers, or thrown on the sea-coast, ministered to their necessities, without the slightest effort on their part; and, hence, they had but little incentive to mental or corporeal exertion. This is the cause ofthe abject condition of the ichthyophagous tribes of old ; and of their comparatively low state of civilization at the present day.c Again, a De Rubro Mare, in Hudson's Geograph. Minor, i. 37. *> Bruce's Travels, 3d edit. v. 83. c The author, in Amer. Med. Intelligencer, i. 99, Philad. 1838. 502 DIGESTION. the savages, in various parts of the globe, live by the chase or the fishery ; and must, consequently, be regarded as essentially car- nivorous. It would not, however, be justifiable, to regard barba- rism as the natural state of man ; nor is it clear what the different writers on this point of anthropology have meant by the term. The Author of Nature has invested man with certain prerogatives, one of which is, the capability of rendering the organized kingdom sub- servient to his wishes and necessities; and, by the invention of the culinary art, of converting various organized bodies into whole- some and agreeable articles of diet, which thus become as natural to him as the restriction to one species of aliment is to the animal. It has been remarked, that the exclusive or predominant use of animal or of vegetable food has a manifest effect upon the physical and moral powers. Buffon affirms, that if man were obliged to abstain from flesh in our climates, he could not exist, or propagate his kind. Others, again, have depicted a state of ideal innocence, in the infancy of society, when man lived, as they conceive, en- tirely on vegetables; " His food the fruits ; his drink the crystal well;" unsolicitous for the future, in consequence of the abundant sub-' sistence spread before him; independent, and always at peace with his fellows, and with the other animals ; but he gradually sacrificed his liberty to the bonds of society; and cruelty, with an insatiable appetite for flesh and blood, were the first fruits of a depraved nature. Either immediately or remotely, all the physi- cal and moral evil, by which mankind are afflicted, arose from these carnivorous practices.* In point of fact, however, we find, that the countries, in which mankind are accustomed to be omni- vorous, or to unite animal with vegetable food, are those, that are most distinguished for both mental and corporeal endowments. The tribes, which feed altogether on animal food, —as the Lap- landers, the Samoiedes, the Esquimaux, &c, —are far inferior, in both these respects, to the European, or Europeo-American ; and the same may be said, although not to the like extent, of the vari- ous tribes in whose diet animal food predominates,—as the Indian inhabitants of our own continent. A similar remark is applica- ble to those, who live almost exclusively on vegetables, as the Hindoos, millions of whom are kept in subjection by a few Euro- peans.1' Attempts have frequently been made to refer the nutrient pro- perties of all articles of diet to a particular principle of a constant character, and which, alone, of all the elements, is entirely capa- ble of assimilation. Haller conceived this to be jelly ; — Cullen,c a "The principal patrons of this twaddle, in modern times — to say nothing of Pythagoras and the ancients - have been Gassendi, Rousseau, Wallis, Lamb, and Newton ; the last of whom, m the plenitude of his infatuation, asserts that real men have never yet been seen, nor ever will be, till they shall be content to subsist entirely on herbs and fruits and distilled water." _ Fletcher's Rudiments of Physiology 22 li. a. p. 121, Edinb. 1836. b Lawrence's Lectures, edit. cit. P. 216 * institutions of Medicine, Part i, Physiology, § 211,-Edinb. 1785. FOOD OF MAN. 503 thought it to be oily, or saccharine, or what seems to be a combi- nation of the two ; — Becker, Stahl, Fordyce,a &c, to be mucilage; Dumas,b mucus; and Halle, that it is a hydro-carbonous oxide, very analogous to gummi-saccharine matter !c It is probable, that there is no such particular principle as the one contended for ; and that, in all cases, the food is resolved into its elements, in the formation of the chyle or reparative fluid, which is sepa-' rated from it. To this conclusion we are necessarily impelled, when we reflect that the chyle can be formed from both animal and vegetable substances ; in other words, that, when vegetable substances are received into the digestive apparatus, they are capable of being converted into a substance, resembling the ani- mal they have to nourish ; and, on the other hand, the vegetable has the power of reconverting this animal matter into a substance of its own nature ; and hence the utility of manure in promoting vegetation. In an early part of this work, we had occasion to mention, that animals and vegetables are reducible into nearly the same ultimate elements, — oxygen, hydrogen, carbon and azote ; and all organized bodies probably possess the power of reducing substances, received as food, into their elements; and of recom- posing them, by virtue of affinities which are controlled by the vital agency. Of late, great light has been thrown on this sub- ject by the labours of the organic chemist. These have shown, that the chief proximate principles of animal tissues, and those that have been regarded as highly nutritious amongst vegetables have almost identically the same composition; and are modifica- tions of protein.d The following tables from Liebige exhibit the striking similarity in constitution, and in the proportion of con- stituents on different animal and vegetable compounds of organi- zation. Animal proximate principles, according to Mulder. Albumen. Fibrin. Casein. Carbon, - - - 54-84 * - - 54-56 - - - 54-96 Hydrogen, - - - 7-09 - - 690 - - - 7 15 Nitrogen, - - - 15-83 - - 15-72 - - - 15-80 Oxygen, - - - 21-23 - - 22-13 - - - 21-73 Sulphur, - - - 0-6S - * - 0-33 - - - 0 36 Phosphorus, - - 0-33 - - 0-36 100-00 100-00 100-00 Vegetable proximate principles, according to Scherer and Jones. Albumen, from wheat. Fibrin. Casein or Legumin, Carbon, - - 55-01 - - 54-603 - - 54-138 Hydrogen, - - 7-23 - - 7-302 - - 7-156 Nitrogen, - - 15-92 - - 15-809 - . 15-672 Oxygen, ) Sulphur, C - 21-84 - - 22-286 - - 23034 Phosphorus J 100-00 - - 100-000 - - 100-000 » Treatise on the Digestion of Food-, p. 84, 2d edit., Lond. 1791. >> Principes de Physiologie, i. 187, Paris, 1806. 0 Tiedemann, Physiologie des Menschen, iii. 95. a See page 27. 8 Animal Chemistry, Gregory's and Webster's edit., pp. 100, 283, and 301, Cam- bridge, Mass. 1842. 504 DIGESTION. As the different parts of the animal body contain a considerable portion of azote, a question has arisen regarding its source ; some believing, that it is obtained from the food, others by respiration. Magendiea instituted some experiments with the view of deter- mining the nutritive qualities of non-azoted substances. These consisted in feeding animals, for the necessary time, on diet whose chemical composition was rigidly determined. He fed a dog, three years old and in good condition, solely on pure white sugar and distilled water. For seven or eight days, the animal appeared to thrive well, was lively, and ate and drank with avidity. In the second week, he began to fall off, although his appetite con- tinued good, and he ate six or eight ounces of sugar in the twenty- four hours. In the third week, he became emaciated, his strength diminished, his gaiety was gone, and his appetite impaired. An ulcer formed on each eye, at the centre of the cornea, which sub- sequently perforated the cornea, and allowed the humours of the eye to escape. The emaciation went on progressively increasing, as well as the loss of strength; and, although he ate daily three or four ounces of sugar, the debility became so great, that he could neither chew nor swallow, nor execute the slightest movement. He died on the thirty-second day from the commencement of the experiment. On dissection, the fat was found to have entirely dis- appeared ; the muscles were reduced to less than five-sixths of their ordinary size; the stomach and intestines were much dimi- nished in size, and powerfully contracted ; and the gall and urinary bladders were filled with fluid not proper to them. These were examined by M. Chevreul, who found them to possess almost all the characters of the bile and urine of the herbivorous animal. The urine,in place of being acid, as it is in the carnivora, was sensibly alkaline, and presented no trace of uric acid or of phosphates. The bile contained a considerable proportion of picromel, like that of the ox and the herbivora in general. The excrements contained very little azote, which they usually exhibit in abundance. A second dog was subjected to the like regimen, and with similar results. He died on the thirty-fourth day of the experiment. A third experiment, having afforded analogous re- sults, Magendie concluded, that sugar alone is incapable of nourishing the dog. In all these cases, ulceration of the cornea occurred, but not exactly at the same period of the experiment. He next endeavoured to discover, whether these effects might not be peculiar to sugar ; or whether the non-azoted substances, gene- rally considered nutritious, might not produce like effects. He took two young and vigorous dogs, and fed them on olive oil and distilled water. For fifteen days they were apparently well; but, after this, the same train of phenomena occurred as in the other cases, except that there was no ulceration of the cornea. They died about the thirty-sixth day of the experiment. Similar expe- riments were made with gum Arabic, and with butter__one 1 Precis Elementaire, 2de e"dit. ii. 488, Paris, 1825. FOOD OF MAN. 505 of the animal substances which do not contain azote. The re- sults were identical. Although the character of the excrements passed by the different animals, indicated that the substances were well digested, Ma- gendie was desirous of establishing this in a positive manner. Accordingly, after having fed animals for several days on oil, gum, or sugar, he opened them, and found that each of these substances was reduced into a particular kind of chyme in the stomach; and that they afforded an abundant supply of chyle ; — that from the oil being of a manifest milky appearance, and that from gum or sugar transparent, opaline, and more aqueous than the chyle from oil; facts which proved, that if the various substances did not nou- rish the animals, the circumstance could not be attributed to their not having been digested. These results, Magendie thought, ren- der it likely, that the azote, found in different parts of the animal economy, is originally obtained from the food taken in. This is, however, doubtful. We have no proof, that the animals died simply from privation of azote. It is, indeed, probable, that the azote had little or no agency in the matter ; for there seems to be no reason why it should not have been obtained from the air in respiration, as well as from that contained between the particles of the sugar, where this substance was administered. It must be recollected, moreover, that the subjects of these experiments were dogs ; — animals which, in their natural state, are carnivorous, and, in a domestic state, omnivorous; and that they were restricted to a diet entirely foreign to their nature, and to which they had not been exclusively accustomed. Ought we, under such circumstances, to be surprised, that they should sicken and fall off? Between the period of the publication of the first and the second edition of his Prkcis EUmentaire de Physiologie, Magendie found that his deductions were not, perhaps, as absolute or demonstrative as he had at first imagined; and additional experiments induced him to conclude, — as Dr. Bostocka has since done, without being aware, apparently, of Magendie's observation, — "that variety and multiplicity of articles of food constitute an important hygienic rule." " This," Magendieb adds, " is indicated to us by our in- stinct, as well as by the changes that wait upon the seasons, as regards the nature and kind of alimentary substances." The ad- ditional facts, detailed by Magendie, are the following : — A dog, fed at discretion on pure wheaten bread, and drinking common water, does not live beyond fifty days ; whilst another, fed exclu- sively on military bread, —pain de munition, — seems, in no re- spect, to suffer. Rabbits or Guinea-pigs, fed on a single substance, as on wheat, oats, barley, cabbage, carrots, &c, commonly die, with every mark of inanition, in a fortnight ; and, at times, much earlier. When these same substances are given together, or in • Physiology, 3d edit. p. 561, Lond. 1836. " Op. citat. ii. 494 ; see, also, Wagner, Elements of Physiology, by R. Willis, § 223, Lond. 1812. VOL. I. — 43 506 DIGESTION. succession, at short intervals, the animals continue in good keep- ing. An ass, fed upon rice, lived only fifteen days, refusing his food for the last few days; whilst a cock was fed upon boiled rice for several months, without his health suffering. Dogs, fed exclu- sively on cheese, and others on hard eggs, lived for a long time ; but they were feeble and lean, losing their hair, and their whole appearance indicating imperfect nutrition. The substance, which, when given alone, appeared to support the rodentiaa for the great- est length of time, was muscular flesh. Lastly, Magendie found, that if an animal has subsisted for a certain time on a substance, which, when taken alone, is incapable of nourishing him, on white bread, for instance—for forty days, —it is useless,at the end of that time, to vary his nourishment, and restore him to his accustomed regimen. He will feed greedily on the new food presented to him ; but will continue to fall off; and will die at the same period as he would probably have done, if maintained on his exclusive regimen. That these effects were not owing to privation of azote, the same ob- server0 has since been amply satisfied. In the name of a committee to inquire into the nutritive properties of gelatin, he reported, as chairman ofthe committee, that gelatin, albumen, and fibrin — all of which are highly azoted,— when taken separately, nourish ani- mals for a very limited period only, and in an imperfect manner. They generally excite soon so insurmountable a disgust that they die rather than partake of them. These experiments have led to the too hasty conclusion, that the gelatinous tissues are incapable of conversion into blood. " The gelatinous substance," says Lie- big,0 "is not a compound of protein ; it contains no sulphur, no phosphorus, and it contains more nitrogen or less carbon than pro- tein. The compounds of protein, under the influence of the vital energy of the organs which form the flood, assume a new form, but are not altered in composition ; whilst these organs, as far as our experience reaches, do not possess the power of producing compounds of protein,by virtue of any influence, out of substances which contain no protein. Animals, which were fed exclusively with gelatin, the most highly nitrogenized element of the food of carnivora, died with the symptoms of starvation." " In short," he adds, " the gelatinous tissues are incapable of conversion into blood." Yet it has been shown above, that fibrin and albumen — both compounds of protein — when exhibited alone to animals, nourished them as imperfectly as gelatin. Independently of showing the necessity of variety of food for ani- mal sustenance, the experiments of Magendie exhibit some singular anomalies, and sufficiently demonstrate, that we have yet much to learn on the subject. A great deal,doubtless,dependson the habitsof the particular animal or individual; and on the morbid effects ex- a The rodentia are gnawing animals, having large incisors in each jaw, wilh which they divide hard substances. They are the rongeurs of the French naturalists. The squirrel, mouse, rat, Guinea-pig, hare, rabbit, beaver, kangaroo, porcupine, &c. belong to this division. b Comptes Rendus, Aovit, 1841. c Animal Chemistry, Amer. Edit, by Webster, p. 124, Cambridge, Mass. 1842. FOOD OF MAN. 507 cited by completely modifying the function of assimilation, as it has been ordinarily practised. It has been long known, that if a man, previously habituated to both animal and vegetable diet be restricted exclusively to one or the other, he will fall off, and be- come scorbutic; and yet, that he is capableof subsisting upon either one Or the other exclusively, provided he be restricted to it from early infancy, has been sufficiently shown by the reference already made to carnivorous and herbivorous tribes existing in different regions of our globe. The importance of variety of diet is illus- trated by the experiments, which Dr. Stark,a made upon his own digestive powers, and to which he ultimately became a martyr. His object was to discover the relative effect of various simple sub- stances, when used exclusively as articles of food for a long space of time. In all such cases, he found that the system was reduced to a state of extreme debility, and that there was not a single aliment, that was capable, of itself, of sustaining the vigour of the body for any considerable period. By this kind of regimen, Dr. Stark is said to have so completely ruined his own health, as to bring on premature death. The alimentary substances employed by man, have generally been classed, either according to the ultimate chemical elements entering into their composition ; or to the chief proximate principle or compound of organization. In the former case, they have been grouped into : — 1, those which contain azote, carbon, hydrogen, and oxygen ; 2, those which contain carbon, hydrogen, and oxy- gen ; and, 3, those which contain neither azote nor carbon. The first class will comprise most animal and many vegetable sub- stances: the second, chiefly vegetable substances; whilst water is perhaps the only real alimentary matter, that belongs to the third. The division proposed by Magendie,b and adopted by Dr. Paris,0 is according to the proximate principles, which predominate in the aliment. I. Amylaceous aliments ; wheat, barley, oats, rice, rye, Indian corn, potato, sago, salep, peas, haricots, lentils, &c. 2. Mucilaginous aliments ; carrot, salsify, beet, turnip, asparagus, cabbage, lettuce, artichoke, melon, &c. 3. Saccharine aliments; the different kinds of sugar, figs, dates, raisins, &c. 4. Acidulous aliments ; the orange, currant, cherry, peach, raspberry, strawberry, mulberry, grapes, prunes, pears, apples, tomatos, &c. 5. Oily and fatty ; cocoa, olives, sweet almonds, hazelnuts, walnuts, animal fats, oils, butter, &c. 6. Caseous aliments ; the different species of milk, cheese, &c. 7. Gelatinous aliments ; the tendons, aponeuroses, skin, cellular tissue, the flesh of very young animals, &c. 8. Albuminous aliments; the brain, nerves, eggs, &c. 9. Fibrinous aliments ; comprehending the flesh and blood of different animals. To these proximate principles, gluten may be added, which has been termed the most animalized of the vegetable principles. Ac- * The Works ofthe late Wm. Stark, M.D., &c, by Dr. J. C. Smyth, Lond. 1787. b Precis, &c. ii. 34. c A Treatise on Diet, 3d edit. p. 182, Lond. 1837, or Dunglison's'Amer. Med. Lib. Edit. Philad. 1841; or art. Dietetics, in Cyclopaedia of Practical Medicine, Lond. 1832. 508 DIGESTION. cording to Prout,8 it is separable into two portions, analogous to gelatin and albumen. It is very generally met with, though only in small proportion, in the vegetable kingdom ; — in all the fari- naceous seeds, in the leaves of the cabbage, cress, &c.; in certain fruits, flowers, and roots, and in the green fecula of vegetables in general; but it is especially abundant in wheat, and imparts to wheat flower the property of fermenting and making bread. Of the nutritious properties of gluten, distinct from other principles, we know nothing precise : the superior nutritious powers of wheat flour over those of all other farinaceous substances sufficiently at- test, that, in combination with starch, it is highly nutritive. Dr. Proutb arranges alimentary principles in four great divisions — the aqueous, saccharine, oleaginous, and albuminous. This has been taken as the basis for a classification by Dr. Pereira,c who admits twelve divisions: — the aqueous, mucilaginous or gummy, sac- charine, amylaceous, ligneous, pectinaceous, acidulous, alcoholic, oily ox fatty, proteinaceous, gelatinous, and saline. By the combi- nation of these alimentary principles and simple aliments, our ordinary articles of food or compound aliments are formed. Water forms the basis of all drinks; but it frequently contains in addition other substances. These has been classed as follows: — 1. Water, of different kinds. 2. Vegetable and animal juices and infusions, as lemon-juice, orange-juice, whey, tea, coffee, &c. 3. Fermented liquors, as wines, beer, cider, perry, &c.; and 4. Alcoholic liquors, as brandy, alcohol, kirsch-wasser, rum, gin, whiskey, arrack, &c, &c. Dp. Pereirad has recently proposed the following more complete classification :— 1. Mucilaginous, fari- naceous or saccharine drinks. 2. Aromatic or astringent drinks. 3. Acidulous drinks. 4. Animal broths, or drinks containing gela- tin and osmazome. 5. Emulsive or milky drinks ; and 6. Alco- holic and other intoxicating drinks. Water — as has been seen — is considered by him amongst the alimentary principles. An inquiry into the different properties of these various liquids does not belong to the physiologist. We may remark, however, that the arguments, regarding the natural, have been extended to this variety of aliments ; and it has been contended, that water is the most natural drink ; and that all others, which are the products of art, ought to be avoided. The remarks, we have already made on this subject, will be sufficient. Water was, doubtless,"at one period, the only beverage of man, as nakedness and the use of raw aliment, and the most profound ignorance ofthe universe was his original condition; but no one will be presumptuous enough to declare, that he ought to continue naked, abjure cookery, and be plunged into his primitive darkness, on the plea that all these » Chemistry, Meteorology, and the Function of Digestion, (Bridgewater Treatise,) Amer. Edit. p. 558, Philad. 1834. b On the Nature and Treatment of Stomach and Urinary Diseases, Lond. 1840. c A Treatise en Food and Diet, Amer. Edit, by Dr. C. A. Lee, p. 38, New York 1843. d Op. cit. p. 189. FOOD OF MAN. 509 changes are so many artificial sophistications.a Water is, unques- tionably, sufficient for all his wants ; but the moderate use of fer- mented liquors, even if habitual, except in particular constitutions, is devoid, we think, of every noxious result. They are grateful; and many of them are even directly nutritious, from the undecomposed sugar and mucilage which they contain. Beer has been termed, for this reason, not inaptly, " liquid bread."b With regard to dis- tilled spirits, no evil would result from their total rejection from the table. Although they may, by their action on the digestive organs, be the indirect means of nutrition, they themselves contain no alimentary property. They are received into the vessels of the stomach by imbibition; and always produce, when taken to any amount, undue stimulation. This may be productive of little or no mischief, provided they be only used occasionally; but, if taken habitually, serious visceral disorder may sooner or later ensue. Lastly. There are certain substances called condiments,employed in diet, not simply because they are nutritive, — for many of them possess no such properties, — but because, when taken with food capable of nourishing the'frame, they promote its digestion, correct some injurious property it possesses, or add to its sapidity. Dr. Paris has divided these into the saline, the spicy or aromatic, and the oily. It may be remarked, however, that certain articles are called, at times, aliments, at others, condiments, according as they constitute the basis or the accessory to any dish; — such are cream, butter, mushrooms, olives, &c. The advantage of condi- ments to animal digestion is strongly exemplified by many cases. The bitter principle, which exists in grasses and other plants, ap- pears to be essential to the digestion of the herbivora; — acting as a natural stimulant; and it has been found that cattle do not thrive upon grasses, which are destitute of it. Of the value of salt to the digestive function of his cattle, the agriculturist has ample experience; and the salt licks of our country demonstrate how grateful this natural stimulant is to the beasts of the forest. Charcoal, administered with fat, — as it is done, in rural economy for fattening poultry, in many parts of England, — strikingly ex- hibits the advantage of administering a condiment: the charcoal is a substance which of itself contains no nourishment, but it can put the digestive function in a condition for separating more nutritious matter from the food taken in, than it could otherwise accomplish. A similar effect is produced by the plan, — adopted for the same purpose in some parts of Great Britain, — of giving walnuts,coarse- ly bruised, with the shell, and cramming the animal with this diet. This is asserted, by many rural economists, to be the most effectual plan for fattening poultry speedily; the coarse shell, in passing along the mucous membrane of the chylopoietic organ, stimulates » See an article by the author in the American Quarterly Review, ii. 422, Philad. 1827 ; and Fletcher, op. citat. p. 121. b Kitchener's Invalid's Oracle, Amer. Edit. p. 136, New York, 1831. 43* 510 DIGESTION. it to augmented action, and a more bountiful separation of nutri- tious matter or chyle is the consequence. The aromatic condiments act in a similar manner. These few remarks on the food of man will introduce us to the mode in which the various digestive processes are accomplished. The more intimate consideration of alimentary substances, with their comparative digestibility, &c, will be found in another work, to which the reader is referred.3 3. PHYSIOLOGY OF DIGESTION. The detail entered into regarding the various organs concerned in digestion will have induced the anticipation, that the history of the function must be multiple and complex. The food, is not, in the case of the animal — as it is in that ofthe vegetable — placed in immediate contact with the being to be nourished; consequently an act of volition is necessary to procure it, and to convey it to the upper orifice of the digestive tube. This act of volition is excited by an internal sensation—that of hunger — which indicates to the animal the necessity for taking fresh nourishment into the system. The appetite and hunger, with the prehension or reception of food, must therefore be regarded part of the digestive operations. These may be enumerated and investigated in the following order: — 1st. Hunger, or the sensation, which excites us to take food. 2dly. Prehension of food, the voluntary muscular action, which intro- duces it into the-mouth. 3dly. Oral or buccal digestion, comprising the changes wrought on the food in the mouth. 4thly. Deglutition, or the part taken by the pharynx and oesophagus in digestion. 5thly. Chymification, or the action of the stomach on the food. 6thly. The action of the small intestine. 7thly. The action of the large intestine. And 8thly. Defecation or the expulsion of the faeces. All these processes are not equally concerned in the formation of chyle. It is separated in the small intestine : the first six conse- quently belong to it; — the remainder relate only to the excre- mentitious part of the food. The digestion of solid food requires all the eight processes. That of liquids is more simple ; com- prising only thirst, prehension, deglutition, the action of the sto- mach, and that of the small intestine. The fluid rarely reaches the large intestine. In inquiring into this important and interesting function, we shall first attend to the digestion of solids, and afterwards to that of liquids. 4. DIGESTION OF SOLID FOOD. a. Hunger. Hunger is really an internal sensation, the seat of which is invariably referred to the stomach. Like every internal sensation, it proceeds from changes in the very texture of the organ. It is not produced by any external cause ; and to it are applicable all * The author's Elements of Hygiene, p. 205, Philad. 1835. HUNGER. 511 those observations, which were made on the internal sensations in general. In its slightest condition, it is merely an appetite, (o^|«; Germ. E s s 1 u s t;) but if this be not heeded, the painful sensa- tion of hunger {Fames, xi/moc,) supervenes, which becomes more and more acute and lacerating unless food be taken. If this be the case, however, the uneasiness gradually abates ; and if addi- tional food be taken, a feeling of satiety is produced. The sensation usually occurs, in the healthy state, after the sto- mach has been for some time empty, having finished the digestion of the substances taken in at the previous meal. Habit has a great effect in regulating this recurrence ; the appetite always appearing about the time at which the stomach has been accustomed to receive food. This artificial desire may be checked by various causes; — by the exciting or depressing passions, by the sight of a disgusting object, or anything that induces intense mental emotion ; or it may be appeased by filling the stomach with substances that contain no nutritious properties. As, however, the feeling of true hunger arises from the wants of the system, the natural and instinctive sensation soon appears, and cannot be long postponed by any of these means. Hence, it has been proposed to make a distinction between the appetite and hunger; applying the former term to the artificial, the latter to the natural, desire. In these respects, there is certainly a wide distinction between them, as well as in the capriciousness, which occasionally characterizes the former, and gives rise to the most singular and fantastic preferences. The sensation of hunger varies in intensity according to different circumstances. It is more powerful in the child and the youth than it is in the adult, who has attained his full height. In the period of second childhood, it is urgent, probably owing to the diminished power of assimilation requiring that more aliment should be received into the stomach. In the state of disease, the sensation is gene- rally suppressed, and its place is often supplied by loathing or dis- gust for food: at times, again,its intensity makes it a true disease, as in bulimia, and in pica ; in the latter of which, the appetite is, at times, irresistibly directed to substances, which the person never before relished, or which are not edible,— as chalk, earth, slate pencil, &c. The appetite is also modified by the degree of exercise or inactivity, to which the individual has been subjected: — regu- lar exercise, and the exhilarating passions; a cold and dry atmo- sphere, &c, augmenting it, whilst it is blunted by opposite circum- stances. Long continued exertion, with a scanty supply of nou- rishment, if not continued so long as to injure the tone of the sto- mach, produces, occasionally, in adults, a voracious appetite and rapid digestion. Mr. Hunter has quoted, in illustration of this point, the following extract from Admiral Byron's narrative. After describing the privations he had suffered, when shipwrecked on the coast of South America, the admiral incidentally refers to their effect upon his appetite. "The governor," he says, "ordered a table to be spread for us with cold ham and fowls, which only we 512 DIGESTION. three sat down to, and in a short time despatched more than ten men with common appetites would have done. It is amazing, that our eating to that excess we had done from the time we first came among these kind Indians had not killed us, as we were never satis- fied, and .used to take all opportunities for some months after, of filling our pockets, when we were not seen, that we might get up two or three times in the night to cram ourselves."a Authors have distinguished, in hunger, the local from the general phenomena; but many of their assertions on these points appear to be imaginative. We are told by Adelonb and others, that the stomach becomes contracted, and that this change is effected by the sole action of its muscular coat; — the mucous or lining mem- brane becoming wrinkled, and the peritoneal coat, externally, per- mitting the organ to retire between its laminae. Such, MM. Tie- demann and Gmelinc assert, is the result, also, of their observations. Magendie,d however, affirms, that after twenty-four, forty-eight, and even sixty hours of complete abstinence, he has never witnessed this contraction of the stomach. The organ had always consider- able dimensions, especially in its splenic portion. It was not until after the fourth or fifth day, that it appeared to him to close upon itself, to diminish greatly in capacity, and to change its position slightly ; and these effects were not observed unless the fasting was rigorously maintained. At the same time that the stomach changes its shape and situation, the duodenum is said to be drawn slightly towards it; its parietes to appear thicker, — and the mucous follicles and nervous papillae to project more into its interior. Its cavity is void of food, and contains only a little saliva, mixed with bubbles of air, a small quantity of mucus, and, according to some, a little bile and pancreatic juice, which the traction of the duode- num has caused to flow into it. Much dispute has arisen as to whether the circulation of the blood in the stomach experiences any mutation. Dumase was of opinion, that when the organ is empty, it receives less blood than when full; either on account of the great flexion of the vessels in the former case, or on account of the compression, experienced by the nerves, in consequence ofthe contracted state of the organ. He thinks that, under such circum- stances, a part of the blood, which is distributed to that viscus, reflows into the liver, spleen, and omentum; and he regards these organs as diverticula for the blood ofthe stomach, especially as the liver and spleen are then less compressed, and the omentum more extensive, owing to the retraction of the stomach. Bichat denies both the fact and its explanation. He affirms that, on opening ani- mals suffering under hunger, he never observed the vessels of the stomach less full of blood, the mucous membrane less florid, or the a Byron's Voyage, p. 181 ; and Hunter on the Animal Economy, p. 196. b Physiologie de l'Homme, ii. 396 ; Diet, des Sciences Medicales, ix.; and Rullier, Art. Faim, in Diet, de Medecine, torn, viii., Paris, 1823. c Die Verdauung nach Versuchen, u. s. w. ; or French translation, by A.J. L. Jourdan, Paris, 1827. d Op. citat. ii. 25. « Principes de Physiologie, Paris, 1806. HUNGER. 513 vessels of the omentum more turgid. Is it not true, he adds, that the vessels of the stomach are more flexuous when the organ is empty: being connected with the serous coat, as well as the nerves, they are unaffected by changes of size in the organ ; besides, the retraction ofthe stomach could never be great enough to compress the nerves. He denies, moreover, that the liver and spleen are more free, and the omentum larger, whilst the stomach is empty, as the abdominal parietes contract in the same proportion as the stomach. Magendie,a however, contests this last assertion of Bi- chat. He affirms, on the faith of positive experiments, that the pressure, sustained by the abdominal viscera, is in a ratio with the distension of the stomach. If the stomach be full, the finger, in- troduced into the cavity of the abdomen through an incision in its parietes, will be strongly pressed upon, and the viscera will be forced towards the opening; whilst, if it be empty, the pressure is inconsiderable, as well as the tendency of the viscera to escape through the opening. During the state of vacuity ofthe organ, he remarked, that the different reservoirs in the cavity of the abdo- men, — as the bladder and gall-bladder, — were more easily filled by their proper fluids. With regard to the quantity of blood cir- culating through the stomach in the empty and full state, — he is disposed to believe, that it receives less in the former condition ; but, instead of its differing in this respect from the other abdo- minal viscera, he thinks, that such is the case with every organ in the abdomen. The general effects, said to be produced by hunger, in contra- distinction to the local, are ; — debility and diminished action of every organ : the circulation and respiration slacken ; the heat of the body sinks ; the secretions diminish, and all the functions are exerted with more difficulty, if we except absorption, which, it is affirmed, and with much probability, is augmented. If the absti- nence be so long protracted as to" cause death, the debility of the functions becomes real, and not sympathetic. Respiration and circulation languish; all the animal functions totter; whilst ab- sorption continues, and the blood is supplied by the decomposition of the different organs; — the fat, the various liquid matters, the tissues and the organs themselves being successively subjected to its action. It is obvious, however, that, with the constant drain perpetually taking place, this state of affairs cannot long exist; the blood becomes diminished in quantity, and insufficient in every respect to vivify the organs; the functions of the brain are per- verted, and, in many instances, we are told, the most furious deli- rium closes the scene ; whilst, at others, the miserable sufferer sinks passively into the sleep of death. Occasionally, again, so dreadfully painful are the sensations caused by protracted priva- tion of food, that the most violent antipathies and the dearest af- fections are overcome ; and numerous instances have occurred in which the sufferer has attacked his own species, his friends, his 1 Precis, &c. edit. cit. ii. 26. b Don Juan, oanto ii. 58. 514 DIGESTION. children, and even the substance of his own body. The horrible picture of the shipwreck, by Byron,a is not a mere romance. It is but the actual fact, expanded somewhat by the imagination ofthe poet. Dr. James Currieb has related the case of a person, who died of inanition from stricture of the oesophagus, the particulars of which may exemplify the phenomena, presented by some of those who perish from abstinence. The records of such cases are rare. From the 17th of October to the 6th of December, the patient was sup- ported, without the aid of the stomach, by means of broth clysters, and was immersed in a bath of milk and water. At one period he had a parched mouth : a blister discharged only a thin, coagu- lable lymph; and the urine was scanty, extremely high-coloured, and intolerably pungent. The heat of the body was natural and nearly uniform from first to last; and the pulse was perfectly na- tural until the last days. His sleep was sound and refreshing ; his spirits even ; and his intellect unimpaired, until the last four days of existence, when the clysters were no longer retained. Vision was deranged on the first of December, and delirium followed on the succeeding day ; yet the eye was unusually sensible, and the sense of touch remarkably acute. The surface and extremities were at times of a burning heat; at others, clammy and cold. On the fourth, the pulse became feeble and irregular, and the respira- tion laborious; and, in ninety-six hours after all means of nutri- tion as well as all medicine had been abandoned, he ceased to breathe. He was never much troubled by hunger. Thirst was, at first, troublesome, but it was relieved by the tepid bath. — This was one of the cases in which the patient sinks tranquilly to death. In others, the distressing accompaniments, above described, are met with ; and the death is that of the furious maniac. The period at which death may occur from protracted abstinence is dependent on many circumstances. As a general rule it may be assumed, that the young and robust will expire sooner than the older ; and this will have to be the guidance in questions of survivorship, that may arise when several individuals have perished together from this cause. The picture, drawn by Dante, of the sufferings and death of Count Ugolino della Gherardescha, who saw his sons successively expire before him from hunger, is in this respect true to nature.0 The sensation of hunger resembles every other internal sensa- * Don Juan, canto ii. 58. >> Medical Reports, &c. Amer. Edit. Philad. 1808. c « Now when our fourth sad morning was renew'd, Gaddo fell at my feet, outstretch'd and cold, Crying: —« Wilt thou not, father! give me food V There did he die ; and as thine eyes behold Me now, so saw I three fall, one by one, On the fifth day and sixth: whence in that hold, I, now grown blind, over each lifeless son Stretch'd forth mine arms. Three days I call'd their names, Then Fast achieved what Grief not yet had done." " Inferno," canto xxxiii. HUNGER. 