I 4P '*s MH /> 3 Extractive and peculiar matter - - . T Water j 100 —The character of this substance differs somewhat at the dif- ferent stages of life; it is of a thin aqueous consistence and of a reddish colour in the infant; of the consistence and presenting after death somewhat the appearance of butter in the central cavities of the bones, and of a red semi-fluid appearance in the spongy tissue of the bones of the adult; in old age it has some- thing of a rancid smell, and is of a deep yellow colour. The adeps of the bones was supposed at one time to contribute to CARTILAGES AND THEIR STRUCTURE. oc the flexibility, tenacity, and nourishment of the bones, but it is now generally believed to be deposited upon the same principles, as fat in other parts of the body when nutritive matter is supera- bundantly elaborated by the digestive organs, and is held in re- version, as an aliment for the future wants of the economy, during temporary inanition from sickness or other causes. —The deposit of fat in bones is not universal among animals. In birds the^^tral cavity of the long bones, is filled only with air which is introduced into them from the lungs, and serves greatly to diminish their specific gravity, and facilitate their evolutions in the atmosphere. —It is found in great quantity in the bones of the head of the physeter macrocephalus, or sperm whale, far out of the proportion required, if its object only was that of nourishing the bones. —Its purpose in this animal, besides being a deposit of aliment in reserve, is believed to be that of buoying up its head to ena- ble it to respire with greater freedom.— Cartilages and their Structure. Cartilages are white elastic substances, much softer than bones, in consequence of a smaller quantity of earth entering into their composition. Their structure is not so evidently fibrous as that of bones; yet by long maceration, or by tearing them asunder, a fibrous dis- position is perceptible. In articular cartilages their fibres are parallel to each other, and directed towards the cavities of the respective joints. Their vessels are extremely small, though they can be readily injected in cartilages where bone is beginning to form. The vessels of the cartilages of the joints, however, seem entirely to exclude the red blood; no anatomists having yet been able to inject them. They have no cancelli, nor internal membranes, for lodging marrow; no nerves can be traced into them; nor do they possess any sensibility in the sound state. Upon their surface, there is a thin membrane termed peri- chondrium, which in cartilages supplying the place of bone, as in those of the ribs or at the ends of long bones in children, is a 36 CARTILAGES AND THEIR STRUCTURE. continuation of the periosteum, and serves the same general pur- poses to cartilage as this does to bone. Upon the surface of articular cartilages, the perichondrium is a reflection of the inner surface of the capsular ligament, and is so very thin, and adheres so closely, as to appear like part of the cartilage itself.* One set of cartilages supplies the place of bone, and by their flexibility admit of a certain degree of motion, j^jjje their elasti- city recovers their natural position, as in the nose, larynx, carti- lages of the ribs, &c. Another set, in children, supplies the place of bone, until bone can be formed, and affords a nidus for the osseous fibres to shoot in, as in the long bones of children. A third set, and that the most extensive, by the smoothness and lubrication of their surface, allow the bones to move readily, without any abrasion, as in the cartilages of the joints. A fourth set supplies the office both of cartilage and ligament, giving the elasticity of the former and the flexibility of the latter, as in the bones of the spine and pelvis. —Next to the bones, the cartilages form the hardest tissue in the body. On first inspection they do not appear to present any sort of internal organization. They appear homogenous in their texture and inorganic. When more carefully inspected, how- ever, and especially in the articular cartilages, a particular struc- ture is apparent. —According to De Lasone and Hunter, the articular cartilages are composed of fibres implanted perpendicularly to the surface of the bones, and parallel with each other, like the villi or threads upon a piece of velvet. In this manner the cartilages covering the bones forming the joints, which are invested with the syno- vial membrane, rub against each other, not upon the sides, but upon the ends of the fibres, which brings the elasticity of the lat- ter, into play. The perpendicular direction of these fibres may be made apparent by maceration, or by sawing down a recent * The articular cartilages are the only ones not provided with a fibrous peri- chondrium. The synovial membrane which is reflected over them from the inner face of the capsular ligament, appears to supply the place of perichondrium.__p. CARTILAGES AND THEIR STRUCTURE. 37 bone, and splitting through its cartilage—and they are believed by Beclard, to constitute the free numerous and floating fiocculi, which are seen on the surface of cartilage in its transformations from disease. —It is very probable that there is some cellular tissue in the composition of cartilages: when carefully incinerated, the re- mains present a cellulated appearance. Its existence is rendered still more pH^able, by their being developed in the foetus in a mould of cellular tissue, and from fleshy granulations, being seen occasionally to spring from their surface in various parts of the body. —When a recent cartilage is cut, a whitish juicy fluid is seen to exude from its substance, which must get into it, by imbibi- tion from the surrounding parts, or what is more probable, be carried into it, by white vessels, too small to admit more than the serous portions of theblood. If inflammation take place, which is admitted in many cartilages, though not as yet proven to exist in those of the joints, it differs from ordinary inflammation as these vessels are never so dilated, as to admit the red globules, and present a red appearance. No lymphatics have ever been traced into them, though Mascagni, was disposed to consider them as formed entirely of these vessels; nor have nerves been found in them, the very existence of which in these parts, though so ne- cessary to the perfection of other organs, would have unfitted them for their office. Hence we find them smooth, so as to move upon one another without friction, destitute of nerves, so as to bear pressure without sensation, and feebly supplied with vessels, so as to be little prone to inflammation, if they be not, as Gerdy has suggested, a mere secretion like the hair and nails. Hence they are enabled to bear exposure to the air for a considerable time without change, as stated by Velpeau, and to exist unharmed frequently in the midst of gangrene. —According to J. Davy, their chemical composition is 55. parts in the hundred of water, 44.5, of albumine, and .5 of phos- phate of lime. As in the bones, however, the chemical pro- portions vary at the different periods of life. They are nearly fluid in the foetus, contain a large amount of fluid in youth, have VOL. l. 4 38 ACCIDENTAL DEVELOPEMENT OF CARTILAGES. the proportions given above at puberty, and a much larger amount of earthy matter in old age. In fact, with some few ex- ceptions in the joints, they all have a natural tendency to ossify as life advances. —The structure of cartilage is, however, not fully understood : that they share in some manner in the general circulation of the body, is rendered probable by their being coloured yellow in jaundice, and that they are not reddened when a^fciimal is fed upon madder, like the bones, is said by Beclard, to be owing to the small quantity of phosphate of lime, which they contain, and with which this substance only has affinity. They participate too in the ulcerative process in many parts of the body, as in those of the nose, and as I have many times seen, in those of the larynx and trachea. —All cartilages are divided into two classes, temporary, or os- sescent, and permanent, a distinction which though not perfectly exact, is nevertheless very convenient for the purposes of study. The temporary cartilages, (cartilag temporaries) are those em- ployed in the developement of the bones, those of which the models of the bones are all formed in the foetus, and which gra- dually as the infant advances in growth give place to bony mat- ter. The substitution of bony matter for the cartilaginous, is completed about the period of puberty. —The permanent cartilages (cartilag permanentes) are de- veloped at an early period of life, like the former, but have little tendency to undergo ossification, and retain their cartilaginous character for the whole or the greatest part of life. These com- prise, the articular and costal cartilages, those of the larynx, eustachian tube, auditory meatus, etc. Some of these have a stronger tendency than the rest to ossify, as those of the larynx and ribs, which are frequently found after the fortieth year of life, converted into bone. Accidental developement of Cartilages. —In almost every one of the different tissues of the body, car- tilages have been occasionally met with, but in general onlv OF THE FORMATION OF BONE. ..q after the middle period of life, which from their having appa- rently no fixed laws of developement, have been called acci- dental. —1st. They are found in the form of plates of greater or less size, adherent by both surfaces to the membranes between which they are formed ; in the arteries, where these plates are most fre- quently met with, they are attached on their inner surface to the serous liningjpnbrane, and on the outer to the middle coat of the vessel. —2d. They are frequently met with in the form of roundish or irregular masses in the substance of the different organs, as the arteries, lungs and ovaries. —3d. Under the form of smooth flattened concretions, formed originally according to Meckel, on the outer side of the synovial membrane of the joints, and which develope themselves towards the centre of the cavity of the joints, till their attachment to the membrane is stretched out, so that it becomes a mere pedicle, which not unfrequently breaks off. These form then the loose cartilages so often met with in the knee joint. —All these accidentally developed cartilages have a tendency to be converted into bone, and which are then called accidental ossifications.— Of the Formation of Bone. The generality of bones, and particularly those which are long, are originally formed in cartilage; some, as those of the skull, are formed between membranes, and the teeth in distinct bags. When ossification is about to begin in a particular part of a cartilage, most frequently in the centre, the arteries, which were » formerly transparent, become dilated, and receive the red blood from which the osseous matter is secreted. This matter retains, for some time, the form of the vessels which give it origin, till more arteries being by degrees dilated, and more osseous mat- ter deposited, the bone at length attains its complete form. During the progress of ossification, the surrounding cartilage 4() FORMATION OF BONE. by degrees disappears; not by being changed into bone, but by ,an absorption of its parts, the new-formed bone occupying its place. The ossification of broad bones, as those of the head, begins by one or more points, from which the osseous fibres issue in rays, as seen in Fig. 6. The ossification of long bones, as in those of the extremities, begins by central rings, from which the fibres extend towards the ends of the bones. The ossification of spheri-formed bones, begins by one nucleus, as in the wrist; and that of irregularly shaped bones by different nuclei, as in the vertebras. Some bones are completely formed at the time of birth, as the small bones of the ear. The generality of bones are incomplete until the age of pu- berty, or between the fifteenth and twentieth year, and in some few nstances until a later period. In children, many parts of bones, particularly the ends of long bones, are distinct from the bodies; they are called epiphyses, and can be readily separated from the bodies of bones, by boiling, or by maceration in water. The epiphyses begin to appear after the body of the bone is ossified, and are themselves ossified at seven or eight years of age, though their external surface is still somewhat cartilaginous. They are joined to the body of the bone by the cartilages, which are thick in children, but gradually become thinner as os- sification advances, till at last, in the adult, the external marks of division are not to be seen, though frequently some mark of distinction may be observed in the cancelli. * Parietal boss, of the infant at birth magnified, showing the central point of ossification. At first sight the vascular canals, resemble radiated lines, but with a little attention, they will be found to be vascular channels, slightly tortuous, and originating near the centre of the boss or protuberance from the foramina in the newly formed bone.—p. FORMATION OF BONE. 41 —The developement of bones is the final result of several succes- sive changes. In the foetus the bone is at first represented, by a soft gelatinous mass, continuous throughout as one piece, and in which there is no appearance of joints. The consistence of this matter gradually increases, and presents a cartilaginous appear- ance, about the second or third months of foetal life. At the same period a separation is manifested at the place of the joints. A third change takes place in the cartilage, which is that of ossifica- tion; this co^^Bnces in some of the bones, between the second and third months of foetal life, at various periods in other bones, in many not till long after birth, and is not completed in all the bones of the body till near the period of puberty. —In the metamorphosis of cartilage to bone, the white and ho* mogeneous cartilage which forms the mould of the bone, be- comes hollowed out so as to present irregular cavities,* which subsequently form canals lined by a vascular membrane and filled with a viscous fluid, which extend to the centre of its structure. One of these canals forms subsequently the nutritious foramen. The cartilage becomes opaque and yellowish round this spot, the vessels convey red blood, numerous red points are formed in the structure, and ossification commences at the centre, of the bone; never upon the surface. In the long bones a bony ring is first formed in the centre, and the vascular canals ex- tend themselves in the direction of the extremities—in the flat and thick bones, in radii, attended by a redness in the cartilage, nearest the seat of ossification, and a diffused yellowness beyond it. From these canals the ossific material is deposited, and the central point of ossification grows, till the bone is completed. As the bony portion advances in growth, its redness diminishes, and the vascular canals which are at first large, decrease in size, so as to become in the adult bone microscopical. The ossescent or provisional cartilage of the bone, is solid and has in no in- stance any cavity in its centre. The ring of bone which, as * According to the German anatomists, see page 44, the hollowing of these canals, is produced by an aggregation of the cartilaginous corpuscles, into a series of linear ranges between which the vessels shoot that convey the earthy material of the bone.—p. 4* 42 GROWTH OF BONE. before observed, is the first step of developement in the long bones, has a cavity in its centre which is subsequently destined to lodge the medulla. In the flat bones and especially those of the cranium, ossification commences between the second and third months of foetal life. Those of the cranium are formed between the pericranium and dura mater, and their cartilaginous mould is so thin and soft, that Howship and Beclard have de- nied its existence. The vascularity commences in them at a central point, and the ossific rays pass off in a^pght direction, as seen in Fig. 6, page 40. —Many of these bones, as well as of those in other parts of the body, are of such irregular shape, as to be incapable of being formed of fibres radiating from a single centre; they are, there- fore, developed from several centres, the rays of which finally meet and inosculate. The developement of the thick bones, and the epiphysis of the long bones, takes place in accordance with the same laws. —Growth of Bones. In all the long bones, the extremities or epiphyses, are developed in separate pieces and between them and the ossified shaft there is a cartilaginous lamen, which does not disappear till the bone has attained its full developement. The bones increase in length by the continuous deposit of new ossific matter in this lamen of cartilage, which seems retained there as a soft bed for that purpose. As soon as the bone has attained its full length at puberty, the lamen disappears, and the epiphysis and shaft are consolidated, as seen in Fig. 3, where 2 is the layer of the cartilage, beginning to disappear at one point. The long bones increase in diameter, by the successive addition of new bony matter between the periosteum and bone. It is said to be deposited from the periosteum itself: but that opinion is incorrect, for no membrane can form a tissue, so much at variance with its own structure. It is the blood-vessels w7hich merely ramify minutely through the periosteum, that deposit the matter upon the surface of the bone, precisely as they do in the centre. This mode of growth in diameter by concentric circles, has been proved by experiments made with mixing madder at intervals OSSEOUS CORPUSCLES. 43 in the food of animals, by Duhamil,* Hunter, and Professors Horner and Mussey. On killing the animals, red rings were found surrounding the bones, alternated with white ones cor- responding to the periods of administering or suspending the madder.f At the same time, that there is this increase of matter on the surface, there is a corresponding enlargement in the central or medullary cavity, which is said to be effected by the action of the absorbents. It appears to me, however, to be far more lively, owing to an interstitial growth by which the walls of the cavity are increased in dimensions and the cavity itself necessarily enlarged. —Corpuscles. Purkinje has recently discovered in cartilage gene- rally, and especially in the cartilage of bone, rounded corpus- cles, which are much larger in diameter than the transverse sections of the canals described in p. 30. The existence of these corpuscles, has also been confirmed by the microscopical re- searches of Deutsch, Miescher and Sharpey, and according to Miescher they correspond with the brown spots described by Lewenhoeck as his second order of foramina. In bone deprived of its earthy parts by maceration in acid, their appearance is that of small brown spots, pellucid in the centre, and surrounded with a distinct opaque line, which by a high magnifying power, appeared to Miescher to be denticulated. They are situated be- tween the lamellae, their long diameter being oblique in regard to the direction of the lamella?, and when the work of ossification has not commenced, appear to have no fixed arrangement, and are wedge-shaped, oval, oblong, or flattened, see Fig. 7, p. 44. Of the nature of these corpuscles, little is positively known. Neither vegetable or mineral acids have any effect upon them except to * Duhamil who was no anatomist, considered the growth of bones, as analogous to the vegetation of plants. He placed a silver ring upon the bone of a young animal, which he afterwards fed interruptedly on madder. The white and red strata alternately covering the ring as he found on killing the animal, he errone. ously considered not deposited on the outer surface, but formed by the expansion of the bone bulging over it as takes place in plants.—p. t Rutherford, of Edinburgh, explained this colouring of the bone, without that of the other tissues, by the affinity of the madder for the phosphate of lime, upon which it acted as a mordant.—p. 44 NEW VIEWS OF THE GROWTH OF BONES. render them a little more prominent, on the Fig. 7.* surface of a section of cartilage. Alcohol, ether, or a cold solution of caustic pot- ash has no effect upon them; but if ex- posed to a hot caustic solution, or a long time macerated in water they become completely liquified. —The size of the corpuscles according to the measurements of Miescher, varied in length from the 0.0048 to the 0.0072 parts of a line, and in breadth from the 0.0017 to the 0.0030. The re- searches of this anatomist, of Miiller, and other recent observers, have shown that the formation of cartilage always precedes that of bone,f and that each ossescent or temporary cartilage, is an organic tissue, homogeneous, more or less pellucid, clastic, in its first state almost colourless, afterwards assuming a bluish cast, and having a great many peculiar minute corpuscles interspersed through its substance, as shown by the microscope. —In the conversion of cartilage into bone, the change first com- mences in the cartilage that surrounds the corpuscles, and sub- sequently the cartilaginous corpuscles themselves receive either in their centre or in their parietes the calcareous deposit, so that the ossification of each temporary cartilage is but an evolution, or natural developement which the part is destined to undergo. —Weber, Beclard and others, believe that the calcareous matter * Fig. 7, is a representation from Miescher of the progress of ossification, caused by inflammation in an adult bone, which takes place precisely in the same manner that new bone is formed; a a, the cartilage, the first stage in the formation of bone, and the small bodies thickly interspersed through it are the corpuscles of Purkinje; b b, the first or primary stage of the bony structure, in which the corpuscles ar- range themselves somewhat into lines, and the bony fibres shoot in between them, and in the thickness of the corpuscles themselves saline particles are deposited, which renders them opaque; c c, the new structure completely ossified. t This which was admitted by Albinus, Haller, Scarpa, and others, has been de- nied by Howship and Beclard, in regard to the diaphysis of the long bones, and the bones of the cranium. In the bones of the rabbit, Miescher found a mould of cartilage before a particle of ossific matter had been deposited, and between the pericranium and dura mater, a thin stratum of cartilage. FORMATION OF CALLUS. 4 = is deposited by the vessels, in the cartilaginous mould of the bone, as a foreign body, and that the cartilaginous particles are removed in proportion to make room for it; but this is a mere opinion which has not been proven. —Miescher, asserts that he was unable even with the microscope to ascertain in what manner, the calcareous particles were re- ceived into the cartilage, the strongest powers of the microscope exhibiting no ceJk in which they were placed, nor any calcareous particles of the size of the dispersed corpuscles; all that appeared positively was that the cartilage seemed by degrees to assume the aspect of bone. Formation of Callus. —The most ancient opinion* in regard to the mode of union be- tween broken bones, was, that it was owing to the concretion of a viscous fluid, or imaginary osseous juice poured out between the fragments. This was the opinion of Haller. Duhamil de- monstrated the fallacy of this opinion, by numerous experiments, and instituted a theory of his own which is much nearer the truth. According to him the production of callus or new bony matter, is owing to the swelling, elongation, and subsequent ad- hesion between the periosteum and medullary membrane of one fragment with the corresponding parts of the other; and that from these membranes thus modified, bony matter was deposited in the form of a ring on the exterior of the bone and a plug in its medullary cavity, which held the fragments together by pass- ing across the cavity of fracture, and sometimes by prolongations passing between them through the cavity. John Hunter believed that the reunion of fractured bones took place from the organi- sation of the blood effused around the fracture and between the fragments; a doctrine which now has no supporters. —The credit of giving the most faithful account of the formation of callus, is due to Dupuytren* and Sanson. According to these, the union of fragments of bone, is effected by the formation of two successive stages of callus. One which is provisional or * Journal Univ. de Med. torn. 20. 4(5 RESTORATION OF FRACTURED BONES. temporary, is completed usually in the space of thirty or forty days, by the union and ossification of the periosteum, cellular tissue, and even in some cases of the muscles, so as to constitute an external ring, and of the medullary membrane, so as to con- stitute an internal plug. The other, which he calls definitive or permanent, is formed by the reunion of the surfaces of the frac- ture, with a solidity so much superior to that of the bone in other parts, that it will break any where agai^ rather than at that point, and which is never fully completed under eight, ten, or twelve months, by which time all the provisional callus has been removed, and the medullary canal is completely re-established. —Dupuytren divides the successive organic changes, which at- tend the formation of callus, into five periods. —Theirs/ period, extends from the time of the fracture to the eighth or tenth day, and is characterised by the following pheno- mena : when a fracture takes place, the medullary membrane, the medulla, the periosteum, cellular tissue, and sometimes the muscles themselves, are torn ; blood escapes from the ruptured vessels, surrounds the fragments, spreads in the medullary canal and infiltrates in the surrounding tissue: the hemorrhage stops; a slight inflammation is developed in all these parts, which is the first step towards the production of the callus. The cellular tissue surrounding the bone, becomes very vascular, is thickened, loses its elasticity, and acquires a great degree of consistence; it sends irregular processes into the neighbouring muscles, trans- forms them to a greater or less extent into an analogous tissue, and unites them in a common structure with the periosteum, which is also much thickened and very vascular. A nearly similar change takes place in the cavity of the bone in the me- dulla, and its membrane. The calibre of the medullary canal is contracted by the thickening of the membrane, which presents a fleshy appearance, in consequence of a sort of gelatinous infiltra- tion. The effused blood becomes absorbed, and a ropy, viscous, gelatinous fluid, is poured out between the ends of the fragments, and is essential to the production of the definitive callus. —The second period extends from the tenth or twelfth, to the twentieth or twenty-fifth day. During this period, the engorgement RESTORATION OF FRACTURED BONES. 