515 tion in the mode in which it is accomplished. There must be im- pression, conduction, and perception. That the brain is the organ of the last part of the process is proved by all the arguments used in the case of the internal sensations in general. Without its inter- vention, in this, as in every other case, no sensation can be accom- plished. The stomach is the organ in which the impression is effected ; and by means of the nerves this impression is conveyed to the encephalon. The eighth pair or pneumogastric nerves have generally been regarded as the agents of this transmission ; and it has been affirmed by Baglivi, Valsalva, Haller, Dumas, Legallois, Chaussier, and others, that if these nerves be divided in the neck, although the stomach may be, in other respects, favourably cir- cumstanced for the development ofthe impression of hunger, and the brain ready for its reception, there is no sensation. MM. Leuret and Lassaigne,3 Dr. John Reid,b and Nasse,c however, deny that such effect follows the division of these nerves; and the former gentlemen affirm, that horses have eaten as usual, and apparently with the same appetite, after they had removed several inches of the pneumogastric nerves; and that they even continued to eat after the stomach was filled. To these experiments we shall have occasion to refer hereafter. They by no means exhibit, that this internal sensation differs from others; and that the three actions are not equally necessary for its accomplishment. A difficulty, which the physiologist has always felt, regards the precise nature of the action of impression. Its seat is clearly in the stomach. This was incontestably shown in a case of fistulous opening into the stomach, which fell under the care of Dr. Beau- mont, and to which we shall have frequent occasion to refer. When the subject of this case was made to fast until his appetite was urgent, it was immediately assuaged by feeding him through the aperture. To the stomach, indeed, all our feelings refer the sen- sation. It is dependent upon some modification occurring in the very tissue of the viscus; and in the nerves, which, as has been shown, are the sole agents in all the phenomena of sensibility. These nerves are spread over the stomach, so that the precise seat of the impression cannot be as accurately defined as in the case of the organs of external sense. Moreover, the nerves of the stomach proceed from two essentially different sources, — from the eighth pair, and from the great sympathetic. The question consequently arises: — on which of these is the impression made ? The experi- ment of cutting the eighth pair in the neck would appear to decide in favour of the former. As to the proximate or efficient cause of hunger, we cannot ex- pect to arrive at any satisfactory conclusion. It is a sensation ; and, like all sensations, necessarily inscrutable. Theories, however, as on all obscure topics, have been numerous, and these have generally * Recherches Physiologiques et Chimiques pour servir a l'Histoire de la Digestion, Paris, 1825. b Edinb. Med. and Surg. Journal, April, 1839. c Untersuchungen zur Physiologie und Pathologie, Bonn, 1835-6. 516 DIGESTION. been of a mechanical or a chemical nature. Some have attributed it to the mechanical friction of the parietes of the stomach against each other, inconsequence ofthe contraction ofthe organ ; in which state, they affirm, the mucous coat is rugous, and its papillae and follicles prominent. It is manifest, however, from the structure of the organ, that no such friction can possibly take place. Yet this view was embraced by Haller.a Dr. Fletcherb ascribes it to a kind of permanent though partial contraction ofthe muscular fibres of the stomach ;—"not that alternate general contraction and relaxa- tion, which produces a sensible motion of this organ, nor that perma- nent general contraction, which would serve to diminish its cavity, but that kind of permanent contraction, which takes place in certain fibres alone, and perhaps through a part of their length only, and by which these fibres are, as it were, drawn away from the others, or, in other words, a minor degree of cramp." Others, again, have accounted for the sensation by the action of the gastric juice, which is supposed to have a tendency to corrode the internal membrane. In proof of this, they refer to a case, mentioned by Hunter, in which the mucous membrane, in a man who died of fasting, was found corroded. The gastric juice is, however, incapable of eroding liv- ing animal matter; and the numerous cases which have occurred, since that of Hunter, have sufficiently shown, that the corrosion and perforation, which we meet with on dissection, are to be re- ferred to an action after death, and are,consequently, totally uncon- nected with the sensation felt during life. We have, indeed, no reason for believing that the gastric juice can ever attain a state of acridity, and act upon the surface by which it is secreted. It has been remarked, that it is a law of the animal economy, that no secretion acts upon the part over which it is destined to pass, provided such part be in a healthy condition. Yet Sommering0 ascribes the pain, from long-continued fasting, to the action of the gastric juice ; and Dr. Wilson Philipd is manifestly induced to be- lieve, that the influence of the gastric juice on the stomach is, in some mode or other, productive ofthe sensation : his remarks, how- ever tend simply to show, — what we have so many opportunities of observing,— that the sensation can be postponed by exciting vomiting, or by inducing, for the time, a morbid condition of the stomach. The unanswerable objection, however, to all these views is the fact — repeatedly proved by Dr. Beaumont,e and which the author had an opportunity of observing —that, in the fasting state there is little, if any, gastric juice in the cavity ofthe stomach. Dr. Beaumont thinks, that the sensation of hunger is produced by dis- tension of the vessels, which secrete the gastric solvent; but such distension, if it exist — which is by no means proved—must itself a Element. Physiol, xix. 2. b Rudiments of Physiology, part iii. by Dr. Lewins, p. 73, Edinb. 1837. « De Corp. Human. Fabric, torn. vi. Traject. ad Moenum, 1794—1801. << Experimental Inquiry into the Laws ofthe Vital Functions, 2d edit. Lond. 1818. e Experiments and Observations on the Gastric Juice, and the Physiology of Diges- tion, p. 57, Plattsburg, 1833. PREHENSION OF FOOD. 517 be consecutive on the nervous condition that engenders the sensa- tion ; the efficient cause of such condition has still to be explained. Bichat, again, attributed it to the lassitude or fatigue of the sto- mach, occasioned by the contraction of its muscular coat, when prolonged beyond a" certain time. In answer to this, it may be remarked, that, if any thing impede the nutrition of the body, hunger still continues, although the stomach may be distended. This happens in cases of scirrhous pylorus, where the nutritive mass cannot pass into the small intestine, to be subjected to the action ofthe chyliferous vessels, and the losses ofthe body cannot, therefore, be repaired; — facts which would seem to show, that hunger is a sensation, excited in the stomach by sympathy with the wants ofthe constitution ; and that it is immediately produced by some alteration in the condition of the nerves of the organ, which is inappreciable to us. It appears, from the experiments of Magendie,a that when the cerebrum and great part of the cere- bellum were removed in ducks, the instinct of seeking food was lost in every instance, and the instinct of deglutition in many : food, however, introduced into the stomach, was found to be digested. b. Prehension of Food. The arms and the mouth have been described as the organs of prehension. It is scarcely necessary to say, that the hands seize the food and convey it to the mouth under ordinary circum- stances ; but there are cases in which the mouth is the sole.or chief organ of prehension. Most animals are compelled to use the mouth only. When the food is conveyed to the mouth by the hands, it must open to receive it. The mode in which this is effected has given rise to much controversy; and, strange to say, is not yet considered determined. Whilst some physiologists have asserted, that the lower jaw alone acts in opening the mouth mode rately ; others have affirmed, that both the jaws separate a little ; the lower, however, moving five or six times as much as the upper. That the latter is the correct view can be proved by positive expe- riment. If, when the mouth is closed, we place the flat side ofthe blade of a knife against the teeth of both jaws; and, holding the knife immoveably, separate the jaws ; we find, that both jaws move on the blade ; but the lower to a much greater extent than the upper. Now, as the upper jaw is fixed immoveably to the head, the whole head must, of necessity, participate in this move- ment ; and the question arises, what are the agents that produce it ? Some attribute it to a slight action ofthe extensor muscles of the head ; and they affirm, that whilst the depressors of the lower jaw carry it downwards, the extensors of the head draw the head slightly backwards, and thus raise the upper jaw. Magendieb and Adeloir2 assert, that when the mouth is opened moderately, the upper jaw does not participate ; but, that if the motion be " forced" or extensive, the upper jaw participates » Precis, &c. ii. 168. b Op. citat. ii. 43. c Op. citat. ii. 408. vol. I. — 44 518 DIGESTION. slightly. The experiment, however, with the knife, which is ad- duced by Adelon himself, completely overthrows this notion, and shows, that both jaws act, whenever the mouth is slightly opened. Magendie agrees with those who consider, that, whenever the upper jaw is raised, it must be by the head being thrown back on the verte- bral column ; and he properly remarks, that where there is a physi- cal impediment to the depression of the lower jaw,the mouth must be opened solely by the retroversion of the head on the spine. Ferreina conceived, that the motion ofthe upper jaw is occasioned by the action ofthe stylo-hyoideus muscle, and of the posterior belly of the digastricus ; and he affirms, that whilst the anterior fas- ciculus or belly of the digastricus depresses the lower jaw ; the posterior belly, with the stylo-hyoideus, carries the head backwards, and, with it, the upper jaw. The attachments, however, of these muscles sufficiently show, that they cannot be the agents: the mas- toid process, to which the posterior belly of the digastric muscle is attached, is near the articulation of the head with the atlas; whilst the styloid process, to which the stylo-hyoideus is attached, is anterior to the articulation, and its effect ought, therefore, to be to depress the upper jaw. The view of Professor Chaussier is the most probable. He ascribes the slight elevation of the upper jaw to the mechanical arrangement of the joint of the lower jaw. The temporo-maxillary articulation is not formed by a single condyle, but by two, which are so disposed, that the lower cannot roll downwards during the depression of the lower jaw, without caus- ing the upper condyle to roll upwards, and, consequently, to slightly elevate the upper jaw. Under ordinary circumstances, then, the jaws cannot be at all separated without both participating; but if we determine to fix the upper jaw we can make the lower the sole agent. As soon as the food is introduced into the mouth, the jaws are closed to retain it, and subject it to mastication. Frequently, how- ever, they assist in the act of prehension, as when we bite into a fruit, to separate a portion from it; — the incisor teeth acting, in such case, like scissors. This is chiefly produced by the contrac- tion of the muscles that raise the lower jaw ; and it is probable, that the action of the stylo-hyoideus is concerned in this move- ment ; — drawing the head and upper jaw with it downwards and forwards. The levator muscles of the jaw act here with great dis- advantage ; — the lower jaw representing a lever of the third kind ; the fulcrum being in the joint; the power at the insertion of the levator muscles ; and the resistance in the substance between the teeth. The arm ofthe resistance is, consequently, the whole length ofthe lever ; and we can readily understand, why we are capable of developing so much more force, when the resistance is placed between the molares; and why old people, — who have become toothless, and are, consequently, constrained to bite with the ante- rior part of the jaws, — the only portion that admits of contact, — cannot bite with any degree of strength. a Memoir, de l'Acad. des Sciences, pour 1744. PREHENSION OF FOOD. 519 The size of the body, put between the incisor teeth, influences the degree of force that can be brought to bear upon it. When small, the force can be much greater, as the levator muscles are inserted perpendicularly to the lever to be moved ; and the whole Fig. 137. Action ofthe Lower Jaw in prehension. A. The frontal bone. B. The temporal. C The parietal. D. The occipital. E. The coronoid process ofthe lower.jaw, to which the temporal muscle is attached. F. The condyloid process or head of the lower jaw. G. The lower jaw. H. The mastoid process. I. The upper jaw. J. The cheek bone. K. The orbit. L. The meatus auditorius externus. L*. The coronal suture. M. The squamous suture. N. The lambdoidal suture, g. The lower jaw depressed. of their power is advantageously exerted; but if the body be so large, that it can scarcely be received into the mouth, and be resist- ing, withal, the incisors can scarcely penetrate it; — the insertion of the levator muscles into the jaw being rendered very oblique ; and the greater part ofthe force they develope being consequently lost. This will be readily seen by the illustration, Fig. 137. When the mouth is closed, or nearly so, the masseter, and temporal mus- cles, represented respectively by the lines B E and J j, are inserted nearer the perpendicular ; but when the lower jaw is depressed, so that the situation of these muscles is represented by the dotted lines B e and J;, the direction, in which the muscles act, will be much more oblique, and, therefore, more disadvantageous. When the muscles of the jaws are incapable, of themselves, of separating 520 DIGESTION. the substance, as in the case of the apple, the assistance of the muscles of the hand is invoked ; whilst the muscles on the poste- rior part of the neck, which are inserted into the head, draw it backwards; and, by these combined efforts, the substance is forci- bly divided. c. Oral or buccal digestion. The changes, effected upon the food in the mouth, are important preliminaries to the function, which has to be executed in the stomach and duodenum. As soon as the food enters the cavity, it is subjected to the action of the organ of taste ; and its sapid quali- ties are duly appreciated. By its stay there, it also acquires nearly the temperature of the cavity. This is, however, a change of little moment, unless the food is so hot, that it would injure the stomach, if passed rapidly into it. Under such circumstances, it is tossed about the mouth, until it has parted with its caloric to various por- tions of the parietes of the cavity ; and then, if in a fit state for the action of deglutition, it is transmitted along the oesophagus ; but the most, important parts of oral digestion are the movements of mastication and insalivation; by which the solid food is commi- nuted, and imbued with the secretions that are poured into the interior of the mouth, and which we have shown to be of a very compound character. Under the sense of taste, the influence of the agreeable or dis- agreeable character ofthe food upon the digestive function was ex- patiated upon. It is unnecessary, therefore, to do more than allude to the subject here. We find them mutually influencing each other: whilst a luscious aliment excites us to prolonged mastication, and the salivary glands to augmented secretion, the masticatory and salivary organs, by dividing and moistening the food, permit the organs of gustation to enjoy the savour in successive applications. When the food is received into the mouth, if it be sufficiently soft, it is commonly swallowed immediately ; unless the flavour is delicious, when it is detained for some time. If solid, and, espe- cially, if of any size or density, it is divided into separate portions, or is chewed, — the action constituting mastication. If the con- sistence of the substance be moderate, the tongue, by being pressed strongly against the bony palate, is sufficient to effect this division ; bruising it, and at the same time, expressing its fluid portions. If the consistence be greater, the action of the jaws and teeth is re- quired. For this purpose, the lower jaw is successively depressed and elevated by the action of its depressors and levators; and the horizontal or grinding motion is produced at pleasure by the action of the pterygoid muscles. Whilst these muscles are acting, the tongue and the cheeks are incessantly moving, so as to convey the food between the teeth, and insure its comminution. Mas- tication is chiefly effected by the molares. There is advantage in using them, independently of their form, in consequence of the ORAL DIGESTION. 521 arm of the resistance being much shortened, as has already been shown. The teeth are well adapted for the service they have to perform. The incisors, as their name imports, are used for cutting; hence their coronee come to an edge ; the canine teeth penetrate and lace- rate, and their coronse are acuminated ; whilst the molares bruise and grind, and their touching surfaces are tuberous. The first, having usually no great effort to sustain, are placed at the extre- mity of the lever ; the latter, for opposite reasons, are nearest the fulcrum. To preclude displacement, by the efforts they have oc- casionally to sustain, they are firmly fixed in the alveoli or sockets; and, as the roots are conical, and the alveoli accurately embrace them, the force, as in the case of the wedge, is transmitted in all directions, instead of bearing altogether upon the jaw, which it would do, were the fangs cylindrical. The molar teeth, having the greatest efforts to sustain, are furnished with several roots; or with one, which is extremely large. The gums add materially to the solidity of the junction of the teeth with the jaw. They are themselves formed of highly re- sisting materials, so as to withstand the pressure of hard and irre- gular substances. Whenever they become spongy, and fall away from the teeth, the latter become loose ; and are frequently obliged to be extracted, in consequence ofthe loose tooth acting as an ex- traneous body, and inflaming the lining membrane of the alveolus. The arrangement of the jaw is likewise well adapted to the func- tion ; the lower jaw passing behind the upper at its anterior part; but coming in close contact at the sides, where mastication is chiefly effected. During the whole time that mastication is going on, the mouth is closed ; — anteriorly, by the lips and teeth, which prevent the food from falling out of the cavity; and, posteriorly, by the velum palati, the anterior surface of which is applied to the base of the tongue. At the same time, the food is undergoing admixture with the vari- ous fluids poured into the mouth, and particularly with the saliva, the secretion of which is augmented, not only by the presence of food, but even by the sight of it, especially if the food be desira- ble ; — giving rise to what is called " mouth-watering." It is pro- bable, that, independently of the mental association, the action of the secretory organ's is increased by the agitation of the organs themselves during the masticatory movements. It has, indeed, been asserted, that the parotid glands are so situate, as regards the jaws, that the movement ofthe lower jaw presses upon them, and forces out the saliva; but Bordeu and J. Cloquet have demon- strated, both anatomically and by experiment, that such is not the case.a It has been supposed by some, that admixture with the saliva communicates to the food its first degree of animalization; or in other words, its first approximation to the substance of the animal a Adelon, op. cit. ii. 418. 44* 522 DIGESTION. it has to nourish. Such are the opinions of Professor S. Jackson and of M. Voison.b The former asserts, that he has ascertained posi- tively, that the saliva exerts a very energetic operation on the food,, separating, by its solvent properties, some of its constituent princi- ples, and performing a species of digestion. MM. Tiedemann and Gmelin, too, are of opinion, that the water, and the carbonate, and acetate of potassa and soda, and the chlorides of potassium and so- dium, ofthe saliva contribute to soften and dissolve the food ; whilst the azoted materials — the sal i vary and albuminous matters — com- municate to it a first degree of animalization. It is more probable, however, that the great use of mastication and insalivation is to give the food the necessary consistence, in order that the stomach and small intestine may exert their action upon it in the most favourable manner; and that, consequently, the changes effected upon the ali- ment in the mouth, are chiefly of a mechanical character. In the case of many substances—as sugar, salt, &c.—a true solution takes place in the saliva ; and this probably happens to sapid bodies in general; the particles being separated by imbibing the fluid. Krimer,c of Leipzig, held in his mouth a piece of ham, weighing a drachm, for three hours. At the expiration of this time, the ham was white on its surface, and had increased in weight twelve grains. Krimer, it may be remarked, believes, that the tears assist in diges- tion, and that they flow constantly by the posterior nares into the stomach. It would seem, too, that an important action of the saliva is the conversion of starch into sugar. From one drachm of starch, Dr. WTrightd obtained in twelve hours, at a temperature of 98°, by admixture with saliva, thirty-one grains of sugar. This probably takes place by the action of some azoted or nitrogenized secretion, like pepsin in stomachal digestion.* Both mastication and insalivation are of great moment, in order that digestion shall be accomplished in perfection; and, accord- ingly, we find, that they who swallow the food without due mas- tication, or waste the saliva by constant and profuse spitting, are more liable to attacks of dyspepsia, or imperfect digestion. It is proper, however, to add, that Dr. Budge/in extirpating the sali- vary glands in animals, did not find that they sustained the smallest apparent injury ; whence he conjectures, thatcertain glands can act as succedanea to others, and that in the removal of the salivary glands the pancreas perhaps supplies the fluid usually secreted by the other. The degree of resistance, and the sapidity of the food, apprise us when mastication and insalivation have been sufficiently exerted. When such is the case, it is subjected to the next of the digestive processes. Some physiologists have affirmed, that the uvula is the * Principles of Medicine, p. 354, Philad. 1832. b Nouvei Apcrcu sur la Physiologie du Foie, &c. Paris, 1833. c Versuch einer Physiologie des Blutes, Leipz 1820. < Lond. Lancet, 1841-2. e Mr. Ancell, Lond. Lancet, Dec. 17, 1842, p. 421. f Medicinische Zeitung, Mai 4, 1842 ; and British and Foreign Med. Rev. July. 1842, p. 221. DEGLUTITION. 523 organ which judges when the food is adapted for deglutition. Adelon, whose views are generally worthy of great favour and attention, asserts, " that it judges by its mode%f sensibility, of the degree in which the aliment has been prepared in the mouth ; of the extent to which it has been chewed, impregnated with saliva, and reduced to paste; and, according to the impression it receives from the aliment, it excites, sympathetically, the action of all those parts; directs the convulsive contraction of the muscles that raise the pharynx, and even keeps the stomach on the alert, and dis- poses it to receive favourably or to reject the food passing to it." Such a function would be anomalous. It is, indeed, impossible for us to conceive, how so insignificant an organ could be possessed of these elevated attributes. Observation, also, proves, that the notion is the offspring of fancy. Magendie* asserts, that he has known several persons, who had entirely lost the uvula, either by venereal ulceration or by excision, and yet he never remarked that their mastication experienced the slightest modification, or that they swallowed inopportunely. Our experience corresponds with that of Magendie. We know of more than one individual in whom there is not the slightest vestige of uvula, yet they taste, chew, and swallow like other persons. d. Deglutition. The act of swallowing,although executed with extreme rapidity, and apparently simple, is the most complicated of the digestive operations. It requires the action of the mouth, pharyhx, and oeso- phagus. It has been well analyzed by Magendie, — first of all in a thesis, maintained at the Ecole de Midline of Paris, in 1808, and subsequently, in his Pricis Elimentaire de Physiologie? To faci- litate its study, he divides it into three stages. In the first, the food passes from the mouth into the pharynx ; in the second, it clears the apertures of the glottis and nasal fossae, and attains the oesophagus ; and, in the third, it clears the oesophagus and enters the stomach. 1. When the food has been sufficiently masticated and imbued with saliva, it is collected by the action of the cheeks and tongue upon the upper surface of the last organ ; — the mass being more or less rounded, and hence usually termed the alimentary bolus. Mastication now stops; the tongue is raised and applied against the bony palate, in succession from the tip to the root, and the alimen- tary bolus, having no other way of escaping from the force press- ing it, is directed towards the pharynx. Previous to this, the pendulous veil of the palate had been applied to the base of the tongue. The bolus now raises it to the horizontal position : the circumflexus palati muscles render the velum tense, so that the food cannot pass into the nasal fossae; and the muscles that con- stitute the pillars of the fauces — the palato-pharyngei and the glosso-staphylini — contribute to this effect. By this combination » Op. cit. ii. 58. *> Edit. cit. ii. 63. 524 DIGESTION. of results, the food is impelled into the pharynx. The muscles, which, by their action, apply the tongue to the roof of the mouth and to the velum palati, are the proper muscles ofthe organ, aided by the mylo-hyoidei. In this first stage of deglutition, the motions are voluntary, except those of the velum palati. The process is not executed with rapidity and is easily intelligible. Such is not the case with the second stage. The actions in it are complicated, and executed with so much celerity, that they have been regarded as a kind of convulsion. 2. The distance, over which the bolus has to travel, in the second stage, is trivial : the rapidity of its course is owing to the larynx or superior aperture ofthe windpipe, which opens into the pharynx, having to be cleared instantaneously, otherwise respiration would be arrested, and the most serious effects ensue. The mode, in which this second stage is accomplished, is as follows. As soon as the alimentary bolus comes in contact with the pharynx, all is activity; the pharynx contracts, embraces, and presses the bolus ; and the velum pendulum, drawn down by the palato-pharyngei and glosso- staphylini muscles, fulfils a similar office. At the same time, the genio-glossus, by applying the tongue to the palate, from the tip to the root, raises the os hyoides, the larynx, and, with it, the anterior partes of the pharynx. The same effect is directly induced by the contraction ofthe mylo-hyoidei, and genio-hyoidei muscles; which, instead of acting as depressors of the lower jaw, as they do during mastication, take the jaw as their fixed point, and act as levators ofthe os hyoides. The larynx is thus elevated, carried forwards, and meets the bolus, to render its passage over the aperture of the larynx shorter, and, therefore, more speedy. To aid this effect, when we make great efforts to swallow, the head is inclined for- wards on the thorax. Whilst the os hyoides and the larynx are raised, they approach each other, — the upper margin ofthe thy- roid cartilage passing behind the body of the hyoid bone: the epiglottic gland is pushed backward, and the epiglottis is depressed, and inclined backwards and downwards, so as to cover the en- trance to the larynx. The cricoid cartilage executes a rotatory motion on the inferior cornua of the thyroid cartilage, which occa- sions the entrance ofthe larynx to become oblique, from above to below, and, of course, from before to behind. The bolus thus glides over its surface ; and, forced on by the veil of the palate, and by the constrictors of the pharynx, reaches the oesophagus. At one time, it was universally believed, that the epiglottis is the sole agent in preventing substances from passing into the larynx. The experiments of Magendie3 have, however, demon- strated, that this is the combined effect of the motions of the larynx just described, and of the muscles, whose office it is to close the glot- tis ; so that, if the laryngeal and recurrent nerves be divided in an a Memoire sur l'Usage de l'Epiglotte dans la Deglutition, Paris. 1813; and Precis, &c. i. 67. See, also, Sir A. Cooper, in Guy's Hospital Reports, i. 474, Lond. 1836 ; and Dr. J. Reid. in Edinb. Med. and Surg. Journ. p 50, for Jan. 1838. » DEGLUTITION. 525 animal, and the epiglottis be left in a state of integrity, deglutition is rendered extremely difficult;—the principal cause, that pre- vented the introduction of aliments into the glottis, having been removed by the section. Magendie, and Trousseau and Belloca refer to cases of individuals, who were totally devoid of epiglottis, and yet, who swallowed without any difficulty,11 and Magendie remarks, that if, in laryngeal phthisis, with destruction ofthe epi- glottis, deglutition be laboriously and imperfectly accomplished, it is owing to the carious condition of the arytenoid cartilages, and to the lips of the glottis being so much ulcerated as not to be able to close the glottis accurately. Whilst the bolus, then, is passing over the top ofthe larynx, respiration must be momentarily sus- pended, owing to the closure ofthe glottis; and if, owing to dis- traction of any kind, we attempt to speak, laugh, or breathe, at the moment of deglutition, the glottis opens, the food enters, and cough is excited, which is not appeased, until the cause is removed. This is what is called, in common language, •' the food going the wrong way." As soon as the bolus has cleared the glottis, the larynx descends, the epiglottis rises, and the glottis opens to give passage to the air. This is owing to the relaxation of the muscles that had previously raised the larynx and closed the glottis. Chaus- sier thinks, that the sterno-hyoidei muscles now act, and aid in producing the descent of the parts.0 The author had an excellent opportunity for noticing the laryngeal phenomena of deglutition in a man, who had cut his throat, and in whom a fistulous opening remained, which permitted the inferior ligaments of the larynx to be seen distinctly. The glottis^vas observed to be firmly closed.d M. Longet,e who has recently made experiments connected with this subject on animals, is disposed to think, that the displacement of the base of the tongue and the epiglottis are the two most important conditions, and that the closed glottis is only the last obstacle set up against the passage of food into the larynx ; but he evidently assigns too much importance to the epiglottis. The velum pendulum, then, protects the posterior nares and the orifices of the Eustachian tube from the entrance of the food ; and the epiglottis, the elevation of the larynx, with the contraction of the muscles that close the glottis, are the great agents in prevent- ing it from passing into the larynx. The whole of this second stage consists of rapid movements, of an entirely involuntary cha- racter, which, according to Bellingeri,f are under the presidency of the palatine filaments of the fifth pair. 3. In the third stage, the pharynx, by its contraction, forces the » A Practical Treatise on Laryngeal Phthisis, &c., &c.; Dr. Warder's translation, p. 84, in Dunglison's American Medical Library, Philad. 1839. See, also, on this subject, Horner, General Anatomy and Histology, ii. 149, Philad. 1843. b A similar case is given by Targioni, in which neither deglutition nor speech was impaired ; Morgagni, xxviii. 13. c Adelon, op. citat. ii. 424. d Dunglison's American Medical Intelligencer. Oct. 1841, p. 73. e L'Examinateur Medical, Oct. 17, 1841, and Brit, and For. Med. Rev. Jan. 1842, p. 228. 1 Dissert. Inaugural. Turin, 1823; noticed in Edinb. Med. and Surg. Journ. for July, 1834. 526 DIGESTION. alimentary bolus into the oesophagus, so as to somewhat dilate the upper part of the organ. The upper circular fibres are thus ex- cited to action, and force the food onward. In this way, by the successive contraction ofthe circular fibres, it reaches the stomach. In the upper part of the oesophagus, the relaxation of the circular fibres speedily follows their contraction ; but this is not the case in the lowest third, the circular fibres remaining contracted, for some time after the entrance of the bolus into the stomach, — probably to prevent its return into the oesophagus. The passage of the bolus along the oesophagus is by no means rapid. Magendiea affirms, that he was struck, in the prosecution of his experiments, with the slowness of its progression. At times, it was two or three minutes before reaching the stomach; at others, it stopped repeatedly, and for some time. Occasionally, it even ascended from the inferior extremity of the oesophagus towards the neck, and subsequently descended again. When any obstacle existed to its entrance into the stomach, this movement was repeated a number of times, be- fore the food was rejected. Every one, indeed, must have felt the slowness of the progression of the food through the oesophagus when a rather larger morsel than usual has been swallowed. If it stop, we are in the habit of aiding its progress by drinking some fluid, or by taking a piece of bread to drive it onwards. Occa- sionally, however, the probang is necessary to move it. The pain, produced in these cases, according to Magendie, is owing to the distension of the nervous filaments, that surround the pectoral por- tion of the canal. In the case of a female, labouring under a dis- ease, which permitted the interior of the stomach to be seen, Halle noticed, that whenever a portion of food passed into the stomach, a sort of ring or bourrelet was formed at the cardiac orifice, owing to the mucous membrane of the oesophagus being forced into the stomach, by the contraction ofthe circular fibres ofthe canal.b The mucous fluid from the different follicles, pressed out by the passage of the bolus, materially facilitates its progress. Notwithstanding the facility with which deglutition is accom- plished, almost every part of it is uninfluenced by volition; being dependent upon organization, and exerted instinctively. If the alimentary matter, contained in the mouth, be not sufficiently mas- ticated ; or if it have not the shape, consistence, and dimensions, that it ought to possess; or if the ordinary movements, that pre- cede mastication, have not been executed, — whatever effort we may make, deglutition is impracticable. We constantly meet with persons, who are unable to swallow the smallest pill; yet they can swallow a much larger mass, if certain preliminary motions be permitted, which, in the case of the pill, are inadmissible, in consequence of its being usually of a nauseous character. It appears, that the involuntary parts of the function are excited by the stimulation of the aliment; for, if we attempt to swallow the saliva several times in succession, we find that, after a time, the actis impracticable, owing to the deficiency of saliva. Every * Op. citat. ii. 69. b Ibij. jj. 7fJ# DEGLUTITION. 527 one must have experienced the difficulty of deglutition, when the mouth and fauces were not duly moistened by their secretions. The whole ofthe involuntary part of deglutition is probably un- der the control of the reflex system of nerves; an impression being made by the alimentary matters upon the excitor or afferent nerves, which impression is conveyed to the gray matter of the spinal cord, and in the invertebrata to ganglia corresponding with it; whence it is reflected to the muscular fibres that have to be thrown into contraction. The portion of the spinal cord, which serves as a centre for the reception of the impression, and the point of depar- ture for the motor influence is the medulla oblongata ; and the ex- periments of Dr. John Reid,a lead to the inference, that the glosso- pharyngeal, which is chiefly distributed to the mucous surface of the tongue and fauces, is the excitor nerve; the pharyngeal branches ofthe pneumogastric, the motors. It would seem, how- ever, that these nerves do not alone possess the function ; for after they have been divided, the animal is still capable of imperfect deglutition. The associate excitor or afferent nerves, Dr. Reid concludes to be — the branches of the fifth pair, that are distributed upon the fauces, and probably also the branches of the superior laryngeal distributed upon the pharynx : — the associate motor or efferent nerves being the branches ofthe hypoglossal, that are distri- buted to the muscles of the tongue, and to the sterno-hyoid, sterno- thyroid, and thyro-hyoid muscles ; the filaments of the inferior laryn- geal that ramify on the larynx : some ofthe branches of the fifth pair that supply the levator muscles of the lower jaw; the branches of the portio dura that ramify upon the digastric and stylo-hyoid muscles, and upon the muscles ofthe lower part of the face ; and probably some of the branches of the cervical plexus, which unite themselves to the descendens noni.b It must be admitted, however, that this part of the physiology of deglutition is obscure. Some individuals are capable of swallowing air; and, according to Magendie,0 it is an art that can be attained by a little practice. In the stomach, the air acquires the temperature of the viscus, be- comes rarefied, and distends the organ; exciting, in some, a feeling of burning heat ; in others, an inclination to vomit, or acute pain. Magendie thinks it probable, that its chemical composition under- goes change ; but, on this point, nothing certain is known. The time of its stay in the stomach is variable. Commonly, it ascends into the oesophagus, and makes its exit through the mouth or nos- trils. At other times, it passes through the pylorus, and spreads through the whole of the intestinal canal, as far as the anus, dis- tending the abdominal cavity, and simulating tympanites. Ma- gendie refers to the case of a young conscript, who feigned the disease in this manner. e. Chymification. When the food has experienced the changes, impressed upon it 1 Edinb. Med. and Surg. Journ. vol. xlix. k Carpenter, Human Physiology, p. 145, Lond. 1842. « Ibid. ii. 146. 528 DIGESTION. by the preceding process, it reaches the cavity of the stomach, where it is retained for several hours, and undergoes the first por- tion of the true digestive action ; being converted into a pultaceous mass, to which the term chyme has been applied; whilst the pro- cess has been called chymification. It does not seem, that all physiologists have employed these terms in this signification ; some have confounded the chyle with the chyme ; and chylification with chymification. The former of these processes is distinctly a duo- denal act: the latter is exclusively gastric. The aliment, as it is sent down by repeated efforts of deglutition descends into the splenic portion of the stomach; and this without difficulty, as regards the first mouthfuls. The stomach is but little compressed by the surrounding viscera; and its parietes readily separate to receive the alimentary bolus ; but when food is taken in considerable quantity, the distension becomes gradually more difficult, owing to the compression of the viscera and the disten- sion of the parietes of the abdomen. The accumulation takes place chiefly in the splenic and middle portions. Dr. Beaumont3 observed, that when a portion of food was received into the sto- mach, the rugae of the latter gently close upon it, and, if it be suf- ficiently fluid, they gradually diffuse it through the cavity of the organ, entirely excluding more during this action. The contraction ceasing, another quantity of food is received in the same manner. It was found, in the subject of his experiments, that when the val- vular portion of the stomach, situate at the fistulous aperture was depressed, and solid food introduced, either in larger pieces or finely divided, the same gentle contraction or grasping motion took place, and continued for fifty or eighty seconds, and would not allow of another quantity, until that period had elapsed, when the valve could be depressed, and more food put in. When the man was so placed, that the cardia could be seen, and was then per- mitted to swallow a mouthful of food, the same contraction ofthe stomach and grasping of the bolus were invariably observed to commence at the oesophageal ring. Hence, when food is swal- lowed too rapidly, irregular contractions of the muscular fibres of the oesophagus and stomach are produced, the vermicular motions of the rugae are disturbed, and the regular process of digestion is interrupted. Whilst the stomach is undergoing this distension by the food, it experiences changes in its size, situation, and connexion with the neighbouring organs. The dilatation does not affect its three coats equally. The two laminae of the peritoneal coat separate, and per- mit the stomach to pass farther between them. The muscular mem- brane experiences a true distension; its fibres lengthen, but still so as to preserve the particular shape of the organ ; whilst the mucous coat yields, in those parts especially where the rugae are numerous; that is, along the great curvature and in the splenic portion. In place, too, of being flattened at its anterior and posterior surfaces, * Experiments, &c. on the Gastric Juice, p. 110. CHYMIFICATION. 529 and occupying only the epigastrium, and a part of the left hypo- chondrium, it assumes a rounded appearance. Its great cul-de-sac descends into the left hypochondre and almost fills it, and the greater curvature descends towards the umbilicus, especially on the left side. The pylorus preserves its position, and its connexion with the surrounding parts;— being fixed down by a fold of the peritoneum. It is chiefly forwards, upwards, and to the left'side, that the dilatation occurs. The posterior surface cannot dilate on account of the resistance of the vertebral column, and of a liga- mentous formation which prevents the stomach from pressing on the great vessels behind it. Its cardiac and pyloric portions are also fixed; so that when it is undergoing distension, a movement of rotation takes place, by which the great curvature is directed slightly forwards; the posterior surface inclined downwards, and the superior upwards. A wound, consequently, received in the epigastric region, will penetrate the stomach in a very different part, according as the viscus may be, at the time, full or empty. The dilatation of the stomach produces changes in the condition of the abdomen and its viscera. The total size of the cavity is augmented : the belly becomes prominent; and the abdominal vis- cera are compressed, — sometimes so much so as to excite a desire to evacuate the contents of the bladder or rectum. The diaphragm too, is 'crowded towards the thorax; and is depressed with diffi- culty : so that, not only is ordinary respiration cramped, but speak- ing and singing become laborious. When the distension of the organ is pushed to an enormous extent, the parietes of the abdomen may be painfully distended, and the respiration really difficult. It is in these cases of over-distension, that an energetic contraction of the oesophagus is necessary; hence the advantage of the strong muscular arrangement at its lower portion. In proportion as the food accumulates in the stomach, the sensa- tion of hunger diminishes ; and, if we still go on swallowing ad- ditional portions, it entirely disappears, or is succeeded by nausea and loathing. The quantity, necessary to produce this effect, varies according to the individual, as well as to the character of the food; a very luscious article sooner cloying than one that is less so. A due supply of liquid with our solid aliment also §nables us to prolong the repast with satisfaction. As the stomach, when distended, presses upon the different vis- cera and upon the abdominal parietes, it is obvious, that it must experience a proportionate reaction. An interesting question con- sequently arises ; — to determine the causes, which oppose the passage of the food back along the oesophagus, as well as through the pylorus. Magendiea found, in his vivisections, that the lower portion of the oesophagus experiences, continuously, an alternate motion of contraction and relaxation. This contraction begins at the junction of the two upper thirds with the lowest third; and is » Precis, &c. ii. 82. VOL. I. — 45 530 DIGESTION. propagated, with some rapidity, to the termination of the oeso- phagus in the stomach. Its duration, when once excited, is varia- ble ;— the average being, at least, half a minute. When thus contracted, it is hard and elastic, like a cord strongly stretched. The relaxation, which succeeds the contraction, occurs suddenly and simultaneously in all the contracted fibres; at times, however, it appears to take place from the upper fibres towards the lower. In the state of relaxation, the oesophagus is remarkably flaccid; — forming a singular contrast with that of contraction. This move- ment ofthe oesophagus is, according to Magendie,3 under the de- pendence of the eighth pair of nerves. When these nerves were divided in an animal, the oesophagus no longer contracted. Still it was not relaxed Its fibres, thus deprived of nervous influence, were shortened with a certain degree of force; and the canal re- mained in a state intermediate between contraction and relaxation. The lower part of the oesophagus of the horse, for an extent of eight or ten inches, is not contractile in the manner of muscles. Magendieb found, that when the eighth pair of nerves was irri- tated ; or when the parts were exposed to the galvanic stimulus, no contraction was produced. The oesophagus of this animal is, however, highly elastic; and its lower extremity is kept so strongly closed, that for a long time after death, it is difficult to inyoduce the finger into it; and considerable pressure is required to force air into it. This arrangement Magendie considers to be the true reason, why horses vomit with such difficulty as occasionally to rupture the stomach by their efforts. The alternate motion of the oesophagus, which we have described, opposes the return of the food from the stomach. The more the stomach is distended, the more intense and prolonged is the contraction, and the shorter the relaxation. The contraction, too, commonly coincides with in- spiration ; the time at which the stomach is, of course, most strongly compressed. The relaxation is synchronous with expiration. The pylorus prevents the alimentary mass from passing into the duodenum. In living animals, whether the stomach be filled or empty, this aperture is constantly closed by the constriction of its fibrous ring, and the contraction of its circular fibres ; and, so accu- rately is it closed, that, if air be forced into the stomach from the oesophagus, the organ must be distended, and considerable exer- tion made to overcome the resistance of the pylorus. Yet, if air be forced from the small intestine in the direction of the stomach, the pylorus offers no resistance; suffering it to enter the organ under the slightest pressure ;—a circumstance that accounts for the facility with which the bile enters the stomach ; especially when there exists any unusual inverted action of the duodenum. To the pylorus, however, a more active part has been assigned in the passage of the chyme from the stomach into the intestine. (i Nothing in the animal economy," says Dr. South wood Smith,0" is » Ibid. ii. 18. b ibid. ii. 19. c Animal Physiology, Library of Useful Knowledge, p. 41. CHYMIFICATION. 531 more curious and wonderful than the action of that class of organs of which the pylorus affords a remarkable example. If a portion of undigested food present itself at this door of the stomach, it is not only not permitted to pass, but the door is closed against it with additional firmness : or, in other words, the muscular fibres of the pylorus, instead of relaxing, contract with more than ordi- nary force. In certain cases, where the digestion is morbidly slow, or where very indigestible food has been taken, the mass is carried to the pylorus before it has been duly acted upon by the gastric juice : then, instead of inducing the pylorus to relax, in order to allow of its transmission to the duodenum, it causes it to contract with so much violence as to produce pain, while the food, thus re- tained in the stomach longer than natural, disorders the organ: and if the digestion cannot ultimately be performed, that disorder goes on increasing until vomiting is excited, by which means the load that oppressed it is expelled. The pylorus is a guardian placed between the first and the second stomach, in order to prevent any substance from passing from the former until it is in a condition to be acted upon by the latter : and so faithfully does this guardian perform its office, that it will often, as we have seen, force the stomach to re- ject the offending matter by vomiting rather than allow it to pass in an unfit state: whereas, when chyme, duly prepared, presents itself, it readily opens a passage for it into the duodenum." This view of the functions of the pylorus has antiquity in its favour. It is, indeed, as old as the name, which was given to it, in conse- quence of its being believed to be a faithful porter or janitor, (irv\a>p<>c, " a porter :") but it is doubtless largely hypothetical. We constantly see substances traverse the whole extent of the intestinal canal, without having experienced the slightest modification in the stomach ; yet the pylorus allows them free passage. Buttons, half- pence, &c, have made their way through, without difficulty; as well as the tubes and globes, employed in the experiments of "Spal- lanzani, Stevens, and others. There are certain parts of fruits, which are never digested, yet the janitor is always accommodating. Castor oil is capable of being wholly converted into chyle; and would be so, if it could be retained in the stomach ; yet there is no agent, which arrests its onward progress. Still, from these, and other circumstances, Broussaisa has inferred, that there is an in- ternal gastric sense, which exerts an elective agency; detaining, as a general rule, substances that are nutritive, but suffering others to pass. The presence of food in the stomach, after a meal, soon excites the organ to action, although no change in the food is perceptible for some time. The mucous membrane becomes more florid, in consequence of the larger afflux of blood; and the different secre- tions appear to take place in greater abundance; become mixed with the food, and exert an active and important part in the » Traite de Physiol, appliquee a la Pathologie ; translated by Drs. Bell and La Roche, p. 314, Philad. 1832. 532 DIGESTION. changes which it experiences in the stomach. Direct experiment has proved, that such augmented secretion actually occurs. If an animal be kept fasting for some time, and then be made to swallow dry food, or even stones, and be deprived of liquid aliment, the substances, swallowed, will be found,—on killing it sometime afterwards, — surrounded by a considerable quantity of fluid. Such is not the case with animals, killed after fasting. The stomach then contains no fluid matter. The augmented secretion, in the former case, must, therefore, be owing to the presence of dry food in the stomach. That it is not simply the fluid, passed down by deglutition, — the salivary and mucous secretions, for example,— is proved by the fact, that the same thing occurs when the oesopha- gus has been tied. Besides, if the stomach of a living animal be opened, and any stimulating substance be applied to its inner sur- face, a secretion is seen to issue, in considerable quantity, at the points of contact; and, again, if an animal be made to swallow small pieces of sponge, — attached to a thread hanging out ofthe mouth, by means of which they can be withdrawn, — the sponge becomes filled with the fluids secreted by the stomach, and, on withdrawing it, a sufficient quantity can be obtained for analysis. Such experiments have been repeatedly performed by MM. Reau- mur,8 Spallanzani,b and others. In Dr. Beaumont's0 case, the col- lection of gastric secretion was obtained by inserting an elastic gum tube through the opening ; in a short time fluid enough was secreted to flow through the tube. This admixture with the fluids of the mucous membrane of the stomach, and the secretions continually sent down from the mouth, by the efforts of deglutition, is the only apparent change witnessed for some time after the reception of solid food. Sooner or later, according to circumstances, the pyloric portion of the organ contracts; sending into the splenic portion the food it contains : to the contraction dilatation succeeds; and this alternation of movements goes on during the whole of diges- tion. After this time, chyme only is found in the pyloric portion, mixed with a very small quantity of unaltered food. This motion of contraction and relaxation has been called peristole; and it ap- pears, at first, to be limited to the pyloric portion ofthe organ, but it gradually extends to the body and splenic portion, so that, ulti- mately, the whole stomach participates in it. It consists in an al- ternate contraction and relaxation of the circular fibres of the sto- mach ; and the gentle oscillation, thus produced, not only facilitates the admixture of the food with the gastric secretions, but exposes fresh portions continually to their action. The experiments of Bichat satisfied him, that the peristole is more marked, the greater the fulness of the stomach. He made dogs swallow forced-meat balls, in the centre of which he placed cartilage, and he found, that when the stomach was greatly charged, the cartilages were pressed out of the balls. This did not happen, when the organ contained a smaller quantity of food. a Memoir, de 1'Acad. pour 1752. b Exper. sur la Digestion, Genev, 1783. c Experiments, &c. on the Gastric Juice, p. 106. CHYMIFICATION. 5 33 The ordinary course and direction of the revolutions of the food, according to Dr. Beaumont,a are as follows : — The bolus, as it enters the cardia, turns to the left, passes the aperture, descends into the splenic extremity, and follows the great curvature towards the pyloric end. It then returns in the course of the lesser curva- ture, and makes its appearance again at the aperture, in its descent into the great curvature to perform similar revolutions. That these are the revolutions of the contents of the stomach, he ascertained by identifying particular portions of food, and by the fact, that when the bulb of the thermometer was introduced during chymification, the stem invariably indicated the same movements. Each revolu- tion is completed in from one to three minutes, and the motions are slower at first, than when chymification has made considerable progress. In addition to these movements, the stomach is sub- jected to more or less succussion from the neighbouring organs. At eajfr inspiration, it is pressed' upon by the diaphragm; and the large arterial trunks in its vicinity, as well as the arteries, distri- buted over it, subject it to constant agitation. We have already remarked, that the peristaltic movement of the stomach, —and it extends likewise to the intestines, — is effected by the muscular coat of the organ. It is, however, an involuntary contraction, and appears to be little influenced by the nervous system ; continuing, for instance, after the division of the eighth pair of nerves ; becoming more active, according to Magendie,bas animals are more debilitated, and even at death; and persisting after the alimentary canal has been removed from the body. MM. Tiedemann and Gmelin,0 however, affirm, that by irritating the plexus of the eighth pair of nerves, which is situate around the oeso- phagus, with the point of a scalpel, or touching it with alcohol, the peristaltic action of both stomach and intestines can be constantly excited, and both Valentin and Dr. John Reid state, that distinct movements may be excited in the stomach by irritating the pneu- mogastric.*1 This involuntary function, as well as that exerted by the heart and other involuntary organs, affords us a striking instance of the little nervous influence, that seems to be requisite for carrying on many of those functions which have to be executed, independently of volition, through the whole course of existence ; and which ap- pear to be excited at times, in a reflex manner, by the presence of appropriate excitants; — of food, in the case of the peristaltic action ofthe stomach; of blood, in that of the heart, &c.; and yet may be carried on — as we have seen — even in the absence of all nervous influence ; as in the cases of the intestinal canal, and the heart, which may contract for a long time after they have been removed from the body. In the case of the intestinal canal, the movements are doubtless influenced by the spinal cord, probably > Op. citat. p. 110. b Precis, Elementaire, ii. 20. • Recherches sur la Digestion, Paris, 1827. * Carpenter, Human Physiology, p. 148, Lond. 1842. 45* 534 DIGESTION. through the sympathetic, by means of the fibres, which-the canal derives from it; but although influenced by the spinal cord, the digestive tube from the stomach to the rectum is not dependent upon it for its contractility. As Dr. Carpenter has remarked, it is enabled to propel its contents by its own inherent powers; but, as in other instances, the nervous centres exert a general control over even the organic functions, " doubtless for the purpose of harmo- nizing them with each other, and with the conditions of the organs of animal life."a The gentle, oscillatory or vermicular motion of the stomach, and the admixture with the fluids, secreted by its internal membrane, as well as by the different follicles, &c. in the supra-diaphragmatic portion of the alimentary canal, are probably the main agents in the digestion operated in the stomach. Much contrariety of sentiment has existed regarding the precise organs, that secrete the fluid, which oozes out as soon as ^§>od is placed in contact with the mucous coat of the stomach. Whilst some believe it to be exhaled from that membrane ; others conceive it to be secreted by the numerous follicles, seated in the membrane as well as in that of the lower portion of the oesophagus ; or by what have been termed the gastric glands. The analogy of many animals, especially of birds, would render the last opinion the most probable. In them we find, in the second stomach, the cardiac or gastric glands largely developed ; and it is probable, that they are the great agents of the secretion of the digestive fluid. (See Fig. 127.) MM. Tiedemann and Gemlinb affirm, that the more liquid portion ofthe gastric fluid is exhaled, and that the thicker, more ropy and mucous portion is secreted by the follicles. Rudolphi0 assigns them a double origin ;— from both the exhalants, and the gastric glands or follicles; whilst Leuret and Lassaigned ascribe their for- mation exclusively to the villi. Dr. Beaumont,6 who had an ex- cellent opportunity for experimenting on this matter, remarks, that on applying aliment or any irritant, to the internal coat of the sto- mach, and observing the effect through a magnifying glass, innu- merable, minute, lucid points, and very fine papillae, could be seen protruding, from which a pure, limpid, colourless, slightly viscid fluid distilled, which was invariably and distinctly acid. On ap- plying the tongue to the mucous coat in its empty, unirritated state, no acid taste could be perceived. Although no apertures were perceptible in the papillae, even with the assistance of the best microscope that could be obtained, the points, whence the fluid issued, were clearly indicated by the gradual appearance of innu- merable, very fine, lucid specks, rising through the transparent mucous coat, and seeming to burst, and discharge themselves upon the very points of the papillae, diffusing a limpid, thin fluid over the whole interior gastric surface. 1 Ibid. p. 151. b Op. citat. c Grundriss der Physiologie, Berlin, 1821. 11 Recherches sur la Digestion, Paris, 1825. « Op. citat, 103. CHYMIFICATION. 535 A like difference of opinion has prevailed regarding the chemical character of the fluids ; and this has partly arisen from the difficulty of obtaining them identical. The true fluid, secreted by the gastric follicles or mucous membrane, can never, of course, be obtained for examination in a state of purity. It must always be mixed, not only with the other secretions of the stomach, but with all those sent down into the organ, by the constant efforts of deglutition. It is, consequently, to this mixed fluid, that the term gastric juice has really been applied; although it is more especially appro- priated to the particular fluid, presumed to be secreted by the stomach, and to be the great agent in digestion. To the nature of the gastric juice and its effect in the process of digestion, we shall have occasion to recur presently. It is probably owing to the quantity of fluid, secreted by the stomach, that it is so largely supplied with bloodvessels; and that the mucous membrane is more injected, during the presence of food in the organ. Experiments, by Sir Benjamin Brodiea and others, would seem to show, that this secretion is under the influ- ence of the eighth pair of nerves. Having administered arsenic to different animals, — in some of which he had divided these nerves, — he found, that, whilst the stomachs of those, in which the nerves were unaffected, contained a large quantity of a thin, mucous fluid ; in those, whose nerves were divided, the organ was inflamed and entirely dry. Leuret, and Lassaigne,1' however, affirm, that the division of the nerves had no influence on the gastric secretion. But more of this presently. Before entering into the views of different physiologists on chy- mification, — in other words, on the theories of digestion, it will be well to refer to the physical and chemical properties of the chyme. Whether the changes, induced upon the food, be simply physical or chemical, or whether the first stage of animalization be effected within the stomach, will be a topic for future inquiry. Chyme is a soft, homogeneous substance, of a grayish colour and acid taste. Such are its most common characters: it varies, how- ever, according to the food that has been taken, as may be easily observed, by feeding animals on different simple alimentary sub- stances, and killing them during the process of digestion. This difference in its properties accounts for the discrepancy observable in the accounts of writers on the subject. The change, wrought on the aliments, is, doubtless, of a chemical nature ; but the new play of affinities is controlled by circumstances inappreciable to us. In the case of a female patient at the hospital La Charite, of Paris, who had been gored by a bull, and had a fistulous opening in the stomach, the food, during its conversion into chyme, appeared to have acquired an increase of its gelatin ; a greater proportion of chloride of sodium, and phosphate of soda and phosphate of lime, and a substance, in appearance, fibrinous.0 » Philos. Trans, for 1814. b Op. citat. c Richerand's Nouveaux Elemens de Physiologie, edit. 13eme, par Berard, aine, p. 72, Bruxelles, 1837. 536 DIGESTION. It has been said, again, that the food becomes decarbonized and more azoted ; that the carbon, which disappears, is removed by the oxygen ofthe air swallowed with the food, or by that contained in the food itself; and that the azote proceeds, in greater quantity, from the secretions of the stomach, or predominates, simply because the food is decarbonized. Adelon* has properly remarked, that the fact and the explanation are here equally hypothetical. Gene- rally, the chyme possesses acid properties, MM. de Montegre,b and Magendie,0 and Tiedemann and Gmelin,d always observed it to be so. Haller6 and Marcet found it to be neither acid nor alkaline. In the chyme, examined by the latter gentleman, he detected albu- men, an animal matter, and some salts, differing, however, slightly, according as it proceeded from animal or from vegetable food. In the latter case, for example, it afforded four times as much carbon as in the former, but less saline matter ; and this consisted of lime and an alkaline chloride. MM. Leuret and Lassaignef analyzed the chyme from the stomach of an epileptic, who died suddenly in a fit, five or six hours after having eaten. The chyme was of a white, slightly yellowish colour, and of a strong, disagreeable taste. On analysis, it afforded a free acid, — the lactic; a white, crystalline, slightly saccharine matter, analogous to the sugar of milk ; albumen, soluble, in water ; a yellowish, fatty, acid matter, analogous to rancid butter ; an animal matter, soluble in water, having all the properties of casein ; and a little chloride of sodium, phosphate of soda, and much phosphate of lime. Lastly, Proute affirms, that a quantity of chlorohydric acid is present in the stomach, during the process of digestion. He detected it in the stomachs of the rabbit, hare, horse, calf, and dog, and in the sour matter ejected from the stomachs of persons labouring under indigestion : __a fact which has since been confirmed by Mr. Children. MM. Tiedemann and Gmelin, and Dr. Beaumont,h affirm, that the se- cretion of acid commences, as soon as the stomach receives the sti- mulus of a foreign body, and that it consists of the chlorohydric and acetic acids. The experiments of these gentlemen were not con- fined to the chymous mass, obtained from digestible food. They examined the fluids, secreted by the mucous membrane, when in- digestible substances were sent into the stomach, and the acid character was equally manifested. These experiments, conse- quently, remove an objection, made by Bostock,1 regarding the de- tection ofthe chlorohydric acid by Prout; — that, as there did not appear to be any evidence of the existence of this acid, before the introduction of food into the stomach, it might rather be inferred, that it is, in some way or other, developed during the process of » Physiol, de l'Homme, &c, edit. cit. torn. ii. b Experiences sur la Digestion, Paris, 1824. e Op. citat. ii. p. 87. <* Recherches, &c, sur la Digestion, Paris, 1827. " Element. Physiol. lix. 1. f Recherches, &c. p. 114. s Philos. Trans, for 1824; and Bridgewater Treatise, on Chemistry, &c, Amer. Edit. p. 268, Philad. 1834. k On the Gastric Juice, &c, p. 105. » Physiology, 3d edit. p. 569, Lond. 1836. CHYMIFICATION. 537 digestion. In all Dr. Beaumont's experiments, the chyme, as before observed, was, invariably, distinctly acid. The principal theories on chymification have been the follow- ing:— 1. Coction,ox elixation. — This originated with Hippocrates, and was vaguely used by him to signify the maceration and matu- ration from the raw state, experienced by the food in the stomach, The doctrine was embraced by Galen and others, who ascribed to the organ, an attracting retaining, concocting and expelling quality effected by heat.a In proof of this, they affirmed, that the heat of the stomach is increased during chymification; that the process is more rapid in the warm, than in the cold-blooded animal; that it is aided by artificial heat, and continues even after death, if care be taken to keep up the heat of the body; that in the ex- periments on artificial digestion made by Spallanzani, heat was always necessary, and the greater the degree of heat the more easy and complete the digestion. It is hardly necessary, however, to say that the heat ofthe stomach is totally insufficient to excite any coction or ebullition, in the physical sense of the term, and this applies, particularly, to the cold-blooded animal, which must digest, if not with the same, with due, rapidity. 2. Putrefaction. — The next great hypothesis was that ofputre- faction, which, we are informed by Celsus,b was embraced by Plistonicus, a disciple of Praxagoras of Cos, who flourished upwards of three hundred years before the birth of Christ. Of late it has had no advocates, but it appears to have been the view embraced by Cheselden.0 The reasons, urged in favour of it, have been ; — the putrescible character of the materials employed as food; the favourable circumstances of a heat of 98° or 100°, and of moisture ; and, by some, the foetor of the excrements. The objections are, 1. That when the contents of the stomach are rejected, during chymification, they exhibit no evidence of putridity. 2. That in all the experiments, which have been made on the comparative digestibility of different substances, where it has been necessary to kill the animals, at different stages of the digestive process, there has not been the slightest sign of putrefaction. 3. That opportu- nities frequently occur, for witnessing ravenous fishes and reptiles with an animal or part of an animal,— which has been too large to be entirely swallowed, — partly in the stomach and the remain- der in the gullet and mouth. This we have seen, more than once, in pikes that have been choked by attempting to swallow trouts larger than themselves. In all these cases, where the food has re- mained in this situation some days, the part of it, contained in the throat, has been found putrid, whilst that in the stomach has been en- tirely sweet; and, lastly, in Spallanzani's and other experiments, to be detailed presently it was found, that, when food, in a state of pu- » Boerhaav. Pralectiones Academ. Not. Adv. § 86, torn, i., Gotting. 1740-1743, b De Medicina, cura, E. Milligan, edit. 2da p. 5, Edinb. 1831. c Anatomy ofthe Human Body, &c, 8th edit, p. 155, Lond, 1763, 538 CHYMIFICATION. tridity, was taken into the stomach, or mixed with the gastric juice out of the stomach, it recovered its sweetness. It has been already observed, that it is the custom in some countries, to eat the gibier or game in a state of incipient putrefaction ; yet the breath is not in any way tainted by it. Trituration.— The mathematical physiologists,—Borelli.* Hec- quet,b Megallotti,c Pitcairne,d and others—after the example of Erisistratus,e attempted to refer the whole process of digestion to trituration, imagining, that the food is subjected, in the stomach, to an action, similar to that of the pestle and mortar of the apothe- cary, or of the millstone, and that the chyle is formed like an emulsion. The most plausible arguments, in favour of this view ofthe subject, are drawn from the presumed analogy ofthe grani- vorous bird, whose stomach is capable of exerting an astonishing degree of pressure on substances submitted to its power. There is no analogy, however, between the human stomach, and the gizzard of birds. The latter is a masticatory organ, and therefore possessed of the surprising powers which we have elsewhere de- scribed ; whilst mastication, in man, is accomplished by distinct organs. No comparison can, indeed, be instituted between the gentle oscillatory motion of the stomach, and the forcible compres- sion, exerted by the digastric muscle of the gizzard. The simple introduction of the finger, through a wound of the abdomen, has shown, that the compression, exerted by it on its contents, is totally insufficient to bruise any resisting substance. Moreover, we con- stantly see fruits, — as raisins and currants, — passing through the whole intestinal canal unchanged; whilst worms remain in the stomach, — reside there — unhurt; and, we shall see presently, that the experiments of Reaumur and Spallanzani proved most convincingly, that digestion is effected independently of all pres- sure. The futility, indeed, of this mode of viewing the subject, is signally illustrated by the fact, that, whilst Pitcaime estimated the power of the muscular fibres of the stomach at 12,951 pounds, Hales/ thought that twenty pounds would come nearer the truth ; and Astrucs valued its compressive force at five ounces. 4. Fermentation. — The system of fermentation had many partisans; amongst whom may be mentioned Van Helmont,h Sylvius,1 Willis,-" Boyle,k Grew,1 Charleton,m Lower," Raspail,0 &c. Digestion in this view, was ascribed to the chemical reaction of * De Motu Animalium ; Addit. J. Bernouillii, M.D. Medit. Mathem. Muscul. Lugd. Bat. 1710. b Traite' de la Digestion, Paris, 1710. c Haller. Elem. Physiol, xix. 5. a Works, &c. Lond. 1715. e Cels. loc. citat. f Statical Essays, ii. 174, 4th edit. Lond. 1769. s Traite de la Cause de la Digestion, &c. Toulouse, 1714 ; and Haller. Loc citat. ■» Ortus Medicinse, &c. Amstel. 1648. * Opera. Genev. 1781. j Diatribae duae Medico-Philosophicae, &c. Lond. 1659. * Works, vol. ii. Lond. 1772. 1 Comp. Anat of the Stomach, &c. Lond. 1681. " CEcon. Anim. Exerc. 2. n Tractatus de Corde, &c. Amstel. 1671. 0 Chimie Organique, p. 356, Paris, 1833. CHYMIFICATION. 539 the elements ofthe food upon each other, during their stay in the stomach ; — the action being excited by some of the food which had already undergone digestion, or by a leaven, secreted for the purpose by the stomach itself. In favour of this view, it was at- tempted to show, that air is constantly generated in the stomach, and that an acid is always produced as the result of fermentation ; the formation of chyme being assigned, by the greater number of physiologists, to the vinous and acetous fermentations. The ob- jections to the doctrine of fermentation are ; that digestion ought to be totally independent of the stomach, except as regards tempe- rature ; and that the food ought to be converted into chyme, ex- actly in the same manner,—if it were reduced to the same con- sistence, and placed in the same temperature, — out of the body; which is not found to be the case. Bones are speedily reduced to chyme in the stomach ofthe dog, although they would remain un- changed for weeks, in the same temperature, out of the body. The facts of the voracious fishes before mentioned likewise prove the insufficiency of this hypothesis; according to which, digestion ought to be accomplished as effectually in the oesophagus as in the sto- mach. Yet it is found, in these cases, that, whilst the portion in the stomach is digested, the other may be unaltered, or it may be putrid. The truth is; — in healthy digestion, fermentation, in the ordinary acceptation ofthe term,does not occur; and, whenever the elements ofthe food react upon each other, it is an evidence of im- perfect digestion; hence, fermentation is one of the most common signs of dyspepsia. 5. Chemical solution.—The theory of chemical solution, as pro- posed by Spallanzani,a has met with more favour from physiolo- gists than any of the others that have been mentioned, and may, we think, be regarded as completely established. According to him, chymification is owing to the solvent action of a fluid, secreted by the stomach, which accumulates in that viscus between meals and during hunger,b and acts as a true menstruum on the substances exposed to it. This fluid, — to which he gave the name gastric juice, — he affirmed to be peculiar in each animal, accord- ing to its kind of alimentation, —a fact confirmed by the experi- ments of Voisin, — corresponding, as regards its energy, with the rest of the digestive apparatus, and differing in its source in the series of animals; proceeding, in some, from the follicles of the oesophagus; in others from those of the stomach itself; but always identical in the same animal; generally transparent, slightly yellow, of a saline taste, bitter, slightly volatile, and stronger in animals with a membranous than in those with a muscular sto- mach, and than in ruminant animals. To obtain the juice, Spallanzani opened animals, after they had * Experiences sur la Digestion, par Senebier, Gdnev. 1783. b It has been already stated, that the experiments of Dr. Beaumont have satisfac- torily proved that no such accumulation takes place during hunger. 540 DIGESTION. been made to fast for some time ; and collected the juice, accumu- lated in their stomachs ; or he made them swallow tubes, pierced with holes, and filled with small sponges. By withdrawing these tubes, by means of a thread attached to them, and suffered to hang out of the mouth, and expressing the sponges, he obtained the fluid, in quantity sufficient for examination. To determine whether this fluid, obtained from the stomach of fasting animals, was destined to chymify the food, Spallanzani tried the following expe- riments. He caused numerous animals to swallow tubes filled with food, but pierced with holes, so that the juices of the stomach might be able to get into their interior; and he found that chymi- fication was effected, when he had taken the precaution to chew the substances before they were put into the tubes, or to triturate them ; and the process was always more readily accomplished, the more easy the access of the fluids. On repeating these experi- ments on animals of various kinds, with a muscular or membranous, or musculo-membranous stomach; on pullets, turkeys, ducks, pigeons, rooks, frogs, salamanders, eels, serpents, sheep, cats, &c, he always obtained the same results ; and hence he affirmed, that trituration cannot be the essence of chymification ; and that it does not exist in animals with a membranous stomach. Reaumur,3 — originally a believer in the doctrine of trituration,—had previously proved this fact by experiments of a similar kind. Spallanzani next repeated those experiments upon himself. Having well chewed different articles of food, he inclosed them in wooden tubes pierced with holes, and swallowed them ; but, as these tubes excited pain in the bowels, he substituted small bags of linen. The substances contained in the interior of the bags were digested, without the bags being torn; a fact, which proved that digestion must have been accomplished by means of a fluid, which pene- trated them. In 1777, Stevensb repeated these experiments. He made an individual swallow balls of metal, filled with masticated food, and pierced with holes: when these balls were voided,— thirty-six or forty-eight hours afterwards,—they were entirely empty. Lastly. — Spallanzani was desirous of seeing whether this solvent juice could effect digestion out of the body. He put some well masticated food in small glass tubes, and mixed gastric juice with it. These tubes he placed in his axilla, in order that they might be exposed to the same degree of heat as in the sto- mach ; and he affirms, that in the space of fifteen hours, or of two days, —more or less, —the substances appeared to be converted into chyme. In these experiments he found it important to employ gastric juice, which had not previously been used, and to have a sufficient quantity of it. From all these experiments, Spallanzani conceived it to be de- monstrated, that chymification is a true chemical solution ; and he endeavoured to deduce from them the degree of digestibility of different substances. Similar experiments were instituted by Dr. * Memoir, de l'Acad. pour 1752. b De Alimentorum Concoctione, § 24. CHYMIFICATION. 541 Beaumont.a In all cases, solution occurred as perfectly in the artificial as in the real digestions, but they were longer in being accomplished, for reasons, which appear sufficient to explain the difference. In the former, the gastric secretion is not continuous ; the temperature cannot be as accurately maintained, and there is an absence of those gentle motions ofthe stomach, which are mani- festly so useful in accomplishing the real digestion. With regard to the precise nature of this gastric juice of Spallan- zani, we have already observed that great contrariety of sentiment has prevailed ; and that, in ordinary cases, it is impracticable to procure it unmixed with the other fluids of the digestive mucous membrane. Spallanzani affirmed, that the only properties he de- tected in it, were, — a slightly salt, bitterish taste ; but that it was neither acid nor alkaline. Gosseb found it to vary according to the nature of the animal,— whether herbivorous or carnivorous; — and to be always acid in the former. Dumas0 held the same senti- ments, and proved, by experiments on dogs, that it was acid or alkaline, according as the animal had fed on vegetable or on ani- mal diet. He declared it, moreover, to be mawkish, thick, and viscid. Viridet,d Hunter,e and others, affirm, that it is always acid. Scopolif analyzed the gastric juice of the rook, and found it to consist of water, gelatin, a saponaceous matter, muriate of am- monia, and phosphate of lime. Carminatis describes it as salt, and bitter, and frequently acid; and MM. Macquarth and Vau- quelin,1 in the gastric juice ofthe ruminant animal, found albumen and free phosphoric acid.J All these analyses were made on the mixed fluid, to which the term gastric juice has been applied. That such a mixed fluid does exist in the stomach, at the time of chymification, and is largely concerned in the process, is proved by the facts already mentioned, as well as by the following. Ma- gendie11 asserts, that one of his pupils — M. Pinel — could procure, in a short time after swallowing a little water or solid food,as much as half a pint of it. M. Pinel " possessed the faculty of vomit- ing at pleasure." In this way, he obtained from his stomach, in the morning, about three ounces of the fluid, which was analyzed by Thenard, who found it composed of a considerable quantity of water, a little mucus, and some salts with a base of soda and lime; but it was not sensibly acid, either to the tongue or to reagents. On another occasion, Pinel obtained two ounces of fluid, in the same manner. This was analyzed by Chevreul,.and found to contain much water, a considerable quantity of mucus, lactic acid — united to an animal matter, soluble in water, and insoluble in » Op. citat. p. 139. b Experiences sur la Digestion, § 81, Gen. 1783. « Principes de Physiologie, Paris, 1806. i Tractatus Novus de Prima Coctione, &c. Genev. 1691. e Animal OScon. 1786. f In Spallanzani, § 244. g Recherche sulla Natura, &c. del Succo Gastrico, Milano, i785. h Mem. de la Societe de Med. Paris, 1786. i Fourcroy, Elem. de Chim. torn. iv. 1 See Burdach, Die Physiologie als Erfahrungswissenschaft, v. 240 and 431, Leips. 