47 of the surrounding parts diminishes and the muscles are liberated: but the cellular tissue remains condensed, and concentrated round the fracture, presenting grooves or even canals to the tendons of the muscles if any pass in the vicinity of the fracture, in which they can play, though with little freedom, in conse- quence of some existing induration of the cellular tissue. This constitutes the provisional callus, the external portion of which is thickest at the place of fracture, and insensibly terminates upon the fragments of bone. Its internal portion is formed by the periosteum, which is closely attached to the bone. Its struc- ture is whitish, homogeneous, and of a cartilaginous or fibro-car- tilaginous character. The medullary membrane forms a similar plug of provisional cartilaginous matter, which fills up the whole cavity of the bone, above and below the place of fracture. The viscous or gelatinous fluid interposed between the ends of the bones, is now rose-coloured or red, and presents sometimes a flocculent appearance, and is adherent by its margins to the ex- ternal and internal callus. The limb may still be bent at the place of fracture, but no crepitation can be produced. —The third period extends from the twentieth or twenty-fifth day, to the thirtieth, fortieth or sixtieth, according to the age and health of the patient. —Ossification commences in the centre of the cartilage, and by degrees the whole tumour, internal and external, becomes osseous. It is very vascular, and Howship* has succeeded in injecting the vessels. If at this period the bone be cut longitudinally, the provisional callus will be found presenting all the characters of spongy bone, while the fragments will be found movable upon each other, the substance poured out between them, not having apparently undergone much change. —The fourth period extends from the fiftieth or sixtieth day, to the fifth or sixth month. During this period the callus has been changed from the state of spongy, to that of compact bone. —The substance intermediate to the fragments, which presented itself under the form of a line or septum between them, becomes * Microscop. Observ. 48 TERMS USED IN THE DESCRIPTION OF THE BONES AND JOINTS. more consistent, presents a whiter hue, and is ossified towards the end of this period; and the definitive callus is now completed. —The fifth period extends from the fifth or sixth, to the eighth, tenth or twelfth month, during which time the whole of the pro- visional callus is entirely removed, the object of its formation having been effected, that of securely holding the bones together, like splints, till the fractured surfaces become firmly reunited. The periosteum resumes its usual thickness and polish, and the muscles and tendons their entire freedom of motion. —The internal plug of callus having been removed by absorp- tion, the central cavity of the bone, the medullary membrane, and the marrow itself, present their usual appearance.— Of the Terms used in the Description of Bones and their Articulations. The study of this subject has been rendered more difficult by the unnecessary introduction of many hard words, but some of these words are so generally used, that they ought to be under- stood by the student of anatomy. The word process signifies any protuberance or eminence aris- ing from a bone. Particular processes receive names from their supposed re- semblance to certain objects; and their names are very often composed of two Greek words, thus the term coracoid, which is applied to a well-known process, is derived from the Greek words xo£«!, a crow, and si&>s, resemblance. If a process has a spherical form, it is called a head. If the head is flattened on the sides, it is denominated a condyle. A rough protuberance is called a tuberosity. A ridge on the surface of a bone is called a spine. The term apophysis is nearly synonymous with process. It signifies a protuberance that has grown out of the bone, and is used in opposition to the term epiphysis, which signifies a portion of bone growing upon another, but distinct and separable from it; as is the case in infancy with the extremities of the long bones. The cavities on the surfaces of bones are named in the same V ~i v TERMS USED IN THE DESCRIPTION OF THE BONES AND JOINTS. 49 way, as will appear by a reference to the glossary at the end of this work. Words of this kind have been used most profusely in the descriptions of articulations, and here also their utility is doubt- ful. Therefore, for many terms used on this occasion, the reader is referred to the glossary; but the following are necessary to be understood. Symphysis does not merely imply the concretion of bones origin- ally separate, as its derivation imports; but it is understood also to mean the connexion of bones by intermediate sub- stances. Thus, there are three species of symphysis, particu- larly noticed, viz. Synchondrosis, when bones are connected to each other by car- tilage; as the ribs and sternum. Synneurosis, when they are connected by ligaments, as in the movable articulations. Syssarcosis, when they are connected by muscle. The different articulations are of two kinds, viz. Synarthrosis and Diar- ihrosis. Synarthrosis is the name of that kind of articulation which does not admit of motion. There are three species of synar- throsis, viz. Suture, when the indented edges of the two bones are received into each other, as is the case with the bones of the cranium. Gomphosis, when one bone is fixed in another like a nail in a board, as the teeth in their sockets. Shindylesis, when the thin edge of one bone is received into a narrow furrow of another, as the nasal plate of the ethmoid in the vomer. Diarthrosis is the name of that kind of articulation which ad- mits of motion. Of these articulations there are three species, viz. Enarthrosis, when a large head is received in a deep cavity, as the head of the thigh bone in the acetabulum. Arthrodia, when the head is connected with a superficial cavity. vol. 1. 5 50 TERMS USED IN THE DESCRIPTION OF THE BONES AND JOINTS. Ginglimus, when the extremities of bones apply to each other so as to form a hinge. But most of the important joints have so many peculiarities that they cannot be understood without studying them separately. It may, therefore, be doubted whether the classification and arrangement of joints is any way necessary. OF THE HEAD. 51 CHAPTER II. Of the skeleton and its different parts, and the individual bones of which they are composed. The bones of an animal arranged and connected to each other in their natural order, separate from the soft parts, compose a skeleton. The skeleton is said to be natural when the bones are con- nected by their own ligaments, which have been allowed to re- main for that purpose. It is called artificial when the bones are connected with wire, or any foreign substance. The artificial skeleton is best calculated for studying the mo- tions of the different bones, because the dry and hard ligaments of the natural skeleton do not allow the bones to move; but the bones of young animals do not admit of the preparation neces- sary for an artificial skeleton, as their epiphyses would separate, and they are therefore formed into natural skeletons. The study of the skeleton and its mechanical properties, as a piece of machinery, is absolutely necessary to a perfect under- standing of many motions of the body, and of the action and co- operation of muscles; but any observations on this subject will be better understood after the individual bones and the muscles have been described. The skeleton is divided into the head, the trunk, the superior and the inferior extremities. Of the Head. The head comprehends the Skull, or Cranium, and Face. The cranium consists of eight distinct bones, which, when placed in their natural order, form a large spheroidal cavity for containing the brain, with many foramina or apertures that com- municate with it. 52 OF THE CRANIUM. These bones are of a flattened form. They are composed of two lamina or plates called tables, with a cellular structure be- tween them, called meditullium, or diploe. The external table is more firm and thick than the internal. The latter is compa- ratively very brittle, whence it is called the vitreous table. [Be- tween the two tables which compose the flat bones of the cranium and running through the diploe are several sinuses, which are oc- cupied by veins in the recent subject. They were discovered by M. Fleury about twenty years ago, while he was Prosector at the School of Medicine in Paris, and engaged in some inquiries relative to the structure of the cranium at the instigation of M. Chaussier. The account which M. Chaussier gives of these veins is as follows: they are situated in the middle of the diploe between the two tables of the skull, and like all other veins are intended to return the blood to the heart. They are furnished with small valves, have extremely thin and delicate parietes, and commence by capillary ramifications coming from the dif- ferent points of the vascular membrane which lines the cells of the diploe. Their roots are at first extremely fine and numer- ous, form by their frequent anastomoses a kind of network, and produce by their successive junction, ramuscles, branches, and large trunks, which, becoming still more voluminous, are direct- ed towards the base of the cranium. Some varieties exist in regard to the number, size, and disposition of these trunks, but generally one or two of them are found in each side of the frontal bone, two in the parietal bone, and one in each side of the occipital bone. Anastomoses exist between these several trunks, by which the veins in the parietal bone are joined to those in the frontal and in the occipital. Branches from the right side of the head also anastomose with some from the left side. Besides the branches already mentioned, one or two smaller than the others are directed towards the top of the head and terminate in the longitudinal sinus. The descending veins of the diploe communicate in their passage with the contiguous superficial veins, and empty into them the blood which they receive from the several points of the diploe. These communications are produced through small fora- OF THE CRANIUM. 53 mina which penetrate from the surface of the bone to the diploe. The trunks of such diploic veins as are continued to the base of the cranium, open partly into sinuses of the dura mater, and partly into the venous plexus at the base of the pterygoid apo- physes, and form there the venous communications called the emissaries of Santorini. Moreover, there are communications sent from the diploic veins through the porosities of the internal table of the skull to the veins of the dura mater. This fact is rendered very evident by tearing off the skull cap, when the sur- face of the dura mater will be studded with dots of blood, and the internal face of the bone also, particularly in apoplectic sub- jects. It appears indeed that the arteries of the cranium are principally distributed on its external surface, and the veins on its internal surface and diploe. In the infant the diploic veins are small, straight, and have but few branches: in the adult they correspond with the descrip- tion just given; and in old age tb.ey are still more considerable, forming nodes and seeming varicose. In children, when the bones are diseased, they partake of the latter character. In order to see them fully, the external table of the skull must be removed with the chisel and mallet, both from its vaults and base.]* The periosteum, which is on their external surface, is called pericranium. Internally the dura mater, or membrane which covers the brain, supplies the place of periosteum. There are eight of these bones, which are thus denominated : Os Fronds, Ossa Parietalia, Ossa Temporum, Os Occipitus, Os Sphenoides, and Os Ethmoides. The two last are called common bones, to denote that they are connected with the bones of the face as well as with those of the cranium. The os frontis forms the whole fore part of the vault of the * The diploe, or meditullium, corresponds exactly in structure and situation with the spongy, or cellular tissue of the other bones of the body, though it has unnecessarily received a distinct name. Neither are the diploic sinuses peculiar to the bones of the skull. They are found presenting exactly the same appearance in the bodies of the vertebra?, and appear in fact to be but a developement of the canaliculated tissue of the other bones. See Fig. 5, page 30.—p. 5* 54 THE SUTURES. cranium : the two ossa parietalia form the upper and middle part of it; the ossa temporum compose the lower part of the sides; the os occipitis makes the whole hinder part and some of the base; the os ethmoides is placed between the orbits of the eyes, and the sphenoides extends across the base of the cranium. The Sutures. The above bones are joined to each other by five sutures; the names of which are the Coronal, Lambdoidal, Sagittal, and two Squamous. The coronal suture is extended over the head, from within about an inch of the external angle of one eye, to the like distance from the other; which being near the place where the ancients wore their garlands, this suture has hence got its name. Though the indentations of this suture are conspicuous in its upper part, yet an inch or more of its end on each side has none, but is squamous and smooth. The lambdoidal suture begins some way below, and further back than the vertex or crown of the head, whence its two legs are stretched obliquely downwards, and to each side, in form of the Greek letter A, and are now generally said to extend them- selves to the base of the skull; but formerly, anatomists reckoned the proper lambdoidal suture to terminate at the squamous su- tures : and the portion continued from them on each side, where the indentations are less conspicuous than in the upper part of the suture, they called additamentum suturae lambdoidis. This suture is sometimes very irregular, being made up of a great many small sutures, which surround a number of insulated bones, that are generally more conspicuous on the externa] sur- face of theskull than internally. These bones are commonly call- ed triquetra or wormiana; their formation is owing to a greater than ordinary number of points of ossification in the skull, or to the ordinary bones of the cranium not extending their ossifica- tion far enough or soon enough; in which case, the unossified in- terstice between such bones begins a separate ossification, in one or more points ; from which the ossification is extended to form THE SUTURES. 55 as many distinct bones as there were points which are extended into the large ordinary bones, and into each other.* The sagittal suture is placed longitudinally, in the middle of the upper part of the skull, and commonly terminates at the middle of the coronal and of the lambdoidal sutures; between which it is said to be placed, as an arrow is between the string and the bow. This suture is sometimes continued through the middle of the os frontis down to the root of the nose. The squamous agglutinations, or false sutures, are one on each side, a little above the ear, of a semicircular figure, formed by the overlapping (like one scale upon another) of the upper part of the temporal bones on the lower part of the parietal, where, in both bones, there are a great many small risings, and fur- rows which are indented into each other: though these inequali- ties do not appear until the bones are separated. In some skulls, indeed, the indentations here are as conspicuous externally as in other sutures; and what is commonly called the posterior part of this squamous suture, always has the evident serrated form ; and therefore is reckoned by some a distinct suture, under the name of additamentum posterius suturae squamosae. The squamous suture is not confined to the conjunction of the temporal and parietal bones, but is made use of to join all the edges of the bones on which each temporal muscle is placed; for the two parts of the sphenoidal suture, which are continued from the anterior end of the common squamous suture just now described, one of which runs perpendicularly downwards and the other horizontally forwards ; and also the lower part of the coronal suture already taken notice of, may all be justly said to pertain to the squamous suture. This structure appears to depend upon the pressure of the temporal muscle externally, and the resistance of the brain within, which makes the bones so thin, that their edges opposed * These ossa triquetra or wormiana are also frequently met with in the sagittal suture, and occasionally in all the different sutures of the cranium. As many as fifteen or twenty have been seen in a single head, though usually their number is much Jess. Where the cranium is of a globular form, few, and frequently none, are met with. They never begin to ossify till six months or a year after birth.—p. 56 THE SUTURES. to each other are not sufficiently thick to stop the extension of their fibres in length, and thus to cause the common serrated ap- pearances of sutures; but the narrow edge of the one bone slides over the other. The squamous form is also more convenient here; because such thin edges of bones, when accurately ap- plied one to another, have scarce any rough surface, to obstruct or hurt the muscle in its contraction; which is still farther pro- vided for, by the manner of laying these edges on each other; for, in viewing their outside, we see the temporal bones covering the sphenoidal and parietal, and this last supporting the sphe- noidal, while both mount on the frontal, from which disposition it is evident, that while the temporal muscle is contracting, which is the only time it presses strongly in its motion on the bones, its fibres slide easily over the external edges. Another advantage of this structure is, that the whole part is made stronger by the bones thus supporting each other. The indentation of the sutures are not so strongly marked on the inside as on the outside of the cranium; and sometimes the bones seemed to be joined by a straight line: in some skulls, the internal surface is found entire, while the sutures are manifest without. By this mechanism, there is no risk of the sharp points of the bones growing inwards, since the external serrae of each of the conjoined bones rest upon the internal smooth-edged table of the other. The advantages of the sutures are these: 1. The cranium is more easily formed and extended into a spherical figure, than if it had been one continued bone. 2. The bones which are at some distance from each other at birth, may then yield, and allow to the head a change of shape, accommodated to the passage it is engaged in. Whence, in difficult parturition, the bones of the cranium, instead of being only brought into contact, are some- times made to mount one upon the other. [The sutures which unite the bones of the cranium, are gene- rally said to be made by the radii of ossification, from the op- posite bones meeting and passing each other, so as to form a ser- rated edge. This explanation is however insufficient, for the following reasons: we always find the sutures in the same rela- THE SUTURES. 57 tive situation, and observing the same course in the cranium; if they, then, depended exclusively on so mechanical a process, as the shooting of the rays of bone across each other when they met, in ossification on one side of the head occurring sooner or faster than on the other, we ought to find the sagittal suture to one side of the middle line ; it should also, in many instances, be found crooked. Moreover, in all cases where bones arise from different points of ossification and meet, particularly in the flat bones, the serrated edges ought to be formed; this, however, is not the case. The os occipitis, which is formed originally from four points of ossification, and has therefore as many bones com- posing it in early life, never joins these bones together by the ser- rated edge; the acromion process of the scapula is never united to its spine by sutures; the three bones of the sternum never unite by suture, and the same observation holds good in many other instances. Bichat, who rejects this mechanical doctrine, advances an opinion much better founded. The dura mater and the pericranium before ossification commences, form one mem- brane, consisting of two lamina ; it is generally known that the flat bones of the cranium are secreted between these two lamina; now the outline of each bone, long before it has reached its ut- most limits, is marked off by partitions passing between these two membranes. The peculiar shape of the bony junction, or of the suture in adult life, will, therefore, depend upon the ori- ginal shape of the partitions: when the latter are serrated, the points of ossification will fill up these serras; but when they are simply oblique, the squamous suture will be formed. This also accounts for cases where the mode of junction is intermediate to the squamous and serrated suture; for the formation of the ossa triquetra, and why in some skulls they do not exist, whereas in others their extent and number are very considerable. The in- ference will also be drawn from this, that in all ossifications from different nuclei, where these original membraneous septa do not exist, a suture will not be formed; but the bones will join each other, as in a case of callus between the broken extremities of bones. When these septa become weak or thin, either from ori- ginal tendency, as in the case of the sagittal suture, which in 5g THE SUTURES. early life is continued to the root of the nose frequently ; or from advanced age, as in the case of nearly all sutures, the bones of the opposite sides amalgamate, and no appearance of suture is left. It is easy to make a preparation illustrative of these facts, and one now exists in the museum of the University of Pennsyl- vania, in which, by removing the bone from between the mem- branes by means of an acid, and afterwards rendering the mem- branes transparent with oil of turpentine, the septa are seen suf- ficiently distinctly.] Os Frontis. The os frontis, as its name imports, forms the front part of the cranium, and the upper portion of the orbits of the eyes. The external surface of this bone is smooth at its upper con- vex part; but several processes and cavities are observable be- low ; for at the angles of each orbit, the bone projects to form four processes, two internal, and as many external; which are denominated angular. Between the internal and external angu- lar processes on each side, an arched ridge is extended, on which the eyebrows are placed. Very little above the internal end of each of these superciliary ridges, a protuberance may be re- marked in most skulls, called the superciliary or nasal boss, where there are large cavities within the bone, called sinuses. Between the internal angular processes, and in front of the va- cuity for the ethmoid bone, the edge of the os frontis is serrated for articulation with the ossa nasi, and the process of the upper maxillary bone; and from the centre of this surface a small pro- cess arises, which is called the nasal spine. From the under part of the superciliary ridges, the frontal bone runs a great way backwards: these parts are called orbitar processes, which, con- trary to the rest of this bone, are concave externally, for receiv- ing the globes of the eyes, with their muscles, fat, &c. In each of the orbitar processes, at the upper and outer portion of the orbit, a considerable sinuosity is observed, where the glandula lachrymalis is lodged. Near each internal angular process a small pit may be remarked, where the cartilaginous pulley of the superior oblique muscle of the eye is fixed. Be- OS FRONTIS. _„ 59 tween, the two orbitar processes, there is a large vacuity which the cribriform part of the os ethmoides occupies. The frontal bone has frequently little caverns formed in it where it is joined to the ethmoid bone. The foramina, or holes, observable on the external surface of the frontal bone, are three in each side. On each superciliary ridge, at the distance of one-third of its length from the nose, is a foramen, or a notch, through which pass a branch of the ophthalmic artery and a small nerve. In the internal edge of each orbitar process are two other foramina denominated anterior and posterior orbitar or ethmoidal foramina, which lead to the nose: sometimes they are only notches or grooves, which join with similar grooves in the bones below, and form foramina. They transmit the anterior and posterior ethmoidal arteries and veins, and the former transmits likewise the internal nasal branch of the ophthalmic nerve. The internal surface of the os frontis is concave, except at the orbitar processes, which are convex, and support the anterior lobes of the brain. This surface is not so smooth as the exter- nal; for the larger branches of the arteries of the dura mater make some furrows in its sides and back parts, and its lower and fore parts are marked with the convolutions of the anterior lobes of the brain. In the middle of the concave internal sur- face is a groove, which is small at its commencement, and gra- dually increases in diameter as it proceeds upwards. This is formed by the superior longitudinal sinus; at its commencement is a ridge to which the beginning of the falciform process of the dura mater is attached. At the root of this ridge is a small foramen, sometimes formed jointly by this bone and the ethmoid; it is denominated foramen caecum; in it a small process of the falx is inserted, and here the longitudinal sinus begins. The frontal sinuses are formed by the separation of the two tables of this bone at the part above the nose and the internal extremities of the superciliary ridges. In the formation of these cavities, the external table commonly recedes most from the general direction of the bone. These cavities are divided by a perpendicular bony partition, which is sometimes perforated and admits a communication be- gO OSSA PARIETALIA. tween them. Their capacities are often very different in differ- ent persons, and on the different sides of the same person. In some persons whose foreheads were very flat, they are said to have been wanting. They communicate with the nose by means of a canal in the cellular part of the os ethmoides. The os frontis is composed of two tables, and an intermediate diploe, as the other bones of the cranium are: it is of a mean thick- ness between the os occipitis and the parietal bones; and is nearly equally dense throughout, except at the orbitar processes, where, by the action of the eye on one side, and pressure of the lobes of the brain on the other, it is made extremely thin and diapha- nous, and the diploe is entirely obliterated. In this place there is so weak a defence for the brain, that fencers esteem a push in the eye mortal. In such skulls as have the frontal bone divided by the sagittal suture, the partition separating these cavities is evidently com- posed of two plates, which easily separate. Each of the frontal sinuses opens into one of the uppermost cells in the anterior part of the ethmoid bone, and this cell com- municates with the middle channel of the nose under the anterior end of the os turbinatum superius. This bone is united with the parietal, ethmoidal and sphenoi- dal bones of the head; and with the nasal, maxillary, unguiform and malar bones of the face. Ossa Parietalia. Each of the two ossa parietalia is an irregular square; its upper and front edges being longer than the one behind or below. The inferior edge is concave, the middle part receiving the upper round part of the temporal bone. The angle formed by the under and anterior edges is so extended as to have the appear- ance of a process. The external surface of each os parietale is convex. Upon it, somewhat below the middle height of the bone, there is a trans- verse arched ridge, generally of a whiter colour than any other part of the bone; from which, in bones that have strong prints of muscles, we see a great many converging furrows, like so many radii drawn from a circumferc-"" *~»">~<*r> « — •-« "gv~™ ,u\<. OSSA PARIETALIA. gj ridge of each bone the temporal muscle rises: and, by the pres- sure of its fibres, occasions the furrows just now mentioned. Below these we observe, near the semicircular edges, a great many risings and depressions, which are joined to like inequali- ties on the inside of the temporal bone, and form the squamous suture. Near the upper edges of these bones, towards the hind part, is a small hole in each, through which a vein passes from the teguments of the head to the longitudinal sinus.* On the inner concave surface of the parietal bones we see a great many deep furrows, disposed somewhat like the branches of trees: the furrows are largest and deepest at the lower edge of each os parietale, especially near its anterior angle, where a complete canal is sometimes formed. [These furrows are made by the ramifications of the great mid- dle artery of the dura mater: they have been commonly attri- buted to the pulsation of the artery causing the absorption of the bone, but it is more probable that the deposition of the bone has been prevented where the artery beats, and thus the bone becomes modelled over the artery in the same way that it is made to conform to the surface of the brain. If it were exclu- sively an absorption and not a deposition, we should scarcely find the artery occasionally surrounded perfectly by bone.] On the inside of the upper edge of the ossa parietalia there is a large sinuosity, frequently larger in the bone of one side than of the other, where the upper part of the falx is fastened, and the superior longitudinal sinus is lodged. Part of the lateral sinuses generally makes a depression near the angle formed by the lower and posterior edges of these bones; and the pits made by the convolutions of the brain are in no part of the skull more frequent or more conspicuous, than in the internal surface of these bones. The ossa parietalia are the most equal and smooth, and are among the thinnest bones of the cranium; but they enjoy the general structure of two tables and diploe most perfectly. These bones are joined at their foreside to the os frontis, at * It transmits, also, an artery from the integuments to the dura mater, and is called the parietal foramen.—p. VOL. I. 6 62 OSSA TEMPORUM. their long inferior angles, to the sphenoid bone; at their lower edge, to the ossa temporum ; behind to the os occipitis, or ossa triquetra; and above, to one another. Ossa Temporum.* The ossa temporum are situated at the lateral and inferior parts of the cranium; each of them is divided into three portions, a superior or squamous, a posterior or mastoid, and a middle or petrous. The squamous portion is nearly semicircular in form, and very thin; its edge is sharp, and the inner table appears pared away to form the squamous suture with the corresponding edge of the parietal bone. Its external surface is covered by the temporal muscle. At the lower and anterior part of this surface the zygo- matic process arises, it proceeds forward to join the cheek bone, and form an arch under which the temporal muscle passes. At the base of the process is the glenoid cavity for the condyle of the lower jaw. Immediately before this cavity is a tubercle or protuberance, which forms part of the articular surface on which the condyle rises when the jaw is opened. In the posterior part of the cavity is a fissure—called the glenoid—in which part of the ligament of this articulation is fixed. In this fissure is an aperture—glenoid foramen—which communicates with the ca- vity of the tympanum of the ear, and is occupied by a small nerve called chorda tympani; and also by the anterior muscle of the malleus, one of the small bones of the ear. The internal surface of the squamous portion.is concave; it is marked by pits and small eminences, which correspond with the convoluted surface of the brain, and also by impressions of the arteries of the dura mater, as they go towards the parietal bone. The mastoid or occipital portion is the smallest of the three parts of the bone; it consists of an angular portion, which occu- pies a vacuity between the occipital and parietal bones; and of the mastoid process. The mastoid process has some resemblance * This boneJias received the name of temporal, because at the region which it covers, the hair usually commences to turn gray, and thus in some measure indi- cates the different periods of life.—p. OSSA TEMPORUM. go to the nipple; it is composed internally of cells which communi- cate with the cavity of the tympanum. On the internal side of its base is a deep groove in which the posterior belly of the digastric muscle is inserted. Behind this process is the mastoid hole, which transmits a vein, and sometimes a small artery. On the internal surface of this portion is a large groove, which is formed by the lateral sinus. The mastoid hole above men- tioned, opens into this groove. The petrous portion, which is situated between the squamous and mastoid, resembles a triangular pyramid lying on one of its sides. When in its proper position it projects inward and for- ward. The two upper sides form a portion of the internal sur- face of the base of the cranium. The angle formed by these surfaces is very prominent, and divides the fossa from the middle lobes of the brain, or cerebrum from those which contain the cerebellum. One of these sides of the petrous portion looks forward and outward, the other backward and inward. Each of them has eminences and depressions to correspond with the convolutions of the brain. Near the middle of the anterior side is a small furrow, and a foramen denominated Innominatum or Hiatus Fallopii, which transmits the vidian nerve to the aqueduct of Fallopius. About the middle of the posterior side is the large aperture called meatus auditorius internus. The bottom of this cavity is perforated by several foramina; the largest and uppermost of which is the orifice of a winding canal, called improperly the aqueduct of Fallopius, which transmits the portio dura of the seventh pair of nerves. The other foramina transmit the fibres of the portio mollis of the same nerve. Posterior to the orifice of the meatus internus is an oblong depression, with a foramen in it, covered by a shell of bone, which is the orifice of a proper aqueduct or canal that passes from the vestibule of the ear.* The inferior side of the petrous portion forms a part of the ex- ternal surface of the basis of the cranium. On the back part of %.. * This orifice should not be confounded with one which is nearer to the meatus internus, and situated on the angle made by the two sides of the bone.—h. 64 OSSA TEMPORUM. it is the external orifice of the canal, through which the portio dura passes. It is called foramen stylo mastoideum. Before this foramen is a long and slender styloid process, which varies from one to two inches in length; it projects almost perpendicularly from the basis of the cranium, and gives origin to a muscle of the tongue, of the os hyoides, and of the pharynx, and also to several ligaments. [The base of this process is surrounded by a flat projection of bone, occasionally called the vaginal process. On the inside of this process, and rather before it, is the jugu- lar fossa, which, when applied to a corresponding part of the occipital bone, makes the posterior foramen lacerum, through which the internal jugular vein, and the eighth pair of nerves pass out. A small spine often projects into this foramen from the temporal bone, and separates the nerve from the vein; the nerve being anterior. Before this spine, or partition, is the orifice of the second aqueduct of the ear, the aqueduct of the cochlea. This jugular fossa is at the termination of the groove, in the internal surface of the bone, made by the lateral sinus. At a small distance before the jugular fossa is the commencement of the carotid canal, which makes a curve almost semicircular, and then proceeds in a horizontal course to the anterior extre- mity of the bone: through this winding canal passes the carotid artery, and the filaments from the fifth and sixth pair of nerves, which are the beginning of the intercostal nerve. Between the carotid canal and the cavity for the condyle of the lower jaw, at the junction of the anterior part of the squam- ous portion with the petrous portion of this bone, is a very rough aperture, the bony margin of which appears broken; this is the orifice of the bony part of the Eustachian tube, or passage from the throat to the ear. This canal is divided lengthwise by a thin bony plate; the upper passage contains the internal muscle of the malleus bone of the ear; the lower and largest canal is the bony part of the Eustachian tube. The external passage to the ear, called Meatus Auditorius Ex- ternum, is situated between the zygomatic and the mastoid pro- cesses. The orifice is large and smooth above, but rough below, OS OCCIPITIS. 65 and is sometimes called the auditory process. The direction of the canal is obliquely inward and forward. The temporal is articulated with the parietal, occipital and sphenoidal bones, and by its zygomatic process with the malar bone. Os Occipitis. The occipital bone is situated at the posterior and inferior part of the cranium; it is of a rhomboidal figure, with convex and concave surfaces. The upper part of the external surface is smooth: at a small distance above the middle of the bone is the external occipital pro- tuberance, with a curved line on each side of it. Near the middle of the bone the trapezii muscles are attached to this line, and externally, on each side, the occipito frontalis, and the sterno mastoideus. Under this line is a depression, on each side, into wrhich are inserted the complexus and the splenius capitis muscles. Below this is the inferior curved line, and still lower is a mus- cular depression to which the rectus minor posticus is attached on each side near the middle; and the rectus major, and obliquus superior, near the end. Below the protuberance is a spine which passes down the mid- dle of the bone, and at the lower extremity of this spine is the great occipital foramen, which forms the communications be- tween the cavities of the cranium, and the vertebra] column. This great opening transmits the medulla spinalis with its mem- branes, the accessory nerves of Willis, and the vertebral arte- ries and veins. It is rather of an oval form, and the occipital condyles are situated anteriorly on its edges. These condyles are of an irre- gular oval figure; they are not parallel, but incline towrards each other anteriorly. Their articulating surfaces are oblique, look- ing downward and outward; they are received into correspond- ing cavities of the atlas, or first cervical vertebra, and form with them the articulation of the head and neck. From the oblique position of their articulating surfaces, as well as the length of their ligaments and the inclination of their axes towards each other, it results, that their motion is confined to flexion and ex- 6* 66 OS OCCIPITIS. tension. On the internal sides of these condyles is a rough sur- face, to which are attached the strong ligaments that come from the processus dentatus of the second vertebra of the neck. Behind each condyle is a depression in which is situated the posterior condyloid foramen, for transmitting the cervical veins; and at their anterior extremities are two large foramina, (anterior condyloid,) through which pass the ninth pair of nerves. On the internal surface of the os occipitis is the crucial ridge, to which are attached the falx or vertical, and the tentorium, or horizontal process of the dura mater. The groove made by the longitudinal sinus continues from the sagittal suture along the upper limb of this cross. Sometimes it is on the side of the ridge, and sometimes the ridge is depressed, and it occupies its place; at the centre of the cross, the groove for the longitudinal sinus divides into two grooves, for the lateral sinuses; these form the horizontal limbs of the cross, and pro- ceed towards the foramen lacerum where the lateral sinuses emerge from the cavity of the cranium. The lower limb of the cross is formed by a spine which proceeds from the centre to the great occipital foramen, and supports the falx of the cerebellum. The internal surface of the bone is divided by the cross into four portions, each of which is considerably depressed; the two up- per by the posterior lobes of the cerebrum, and the lower by those of the cerebellum. This circumstance occasions great inequality in the thickness of the bone, as the depressed portions are extremely thin, while the ridge adds greatly to the thickness, especially at the centre of the cross, which is opposite to the great external protu- berance. Before the great occipital foramen is the cuneiform process, which is thick and substantial; it terminates by abroad truncated extremity, which is articulated with the body of the sphenoid bone. The internal surface of the cuneiform process is some- what excavated, and forms a large superficial groove for the medulla oblongata; on each side of this groove is a small furrow for the inferior petrous sinuses. The two upper edges of the occipital bone are Serrated, to OS ETHMOIDES 67 articulate, with those of the parietal, and form the lambdoidal suture. The inferior edges are divided into two portions by a small prominence called the jugular eminence; the upper and posterior portion is also serrated for articulation with the mas- toid portion of the temporal; the inferior portion, which is not serrated, applies to the petrous portion of the temporal bone, and a notch in it contributes to the formation of the foramen lacerum. The upper angle of this bone is acute, the lateral angles are obtuse, and the inferior truncated. It is articulated with the pa- rietal, the temporal, and the sphenoidal bones. Os Ethmoides. The os ethmoides is truly one of the most curious bones of the human body. It appears almost a cube, not of solid bone, but exceedingly light and spongy, and consisting of many convoluted plates, which form a network like honey-comb. It is firmly enclosed in the os frontis, betwixt the orbitary processes of that bone. One horizontal plate receives the olfactory nerves, which perforate that plate with such a number of small holes, that it resembles a sieve; whence the bone is named cribriform, or eth- moid. Other plates are so arranged that they form a cellular structure, on which the olfactory nerves are expanded by means of a particular membrane; while an additional plate, appropria- ted to the nose, descends into that cavity in a perpendicular di- rection, and forms a large proportion of the partition which divides it into two chambers. The cribriform plate is situated in the anterior part of the basis of the cranium. The cellular part occupies most of the space between the orbits of the eyes, and the perpendicular plate is to be found in the septum of the nose. The ethmoid bone, for the purposes of description, may be di- vided into three parts, viz. the cribriform plate, the nasal or per- pendicular lamella, and the cellular portions. The cribriform plate is oblong in shape, and firm in its struc- ture; in the middle of the anterior extremity the crista galli pro- jects from its upper surface, dividing it into two lateral portions, 68 OS ETHMOIDES. each of which is rather concave, and occupied by the bulbous extremity of the olfactory nerve; it is perforated by many fora- mina, which transmit the fibres of the aforesaid nerve. Near the crista galli, on each side, there is a small fissure, through which passes a nervous filament derived from the ophthalmic branch of the fifth pair. The crista galli varies in size in dif- ferent subjects: the beginning of the falciform process of the dura mater is attached to it, and with the opposite part of the os frontis it forms the foramen caecum, already mentioned. It is very conspicuous in the basis of the cranium. The nasal plate of the ethmoid bone seems to be continued downwards from the crista galli through the cribriform plate. It is thin, but firm; it forms the upper portion of the septum of the nose, and, to complete the partition, it unites with the vomer and with a plate of cartilage before. It is very often inclined to one side, so that the nostrils are not of equal size. At a small distance from this perpendicular plate, on each side of it, the cellular portions originate from the lower surface of the cribriform plate; they extend from before backward, and are as long as the ethmoid bone; their breadth between the eye and the cavity of the nose varies in different subjects, from half an inch to more; they extend downwards from the root of the nose or from the cribriform plate, more than half way to the roof of the mouth. Their external surface on each side forms a part of the surface of the orbit of the eye, and is called os pla- num; their internal surface forms part of the external lateral surface of each nostril. This surface extends the whole depth of the nostril, from before backward ; but in many skeletons it is extremely imperfect, owing to the great brittleness of the bony plates of which it is composed. When the bone is perfect, the uppermost half part of this internal surface is uniformly flat, and rather rough ; but below it, about the middle of the bone, a deep groove begins, which extends downwards and backwards, to the posterior extremity ; this is the upper channel or meatus of the nose. The edge of the surface immediately above it projects in a small degree over this channel or groove ; having been de- scribed by Morgagni, it bears his name, and may be considered OS ETHMOIDES 69 as one of the spongy or turbinated bones; from its situation, it should be called the first. The groove is very deep, and most of the cells of the posterior part of the ethmoid bone communicate with it, through one or more foramina at its anterior extremity. The part of the surface of the ethmoid which is immediately below this groove, is convex; that which is before and below it, is rather flat; the convex part is the upper spongy or turbinated bone, as it has commonly been called; it projects obliquely into the cavity of the nose, and hangs over the middle channel or meatus, which is immediately below the ethmoid bone. The in- ternal surface of this spongy bone, which is opposite the septum of the nose, is convex and rough or spongy; the external surface is concave. The anterior cells of the ethmoid, and particularly those which the frontal sinuses on each side communicate with, open into the middle channel or meatus, under the anterior end of this turbinated bone. This middle channel or meatus, is much larger than that above; it extends from the anterior to the posterior part of the nostrils, and slope* downwards and backwards. The cavity of the up- per maxillary bone, or the antrum highmorianum, opens on each side into this meatus, and a thin plate of bone extends from the cellular part of the ethmoid so as to cover a part of it. The cellular portions of the ethmoid are composed of plates thinner than the shell of an egg; they are entirely hollow, and the cells are very various, in number, size, and shape. Some cells of the uppermost row communicate with those of the os frontis, formed by the separation of the plates of the orbitar pro- cess of that bone. From the posterior part of the cribriform plate, where it is in contact with the lesser wings of the sphenoidal bone, thin plates of bone pass down upon the anterior surface of the body of the os sphenoides, one on each side of the azygos process, and often diminish the opening into the sphenoidal cells. These plates are sometimes triangular in form, the bases uniting with the cribriform plate. They have been described very differently by different authors, some considering them as belonging to the 70 OS ETHMOIDES. os ethmoides, and others to the sphenoid bone. To the perfect ethmoid bone there are attached two triangular pyramids, in place of the triangular bones; these pyramids are hollow, the azygos process of the os sphenoides is received between them; one side of each pyramid applies to each side of the azygos pro- cess, another side applies to the anterior surface of the body of the sphenoid bone, in place of the ossa triangularia, and the third side is the upper part of one of the posterior nares.* There are * This may be considered as an original observation of the lamented Wistar. The merit of it has been denied to him, more particularly by the anatomists of Paris, under an impression that he had been anticipated in it by Bertin, who has written an excellent and minute treatise on osteology. The extent to which the claims of other anatomists interfere with his, he was fully aware of; and it will be seen by the following communications to the American Philosophical Society, that these are placed in as important a light as they deserve, at the same time that he vindicates his own pretensions, to have first observed the " cornets sphenoidaux" in the form of triangular hollow pyramids, as constituting part of the perfect ethmoid bone.—h. Observations on those Processes of the Ethmoid Bone which originally form the Sphenoid Sinuses. By C. Wistar, M. D. President of the SocietymPr ofessor of Anatomy in the University of Pennsylvania.—Read, Nov. 4, 1814. It has been long believed that the sinuses, or cavities in the body of the os sphenoides, were exclusively formed by that bone, when Winslow suggested that a small portibn of the orbitar processes of the ossa palati contributed to their for- mation.* Many years after Winslow's publication, Monsieur Bertin described two bones which form the anterior sides of these sinuses, and contain the foramina by which they communicate with the nose.t These bones he denominates " Cornets Sphenoidaux," and states that they are most perfect and distinct between the ages of four years and of twenty; that they are not completely formed before this period, and that after it they appear like a part of the sphenoidal bone.—According to his account they are lamina of a tri- angular form, and are originally in contact with the anterior and inferior surface of the body of the os sphenoides, so that they form a portion of the surface of the cavity of the nose.—He believed, that as they increase in size, they become convex and concave, and present their concave surfaces to the body of the sphenoidal bone, which also becomes concave, and presents its concavity to those bones; thus forming the sinuses. * In his description of the Ossa Palati, printed in the Memoirs of the Academy of Sciences for 1720. f See Memoirs of the Academy of Sciences for 1774. 03 SPHENOIDES. ~j two apertures in each of these pyramids; one at the base open- ing directly into the nose, near the situation of the opening of the This account of M. Bertin has been adopted by Sabatier, and also by Boyer, who has improved it by the additional observation, that these triangular bones are sometimes united to the ethmoid, and remain attached to that bone when it is sepa- rated from the os sphenoides. Bichat and Fyfe have confirmed the description of Boyer. The specimens of ethmoid and sphenoid bones, herewith exhibited to the so- ciety, will demonstrate that in certain subjects, about two years of age, there are continued from the posterior part of the cribriform plate of the ethmoid, two Hol- low Triangular Pyramids, which, when in their proper situations, receive between them the azygos process of the os sphenoides.—(See Plate X. Figures 1, 2, 3, with the explanation.) The internal side of each of these pyramids applies to the aforesaid azygos pro- cess ; the lower side of each forms part of the upper surface of the posterior nares ; the external side at its basis is in contact with the orbitar process of the os pajati. The base of each pyramid forms also a part of the surface of the posterior nares, and contains a foramen which is ultimately the opening into the sphenoidal sinus of that side. In the sphenoidal bones, which belong to such ethmoids as are above described, there are'no cells or sinuses ; for the pyramid of the ethmoid bones occupy their places. The azygos process, which is to become the future septum between the sinuses, is remarkably thick, but there are no cavities or sinuses in it. The sides of the pyramids, which are in contact with this process, are extremely thin, and sometimes have irregular foramina in them, as if their osseous substance had been partially absorbed.