1835. k Precis, &c. ii. 11. VOL. I. — 46 , 542 DIGESTION. alcohol, —a little muriate of ammonia, chloride of potassium, and some chloride of sodium. Tiedemann and Gmelina procured the gastric fluid by making animals, that had fasted, swallow indigestible substances, such as flints. It always appeared to them to be produced in greater quan- tity, and to have a more acid character, in proportion as the ali- mentary matter was less digestible and less soluble ; and they assign it, as constituent elements, —chlorohydric acid ; acetic acid ; mucus ; no, or very little, albumen ; salivary matter ; osmazome ; chloride of sodium, and sulphate of soda. In the ashes, remaining after incineration, were, carbonate, phosphate, and sulphate of lime, and chloride of calcium. Leuret and Lassaigneb assign its composition, in one hundred parts, to be, — water,-ninety-eight; lactic acid, muriate of ammonia, chloride of sodium, animal matter soluble in water, mucus, and phosphate of lime, two parts. Bra- connot0 examined the gastric juice of a dog, and found it to con- tain — free chlorohydric acid in great abundance ; muriate of am- monia ; chloride of sodium in very great quantity ; chloride of calcium ; a trace of chloride of potassium ; chloride of iron ; chlo- ride of magnesium; colourless oil of an acid taste; animal matter soluble in water and alcohol, in very considerable quantity ; animal matter soluble in weak acids ; animal matter soluble in water, and insoluble in alcohol (salivary matter of Gmelin); mucus ; and phos- phate of lime. In the winter of 1832-3, the author was favoured by Dr. Beaumont,d with a quantity of the gastric secretion, ob- tained from the individual with the fistulous opening into the sto- mach, which was examined by himself and his friend, the late Pro- fessor Emmet, of the University of Virginia, and found to contain free chlorohydric and acetic acids, phosphates, and chlorides, with bases of potassa, soda, magnesia, and lime, and an animal matter — probably pepsin — soluble in cold water, but insoluble in hot. The quantity of free chlorohydric acid was surprising : on distilling the gastric fluid, the acids passed over, the salts and animal matter remaining in the retort: the amount of chloride of silver, thrown down on the addition ofthe nitrate of silver to the distilled fluid was astonishing. The author had many opportunities for examin- ing the gastric secretion obtained from the case in question. At all times, when pure or unmixed, except with a portion of the mucus of the lining membrane of the digestive tube, it was a trans- parent fluid, having a marked smell of chlorohydric acid ; and of a slightly salt, and very perceptibly acid,taste. The sourceof the chlo- rine or chlorohydricacid,as Dr. Proulesuggests,mustbethe common salt, existing in the blood, which he conceives to be decomposed by galvanic action. The soda, which is set free, remains, he thinks, a Recherches Experimentales, &c. edit, citat., Paris, 1827. b Recherches, &c, Paris, 1825. c Journal de Chimie Medicale, torn. ii. Ser. 2,1836, and Records of General Science, Jan.1836. * See a letter from the author to Dr. Beaumont — in Beaumont's Experiments, &c. on the Gastric Juice, p. 77; and the author's Elements of Hygiene, p. *16,Phila. 1835. e Bridgewater Treatise, Amer. Edit. p. 268, Philad. 1834. CHYMIFICATION. 543 in the blood, a portion of it being " requisite to preserve the weak alkaline condition essential to the fluidity of the blood ;" but the larger part being directed to the liver to unite with the bile. This is plausible, but, it need scarcely be added, not the less hypothetical. Drs. Purkinje and Pappenheima are of a similar opinion in regard to the source of the chlorohydric acid. From their galvanic experi- ments they think it follows, that the juices mixed with the food in the natural way, the saliva, the mucus, and the portions of chloride of sodium present therein, and still more the gastric mucous mem- brane itself, develope as much as is required ; and that if the ner- vous action in the stomach be either identical with, or analogous to, galvanism, it would be sufficient to account for the secretion of the quantity of chlorohydric acid requisite for digestion, without the assumption of a special organ of secretion. Liebigb denies, that in health lactic acid is formed in the sto- mach. In certain diseases, he states, lactic acid and mucilage are formed from the starch, sugar of the food ; and the property pos- sessed by these substances of passing by contact with animal sub- stances, in a state of decomposition, into lactic acid, has induced physiologists, without farther inquiry, he affirms, to assume that lactic acid is produced during digestion. Neither Prout nor Bra- connot, however, could detect it in the gastric juice; and, more- ever, it is not formed in artificial digestion. The diversity of the results obtained by chemical analysis; the difficulty of comprehending how the same fluid can digest sub- stances of such opposite character; and the uncertainty we are in, regarding the organs concerned in its production, have led some physiologists to doubt the existence of any such gastric juice or solvent, as that described by Spallanzani. Montegre,0 for example, in the year 1812, presented to the French Institute a series of ex- periments, from which he concluded, that the gastric juice of Spal- lanzani is nothing more than saliva, either in a pure state or changed by the chymifying action of the stomach and become acid. As Montegre was able to vomit at pleasure, he obtained the gastric juice, as it had been done by previous experimenters, in this manner, whilst fasting. He found it frothy, slightly viscid, and turbid ; depositing, when at rest, some mucous flakes, and commonly acid; so much so, indeed, as to irritate the throat, and to render the teeth rough. He was desirous of proving, whether this fluid were in any manner inservient to chymifica- tion. For this purpose, he began by rejecting as much as pos- sible by vomiting ; and, afterwards, swallowed magnesia to neu- tralize what remained of it. On eating after this, the food did not appear less chymified ; nor was it less acid; whence he con- cluded, that, instead of this fluid being the agent of chymification, 1 Miiller's Archiv. fur Anatomie u. s. w. Heft. 1, 1838, noticed in Brit, and For Med. Rev. Oct. 1838, p. 529. b Animal Chemistry, Gregory's and Webster's edit., p. 107, Cambridge, 1842. c Exper. sur la Digestion, p. 20, Paris, leJ24. 544 DIGESTION. it was, itself, nothing more than the saliva and the mucous secre- tions of the stomach, changed by the chymifying action of that viscus. To confirm himself in this view, he repeated, with the juice, Spallanzani's experiments on artificial digestion; making, at the same time, similar experiments with saliva, and the results were the same in the two cases. When gastric juice, not acid, was put into a tube, and placed in the axilla, — as in Spallanzani's experiments, — in twelve hours it was in a complete state of putrefaction. The same occurred to saliva, placed in the axilla. Gastric juice, in an acid state, placed in the axilla, did not become putrid, but this seemed to be owing to its state of acidity ; for the same thing happened to the saliva, when rendered acid by the addition of a little vinegar; and even to the gastric juice, — used in the experiment just referred to, — when mixed with a little vinegar. Again: — he attempted artificial digestion with the gastric juice, acid and not acid, fresh and old; but they were unsuccessful. The food always became putrid, but sooner, when the juice employed was not acid; and, if it sometimes liquified, before becoming putrid, this was attributed to the acidity of the juice, as the same effect took place, when saliva, mixed with a little vinegar was employed. Montegre, moreover, observed, that the food, rejected from the stomach, was longer in becoming putrid, in proportion to the time it had been subjected to the chymifying action ofthe stomach ; and he concluded, that the fluid, which is sometimes contained in the stomach when empty, instead of being a menstruum kept in reserve for chymification, is nothing more than the saliva, continually sent down into that viscus, and that its purity or acidity depends upon the chymifying action ofthe stomach.11 As regards the fluid met with in the stomach of fasting animals, Montegre's remarks may be true in the main ; but we have too many evidences in favour of the chemical action of some secretion from the stomach during digestion to permit us to doubt for a moment ofthe fact. Besides, some ofthe experiments of Montegre have been repeated and with opposite results. MM. Leuret and Lassaigne,b and Dr. Beaumont,0 for example, performed those re- lating to digestion after the manner of Spallanzani, and succeeded perfectly ; whilst they failed altogether in producing chymification with the saliva, either in its pure state, or acidulated with vinegar. By steeping the mucous membrane of any animal's stomach in an acid liquor, a solution is obtained, to which Eberled gave the name pepsin. This solution has the property of dissolving organic matter in a much higher degree than diluted acids. It dissolves coagu- lated albumen, muscular fibre, and animal matter in general. One grain ofthe digestive matter dissolved, in an experiment, one hun- dred grains of the coagulated white of egg. Eberle thought that * Chaussier and Adelon, in Diet, des Sciences Medicales, xx. 422. b Recherches sur la Digestion, Paris, 1S25. c Op. citat. p. 139. d Eberle, Physiologie der Verdauung nach Vcrsuchen, u. s. w., Wurzburg, 1834 ; Miiller, Archiv. Heft 1, 1836 ; London Lancet, p. 19, March 31, 1838. CHYMIFICATION. 545 all mucus has the property, when acidulated, of inducing decom- position and subsequent solution of the food ; but it would appear that no other mucus than that of the gastric mucous membrane is, when acidulated, adequate to the solution of food,a and, conse- quently, that there must be a peculiar substance, pepsin, which must be regarded as the true digestive principle.b This principle was not obtained by Schwann in a pure state ; but M. Wasmann0 would appear to have succeeded better. A solution, containing only TTifou- Part of pepsin and slightly acidulated is said to dissolve the white of an egg in six or eight hours.d But even were "the evidence adduced less positive, the following would be overwhelming, in favour of the existence of some secre- tion from the stomach, concerned in the digestive changes in that organ. Besides the fact of the most various and firm substances being reduced into chyme in the stomach, we find the secretions from its lining membrane possessing the power of coagulating albuminous fluids. It is upon the coagulating property of these secretions, that the method of making cheese is dependent. Rennet, employed for this purpose, is an infusion of the digestive stomach of the calf, which, on being added to milk, converts the albuminous portion into the state of curd ; and it is surprising how small a quantity of rennet is necessary to produce this striking effect. Fordycee and Young/ of Edinburgh, found that six or seven grains ofthe inner coat of a calf's stomach, infused in water, afforded a liquid, which coagulated more than one hundred ounces of milk, that is, more than six thousand eight hundred and fifty-seven times its own weight; and yet its weight was probably but little di- minished. The substance that possesses this property does not appear to be very soluble in water ; for the inside of a calf's sto- mach after having been steeped in water for six hours, and then well washed, still furnishes a liquor or infusion, which coagulates milk. Liebige has denied, that the fresh lining membrane of the stomach of the calf, digested in weak chlorohydric acid, gives to that fluid the power of dissolving boiled flesh or coagulated white of egg ; but Dr. Pereirah affirms, that he has found, by experiment, that a digestive liquor can be prepared from the fresh undried sto- mach of a calf. This had, indeed, been shown on the best autho- rity long ago. Mr. Hunter,1 for example, made numerous expe- riments upon the coagulating power ofthe secretions of the stomach, which show, that it exists in the stomachs of animals of very dif- » J. Miiller, Elements of Physiology, by Baly, pp. 518 and 542, Lond. 1838. b Miiller and Schwann, in Muller's Archiv. Heft 1, 1836; and Miiller, op. citat. <= Journ. de Pharmacie; and American Journal of Pharmacy, for Oct. 1840, p. 192. See, also, M. Dechamps, on Runnet and Chymosine, ibid. p. 194. ■i Graham's Elements of Chemistry, Amer. Edit., p. 695, Philad. 1843, and Thorn- son's Animal Chemistry, p. 229, Edinb. 1843. * A Treatise on the Digestion of Food, p. 57, 2d edit., Lond. 1791. f Thomson's System of Chemistry, 6th edit. iv. 596. g Animal Chemistry, Webster's Amer. Edit., Cambridge, 1842. h Treatise on Food and Diet, Amer. Edit., p. 36, New York, 1843, i Animal (Economy, &c, Lond. 1786. 46* 546 DIGESTION. ferent classes. The lining of the fourth stomach of the calf is in common use, in a dried state, for the purpose mentioned above; and it has been proved, that every part of the membrane possesses the same property. Hunter found, by experiment, that the mucus of the fourth cavity of a slink calf, made into a solution with a small quantity of water, had the power of coagulating milk; but that found in the three first cavities possessed no such power. This mucus, even after it had been kept several days, and was beginning to be putrid, retained the property. The duodenum and jejunum, with their contents, likewise coagulated milk; but the process was so slow as to give rise to the suggestion, that it might have occurred independently of the intestines employed for the purpose. He found, that the inner membrane ofthe fourth cavity in the calf, when old enough to be killed for veal, had the same property. Portions of the cuticular part, of the massy glandular part, and of the portion near the pylorus of the boar's stomach, being prepared as rennet, it was found, that no part had the effect of producing coagulation but that near the pylorus, in which part the gastric glands of the animal are especially conspicuous. The crop and gizzard of a cock were salted, dried, and afterwards steeped in water. The solution, thus obtained, was added to milk; the portion of the crop coagulated it in two hours, that of the giz- zard in half an hour. The contents of a shark's stomach and duodenum coagulated milk immediately. Pieces of the stomach were washed clean, and steeped for sixteen hours in water. The solution coagulated milk immediately. Pieces of the duodenum produced the same effect. When the milk was heated to 96°, the coagulation took place in half an hour; when it was cold, in an hour and a quarter. The stomachs of the salmon and thornback, made into rennet, coagulated milk in four or five hours. But these experiments of Mr. Hunter do not inform us of the particular se- cretions, that are productive of the effect. They would, indeed, rather seem to show, that it is a general property of the whole internal membrane. To discover the exact seat of the secretion, and especially whether it be not in the gastric glands, Sir Everard Homea selected those of the turkey; which, from their size, are better adapted for such an experiment than those of any other bird, except the ostrich. A young turkey was kept a day without food, and was then killed. The gastric glands were carefully dis- sected separately from the lining of the cardiac cavity ; cutting off the duct of each before it pierced the membrane, so that no part but the glands themselves were removed. Forty grains, by weight, of these glands were added to two ounces of new milk; and similar . experiments were made with rennet; with the lining of the cardiac cavity of the turkey; and with the inner membrane of the fourth cavity of the calf's stomach. Coagulation, and the separation into curds and whey, were first effected by the rennet. Next to this, and simultaneously, came the gastric glands, and the fresh stomach i Lectures on Comparative Anatomy, i. 299, Lond. 1814, and iii. 134, Lond. 1823. CHYMIFICATION. 547 It also resembles them, Gastric Glands of the Oesophagus magnified fifteen times. in the secretion which it produces coagulating milk, whilst none ofthe inspissated juices, met with in these cavities, according to Sir Everard, affect milk in the same way. From these facts, he thinks, there can be no longer any doubt entertained, that the gastric glands have the same situa- tion respecting the cavity of the stomach as in birds. Yet M. Mon- tegre3 denies that the gastric juice has any coagulating power ! In some experiments, undertaken by M. J. F. Simon,b with a view to determine, whether the stomach ofthe child possessed the same properties of coagulating milk as the stomach of the calf, he found that cow's milk was not coagulated by it, but that, when a quantity of the colostrum of the mother of a child, which died when five days old, was obtained, and a piece of calf's stomach was introduced into it, the milk was coagulated. Another property, manifestly possessed by the secretion in ques- tion, is that of preventing putrefaction, or of obviating it, in sub- stances, exposed to its action. Montegre and Thackrah0 deny it this property also, but there can be no doubt of its existence. Spallanzani, Fordyce, and others, have ascertained, that, in those animals which frequently take their food in a half putrid state, the first operation of the stomach is to disinfect, or remove the foetor 1 Experiences sur la Digestion, Paris, 1824. " Muller's Archiv. Heft i. 1839, and Brit, and For. Med. Rev. Oct. 1839, p. 549. c Lectures on Digestion and Diet, p. 14, Lond. 1824. 548 DIGESTION. from the aliment received into it. We have already alluded to many facts elucidative of this power. Helm of Vienna,3 in the case of a female who had a fistulous opening in her stomach, ob- served, that substances, which were swallowed in a state of acidity or putridity, soon lost those qualities in the stomach ; and the same power of resisting and obviating putrefaction has been exhibited in experiments, made out of the body. Nothing could be more un- equivocal, as regards the possession of this property by the gastric fluid, than the experiments of Dr. Beaumont and the author,b with the secretion obtained from the subject of his varied investigations. In the presence of the author's friend, N. P. Trist, Esq. — then con- sul ofthe United States at the Havana, — the odour of putrid food was as speedily removed by it as by chlorinated soda, employed at the same time on other portions. The explanation of this property, as well as that of coagulation, has been a stumbling-block to the chemical physiologist. " We can only say concerning it," says Dr. Bostock,0 " that it is a chemical operation, the nature of which, and the successive steps by which it is produced, we find it diffi- cult to explain ; at the same time, that we have very little, in the way of analogy, which can assist us in referring it to anymore general principle, or to any of the established laws of chemical affinity." The cases of what are termed digestion of the stomach after death afford us, likewise, remarkable examples of the presence of some powerful agent in the stomach ; as well as of the resistance to chemical action, offered by living organs. Powerful as the action ofthe gastric juice may be, in dissolving alimentary sub- stances, it does not exert it upon the coats of the stomach during life. Being endowed with vitality, they effectually resist it. But when that viscus has lost its vitality ; its parietes yield to the che- mical power of the contained juices ; and become softened, and, in part, destroyed. Hunterd found the lining membrane of the sto- mach destroyed, in several parts, in the body of a criminal, who, for some time before his execution, had been prevailed upon, in consideration of a sum of money, to abstain from food. Since Hunter's time, numerous examples have occurred, and have been recorded by Baillie, Allan Burns, Haviland, Grimaud, Pascalis, Cheeseman, J. B. Beck, Chaussier, Yelloly, Gardner, Treviranus, Godecke, Jager, Carswell, and others.e The fact is of importance in medical jurisprudence; and, until a better acquaintance with the subject would, doubtless, have been set down as strong corro- borative evidence in cases of suspected poisoning. It is now es- * Rudolphi, Grundriss der Physiologie, &c. Berlin, 1821. b See the author's Elements of Hygiene, p. 216, Philad. 1835. c Edit, citat. p 571. d Phil. Transact, lxii.; and Observations on certain parts ofthe Animal Economy, p. 229, Lond. 1786. e See Beck's Medical Jurisprudence, 6th edit. ii. 311, Albany, 1838; Carswell's Path. Anat. No. 5, Lond. 1833 ; also, T. Wilkinson King, Guy's Hospital Reports. vii. 139, Lond. 1842. r CHYMIFICATION. 549 tablished, that solution of the stomach may take place after death, without there being the slightest reason for supposing, that any thing noxious had been swallowed. The experiments of Drs. Wilson Philip3 and Carswellb are sig- nally corroborative of this physiological action of the gastric juice. On opening the abdomen of rabbits, which had been killed imme- diately after having eaten, and were allowed to lie undisturbed for some time before examination, the former found the great end of the stomach soft, eaten through, and sometimes altogether con- sumed ; the chyme being covered only by the peritoneal coat, or lying quite bare for the space of an inch and a half in diameter; and, in this last case, a part of the contiguous intestines was also destroyed; whilst the cabbage, which the animal had just taken, lay, in the centre of the stomach, unchanged, if we except the al- teration that had taken place, in the external parts of the mass it had formed, in consequence of imbibing gastric fluid from the half- digested food in contact with it. Why the perforation takes place, without the food being digested, is thus explained by Dr. Philip. Soon after death, the motions of the stomach, which are constantly carrying on towards the pylorus the most digested food, cease. The food, which lies next to the surface of the stomach, thus be- comes fully saturated with gastric fluid, neutralizes no more, and no new food being presented to it, it necessarily acts on the sto- mach itself, now deprived of life, and equally subject to its action with other dead animal matter. It is extremely remarkable, how- ever, that the gastric fluid of the rabbit, which, in its natural state, refuses animal food, should so completely digest its own stomach, as not to leave a trace of the parts acted upon. Dr. Philip remarks, that he has never seen the stomach eaten through except in the large end ; but, in other parts, the external membrane has been in- jured. Mr. A. Burns,0 however, affirms, that in several instances, he found the forepart of the stomach perforated, about an inch from the pylorus, and midway between the smaller and larger cur- vatures. From all these facts, then, we are justified in concluding, that the food in the stomach is subjected to the action of a secretion, which alters its properties, and is the principal agent in converting it into chyme. But many physiologists, whilst they admit,thatthechangeeffected in the stomach is of a chemical character, contend, that the nature of the action is unlike what takes place in any other chemical pro- cess, and that it is, therefore, necessarily organic and vital, and appertaining to vital chemistry. Such are the sentiments of For- a Treatise on Indigestion, Lond. 1821. b Ibid, and Edinb. Med. and Surg. Journal, Oct. 1830; and art. Perforation ofthe Hollow Viscera, in Cyclopaedia of Practical Medicine, P. xvi. p. 272, Lond. 1833. See, also, Dr. Bowditch, in Append, to Amer. Edit, of Louis on Typhus, Boston, 1836; and Alfred S. Taylor, on Perforations of the Stomach, from Poisoning and Disease, in Guv's Hospital Reports, Aug. 1839, p. 8. c Edinb. Med. and Surg. Journal, vi. 132. 550 DIGESTION. dyce,a of Broussais,b of Chaussier and Adelon,0 and others. Prout suggests, that the stomach must have, within certain limits, the power of organizing and vitalizing the different alimentary sub- stances ; so as to render them fit for being brought into more inti- mate union with a living body, than the crude aliments can be sup- posed to be. It is impossible, he conceives, to imagine, that this organizing agency of the stomach can be chemical. It is vital, and its nature completely unknown. The physiologist should not, however, have recourse to this explanation, until every other has failed him. It is, in truth, another method of expressing our igno- rance, when we affirm that any function is executed in an organic or vital manner; nor is this mode of explaining the conversion of the aliment into chyme necessary : the secretion of the matters, that are the great agents of chymification, is doubtless vital; but when once secreted, the changes, effected upon the food, are pro- bably unmodified by any vital interference, except what occurs from temperature, agitation, &c, which can only be regarded as auxiliaries in the function. It is in this way, that digestion is influenced by the nervous system. The effect of the different emo- tions upon the digestive function is often evinced, and has already been alluded to; but the importance of the nervous influence to this function has been elucidated, in an interesting manner to the physiologist, of late years chiefly. Baglivi,d having tied the two nerves of the eighth pair in dogs, found that they were affected with nausea and vomiting, and that they obstinately refused food. Since Baglivi's time, the same results have been obtained by many physiologists. De Blainville, having repeated the operation on pigeons, found the vetch, in their crops, entirely unchanged, and chymification totally prevented. Legallois,eBrodie,fPhilip,sDupuy, Clarke Abel, Hastings,11 and others, — on carefully repeating the experiments — also announced, that, after this operation, the diges- tive process was entirely suspended.1 The result of these experi- ments was, however, contested by several physiologists of emi- nence, who affirmed, that, after the division of the eighth pair of nerves, digestion continued nearly in the natural state, or, at most, was only slightly impeded. Mr. Broughton) asserted, that he had made the section on eleven rabbits, one dog, and two horses; and that digestion was not destroyed. Magendiek expresses his belief, that the annihilation of chymification was owing to the disturbance of respiration, caused by the division of the nerves; and he affirmed that digestion continued when care was taken to cut the nerve within the thorax, lower down than the part which furnishes the » On the Digestion of Food, 2d edit. Lond. 1791. b Traite de Physiologie, &c. translated by Drs. Bell and La Roche, p. 323. c Diet, de Sciences Medicales, ix. d Opera Omnia, Lugd. Bat. 1745. e Sur le Principe de la Vie, p. 214, Paris.l 842. f Phil. Trans, for 1814. g Experimental Inquiry, &c. Lond. 1817. b See Journal of Science and Arts. vii. ix. x. xi. and xii. ' See Ley, in App. to Laryngismus Stridulus, p. 447, Lond. 1836. i Ibid. x. 292. k pr6ds, &c. ii. 102. CHYMIFICATION. 551 pulmonary branch. MM. Leuret and Lassaigne assert,8 that they found chymification continue, notwithstanding the division of these nerves ; and Dr. Hollandb thinks he has proved, that the suspension of the digestive function is not produced by the influence of these nerves being withdrawn from the stomach, but by the disturbance ofthe circulating system ; for when the natural conditions of this system were maintained, after the division of the nerves in ques- tion, the function of digestion still continued to be properly per- formed ; showing that the nervous connexion between the brain and stomach is not essential to the process of digestion, to the secre- tion of the gastric solvent, or to the possession of contractility by the muscular fibres of the stomach. •In opposition to these experiments, those of Dupuytren may be adduced. He divided, separately, the portions of the eighth pair of nerves, distributed to the pulmonary, circulatory, and digestive apparatuses, and always found, that when the section was made below the pulmonary plexus, chymification was suspended. But how are we to explain the discrepancy between these results, and those of MM. Broughton and Magendie ? Adelon0 has supposed, that as the eighth pair is not the only nerve distributed to the sto- mach, — the great sympathetic sending numerous filaments to it,— these filaments, in the experiments of MM. Broughton and Magen- die, might have been sufficient to keep up for some time the chymi- fying action of the stomach; and, again, he suggests, whether the nervous influence of the stomach may not have still persisted for a time after the section of the nerve, like other nervous influences, which, he conceives, continue for some time, even after death; and lastly, he thinks it probable, that, in the cases, in which chymi- fication continued, the experiment was badly performed. Most of these reasons, however, would apply with as much force to the experiments on the other side of the question. Why were not the agency of the great sympathetic, and the continuance of the ner- vous influence for some time after the section of the nerve, evi- denced in the experiments of Dupuytren, and of Wilson Philip, Hastings, and others ? More recent experiments by Wilson Philip,d Breschet, Milne Edwards, and Vavasseur,e have shown, that the mere division of the nerves, and even the retraction of the divided extremities for the space of one-fourth of an inch, does not prevent the influence from being transmitted along them to the stomach; but that, if a portion of the nerve be actually removed, or the ends folded back, chymification is wholly, or in part, suspended. Most of the experimenters agree with Sir Benjamin Brodie in the opinion, that chymification is suspended, owing to the secretion of the gastric juice having been arrested by the division of the nerves under a Edinburgh Med. and Surg. Journal, xciii. 365 ; and Recherches sur la Digestion, Paris, 1825. t Inquiry into the Principles, &c. of Medicine, i. 444, Lond. 1834. c Physiologie de l'Homme, &c 2de 6dit. vol. ii. Paris, 1829. d Philos. Transact, for 1822. « Archives Generates de Med. Aout. 1823. 552 DIGESTION. whose presidency it is accomplished. MM. Breschet and Milne Edwards, however, conceive, that the effect is owing to paralysis ofthe muscular fibres of the stomach produced by the section of the nerves ; in consequence of which the different portions of the alimentary mass are not brought properly into contact with the coats of the stomach, so as to be exposed to the action of its secre- tions ; and they affirm, that, when the galvanic influence is made to pass along the part of the nerve attached to the stomach, its effect is to restore the due action ofthe fibres ; and, that a mechani- cal irritant, applied to the lower end of the -divided nerves, pro- duces a similar kind of change on the food in the stomach: from which they conclude, that the use of the par vagum, as connected with the functions of the stomach, is to bring the alimentary mass into the necessary contact with the gastric juice. These experi- ments were repeated in London by Mr. Cutler, under the inspec- tion of Dr. Philip and Sir B. Brodie ; but the effects of mechanical irritation ofthe lower part ofthe divided nerve did not correspond with those observed by MM. Breschet and Milne Edwards.3 The experiments of F. Arnoldb lead him also to infer, that the nerves of the stomach appear to exert an influence on chymification in so far as the process depends upon the various motions of the organ.0 Recently, Mr. Longetd has endeavoured to reconcile these dis- cordant results. Having opened many dogs, he ascertained, that in the greater number, irritation of the pneumogastric nerves in- duced contraction of the stomach. Frequently, during his expe- riments, he saw the stomach assume the hour-glass form. In a few dogs, the movements of the stomach, on the irritation of the nerve, were scarcely perceptible. After repeating his experiments on forty dogs, he recognized that the difference in the results ob- tained depended on the condition of the stomach itself. Thus, if the animal was opened when the stomach was full, irritation of the pneumogastric nerves caused the most manifest movements of the organ; but, when empty, scarcely any movement was excited : the movements, in fact, were feeble in proportion to the time that had elapsed from the period of chymification,or of filling the stomach. M. Longet thinks, that these facts account for the different results arrived at by experimentalists in regard to the in- fluence of the pneumogastric nerves over the movements of the stomach; for, if the same experiments were made when the stomach was in different states, they might readily arrive at opposite conclusions from them. He was never able to ex- cite any movement of the coats of the stomach, by irritating a Bostock's Physiology, 3d edit. p. 523, Lond. 1836 ; Ley, op. cit.; Sir A. Cooper in Guy's Hospital Reports, i. 474, Lond. 1836 ; and Miiller, Elements of Physiology byBaly, p. 548, Lond. 1838. b Lehrbuch der Physiologie des Menschen, Zurich, 1836-7; noticed in British and Foreign Medical Review, for Oct. 1839, p. 478. c See also, Valentin, Traite" de Nevrologie, traduit par Jourdan, p. 462, Paris, 1843. 4 Comptes Rendus, Fevr. 1842. CHYMIFICATION. 553 or galvanizing the filaments of the great sympathetic or the semi- lunar ganglia. On the whole, the proposition of Dr. Philip, — that if the eighth pair of nerves be divided in such a manner as to effectually inter- cept the passage of the nervous influence, digestion is suspended, — is generally considered to be established ; although it must, we think, be admitted with Mr. Mayo,a that the subject remains in- volved in great uncertainty. Like other secretions, that of the gastric juice, although capable of being modified, by the nervous influence, cannot be regarded as dependent upon it. The secre- tion, of the true acid character and solvent powers, is not always checked by section of the nerve ; and the experiments of Dr. John Reidb and others, have sufficiently shown, that the integrity of those nerves is not a condition absolutely necessary for the per- formance of secretion in the stomach, whilst at the same time they prove, that the secretions usually poured into the interior of the stomach may be modified in a most important manner, by causes acting through those nerves. It is denied, however,»by Miiller, that galvanism has any influence in re-establishing the gastric secretion, when it has been checked by division of these nerves. Finally, Dr. Philip found, that every diminution of the nervous influence, — the section of the medulla spinalis at the inferior part, for example,— deprives the stomach of its digestive faculty; and MM. Edwards and Vavasseur obtained the same result by the re- moval of a certain portion of the hemispheres of the brain, or by the injection of opium into the veins in a sufficient quantity to throw the animal into a deep coma. Of all these theories of chymification, that of chemical action, aided by the collateral circumstances to be presently mentioned, can alone be embraced ; yet, how difficult is it to comprehend, that any one secretion can act upon the immense variety of animal and vegetable substances, which are employed as food. The discovery of the chlorohydric and acetic acids and of pepsin in the secretion aids us in solving the mystery expressed by the well known pithy and laconic observation of Dr. William Hunter in his lectures: " Some physiologists will have it, that the stomach is a mill: others, that it is a fermenting vat; others, again, that it is a stewpan ; — but, in my view of the matter, it is neither a mill, a fermenting vat, nor a stewpan ;—but a stomach, gentlemen, a stomach." Allusion has been already made to pepsin as an organic com- pound thrown off from the stomach, which is an active agent in digestion. It had been observed in the experiments of Eberle and Schwann, that although acids alone have little power in digesting food, they act energetically, when combined with mucus of the stomach. Eberle thought, that the acidulated mucus of any mem- a Outlines of Human Physiology, 4th edit. p. 122, Lond. 1837. See, also, Fletcher's Rudiments of Physiology, P. ii. b. p. 56, Edinb. 1836. b Edinb. Med. and Surg. Journal, April, 1839. VOL. I. — 47 554 DIGESTION. brane would produce this effect, but J. Miiller and Schwann found it to be restricted to that of the stomach. The agency of the pep- sin is regarded by Liebiga to be similar to that of the diastase in the germination of seeds. Both are bodies in a state of transformation or decomposition; the latter effecting the solution of the starch, that is, its conversion into sugar ; and the former the conversion of alimentary matter into chyme. The present belief amongst phy- siologists "and chemists, from all these experiments, as well as those of Wasmann and others, is, that the pepsin, by inducing a new arrangement of the elementary particles or atoms of the ali- mentary matter, disposes it to dissolve in the gastric acids. Chlo- rohydric acid, indeed, when alone, dissolves white of egg by ebul- lition, just as it does under the influence of pepsin ; so that pepsin replaces the effect of a high temperature, which is not possible in the stomach.b Liebig, consequently, does not believe, that the digestive process is a simple solution, but a species of fermentation, not identical, however, IHth any of the known processes of fermentation occur-. ring in organic matters out of the body. Magendie examined the gases in the stomach and intestines of executed criminals and ob- tained the following results :— a, in the case of an individual who had taken food in moderation an hour previous to death; b, in the case of one who had eaten two hours previously; and c, in the case of one who had done so four hours previous to execution. 100 volumes of the gas contained Oxygen. Azote. Carbonic acid. Inflammable gas. From the stomach, 11-00 71-45 1400 3-55 small intestines, 00 00 20-03 24-39 55-33 £--------large do. 00-00 5103 43-50 5-47 rFrom the stomach, 0000 00-00 00-00 00-00 b 2--------small intestines, 00-00 8 85 40-00 51-15 £--------large do. 00-00 18-40 7000 11-60 f" From the stomach, 0000 0000 0000 0000 c<-------small intestines, 00-00 66-60 2500 8-40 (_--------large do. 00-00 45-96 42-86 11-18<= From these it appears, that when the execution occurred not longer than an hour after a meal, oxygen was found in the sto- mach ; and when not until two hours it had entirely disappeared, and a large quantity of azote was found in the intestines, with an entire absence of oxygen; whence it is inferred, that the oxygen of the air is separated from the nitrogen in the stomach; and that the oxygen is employed in digestion. The view of Liebig is, that the oxygen occasions a molecular action in the pepsin or animal matter separated from the stomach in the gastric juice, and that this intestine motion is communicated to the molecules ofthe albu- men or protein of the food, so that the latter is rendered soluble in the chlorohydric acid/1 The oxygen Liebig refers to the atmo- 1 Animal Chemistry, Gregory and Webster's edit. p. 106, Cambridge, Mass, 1842. b Graham's Elements of Chemistry, Amer. Edit, by Dr. Bridges, p. 696, Philad. 1843. c Liebig, op. cit. p. 289. d Mr. Ancell, Lond. Lancet, Dec. 16,1842, p. 419. CHYMIFICATION. 555 spheric air enclosed in the saliva during mastication, and in that way introduced into the stomach. Very recently, fresh researches have been made into the pheno- mena of digestion by two competent observers, MM. Bouchardat and Sandras,3 who are led to deduce the following conclusions from their different experiments. First. The functions of the sto- mach, in digestion, consist in dissolving, with the aid of chloro- hydric acid, all albuminous matters, as fibrin, albumen, casein, and gluten. Secondly. This acid, if diluted with 5000 parts of water, dissolves the same-matters out of the body, provided they are not cooked; but if boiled, the solution has no action upon them. As they are found, however, to be dissolved in the stomach, it is pro- bable that some other agency is at work than simple solution by means of chlorohydric acid ; but the presence of that acid appears to be always indispensable. Thirdly. As far as albuminous mat- ters are concerned, digestion and absorption take place exclusively in the stomach by the veins; the intestines present scarcely any traces of those dissolved matters that exist in such abundance in the stomach. Fourthly. Solution of fecula likewise occurs in the stomach. This principle does not appear to pass into the state of sugar ; and the experiments did not even warrant the statement, that it passes into that of soluble starch ; but they regard as proved, its transformation into lactic acid. Fifthly. The absorption of this kind of aliment appears to take place less exclusively from the stomach than that of albuminous matters, — a circumstance* which accords with the special disposition and length of the intestines of animals not carnivorous. Sixthly. Fatty matters are not acted on in the stomach. They pass into the duodenum forming an emulsion with the alkalies furnished by the liver and pan- creas. This emulsion is found abundantly throughout the whole course of the intestines. Seventhly. The chyle appeared to be somewhat less abundant, but presented similar characters in ani- mals that were killed after long fasting; and in those killed after having taken copious meals of albuminous matters and fecula. In those, however, that were fed on fat, this principle was found in it in considerable proportion. According to these views, — which were favourably reported upon to the Academie Royale des Sciences of Paris, on the 30th of January, 1843, by MM. Payen, Magendie, Flourens, Milne Ed- wards and Dumas,i> and " the authors encouraged to persevere in a study which still presents so many problems for solution, into which they have but entered, although they have already made some curious observations,"—most articles undergo complete diges- tion in the stomach; but fat requires an admixture with the secre- tions poured into the intestines, and is alone taken up by the chy- liferous vessels. MM. Bouchardat and Sandras do not, however, 1 Annales des Sciences Naturelles, Oct. 1842, or Edinb. Med. and Surg. Journal, Jan. 1843. i> Encyclographie des Sciences M6dicales, Fe\r. 1843, p. 159. 