* That part of the external side of the pyramid which is in contact with the orbitar process of the os palati is also thin, and some- times has an irregular foramen, which communicates with the cells of the aforesaid orbitar process. Upon comparing these perfect specimens of the ethmoid and sphenoidal bones of the subject about two years of age, with the os sphenoides of a young subject who was more advanced in years, it appears probable that the azygos process and the sides of the pyramid applied to it, are so changed, in their progress of life, that they simply constitute the septum between the sinuses; that the external side of the pyramid is also done away, and that the front side and the basis of the pyra- mid only remain ; constituting the Cornets Sphenoidauxt of M. Bertin. If this be really the case, the origin of the sphenoidal sinuses is very intelligible. * See e, Fig. 3. t " Cornet" is the word applied by several French anatomists to the Ossa Turbinati of the nose; they seem to have intended to express by it a convoluted lamina or plate of bone. The fine drawing of the Ethmoid Bone, for this plate was done by my friend M. Lesueur, whose talents are so conspicuous in the plates attached to Peron's "Voyage de Descouvertes aux Terres Australes." 72 OS SPHENOIDES. sphenoidal sinuses, in the bones of adults; and the other in each of the sides in contact with the azygos process. Os Sphenoides. The os sphenoides or pterygoideus, resembles a bat with its wings extended. It consists, 1st. Of a body with two processes arising from it, called the lesser wings, or apophyses of Ingrassias. 2dly. Of two large lateral processes, called the greater icings, or temporal processes; and, 3dly. Of two vertical portions, denominated pterygoid pro- cesses. The body is situated near the centre of the cranium, and in con- tact with the cuneiform process of the occipital bone; the greater icings extend laterally between the frontal and temporal bones as high as the parietal; while the pterygoid processes pass down- Explanation of the Figures in the Plate referred to above. FIG. I. Represents the upper surface, or cribriform plate of the Ethmoid Bone. a. Crista Galli. 6 6 6 6. Cribriform plate. c. Surface denominated Os Planum. d d. Hollow Triangular Pyramids. e. Space between the Pyramids for receiving the Azygos Process of the Os Sphe- noides. FIG. II. A lateral View of the Bone. a. Crista Galli. c. Os Planum. d. Triangular Pyramid. FIG. III. The Bone Inverted. a. The Nasal Plate of the Ethmoid Bone, which constitutes the upper portion of the Septum of the nose. g g. Those portions of the Ethmoid which are called Superior Turbinated Bones. //. The Cellular Lateral Portions of the Bone. d d. The Triangular Pyramids. e. Space between the Pyramids for the Azygos Process of the Os Sphenoides— a foramen on the internal side of one of the Pyramids. tv/. r i'.,,..-,\6 i3^ OS SPHENOIDES. 73 wards on each side of the posterior opening of the nose, as low as the roof of the mouth. It is, therefore, in contact with all the other bones of the cranium, and with many bones of the face. The body has a cubic figure, its upper surface forms a portion of the basis of the cranium; its lower and anterior surfaces form part of the cavity of the nose ; the posterior surface is arti- culated with the cuneiform process of the occipital bone; and laterally it is extended into the great wings, or temporal pro- cesses. On the upper surface of the body, the lesser wings or the apophyses of Ingrassias,* project from the lateral and anterior parts; these wings consist of two triangular plates, each of which is joined to the other by its base, and to the body of the os sphenoides by its under surface near the base, and terminates in a point; their direction is forwards and outwards, and their flat surfaces are horizontal. Anteriorly they are connected by suture to the ethmoid and frontal bones; their posterior edge is rounded, and detached from any other bone, forming the upper margin of the foramen lacerum of the orbit of the eye; this edge is thick and prominent at its internal extremity, and these prominences are called the anterior or clinoid processes; imme- diately before them are the optic foramina, which pass obliquely through the wings into the orbit of the eye, and transmit on each side the optic nerve and a small artery. Behind the optic foramen is a notch and sometimes a foramen, made by the carotid artery. A groove made by the optic nerves, is often seen extending across the body of the bone, from one of the optic foramina to the other. Behind it is a depression, which occupies the greatest part of this surface of the bone, in which the pituitary gland is lodged; the back part of this depression is bounded by a transverse eminence, called the posterior clinoid process. These three processes are called clinoid from their supposed resemblance to the supporters of a bed; and the de- pression for the pituitary gland is called cella turcica from its resemblance to the saddle used by the Turks. * A physician of Palermo, who died in 1580, aged 70.—h. VOL. I. 7 74 OS SPHENOIDES. On each side of the posterior clinoid process is a groove in the body of the bone, made by the carotid artery as it passes from the foramen caroticum of the temporal bone. The poste- rior surface of the body of the sphenoides is rough, for articula- tion with the truncated end of the cuneiform process of the os occipitis. On the anterior and inferior surfaces is a spine, called the azygos process, which is received into the base of the vomer, and extends forward until it meets the nasal plate of the ethmoid bone; on each side of this spine, in the anterior surface, are the orifices of the sphenoidal cells. Those orifices appear very dif- ferently in different bones; in some very perfect specimens, they are irregularly oval, being closed below, and on their external sides, by the processes of the ossa palati, and above by the tri- angular plates, as they have been called, of the ethmoid bone. The cells or sinuses, to which these orifices lead, occupy the body of the sphenoidal bone; they are divided by a partition, and each of them has a communication with the cavity of the nose on its respective side, by the orifice above described. The sinuses do not exist during infancy; they increase in the pro- gress of life, and are very large in old age. Laterally, the body of the sphenoides is extended into the por- tions called the great wings or temporal processes. These great wings compose the largest part of the bone, and their internal surface forms a portion of the middle fossa of the base of the cranium. Externally, the surface of each great wing is divided into two portions: one of which is lateral, and unites to the fron- tal, temporal, and malar bones, forming part of the smooth sur- face for the temporal muscle; the other portion forms part of the orbit of the eye, and is very regular and smooth. As the ethmoid bone forms part of the inside, this portion of the great wing forms part of the outside of the orbit, and is termed the orbitary process of the sphenoid bone. The horizontal part of each wing terminates in an acute angle termed spinous process, which penetrates between the petrous portion and the articulat- ing cavity of the temporal bone. In this angle is the foramen for the principal artery of the dura mater; near the point of the FORAMINA OF THE SPHENOIDAL BONE. 75 angle is a small process, which projects from the basis of the cranium, and is called styloid. The pterygoid processes pass downwards in a direction almost perpendicular to the base of the skull. Each of them has two plates, and a middle fossa facing backwards; to complete the comparison, they should be likened to the legs of the bat, but are inaccurately named pterygoid, or wing-like processes. The external plates are broadest, and the internal are longest. From each side of the external plates the pterygoid muscles take their rise. At the root of each internal plate, a small hollow may be remarked, where the musculus circumflexus palati rises, and part of the cartilaginous end of the Eustachian tube rests. At the lower end of the plate is a hook-like process, round which the tendon of the last" named muscle plays, as on a pulley. The ossa palati, on each side, rest upon these internal plates; and, therefore, the pterygoid processes seem to support the whole face. Foramina of the Sphenoidal Bone. Before these foramina are described, it is necessary to state, that the nerves of the brain are named numerically, beginning with the olfactory, which is foremost. It should also be observed, that each nerve of the fifth pair is divided, before it passes from the cavity of the cranium, into the three large branches. The first foramina are the optic, which have been already described; they transmit the optic, or second pair of nerves, and a small artery, to the ball of the eye. The second foramen, on each side, is the foramen lacerum. It commences largely at the cella turcica, and extends laterally a considerable distance, until it is a mere fissure. The upper margin of this foramen is formed by the anterior clinoid pro- cesses, and the edges of the smaller wings of the sphenoid bone. This foramen transmits the third, fourth, and sixth pair of nerves, and the first branch of the fifth pair, to the muscles, and the other parts, subservient to the eye. The foramen rotundum, or third hole, is round; as its name imports. It is situated immediately under the foramen lacerum, 76 THE FACE. on each side, and transmits the second branch of the fifth pair of nerves to the upper maxillary bone. The foramen ovale is the fourth hole. It is larger than the foramen rotundum, and half an inch behind it. It transmits the third branch of the fifth pair of nerves to the lower jaw. The fifth hole is the foramen spinale. It is small and round, and placed in the point of the spinous process, behind the fora- men ovale, to transmit the principal artery of the dura mater, which makes its impression upon the parietal bone. The sixth foramen is under the basis of each pterygoid pro- cess, and is therefore called the pterygoid, or the Vidian* foramen. It is almost hidden by the point of the petrous portion of the temporal bone, and must be examined in the separated bone. It is nearly equal in size to the spinous hole. This foramen transmits a nerve that does not go out from the cavity of the skull, but returns into it. The second branch of the fifth pair, after passing out of the cranium, sends back, through this foramen, a branch called the Vidian, which upon its arrival in the cavity of the cranium, enters the temporal bone by the foramen innominatum. Of the Face. The face is the irregular pile of bones composing the front and under part of the head, and is divided into the upper and lower maxillae, or jaws. The upper jaw consists of six bones on each side, of one single bone placed in the middle, and of sixteen teeth. The thirteen bones are, two ossa maxillaria superiora, two ossa nasi, two ossa unguis, two ossa malarum, two ossa palati, two ossa spongiosa inferiora, and the vomer. The ossa maxillaria superiora form the principal part of the cavity of the nose, with the whole lower and forepart of the up- per jaw, and a large proportion of the roof of the mouth. The ossa nasi are placed at the upper and front part of the nose. * From its reputed discoverer, Vidius, a professor at Paris. OSSA MAXILLARIA SUPERIORA. 77 The ossa unguis are at the internal angles of the orbits of the eyes. The ossa palati in the back part of the palate, extending up- wards to the orbits of the eyes. The ossa spongiosa in the lower part of the cavity of the nose; and The vomer in the partition which separates the two nostrils. Ossa Maxillaria Superiora. The ossa maxillaria superiora, or upper jaw bones, may be considered as the basis or foundation of the face; as they form a large part of the mouth, the nose, and the orbit of the eye. The central part of each bone, which may be considered as its body, is hollow, and capable of containing, in the adult, near half an ounce of fluid. The plate which covers this cavity is the bottom of the orbit of the eye. The sockets of the large teeth are below it. The roof of the mouth projects laterally from the inside of it. A process for supporting the cheek bone is on the outside; and another process goes up before it, which forms the side of the nose. In each upper maxillary bone the following parts are to be examined: The nasal process; the orbitar plate; the malar process; the alveolar process; the palatine process; the anterior and posterior surfaces; the great cavity; the internal or nasal surface; and the three foramina. The nasal process, which extends upwards to form the side of the nose, is rather convex outwards, to give the nostril shape. Its sides support the nasal bone ; and a cartilage of the alse nasi is fixed to its edge. The margin of the orbit of the eye is marked by a sharp ridge on the external surface of this process; and the part posterior to this ridge is concave to accommodate the lachrymal sac. The orbitar plate, which covers the great cavity, and forms the bottom of the orbit, is rather triangular in form, and con- cave. In the posterior part is a groove, which penetrates the substance of the bone, as it advances forward, and terminates in 7* 78 OSSA MAXILLARIA SUPERIORA. the infra-orbitary foramen, below the orbit. At the place where this plate joins the nasal process above mentioned, viz. at the inner angle of the orbit, is the commencement of the bony canal, which transmits the lachrymal duct into the cavity of the nose. The malar process projects from the external and anterior corner of the orbitar plate; it supports the malar bone, and is rough for the purpose of articulating with it. The alveolar processes compose the inferior and external mar- gins of the upper maxillary bones. When these bones are applied to each other, they form more than a semicircle: their cavities contain the roots of the teeth, and correspond with them in size and form. They do not exist long before the formation of the teeth commences; they grow with the teeth; and when these bodies are removed, the alveoli disappear. The palate process is a plate of bone, which divides the nose from the mouth, constituting the roof of the palate, and the floor or bottom of the nostrils. It is thick where it first comes off from the alveolar process; it is thin in its middle; and it is again thick where it meets its fellow of the opposite side. At the place where the two upper jaw bones meet, the palate plate is turned upwards, so that the two bones are opposed to each other in the middle of the palate, by a broad flat surface, which cannot be seen but by separating the bones. This surface is so very rough, that the middle palate suture almost resembles the sutures of the skull; and the maxillary bones are neither easily separated, nor easily joined again. The meeting of the palate plates by a broad surface, makes a rising, or sharp ridge, towards the nostrils; so that the breadth of the surface by which these bones meet, serves a double purpose; it joins the bones securely, and it forms a small ridge upon which the edge of the vomer or partition of the nose, is planted. Thus we find the palate plates of the maxillary bones conjoined, forming almost the whole of the palate; while what are properly called the palate bone forms a very small share of the back part only. As these thinner bones of the face have no medulla, they are nourished by their periosteum only, and are of course perforated with many small holes. The anterior surface of the upper maxillary bone is concave; OSSA MAXILLARIA SUPERIORA. 70 the margin formed by the lower edge of the orbit, by the malar process, and by the alveolar processes, being more elevated than the central part. At a small distance below the orbit is the infra- orbitary foramen for transmitting a branch of the superior maxil- lary nerve. When these two bones are applied to each other, and the ossa nasi are in their places, they form the anterior ori- fice of-the nasal cavity, which has a small resemblance to the inverted figure of the heart on cards. The posterior surface has been called a process or tuber. It expands to a considerable size, and is united internally and poste- riorly to the ossa palati. The great cavity extends from the bot- tom of the orbit of the eye to the roof of the mouth, and from the anterior to the posterior surface of the bone; it opens in the cavity of the nose, and is called antrum maxillare, or Highmo- rianum.* There is but a small portion of bone between this cavity and the sockets of the teeth, particularly those of the second malar tooth. The internal or nasal surface of this bone forms a large part of the cavity of the nose, and is concave. At the root of the nasal process is a ridge, for supporting the anterior end of the lower turbinated bone. The nasal process seems continued into the cavity of the nose, and forms a portion of the orifice of the canal for the lachrymal duct, which is on the external side of this cavity, near its anterior opening, and under the lower turbi- nated bone. The orifice in this bone by which the antrum max- illare communicates with the nose, is very large; but it is re- duced to a small size, by a plate from the ethmoid bone, by a portion of the ossa palati, and of the lower spongy bone, each of which covers a part of it. The three foramina are, 1st. The infra-orbitary foramen al- ready described. 2d. The foramen incisivum or anterior pala- tine hole, which passes through the palatine process, from the nose to the mouth. In the nose there are generally two fora- mina, which unite and form but one in the mouth, immediately behind the middle incisor teeth. This foramen is closed by the soft parts during life, and transmits a branch of the spheno-pala- * After an anatomist who described it. 80 OSSA NASI. tine nerve from each side which runs on the septum narium, and joining at the lower part of the canal with its fellow, they unite, and, according to M. Cloquet, form a ganglion. 3d. The pos- terior palatine foramen, which is formed by this bone, and by the os palati, on each side, is situated in the suture which joins them to each other, and transmits to the palate a branch of the upper maxillary nerve. This bone is united to the frontal, nasal, unguiform, ethmoid and malar bones, above; to the ossa palati behind; to the corre- sponding bone, on the opposite side; and to the inferior spongy bone, in the cavity of the nose. Ossa Nasi. The ossa nasi are so named from their prominent situation at the root of the nose. They are each of an irregular oblong figure, being broadest at their lower end, narrowest near the middle, and larger again at the top, where the edge is rough and thick, and their connexion with the os frontis is consequently very strong. They are convex externally, and concave within. The lower edges of these bones are thin and irregular. Their anterior edges are thick, and their connexion with each other, by- means of their edges, is firm; the suture between them, extending down the middle of the nose, forms a prominent line on the in- ternal surface, by which they are united to the septum narium. The uppermost half of their posterior edges is covered by the edges of the nasal processes of the upper maxillary bones; the lower half laps over the edges of these bones; and by this struc- ture they are enabled to resist pressure. [On the posterior sur- face of the os nasi is a groove occupied in the recent subject by a branch of the ophthalmic nerve called the nasal, which enters the nose through the foramen orbitare internum anterius.] They are joined above to the os frontis; before, to each other; behind, to the upper maxillary bones; below, to the cartilages; and in- ternally, to the septum of the nose. Ossa Unguis. The ossa unguis are so named from their resemblance to a nail of the finger. They are situated on the internal side of the OSSA UNGUIS. 81 orbit of the eye, between the os planum of the ethmoid, and the nasal process of the upper maxillary bone. Their external sur- face is divided into two portions, by a middle ridge; the posterior portion forms part of the orbit; and the anterior, which is very concave, forms part of the fossa, and canal, for containing the lachrymal sac and duct. This portion is perforated by many small foramina; and the whole, being extremely thin and brittle, is therefore often destroyed by the preparation of the subject. The internal surface of this bone is generally in contact with the cells of the ethmoid; a small portion of the anterior parts is in the general cavity of the nose. Each os unguis is joined above to the frontal bone; behind to the os planum ; before and below to the maxillary bone. It sometimes is extended into the nose, as low as the upper edge of the inferior spongy bone. Ossa Malarum. The ossa malarum are the prominent square bones which form the cheek, on each side. Before, their surface is convex and smooth; backward, it is unequal and concave, for lodging part of the temporal muscles. The four angles of each of these bones have been reckoned as processes. The one at the external canthus of the orbit call- ed the superior orbitar process, is the longest and thickest. The second terminates near the middle of the lowrer edge of the orbit in a sharp point, and is named the inferior orbitar process. The third, placed near the lower part of the cheek, and thence called maxillary, is the shortest and nearest to a right angle. The fourth, which is called zygomatic, because it is extended back- wards to the zygoma of the temporal bone, ends in a point, and, has one side straight and the other sloping. Between the two orbitar angles there is a concave arch, which makes about a third of the external circumference of the orbit, from which a fifth process is extended backwards within the orbit, to form near one-sixth of that cavity; and hence it may be called the internal orbitar process. From the lower edge of each of the ossa ma- larum, which is between the maxillary and zygomatic processes, the masseter muscle takes its origin. On the external surface of each cheek bone, one or more small 82 OSSA MALARUM. holes are commonly found for the transmission of small nerves or blood-vessels from, and sometimes, into the orbit. On the in- ternal surface are the holes for the passage of the nutritious vessels of these bones. A notch, on the outside of the internal orbitar process of each of these bones, assists to form the great slit common to this bone, and to the sphenoid, maxillary, and palate bones. The substance of these bones is, in proportion to their bulk, thick, hard, and solid, with some cancelli. Each of the ossa malarum is joined, by its superior and inter- nal orbitar processes, to the os frontis, and the orbitar process of the sphenoid bone; by the edge between the internal and inferior orbitar processes, to the maxillary bone; by the side between the maxillary and inferior orbitar process, again to the maxillary bone; and by the zygomatic process to the os temporis. Ossa Palati. The ossa palati form the back part of the roof of the mouth, and extend from it along the external sides of the posterior openings of the nose, into the orbits of the eyes. Each bone may therefore be divided into four parts, the palate square bone, or palatine process, the pterygoid process, the nasal lamella, and orbitar process. The square bone is irregularly concave, for enlarging both the mouth and cavity of the nose. The upper part of its internal edge rises in a spine, after the same manner as the palate plate of the maxillary bone does, to be joined with the vomer. Its anterior edge is unequally ragged, for its firmer connexion with the palate process of the os maxillare. The internal edge is • thicker than the rest, and of an equal surface, for its conjunction with its fellow of the other side. Behind, this bone is somewhat in form of a crescent, and thick, for the firm connexion of the velum pendulum palati; the internal point being extended back- wards, to afford origin to the palato-staphylinus or azygos mus- cle. This square bone is well distinguished from the pterygoid process by a perpendicular fossa, which, applied to such another in the maxillary bone, forms a passage (pterygo-maxillary) for the palatine branch of the fifth nair nf nprvps• nnrl hu nnnthpr OSSA PALATI. 83 small hole behind this, through which a twig of the same nerve passes. The pterygoid process is somewhat triangular, having a broad base, and ending smaller above. The. back part of this process has three fossae formed in it; the two lateral receive the ends of the two pterygoid plates of the sphenoid bone; the middle fossa, which is very superficial, makes up a part of what is commonly called the fossa pterygoidea. The foreside of this pterygoid pro- cess is rough and irregular where it joins the back part of the great tuberosity of the maxillary bone. Frequently several small holes maybe observed in this triangular process, particularly one near the middle of its base, which a little above communicates with the common and proper holes of this bone already men- tioned. The nasal lamella of this bone is extremely thin and brittle, and rises upwards from the upper side of the external edge of the square bone, and from the narrow extremity of the pterygoid process; it is so weak, and, at the same time, so firmly fixed to the maxillary bone, as to be very liable to be broken in separating the bones. From the part where the plate rises, it runs up broad on the inside of the tuberosity of the maxillary bone, to form a considerable share of the sides of the maxillary sinus, and to close up the space between the sphenoid and the great bulge of the maxillary bone, where there would otherwise be a large slit opening into the nostrils. On the middle of the internal side of this thin plate, there is a transverse ridge, continued from one which is similar to it in the maxillary bone for supporting the back part of the os spongiosum inferius. Along the outside of this plate, the perpendicular fossa made by the palate nerve is observable. At the upper and posterior edge of this nasal plate is a notch, which when applied to the sphenoid bone, forms the sphenopa- latine foramen, through which a nerve, artery, and vein pass to the nostril; this notch forms two processes on the posterior part of the bone, the inferior of which is in contact with the internal plate of the pterygoid process of the sphenoidal bone, and has, therefore, been called by some French anatomists, the pterygoid 84 OSSA SPONGIOSA INFERIORA. apophysis of the os palati. The superior and anterior portion is the proper orbitar process of this bone, which is situated at the posterior part of the lower surface of the orbit, and forms a por- tion of it. This process of the os palati is hollow; and its cavity generally communicates with the contiguous cell of the os eth- moides. It has several surfaces, one of which is to be found in the orbit, and another in the zygomatic fossa. The palate square part of the palate bone, and its pterygoid process, are firm and strong, with some cancelli; but the nasal plate, and orbitar processes, are very thin and brittle. The palate bones are joined to the maxillary, by the fore edges of the palate square bones; by their thin nasal plates, and part of their orbitary processes, to the same bones; by their ptery- goid processes, and back part of the nasal plates, to the pterygoid processes of the os sphenoides; by the transverse ridges of their nasal lamellae to the ossa turbinata inferiora, and by the spines of the square bones to the vomer. The Ossa Spongiosa, or Turbinata Infenora. The ossa spongiosa, or turbinata inferiora, are so named to distinguish them from the upper spongy bones, which belong to the os ethmoides; but these lower spongy bones are quite distinct, and connected in a very slight way with the upper jaw bones. They are rolled or convoluted, very spongy, and exceedingly light. Each of them is attached to the os maxillare superius, near the transverse ridge, by a hook-like process, and covers a part of the opening of the maxillary sinus. One end is turned towards the anterior opening of the nose, and covers the end of the lachrymal duct; the other end of the same bone points back- wards towards the throat. The curling plate hangs down into the cavity of the nostril, with its convex side towards the septum. This spongy bone differs from the spongy processes of the eth- moid bone, in being less turbinated or complex, and in havinc no cells connected with it. The Vomer. The vomer is a thin flat bone, which forms the back part of the THE VOMER. 