556 DIGESTION. restrict their agency to the absorption of fat. They suggest — and it can only be regarded as a suggestion — that the abdominal glands prepare for the chyliferous" vessels and thoracic duct a chyle, the alkaline character of which is in a direct ratio with the acidity developed in the stomach during digestion. This chyle — not ob- tained from the food but by a true process of secretion — enters the blood through the chyliferous apparatus,to neutralize the acid, which was indispensable for the solution ofthe food in the stomach to prepare it for absorption from that organ. Should the views of MM. Bouchardat and Sandras be established, they would modify materially our notions in regard to the physiology of the digestion of solids. It need hardly be said, however, that a succession of repeated and careful experiments, tending to the same results, will be necessary before they can be regarded as worthy of more than a passing notice. The view, that digestion can be accomplished by the veins of the stomach, independently of the action of any gastric secretions, has been maintained ; but is now probably abandoned or materially modified by its supporters.3 In conclusion:—Let us inquire into the various agencies to which the food is exposed during the progress of chymification. First. It becomes mixed with the secretions, already existing in the stomach,as well as with those excited by its presence. Secondly. It is agitated by the movement of the neighbouring organs, and the peristaltic motion of the stomach itself. Thirdly. It is ex- posed to a temperature of 100° of Fahrenheit, which, during the ingestion of food, does not rise higher : exercise elevates, whilst sleep, or rest, or a recumbent posture, depresses it. (Beaumont.)b After the food has been, for some time, subjected to these influ- ences, the conversion into chyme commences. This always takes place from the surface towards the centre: the nearer it lies to the surface of the stomach, the more it is acted on ; and that part of it which is in contact with the lining membrane is more digested than any other ; appearing as if corroded by some chemical substance capable of dissolving it. Dr. Wilson Philip0 asserts, that the new food is never mixed with the old; the former being always found in the centre, sur- rounded on all sides by the latter. If the old and new be of dif- ferent kinds, the line of separation between them is so evident, that the old may be completely removed without disturbing the new; and if they be of different colours, the line of demarcation can frequently be distinctly traced through the parietes of the organ before they are laid open. Dr. Beaumont,d however, affirms, that this statement is not correct; that, in a very short time, the food, already in the stomach, and that subsequently eaten, become com- a A Physiological Essay on Digestion. By Nathan R. Smith, M.D., &c, New York, 1825. b On the Gastric Juice, p. 274. c Exper. Inquiry, ch. vii. sect. 1 ; and Treatise on Indigestion, Lond. 1821. d Op. citat. p. 89. CHYMD7ICATI0N. 557 mingled. In the subject of his experiments, he invariably found, that the old and the new food, if in the same state of comminution, were readily and speedily united in the stomach. The conversion of the food into chyme, it has been conceived, commences in the splenic portion, is continued in the body of the viscus, and is completed in the pyloric portion. On this point, the observations of Dr. Philip differ somewhat from those of Magendie,a the former appearing to think, that chymification is chiefly accomplished in the splenic portion and middle of the sto- mach ; whilst the latter affirms, that it is mainly,in the pyloric portion that chyme is formed; the alimentary mass appearing to pass into it by little and little, and during its stay there,to undergo the transformation. He further affirms, that he has frequently seen chymous matter at the surface ofthe alimentary mass filling * the splenic half; but that, commonly, it preserves its properties in this part of the stomach. The precise steps of this change into chyme cannot be indicated. Some of the results, at different stages of the process, have been observed on animals ; and pathological cases have occasionally occurred, which enabled the physiologist to witness what was going on in the interior of the stomach ; but with perhaps one exception, those opportunities have not been much improved. Burrowsb relates a case of fistulous opening - into the stomach. The subject of the case was not seen by him until twenty-seven years after the injury, at which time the man was, to all appearance, healthy. But he was drunken, and dis- sipated, and the following year he died. Such a case is related by Schenk ;° and Louisd refers to similar cases that occurred to Foubert and Covillard. Helm, of Vienna/ published a case of the kind, to which reference has already been made ; and an interest- ing case occurred at the Hospital La Charite of Paris, which sheds some little light on the subject/ The aperture, which was more than an inch and a half long and an inch broad, exposed the in- terior of the organ. At the admission of the female into the Hos- pital, she ate three times as much as ordinary persons. Three or four hours after a meal, an irresistible feeling compelled her to remove the dressings from the fistulous opening, so as to allow the escape of the food which the stomach could no longer con- tain, when the contents came out quickly, accompanied by more or less air. They possessed a faint smell but had neither acid nor alkaline properties; the grayish paste, of which they consisted, when diluted with distilled water, not affecting the vegetable blues. The digestion was far from complete ; yet, frequently the odour of wine was destroyed ; and bread was reduced to a soft, viscid, thick substance, resembling fibrin recently precipitated a Precis, &c. edit. cit. ii. 88. b Transactions of the Royal Irish Academy, vol. iv. « Observ. Medic. Rar. Novarum, &c. lib. iii. Francof. 1609. Up. citat. and Amer. Journal, &c. for Aug. 1834, p. 465. e Valentin, cited by Mr. Paget, Brit, and For Med. Kev. July, 1842, p. 290. CHYLIFEROUS APPARATUS. 597 membrane of the veins, but not lined by epithelium." Some anatomists de- scribe an external coat, which is form- ed of condensed celular tissue, and unites the chyliferous vessels to the neighbouring parts. The mesenteric glands ox ganglions are small,irregularly lenticnlar,organs; varying in size from the sixth of an inch, to an inch ; nearly one hundred in number, and situate between the two laminae of the mesentery. In them, the lymphatic vessels of the ab- domen terminate, and the chyliferous vessels traverse them, in their course from the small intestine to the thoracic duct, Their substance is of a pale rosy colour; and their consistence moderate. By pressure, a transparent and inodorous fluid can be forced from them ; which has neverbeen examined chemically.b Anatomists differ with regard to their structure. According to some, they consist of a pellet of chy- liferous vessels, folded a thousand times upon each other; subdividing and anastomosing almost ad infini- tum ; united by cellular tissue, and receiving a number of bloodvessels. In the opinion of others, again, cells exist in their interior, into which the afferent chyliferous vessels open ; and whence the efferent set out. These are filled with a milky fluid, carried thither by the lacteals or exhaled by the bloodvessels.0 Notwithstanding the labours of Nuck,d Hewson, Aber- nethy, Mascagni, Cruikshank, Haller,e Beclard/and other distinguished ana- tomists, the texture of these, as well as of the lymphatic glands or ganglions in general, is not demonstrated. All that we know is, that the chyliferous and sanguiferous vessels become ex- tremely minute in their substance; and that the communication between Fig. 142. Course of Thoracic Duct. 1. Arch of aorta. 2. Thoracic aorta. 3. Abdominal aorta ; showing its principal branches divided near their origin. 4. Arteriainnominata,divid- ing into right carotid and right sub- clavian arteries. 5. Left carotid. 6. Left subclavian. 1. Superior cava, formed by the union of 8, the two vense innominate; and these by the junc- tion 9, of internal jugular and sub- clavian vein at each side. 10. Greater vena azygos. 11. Termination of the lesser in greater vena azygos. 12. Receptaculum chyli; several lym- phatic trunks are seen opening into it. 13. Thoracic duct, dividing opposite middle of dorsal vertebra into two branches which soon reunite; course of duct behind arch of aorta and left subclavian artery is shown by a dotted line. 14. The duct making its turn at root of the neck and receiving several lymphatic trunks previously to termi- nating in posterior aspect of junction of internal jugular and subclavian vein. 15. Termination of trunk of ductus lymphaticus dexter. — ( WHsoik) a Henle, op. cit. b Magendie, Precis, &c.; and Breschet, Le Systerr.e Lymphatiques, Pans, 1836. c Miiller, op. cit. p. p. 272. d Adenologia, Lugd. Bat. 1696. e Element. Physiol, ii. 3. f Addit. a Bichat, p. 128, Paris, 1821. 598 ABSORPTION. the afferent and efferent vessels, through them, is very easy; as mercurial injections pass readily from the one to the other. The thoracic duct,g, Fig. 140, and 13, Fig. 142, is formed by the junction of the chyliferous trunks with the lymphatic trunks from the lower extremities. The receptaculumchyli,a\xeadydescxibed,forms its commencement. After getting from under the diaphragm, the duct proceeds, in company with the aorta, along the right side of the spine, until it reaches the fifth dorsal vertebra ; where it crosses over to the left side of the spine, behind the oesophagus. It then ascends behind the left carotid artery ; runs up to the interstice between the first and second vertebrae of the chest; where, after receiving the lymphatics, which come from the left arm and left side of the head and neck, it suddenly turns downwards, and termi- nates at the angle, formed by the meeting of the subclavian and internal jugular veins of the left side. To observe the chyliferous apparatus to the greatest advantage, it should be examined in an individual recently executed, or killed suddenly, two or three hours after having eaten; or in an animal, destroyed for the purpose of experiment, under the same circum- stances. The lacteals are then filled with chyle, and may be readily recognised, especially if the thoracic duct have been pre- viously tied. These vessels were unknown to the ancients. The honour of their discovery is due to Gaspard Aselli,a of Cremona, who, in 1622, at the solicitation of some friends, undertook the dissection of a living dog, which had just eaten, in order to demon- strate the recurrent nerves. On opening the abdomen, he per- ceived a multitude of white, very delicate filaments, crossing the mesentery in all directions. At first, he took them to be nerves ; but having accidentally cut one, he saw a quantity of a white liquor exude, analogous to cream. Asellialso noticed the valves,but he fell into an important error regarding the destination of the vessels; — making them collect in the pancreas, and from thence proceed to the liver. In 1628, the human lacteals were discovered. Gas- sendib had no sooner heard of the discovery of Aselli than he spoke of it to his friend Nicholas-Claude-Fabrice de Peiresc, senator of Aix; who seems to have been a most zealous propagator of scien- tific knowledge. He immediately bought several copies of the work of Aselli, which had only appeared the year previously, and distributed them amongst his friends of the profession. Many experiments were made upon animals, but the great desire of De Peiresc was, that the lacteals should be found in the human body. Through his interest, a malefactor, condemned to death, was given up, a short time before his execution, to the anatomists of Aix ; who made him eat copiously ; and, an hour and a half after exe- cution, opened the body, in which, to the great satisfaction of De Peiresc, the vessels of Aselli were perceived, in the clearest manner. Afterwards, in 1634, John Weslingc gave the first graphic repre- * De Lactibus seu Lacteis Venis, &c. Mediol. 1627 ; also, in Collect. Oper. Spigelii, edit. Van der Linden ; and in Manget. Theatr. Anatom. b Vita Peirescii, in Op. omnia, v. 300. ° Syntagm. Anatom. viii. 170. CHYLE. 599 sentation of the chyliferous vessels of the human body ; and he subsequently indicated, more clearly than his predecessors, the thoracic duct and the lymphatics. Prior to the discovery of the chyliferous and lymphatic vessels, the veins, which arise in im- mense numbers from the intestines, and, by their union with other veins, form the vena porta, were esteemed the agents of.absorp- tion ; and, even at the present day, they are considered, by some physiologists, to participate with the chyliferous vessels in the func- tion ; — with what propriety we shall inquire hereafter.3 2. CHYLE. The chyle, as it circulates in the chyliferous vessels, has only been submitted to examination in comparatively recent times, and — as will be seen hereafter—it varies in different parts of its course. The best mode of obtaining it is to feed an animal, and, when digestion is in full progress, to strangle it, or divide the spi- nal marrow beneath the occiput. The thorax must then be opened, through its whole length ; and a ligature be passed round the aorta, oesophagus, and thoracic duct, as near the neck as possible. If the ribs ofthe left side be now turned back or broken, the thora- cic duct is observed, lying against the oesophagus. By detaching the upper part, and cutting into it, the chyle flows out. A small quantity only is thus obtained ; but, if the intestinal canal and chyliferous vessels be repeatedly pressed upon, the flow may be sometimes kept up for a quarter of an hour. It is obviously im- possible, in this way, to obtain the chyle pure ; inasmuch as the lymphatics, from various parts ofthe body, are constantly pouring their fluid into the thoracic duct. From the concurrent testimony of various experimenters, chyle is a liquid of a milky-white appearance ; limpid and transparent in herbivorous animals, but opaque in the carnivorous-, neither viscid nor glutinous to the touch; of a consistence, varying somewhat according to the nature of the food ; of a spermatic smell; sweet taste, not dependent on that of the food; neither acid nor alkaline; and of a specific gravity, greater than that of distilled water, but less than that of the blood. Magendie,b Tiedemann and Gmelin,c and Muller,d however, state it to. possess a saline taste ; to be clammy on the tongue ; and sensibly alkaline. The milky colour ofthe chyle is generally supposed to be owing to the oily matter which occurs in it in the form of globules of various sizes, from „iVBth to ^o^ of an inch in diameter, and which are more abundant in the chyle of man and of the carni- vora, than in that of the herbivora. Mr. Gulliver"8 has, however, • See a history of these discoveries, by Dr. Meigs, in Philadelphia Journal, No. 2, New Series; and Kurt Sprengel, Hist, de la Medecine, traduit par Jourdan, iv 201, _ . iqi- rrecis, &c. n. 17.4. cDie Verdauung nach Versuchen, i. 353, Heidelb. 1826 ; or French translation, VSSe^of Physiology, by Baly, p. 258, Lond. 1838. e GerbeS General Anatomy"by Gulliver, Appendix, p. 88, Lond. 1842. 600 ABSORPTION. recently affirmed that the colour is due to an immense multitude of minute particles, which he regards as forming the matrix or molecular base of the chyle. These are generally spherical and extremely small — their diameter being estimated at from T^r,ioth to ^oVoth of an inch. The chemical character of the chyle has been examined by bra- mert,a Vauqlielin,b Marcet,c and Prout ;d and is found to resemble greatly that of the blood. In a few minutes after its removal from the thoracic duct, it becomes solid ; and, after a time, separates, like the blood, into two parts, a coagulum, and a liquid. The coagu- lum is an opaque white substance; of a slightly pink hue; insoluble in water; but readily soluble in the alkalies,and alkaline carbonates. Vauquelin regards it as fibrin in an imperfect state, or as interme- diate between that principle and albumen ; but Brandee thinks it more closely allied to the caseous matter of milk than to fibrin. The analyses of Marcet and Prout agree, for the most part, with that of Vauquelin. Dr. Prout has detailed the changes, which the chyle expe- riences in its passage along the chyliferous apparatus. In each successive stage, its resemblance to the blood was found to be increased. Another point, of analogy with the blood is the fact, observed by Bauer/ and subsequently by Prevost and Dumas,e and others, that the chyle, when examined by the microscope, contains globules; differing from those of the blood in their being of a smaller size, the average being 3TrVotn of an inch, and devoid of the envelope of colouring matter. The nature and source of these globules, as well as those of the lymph which resemble them in all respects, is not determined, They have been supposed to be the nuclei or primordial cells from which all the tissues originate.11 Although the chyle has essentially the same constituents, whatever may be the food taken, and separates equally into the clot and the serous portion, the character of the aliment may have an effect upon the relative quantity of those constituents, and thus exert an influence on its composition. That it scarcely ever contains ad- ventitious substances we shall see hereafter; but it is obvious, that if an animal be fed on diet contrary to its nature, the due propor- tion of perfect chyle may not be formed; and that, in the same way, different alimentary articles may be very differently adapted for its formation. Leuret and Lassaigne,'indeed, affirm, that in their experiments they found the chyle to differ more according to the nature of the food than to the animal species; but that, con- a Annales de Chimie, torn. lxxx. p. 81. b Ibid. Ixxxi. 113 ; and Annals of Philosophy, ii. 220. = Med. Chirurg. Transactions, vol. vi. 618, Lond. 1815. a Thomson's Annals of Philosophy, xiii. 121, and 263. '■ e Phil. Transact, for 1812. f Sir E. Home, Op. cit. iii. 25. s Biblioth. Universelle de Geneve, p. 221, Juillet, 1821. h Gulliver, in Gerber's Anatomy, p. 83, note. Hee, also, Carpenter, Human Physi- ology, § 567, Lond. 1842 ; and Mr. Paget, Brit, and For. Med. Rev. July, 1842, p. 262. » Recherches sur la Digestion, Paris, 1825. CHYLE. 601 trary to their expectation, the quantity of fibrin, existing in the chyle, bore no relation to the more or less azoted character of the aliment. They assign it, as constituents, fibrin, albumen, fatty matter, soda, chloride of sodium, and phosphate of lime. The chief object of Marcet's experiments was to compare the chyle from vegetable, with that from animal food, in the same ani- mal. The experiments, made on dogs, led him to the following re- sults. The specific gravity of the serous portion of the chyle is from 1-012 to 1-021, whether it be formed from animal or vegeta- ble diet. Vegetable chyle, when subjected to analysis, furnishes three times more carbon than animal chyle. The latter is highly disposed to become putrid; and this change generally commences in three or four days; whilst vegetable chyle may be kept for seve- ral weeks, and even for months, without becoming putrid.3 Putre- faction attacks rather the coagulum of the chyle than its serous portion. The chyle from animal food is always milky; and, if kept at rest, an unctuous matter separates from it, similar to cream, which swims on the surface. The coagulum is opaque, and has a rosy tint. On the other hand, the chyle from vegetable food is almost always transparent, or nearly so, like ordinary serum. Its coagulum is almost colourless, and resembles an oyster; and its surface is not covered with the substance analogous to cream. Magendie,b too, remarks, that the proportion of the three substances, into which the chyle separates, when left at rest; — namely, the fatty substance on the surface, the clot and the serum, varies greatly, according to the nature of the food; — that the chyle, pro- ceeding from sugar, for example, has very little fibrin; whilst that from flesh has more; and that the fatty matter is extremely abundant when the food contains fat or oil; whilst scarcely any is found if the food contains no oleaginous matter. Lastly, — the attention of Proutc has been directed to the same comparison. He found, on the whole, less difference between the two kinds of chyle than had been noticed by Marcet. In his experiments, the serum of chyle was rendered turbid by heat, and a few flakes of albumen were deposited ; but, when boiled, after admixture with acetic acid, a copious precipitation, ensued. To this substance, which thus differs slightly from albumen, Dr. Prout gave the inex- pressive name of incipient albumen. The following is a compa- rative analysis, by him, of the chyle of two dogs, one of which was fed on animal, and the other on vegetable substances lhe quantity of pure albumen, it will be observed, was much less in the latter case. * Thenard has properly remarked, that the difference in the time of putrefacUon of these two substances, "appears very extraordinary. It is, mdeed, tnex^hcable. Traite de Chimie Elementaire, &c. 5eme edit., Pans, 18.47. ! Sn^ofVhit'sophy^iii. 22, and Bridgewater Treatise, Amer. Edit. p. 272, Philad. 1834. VOL. I- — 51 602 ABSORPTION. Vegetable Food. Animal Food. Water .... . 93-6 89-2 Fibrin .... . 0-6 0-8 Incipient albumen - - - - 4-6 4-7 Albumen, with a red colouring matter - 0-4 4-6 Sugar of milk - a trace Oily matter ... - a trace a trace Saline matters ... 0-8 0-7 100-0 100-0 The difference between the chyle from food of such opposite character, as indicated by these experiments, is insignificant, and indicative of the great uniformity in the action of the agents of this absorption. More recent researches by Messrs. Macaire and Mar- cet,2 tend, indeed, to establish the fact, that both the chyle and the blood of herbivorous and of carnivorous quadrupeds are identical in their composition, in as far, at least, as regards their ultimate analysis. They found the same proportion of azote in the chyle, whatever kind of food the animal habitually consumed ; and this was the case with the blood, whether of the carnivora or herbi- vora; but it contained more azote than the chyle. These results are not so singular, now that we know that the animal and vegetable compounds of protein are almost identical in composition. (See page 503.) All the investigations into the nature of the chyle exhibit the inaccuracy of the view of Roose,b that the chyle and the milk are identical. With regard to the precise quantity of chyle, that may be formed after a meal, we know nothing definite. When digestion is not going on, there can of course be none formed except from the digestion of the secretions from the digestive tube itself; and, after an abstinence of twenty-four hours, the contents of the thoracic duct will be chiefly lymph. During digestion, the quantity of . chyle formed will bear some relation to the quantity of food taken, the nutritive qualities ofthe food, and the digestive powers of the individual. Magendie,0 from an experiment made on a dog, esti- mated, that at least half an ounce of chyle was conveyed into the mass of blood, in that animal/in five minutes ; and the flow was kept up, but much more slowly, as long as the formation of chyle continued.11 3. PHYSIOLOGY OF CHYLOSIS. The facts just referred to — regarding the anatomical arrange- ment of the chyliferous radicles and mesenteric glands, — will suffi- ciently account for the obscurity of our views on many points of chylosis. > Memoir, de la Soci^te de Physique et de l'Histoire Naturelle de Geneve, v. 389. '» Weber's Hildebrandt's Handbuch der Anatomie, i. 102, Braunschweig, 1830. c Op. citat. ii. p. 183. d See, on the character of the chyle, Mr. Ancell, Lectures on the Physiology and Pathology ofthe Blood, in London Lancet, Oct. 26, 1839, p. 150 ; and Mr. Lane, art. Lymphatic and Lacteal System, Cyclop, of Anat. and Phys., April, 1841. CHYLOSIS. 603 The impracticability of detecting the mouths or extremities of the chyliferous radicles has been the source of different hypotheses; and, according as the view of open mouths or of the spongy gela- tinous tissue has been embraced, the chyle has been supposed to enter immediately into the vessels, or to be received through the medium of this tissue ; or, again, to pass through the parietes of the vessels by imbibition. Let it be borne in mind, however, that not only the action of absorption, but the vessels themselves, are seen only by the " mind's eye ;" and that the chyle does not seem to exist any where but in the chyliferous vessels. In the small intestine, we see a chymous mass, possessing all the properties we have described, but containing nothing resembling true chyle ; whilst, in the smallest lacteal, which we can detect, it always pos- sesses the same essential properties. Between this imperceptible portion of the vessel, then, and its commencement — including the latter,—the elaboration must have been effected. Leuret and Lassaigne/ indeed, affirm, that they have detected chyle in the chymous mass within the intestine, by the aid of the microscope. They state that globules appeared in it similar to those that are contained in the chyle, and that their dissemination amongst so many foreign matters alone prevents their union in perceptible fibrils. These globules they regard as true chyle, — for the reason, that they observed similar globules in the artificial digestions they attempted; and, on the other hand, never detected them in the digestive secretions. In their view, consequently, chyliferous ab- sorption would be confined to the separation of the chyle, ready formed in the intestine, from the excrementitious matters united with it. Some caution is, however, necessary regarding the re- corded results of minute microscopic researches, which have fre- quently presented a considerable difference to the observer, owing to glasses of different magnifying powers having been employed. We certainly must have stronger evidence than the above to set aside the overwhelming testimony in favour of an action of selec- tion and elaboration by the absorbents of all organized bodies — vegetable as well as animal. The nutriment of the vegetable may exist in the soil and the air around it; but it is subjected to a vital agency the moment it is laid hold of, and is decomposed to be again united, so as to form the sap. How else can we understand the conversion of animal matters in the soil into the substance of the vegetable ? A like action is doubtless exerted by the chylifer- ous radicles ;b and hence all the modes of explaining this part of the function, under the supposition of their being passive, me- chanical tubes, are inadequate. Boerhaave- affirmed that the peristaltic motion of the intestines has a considerable influence in forcing the chyle into the mouths of the vessels ; whilst Dr. Youngd a Recherche* Physiologiques et Chimiques, pour servir a l'Histoire de la Digestion, P'b6F Arnold8 Lehrbuch der Physiologie des Menschen, Zurich, 1836-7 ; and Brit. and For. Med.Review, Oct. 1839, p. 479. c Prelect. Academ. in prop. Instit. Rei Med. § 103. d Medical Literature, p. 42, Lond. 1813. 604 ABSORPTION. is disposed to ascribe the whole effect to capillary attraction ; and he cites the lachrymal duct as an analogous case, the contents of which, he conceives, — and we think with propriety, — are en- tirely propelled by capillary attraction. The objections to these views, as regards the chyliferous vessels, are sufficiently obvious. The chyle must, according to them, exist in the intestines ; and, if the view of Boerhaave were correct, we ought to be able to obtain it from the chyme by pressure. As the chyle is not present, ready formed, in the intestine, the explana- tions by imbibition and by capillary attraction are equally inad- missible. There is no analogy between the cases of the lachrymal duct and the chyliferous vessels; even if it were admitted, that the latter have open mouths, which is not the case. In another part of this work, (p. 215,) we have affirmed, that the passage of the tears, through the puncta lachrymalia, and along the lachrymal ducts, is one of the few cases in which capillary attraction can, with propriety, be invoked, for the explanation of functions executed by the human frame. In that case there is no conversion of the fluid. It is the same on the conjunctiva as in the lachrymal duct, but, in the case of the chyliferous vessels, a new fluid is formed ; there must, there- fore, have been an action of selection exerted; and this very action would be the means of the entrance of the new fluid into the mouths of the lacteals. If, therefore, we admit, in any manner, the doctrine of capillary tubes, it can only be, when taken in con- junction with that of the elaborating agency. " As far as we are able to judge," says Bostock," " when particles, possessed of the same physical properties, are presented to their mouths (the lac- teals), some are taken up, while others are rejected; and if this be the case, we must conceive, in the first place, that a specific attrac- tion exists between the vessel and the particles, and that a certain vital action must, at the same time, be exercised by the vessel connected with, or depending upon, its contractile power, which may enable the particles to be received within the vessel, after they have been directed towards it. This contractile power may be presumed to consist in an alternation of contraction and relaxa- tion, such as is supposed to belong to all vessels that are intended for the propulsion of fluids, and which the absorbents would seem to possess in an eminent degree." This is all specious: but it is not the less hypothetical. By other physiologists, absorption is presumed to be effected, by virtue of the peculiar sensibility or insensible organic contrac- tility or irritability of the mouths of the absorbents; but these terms, as Magendieb has remarked, are the mere expression of our ignorance, regarding the nature of the phenomenon. The sepa- ration of the chyle is, doubtless, a chemical process ; seeing that there must be both an action of decomposition and of recomposition ; but it is not regulated, apparently, by the same laws as those that govern inorganic chemistry. 1 Physiol., edit. cit. 622, Lond. 1836. b Precis, &c. ii. 179. CHYLOSIS. 605 Recently, Mr. Goodsira has referred this function to the agency of cells. Having fed a dog, with oatmeal, butter, and milk, he ex- amined the intestinal villi three hours afterwards, when the chy- liferous vessels were turgid with chyle, and the intestine was full of milky chyme mingled with a. bilious looking fluid. In the white portion of the fluid, which was situate principally towards the mucous membrane, numerous epithelium cells were found; some of which had evidently — from their form — been detached from the surface of the villi; whilst others had been thrown off from the interior of the follicles of LieberkUhn. The villi were turgid, and destitute of epithelium except at their bases. Each villus was covered by a very fine, smooth membrane, continuous with what Mr. Bowman terms the basement membrane of the mucous surface, which is reflected into the follicles. The villi were semitransparent except at their free or bulbous extremities, where they were white and nearly opaque. The summit of each villus was crowded beneath the enveloping membrane with a number of perfectly spherical vesicles, varying in size from ToVo_m to ^njthofaninch; the matter in the interior of which had an opa- lescent milky appearance. At the part where these vesicles ap- proached the granular texture of the substance of the villus, minute granular or oily particles were situate in great numbers. The trunks of two lacteals could be easily traced up the centre of each villus; and as they approached the vesicular mass, they subdivided and looped ; but in no instance could they be seen to communicate directly with any of the vesicles. These vesicles, in Mr. Goodsir's opinion, can scarcely be considered in any other light than cells, whose lives have but a very brief duration, which select from, and appropriate the materials in contact with the surface of the villi into their own substance, and then liberate these, by solution or disruption of the cell-wall, in a situation where they can be ab- sorbed by the lacteals. When the intestine contains no more chyme, the development of new vesicles ceases ; the lacteals empty themselves, and the villi become flaccid. During the interval of repose, the epithelium is renewed for the protection ofthe surface ofthe villi, and for the secretion function ofthe follicles of Lieber- kUhn. It is considered by Mr. Gpodsir, that the epithelium cells have their origin in certain nuclei, which he has detected scattered through the basement membrane. These views have been embraced by Dr. Carpenter ; but they can scarcely be regarded, at present, as more than suggestions. It has already been said, that the chyle always possesses the same essential properties ; that it may vary slightly according to the food and the digestive powers of the individual; but that it rarely if ever contains any adventitious substance, — the function of the chyliferous vessels being restricted to the formation of chyle. » Edinb. New Philosophical Journal, July, 1842 ; see, also, Dr. Carpenter, British and Foreign Med. Review, Jan, 1843, p. 268. 51* 606 ABSORPTION. The facts and arguments, in favour of this view of the subject, will be given hereafter. The course of the chyle is, as we have described, along the chy- liferous vessels, and through the mesenteric glands into the recep- taculumchyli or commencement of the thoracic duct; along which • it passes into the subclavian vein. The chief causes of its pro- gresssion, are,— first of all, me inappreciable action,by which the chyliferous vessels form and receive the chyle into them. This formation being continuous, the fresh portions must propel those already in the vessels towards the mesenteric glands, in the same way as the ascent of sap in plants, during the spring, appears to depend solely on the constant absorbing action of the roots.a It is probable, too, that the vessels themselves are contractile :b such is the opinion of Sheldon,6 Schneider, and Cruikshank,d and J. Miil- ler ; and Mandle affirms, that it can no longer be doubted ; and that their irritability continues for several hours even after death. Mojonf considers, that when the longitudinal fibres, which he has observed in the lymphatics, contract, they draw one sphincter nearer to another, whilst the oblique fibres diminish the diameter. All these fibres, taking their point d'appui in the circular fibres, dilate the superior sphincters by drawing the circumference down- wards. By this'method, the fluid that enters a lymphatic irritates the vessel, which contracts upon itself, diminishes its cavity, and sends on the fluid through the open sphincter. A kind of peristaltic action, he conceives, exists in the lymphatics similar to that ofthe intestines, which may be observed very distinctly, he says, in the lacteal vessels of the mesentery of animals, if opened two or three hours after they have been well fed. Moreover, that the lacteals and lymphatics are possessed of a power of contraction, is corro- borated by the following reasons. First. They are small; and tonic contractions are generally admitted in all the capillary vessels. Secondly. The ganglions or glands, which cut them at intervals, would destroy the impulse given by the first action of the radicles ; and hence require some contraction in the vessels to transport the chyle from one row of these ganglions to another. Thirdly. If a chyliferous vessel be opened in a living animal, the chyle spirts out, which could not be effected simply by the absorbent action of the chyliferous radicles; and, Fourthly ; in a state of abstinence, these vessels are found empty ; proving, that notwithstanding there has been an interruption to the action of chylous absorption, the whole of the chyle has been propelled into the receptaculum chyli. It is obvious, however, that most of these reasons would apply as well to the elasticity as to the muscularity of the outer coat of these vessels.^ A more forcible argument is derived from an ex- » Breschet, Le Systeme Lymphatique, Paris, 1836. i> Muller's Handbuch, u. s. w. and Baly's translation, i. 284, Lond. 1838. c History ofthe Absorbent System, p. 28, Lond. 1784. d Op. citat. c. 12. e Manuel d'Anatomie generale, p. 211, Paris, 1843. f Journ. de la Societe des Sciences Physiques, &c. Nov. 1833. i Adelon, Physiologie, &c. iii. 31. CHYLOSIS. 607 periment by Lauth.a He killed a dog, towards the termination of digestion ; and immediately opened its abdomen, when he found the intestines marbled, and the chyliferous vessels filled with chyle. Under the stimulation of the air, these vessels began to contract, and, in a few minutes, were no longer perceptible. The result he found to be the same, whenever the dissection was made within twenty-four hours after death ; but, at the end of this time, the irritability of the chyliferous vessels was extinct; and they re- mained distended with chyle, notwithstanding the admission of air. These experiments lead fo a deduction which seems, in the absence of less direct proof, scarcely doubtful; — that the chyli- ferous vessels possess a contractile action, by the aid of which the chyle is propelled along the vessels. In addition to these propel- ling causes, the pulsation of the arteries in the neighbourhood of the chyliferous vessels; and the pressure of the abdominal mus- cles in respiration have been invoked. The former has probably less effect than the laUer. It is not, indeed, easy to see how the former can be possessed of any. Of the agency of the latter we have experimental evidence. If the thoracic duct be exposed in the neck of a living animal, and the course ofthe chyle be observed, it will be found accelerated at the time of inspiration, when the de- pressed diaphragm forces down the viscera ; or when the abdomen of the animal is compressed by the hands. We shall find, too, hereafter, that the mode in which the thoracic duct opens into the subclavian exerts considerable effect on the progress of the chyle in its vessels. We have reason to believe that the course of the chyle is slow. It has been already stated, that in an experiment on a dog, which had eaten animal food at discretion, Magendieb found half an ounce of chyle discharged from an opening in the thoracic duct in five minutes. Still, as he judiciously remarks, the velocity will be partly dependent upon the quantity of chyle formed. If much enters the thoracic duct, it will probably proceed faster than under opposite circumstances. In the commencement of the thoracic duct the chyle becomes mixed with lymph. Under the head of lymphatic absorption we shall show how they proceed together into the subclavian, and the effect produced by the circumstances under which the thoracic duct opens into that venous trunk. It has been a subject of inquiry, whether the chyle varies mate- rially in different parts of its course, and what is the precise modi- fication, impressed upon it by the action ofthe mesenteric glands. The experiments of Reuss, Emmert,0 and others, seem to show, that when taken from the intestinal side of the mesenteric glands, it is of a yellowish-white colour, does not become red on being exposed to the air, and coagulates but imperfectly, depositing only a small, yellowish pellicle. It is said, indeed, that chyle, drawn a Essai sur les Vaisseaux Lymphat. Strasb. 1824. b Precis, &c. ii. 183. c Reil's Archiv. viii. s. 2 ; and Annales de Chimie, lxxx. 81. 608 " ABSORPTION. from the chyliferous vessels that traverse the intestinal walls, con- tains albumen in a state of solution, but no fibrin ; and abounds in oleaginous matter; whilst that obtained from the other side ofthe glands, and near the thoracic duct, is of a reddish colour, contains chyle globules, coagulates entirely, and separates into a clot and m serum. Vauquelin,a too, affirms, that it acquires a rosy tint as it advances in the apparatus; and that the fibrin becomes gradually more abundant. These circumstances have given rise to the be- lief, that the chyle, as it proceeds, becomes more and more animal- ized, or transformed into the nature of the being to be nourished. This effect has generally been ascribed to the mesenteric glands ; and it has been presumed by some to be produced by the exhala- tion of a fluid into their cells, from the numerous bloodvessels with which they are furnished. Others, again, consider that the veins ofthe glands remove from the chyle every thing that is noxious, or purify it. From the circumstance, that the rosy colour of the chyle is more marked on the thoracic, than on the intestinal side ofthe glands; that the fluid is richer in fibrin after having passed through those glands; and that the rosy colour and fibrin are less, when the animal has taken a larger proportion of food, MM. Tiede- mann and Gmelinb infer, that it is to the action of the glands, that the chyle owes those important changes in its nature ; — the fluid, in its passage through them, obtaining, from the blood circulating in them, the new elements, which animalize it. These are the chief views, that have been entertained, regarding the use of the mesenteric glands. They are equally gratuitous with the notion, indulged by some, that they act as so many hearts, for the propulsion ofthe chyle towards the subclavian vein. We are, in truth, totally ignorant of their uses. In another place, the various hypotheses that have been in- dulged, regarding the spleen, will be noticed. It is proper, how- ever, to refer to one, that has been recently proposed by MM. Tiedemann and Gmelin, but which is perhaps little less solid than its precursors. They consider the organ as a dependent ganglion of ihe absorbent system, which prepares a fluid, destined to be mixed with the chyle to effect its animalization. They assert that the chyle hardly coagulates, if at all* before it has passed through the mesenteric glands ; but, after this, fibrin begins to appear, and is much more abundant after the addition of the lymph from the spleen, which contains a very large quantity of fibrin. Before passing the mesenteric glands, the chyle contains no red particles; but it does so immediately afterwards, and more particularly after it is mixed with the lymph from the spleen, which abounds with them, and with fibrin. M. Voisin,c who, as we have seen, con- siders that the chyliferous vessels ramify in the substance of the liver, thinks, that by the action of the liver, a species of punfica- 1 Annales de Chimie, lxxxi. 113; and Annals of Philosophy, ii. 220. b Die Verdauung nach Versuchen, u. s. w., and Jourdan's translat. Paris, 1827. c Nouvel Apercu sur la Physiologie du Foie, &c. Paris, 1833. CHYLOSIS. 609 tion is produced in the chyle, bv which the latter is better fitted to mingle with and form part ofthe blood. The following table by Dr. Carpentera is a modification of one by Gerber, and exhibits concisely the relative proportions of the three main ingredients of the chyle— fat, albumen, and fibrill- in various parts of the absorbent' system ; and affords some idea of its change in the process of assimilation. fFat in maximum quantity (numerous fat or I. In the afferent or peripheral lacteals | oil globules). (from the intestines to the mesen-^ Albumen in minimum quantity (few or no teric glands). | albuminous granules). y_Fibrin almost entirely wanting. II. In the efferent or central lacteals C Fnalin medium quantity (fewer oil globules). (from the mesenteric glands to the J Mbum™ m maximum quantity (numerous thoracic duct). ) ^.f™nules). £ ribrin in medium quantity. CFat in minimum quantity (few or no oil j globules). III. In the thoracic duct. -^ Albumen in medium quantity. | Fibrin in maximum quantity (cytoblasts and l_ lymph corpuscles). Prior to the discovery of the chyliferous vessels, the mesenteric veins were regarded as the agents of chylous absorption; and as these veins terminate in the vena porta?, which is distributed to the liver, this last organ was considered the first organ of sanguifica- tion ; and to impress upon the chyle a first elaboration. In this view, the great size ofthe organ, compared with the small quantity of bile it furnishes, and the exception, which the mesenteric veins and vena porta present to the rest of the venous system, were accounted for, — as well as the large size of the liver in the foetus, although not effecting any biliary secretion, and the fact of its receiving immediately the nutritive fluid from the placenta. This idea of the agency of the mesenteric veins is now nearly ex- ploded, but not altogether so. There are yet physiologists, and of no little eminence, who regard them as participators in the func- tion of chylosis with the chyliferous vessels themselves. Some of the arguments, used by these gentlemen, are : — First. The mesenteric veins form as much an integrant part of the villi of the intestine as the chyliferous vessels; and they have, also, free orifices, in the cavity of the intestine. Lieberkohn,b by throwing an injection into the vena porta, observed the fluid ooze out at the villi of the intestine; and Ribesc obtained the same result by in- jecting spirit of turpentine coloured black. It is manifest, how- ever that these experiments are insufficient to establish the fact of open mouths. Situate, are those vessels are, in an extremely loose tissue which affords them but little support, the slightest injecting force mi"ht be expected to be sufficient to rupture their sides. Secondly. Chyle has often been found in the mesenteric veins. » Human Physiology, § 569, Lond. 1842. b Dissert, de Fabric. Villor. Intestin. Lugd. Bat. 1745. e Memoir, de la Soctete M^dicale d'Emulation, viii. 621. 610 ABSORPTION. Swammerdam asserts, that, having placed a ligature round the mesenteric veins of a living animal, whilst digestion was going on, he saw whitish, chylous striae in the blood of those veins; and Tiedemann and Gmelin affirm, that they have often, in their expe- riments, observed thesame appearance.8 If the fact of the identity of these stria? with chyle were well established, we should have to bend to the weight of evidence. This is not, however, the case. These gentlemen afford us ho other reason for the belief, than the colour of the stria?. The arguments against the mesenteric veins having the power of forming chyle we think irresistible. A sepa- rate apparatus exists, manifestly for this purpose, which scarcely ever contains any thing but chyle; and consequently, it would seem unnecessary, that the mesenteric veins should participate in the function, especially as the fluid, which circulates in them, is most heterogeneous; and, as we shall see, a compound of various adventitious and other absorptions. Granting, however, that these stria? are truly chyle, it would, it is affirmed, by no means, follow absolutely, that it should be formed by the mesenteric veins. It is possible, that a communication may exist between the chyliferous vessels and these veins. Walla?usb asserts, that having placed a ligature on the lymphatic trunks of the intestine, chyle passed into the vena porta?. Rosen, Meckel/ and Lobstein, affirm that by the use of injections they also detected this inosculation. Lippid states, that the chyliferous vessels have numerous anastomoses with the veins, not only in their course along the mesentery before they enter the mesenteric glands; but also in the glands themselves. Tiedemann and Gmelin concur in the existence of this last anas- tomosis, and Leuret and Lassaigne found that a ligature applied round the vena porta? occasioned the reflux of blood into the thoracic duct. A. Meckel, E. H. Weber, Rudolphi and J. Miiller doubt, however, the existence of an actual open communication between the lymphatics and minute veins in the glands. Meckel states, as a reason for his questioning a real communication, that when the seminal duct of the epididymis of the dog is injected, the veins also are filled; and Miillere observes, that when glands are injected from their excretory duct, the small veins of the gland also frequently become filled with the mercury; and the cases in which this occurred»to him were always those in which the ducts had not been well filled, — their acini not distended. Thirdly. That the ligature ofthe thoracic duct has not always induced death, or has not induced it speedily ; and, consequently, that the thoracic duct is not the only route, by which the chyle can pass to be in- * Richerand, Elemens de Physiologie, 13eme edit, par B£rard aine, § xxxvii. p. 90, Bruxelles, 1837. b Medica Omnia, &c. ad Chyli et Sanguinis Circul. Lond. 1660. . c Diss. Epist. ad Haller. de Vasis Lymph. &c. Berol. 1757 ; Nov. Exper. de Finibus Venarum et Vas. Lymph. Berol. 1772; and Manuel d'Anatomie, &c, French edit. by Jourdan, i. 179. d lllustrazioni Fisiologiche e Patologiche del Sistema Limfatico-Chilifefo, Firenze, 1825. * Handbuch, u. s. w.; and Baly's translation, p. 273, Lond. 1838. • OF DRINKS. 6U servient to nutrition. In an experiment of this kind by Duverney, the dog did not die for fifteen days. Flandrin repeated'it on twelve horses, which appeared to eat as usual, and to keep their flesh. On killing them and opening them a fortnight afterwards, he satisfied himself, that the thoracic duct was not double. Sir Astley Cooper likewise performed the experiment on several dogs: the majority lived longer than a fortnight, and none died in the two first days; although, on dissection, the duct was found ruptured and the chyle effused into the abdomen. The experiments of Du- puytren have satisfactorily accounted for these different results. He tied the thoracic duct in several horses. Some died in five of six days, whilst others continued apparently in perfect health. In those, that died in consequence of the ligature, it was impossible to send any injection from the lower part of the duct into jthe sub- clavian vein. It was, therefore, presumable, that the chyle had ceased to be poured into the blood, immediately after the duct was tied. On the other hand, in those, that remained apparently un- affected, it was always easy to send mercurial or other injections from the abdominal portion of the duct into the subclavian. The injections followed the duct until near the ligature; when they turned off, entering large lymphatic vessels, which opened into the subclavian vein, so that, in these cases, the ligature of the thoracic duct had not prevented the chyle from passing into the venous system; and, thus, we can understand why the animals should not have perished.3 From every consideration, then, it appears that the chyliferous vessels are the sole organs concerned in chylosis; and we shall see presently, that they refuse the admission of other substances, which must, consequently, reach the circulation through a different channel.b The recent views of MM. Bouchardat and Sandras — who be- lieve, that the absorption of the nutritive portion of most aliments ' takes place in the stomach, — fatty matters only being absorbed by these vessels, and that they moreover absorb a fluid of an alkaline character destined to neutralize the acidity developed in the sto- mach during digestion, have been given already (page 555). b. Absorption of Drinks. It has been stated, that a wide distinction exists between the' gastric and intestinal operations that are necessary in the case of solid food and liquids. Whilst the former is converted into chyme and passes into the small intestine, to have its chylous part sepa- rated from it; the latter, according to their constitution, may either be wholly absorbed or be divided into two portions —if they be a Rirherand's'Ele'mens de Physiologie, edit. cit. p. 90. b rhan^ier et Adelon, art. Lymphatique, in Diet, des Sciences McSdieales; Adelon, PhvsiolS de l'Homme, 2de edit. iii. 43, Paris, 1829 ; and art. Chyliferes, in Diet. de MTdeSe, 2de edit., Paris, 1832; also, Carpenter, Human Physiology, § 459, Lond. 1842. 612 ABSORPTION. animal or vegetable infusions, — the animal or vegetable substance being subjected to chymification, whilst the watery portion, with its saline accompaniments, — if any such exist, — is absorbed from the stomach or small intestine. The chyliferous vessels, we have seen, are the agents and the exclusive agents of the absorption of the chyle or nutritive product from the digestion of solids : what then, are the agents ofthe ab- sorption of liquids ? There are but two sets of vessels, on which we can rest for a moment. These are the lacteals or lymphatics of the digestive tube ; and the veins of the same canal. But, it has »been seen, the chyliferous vessels refuse the admission into their interior of everything but chyle. It would necessarily follow, then, that the absorption of liquids must be a function of the veins. Such is the conclusion of many distinguished physiologists, and on inferences that are logical. The view is not, however, universally, or perhaps generally, admitted ; some assigning the function ex- clusively to the lacteals ; others sharing it between them and the veins. But let us inquire into the facts and arguments, adduced in support of these different opinions. The advocates for the ex- clusive agency of the chyliferous system affirm, First, That what- ever is the vascular system, which effects the absorption of drinks, it must communicate freely with the cavity of the intestine; and that the chyliferous system does this. Secondly, That this system of vessels is the agent of chylous absorption : — a presumption, that it is also the agent of the absorption of drinks. Thirdly, That every physiologist, who has examined the chyle, has de- scribed its consistence to be in an inverse ratio With the quantity of drink taken ; and, lastly, that when coloured and odorous sub- stances have been conveyed into the intestine, they have been found in the chyliferous vessels and not in the mesenteric veins. The experiments, however, adduced in favour of this last position are so few and inadequate, that it is surprising they could have, for a time, so completely overturned the old theory. This effect . was greatly aided by the zeal and ability of- the Hunters, and of the Windmill Street School in general, who were the chief im- provers of our knowledge regarding the anatomy of the lymphatic system. John Hunter,a — who was one of the first that positively denied absorption by the veins and admitted that ofthe lymphatics, >—instituted the following ingenious and imposing experiment. He opened the abdomen of a living dog ; laid hold of a portion of intestine, and pressed out the matters it contained with the hand. He then injected warm milk into it, which he retained by means of ligatures. The veins, belonging to the portion of intestine, were emptied of their blood by puncturing their trunks; and were pre- vented from receiving fresh blood, by the application of ligatures to the corresponding arteries. The intestine was then returned into the cavity of the abdomen ; and, in the course of half an hour, a Observations on certain parts of the Animal Economy, by John Hunter, F.R.S., with notes by Richard Owen, F.R.S., Bell's Library Edit. p. 307, Philad. 1840. OF DRINKS. 613 was again withdrawn and scrupulously examined ; when the veins were found still empty, whilst the chyliferous vessels were full of a white fluid. Hunter subsequently repeated the experiment with odorous and coloured substances, but without ever being able to detect them in the mesenteric veins. It may be remarked, also, that Musgrave,a Lister,b Blumenbach,6 Seiler and Ficinus assert,d that they have detected substances which had been thrown into the intestines of animals in the chyle of the thoracic duct. The expe- riments of Hunter, however, are those, on which the supporters of this view of the question principally rely. Those physiologists, who believe in absorption of liquids by the mesenteric veins, adduce similar arguments and much more nu- merous experiments. They affirm, that the mesenteric veins, like the chyliferous vessels, have free orifices in the cavity of the intes- tine, and form constituent portions ofthe villi; whilst some of them conceive even this arrangement to be unnecessary, and that the fluids can readily pass through the coats of the vessels; — that if the chyliferous system be manifestly an absorbent apparatus, the same may be said ofthe venous system ; — that if the chyle have appeared to be more fluid after much drink has been taken,'Boer- haave affirms, that he has seen the blood of the mesenteric veins more fluid under like circumstances; and, lastly, against the ex- periments of Hunter, numerous others have been cited, clearly showing, that liquids, injected into the intestine, have been found in the mesenteric veins, whilst they could not be detected in the chyliferous vessels. To the first experiment of Hunter it has been objected ; — that the art of performing physiological experiments was, in his time, imperfect; and that, in order to deduce any useful inferences from it, we ought to know, whether the animal was fasting at the time it was opened, or whether digestion was going on; that the state of the lymphatics ought to have been examined at the commence- ment of the experiment, to see whether they were full of chyle, or empty; as well as the milk, to notice whether any changes had supervened, during its stay in the intestine : lastly, that the reasons should have been assigned for the belief that the lacteals were filled with milk at the end of the experiment, and not with chyle. The experiment, moreover, has been repeated several times by Flandrin, and by Magendie,e — both of them dexterous experi- menters, — yet, in no case, was the milk found in the chyliferous vessels. This first experiment of Hunter cannot, therefore, be looked upon as satisfactory. Some illusion must have occurred, — some source of fallacy, — or, otherwise, a repetition ofthe experi- ment should have been attended with like results. We shall find, hereafter, that in another experiment, by that distinguished indi- vidual, a source of illusion existed, of which he was unaware, a Philosoph. Transact, for 1701, p. 996. b Philosoph. Transact. 1701, p. 819. ' Instit. Physiol. § 422. d Journal Complement, xviii. 327. • Precis, &c, edit, citat. ii. 201. VOL. 1. — 52 614 ABSORPTION. but which was sufficient to account for the appearances he noticed. The experiments of Hunter with the odorous and coloured sub- stances have been likewise repeated by many physiologists, and found to be even less conclusive than that with the milk. Flandrin, who was professor in the Veterinary School at Alfort, in France, thought that, in horses, he could detect an herbaceous odour, in the blood of the mesenteric veins, but not in the chyle. He gave to a horse a mixture of half a pound of honey, and the same quantity of asafoetida; and, whilst the smell of the latter was distinctly per- ceptible in the venous blood ofthe stomach and intestine, no trace of it existed in the arterial blood and chyle. Sir Everard Homea having given the tincture of rhubarb to an animal, around whose thoracic duct he had placed a ligature, found the rhubarb in the bile and in the urine. Magendie gave to dogs, whilst they were digesting, a quantity of alcohol, diluted with water, and solutions of camphor, and other odorous fluids: on examining the chyle, half an hour afterwards, he detected none of those substances, whilst the blood in the mesenteric veins manifestly exhaled the odour,'and afforded the substances by distillation. He gave to a dog four ounces of a decoction of rhubarb ; and, to another, six ounces of a solution of the prussiate of potassa in water. Half an hour afterwards, no trace of these substances was detected in the fluid of the thoracic duct, whilst they were contained in the urine. On another dog, he tied the thoracic duct, and then gave it two ounces of a decoction of nux vomica. Death occurred as speedily as in a dog, in which the thoracic duct was pervious. The result was the same, when the decoction was thrown into the rectum, where no proper chyliferous vessels perhaps exist. Having tied the pylorus in dogs, and conveyed fluids into their stomachs, ab- sorption equally took place, and with the same results. Lastly, with M. Delilleb he performed the following experiment on a dog, which had been made to eat a considerable quantity of meat pre- viously, in order that the chyliferous vessels might be easily per- ceived. An incision was made in the abdominal parietes ; and a portion of the small intestine drawn out, on which two ligatures were applied, at a short distance from each other. The lympha- tics, which arose from this portion of the intestine, were very white, and apparent, from the chyle that distended them. Two ligatures were placed around each of these vessels ; and the ves- sels divided between the ligatures. Every precaution was taken, that the portion ofthe intestine drawn out of the abdomen, should have no connexion with the rest of the body by lymphatic ves- sels. Five mesenteric arteries and veins communicated with this portion ofthe intestine. Four of the arteries and as many veins were tied and cut, in the same manner as the lymphatics. The two extremities of the portion of intestine were now divided, and *■ Lectures on Comparative Anatomy, i. 221, Lond. 1814. b Precis, &c. ii. 203. OF DRINKS. 615 separated entirely from the rest of the small intestine. A por- tion of small intestine, an.inch and a half long, thus remained attached to the body by a mesenteric artery and vein only. These two vessels were separated from each other by a distance of four fingers' breadth ; and the cellular coat was removed to obviate the objection, that lymphatics might still exist in it. Two ounces of a decoction of nux vomica were now injected into this portion of intestine, and a ligature was applied to prevent the exit of the injected liquid. The intestine, surrounded by fine linen, was replaced in the abdomen; and, in six minutes, the effects of the poison were manifested with their ordinary intensity; so that every thing occurred as if the intestine had been in its natural condition. Segalasa performed a similar experiment, leaving the intestine, however, communicating with the rest of the body by chyliferous vessels only. On injecting a solution of half a drachm of the alco- holic extract of nux vomica into the intestine; the poisoning, which, in the experiment of Magendie, took effect in six minutes, had not occurred at the expiration of half an hour; but when one of the veins was untied and the circulation re-established, it supervened immediately. Westrumbb mixed rhubarb, turpentine, indigo, prus- siate of potassa and acetate of lead in the food of rabbits, sheep and dogs. They were detected in the veins of the intestines and in the urine,'but not in the chyle. The same facts were observed by Mayer,0 when rhubarb, saffron, and prussiate of potassa were introduced into the stomach. MM. Tiedemann and Gmelin like- wise observed the absorption of different colouring and odorous substances from the intestinal canal to be effected, exclusively, by the veins. Indigo, madder, rhubarb, cochineal, litmus, alkanet, camboge, and verdigris : musk, camphor, alcohol, spirit of turpen- tine, Dippel's animal oil, asafostida and garlic, the salts of lead, mercury, iron, and baryta, were found in the venous blood, but never in the chyle. The prussiate of potassa and sulphate of potassa were the only substances, which, in their experiments, en- tered the chyliferous vessels. Such are the chief facts and considerations, on which the believers in the chyliferous absorption and in the venous absorption of drinks rest their respective opinions. The strength, we think, is mani- festly with the latter. Let it be borne in mind, that no sufficient experiments have been recently made, which encourage the idea, that any thing is contained in the chyliferous vessels except chyle; and that nearly all are in favour of absorption by the mesenteric veins. An exception to this, as regards the chyliferous and lym- phatic vessels, seems to exist in the case of certain salts. The prussiate and the sulphate of potassa — we have said — were de- tected in the thoracic duct by MM. Tiedemann and Gmelin ; the a Magendie's Journal de Physiologic, torn, ii ; and Precis, &c. ii. 208. b De Phsnomenis, quse ad Vias sic dictas Lotn clandestinas referuntur. Gotting. l8c Ueber das Einsaugungsvermogen der Venen u. s. w. in Meckel's Archiv. Band. iii.; also, C. Windischmann, in art. Einsaugung, of Encycl. Worterb. x. 299, Berlin, 1834. 616 ABSORPTION. sulphate of iron and the prussiate of potassa by Messrs. Harlan, Lawrence and Coatesa of Philadelphia; and the last of these salts by Dr. Macneven of New York. "I triturated," says Dr. Macneven,b "one drachm of crystallized hydrocyanate of potassa with fresh butter and crumbs of bread, which being made into a bolus, the same dog swallowed and retained. Between three and four hours afterwards, Dr. Anderson bled him largely from the jugular vein. A dose of hydrocyanic acid was then administered, of which he died without pain, and the abdomen was laid open. The lacteals and thoracic duct were seen well filled with milk-white chyle. On scratching the receptaculum, and pressing down on the duct, nearly half a tea-spoonful of chyle was collected. Into this were let fall a couple of drops of the solution of permuriate of iron, and a deep blue was the immediate consequence."0 J. Mullerd placed a frog with its posterior extremities in a solution of prussiate of potassa which reached nearly as high as the anus, and kept it so for two hours. He then carefully washed the animal, and, having wiped the legs dry, tested the lymph taken from under the skin with a persalt of iron ; the lymph assumed immediately a bright blue colour, while the colour of the serum of the blood was scarcely perceptibly affected by the test. In a second experiment, in which the frog was kept only one hour in the solution, the salt could not be detected in the lymph. These very exceptions are strikingly corroborative of the rule. Of the various saits employed, these alone appear to have been detected in the chyle of the thoracic duct. It is, therefore, legitimately presumable, that they entered adventitiously,and probably by simple mechanical imbibition; — the mode in which venous absorption seems to be effected. The property of imbibition, possessed by animal tissues, has already been the subject of remark (page 43). It was there shown, that they are not all equally penetrable ; and that different fluids possess different penetrative powers. This view is confirmed by the experiments of Tiedemann and Gmelin on the subject en- gaging us. Although various substances were placed in the same part of the intestinal canal, they were not all detected in the blood of the same vessels. Indigo and rhubarb, for example, were found in the blood of the vena porta?. Camphor, musk, spirit of wine, spirit of turpentine, oil of Dippel, asafoetida, garlic, not in the blood of the intestines, but in that of the spleen and mesentery ; the prus- siates of iron, lead and potassa in that of the veins of. the mesen- tery; those of potassa, iron and baryta in that of the spleen ; the prussiate of potassa, and the sulphates of potassa, iron, lead and baryta in the vena porta? as well as in the urine ; whilst madder and camboge appear to have been found in the latter fluid only. The evidence, in favour of the action of the chyliferous vessels a Philad. Journ. of Med. and Phys. Sciences, vol. ii.; and Harlan's Medical and Physical Researches, p. 458, Philad. 1835. b New York Med. and Phys. Journ. June, 1822. c See, also, Ducachet, in New York Med and Phys. Journal, No. 2, April, 1822. i Handbuch der Physiologie, u. s. w. Baly's translation, p. 279, Lond. 1838. OF DRINKS. 617 being restricted to the absorption of chyle, whilst the intestinal veins take up other matters, is not, however, considered by some to be as decisive as it is by us. Adelon,a for example, concludes, that, as the sectators, on both sides, employ absolutely the same arguments, we are'compelled to admit, that the two vascular sys- tems are under exactly similar conditions ; and that both, conse- quently, participate in the function. We have seen, that whatever may be the similarity of the arguments, the facts are certainly not equal.b It is proper, however, to remark, that all chemical analysts have found great difficulty in detecting inorganic matters when mixed with certain of the compounds of organization; and this may account for substances not having been detected in the tho- racic duct, even when they have been present there. With regard to the mode in which the absorption of fluids is effected, a difference of opinion has existed, chiefly as regards the question, — whether any vital elaboration be concerned, as in the case of the chyle, or whether the fluid, when it attains the interior ofthe vessel, be the same as without. The arguments in favour of these different views will be detailed under the head of venous absorption. We may merely observe, at present, that water, — the chief constituent of all drinks,—is an essential component of every circulating fluid ; that we have no positive evidence, that any action of elaboration is exerted upon it; and that the inge- nious and satisfactory experiments of Prof. J. K. Mitchell,0 have shown, that it penetrates most, if not all, animal tissues better than any other liquid whatever; and, consequently, passes through them to accumulate in any of its own solutions. It is probably in this way, — that is, by imbibition, — that all venous absorptions are effected. But it has been said, if fluids pass so readily through the coats ofthe veins ; — by reason of the extensive mucous surface, with which they come in contact, a large quantity of extraneous and heterogeneous fluid must enter into the abdominal venous system, when we drink freely ; and the composition of the blood be con- sequently modified ; and if it should arrive, in this condition, at the heart, the most serious consequences might result. It has, in- deed, been affirmed by a distinguished member of the profession,41 in this country, in a more ingenious than forcible argument to sup- port a long-cherished hypothesis, that " it must at least be acknow- ledged, that no substance, in its active state, does reach the circu- lation, since it is shown, that a small portion, even of the mildest fluid, as milk or mucilage, oil or pus, cannot -be injected into the bloodvessels without occasioning the most fatal consequences." But the effects are greatly dependent upon the mode in which the injection is made. If a scruple of bile be sent forcibly into the crural vein, the animal will generally perish in a few moments. 1 Physiologie de l'Homme, edit. cit. iii. 111. b Rostock's Physiol. 3d edit. p. 607, Lond. 1836. c American Journal ofthe Medical Sciences, vii. 44, 58. i Chapman, Elements of Therapeutics, 6th edit. p. 47, Philad. 1831. 52* 618 ABSORPTION. The same occurs, if a small quantity of atmospheric air be rapidly introduced into that vessel. The animal, indeed, according to Sir Charles Bella dies in an instant, when a very little air is blown into the veins ; — and there is no suffering nor struggle, nor any stage of transition, so immediately does the stillness of death take possession of every part ofthe frame. In this way, according to Beauchene, Lar- rey, Dupuytren, Warren of Boston, Mott and Stevens of New York, Delpech, and others, operations sometimes prove fatal; — the air beingdrawnin by the divided veins. If, however, the scruple of bile or the same quantity of atmospheric air be injected into one ofthe branches ofthe vena porta?, no apparent inconvenience is sustained. Magendieb concludes, from this fact, that the bile and atmospheric air, in their passage through the myriads of small vessels, into which the vena porta? divides and subdivides in the substance of the liver, become thoroughly mixed with the blood, and thus arrive at the vital organs in a condition to be unproductive of mis- chief. This view is rendered the more probable by the fact, that if the same quantity of bile or of air be injected very slowly into the crural vein, no perceptible inconvenience is sustained. Dr. Blundellc injected five drachms into the femoral vein of a very small dog, with only temporary inconvenience, and subsequently three drachms of expired air, without much temporary disturbance.*1 M. Lepelletiere affirms, that in the amphitheatre of the Ecole Pra- tique of Paris, in the presence of upwards of two hundred stu- dents, he injected thrice into the femoral vein of a dog, of middle size, at a minute's interval, three cubic inches of air, each time, without observing any other effect than struggling, whining, and rapid movements of deglutition, and these symptoms existed only whilst the injection was going on. Since that he has often re- peated the experiment with identical results, — " proving," he observes, "that the deadly action ofthe air is, in this case, mecha- nical, and that it is possible to prevent the fatal effects by injecting so gradually, that the blood has power to disseminate, and perhaps even to dissolve the gas with sufficient promptitude to prevent its accumulation in the cardiac cavities."f As liquids are frequently passed off by the urinary organs soon after they have been taken, it has been believed by some, — either a Animal Mechanics, P. ii, p. 42, Lond. 1829. b Precis Elementaire, 2de edit. ii. 433. c Medico-Chirurg. Trans, for 1818, p. 65. d See, also, Nysten, Recherches de Physiol, et Chimie Pathologique, Paris, 1811. e Physiologie Medicale et Philosophique, i. 494, Paris, 1831. f See Velpeau, Gazette Medicale de Paris, Fev. 24, 1838 ; and Dunglison's Amer. Med. Intelligencer for May 15, and June 1, 1838. In this paper, M. Velpeau examines, critically into the different cases of the introduction of air into the veins during opera- tions, that had occurred up to the time he wrote. See, also, M. Bouillaud's Report on Experiments relative to the Introduction of Air into the Veins, by M. Amussat, in Bull, de 1'Academ. Royale de Medecine, ii. 12 ; and in Brit, and For. Med, Rev. Oct. 1838, pp. 455 and 517; and Dr. C. J. Warren, art. Air, American Cyclopedia of Prac- tical Medicine and Surgery, P. iii. 263, Philad. 1834 ; in Surgical Operations on Tu- mours, p. 259, Boston, 1837; and in Gazette Medicale de Paris, Dec. 30, 1837. LYMPHOSIS. 619 that there are vessels, which forma direct communication between J[Je st(jmach and bladder; or that a transudation takes place through the parietes of the stomach and intestine, and that the fluids proceed through the intermediate cellular tissue to the blad- der. Both these views, we shall hereafter show to be devoid of foundation. In those animals, in which the cutis vera is exposed, or the cuti- cle very thin, nutritive absorption is effected through that envelope. In the polypi, medusae, radiaria, and vermes, absorption is active, and according to Zeder and Rudolphi,a those entozoa, that live in the midst of animal humours, imbibe them through the skin. A few years ago, Jacobsonb instituted experiments on the absorbing power of the helix of the vine (Limacon des vignes). A solution of prussiate of potassa was poured'over the body. This was rapidly absorbed, and entered the mass of blood in such quantity, that the animal acquired a deep blue colour, when sulphate of iron was thrown upon it. In the frog, toad, salamander, &c, the cutaneous absorption is so considerable, that occasionally the weight of water, taken in in this way, is equal to that of the whole body. We shall see, hereafter, that the nutrition of the foetus in utero is mainly, perhaps, accomplished by nutritive absorption effected through the cutaneous envelope. II. ABSORPTION OP LYMPH, OR LYMPHOSIS. This function is effected by agents,which strongly resemble those concerned in the absorption of chyle. One part of the vascular apparatus is, indeed, common to both, — the thoracic duct. We are much less acquainted, however, with the physiology of lym- phatic, than of chyliferous; absorption. 1. ANATOMY OF THE LYMPHATIC APPARATUS. The lymphatic apparatus consists of lymphatic vessels, lympha- tic glands or ganglia, and thoracic duct. The latter, however, does not form the medium of communication between all the lym- phatic vessels and the venous system. 1. Lymphatic vessels. — These vessels exist in almost all parts of the body ; and have the shape of cylindrical, transparent, mem- branous tubes, of small size, and anastomosing freely with each other, so as to present, every where, a reticular arrangement. They are never, according to Miiller, so small as the arterial and venous capillaries, and are almost without exception visible to the naked eye. G. R. Treviranus asserts, that, jheir walls, like the cellular membrane and other tissues, are made up of minute ele- mentary cylinders, of a diameter of about 0-001 millemetres to 0-006, placed in a series side by side and end to end, so as to con- stitute tubes which form networks, and open into larger lympha- a Entozoorum Histor. i. 252, 275. b Tiedemann, Traite Complet de Physiologie de l'Homme, Fr. Edit. p. 242, Paris, 1831. See, also, Jacobson, in Memoir, de l'Acad. des Sciences de Berlin, 1825. 620 ABSORPTION. tic trunks. They are extremely numerous ; more so, however, in some parts than in others. It is not certain that they have yet been found in the brain, spinal marrow, eye, internal ear, &c.; but this is no proof that they do not exist there. It may be merely an evidence that they are so minute as to escape observation. In their progress towards the venous system, they go on forming fewer and fewer trunks; yet they always remain small. This uniformity in size is peculiar to them. When an artery sends off a branch, its size is sensibly diminished ; and when a vein receives a branch, it is enlarged ; but when a lymphatic ramifies, there is, generally, little change of size, whether the branch given off be large or small. The lymphatics consist of two planes, — the one superficial, the other deep-seated. The former creep under the outer covering of the organ, or of the skin, and accompany the subcutaneous veins. The latter are seated more deeply in the interstices of the muscles, or even in the tissue of parts, and accompany the nerves and great vessels. These planes anastomose with each other. This arrangement occurs not only in the limbs, but in the ' trunk, and in every viscus. In the trunk, the superficial plane is seated beneath the skin ; and the deep-seated between the mus- cles and the serous membrane that lines the splanchnic cavities. In the viscera, one plane occupies the surface, the other appears to arise from the parenchyma. The two great trunks of the lymphatic system, in which the lymphatic vessels of the various parts of the body terminate, are the thoracic duct, and the great lymphatic trunk of the right side. The course of the thoracic duct has already been described. It is . formed of three great vessels ; —one, in which all the lymphatics and lacteals ofthe intestines terminate; and the other two, formed by the union of the lymphatics of the lower half of the body. Occasionally, the duct consists of several trunks, which unite into one before reaching the subclavian vein; but more frequently it is double. In addition to the lymphatics ofthe lower half of the body, the thoracic duct receives a great part of those of the thorax, and all those from the left half of the upper part of the body. At its termination in the subclavian, there is a valve, so disposed as to allow the lymph to pass into the blood; and to prevent the reflux ofthe blood into the duct. We shall see, however, that its mode of termination in the venous system possesses other advan- tages. The other trunk is formed by the absorbents from the right side of the hgad and neck, and from the right arm. It is very short, being little more than an inch, and sometimes not a quarter of an inch, in length, but of a diameter nearly as great as the thoracic duct. A valve also exists at the mouth of this trunk, which has a similar arrangement and office with that of the left side. The lymphatics have been asserted to be more numerous than the veins : by some, indeed, the proportion has been estimated at LYMPHOSIS. 