85 septum of the nose. Its posterior edge extends downwards from the body of the os sphenoides to the palatine processes of the ossa palati, separating the posterior nares from each other. The figure of this bone is an irregular rhomboid. Its sides are smooth; and its posterior edge appears in an oblique direction at the back part of the nostrils. The upper edge is firmly united to the base of the sphenoid bone, and to the nasal plate of the ethmoid. It is hollowT for receiving the processus azygos of the sphenoid, and where it is articulated to the nasal plate of the ethmoid, it is composed of two lamina which receive this plate between them. The anterior edge has a long furrow in it, where the middle cartilage of the nose enters. The lower edge is firmly united to the nasal spines of the maxillary and palate bone. These edges of the bone are much thicker than its middle, which is as thin as paper ; in consequence of which, and of the firm union or connexion this bone has above and below, it can very seldom be separated entire in adults; but in a child it is much more easily separated entire, and its structure is more distinctly seen. Its situation is not always perpendicular, but often inclined and bent to one side, as well as the nasal plate of the ethmoid bone. It is united above to the os sphenoides and the nasal plate of the ethmoid bone; before to the middle cartilage of the nose; and below, to the ossa palati and ossa maxillaria superiora. Maxilla Inferior, or Lower Jaw. The form and situation of this bone are so generally known, that they do not require description. To acquire an accurate idea of the lower jaw, it is, however, necessary to examine at- tentively its different parts: viz. the chin, the sides, the angles, and the processes. In the subjects where the bones are strongly marked, there is a prominent vertical ridge in the middle and most interior part of the chin which becomes broad below so as to form a triangle, and on each side of this triangular prominence are transverse ridges; from these eminences the muscles of the lower lip originate. On each side of the jaw, commonly under the second of the VOL. i. 8 86 MAXILLA INFERIOR. bicuspides,or small molar teeth, is the anterior maxillary foramen, through which pass out the remains of the inferior maxillary nerve and blood-vessels. This foramen, has a direction upward and backward. At a small distance behind these foramina, on each side is the commencement of a ridge which continues backward until it forms the edge of the anterior or coronoid process. The alveolar processes, which form the upper edge of the jaw, are on the inside of this ridge; the alveoli or sockets corresponding with the roots of the teeth, in number and form. The lower edge of the jaw, which is denominated the base, is round and firm, ex- cept at the angles, where it is thin. The angle is formed at the posterior extremity of the base: in children it is obtuse; but in adults whose teeth are perfect, it is nearly rectangular. The masseter muscle is inserted into the lower jaw, at the angle; and there are several inequalities on the surface made by this muscle. The anterior or coronoid process, is rather higher than the pos- terior, and forms an obtuse point: into this process the temporal muscle is inserted. The anterior edge of the coronoid process is sharp, and continued into the ridge above mentioned ; from this edge the buccinator muscle arises. As the alveoli are on the inside of this edge and ridge, the jaw is very thick at this place. There is a semicircular notch between this process and the posterior or condyloid; and here the bone is very thin. The condyles are oblong, and are placed obliquely; so that their longest axes, if extended until they intersect each other, would form an angle of more than one hundred and forty de- grees. The neck of the process, or the part immediately below the condyle, is concave on the anterior, and convex on the pos- terior surface. On the inside of the jaw, in the middle of the chin, is a small protuberance, sometimes divided by a vertical fissure; to this are attached the fraenum linguae, and some muscles of the tongue and os hyoides. Farther back is a ridge which extends backwards and upwards, until it approaches the alveoli of the last molar teeth ; where it terminates in an oblong protuberance. To the anterior part of this line the mylo-hyoidei muscles are MAXILLA INFERIOR. 87 attached; and to the posterior extremity, the superior constrictor of the pharynx. The surface of the bone above this ridge is smooth, and covered with the gums and lining membrane of the mouth. The surface below the posterior part of the line is rather concave, to accommodate the submaxillary gland. At a small distance behind the alveoli, and nearly on a line with them, midway between the roots of the two processes, is a large foramen for transmitting the third, or inferior maxillary branch of the fifth pair of nerves, and the blood-vessels which accompany it; the canal, which commences here, terminates at the anterior foramen, already described. The surface of this canal is perforated by many foramina, through which blood- vessels and nerves pass to the different teeth, and to the cancelli of the bone. On the anterior side of the foramen is a sharp- pointed process, from which a ligament passes to the temporal bone. The nerve and vessels, before they enter into this fora- men, make an impression on the bone; and there is generally a small superficial groove which proceeds downwards from it, being made by a small nerve which supplies some of the parts under the tongue. At the angle of the jaw, on the inside, is a remarkable rough- ness, where the internal pterygoid muscle is inserted. The lower jaw moves like a hinge upon its condyles in the glenoid cavity, when the mouth opens and shuts in the ordinary way. When the mouth is opened very wide, the condyles move forward upon the tubercles before the cavities: if the effort to open the mouth is continued, the lower jaw is fixed in that situa- tion, and the whole head is thrown back, which separates the upper jaw still farther from the lower. The lower jaw can be projected forward without opening the mouth, by the movement of both condyles, at the same time, on the tubercles. This bone can also rotate upon one condyle, as a centre, while the other moves out of the glenoid cavity, upon the tubercle: but these important motions can be better understood, after the mus- cles, and the articulation with the temporal bone, in its recent state, have been described. go OF THE TEETH. Of the Teeth. In the adult, when the teeth are perfect, there are sixteen in each jaw, and those in corresponding situations, on the opposite sides, resemble each other exactly. They are of four kinds, viz. incisores, or the fore teeth; cus- pidati, or the canine; bicuspides, or the small grinders; and mo- lares, or the large grinders. On each side of the jaw, supposing it divided in the middle, there are tivo incisores, one cuspidatus, two bicuspides, and three molares. They occur in the order in which they have been named, beginning at the middle of the jaw, as in the following figure. Fig. 8. Each tooth is divided into two parts, viz. the body, or that por- tion which is bare, and projects beyond the alveoli and gums; and the root, which is lodged in the socket. The boundary be- tween these parts, which is embraced by the gums, is called the neck of the tooth. The body and roots consist of bone, which is more firm and hard than the substance of the other bones; but all the surface of the body, which projects beyond the gums, is covered with enamel, a substance very different from common bone. Every tooth in its natural condition has a cavity in it, which commences at the extremity of each root, and extends from it to COMPOSITION OF THE TEETH. 89 the body of the tooth, where it enlarges considerably. This cavity is lined by a membrane, and contains a nerve, with an artery and vein, which originally entered the tooth, by a fora- men near the point of the root, as is evident during the growth of the teeth. These vessels, and the nerve, have been traced into the teeth; although in many subjects the foramina appear to be closed up. Composition of the Teeth. —The bone or ivory of the teeth, (see Fig. 9.) constitutes the whole of the root, and a greater part of the body and neck. The cavity in the centre, for the lodge- ment of the pulp, in whichever of the teeth it is examined, presents an exact similarity of shape to the bodies and fangs of the teeth, as though the latter had been moulded upon the pulp. —The ivory is of a polished pearly whiteness, like that of a piece of white satin. It is composed chemically both of animal and earthy matter, but in different proportions from ordinary bone. If exposed for a considerable time to the action of a weak acid solution, the earthy matter is dissolved, and there is left a flexible, tenacious, dense, and homogeneous mass, much resembling cartilage, but more dense. If, on the contrary, it is exposed to the action of fire, the animal matter is first blackened, then consumed, and there is left a white, hard, friable residue of calcareous matter. —The enamel or vitreous substance, (see Fig. 9,) so named from its resemblance to vitrified minerals, has been with greater pro- priety called by Blake, the cortex striatum, from the lines which it presents upon its sides. It forms a covering nearly a line in thickness upon the crown of the teeth, and is thinned down at its termination upon the neck. Its texture is fibrous or consists of particles piled one upon another, perpendicularly to the bony part, and so closely compressed together, as to leave no obvious 8* Fig. 9. 90 COMPOSITION OF THE TEETH. interval between them. All the wear of the teeth takes place, therefore, at the end of these fibres and not upon their sides; and the enamel is rendered by this arrangement much less liable to fracture. —No vessels have been traced to this substance, nor has it ever been seen like the bony portion, coloured by madder in young animals fed on this substance during the developement of the teeth. But Mascagni, infatuated with his discoveries in the absorbent system, absurdly regarded this substance as en- tirely formed of absorbent vessels.* It is exceedingly hard and strikes fire, on collision with steel. While covering the bone, it presents a milky white appearance; removed from it, it is semi- transparent and opaline. —The enamel is thickest on those parts of the teeth most ex- posed to friction, as on the horizontal surfaces of the grinders, the edges of the incisors, and the points of the cuspidati. The position of the enamel and its arrangement into fibres is well seen in Fig. 9. —The enamel and ivory of the teeth are the most indestructible after death of all parts of the body. In opening tumuli or other ancient places of sepulchre, they are frequently found to have undergone scarcely any decomposition. —The chemical composition of the two substances of the human teeth, consists, according to Berzelius, in the hundred parts, of Enamel. Bone. Animal matter, - Phosphate of lime, with fluate of lime, Carbonate of lime, Phosphate of magnesia, Soda, with some chloride of soda, - Free alkali and animal matter, 100.0 100.0 20.0 88.5 64.3 8.0 5.3 1.5 1.0 1.4 2.0 * Vide Prodrome PURKINJE AND MULLER ON THE TEETH. 91 —Purkinje and Miiller, have recently, with the aid of the micro- scope, investigated very minutely, the structure of the teeth. They describe the bony part of the tooth as consisting of fibres running parallel to each other from the external to the internal surface of the tooth, between which is placed a semi-transparent, homogeneous portion. These fibres they believe to be really tu- bular ; for on bringing ink into contact with them, it was drawn into them, as if by capillary attraction. These tubes Miiller believed to be filled, at least partially, with calcareous matter, which was the cause of the whiteness and opacity of the tooth. In the more transparent parts of carious teeth, the white sub- stance in these tubes presented more of a granular, and less of a compact appearance, under the microscope, than in a sound tooth. —The white colour and opacity of these tubes were removed by the application of acids. On breaking a thin lamella of a tooth transversely in regard to the fibres, and examining the edge of the fracture, he perceived the tubes, stiff, straight, and inflexible, projecting here and there from the surfaces. If the lamella had previously been acted on by acid, the tubes were flexible, transparent and often very long. Hence Miiller in- ferred that the tubes have a basis of animal tissue, and that besides containing calcareous matter in their cavity, they have this tissue in the natural state impregnated with calcareous salts. The greater part of the earthy matter of the tooth is, however, contained in the transparent homogeneous portion between the fibres, in which it can be rendered visible in a granular state by boiling thin lamina of teeth in a ley of potash. —Purkinje, by the aid of the microscope, discovered the cor- puscles that characterise true bone, in layers taken from the external and internal surface of the root; he considers the great mass of the tooth, however, as destitute of organisation.— The alveoli or sockets of the teeth, are formed upon the edge of the jaw: the bone, of which they consist, is less firm than any other part of the jaws: they correspond exactly with the roots of the teeth; and are lined with a vascular membrane which 92 OF THE ALVEOLI. serves as a periosteum to the roots, and assists in fixing them firmly. —They are developed pari passu, with the teeth, and solely for the purpose of giving them a lodgement; hence when the teeth are removed from the jaw, in the living subject, the sockets sub- sequently disappear by absorption, as being of no further use. There are two sets of alveoli, one for the deciduous teeth of the child, and one for the permanent teeth of the adult. Their walls are formed of one plate on the external side of the jaw, and one on the interna], with transverse bony laminae passing between them. On the side of the cavity which they form, their substance is loose and cellular; on their outer side like other bones, they are smooth and compact. —The transverse processes, are rather more prominent than the lateral part of the parietes, corresponding in this respect inversely with the line of enamel on the teeth. —The enamel terminates on the neck of the teeth a little above the level of the sockets, leaving a small space on the bony part of the neck round which the gum is attached. —The alveoli, terminate in as many hollow processes, as there are fangs to the teeth which they lodge: and at the bottom of each of these processes there are one or more minute fora- mina, for the transmission of vessels and nerves to the internal membrane and pulp of the teeth. —The mode of articulation of the teeth in the sockets is called gomphosis; even in their perfect state, the teeth are slightly movable in the socket, of which dental surgeons, occasionally take advantage, in altering the direction of the teeth, by me- chanical means. The firmness of the articulation, depends upon the adaptation in size and shape of the sockets to the fangs, on the gum which surrounds the neck, of the periosteum of the sockets which is continuous with that of the fangs, and of the vessels and nerves, which enter into the foramina, of the fangs. The teeth of different kinds differ greatly from each other, in form and size. The body of the incisores is broad, with two flat surfaces, one anterior and the other posterior; the anterior surface is rather OF THE TEETH. gg convex, and the posterior concave; they meet in a sharp cutting edge. At this edge the tooth is thinnest and broadest; it gradu- ally becomes thicker and narrower, as it is nearer the neck. The enamel continues farther down, on the anterior and posterior sur- faces than on the sides. The incisores of the upper jaw are broader than those of the lower; especially the two internal incisores. The cuspidati are longer than any other teeth, and are thicker than the incisores. Their edges are not broad, as those of the incisores, but pointed; this point is much worn away in the pro- gress of life. The enamel covers more of the lateral part of these teeth than of the incisores. The bicuspides are next to the cuspidati, two on each side. They resemble each other strongly; but the first is smaller than the other, although it generally has a longer root. The bodies are flattened laterally, but incline to a roundish form. On the middle of the grinding surface are depressions which make the edges prominent. On the external edge there is generally one distinct point in each of the bicuspides. The internal edge is lower than the external in the first bicuspis, which gives it a re- semblance to the cuspidatus. In the second bicuspis, the internal edge is more elevated, although the point is not so distinct as it is on the external edge. The bicuspides have generally but one root, which is often in- dented lengthwise, so as to resemble two roots united. The three molares or large grinders, are placed behind the bi- cuspides, on each side. The first and second strongly resemble each other, but the third has several peculiarities. The body of the large grinders is rather square; the grinding surface has often five points, and three of these are on the external side. In the upper jaw these teeth have three roots, two situated externally, and one internally, which is very oblique in its direction; they are all conical in their form. It seems probable that the roots of these teeth are arranged in this way to avoid the antrum maxil- lare. The molares of the lower jaw have but two roots, which are flat, and are placed one anterior and the other posterior; in 94 OF THE TEETH. each of these broad roots there are two canals, leading to the central cavity; whereas, in each root of the upper molares there is but one. The third grinder is called dens sapiential, from its late appearance. It is shorter and smaller than the others; its body is rather rounder, and its roots are not so regular and dis- tinct; for they are sometimes compressed together, and some- times there appears to have been but one root originally, when the whole tooth has a conical appearance. In some cases the dentes sapientiae take an irregular direction, and shoot against the ad- joining teeth. Infants have a set of deciduous teeth, which differ in several respects from those of adults. They are but twenty in number; the five on each side of each jaw, consist of two incisores, one cuspidatus, and two molares or large grinders. The first of them generally protrudes through the gums between the fourth and eighth months of age; the last about the end of the second year. They commonly appear in pairs,* which succeed each other at irregular intervals. Those of the lower jaw are, in most cases, the first. The order of their appearance is this: the central in- cisores appear first, then the external incisores on each side; after these the first molaris, then the cuspidatus, and finally the last molaris on each side. There are many deviations from this or- der of succession, but it takes place in a majority of cases. These deciduous teeth become loose, and are succeeded by those which are more permanent, nearly in the same order in which they appeared, but with a progress much more slow. The incisores generally become loose between the sixth and seventh year; the first molares about the ninth, the cuspidati and the second molares not until the tenth or twelfth, or even fourteenth year. The bicuspides take the places of the infant molares. The three permanent molares appear in the following order: the first of them protrudes a short time before the front teeth are shed; it is the first of the permanent teeth which appears, and is seen between the sixth and seventh year. The second molaris appears soon after the cuspidati and the second bicuspides are seen. * The two teeth of a pair do not appear at the same precise time, but very near to each other. DEVELOPEMENT OF THE TEETH. Ok There is then a long interval; for the last molaris or dens sapi- entiae is seldom seen before the twentieth year, and sometimes not until the twenty-fifth. The teeth are formed upon pulpy substances, which are situ- ated in the alveoli, and are contained in capsules. A shell of bone is first formed upon the surface of the pulp, which gradually in- creases, and the pulp diminishes within it. The body of the tooth is produced first, and the root is formed gradually afterwards; during its formation the root has a large opening at the extremity, which is gradually diminished to the small orifice before de- scribed. The roots, as well as the body, are formed upon the pulpy substance, which gradually diminishes, as they increase. After the external surface of the body of the tooth is formed, the enamel begins to appear upon it, and gradually increases, until it is completely invested. It is probable that the enamel is deposit- ed upon the body of the tooth by the membranous capsule which contains it. This substance, which appears to be formed of ra- diated fibres, is harder and less destructible than bone. Like the substance of bone, it is composed of phosphate, with a small pro- portion of the carbonate of lime; but it is destitute of the car- tilaginous or membranous structure which is demonstrable in bone. The pulpy substances, or rudiments of teeth, may be seen in the foetus, when about four months old. At six months, ossifica- tion can be seen to have commenced on the pulps of the incisores. At the time of birth, the bodies of the infant teeth are distinctly formed. The alveoli, at first, have the appearance of grooves in the jaw, which afterwards are divided by transverse partitions; they enlarge, in conformity to the growth of the teeth, and appear to be altogether influenced by them. The permanent teeth are formed very early: the rudiments of the first permanent grinder on each side have commenced their ossification at birth. At the same time, the rudiments of the per- manent incisores are to be perceived; and their bodies will be found nearly ossified, by the time the infant incisores are pro- truded completely through the gums. x\bout the age of six years, if none of the infant teeth are shed, there will be forty-eight teeth gg DEVELOPEMENT OF THE TEETH. in the two jaws, viz. the twenty infant, and twenty-eight perma- nent teeth, more or less completely formed; —From their mode of developement, structure, and con- nexions with the rest of the economy, the teeth have been consi- dered analogous to the hair, nails, and feathers, of mammiferae and birds, and to the shells of molluscae. It cannot be said that the teeth are absolutely inorganized, that they are mere concre- tions of an effused fluid, since there is no part appertaining to living beings, entirely destitute of life ; but in the hard structure of the teeth, no anatomist has yet demonstrated either vessels or nerves, though there are practical dentists, who assert that they have seen blood issue from the bony part of the teeth, in some of their operations.* * Hunter denies positively the existence of any vessels passing between the pulp and bone of the teeth, as he was not able to render them manifest by injection, as the colouring matter does not pass into them when animals are fed upon madder, except in the forming state, and as they do not share in the general softening of the bones, in rickets and malacosteum. Blake believed that these vessels did exist, but were difficult to demonstrate, like those that we know to pass in the eye from the capsule of the crystalline lens, to the lens itself; Beclard, that there were no vessels in the bone of the teeth, continuous with those of the pulp, but that the former received continually from the latter a nourishing liquid which penetrated it by imbibition, and that it was situated in regard to the pulp, as the hair and nails to the vascular part of the skin. But the morbid alterations which take place in the body of the teeth, the softening and exostosis seen frequently at the roots of the teeth, and the fusion of the latter occasionally to the bottom of the alveoli, render their vascularity highly probable. The fang of a perfectly developed tooth, is covered closely by a membrane, called its periosteum, which is continuous with the periosteum of the socket, and is on all hands admitted to be vascular; the internal cavity is also lined by a highly nervous and vascular membrane. Both of these are intimately connected with the bony structure of the tooth, and require a little force to separate them. This connexion Bell believes to be made by vessels and probably nerves, which pass between them and the bone. Though no artificial injection has been made of the teeth, this writer has seen them tinged with a bright yellow in a young woman who died of jaundice; and when death has taken place from hanging or drowning, when there is usually a congestion of the capillary system, " he has found the osseous part colour- ed with a dull deep red which could not possibly take place if they were de- void of a vascular system; in both instances the enamel remained wholly free from discoloration." I have observed the same thing in the teeth of subjects who have died of cholera. The existence of nerves in the bony part of the teeth Bell const- DEVELOPEMENT OF THE TEETH. 97 —The teeth are formed of concentric layers, and if the pulp which produces them be destroyed from any cause, they lose the little vitality that they may possess, become foreign bodies me- chanically retained in the living parts, and sooner or later are thrown off. —The teeth are distinguished from the bony tissue, by the ab- sence of any demonstrable cellular or vascular parenchyma in their composition, by their being in part exposed to the contact of the atmosphere, which no bone can be without losing its vitality, by the enamel which covers them externally, by their successive evolution and renovation at certain periods of life, and lastly by their wearing out, and being lost in old age, whilst the vital actions are still going on in the rest of the economy. —In many of the lower animals the teeth are evidently a pro- duction of the skin or dermoid tissue, which is reflected in at the commencement of the digestive passages, and many modern anatomists have for the reasons above mentioned, connect- ed them with the description of the digestive organs; other anatomists of distinction, have, however, for purposes of con- venience to the student, chosen to describe them with the bones in which they are developed. Developement of the Teeth. —The teeth, as we have before observed, are developed on a principle different from that of other parts of the body, by germes or gemmules. If the jaws of a foetus are examined with care, even at the period of two months* after conception, an ders manifested by the facts commonly observed by dentists; in filing the teeth no pain whatever is produced till the enamel is removed; but the instant the file begins to act upon the bone, the sensation is exceedingly acute: and when the gums, alveoli and periosteal lining membrane, have receded from the teeth so as to leave the bony part bare, it is exquisitely sensitive when touched with any hard instrument. He admits likewise the existence of absorbents in the bony part of the teeth, for in a tooth in which inflammation had existed for a considerable time, he found after its extraction an abscess in the very centre of the bony structure, communi- cating with the natural cavity and filled with pus.—p. * T. Bell—Beclard. VOL. I. 9 98 DEVELOPEMENT OF THE TEETH. extremely soft, jelly-like substance is seen lying along the edge of each maxillary arch. At the third month it is more consist- ent, and two plates of bone have sprung up at its sides, which are the rudiments of the external and internal alveolar plates. Shortly after this period, the pulpy substance separates into dis- tinct portions, and rudiments of the transverse plates of the al- veoli are seen shooting across, from side to side. These distinct portions of the pulpy substance, are the germs or rudiments from which the teeth are formed; each is partially enclosed in a sac, and receive branches from the vessels and nerves which run along the bottom of the groove. At the fourth month, the enve- loping sac is thick in its texture, and consists of two layers, which are easily separated after a short maceration. Both of these layers, Fox and T. Bell have proved, by their injections, to be vascular :* laying loosely within this double sac is the gela- tinous vascular pulp itself, covered by an extremely thin, delicate vascular membrane, (to which it is closely united by vessels,) which secretes the bony part of the tooth, and is a sort of inter- nal periosteum.! The pulp and its membrane receive their vas- cular and nervous filaments from the proper dental vessels and nerves, which run along the groove in the jaw. The double sac- cular membrane receives its vessels and nerves solely from the gums; and the only attachment between this and the membrane of the pulp, is near the base of the latter, where the dental vessels enter it. The sac is closely united to the gum, hence if we tear the gum that covers the jaws, we necessarily bring with it the entire structure of the germ. —If at this period, the fourth month, we open the germ, we find the pulp presenting exactly the size and shape of the body of the teeth first cut, (incisors) and that its membrane has already com- menced the deposit of its bony tip. —At birth, ossification will be found to have commenced on all * Hunter declared, that the external is soft and spongy, without any vessels; the other is much firmer, "and extremely vascular." Blake on the contrary as- serts, that the external is spongy and full of vessels, the internal one is more ten- der and delicate, and seems to contain no vessels capable of containing red blood. t This membrane is called by Bell the proper membrane of the pulp, and was conjectured by Blake, with much probability, to be a " propagation of the perios- teum of the jaw." Blake on the Te:' ; r OF THE ENAMEL. 99 the pulps of the temporary teeth, (the body of the incisors being nearly completed,) and on each of those of the anterior perma- nent grinders. The commencement of ossification is by three points in the incisors, which form their serrated edges, as seen on their first developement, by a single point for the canine, two for the bicuspide, and three, four, or five on the large molar, ac- cording to the number of processes which they present. Continu- ous deposition of the bony matter from the membrane of the pulp, unites these points together, and by degrees at different epochs, all the bodies are formed; the pulp retiring as it were, as the deposition of bone goes on and encroaches upon its cavity, and elongates itself downward, into the shape of the fang. This is finally formed in the same manner as the bodies, and the pulp is completely enclosed in the bony case of the tooth, except at the foramina where the vessels and nerves enter. Where more than one fang exists to a tooth, the lower part of the pulp, is pre- viously divided into an equal number of processes, by little bony partitions which shoot across from the sides of the alveoli. Of the Enamel. —When the developement of the bony shell has proceeded as far as the completion of the body and neck, the internal layer becomes thickened and more vascular, receives a greater amount of blood, becomes closely attached to the neck, and forms a loose capsule over the body. From the internal face of this membrane, is poured out a thickened whitish fluid, which Ber- zelius considers of the nature of lactic acid, which is speedily consolidated into a dark chalky substance, deposited first upon the tips of bone, and gradually extending down in layers till it covers the whole crown of the teeth. This is the enamel. It becomes gradually whiter and harder, as though by a more per- fect crystallization, but (near to the period at which the teeth are cut,) it is still so soft, as to be frequently cut with the gum lancet.* * In man, the enamel is formed solely by the inner membrane of the sac. The external contributes nothing to the structure of the teeth. But in graminivorous animals, where the flinty covering of the food they feed on requires a more per- fect grinding apparatus, it performs an important part, in adding another element to the structure of the molar teeth, called by Blake crusta petrosa. The cutting teeth are constructed as those of man. In these animals the enamel of the grind- 10Q DEVELOPEMENT OF THE TEETH. —Of the three membranes of the germ or follicle, one only may be considered as permanent, that of the pulp or internal, which secretes the bone of the tooth. —The two outer, or those of the sac, cover the crown of the tooth; and as this is pushed forwards by successive depositions of bony matter from within, they are pressed upon and wasted away by absorption, like the gum, in direct proportion with the advancement of the tooth, so that in perfectly natural dentition, there is little tension or pressure felt. This is called cutting the teeth, a name which expresses the fact, sufficiently well, but literally conveys a wrong idea. —In cases of difficult dentition, the membranes of the sac re- tain their density and vascularity, and are probably thickened by inflammation, and the bony layers formed from the pulp, resisted in their advancement by these membranes, make com- pression upon the pulp and dental nerves; this, like continued pressure made in other parts of the body, becomes exqui- sitely painful, and gives rise to distressing sympathetic disturb- ances. The relief procured is by cutting the gums and sac, which will be more or less immediate, according to the degree of compression and inflammation of the pulp. —The periosteum covering the fangs of the tooth, is a reflected continuation of the periosteum lining the socket, and this again is continuous with that lining the jaw. Of the Permanent Teeth. —The adult or permanent teeth, are developed in a manner almost exactly analogous to the deciduous or infantile. The ers does not form a continuous smooth layer as in man, but passes a little way into the body of the teeth, and is arranged in the form of vertical layers, between which after the inner membrane of the sac has been removed by absorption, the outer one, according to Bell, deposits the pars petrosa, and fills up the intervening space. This is a substance harder than the bone,.but softer than the enamel; and the advantage derived from it is, that it is worn off by trituration more readily than the enamel, so that the latter is constantly maintained in sharp prominent lines upon the surface of the teeth. The same object is here insensibly attained, as a natural consequence of the difference in density of these parts, which the miller effects with much, labour with his pick-hammer, on the burr-stones of his mill—p. DEVELOPEMENT OF THE TEETH 101 germs of mnny of them are distinctly perceptible in the gums of the infant at birth. They are placed at first deep in the jaw at the inner side of those of the deciduous teeth, to the sac of which they are attached at top by a neck-like process, as seen in Fig. 10. As the infantile teeth rise up and make their way through the gum, this process becomes con- nected with the gum, and forms what is called by Hunter the gubernaculum dentis, from its influence in giving the permanent teeth their proper vertical direction, and preventing their making their way at random through the sides, as they do occasionally in cases where the gubernaculum has been destroyed. —Delabarre has given the gubernaculum the name of iter dentis, from an erroneous belief that it was tubular, like the duct of a sebaceous follicle, and gradually opened as the tooth progressed. —At the fifth month of foetal life, according to Bell, and the eighth and ninth, according to Blake and Fox, the germs of the first permanent molars, may be seen at the outside of the infantile row, and those of the permanent incisors behind the deciduous. Fig. 10—1, 2, shows the attachment of the incisor and molar germs of the two sets, just prior to the eruption of the first. The permanent germ is at first placed in the socket of the deciduous tooth, of which it appears, on first view, to be an offshoot or gemmiperous production. Its vessels and nerves are believed to be mere branches of those of the deciduous set. By degrees a distinct socket is formed for it behind the latter, and its process or gubernaculum is elongated, as seen in Fig. 10—3. When the decidu- ous teeth have cut the gum, the two sockets are completely distinct, as seen in Fig. 11, and the gubernaculum is at- tached to the gum. 9* Fig. 11. 1Q2 DEVELOPEMENT OF THE TEETH. —Ossification first commences in the permanent set on the an- terior molares, and may be seen at birth; at the age of twelve months, it has progressed to a considerable extent upon these as well as upon the incisors and the lower cuspidata. At the sixth or seventh year of age the whole of the permanent teeth are more or less ossified, and the incisors are so far completed as to be nearly ready to make their appearance through the gum. At this period there are no less than forty-eight teeth in the two jaws, the twenty deciduous and the twenty-eight permanent, which are in different degrees of developement. The last mo- lars do not begin to ossify till the ninth year, and are the last of all to make their appearance through the gum, whence they have received the name of denies sapientics or wisdom teeth. —The permanent teeth, which are more in number and individu- ally of larger size and form a larger arch than the temporary, are developed at successive intervals, so as to correspond ex- actly, with the increasing size of the jaws from the infantile to the adult state. Hence they cannot correspond in position with the deciduous teeth ; the outer permanent incisor will rise up near the cuspidatus, and the permanent cuspidatus near the first molar of the deciduous set. —Exactly in proportion as the bodies of the permanent teeth are completed and approach the gum, the roots of the deciduous are removed by absorption, till finally the bodies of the latter only are left fixed mechanically in the gum, and are tumbled off at the slightest effort. The process of the removal of the fangs is not perfectly understood; it is not as was once supposed produced by the pressure of the subjacent tooth, for very frequently the com- mencement of absorption is at the neck, and not at the root of the tooth, where no pressure can come, and occasionally takes place even where the germ of the permanent tooth has been de- stroyed. It is more probably owing to the enlarged vessels of the growing permanent teeth, which come from the same branch with those of the deciduous, carrying off all its blood by deri- vation, which leads to the wasting of the latter set, a process of which we find the analogue in the developement of many parts of the foetus. DEVELOPEMENT OF THE TEETH. ,nn —Below is a tabular view of the appearance of the temporary teeth, and also of the periods at which they are changed for the permanent. —It is to be taken, however, as a general rule liable to continual exceptions, not only in regard to the time, but also as to the regular order of appearance. As a general rule, the teeth of the lower jaw appear first, then the coresponding teeth of the upper. Deciduous Teeth. From 5 to 8 months, the four central incisors, " 7 " 10 " four lateral incisors, " 12 " 16 " four anterior molares, " 14 " 20 " four cuspidati, " 18 " 36 " four posterior molares. Permanent Teeth. —The first permanent molares usually pierce the gum before the fall of the central incisors, and their appearance indicates the ap- proaching change. —The following are about the medium periods at which they are cut, but there is a great degree of variation in this respect. Those of the lower are here indicated, and they most commonly precede the upper by about two or three months. About 6^ years, the anterior molares, " 7 " central incisors, " 8 " lateral incisors, " 9 " anterior bicuspides, " 10 " posterior bicuspides, 11 to 12 " cuspidati, 12 " 13 " second molares, 17 " 19 " third molares or dentes sapientice. —Fig. 8 is a side-view of a beautiful set of the permanent teeth of both jaws, fitted in their sockets, showing the exact manner in which the surfaces of each set are adjusted to each other, and the smaller dimensions of the fangs of the wisdom teeth, owing 104 ABERRATIONS OF DENTITION. to the contracted space in which they are developed. These teeth decay early, are comparatively of little utility, and probably from the same cause ; for in cases, where prior to their develope- ment one of the molares in front of them have been removed, they take a more forward position, are developed with larger fangs, and become much more serviceable. —When the first teeth have made their appearance through the gum, they are not yet completed; the process of thickening the body by layers from within, and of lengthening the root below, is for a time still continued by the pulp. After their completion, the only physiological changes they undergo, is the wearing down of the bodies by friction, and the filling up of the top of their cavity within by the pulp, with a yellowish bony matter in old age, which prevents the exposure of the cavity, and protects the vasculo-nervous pulp, which is so exquisitely sensitive, as to be considered by some in the light of a nervous ganglion. This latter process unhappily is not universal, and is especially defec- tive when the teeth decay early in life, apparently before the period nature has assigned them. Aberrations of Dentition. —Occasionally at birth teeth have been found developed on the surface of the gum, as in the cases of Louis XIV. of France and Richard III. of England: in such cases they are generally mere shells, and are quickly shed, and below exist the double series of germs, which are developed in the regular order. —In some rare cases, from the non-existence or disease of the germs, no teeth have ever been developed.* Borelli mentions a case of this sort occurring in a woman then seventy-two years old. —Sometimes the temporary teeth only exist, which fall at the regular period and are never replaced. Occasionally the set of permanent teeth have consisted of double or molar teeth all round. Sometimes the appearance of the temporary teeth has been protracted to the sixth or seventh year, and even then fol- lowed at regular intervals by the permanent set. The number * Oudet. Consid. sur la Nature des Dents et leur Alterations; Journal Univ. Des Sciences Med. torn. 43, 1826. OS HYOIDES. 105 of .the permanent teeth are sometimes less than usual, in conse- quence of the non-developement of the wisdom teeth, which re- main locked up in the jaw, and occasionally produce pain, and even abscesses in the bony structure. —Sometimes there are supernumerary teeth. Haller has seen in an infant of fourteen years, seventy-two teeth, thirty-six in each jaw, which appeared to depend upon a greater number than usual of the dental germs. Some, fond of the marvellous, have described the eruption of a third set of teeth analogous to the two first: but according to Hudson and others, this appearance has probably been owing to the tardy removal of the deciduous set, and the late supplial of their place by the permanent teeth. —Sometimes the direction of the teeth is vicious, leading into the ramus of the jaw, or upon the outer or inner surface of the gums; or upon the roof of the mouth. Accidental developements of teeth have likewise been met with in the orbit, the tongue, pharynx, stomach, and not unfrequently in the ovaries and uterus.— Os Hyoides. The os hyoides is a small insulated bone, supported between the lower jaw and the larynx, by muscles and ligaments, which pro- ceed from the neighbouring parts in various directions. The figure of this bone, as its name imports, resembles the Greek letter u. In its natural situation, the central and convex part is anterior, and the lateral portions extend backwards. The central part is called the body, and the lateral portions the cornua. The body is broad and its upper edge bent inwards, so that the external surface is convex, vertically, as wrell as horizontally. On this surface is a horizontal ridge: the muscles which proceed from the lower jaw are generally inserted above' this ridge, and the muscles from the sternum and scapula below it. The internal or posterior surface of the body is very concave. The cornua, in young subjects, are distinct from the body of the bone, and joined to it by cartilages: near the body of the os 106 ORBIT OF THE EYE. hyoides they are flat; but their figure soon changes, and they ter- minate on each side in a small tubercle. On the upper edge of the bone, where the cornua unite to the body, is a process, equal in size to a small grain of wheat, which has a direction upwards and backwards; this is called the appen- dix, or lesser cornu of the os hyoides: from it proceeds a liga- ment which is attached to the styloid process of the temporal bone, and is sometimes ossified. The basis of the tongue is attached to the os hyoides, and the motions of the bone have a particular reference to those of that organ; but they will be better understood when the parts with which it is connected have been described. An acquaintance with the individual hones which compose the head is principally useful, as it leads to a perfect understanding' of the whole structure, of which each bone is but a small part. This structure comprises the cavities which contain the brain and the most important organs of sense, as well as the foramina subservient to them, which are of so much importance in the practice of medicine and surgery, and also in physiology, that the following descriptions are subjoined. Orbit of the Eye. The figure of this cavity is that of a quadrangular pyramid with its angles rounded; so that it resembles a cone, the bottom being the apex and the orifice the base. The diameter of the cavity passes obliquely outward from the apex behind. As the figure is irregular, the side next the nose does not partake of this general obliquity, but extends in a straight direction from behind forwards. The orbit is somewhat contracted at its orifice, and enlarged immediately within. The form of the orifice is rather oval, as the transverse diameter is longer than the vertical. Seven bones are concerned in the formation of this cavity; the os frontis and a portion of the lesser wing of the sphenoid bone above the os planum or ethmoid, the os unguis, and the nasal process of the ORBIT OF THE EYE. 1q~ upper maxillary bone, and the os palati below; the os malae, and orbitar plate of the sphenoid bone, on the outside. On the upper surface is the depression for the lachrymal gland; and at the orifice is the notch or foramen for the supra-orbitary vessels, &c. which have already been mentioned. On the inner surface are two longitudinal sutures, which con- nect the os planum and the os unguis to the os frontis above, and the os maxillare below. In the upper suture are the two internal orbitary foramina mentioned in the description of the os frontis, the anterior of which transmits a fibre of the ophthalmic nerve, with an artery and vein ; the posterior transmits only an artery and vein. There are also two smaller vertical sutures on each side of the os unguis. On the anterior part of this inner surface is the ridge of the os unguis, and the grooves for accommoda- ting the lachrymal sac, which passes into the canal of the same immediately below. On the lower surface is the aforesaid canal, formed by the nasal and orbitar process of the upper maxillary bone, and that part of the os unguis which is anterior to the ridge. On the poste- rior part of this surface is a groove which proceeds forwards, and penetrating into the bone, becomes a canal that terminates in the infra-orbitar foramen; this groove in the bone is made a canal by the periosteum. The thin plate which forms this surface is the partition between the antrum maxillare and the orbit of the eye, and is more or less absorbed in those cases where po- lypi of the antrum maxillare occasion a protrusion of the eye. The external surface, formed by the malar bone and the orbi- tar plate of the sphenoid, is almost flat. In the posterior part of the orbit it is bounded by two large fissures, which are now to be described. In the posterior part of the orbit are three apertures. The optic foramen, the sphenoidal fissure, and the spheno-maxillary fissure. The optic foramen opens almost at the bottom of the orbit on the inside; its direction is forwards and outwards. The sphenoidal fissure, formed principally by the lesser and greater wings of the sphenoidal bone, begins at the bottom of 108 CAVITIES OF THE NOSE. the orbit, and extends forward, upward, and outward. It is broad at the commencement, and gradually diminishes to a fis- sure. This fissure opens directly into the cavity of the cranium, and admits the third, fourth, sixth, and one branch of the fifth pair of nerves, an artery, and a vein. The spheno-maxillary fissure commences also at the bottom of the orbit, and extends forward, outward, and downward, be- tween the maxillary bone and the orbitar plate of the sphenoid, from the body of the sphenoid to the malar bone. This fissure opens from the orbit directly into the zygomatic fossa. In the re- cent subject it is closed, and only transmits the infra-orbitary nerve and vessels, and a small branch of the superior maxillary nerve. The Cavities of the Nose. These cavities, which are separated from each other by the septum narium, are contained between the cribriform plate of the ethmoid and the palatine process of the upper maxillary and pa- late bones, and between the anterior and posterior nares. They are, therefore, of considerable extent in these directions; but the distance from the septum to the opposite side of the nose is so small, that each cavity is very narrow. The upper surface of each cavity consists of that portion of the cribriform plate of the ethmoid which is between the septum and the cellular portions. Anterior to this, each cavity is bound- ed by the internal surface of the os nasi of its respective side; and posterior to it, by the anterior surface of the body of the sphe- noid bone. These anterior and posterior surfaces form obtuse angles with the upper surface of the nose, and are immediately above the openings called anterior and posterior nares. The an- terior surface partakes of the figure of the os nasi; the upper surface has the perforations of the cribriform plate; the posterior surface has an opening, equal in diameter to a small quill, that leads into the sphenoidal cell, and it is also broader than the an- terior or superior surface. The internal surface, formed by the septum of the nose, which is composed of the