621 fourteen superficial lymphatics to one superficial vein ; whence it has been deduced, that the capacity of the lymphatic system is greater than that of the venous. This must, of course, be mere matter of conjecture. The same may be said Of the speculations that have been indulged regarding the mode in which the lym- phatic radicles arise, — whether by open mouths or by some spongy mediate body. The remarks made, regarding the chylous radicles, apply with equal force to the lymphatic. It has been a matter of some interest to determine, whether the lymphatic vessels have not other communications with the venous system than by the. two trunks just described ; or, whether, soon after their origin, they do not open into the neighbouring veins,— an opinion which has been enunciated by many of those who believe in the doctrine of absorption by the lymphatics exclusively, in order to explain why absorbed matters are found in the veins. Many of the older, as well as more modern, anatomists, have professed a similar opinion ; whilst it has been strenuously combated by Som- mering, Rudolphi,a and others. Vieussens affirmed, that, by means of injections,lymphatic vessels were distinctly seen to originate from the minute arteries,and to terminate in the small veins. SirWil- liam Blizardb asserts, that he twice observed lymphatics terminating directly in the iliac veins. Mr. Bracy Clarkec found the trunk ofthe lymphatic system of the horse to have several openings into the lumbar veins. Ribes,d by injecting the supra-hepatic veins, saw the substance of the injection enter the superficial lymphatics of the liver. Alarde considers the lymphatic and venous systems to communicate at their origins. Vincent Fohmann,f that the lym- phatic vessels communicate directly with the veins, not only in the capillaries, but in the interior of the lymphatic glands. Lauths 0f Strasbourg, — who went to Heidelberg to learn from Fohmann his plan of injecting,— announced the same facts in 1824. By this anatomical arrangement, Lauth explains how an injection, sent into the arteries, reaches the lymphatics, without being effused into the cellular tissue ; the injection passing from the arteries into the veins, and thence, by a retrograde route, into the lymphatics. Beclard believed, that this communication exists at least in the interior of the lymphatic glands; and he supported his opinion by the fact, that in birds, in which these glands are wanting, and are replaced by plexuses, the lymphatic vessels in these plexuses are distinctly seen to open into the veins. Lippih has made these communica- tions the express subject of a work. According to him, the most » Grundrissder Phvsiologie, u. s. w. Berlin, 1821. ♦ b Physiological Observations on the Absorbent System of Vessels, Lond. 1787. ' Rees's Cyclopedia, art. Anatomy, Veterinary. d Magendie, Precis, &c. ii. 238. e Du sie<*e et de la nature des maladies, on nouvelles considerations touchant la ve- ritable action du Systeme Absorbant, &c, Paris, 1821. f Ueber die Verbindung der Saugadern mit den Venen, Heidelb. 1S21, und Das Sau«-adersystem der Wirbelthiere, Heft 1, Heidelb. 1824; Mem. sur les communica- tion^ des vaisseaux lyrnphatiques avec les veines, Liege, 1832. g Essai sur les Vaisseaux Lyrnphatiques, Strasbourg, 1824. h Ulustrazioni Fisiologiche, &c, Firenz., 1825. 622 ABSORPTION. numerous exist between the lymphatic vessels of the abdomen and the vena cava inferior and all its branches. So numerous are they, that every vein receives a lymphatic vessel, and the sum of all those vessels would be sufficient to form several thoracic ducts. Opposite the second and third lumbar vertebra?, these lym- phatic vessels are manifestly divided into two orders: — some ascending, and emptying themselves into the thoracic duct; others descending and opening into the renal vessels and pelves of the kidneys. Lippi admits the same arrangement, as regards the chyli- ferous vessels; and he adopts it to explain the promptitude with which drinks are evacuated by the urine. Subsequent researches do not seem to have confirmed the statements of Lippi. G. Rossi,8 indeed, maintains, that the vessels, which Lippi had taken for lym- phatics, were veins. It would appear, however, that when Rossi was at Paris, he was unable to demonstrate, when requested to do so by Breschet, the very things, which he had previously figured and described. Panizza, too, affirms, that no direct union or con- tinuity between the venous capillaries and the lymphatics has ever been made manifest to the eye, either in the human subject or in the lower animals.b On the whole matter, we are perhaps justi- fied in concluding with Panizza, that anatomy has not hitherto succeeded in determining, with physical certainty,in what relation the sanguiferous and lymphatic systems stand to each other, at their extreme ramifications.0 Magendied conceives the most plau- sible view regarding the lymphatics to be:—that they arise by extremely fine roots in the substance of the membranes and cellular tissue, and in the parenchyma of organs, where they appear con- tinuous with the- final arterial ramifications, — as it frequently happens, that an injection, sent into an artery, will pass into the lymphatics ofthe part to which it is distributed. The structure of the lymphatic vessels is the same as that of the lacteals. They have the same number and character of coats, the same crescentic valves or sphincters, occurring in pairs, and giving them the knotted and irregular appearance, for which they are re- markable ; every contraction indicating the presence of a pair of valves, or sphincter. The minutest lymphatics seem, however, to be destitute of valves, but they are discernible in those of less than one-third of a line in diameter, and have the same structure as those ofthe veins. In man, each lymphatic, before reaching the venous system, passes through a lymphatic gland or ganglion ; formerly called a conglobate gland. These organs are extremely numerous; and in shape, structure, and probably in function, entirely resemble the mesenteric glands. They, therefore, do not demand any distinct notice. They exist more particularly in the axilla?, neck, in the neighbourhood of the lower jaw, beneath the a Omodei's Annali Universali, Jan. 1826. b Osservazioni Antropo-zootomico-fisiologiche, Pavia, 1833; and Breschet's Sys- teme Lymphatique, Paris, 1836. c See, on both sides of this subject, Mailer's Handbuch, u. s. w.,Baly's translation, p. 273, Lond. 1838; and Weber's Hildebrandt's Handbuch der Anatomie, iii. 113, Braunschweig, 1831. d Precis, &c. ii. 194. LYMPHATIC APPARATUS. 623 skin ofthe nape of the neck, in the groins, and in the pelvis — in the neighbourhood of the great vessels. The connexion be- tween the lymphatic vessels and those glands is exactly analo- gous to that between the chyliferous vessels and the mesenteric glands. Chaussier includes, in the lymphatic system, certain organs, whose uses in the economy are not manifest, — the thymus gland, the thyroid gland, the supra-renal capsules, and perhaps the spleen. These he considers as varieties of the same species, under the name glandiform ganglions. The thymus gland is a body consisting of distinct lobesj"situate at the upper and anterior part of the thorax, behind the ster- num. It belongs more particularly to fcetal existence,and will be investigated hereafter. The thyroid gland is, also, a lobular organ, situate at the anterior part ofthe neck be- neath the skin and some subcutaneous mus- cles, and resting upon the anterior and infe- rior part of the larynx, and the first rings of the trachea. It is formed of lobes, which subdivide into lobulesand granula; has a red andsometimesayellowcolour;and presents, internally,cells or vesicles, filled with a fluid, which is viscid and colourless,or yellowish. Collected on the point of a knife (after in- cising the gland) it. appears like weak gum, and isalmost devoid of theropiness of white of egg. When put into common rectified spirit it seems only to lose a little water; becomes solid, but not opaque, and decreases but little. The same effects result in the cells when the gland is boiled for a quarter of an hour,and no apparent solution occurs. The thyroid gland has no excretory duct; and, consequently, it is difficult to discover its use. It is larger in the fostus than in the adult, and has, therefore, been supposed to be, in some way, inservient to foetal exist- ence. It continues, however, through life,3 receives large arteries, as well as a number of nerves and lymphatics, and hence, it has been supposed, fills some important office through the whole of existence. This, however, is all conjecture. Mr. Kingb has affirmed, what had been already ima- IT^^^TX^^ gined by many, that the absorbent vessels » Krause, in Muller's Archiv. fiir Anat. u. s. w., Heft i. 1837; and Brit, and For Med. Rev. July, 1838, p. 218. b Guy's Hospital Reports, i. 437, Lond. 1836, and Sir Astley Cooper, ibid. p. 448. Lymphatics. a, a, a, a. Lymphatic vessels proceeding towards the thoracic duct, b, b. Lymphatic glands. 624 ABSORPTION. 3 of the thyroid gland convey its peculiar, secretion to the great veins of the body. The thyroid gland is the seat of goitre or 1 bronchocele, the swelled neck, Derbyshire neck, papas, &c, as it has been termed in different quarters ofthe globe,—a singular affection, which is common at the base of lofty mountains in all parts of the world ; and, in the cure of which, we have a valuable remedy in iodine. The sorbefacient property of this drug is particularly ex- erted on the thyroid gland and on the mamma?; and it affords us an additional instance, to the many already known, of remedial agents, not only exerting their properties upon a particular system, but even upon a small part of such system, without our being able, in the slightest degree, to account for the preference. The iodine stimulates the absorbent vessels of the gland to augmented action ; and the consequence is, the absorption of the morbid de- posit. Lastly, the supra-renal or atrabiliary capsules or glands, are small bodies in the abdomen, without the peritoneum, and above each kidney. The arteries distributed to them are large ; and the glands themselves are larger in the foetus than in the adult. They, likewise, remain during life. These bodies consist of small sacs, with thick parenchymatous parietes: they are lobular and granular,—the internal cavity being filled with a viscid fluid pulp or oil, according to Sir Everard Home1 which is reddish in the foetus, yellow in childhood, and brown in old age. Under the microscope, the pulp is found to consist of minute oil-like sphericles, of very unequal size, varying from-^^th to 57^m °f an 'ncn in diameter.5 With their uses we are totally unacquainted. By the ancients, they were believed to be the secretory organs of the imaginary atrabilis; and hence their name. Sir Everard Home considers that they act like a filter, " by which any oil left in the » arterial branches that are near the kidneys may be separated and prevented from making its escape by the tuba? urinifera? of these glands." Dr. Carpenter0 thinks the only use that can be assigned them with any thing like probability, is that of serving as a means of conveying into the veins the blood sent through the renal artery, when from any cause the secreting function of the kidneys is partly or wholly checked, and their capillary circulation stagnates in con- sequence. 2. LYMPH. Lymph may be procured in two ways, either by opening a lym- phatic vessel, and collecting the fluid that issues from it, — but this is an uncertain method, — or by making an animal fast four or five days, and then obtaining the fluid from the thoracic duct. This has been considered pure lymph; but it is obvious that it must be mixed with the product of the digestion of the different secretions from the part of the digestive tube above the origin of the chylifer- ous vessels. Chyle itself is nothing more than the lymph of the a Lect. on Comp. Anat. v. 262, Lond. 1828. b Gulliver, in Gerber's General Anatomy, p. 103. c Human Physiology, § 710, Lond. 1842. LYMPH. 625. intestines, containing matter absorbed from the digested food.3 The fluid, thus obtained, is of a rosy, slightly opaline tint; of a marked spermatic smell, and saline taste. At times, it is of a de- cidedly yellowish colour; and, at others, of a madder red ; circum- stances which may have given occasion to erroneous inferences, in experiments made on the absorption of colouring matters. Its specific gravity has been found by some to be 1022-28: by others l-037.b Its colour is affirmed to be more rosy, in proportion to the length of time the animal has fasted. When examined by the microscope, it exhibits globules or corpuscles like those of the chyle ;c and, like the chyle, bears considerable analogy, in its che- mical composition, to the blood.d Bodies similar to these lymph corpuscles are seen mingled with the blood, occupying generally the space between the main current of the blood and the parietes of the vessel. Some, however, regard them as blood corpuscles in process of solution or disintegration ; and Mandle thinks they do not exist in the fluid during life, but are owing to the coagulation of the fibrin. More recently, he has stated, that from experiments made with M. Bres- chet, it was evidently impracticable to procure pure lymph by opening the lymphatic hearts of frogs. Blood globules always existed in it; and this, he thinks, throws doubts on the view, that lymph corpuscles are transformed into blood corpuscles/ When left at rest, lymph separates into two portions ; — the one a liquid, nearly like the serum of the blood ; and the other a co- agulum or clot of a deeper rosy hue; in which is a multitude of reddish filaments, disposed in an arborescent manner ; and, in ap- pearance, very analogous to the vessels, which are distributed in the tissue of the organs. When a portion of coagulated lymph is examined, it seems to consist of two parts ; — the one which is solid, formed of numerous cells, containing the other or more liquid part; and if the solid portion be separated, the latter coagulates. Mr. Branded collected the lymph from the thoracic duct of an ani- mal, which had been kept without food for twenty-four hours. He found its chief constituent to be-water; besides which, it con- tained chloride of sodium and albumen; — the latter being in such minute quantity, that it coagulated only by the action of galva- nism. The lymph of a dog yielded to Chevreul, water, 926-4; fibrin, 4-2; albumen, 61-0; chloride of sodium, 6-1; carbonate of soda, 1*8 ; phosphate of lime, phosphate of magnesia, and carbo- nate of lime, 0-5 : that of the horse yielded to Lassaigne, water, 192-5; fibrin, 0-33 ; albumen, 5-73 ; "and chlorides of sodium and a Muller's Handbuch u. s. w., Baly's translation, P. i. p. 258, Lond. 1838. b R. T. Marchand and C. Colberg, Muller's Archiv. fur Anatomie, No. 2,1838 ; and Brit, and For. Med. Rev. Oct. 1838, p. 544. c See Mr. Paget, Brit, and For. Med. Rev. July, 1842, p. 262. See, also, Carpenter, Human Physiology, § 567, Lond. 1842. d Miiller, op. cit. p. 259. e Anatom. Microscop. I. 15. f Mandl, Manuel d'Anatomie generate, p. 297, Paris, 1843. s Turner's Chemistry, 4th Amer. Edit. p. 567. VOL. I.-- 53 626 ABSORPTION. potassium, with soda and phosphate of lime, 1-43. Total, 100. MM. Marchand and Colberga found its constituents to be,— water, 96-926 ; fibrin, 0-520; albumen, 9-534 ; osmazome (and loss), 0-312; fatty oil and crystalline fat, 0-264 ; chloride of sodium, chloride of potassium, carbonate and lactate of an alkali, and sul- phate of lime, phosphate of lime, and oxide of iron, 1-544. Total, 100-000 ; and more recently a comparative analysis of the chyle and the lymph of the ass has been made by Dr. G. 0. Rees. The fluids were obtained from the chyliferous and lymphatic ves- sels previous to their entrance into the thoracic duct, seven hours after a full meal. Water - - - - - Albuminous matter .... Fibrinous matter - Animal extractive matter, soluble in water and in alcohol Animal extractive matter, soluble in water only Fatty matter ..... Salts: — alkaline chloride, sulphate and carbonate, with traces of alkaline phosphate and oxide of iron 100 000 100000 The chyle — it will be observed — contains a larger proportion of decidedly organizable matters.b Still more recently,0 Dr. Rees examined the contents of the thoracic duct of a human subject procured an hour and a quarter after death by hanging. They amounted to six drachms, and yielded the following results: Water ........ 90-48 Albumen, with traces of fibrinous matter .... 7-08 Aqueous extractive (zomodine) ..... 056 Alcoholic extractive (osmazome) ..... 0-52 Alkaline chloride, carbonate and sulphate ,with traces of phosphate, and ~) ~.. oxide of iron 5 Fatty matters ....... 0-92 Chyle. Lymph. 90-237 96-536 3-516 1200 0-370 0-120 0332 0-240 1-233 1-319 3-601 a trace, 0-711 0-585 100- It is impossible to estimate the quantity of lymph contained in the body. It would seem, however, that, notwithstanding the great capacity of the lymphatic vessels, there is, under ordinary circumstances, but little fluid circulating in them. Frequeutly, when examined, they have appeared to be empty, or pervaded by a mere thread of lymph. Magendied endeavoured to obtain the whole of the lymph from a dog of large stature. He could collect but an ounce and a half; and it appeared to him that the quantity increased whenever the animal was kept fasting ; but on this point he does not seem to express himself positively. 3. PHYSIOLOGY OF LYMPHOSIS. The term lymphosis has been proposed by Chaussier for the action of elaboration by which lymph is formed, as chylosis has 1 Op. cit. b Carpenter, Human Physiology, § 464, Lond. 1842. c Proceedings ofthe Royal Society, Feb. 10, 1842; and Brit, and For. Med. Rev. ,Oct. 1842, p. 573. <» Op. citat. ii. 192. LYMPHOSIS. 627 been used, for the formation of chyle; and hasmatosis,fox that ofthe blood. In describing the organs, concerned in this function, the striking similarity— we might almost say — identity, in structure and arrangement between them and the chyliferous organs will have been apparent. A part, indeed, of the vascular apparatus is common to both ; and they manifestly constitute one and the same system. This would be sufficient to induce us to assign them similar functions; and it would require powerful and positive testimony to establish an opposite view. At one period, the lymph was considered to be simply the watery portion of the blood; and the lymphatic vessels were regarded as the mere continuation of the ultimate arterial ramifications. It was affirmed, that the blood, on reaching the final arterial branches, separated into two parts; the red and thicker portion returning to the heart by the veins; and the white, serous portion passing by the lymphatics. The reasons for this belief were, the great resemblance between the lymph and serum of the blood; and the facility with which an injection passes, in the dead body, from the arterial, into the lym- phatic capillary vessels. Magendie has revived the ancient doc- trine ; and, of consequence, no longer considers the lymphatics to form part, ofthe absorbent system ; but to belong to the circulatory apparatus, and to serve, as we shall see, the office of waste pipes, in case of emergency. Without canvassing this subject now, we may assume it for granted, that the lymph, which circulates in the lymphatic vessels, is identical in its nature, or as little subject to alteration as the chyle ; and that, consequently, whatever may be the materials, that constitute it, an action of elaboration and selec- tion must be exerted in its formation. It has been conceived that many of the tissues of the body, the serous membranes, for example, do not receive red blood ; and that they must consequently be nourished by white blood. The lympha- tics, in such case, have been considered to be to the white arteries what the veins are to the red. This at least has been presumed to be one of their offices,3- but it will be seen, hereafter, that all the tis- sues supplied with vessels probably receive red blood ; and hence it is unnecessary to suppose, that the lymphatics execute any venous function. Assuming, for the present, that the lymph is wholly obtained from materials already deposited in the body; the next inquiry is ;__into the mode in which their separation and simultaneous absorption are effected. On this topic, we have no additional argu- ments to employ to those adduced regarding the function of the chyliferous radicles. In every respect, they are identically situate ; and to their history we refer for an exposition of how little we know of this part of lymphosis. The causes of the progression of the lymph in the vessels are the » T)r S Jackson, Principles of Medicine, 389, Philad. 1832; Dr. Graves, Lect. on ,' T,/mr,'hatic Svstem ; and Dr. Stokes, Lectures on the Theory and Practice of P?yK 7u^«* Amer. Med, Libr. Edit. p. 313, Philad. 1837. 628 ABSORPTION. same as those that influence the chyle. In addition, however, to those mentioned under chyliferous absorption, there is one which applies equally to the chyliferous and lymphatic vessels arising from the mode in which the tho- racic duct enters the subclavian vein. It has been already ob- served that this occurs at the point of junction between the ju- gular and sub- clavian, as at D, Fig. 144, where J represents the jugular, and V S, the subcla- vian, in which the blood flows from V towards S, the cardiac extremity. Now, it is a physical fact, that when a small tube is inserted perpendicularly into the lower side of a horizontal conical pipe, in which the water is flowing from the narrower to the wider por- tion ; and if the small vertical tube be made to dip into a vessel of water, not only will the water of the larger pipe not descend into the vessel; but it will actually draw up the water through the small tube so as to empty the vessel.3- Instead of supposing the canals.in Fig. 144, to be veins and the thoracic duct; let us presume that they are rigid mechanical tubes; and that the extre- mity of the tube D, which represents the thoracic duct, dips into the vessel B. As the fluids, proceeding from J to S and from V to S are passing from the narrower portions of conical tubes to wider, it follows, that the fluid will be drawn out of the vessel B, simply by traction, or, by what Venturi1' terms, the lateral com- munication of fluids. This would happen in whatever partof the vessel the tube B D terminated. But its insertion at D has another advantage. By the mode in which the current, from J towards S, unites with that from V towards S, a certain degree of diminished pressure must exist at D ; so that the atmospheric pressure, on the surface of the water in the vessel B, will likewise be exerted in propelling it forwards. In the progress, then, of the chyle and lymph, along the thoracic duct, not only may the attrac- tion of the more forcible stream along the veins draw the fluid in » SirC. Bell, in Animal Mechanics, p. 41, Library of Useful Knowledge, Lond. 1829. b Sur la Communication Laterale du Mouvement dans les Fluides, Paris, 1798. Fig. 144. LYMPHOSIS. 629 the thoracic duct along with it, but, owing to the diminished pres- sure at the mouth of the duct, atmospheric pressure may have s°me — although probably but little — influence, in forcing the chyle and lymph from the chyliferous and lymphatic radicles on- wards. The lymphatic glands have been looked upon as small hearts for the propulsion ofthe lymph; and Malpighi accounts for the greater number in the groin in this way ; — the lymph having to ascend to the thoracic duct against its own gravity : this ap- pears, also, to have been somewhat the opinion of Bichat. There seems, however, to be nothing in their structure which should lead to this belief; and, if not muscular or contractile, it is manifest, that their number must have the effect of retarding rather than of accelerating the flow of the lymph. The most prevalent sentiment is, that they are somehow concerned in the admixture of the lymph; and by many it is conceived, that some kind of elaboration is ef- fected by them; but, on this topic, we have only conjectures for our guidance. Of their true functions we know nothing definite. On the subject ofthe moving powers ofthe lymph, Adelona has remarked, that if we admit the lymph to be the serous portion of the blood, and that the lymphatics are vessels of return, as the veins are, the heart might be considered to have the same influence over lymphatic, that it has been presumed to have over venous, circula- tion ; and whether we admit this or not, as the thoracic duct opens into the subclavian vein, the influence ofthe suction power ofthe organ on the venous blood may affect the progression of the chyle also. It canuot, however, as Mullerb remarks, be the primary cause of the motion of the chyle, for Autenrieth, Tiedemann, and Cams observed, that when a ligature was applied to the thoracic duct, the part of the duct below the ligature became distended even to bursting. We shall see hereafter, that during inspiration, absorp- tion, it is imagined, may be facilitated by the dilatation of the chest, and cause great diminution of pressure on the heart and great vessels. Professor Miiller0 discovered, that the frog, and several other amphibious animals are provided with large receptacles for the lymph, situate immediately under the skin, and exhibiting distinct and regular pulsations, like the heart. The use of these lymphatic hearts appears to be to propel the lymph along the lymphatics. In the frog, four of these organs have been found; two posterior situ- ate behind the joint of the hip, and two anterior on each side of the transverse process of the third vertebra, and under the posterior extremity of fhe scapula. The pulsations of these lymphatic hearts do not correspond with those of the sanguiferous heart; nor do » Art. Absorption, in Diet, de Medecine, 2de edit. i. 239, Paris, 1832 ; and Physio- logie de l'Homme, edit. cit. iii. 92. b Handbuch, u. s. w.; and Baly's translation, p. 284, Lond. 1838. c Philos. Transact, for 1833, and op. cit. See, also, his observations on the Lym- phatic Hearts of Tortoises, in Muller's Archiv., Heft i. 1840 ; and Brit and For. Med. Review, July, 1840, p. 256. 53* 630 ABSORPTION. those of the right and left sides take place synchronously. They often alternate in an irregular manner. Prof. E. H. Weber has described those lymphatic hearts in a larger species of serpent — the python bivitatus;a and Dr. Joseph J. Allison, of Philadelphia,b a young and zealous observer, who was cut off early in his career, has likewise seen them in the tadpole, the frog, the sauria,ophidiaj and chelonia. His researches led him to conclude: First. That the pulsations ofthe lymphatic organs vary in different specimens (frogs and tadpoles) from 60 or less to 200 per minute. Secondly. That they vary in the same individual so as sometimes to become double in frequency. Thirdly. That the lymphatic pulsations bear no fixed relation to those ofthe pulmonary heart or to respiration, the lymphatic hearts beating — on an average — with greater fre- quency. The course ofthe lymph is by no means rapid. If a lymphatic vessel bedivided,on a living individual, the lymph oozes out slowly, and never with a jet. Cruikshank estimated its velocity along the vessels to be four inches per second or twenty feet per minute ; but it is probably far less rapid. Collard de Martignyc obtained nine grains of lymph, in ten minutes, from the thoracic duel.of a rabbit, which had taken no food for twenty-four hours. Having pressed out the lymph from the principal lymphatic trunk of the neck, in a dog, the vessel filled again in seven minutes: in a second experiment it filled in eight minutes. The data for any correct evaluation of this matter are altogether inadequate, the deranging influence of all such experiments being signal. In man and in living animals, the lymphatics ofthe limbs, head, and neck rarely contain lymph ; their inner surface appearing to be merely lubricated by a very thin fluid. Occasionally, however, the lymph stops in different parts of the vessels; distends them ; and gives them an appearance very like that of varicose veins, except as to colour. Sommering states, that he has seen several in this condition on the top of the foot of a female; and Magendie one around the corona glandis of the male. In dogs, cats and other living animals, lymphatics, filled with lymph, are frequently seen at the surface of the liver, gall-bladder, vena cava, vena porta?, and at the sides of the spine. Magendie remarks, that he has never met with the thoracic duct empty, even when the lymphatics of the rest of the body were entirely so.d It must be recollected, however, that the thoracic duct must always contain the product of the diges- tion either of food or of the secretions from the alimentary tube. This kind of stagnation of lymph in particular vessels has given occasion to the belief, that the lymph flows with different degrees of velocity in the different parts of the system ; and the notion has entered into the pathological views of different writers, who have presumed, that something like determinations of lymph can occur, 1 Miiller, Op. citat. p. 275. b American Journal ofthe Medical Sciences, for August, 1838. c Journal de Physiologie, torn. viii. d Precis, &c, ii. 224. LYMPHOSIS. 631 so as to produce lymphatic swellings. Bordeu,8 indeed, speaks of currents of lymph. All the phenomena of the course of the lymph negative such presumption ; and induce us to believe, that its pro- gress is pretty uniform and always slow ; and when an accumula- tion, or engorgement, or stagnation occurs in any particular vessel, it is more probably owing to increased secretion by the lymphatic radicles, which communicate with the vessel in question, and the consequently augmented quantity of lymph. The lymph, which proceeds by the thoracic duct, is emptied, along with the chyle, into the subclavian vein. A_t the confluence, a valve is placed, which does not, however, appear to be essential, as the duct opens so favourably between the two currents from the jugular and subclavian, that there is no tendency for the blood to reflow into it. It has been suggested, that its use may be, to moderate the instillation of the fluid from the thoracic duct into the venous blood. With regard to the question, whether the lymph be the same at the radicles of the lymphatics as in the thoracic duct, or whether it do not gradually become more and more ani- malized in its course towards the venous system, and especially in its progress through the lymphatic glands, the remarks made upon the subject, as respects the chyle, apply with equal force to the lymph ; and our ignorance is no less profound. The glands of the mesentery, and of the lymphatics in general, seem to be concerned in some of the most serious diseases. Swell- ing ofthe lymphatic glands ofthe groin may indicate the existence of a venereal sore on the penis. A wound on the foot will produce tumefaction ofthe inguinal glands; one on the hand will inflame the glands in the axilla. Whenever, indeed, a lymphatic gland is symptomatically enlarged, the source of irritation will be found at a greater distance from the vein into which the great lymphatic trunks pour their fluid, than the gland is. In plague, one of the essential symptoms is the appearance of swelling of the lymphatic glands of the groin and axilla ; hence, it has been termed by some, adeno-adynamic fever (from *JW, a gland). In scrofula, the lym- phatic system is generally deranged; and, in the doctrine of Brous- sais, a very active sympathy is affirmed to exist between the glands of the mesentery, and the mucous surface of the stomach and in- testines. This discovery, we are told, belongs to the "physiolo- gical doctrine," which has shown, that all gastro-ententes are accompanied by tumefaction of the mesenteric glands: although chyle may be loaded with acrid, irritating, or even poisonous mat- ters, it traverses the glands with impunity, provided it does not inflame the gastro-intestinal mucous surface. "Our attention," Broussaisb adds, " has been for a.long time directed to this ques- tion and we have not observed any instance of mesenteric gan- elionitis which had not been preceded by well-evidenced gastro- enteritis'." The discovery will not immortalize the " doctrine." a CEuvres completes, par Richerand, Paris, 1818. b Traite de Physiologie, &c, and Bell and La Roche's translation, 3d Amer. Edit. p. 362, Philadelphia, 1832. 632 ARSORPTION. We should as naturally look for tumefaction of the mesenteric glands or ganglia, in cases of irritation of the intestine, as for en- largement of the glands of the groin when the foot is irritated. Lastly; the lymph, from whatever source obtained — united with the chyle — is discharged into the venous system. Both these, therefore, go to the composition of the body. They are entirely analogous in properties; but differ materially in quantity ; — the nutritious fluid, formed from materials obtained from without, being by far the most copious. A due supply of it is required for continued existence; yet the body can exist foratime,even when the supply of nutriment is entirely cut off. Under such circumstances, the necessary proportion of nutritive fluid must be obtained from the decomposition of the tissues; but, from the perpetual drain, which takes place through the various excretions, this soon be- comes insufficient, and death is the result.8- We have seen, that both chyle and lymph are poured into the venous blood ; — itself a compound of the remains of arterial blood, and of various heterogeneous absorptions. As an additional pre- liminary to the investigation of the agents of internal absorption, let us now inquire into the nature and course of the fluid contained in the veins; but so far only as to enable us to understand the function of absorption : the other considerations, relating to the blood, appertain to the function of circulation. III. VENOUS ABSORPTION. The apparatus of venous absorption consists of myriads of ves- sels, called veins, which commence in the very textures of the body, by what are called capillary vessels ; and from thence pass to the great central organ of the circulation — the heart ; receiv- ing, in their course, the products of the various absorptions not only effected by themselves, but by the chyliferous and lymphatic vessels. The anatomy of the venous system is given under the head of Circulation. 1. PHYSIOLOGY OP VENOUS ABSORPTION. Whilst the opinion prevailed universally, that the lymphatics are the sole agents of absorption, the fluid, circulating in the veins, was considered to consist entirely ofthe residue of the arte- rial blood, after it had passed through the capillary system, and been subjected to the different nutritive processes there effected. We have already seen, however, that the drinks are absorbed by the mesenteric veins ; and we shall hereafter find, that various other substances enter the venous system by absorption. It is ob- vious, therefore, that the venous blood cannot be simply the residue » See Adelon, Physiologie de l'Homme. edit. cit. iii. 68, Paris, 1829 ; art. Absorption, in Diet de Med. 2de edit. i. 239, Paris, 1832 ; Copland, in Lond. Med. Repos. for Jan. 1825 ; Muller's Handbuch, u. s. w., or Baly's translation, p. 258, Lond. 1838 ; Ancell's Lectures on the Blood, London Lancet, Oct. 26, 1839, p. 150; and Mr. Lane, art. Lymphatic and Lacteal System, Cyclop, of Anat and Physiol. April, 1841. VENOUS. 633 of arterial blood; and we can thus account for the greater capa- city of the venous system than of the arterial. The facts, which were referred to, when considering the absorption of fluids from the intestinal canal,may have been sufficient to show, that the veins are capable of absorbing ; as the odorous and colouring proper- ties of substances were distinctly found in the mesenteric veins. A question arises, whether any vital elaboration is concerned, as in the case of the chyle, or whether the fluid, when it attains the interior of the vessel, is the same as without ? Adelon,3 — who, with many of the German physiologists, believes in both venous and lymphatic absorption, and venous and chyliferous absorption, — conceives, that a vital action takes place at the very mouth of the venous radicles, precisely similar to that which is presumed to be exerted at the mouths of the lymphatic and chyliferous radicles. In his view, consequently, an action of elaboration is exerted upon the fluid, which becomes, in all cases, converted into venous blood at the very moment of absorption, as chyle and lymph are elaborated under similar circumstances. On the other hand, Magendie,b Fodera,c and others maintain, that the substance soaks through the vessel, when possessed of the neces- sary tenuity; that this act of imbibition is purely physical, and consists in the introduction of the absorbed materials through the pores of the veins by capillary attraction. In their view, there- fore, the fluid within the vessel should be the same as that without. In favour of the vital action of the veins we have none of that evidence, which strikes us in regard to the chyliferous and lym- phatic vessels. In these last we invariably find fluids, identical — in all essential respects —in.sensible and chemical characters ; and never containing extraneous matter, if we make abstraction of cer- tain salts, which have been occasionally met with in the thoracic duct. In the veins, on the other hand, the sensible properties of odorous and colouring substances have been apparent. It may, however, be remarked, that the fluid, flowing in the veins, is as identical in composition as the chyle or the lymph. This is true; but it must be recollected, that the greater part of it is the residue of the arterial blood; and that its hue and other sensible proper- ties are such as to disguise any absorbed fluid, not itself possess- ing strong characteristics. The fact, — now indisputable — that various substances, placed outside the veins, have been detected in the blood within, is not only a proof, that the veins absorb ; but that no action of elaboration has been, exerted on the absorbed fluid Of this we have the most convincing proof in some expe- riments by Magendie.d In exhibiting to his class the mode in a Art Absorption in Diet, de Medecine, 2de edit. i. 239, Paris, 1832 ; and Physio- logie de l'Homme, 2de edit. iii. 113, Paris, 1829. T> Precis &c. 2de 6dit. ii. 271. c Recherches Experimentales sur l'Exhalation et l'Absorption, Pans, 1823. d Op. citat. ii. 273. 634 ABSORPTION. which medicines act upon the system, he showed, on a living ani- mal, the effects of introducing a quantity of water,of the tempera- ture of 104° Fah., into the veins. In performing this experiment, it occurred to him to notice what would be the effect produced by artificial plethora on the phenomena of absorption. Having in- jected nearly a quart of water into the veins of a dog of middle size, he placed in the cavity of the pleura a small dose of a sub- stance with the effects of which he was familiar, and was struck with the fact, that these effects did not exhibit themselves for several minutes after the ordinary period. He immediately re- peated the experiment, and with a like result. In several other experiments, the effects appeared at the ordinary time, but were manifestly feebler than they ought to have been from the dose of the substance employed, and were kept up much longer than usual. In another experiment, having introduced as much water as the animal could bear without perishing, — which was about two quarts, — the effects did not occur at all. After having waited nearly half an hour for their development, which generally re- quired only about two minutes, he inferred, that if the distension ofthe bloodvessels was the cause ofthe defect of absorption, pro- vided the distension were removed, absorption ought to take place. He immediately bled the animal largely in the jugular ; and, to his great satisfaction, found the effects manifesting them- selves as the blood flowed. He next tried whether, if the quan- tity of blood were diminished at the commencement of the expe- riment, absorption would be more rapid; and the result was as he anticipated. An animal was bled to the extent of about half a pound ; and the effects, which did not ordinarily occur until after the second minute, appeared before the thirtieth second. As the results of these experiments seemed to show, that absorption is evidently in an inverse ratio to the degree of vascular distension, Magendie inferred, that it is effected physically ; is dependent upon capillary attraction; and that it ought to take place as well after death as during life. To prove this, he instituted the follow- ing experiments. — He took a portion of the external jugular vein of a dog, about an inch long and devoid of branches. Re- moving carefully the surrounding cellular tissue, he attached to each of its extremities a glass tube, by means of which he kept up a current of warm water within it. He then placed the vein in a slightly acid liquor, and carefully collected the fluid of the current. During the first few minutes, it exhibited no change ; but, in five or six minutes, became sensibly acid. This experiment was re- peated on veins taken from the human subject, with the same re- sults ; and not only with veins but with arteries. Similar experi- ments were next made on living animals. He took a young dog, about six weeks old, whose vessels were thin, and, consequently, best adapted for the success of the experiment, and exposed one of its jugular veins. This he dissected entirely from the surround- VENOUS. 