vomer, the nasal plate of the ethmoid, and CAVITIES OF THE NOSE. 109 cartilaginous plate, is flat, but rather inclined to one side or the other, so as to make a difference in the nasal cavities. The external surface is very irregular; it is formed by the cel- lular portions of the ethmoid; by a small portion of the os un- guis ; by the upper maxillary bone ; the os turbinatum inferius; the os palati; and the internal pterygoid process of the os sphe- noides. The upper part of this surface is formed by the internal surface of the cellular portions of the ethmoid, which have been described at page 68. It extends from the sphenoid bone, very near to the ossa nasi; and is uniformly flat and rough. About the middle of it begins a deep groove, which penetrates into the cellular structure of the ethmoides, and passes obliquely downwards and backwards. At the upper end of this groove is the foramen by which the posterior ethmoidal cells communicate with the nasal cavity. This is the upper channel or meatus of the nose. At the pos- terior end of it is a large foramen formed by the nasal plate of the os palati and the pterygoid process of the os sphenoides, and therefore, called pterygo or spheno-palatine foramen. It opens externally, and transmits a nerve and an artery to the nose. Below the meatus is the upper spongy bone, which presents a convex surface; its lower edge is rolled up and not connected with the parts about it. This spongy bone covers a foramen in the ethmoid bone, by which its anterior cells and the frontal si- nuses communicate with the nose. Below this spongy bone is the middle channel, or meatus of the nose. The channel extends from the anterior to the posterior part of the cavity. It is very deep, as it penetrates to the max- illary bone. The cells of the ethmoid are above it; the inferior turbinated bone below it; and the upper spongy bone projects over it. In this channel is the opening of the great cavity of the upper maxillary bone. At the anterior extremity of it is a small portion of the os unguis, which intervenes between the nasal pro- cess of the upper maxillary bone and the cells of the ethmoid, and continues down to the lower spongy bone. The lower spongy bone is nearly horizontal, and very conspicu- vol. i. 10 HO CAVITY OF THE CRANIUM. ous. It extends almost from one opening of the nose to the other. Under this bone is the third and largest channel or meatus of the nose. It is made large by an excavation of the upper maxillary bone, particularly at the anterior part. It affords a direct and very easy passage to the posterior opening of the nose and the throat. Near the anterior extremity of this meatus is the lower orifice of the lachrymal duct, which is so situated that a probe properly curved can be readily passed into it through the nostril. There are, then, four foramina on each side, which form com- munications between the cavities of the nose and the adjacent cells, viz. One in the upper meatus, which leads to the posterior ethmoid cells. A second in the middle meatus, which leads to the anterior ethmoid cells and the frontal sinuses. A third in the same meatus, which opens into the maxillary sinus. A fourth in the anterior surface of the body of the sphenoidal bone, which opens into the sphenoidal sinus. To these must be added the opening of the lachrymal canal. It will be useful to the student of anatomy, after placing three or four of the up- permost cervical vertebrae in their natural situation, to take a view of The Cavity between the spine and the posterior JVares, which is bounded above, by the cuneiform process, passing obliquely up- ward and forward ; laterally, by soft parts not yet described; behind, by the bodies of the cervical vertebras ; and before, by the posterior nares, each of which is oblong in form, rounded above, flat below, and separated from the other by a thin parti- tion, the vomer. The Cavity of the Cranium. The upper concave surface of this cavity corresponds with the figure of the cranium. The ridge in it for supporting the falciform process of the dura mater, the groove made by the longitudinal sinus, the impressions of the arteries, and the pits BASIS OF THE CRANIUM. 111 made by the convolutions of the brain, are particularly to be noticed. The Basis of the Cranium Is much more important. It is divided into three fossas on each side; the anterior of these are most superficial, and the posterior the deepest. The bottoms of the anterior fossce are formed by the orbitar processes of the os frontis, and consequently are con- vex ; between them is the cribriform plate of the ethmoid, which is commonly sunk below the adjoining surface. The crista galli is very conspicuous; and the foramen caecum can almost always be seen. The crista galli is evidently the beginning of the pro- minent ridge, which continues on the os frontis, and supports the falx of the dura mater. The posterior margins of these fossas are formed by the lesser wings of the sphenoid bone. The middle fossce are formed by the great wings of the sphenoidal bone, and by the squamous and petrous portions of the temporal bone. They are lower than the anterior, and higher than the posterior fossa?. The projection of the margin of the anterior fossas into these cavities, corresponds with the separation between the anterior and middle lobes of the brain. The suture between the sphenoidal and temporal bones is evi- dent in these fossas. The upper surface of the body of the sphenoid bone, or the sella turcica is between them; and all the peculiarities of its surface are very conspicuous. The first five foramina of the sphenoidal bone can be easily ascertained, and also, the anterior foramen lacerum and termination of the fora- men caroticum, with the impressions made by the carotid arte- ries on the sides of the sella turcica. The petrous portions of the temporal bones are the posterior boundaries of the middle fossas. Their oblique direction, inwards and forwards, is particularly remarkable; being formed like triangular pyramids. Two of their sides are in the cavity of the cranium ; one, which is ante- rior, forms a portion of the middle fossa; and the other forms a part of the posterior fossa. The edge between them is very prominent, and has the tentorium or horizontal process of the dura mater attached to it. On the anterior surface, in the mid- 112 BASIS OF THE CRANIUM. die fossa, may be traced the groove, and the foramen for the Vidian nerve. The posterior fossas are larger as well as deeper than the other two. Their boundaries are well defined by the edges of the petrous bones above mentioned, and by the grooves of the hori- zontal parts of the lateral sinuses. These fossas are nearly separated from the general cavity by the tentorium, which is attached to the edge of the petrous bone and also to the edge of the horizontal part of the groove for the lateral sinuses. On the tentorium lie the posterior lobes of the cerebrum; and under it, in these fossas, is the cerebellum. These fossas may be considered as one great cavity, which is circular behind, and somewhat angular before. The angular surfaces are formed by the posterior sides of the petrous portions. Between them, is the oblique surface of the cuneiform process of the occipital bone, which descends to the great foramen. On the surface of each petrous bone is the meatus auditorius internus, and the orifice of the aqueduct of the vestibule. Behind the petrous portion, the groove for the lateral sinus is very conspi- cuous ; it terminates in the posterior foramen lacerum, which is evidently formed by the temporal and the occipital bones. At the anterior part of this foramen is most commonly a small bony process, which separates the eighth pair of nerves from the internal jugular vein, as they pass out here. The anterior condyloid foramen for the passage of the ninth pair of nerves, appears in the surface of the great occipital hole, immediately below the foramen lacerum. From the back part of this hole the spine, which forms the lower limb of the cross, passes up; and on each side of it are the great depressions which accommodate the two lobes of the cerebellum. External Basis of the Cranium. When the head is inverted, we see the external protuberances of the os occipitis, formerly described. The mastoid processes of the ossa temporum are on the same transverse line with the great foramen of the os occipitis; but the foramen being larger extends farther forward. On the inside of the mastoid process, BASIS OF THE CRANIUM. 113 the fissure for the digastric muscle is very conspicuous, and also the suture between the mastoid process and the occipital bone. The oblique direction of the occipital condyles and the slant- ing position of their articulating surfaces are particularly striking. The posterior condyloid foramina for the cervical veins, and the anterior for the ninth pair of nerves, are also in view. The posi- tion of the cuneiform process of the os occipitis is by no means horizontal, but extends forwards and upwards. The petrous or pyramidal portion of the temporal bone commences between the mastoid process and the condyle of the lower jaw, and extends obliquely forwards and inwards, having the occipital bone behind it, and the glenoid cavity and the os sphenoides before it. At the commencement, the surface of the petrous portion is not horizon- tal, but oblique, sloping into the glenoid cavity with a sharp edge downwards. This edge in some cases is curved so as to sur- round the basis of the styloid process, which arises in contact with it, and projects downwards, on each side of the vertebras. Between the mastoid and styloid process, is the foramen stylo^ mastoideum. On the inside of the styloid process, and rather anterior to it, is the foramen lacerum posterius, for the internal jugular vein, the eighth pair of nerves, &c. This foramen passes obliquely backwards and upwards, and is bounded behind by the jugular process of the os occipitis, which bone seems to contri- bute most to its formation. Very near to this hole on the inside is the anterior condyloid foramen; and rather anterior to it is the opening of the carotid canal, which forms a curve in the bone as it passes upwards, inwards, and forwards. From the foramen lacerum posterius, the suture between the cuneiform process of the occipital and the petrous portion of the temporal bone, extends to the foramen lacerum anterius; which is closed by cartilage in the recent subject, but is of an irregular and rather triangular form in the macerated head; this hole is formed by the occipital, sphenoidal, and petrous bones. The suture or connexion between the petrous bone and the os sphe^ noides, is continued on the anterior side of the petrous bone, from the fissure of the glenoid cavity to the anterior foramen 10** 114 SIDE OF THE HEAD. lacerum. The styloid process of the os sphenoides, which is seldom more than four lines in length, appears at the edge of this suture. On the inside of the glenoid cavity, and on the in- side of this process, in the suture formed between the petrous and sphenoid bones, is the bony orifice of the Eustachian tube. The foramen spinale, for the middle artery of the dura mater, is at a very small distance from the Eustachian tube, imme- diately anterior to it; and at a small distance on the inside and front of this foramen is the foramen ovale, for the inferior maxil- lary nerve, or the third branch of the fifth pair. Side of the Head. Those portions of the side of the head which are formed by the frontal, parietal-and occipital bones, and by the squamous part of the temporal, require no explanation here; but the region which is behind the malar and upper maxillary bone, and within the zygomatic processes of the temporal and malar bones, which comprises part of the temporal and zygomatic fossas of some anatomists, is both important and obscure. To obtain a view of this, the lower jaw should be removed, and the zygoma sawed away, in one preparation; and in an- other, the upper maxillary and palate bones of one side should be applied in their natural position, to the os sphenoides, without any of the other bones. The upper part of this region, formed by the sphenoidal, frontal and malar bones, is made concave by the form of the external angular part of the os frontis and of the os malas ; which projects backwards so as to cover a large portion of it. The lower part is formed principally by the external surface of the pterygoid process of the sphenoid bone, and by the poste- rior surface of the upper maxillary. Between the lower end of the pterygoid process and the upper maxillary bone, a small portion of the os palati intervenes; but in many adult subjects it is not to be distinguished from the other bones. At this place, the pterygoid process and these bones appear to be in close con- tact ; but as they pass upwards they recede from each other so as to form a considerable aperture, which continues the whole FORM OF THE CRANIUM. j jg length of the pterygoid process. This fissure, which may be called pterygo-palatine or pterygo-maxillary, would open into the posterior part of the cavity of the nose, if the nasal plate of the os palati did not intervene; this plate forms a partition, which separates the nose from this fissure: and the spheno-palatine foramen, formed principally by it, transmits a nerve and blood- vessels to the nose. The fissure is vertical: at the back of the orbit, it unites with the spheno-maxillary fissure of the orbit, which is almost hori- zontal, and at the place of their junction, the sphenoidal, or upper fissure of the orbit, opens also. The foramen rotundum, which transmits the second branch of the fifth pair, or the upper maxillary nerve, is likewise situated near this place; and when the upper maxillary, the sphenoidal, and the palate bones are in their natural situation, the distribu- tion of the branches of this important nerve can be easily under- stood: for the same view presents the course of its various branches; viz. to the nose, by the spheno-palatine foramen; to the cavity of the cranium, by the pterygoid foramen; to the orbit, and the inferior orbitary canal, by the spheno-maxillary fissure; and to the roof of the mouth, by the palato-maxillary canal. The Form of the Cranium. The form of the cranium is that of an irregular oval. The greatest length of its cavity is between a part of the os frontis above the crista galli, and of the os occipitis above the centre of the crucial ridge. The greatest breadth is at about two-thirds of the distance from the first to the last of these positions. This transverse diameter touches the sides of the cranium near the posterior part of the basis of the petrous portion of the temporal bone. The difference between these longitudinal and transverse diame- ters varies greatly in different persons, as their craniums ap- proach to the oval or round figures. The greatest depth of the cavity is between the posterior part of the cuneiform process of the occipital bone, and a part of the Hg FORM OF THE CRANIUM. cranium which is nearly over it about the middle of the sagittal suture. The figure of the cranium is somewhat varied in different races of men; and it has been much changed by the particular management of several savage nations. In North America, the Choctaw tribe of Indians were for- merly accustomed to make their foreheads perfectly flat, and sloping obliquely backwards. They have latterly disused this practice; but one of their nation, whose head had this form, was in Philadelphia about the year 1796. At this time a tribe who inhabit a district of country near the sources of the Missouri river, are in the practice of flattening both the frontal and occipital regions of the head; so that a small part only, of the middle of it, remains of the natural form, between these flattened sloping surfaces. In the case of the Choctaw man above-mentioned, it did not appear that his health, or his intellectual operations, were any way affected by this form of his head. During infancy, the cranium sometimes increases to a preter- natural size, as disproportionate to the face as if it were affected by hydrocephalus. In many of these instances, that disease ulti- mately shows itself; but in other cases, the preternatural increase of the cranium finally stops without the occurrence of disease; and the disproportion is lessened by the increase of the face in the ordinary progress of growth. In many cases where men have deviated from the ordinary stature, the head has preserved the common size. It is there- fore said to be small in giants, and large in dwarfs. —Many efforts have been made to determine rigorously the di- mensions of the cavity of the cranium. This may be done with considerable accuracy from the exterior of the skull, by making allowances for the various degrees of developement in which the frontal sinuses are found in different individuals. The thickness of the diploe seldom varies in different skulls more than one or two lines in thickness. There is, however, a skull (a black,) in the possession of Dr. Parrish of this city, the walls of which are nearly three-quarters of an inch in thickness, and so compact in FACIAL AND OCCIPITAL ANGLES. H^ its composition as to present very little of the diploic or cellular structure. When measured from the interior, a skull of ordinary capacity will measure in its longitudinal diameter, (between the frontal spine and longitudinal sulcus,) five inches and a half; in its transverse, (between the bases of the petrous portions of the temporal bones,) four and a half; between the parietal fossas five inches, and between the lesser wings of the sphenoid bones, three inches and three-quarters; in the vertical, from the foramen mag- num to the sagittal suture, four inches and a half. —Several plans have also been adopted, by the cranioscopists, to determine the relative developement of the cranium (which is filled with the brain) and that of the face. The best known of these are those of Camper, Daubenton and Cuvier. The facial angle of Camper, is taken by extending a horizontal line from the ex- ternal auditory meatus, on a line with the floor of the nostrils, so as to follow nearly the direction of the base of the cranium, and by dropping upon this a second from the most prominent part of the forehead to the extremity of the upper jaw. The area be- tween them is the facial angle, and will be the more acute, in direct proportion as the face is developed in front, and the fore- head is sloped backwards. This angle is of course larger in man than in any other animal, and varies in size in the different races of men. In a well formed white or Caucasian, it is usually about 80°; in the Mongolian about 75°; in Negroes about 70°; in the different species of monkeys it varies from 65° to 30°. As a test of the intellectual capacity of individuals, it is but little to be relied on. —The occipital angle of Daubenton, is formed by drawing two lines, one from the inferior border of the orbit, to the anterior margin of the occipital foramen, the other drawn from the ante- rior to the posterior border of the occipital foramen, and extend- ed forwards. The angle between the two, is the occipital. As the direction of the occipital foramen depends upon the manner in which the head is articulated with the vertebral column, it will be the larger, the less favourably the animal is constructed for the upright posture. In a well formed Caucasian skull, it is about 3°. In the ox it is about 70°. Daubenton has thus done 118 HEAD OF THE FCETUS. for the posterior part of the head what Camper has done for the anterior. —Cuvier's method consists in dividing the skull vertically, and establishing a comparison between the area of the cranium and that of the face. In a well formed Caucasian he finds the area of the cranium, quadruple that of the face. In the Mongolian variety, he found the area of the face had increased over this proportion one-tenth, in the Negro, one-fifth; in monkeys one- half. Tiedemann has adopted a plan of measuring the capacity of different crania, by filling them with seeds from the occipital foramen, and subsequently measuring their contents. This me- thod as well as some others, has been applied by Dr. S. G. Mor- ton of this city, in a forthcoming very scientific work on the Crania Americana, so as to leave henceforth little to be wished upon a subject which has excited much interest among physiolo- gists. The whole capacity of the cranium is found on an ave- rage, greater in the Caucasian variety of the human race, than in any other. The Head of the Fostus. In the fostus, these bones, which form the vault of the cra- nium, originally consist of one plate only; which is composed o radiant fibres. At birth, the os frontis consists of two pieces, which join each other in the middle of the forehead. The parietal bones are each in a single piece; but they are incomplete at their edges and their angles. The temporal bones have no appearance of mastoid or styloid processes. Instead of a meatus auditorius externus, there is a bony ring in which the membrana tympani is fixed. The squamous and petrous portions, and this ring, are originally formed separate; but at the period of birth they often adhere to each other. The os occipitis is composed of four pieces: the first and largest, extends from the beginning or angle of the lambdoidal suture to the upper edge of the great occipital foramen. Each side of the foramen, and the condyle on it, is formed by a dis- HEAD OF THE FCETUS. iig tinct piece. The front part is formed by the cuneiform process, which is separate from the other parts and forms the fourth piece. The sphenoidal bone may be separated by maceration into three pieces. The body and the little wings form one piece* Each of the great wings, with the pterygoid processes united to it, forms also a piece. The body of the bone is entirely solid. A large part of the ethmoid is in a cartilaginous state. It is divided into two portions by a partition of cartilage, which occu- pies the place of the nasal plate and the crista galli. In consequence of the imperfect formation of the bones which compose the vault of the cranium, there are several deficiencies in it. Thus the superior anterior angles of the parietal bones being incomplete, and also the upper angles of the pieces which compose the os frontis, a vacuity with four sides is occasioned, which is termed the Anterior fontanel. This opening may be distinguished by its form, as well as its greater size, from another vacuity which is produced in a similar way at the other end of the sagittal suture, and called the Posterior fontanel: but as there are only three bones con- cerned in its formation, viz. the two parietal and the occipital, this vacuity is triangular. Besides these, there are two other vacuities or fontanels on each side, at the two lower corners of each parietal bone: these, however, are much less than those first described. The smaller fontanels do not continue open long; but the an- terior fontanel is seldom completely closed before the end of the third year. It is very obvious, upon an examination of the cranium, that the centre of the base is better calculated to resist pressure than any other part; as the cuneiform process of the occipital bone, the petrous portions of the temporal, and the body of the sphe- noidal bone, which compose a large part of it, are very firm and substantial. The face of the foetus differs very essentially from that of the adult. Although the orbits of the eyes are very large when 120 OF THE SPINE. compared with the size of the head, that portion of the face which is below them is very small, and has little depth. The upper maxillary bones have no sinuses in them; and their orbitar plates are not much elevated above the cavities for con- taining the posterior teeth; in consequence, the depth of the face is very small, and its whole aspect is affected. The nose of the fostus differs greatly from that of the adult in respect to its sinuses; for not only are the maxillary cavities wanting, but those of the frontal and sphenoidal bones also. The lower jaw is formed in two pieces, which unite at the middle; and hence the term symphysis is used in describing the chin. The bone is not only less broad in proportion than that of the adult, but the angles are more obtuse, and the processes which arise from them are more sloping. The head of the foetus is much larger in proportion to the body than that of the adult. Of the Trunk. The Trunk consists of the Spine, Thorax, and Pelvis. The Spine. The spine is the long pile of bones extending from the con- dyles of the occiput to the end of the os coccygis. It somewhat resembles two unequal pyramids joined in a common base. It is not, however, straight; for its upper part being drawn back- wards by strong muscles, it gradually advances forwards to sup- port the oesophagus, vessels of the head, &c. Then it turns backwards, to make room for the heart and lungs. It is next bent forwards to support the viscera of the abdomen. It after- wards turns backwards for the enlargement of the pelvis. And, lastly, it is reflected forwards, for sustaining the lowest great intestines. The spine is commonly divided into true and false vertebra; the former constituting the long upper pyramid, which has its base below; while the false vertebras make the shorter lower pyra- mid, whose base is above. THE VERTEBRAE. 