635 ing matter, and especially from the cellular tissue and the minute vessels, which ramified upon it, and placed it upon a card, in order that there might be no point of contact between it and the sur- r°^!iinS ?artS* He then let fal1 upon its surface and opposite the middle of the card a thick, watery solution of nux vomica, —a substance, which exerts a powerful action upon dogs. He took care that no particle of the poison touched any thing but the vein and cord, and that the course of the blood, within the vessel, was free. Before the end of three minutes, the effects which he ex- pected, appeared, — at first feebly, but afterwards with so much activity, that he had to prevent fatal results by inflating the lungs. The experiment was repeated on an older animal with the same effects ; except that, as might be expected, they were longer in exhibiting themselves, owing to the greater thickness ofthe parie- tes of the veins. Satisfied, as regarded the veins, he now directed his attention to the arteries ; and with like results. They were, however, slower in appearing than in the case of the veins, owing to the tissue of the arteries being less spongy than that of the veins. It required more than a quarter of an hour for imbibition to be accomplished. In one of the rabbits, which died under the experiment, they had an opportunity of discovering, that the absorption could not have been effected by any small veins, that had escaped dissection. One of the carotids — the subject vessel of the experiment — was taken from the body; and the small quantity of blood, adherent to its inner surface, was found by Magendie, and his friends who as- sisted at the experiment, to possess the extreme bitterness which characterizes the nux vomica. These experiments were sufficient to prove the fact of imbibition .by the large vessels, both in the dead and in the living state. His attention was now directed to the small vessels, which seemed, d priori, favourable to the same ac- tion, from their delicacy of organization. He took the heart of a dog, which had died the day before, and injected, into one of the coronary arteries, water at the temperature of 86° of Fah. The water readily returned by the coronary vein into the right auricle, whence it was allowed to flow into a vessel. Half an ounce of water, slightly acidulated, was now placed in the pericardium. At first, the injected fluid did not exhibit any signs of acidity; but, in five or six minutes, the evidences of it were unequivocal. From these facts, Magendiea draws the too exclusive deduction, that "all bloodvessels, arterial and venous, dead or living, large or small, possess a physical property, capable of perfectly accounting for the principal phenomena of absorption." We shall endeavour to show, that it explains only certain varieties of absorption,— those in which the vessel receives the fluid unmodified — but that it is unable to account for absorptions, in which an action of selec- tion and elaboration is necessary. Mayerb injected prussiate of Preci" &c. ii. 283. b Meckel's Archiv. B. iii., and Windischmann in Encyclop. Worterh. u. s. w. B. x. B. 300, Berlin, 1834. 636 ABSORPTION. potassa into the trachea of different animals through a small aper- ture ; and in from two to five minutes the salt was detected in the blood ofthe left side ofthe heart. Since these experiments were performed, others have been insti- tuted by M. Segalasa and Foderab from which the latter physio- logist attempts to show, that exhalation is simply transudation of substances from the interior of vessels to the exterior; and that absorption is imbibition, ox the passage of fluids from the exterior to the interior. The facts adduced by Fodera in support of his views will be considered under the head of secretion. They chiefly go to show the facility with which substances penetrate the different vascular parietes and other tissues of the body ; an action, which he found to be singularly accelerated by the galvanic influence. Some prussiate of potassa was injected into the cavity of the pleura; and sulphate of iron was introduced into the abdomen of a living animal. Under ordinary circumstances, it requires five or six minutes, before the two substances meet by imbibition through the diaphragm; but the admixture is instantaneous if the diaphragm be subjected to a slight galvanic current. The same fact is ob- served, if one of the liquids be placed in the urinary bladder, and the other in the abdomen ; or the one in the lung, and the other in the cavity of the pleura. It was further found, that, according to the direction of the qurrent, the union took place in one or other cavity. Dr. Bostock,c in commenting on these cases, thinks it must be admitted, that they " go very far to prove that membranes, perhaps even during life, and certainly after death, before their texture is visibly altered, have the power of permitting the transu- dation of certain fluids." That such imbibition occurs during life appears to us indisputably proved. If the clear and decisive ex- periments of Magendie and Fodera did not establish it, the addi- tional testimony, — afforded by Lawrence, Coates and Harlan ; by Dutrochet, Faust, Mitchell, Rogers, Draper, and others,— would command it. By the different rates of penetrativeness of different fluids, and of permeability of different tissues, we can explain, why imbibition may occur in one set of vessels and not in another; and why there may not be the same tendency to transude from the vessel, after the fluid has entered it by imbibition : indeed, the constant current, established in the interior of the vessel, would be a sufficient reply to this suggestion.*1 Adelon,e again, affirms, that we ought, under the view of imbibition, to find imbibed sub- stances in the arteries and lymphatics, also. A sufficient objection to this would be, — the comparative tardiness, with which the for- mer admit of the action ; and the selection, and consequently, re- fusal, exerted by the latter ; but even here we occasionally find » Magendie's Journal de Physiol, ii. 217. b Recherches Experiment, sur l'Absorption, &c, Paris, 1824, and Magendie's Jour- nal, &c. iii. 35. ° Physiology, edit. cit. p. 629. <• Bostock, ibid. p. 615. e Physiologie de l'Homme, torn. iii. VENOUS. 637 evidences of adventitious imbibition; as in the case of salts, which— we have seen — have been detected in the thoracic duct, when introduced into the cavity of the abdomen. The two following experiments by Prof. J. K. Mitchell,3 which are analogous to numerous others, performed in the investigation of this subject, ratify the fact of imbibition in the living tissues: — a quantity of a solution of acetate of lead was thrown into the peri- toneal cavity of a young cat; and sulphuretted hydrogen was passed, at the same time, into the rectum. In four minutes, the poisonous gas killed the animal. Instantly on its death, the peri- toneal coat of the intestines, and the parietes of the cavity in con- tact with them, were found lined with a metallic precipitate, which adhered to the surface, and was removable by nitric acid, moder- ately diluted. It was the characteristic precipitate of sulphuretted hydrogen, when acting on lead. In another experiment on a cat, a solution of acetate of lead was placed in the thorax, and sulphu- retted hydrogen in the abdomen. Almost immediately after the entrance of the sulphuretted hydrogen into the abdominal cavity, death ensued. On inspecting the thoracic side of the diaphragm, which was done as quickly as possible, the tendinous part of it exhibited the leaden appearance of the precipitate by sulphuretted hydrogen. The experiment of J. Miiller, referred to in a preced- ing page (p. 616), exhibits the same fact. It may be concluded, then, that all living tissues imbibe the liquid matters which come in contact with them; and that the same occurs to solid matters, provided they are soluble in the humours, and especially in the serum of the blood. But although imbibition is doubtless effected by living tissues, too great a dispo- sition has been manifested to refer all the vital phenomena of ab- sorption and exhalation to it.b Even dead animal membrane has been supposed to exert a positive agency in respect to bodies placed on either side of it. In the early part of this work (p. 43), we referred to the phenomena of imbibition, and explained how endosmose and exosmose,or,in other words, imbibition and transu- dation are effected through organic membranes by virtue of their porosity ; and a careful examination of those phenomena would lead us to the belief that the membrane exerts no agency except in the manner suggested by Dutrochet. This is signally mani- fested in experiments with porous, inorganic substances ; and it has been ingeniously and ably shown by Dr. Draper,0 of Hampden Sidney College, Virginia, who found that all the phenomena were elicited, when, instead of an organic tissue, figured glass was employed. Sir David Barry,d — in different memoirs laid before the Aca- ■ American Journal ofthe Medical Sciences, vii. 44, Philad. 1830. i> Muller's Handbuch der Physiologie, u. s. w., or Baly's translation, p. 248 and 282. c See his various papers in Amer. Journ. of the Med. Sciences, for Aug. 1836, p. 276; Nov. 1837, p. 122; May, 1838, p. 23, and August, 1838 — more especially the two last. d Experimental Researches on the Influence of Atmospheric Pressure upon the Cir- culation, &c. Lond. 1826. VOL. I. — 54 638 ABSORPTION. demie Royale de Medecine, the Acadimie Royale des Sciences of Paris, and the Medico-Chirurgical Society of London, — has main- tained that the whole function of external absorption is a physical effect of atmospheric pressure ; and " that the circulation in the absorbing vessels and in the great veins depends upon this same cause in all animals possessing the power of contracting and di- lating a cavity around that point to which the centripetal current of their circulation is directed." In other words, it is the opinion of this gentleman, that, at the time of inspiration, a tendency to a vacuum is produced in the chest by its expansion ; and as the atmospheric pressure externally thus ceases to be counterbalanced, the pressure without occasions the flow of blood towards the heart along the veins. The consideration of the forces that propel the blood will afford us an opportunity of saying a few words on this view ; at present, we shall only observe, that he ascribes absorp- tion,— which he explicitly states to be, in his opinion, extra vital, — to the same cause. In proof of this, he instituted numerous experiments, in which the absorption of poisons from wounds ap- peared to take place or to be suspended according as the wounds continued, as he conceived, exposed to atmospheric pressure, or were freed from its influence by the application of a cupping-glass. The same quantity of poison, which, under ordinary circumstances, destroyed an animal in a few seconds, was rendered completely innocuous by the exhausted vessel; and what is singular, even when the symptoms had commenced, the application of the cup- ping-glass had the effect of speedily and completely removing them ; — a fact of essential importance in its therapeutical rela- tions. In commenting on the conclusions of Sir D. Barry, Messrs. Addison and Morgan,3— who maintain the doctrine, that all poi- sonous agents produce their specific effects upon the brain, and general system, through the sentient extremities of nerves, and through the sentient extremities of nerves only; and that, when introduced into the current of the circulation in any way, their effects result from the impression made upon the sensible structure of the bloodvessels, and no.t from their direct application to the brain itself, — contend, that the soft parts of the body, when covered by an exhausted cupping-glass, must necessarily from the pressure of the edges of the glass be deprived, for a time, of all connexion, both nervous and vascular, with the surrounding parts; — that the nerves must be partially or altogether paralysed by compression of their trunks, and that, from the same cause, all cir- culation through the veins and arteries situate within the area of the glass must cease; that the rarefaction of the air within the glass being still farther increased by means of the small pump attached to it, the fluids, in the divided extremities of the vessels, are forced into the vacuum, and, with these fluids, either a part or the whole ofthe poison, which had been introduced; and that, in such a condition of parts, the compression, on the one hand, and 1 An Essay on the Operation of Poisonous Agents upon the Living Body, Lond. 1829. INTERNAL. 639 the removal ofthe poison from the wound on the other,will suffi- ciently explain the result of the experiment, either according to the views of those who conceive the impression to be made on the nerves of the bloodvessel, or of those who conceive that the agent must be carried along with the fluid of the circulation to the part ' to be impressed. Such would seem to be the main facts, regarding the absorbent action of the veins, which rests on as strong evidence as we possess regarding any ofthe functions ofthe body ; yet, in the treatise on Animal and Vegetable Physiology, by Dr. Roget,* we find it passed by without a comment! We have still to inquire into the agents of internal, and adven- titious absorption. IV. INTERNAL ABSORPTION. On this point but few remarks will be necessary, after the. ex- position of the different vascular actions concerned in absorption. The term comprehends interstitial absorption, and the absorption of recrementitial, and of excrementitial fluids. The first com- prises the agency, by which the different textures of the body are decomposed and conveyed into the mass of blood. It will be con- sidered more at length under the head of Nutrition ; the second, that of the various fluids, effused into cavities; and the third, that which is effected on the excretions in their reservoirs or excretory ducts. All these must be effected by one of the two sets of vessels, previously described ; the lymphatics, or veins, or both. Now we have attempted to show, that an action of selection and elabora- tion is exerted by lymphatic vessels ; whilst we have no evidence of such action in the case of the veins. It would follow, then, that all those varieties of internal absorption, in which the sub- stance, when received into the vessel, possesses different characters from those it had when without, must be executed by lymphatics ; whilst those, in which no conversion occurs, take place by the veins. In the constant absorption, and corresponding deposition, which is incessantly going on in the body, the solid parts must be reduced to their elements, and a new compound be formed ; inas- much as we never find bone, muscle, cartilage, membrane, &c, existing in these states in any of the absorbed fluids; and it is probable, therefore, that, at the radicles of the lymphatic vessels, they are all converted into the same fluid — the lymph —in like manner as the heterogeneous substances, existing in the intestinal canal, afford to the lacteals the elements of a fluid, the character of which is always identical. On the other hand, when the recre- mentitial fluid consists simply of the serum ofthe blood, more or less diluted, there can be no obstacle to the passage of its aqueous portion immediately through the coats of the veins by imbibition, whilst the more solid part is taken up by the lymphatic vessels. In the case of the excrementitious fluids, there is reason to believe^ a Bridgewater Treatise, Lond. 1834, Amer. Edit. Philad. 1836. 640 ABSORPTION. that absorption simply removes some of their aqueous portions, and this, it is obvious, can be effected directly by the veins, through imbibition. The facts, connected with the absorption of substances from the interior of the intestine, have clearly shown, that the chy- liferous vessels alone absorb chyle, and that the drinks and adven- titious substances pass into the mesenteric veins. These apply, « however, to external absorption only; but similar experiments and arguments have been brought forward by the supporters of the two opinions, with regard to substances placed on the perito- neal surface of the intestine, and other parts of the body. Whilst some affirm, that they have entered the lymphatics ; others have only been able to discover them in the veins. John Hunter, hav-, ing injected water, coloured with indigo, into the peritoneal cavity of animals, saw the lymphatics, a short time afterwards, filled with a liquid of a blue colour. In animals, which had died of pulmonary or abdominal hemorrhage, Mascagni found the lym- phatics of the lungs and peritoneum filled with blood; and he asserts, that, having kept his feet for some hours in water,swelling of the inguinal glands supervened, with transudation of a fluid through the gland ; coryza, &c. Desgenettes observed the lym- phatics ofthe liver containing a bitte'r, and those ofthe kidneys a urinous, lymph. Sommering detected bile in the lymphatics of the liver ; and milk in those of the axilla.* Dupuytren relates a case, which Magendie conceives to be much more favourable to the doctrine of absorption by the lymphatic vessels than any of the others. A female, who had an enormous tumour at the upper and inner part of the thigh, with fluctuation, died at the Hotel-Dieu, of Paris, in 1810. A few days before her death, inflammation occurred in the subcutaneous cellular tissue, at the inner part of the tumour. The day after dissolution, Dupuytren opened the body. On dividing the integuments, he noticed white points on the lips of the incision. Surprised at the appearance, he carefully dissected away some of the skin, and observed the subcutaneous cellular tissue overrun by whitish lines, some of which were as large as a crow's quill. These were evidently lymphatics, filled with puriform matter. The glands of the groin, with which these lymphatics communicated, were injected with the same matter. The lymphatics were full ofthe fluid, as far as the lumbar glands ; but neither these glands nor the thoracic duct presented any trace of it.b On the other hand, multiplied experiments have been in- stituted, by throwing coloured and odorous substances into the great cavities of the body ; and these have been found always in the veins, and never in the lymphatics. To the experiments of Hunter, objections have been urged, similar to those adduced against his experiments to prove the ab- a See Weber's Hildebrandt's Handbuch der Anatomie, iii. 123 ; and Muller's Hand- buch der Physiologie, u. s. w., Baly's translation, p. 277, Lond. 1838. b Magendie, Precis, &c. 2de edit. ii. 195, etseq,; and Adelon, art. Absorption, Diet. de Med. 2de e"dit. i. 239, and Physiologie de l'Hoinme, 2de edit. iii. 65, Paris, 1829. INTERNAL. 641 sorption of milk by the lacteals; and some sources of fallacy have been pointed out. The blue colour, which the lymphatics seemed to him to possess, and which was ascribed to the absorption of in- digo, was noticed in the experiments of Messrs. Harlan, Lawrence, and Coates ;a but they discovered that this was an optical illusion. What they saw was the faint blue, which transparent substances assume, when placed over dark cavities. Mr. Mayob has also affirmed that the chyliferous lymphatics always assume a bluish tint a short time after death, even when the animal has not taken indigo. The cases of purulent matter, &c, found in the lympha- tics, may be accounted for by the morbid action having produced disorganization of the vessel, so that the fluid could enter the lym- phatics directly ; and, if once within, its progression can be readily understood. Magendie15 asserts, that Dupuytren and himself performed more than one hundred and fifty experiments, in which they submitted to the absorbent action of serous membranes a number of different fluids, and never found any of them within the lymphatic vessels. The substances, thus introduced into the serous cavities, produced their effects more promptly, in proportion to the rapidity with which they are capable of being absorbed. Opium exerted its narcotic influence, wine produced intoxication, &c, and Magendie found, from numerous experiments, that the ligature of the tho- racic duct in no respect diminished the promptitude with which these effects appeared. The partisans of lymphatic absorption, however, affirm that even if these substances are met with in the veins, it by no means follows that absorption has been effected by that order of vessels ; for, as we have seen, the lymphatics, they assert, have frequent communications with the veins ; and, conse- quently, they may still absorb and convey their products into the venous system. In reply to this, it may be urged, that all the vessels — arterial, venous, and lymphatic — appear to have com- munication with each other ; but that there is no reason to believe, that the distinct offices, performed by them, are, under ordinary circumstances, interfered with; and, again, where would be the necessity for these intermediate lymphatic vessels, seeing that im- bibition is so readily effected by the veins? The axiom—quod fieri potest per pauca, non debet fieri per multa — is here strik- ingly appropriate. The lymphatics, too, as we have endeavoured to show, exert an action of selection and elaboration on the sub- stances exposed to their agency ; but, in the case of venous ab- sorption, we have not the slightest evidence that any such selection exists — odorous and coloured substances retaining, within the vessel', the properties they had without. Lastly, where would be the use of the distinct, lymphatic circulation opening into the tho- racic duct seeing that the absorbed matters might enter the various venous trunks directly through these supposititious, communicating ! Harlan's Physical Researches, p. 459, Philad. 1835. b Outlines of Human Physiology, 3d edit., Lond. 1833. « Op. cit. ii. 211. 54* 642 ABSORPTION. lymphatics; and ought we not occasionally to be able to detect in the lymphatic trunks at least some evidence of those substances, which their fellows are supposed to take up and convey into the veins ? These carrier lymphatics have obviously been devised to support the tottering fabric of exclusive lymphatic absorption ; undermined, as it has been, by the powerful facts and reasonings that have been adduced in favour of absorption by the veins. From the whole of the preceding history of absorption, we are of opinion, that the chyliferous and lymphatic vessels form only chyle and lymph, refusing all other substances, with the exception of saline matters, which enter probably by imbibition ;a that the veins admit every liquid, which possesses the necessary tenuity; and that, whilst all the absorptions, which require the substances, acted upon, to be decomposed and transformed, are effected by the chyliferous and lymphatic vessels ; those that are sufficiently thin, and demand no alteration, are accomplished directly through the coats of the veins by imbibition ; and we shall see, that such is the case with several of the transudations or exhalations.b V. ACCIDENTAL ABSORPTION. The experiments, to which reference has been made, have shown, that many substances, adventitiously introduced into various cavi- ties, or placed in contact with different tissues, have been rapidly absorbed into the blood, without experiencing any transformation. Within certain limits, the external envelope of the body admits of this function ; but by no means to the same extent as its prolonga- tion, which lines the different excretory canals. The absorption of drinks is sufficient evidence of the activity of the function, as regards the gastro-intestinal mucous membrane. The same may be said of the pulmonary mucous membrane. Through it, the oxygen and azote pass to reach the blood in the lungs, as well as the carbonic acid in its way outwards. Aromatic substances, such as spirit of turpentine, breathed for some time, are detected in the urine, proving that their aroma has been absorbed; and it is by ab- sorption that contagious miasmata probably produce their pestifer- ous agency. Dr. Madden,c however, thinks that the lungs do not absorb watery vapour with the rapidity, or to the extent that has been imagined ; whilst Dr. A. Combe'1 hazards the hypothesis, that owing apparently to the extensive absorption of aqueous vapour by the lungs, the inhabitants of marshy and humid districts, as the Dutch, are remarkable for the predominance of the lymphatic system. Not only do the tissues, as we have seen, suffer imbibition by '» Muller's Handbuch, u. s. w., Baly's translation, p. 278, Lond. 1838. b Dr. Handyside, in Dublin Journ. of Med. and Chem. Science, for Sept. 1835 ; and Amer. Journal for May, 1836, p. 192. c Experimental Inquiry into the Physiology of Cutaneous Absorption, &c, by W. H. Madden, M.D., p. 64, Edinb. 1838. d Principles of Physiology applied to the Preservation of Health, 5th edit. p. 72, Edinb. 1836. CUTANEOUS. 643 fluids, but by gases also: the experiments of Chaussier,and Mitchell astonish us by the rapidity and singularity ofthe passage of gases through the various tissues ; — the rapidity varying according to the permeability ofthe tissue, and the penetrative power of the gas. a. Cutaneous Absorption. On the subject of cutaneous absorption, much difference of opinion has prevailed ; some asserting it to be possible to such an extent, that life may be preserved, for a time, by nourishing baths. It has also been repeatedly affirmed, that rain has calmed the thirst of shipwrecked mariners who have been, for some time, deprived of wate*r.a It is obvious, from what we know of absorption, that, iu the first of these "cases, the water only could be absorbed ; and even the possibility of this has been denied by many. Under ordi- nary circumstances, it can happen to a trifling extent only, if at all; but, in these extraordinary cases, where the system has been long devoid of its usual supplies of moisture, and where we have reason to believe that the energy of absorption is increased, such imbibi- tion may be possible. Sanctorius,b Von Gorter,c Keill,d Mascagni,e Madden/ R. L. Youngs Dill,h and others believe, that this kind of absorption is not only frequent but easy. It has been affirmed, that after bathing the weight ofthe body has been manifestly augmented; and the last of these individuals has adduced many facts and argu- ments to support the position. Strong testimony has been adduced in favour of extensive absorption of moisture from the atmosphere. This is probably effected, however, rather through the pulmonary mucous surface than through the skin. A case of ovarian dropsy is referred to by Dr. Madden,* in which the patient, during eighteen days, drank 692 ounces of fluid; and discharged by urine and paracentesis 1298 ounces, being an excess of 606 ounces of fluid egesta over the fluid ingesta. Bishop Watson, in his chemical essays, states, that a lad at New Market, having been almost starved, in order that he might be reduced to proper weight for riding a match, was weighed at 9, and again at 10 a.m., when he was found to have gained nearly 30 ounces in weight in the interval, although he had only taken" half a glass of wine. Dr. Carpenter gives a parallel case, which was related to him by Sir G. Hill, Governor of St. Vincent. A jockey had been for some time in training for a race in which Sir G. Hill was much interested, and had beDen reduced to the proper weight. On the morning of the race suffering much from thirst, he took one cup of tea, and shortly afterwards his weight was found to have increased six pounds, so that he was incapacitated for riding. These cases certainly appear • Madden, ibid. p. 46 ; and Carpenter, Human Physiology, § 461, Lond. 1842 b Tie Static Medic. Lugd. Bat. 1711. - De Perspirat. Insensib. Lugd. Bat. 1736. • Kntamin Medico-Physic, Lond. 1718. . Vas. Lymph at. Hist. Senis, 1783. lentamin.meuioo 3 g De Cutis Inhalatione, Edinb. 1813. h Fd'inb Medico-Chir.Transact, ii. 350. See, also, Collard de Martigny, in Archives finales de Medecine, x. 304, and xi. 73 ; and Lebkiichner, translated in Archives „ , ,' •• ac,a ' Op.cit. p. 55. Generates, vii. 424. v r 644 ABSORPTION. difficult of belief: yet the authority is good. Dr. Carpenter pre- sumes, that nearly the whole of the increase in Bishop Watson's case; and at least three-fourths of it in the last case must be attri- buted to cutaneous absorption, which was probably stimulated by the wine that was taken in the one case, and by the tea in the other.a Bichat was under the impression, that, in this way, he imbibed the tainted air of the dissecting-room, in which he passed a large portion of his time. To avoid an objection, that might be urged against this idea, — that the miasmata might have been ab- sorbed by the air-passages, he so contrived his experiment, as, by means of a long tube, to breathe the fresh outer air, and he found, that the evidence, which consisted in the alvine evacuations having the smell of the miasmata of the dissecting room, still continued. It is obvious, however, that such an experiment would hardly admit of satisfactory execution, and it is even doubtful, whether there were any actual relation between the assigned effect and the cause. The testimony of Andral, Boyer, Dumeril, Dupuytren, Serres, Lallemand, Ribes, Lawrence, Parent-Duchatelet, and that afforded by our own observation, are by no means favourable to the unwholesomeness of cadaveric exhalations.b J. Bradner Stuartc found, after bathing in infusions of madder, rhubarb, and turmeric, that the urine was tinged with these sub- stances. A garlic plaster affected the breath, when every care was taken, by breathing through a tube connected with the exte- rior of the apartment, that the odour should not be received into the lungs. Dr. Thomas Sewalld found the urine coloured, after bathing the feet in infusion of madder, and the hands in infusions of madder and rhubarb. Dr. Musseye proved, that if the body be immersed in a decoction of madder, the substance may be de- tected in the urine, by using the appropriate alkaline test. Dr. Barton found, that frogs, confined in dry glass vessels, became enfeebled, diminished in size, and unable to leap; but that, on the introduction of a small quantity of water, they soon ac- quired their wonted vigour, became plump, and as lively as usual in their motions/ "Dr. W. F. Edwards*? of Paris, is, also, in favour of absorption being carried on by the skin to a considera- ble extent, To deny cutaneous absorption altogether is impossible. It is a way, in fact, by which we introduce one of our most active reme- a Carpenter, Human Physiology, § 462, Lond. 1842. See, also, on this subject, Dr. Watson, Lond. Med. Gaz. June 10,1842 ; and Prout, on the Nature and Treatment of Stomach and Renal Diseases, 4th edit. p. 120, Lond. 1843. b See, on this subject, Parent-Duchatelet, Hvgiene Publique, Paris, 1836; and the remarks of the author in his Elements of Hygiene, p. 108, Philad. 1835 ; and in his American Medical Intelligencer, p. 161, Philad. 1838. ■= New York Med. Repos. vol. i. and iii. 1810-11. & Med. and Physical Journ. xxxi. 80, Lond. 1814. e Philad. Medical and Physical Journal, i. 288, Philad. 1808. f Klapp's Inaugural Essay on Cuticular Absorption, p. 30, Philad. 1805. e Sur i'lnfluence des Agens Physiques; or Drs. Hodgkin and Fisher's translat. p. 61, and 187, &c. Lond. 1832. CUTANEOUS. 645 dial agents into the system,— and it has not unfrequently hap- pened, where due caution has not been used, that the noxious effects of different mineral and other poisons have been developed by their application to the surface, but it is by no means common or easy, when the cuticle is sound, unless the substance employed possesses unusually penetrating properties. Chaussier found, that to kill an animal, it is sufficient to make sulphuretted hydro- gen gas act on the surface of the body, taking care that none gets into the air-passages: the researches of Prof. J. K. Mitchella have also shown that this gas is powerfully penetrant. Unless, how- ever, the substances, in contact with the epidermis, are of such a nature as to attack its chemical composition, there is usually no extensive absorption. It is only of comparatively late years, that physiologists have ventured to deny, that the water of a bath, or the moisture from a damp atmosphere, is taken up under ordinary circumstances ; and if, in such cases, the body appear to have increased in weight, it is affirmed, and with some appearance of truth, that this is owing to diminution of the cutaneous transpiration. It is, indeed, probable, that one great use of the epidermis is to prevent the inconveniences to which we should necessarily be liable, were such absorption easy. This is confirmed by the fact, that if the skin be deprived ofthe epidermis, and the vessels which creep on the outer surface of the true skin, be thus exposed, absorption occurs as rapidly as elsewhere. Miillerb affirms, that saline solu- tions applied to the corium penetrate the capillaries in a second of time. To insure this result in inoculation and vaccination, the matter is always placed beneath the cuticle; and, indeed, the small vessels are generally slightly wounded, so that the virus gets imme- diately into the venous blood. Yet, it is proper to remark, that the lizard, whose skin is scaly, after having lost weight by expo- sure to the air, recovers its weight and plumpness when placed in contact with water; and if the scaly skin of the lizard permits such absorption, Dr. Edwards thinks it impossible not to attribute this property to the cuticle of man. When the epidermis is re- moved, and the system is affected by substances placed in contact with the true skin, we have the endermic method of medication. Seguin0 instituted a series of experiments to demonstrate the ab- sorbent or non-absorbent action ofthe skin. His conclusion was, that water is not absorbed, and that the epidermis is a natural ob- stacle to that action. To discover whether this were the case as reo-arded other fluids, he experimented on some individuals labour- in^- under venereal affections. These persons immersed their feet and legs in a bath, composed of sixteen pints of water and three drachms of corrosive sublimate, for an hour or two, twice a day. - » Amer. Journal ofthe Med. Sciences, vii. 44 ; and p. 46 of this work. b Handbuch der Physiologie, torn, i., and British and Foreign Medical Review, for April, 1838, p. 344. e Fourcroy, La Medecine Eclairee, die, torn, in.; and Annales de Chimie,xc. 185, 646 ABSORPTION. Thirteen, subjected to the treatment for twenty-eight days, gave no signs of absorption ; the fourteenth was manifestly affected, but he had itchy excoriations on the legs; and the same was the case with two others. As a general rule, absorption exhibited itself in those only whose epidermis was not in a state of integrity. At the temperature of 74° Fahrenheit, however, the sublimate was occasionally absorbed, but never the water. From other experi- ments, it appeared evident, that the most irritating substances, and those most disposed to combine with the epidermis, were partly absorbed, whilst others were apparently not. Having weighed a drachm, (seventy-two grains,poids de marc,) of calomel, and the same quantity of camboge, scammony, salt of alembroth and tartar emetic, Seguin placed an individual on his back, washed the skin ofthe abdomen carefully, and applied to it these substances, at some distance from each other, covering each with a watch-glass, and maintaining the whole in situ, by a linen roller. The heat of the room was kept at 65°. Seguin remained with the patient, in order that the substances should not be displaced : and he protracted the experiment to ten hours and a quarter. The glasses were then removed, and the substances carefully collected and weighed. The calomel was reduced to 71| grains. The scammony weighed 71|; the camboge, 71; the salt of alembroth, 62 grains,a and the tartar emetic, 67 grains.b It requires, then, in order that mat- ters shall be absorbed by the skin, that they shall be kept in con- tact with it, so as to penetrate its pores, or the channels by which the cutaneous transpiration exudes; or else that they shall be forced through the cuticle by friction, — the iatraleptic mode. In this way, the substance comes in contact with the cutaneous veins, and enters them probably by imbibition. Certain it is, that mercury has been detected in the venous blood by Drs. Colson, Christison,Cantu, Autenrieth, Zeller, Schubarth, and others.0 Not long after the period that Seguin was engaged in his experi- ments, Dr. Rousseau,d of Philadelphia, contested the existence of absorption through the epidermis, and attempted to show, in oppo- sition to the experiments we have detailed, that the pulmonary organs, and not the skin, are the passages by which certain sub- stances enter the system. By cutting off all communication with the lungs, whi*h he effected by breathing through a tube commu- nicating with the atmosphere on the oufside of the chamber, he found, that although the surface of the body was bathed with the juice of garlic, or the spirit of turpentine, none of the qualities of these fluids could be detected, either in the urine, or in the serum of the blood. From subsequent experiments, performed by Dr. * Several pimples were excited on the part to which it was applied. b Magendie's Precis, &c, ii. 262. c See the author's General Therapeutics and Materia Medica, vol. i., Philad. 1843 • and Weber's Hildebrandt's Handbuch der Anatomie, i. 100, Braunschweig, 1830. •' * Experimental Dissert, on Absorption, Philad. 1800. ACCIDENTAL. 647 Rousseau, assisted by Dr. Samuel B. Smith,8 and many of which Professor Chapmanb witnessed, the following results were deduced. First, That of all the substances employed, madder and rhubarb are those only that affect the urine, — the latter of the two more readily entering the system ; and secondly, that the power of ab- sorption is limited to a very small portion of the surface of the body. The only parts, indeed, that seemed to possess it, were the spaces between the middle ofthe thigh and hip, and between the middle of the arm and shoulder. Topical bathing, with a decoction of rhubarb or madder, and poultices of these substances applied to the back, abdomen, sides, or shoulders, produced no change in the urine ; nor did immersion of the feet and hands, for several hours, in a bath of the same materials, afford the slightest proof of absorption. From these and other facts, sufficiently discrepant it is true, we are justified in concluding that cuticular absorption, under ordinary circumstances, is not easy, but we can readily conceive, from the facility with which water soaks through animal tissues, that if the animal body be immersed sufficiently long in it, and especially if the vessels have been previously drained, imbibition might take place to a considerable extent. This, however, would be a physical absorption, and might be effected as well in the dead as the living body. b. Other Accidental Absorptions. Amongst the adventitious absorptions have been classed all those that are exerted upon substances retained in the excretory ducts, or situate in parts not natural to them. The bile, arrested in one of the biliary ducts, affords us, in jaundice, a familiar ex- ample of such absorption, and ofthe positive existence ofthe bile in the bloodvessels ; although the yellow colour has been supposed, by some, to be caused by an altered condition of the red globules and not by the presence of bile in the bloodvessels. This condi- tion of the red globules will account for some of the symptoms, — as the yellow colour of the skin, and of the urine, — but it does not explain the clayey appearance, which the evacuations present, and which, we think, has been properly ascribed to the absence of the biliary secretion. We have, likewise, examples of this kind of absorption, where blood is effused into the cellular membrane, as in the case of a common sprain, or in those accumulations of fluid in various cavities, which are found to disappear by time ; — the serous portion being taken at first, with some of the colouring matter, and, ultimately, the fibrin. In the case of an accumula- tion of the serous fluid, which naturally lubricates cavities, it is precisely of such a character — the aqueous portion at least — as to be imbibed with facility, and probably passes into the veins, in * Philad Medical Museum, i. 34, Philad. 1811; and Prof. S. Jackson, art. Absorp- Hon Amer Cvclop. Pract. Med. i. 114, Philad. 1833. "'Elements of Therapeutics and Materia Medica, 6th edit. i. 65, Philad. 1831. 648 ABSORPTION. this manner ; — the functions of exhalation and absorption consist- ing, here, mainly of transudation and imbibition. But absorption is not confined to these fluids. It must, of course, be exerted on all morbid deposits; and it is to excite the action of the absorbents, that our remedial means are directed ; the agents, belonging to this class, being termed sorbefacients. This absorp- tion — in the case of solids — is of the interstitial kind ; and, as the morbid formation has probably to be reduced to its elements, and undergo an action of elaboration, it ought to be referred to lymphatic agency. To conclude the function of absorption. All the products, — whether the absorption may have been chyliferous, lymphatic or venous, — are united in the venous system, and form part of the venous blood. This fluid must, consequently, be variable in its composition, in proportion to the quantity of heterogeneous mate- rials taken up by the veins, and the activity ofthe chyliferous and lymphatic absorptions. It is also clear, that, between the parts of the venous system into which the supra-hepatic veins, — loaded with the products of the intestinal absorption of fluids, — enter, and the opening of the thoracic duct into the subclavian, the blood must differ materially from that which flows in other parts of the system. All, however, undergo admixture in their passage through the heart; and all are converted into arterial blood by the function, which will next engage us, — that of Respiration. End OP VOL. 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