121 True Vertebra. The true vertebra are the twenty-four upper bones of the spine, on which the several motions of the trunk of our bodies are per- formed. Their name is derived from the Latin verb vertere. Each of these vertebras is composed of its body and pro- cesses. The body is the thick spongy forepart, which is convex before, concave backwards, horizontal and flat in most of them above and below. Numerous small holes, especially on the fore and back part of their surface, giving passage to their vessels, and allow the ligaments to enter their substance. The edges of the body of each vertebras are covered, especially at the forepart, with a ring of bone firmer and more solid than the substance of the body any where else. These rings seem to be joined to the vertebras in the form of epiphyses. They are of great use in preventing the spongy bodies from being broken in the motions of the trunk. Between the bodies of each two adjoining vertebras, a sub- stance between the nature of ligament and cartilage is inter- posed; which seems to consist of concentrical curved fibres, when it is cut horizontally; but when it is divided perpendicularly, the fibres appear oblique and decussating. The outer part of these intervertebral ligaments is the most solid and hard; and they gradually become softer till they are almost in the form of a glairy liquor in the centre. The external fibrous part of each' is capable of being greatly extended, and of being compressed into a smaller space, while the middle fluid part is incompres- sible, or nearly so. The middle point is therefore a fulcrum or pivot, on which the motion of a ball and socket may be made, with such a gradual yielding of the substance of the ligament, in whatever direction our spines are moved, as saves the body from violent shocks, and their dangerous consequences. This ligamento-cartilaginous substance is firmly fixed to the horizon- tal surfaces of the bodies of the vertebras, to connect them; in which it is assisted by a strong membranous ligament, which vol. i. 11 122 THE VERTEBRA lines all their concave surface, and by a still stronger ligament that covers all their anterior convex surface. The elastic substance seems to be in a state of compression by the exterior ligament and the bones; for, if a section be made through a portion of the vertebras and the intervertebral sub- stance, this substance will expand, so that its surface will be much higher than that of the vertebras. It is so elastic, and so much confined, in some subjects, that a sharp knife, if plunged into it will be gradually ejected when the hand is withdrawn. The bodies of the vertebras are, with some exceptions, smaller and more solid above, but more spongy as they descend. The cartilages between them are thick, and the surrounding liga- ments are strong in proportion to the size of the vertebras. By this disposition, the greatest weight is supported on the broadest, best secured base, and the middle of the body is allowed a large and secure motion. From each side of the body of each vertebras, a bony bridge is produced backwards, and to one side; from the posterior end of which one slanting process rises, and another descends. The smooth, and generally the flattest side of each of these four pro- cesses is covered with a smooth cartilage; and the two lower processes of each upper vertebras are fitted to and articulated with the two upper processes of the vertebrae below, having their ar- ticular ligaments fixed into the rough line round their edges. These processes are termed the oblique or articulating. From between the oblique processes of each side, another pro- cess extends laterally, which is called the transverse. From the back part of the roots of the two oblique processes, and of the transverse process of each side, a broad oblique bony plate is extended backwards : where these meet, the seventh pro- cess of the vertebras takes its rise, and stands out backwards. This being generally sharp-pointed and narrow-edged, it has therefore been called spinal process; from which this whole chain of bones has got its name. Besides the common ligament which lines all the internal sur- face of the spinal processes as well as of the bodies, particular THE VERTEBRAE 123 ligaments connect the bony bridges and processes of the conti- guous vertebras together. The substance of the processes is considerably stronger and firmer, and has a thicker external plate than the bodies of the vertebras themselves. The seven processes form a concavity at their forepart, which, joined to the one at the back part of the bodies, make a great hole ; and when the vertebras are placed upon each other in their natural order, these holes form a long tube for containing the spinal marrow. In the upper and lower edge of each lateral bridge, there is a notch. These are so adapted to each other in the contiguous vertebras, as to form a round hole in each side, between each two vertebras, through which the nerves proceed from the spinal mar- row, and its blood-vessels pass. The articulations of these two vertebras are consequently double; for their bodies are joined by the intervening cartilage above described; and their oblique processes, being tipped with cartilages, are so connected by their ligaments as to allow at small degree of motion on every side. Hence, it is evident that their centre of motion is altered in different positions of the trunk: for, when we bow forwards, the weight bears entirely on the bodies of the vertebras; if we bend back, the oblique pro- cesses support it; if we recline to one side, we rest upon the oblique processes of that side and part of the bodies; if we stand erect all the bodies and oblique processes have their share in our support. The true vertebra are divided into three classes, which agree with each other in their general structure, but are distinguished by several peculiarities. These classes are named Cervical, Dorsal, and Lumbar. The cervical are the seven uppermost vertebras; which are distinguished from the rest by these marks: their bodies are smaller and more solid than any others; and are flattened on the front surface. They are also flat behind, where small pro- cesses rise, to which the internal ligaments are fixed. The up- 124 CERVICAL VERTEBRAE. per surface of the body of each vertebras is made hollow, by a slanting thin process which is raised on each side. The lower surface is also hollowed, but in a different manner; for here the posterior edge is raised a little, and the anterior one is consider- ably extended. Hence, the cartilages between these vertebras are firmly connected, and their articulations are secure. These cartilages are thick, especially at their forepart; which is one reason why the vertebras project forward as they descend, and" have the larger motion. Their oblique processes more justly deserve that name than those of any other vertebras. They are situated slanting; the upper ones having their smooth and almost flat surfaces facing obliquely backwards and upwards; while the inferior oblique processes have these surfaces facing obliquely forwards and downwards. The transverse processes of these vertebras are framed in a dif- ferent manner from those of any other bones of the spine; for, besides the common transverse process rising from between the oblique processes of each side, there is a second one that comes out from the side of the body of each vertebras; and these two processes, after leaving a circular hole for the passage of the vertebral artery and vein, unite and form a groove on their up- per surface to protect the nerves that pass in it. They termi- nate obtusely on each side, for the insertion of muscles. The spinal processes project backwards almost horizontally. They are shorter than those of any other vertebras, and are forked or double at their ends; they therefore allow a more con- venient insertion to muscles. The thick cartilages between the bodies of these cervical ver- tebras, the obliquity of their oblique processes, and the shortness and horizontal situation of their spinal processes, all conspire to allow them large motion. The holes between the bony cross bridges, for the passage of the nerves from the spinal marrow, have their largest share formed in the lowest of the two vertebras, to which they are common. CERVICAL VERTEBRAE 125 So far most of the cervical vertebras agree; but they have some particular differences, which require a separate conside- ration. The first, from its use in supporting the head, has the name of atlas. Contrary to all the other vertebras of the spine, it has no body; but, instead of it, there is a bony arch. In the convex forepart of this arch a small rising appears; and on each side of this protuberance, a small cavity may be observed. The upper and lower parts of the arch are rough and unequal, where the ligaments that connect this vertebra to the os occipitis, and to the second vertebra, are fixed. The back part of the arch is concave, smooth, and covered with a cartilage, in a recent sub- ject, to receive the tooth-like process of the second vertebra. On each side of it a small rough sinuosity may be remarked, where the ligaments going to the sides of the tooth-like process of the following vertebra are fastened; and on each side a small rough protuberance and a depression is observable, where the transverse ligament, which secures the tooth-like process in the sinuosity, is fixed, and hinders that process from injuring the me- dulla spinalis in the flexions of the head. The atlas has as little spinal process as body; but, instead of it, there is a large bony arch, that the muscles which pass over this vertebra at that place might not be hurt in extending the head. On the posterior and upper part of this arch, there are two depressions, where the recti postici minores muscles take their rise ; and at the lowTer part are two other sinuosities, into which the ligaments that connect this bone to the following one are fixed. The superior oblique processes, of the atlas are large, and more horizontal than those of any other vertebra. They form an ob- long concave surface which has an internal aspect, and corre- sponds exactly with the articulating surface on the external side of each condyle of the os occipitis. Under the external edge of the posterior part of each of these cavities is the fossa, or deep open channel, in which the vertebral arteries make the circular turn, as they are about to enter the great foramen of the occipi. 11* j26 CERVICAL VERTEBRAE. tal bone, and where the tenth pair of nerves go out. In some subjects, this fossa is covered with bone. The inferior oblique processes, extending from within outwards and downwards, are large, circular, and slightly concave. So that this vertebra, con- trary to the other six, receives the bones with which it is articu- lated, both above and below. The transverse processes of this vertebra are not much hol- lowed or forked; but are longer and larger than those of any other vertebras of the neck, for the origin and insertion of seve- ral muscles; and, therefore, those muscles which move this ver- tebra on the second, have a considerable lever to act with, be- cause of the distance of their insertion from the axis of revolu- tion. The hole for the medulla spinalis is larger in the atlas than in any other vertebra, not only on account of the medulla being largest here, but also to prevent its being hurt by the motions of this vertebra on the second. This large hole, and the long trans- verse processes, make this the broadest vertebra of the neck. The condyles of the os occipitis move forwards and back- wards in the superior oblique processes of this vertebra; but from the figure of the bones forming these articulations, it is evident that very little motion can here be allowed to either side; and there must be still less circular motion. The second vertebra of the neck is called dentata. It is somewhat of a pyramidal figure, being large, and extended downwards, espe- cially in front, to enter into a hollow of the vertebra below; while the upper part has a long process, with its extremity formed into an obtuse point. This process, from its supposed resemblance to a tooth, has given name to the vertebra. The side of it, on which the concave surface of the anterior arch of the first ver- tebra plays, is convex, smooth, and covered with a cartilage; and it is of the same form behind, to accommodate the ligament which is extended transversely from one rough protuberance of the first vertebra to the other, and is cartilaginous in the middle. A ligament likewise goes out in an oblique transverse direction, from each side of the processus dentatus, to be fixed at its other end to the first vertebra, and to the occipital bone ; and another CERVICAL VERTEBRAE. 127 ligament rises up from near the point of the process to the os occipitis. The superior oblique processes of the vertebra dentata are large, circular, very nearly in a horizontal position, and slightly convex, to be adapted to the inferior oblique processes of the first vertebra. The inferior oblique processes of this vertebra answer exactly to the description given of those common to all the cervical vertebras. The transverse processes of the vertebra dentata are short, very little hollowed at their upper part, and not forked at their ends ; and the canals through which the vertebral arteries pass, are reflected outwards about the middle of each process, so that the course of these vessels may be directed towards the trans- verse processes of the first vertebra. Had this curvature of the arteries been made in a part so movable as the neck is, while they were not defended by a bone and placed in the cavity of that bone, scarce a motion could have been performed without the utmost hazard of compression. This is the third instance of similar mechanism in cases of sudden curvature of arteries. The first is the passage of the carotids through the temporal bones; and the second is that lately described, where the verte- bral arteries turn round the oblique processes of the first verte- bra, to come at the great hole of the occipital bone. The spinal process of this vertebra is thick, strong, and short, to give sufficient origin to the musculi recti majores and obliqui inferiores, and to prevent the contusion of these and other mus- cles in pulling the head back. The four cervical vertebras which are next in order have nothing particular in their structure, but agree with the general description. The seventh vertebra approaches the form of those of the back, having the upper and lower surfaces less excavated than the others. The oblique processes are more perpendicular; and the spinal as well as transverse processes are without bifur- cation. After an examination of the condyles of the os occipitis, and of the whole structure of the atlas and vertebra dentata, it will 128 DORSAL VERTEBRAE. be evident, that the flexion and extension of the head, or its mo- tion backwards and forwards, is effected by the movements of the condyles of the occipital bone on the atlas; and that in the rotation of the head, the atlas revolves to a certain degree round the processus dentatus of the second vertebra: the head neces- sarily moving with it. The twelve dorsal may be distinguished from the other ver- tebra of the spine by the following marks. Their bodies are of a middle size, between those of the neck and loins. They are more convex before than either of the other two sorts; and are flattened laterally by the pressure of the ribs, which are inserted into small cavities formed in their sides. This flatness of their sides, which makes the figure of these vertebras almost a half oval, is of great use; as it af- fords a firm articulation to the ribs, allows the trachea arteria to divide at a small angle, and the other large vessels to run secure from the action of the vital organs. Their bodies are more con- cave behind than any of the other two classes. The upper and lower surfaces are horizontal. The cartilages interposed between the bodies of these verte- bras are thinner than in any other of the true vertebras; and contribute to the concavity of the spine in the thorax, by being thinnest at their forepart. The oblique processes are placed almost perpendicularly: the upper ones slanting but a little forwards, and the lower ones slanting as much backwards. The convexity or concavity is not so remarkable as to require particular notice. Between the oblique processes of opposite sides several sharp processes stand out from the upper and lower parts of the plates which join to form the spinal processes: into these sharp processes strong liga- ments are fixed for connecting the vertebras. The transverse processes of the dorsal vertebras are long, thicker at their ends than in the middle, and turned obliquely backwards, which may be owing to the pressure of the ribs; the tubercles of which are inserted into a depression near the end of these processes. DORSAL VERTEBRAE. 129 The spinal processes are long, small-pointed, and sloping down- wards and backwards. From their upper and back part a ridge rises, which is received by a small channel in the forepart of the spinal process immediately above, which is here connected to it by a ligament. The canal for the spinal marrow is here more circular, but corresponding to the size of that chord, is smaller than in any of the other vertebras; and a larger share of the holes in the bony bridges for the transmission of the nerves, is formed in the vertebra above than in the one below. The connexion of the dorsal vertebras to the ribs, the thinness of their cartilages, the erect situation of the oblique processes, the length, sloping, and connexion of the spinal processes, all contribute to restrain these vertebras from much motion, which might disturb the actions of the heart and lungs; and in conse- quence of the little motion allowed here, the intervertebral car- tilages sooner shrivel, by becoming more solid; and therefore the first remarkable curvature of the spine observed, as people advance to old age, is in the least stretched vertebras of the back; or old people first become round-shouldered. The bodies of the four uppermost dorsal vertebras deviate from the rule, and the vertebras become larger as they descend; for the first of the four is the largest, and the other three below gradually become smaller, to allow the trachea and large vessels to divide at smaller angles. The two uppermost vertebras of the back, instead of being very prominent forwards, are flattened by the action of the mus- culi longi colli and recti majores. The proportional size of the two little depressions in the body of each vertebra for receiving the heads of the ribs seems to vary in the following manner: the depression on the upper edge of each vertebra decreases as far down as the fourth, and, after that, increases. The transverse processes are longer in each lower vertebra to the seventh or eighth, with their smooth surfaces, for the tuber- cles of the ribs, facing gradually more downwards; but after- j go LUMBAR VERTEBRAE. wards, as they descend, they become shorter, and the smooth surfaces are directed more upwards. The spinous processes of the vertebras of the back become gradually longer and more slanting from the first, as far down as the eighth or ninth vertebra; from which they manifestly turn shorter and more erect. The first vertebra, besides an oblong hollow in its lower edge, that assists in forming the cavity wherein the second rib is re- ceived, has the whole cavity for the head of the first rib formed in it. The eleventh often has the whole cavity for the eleventh rib in its body, and wants the smooth surface on each transverse process. The twelfth always receives the whole head of the last rib, and has no smooth surface on its transverse processes, which are very short. The smooth surfaces of its inferior oblique pro- cesses face outwards as the lumbar do. In general the upper vertebras of the back lose gradually their resemblance to those of the neck, and the lower ones approach gradually to the figure of the lumbar. The lumbar vERTEBRiE are five bones, that may be distin- guished from any others by these marks: 1. Their bodies, though of a circular form at their forepart, are somewhat oblong from one side to the other. The epiphysis on their edges are larger; and therefore the upper and lower surfaces of their bo- dies are more concave than in the vertebras of the back. 2. The cartilages between these vertebras are very thick, and render the spine convex within the abdomen, by their great thickness anteriorly. 3. The oblique processes are strong and deep; the superior, which are concave, facing inwards, and the convex inferior ones facing outwards; and therefore each of these ver- tebras receives the one above it, and it is received by the one below, which is not so evident in the other two classes already described. 4. Their transverse processes are small, long, and almost horizontal, for allowing large motion to each bone, and sufficient insertion to muscles, and for supporting and defending LUMBAR VERTEBRA. joj the internal parts. 5. Between the roots of the superior oblique and transverse processes, a small protuberance may be observed, where some of the muscles that raise the trunk of the body are inserted. 6. Their spinal processes are strong, straight, and horizontal, with broad flat sides, and a narrow edge above and below ; this last being depressed on each side, by muscles; and, at the root of these edges, we see rough surfaces for fixing the ligaments. 7. The medullary canal is larger in these bones than in the dorsal vertebras. 8. The holes for the passage of the nerves are more equally formed out of both the contiguous ver- tebras than in the other classes; the upper one furnishes, how- ever, the larger share of each hole. The thick cartilages between these lumbar vertebras, their deep oblique processes, and their erect spinal processes, are all fit for allowing large motion, though it is not so great as what is performed in the neck; which appears from comparing the arches which the head describes when moving on the neck or the loins only. The lumbar vertebras, as they descend, have their oblique processes at a great distance from each other, and facing more backward and forwards. The transverse and spinal processes of the first and last lum- bar vertebras are shorter than those in the middle. The epiphyses round the edges of the bodies of the lumbar vertebras are most raised in the two lowest; which consequently make them appear hollower in the middle than the others are. The body of the fifth vertebra is rather thinner than that of the fourth. The spinal process of this fifth is smaller, and the oblique processes face more backwards and forwards, than those of any other lumbar vertebras. In consequence of this particular construction, the spine is capable of flexion, principally in an interior and lateral direction, and also of extension. It ought to be remarked, that during flexion it forms a curve, and not an angle; for, in the last case, the spinal marrow would be more or less compressed. The cervical vertebras have most motion, and the dorsal the 132 FALSE VERTEBRAE. least. This circumstance is fully explained by the form of the different parts of these vertebras, and the difference in the thick- ness of the intervertebral substance. The necessity of fixing the dorsal vertebras is very evident: as their motion would greatly interfere with the motion of the ribs in respiration. The lumbar vertebras have more motion than is commonly supposed; for, in addition to a certain degree of flexion, they perform a species of rotation or twisting, which is very observa- ble in persons who are diseased in one of their hip joints; such persons move their whole pelvis, by a rotation of the lumbar vertebras, to avoid moving the diseased joint. —The first cause, the predisposing cause of spinal curvatures is the relative feebleness of the spinal column, compared to the forces exercised upon it, at the same time that the bones, by a premature increase, or by a lesion of nutrition as yet little known, do not acquire the degree of solidity necessary to resist the action of the muscles, and especially the weight of the viscera contained in the head, chest, &c. There results from this neces- sarily a curvature in one of the points of the lever, and in some one direction. —The direction of the curvature will be determined by the ine- quality of the forces brought into play around it. For without this inequality, the curvature would be direct; that is, straight. It is ordinarily to the left that it has place, because the muscles of the right side, stronger than those of the left, draw the verte- bra in that direction, as Ludwig has said.— False Vertebra. The lower pyramid or under part of the spine, consists of one large triangular bone, called the os sacrum, and of some small bones, denominated the os coccygis. These bones are called the false vertebras, because the sacrum in young subjects is composed of five distinct bones, each of which has some resemblance to a vertebra; but they are com- pletely united in the adult, and form but one bone, which is sup- posed to have been denominated sacrum, because it was offered in sacrifice by the ancients. OS SACRUM. 133 The os sacrum is of a triangular form, with its base upwards. It is concave anteriorly, and convex posteriorly. The middle of the bone, when viewed anteriorly, appears to be composed of the bodies of five vertebras, united to each other, and their union is marked by four transverse lines. At the two extremities of each of these lines, are large round holes, which communicate with the vertebral cavity of the bone. On the exterior sides of these holes the surface is free from any marks of the original separation. The middle of the upper surface, or base of the bone, is formed for articulating with the last lumbar vertebra, and has two oblique processes, with a groove in each side, which forms part of the foramen for transmitting the twenty-fourth pair of nerves. The back part of the os sacrum is rough and convex; in the middle there are commonly three processes similar to the spinous processes of the lumbar vertebras, and a fourth, which is much smaller. Below this, there is a deficiency of the bony spine, and the vertebral cavity is consequently open behind, but the sides of the canal continue lower down. On each side of the spinous processes are four smaller holes, which are opposite to the larger holes on the anterior surface. Between the spinous processes and the anterior part, which re- sembles the bodies of vertebras, is the continuation of the vertebral cavity which contains the spinal marrow. From the cauda equina, contained in this cavity, the great nerves of the lower extremities pass off, through the large holes on the anterior sur- face, and some small nerves through the posterior holes. In some bones the spinous processes are entirely deficient, and the cavity above mentioned is completely open behind; but the contained parts are defended by strong membranes. The anterior part of each lateral surface is covered by a plate of cartilage, and articulated to the os ilium. The posterior part is rough, and perforated by the fibres of the strong ligaments, which are inserted into it. On the posterior surface of the sacrum, the sides of the open vol. i. 12 134 os COCCYGIS. part of the vertebral canal terminate, so as to form a notch through which passes the twenty-ninth pair of nerves. The os sacrum is very spongy, and is lighter in proportion to its bulk than any bone in the body: it is defended by the muscles that cover it, and the ligaments which adhere to it. It is articulated, above, to the last lumbar vertebra; below, to the os coccygis ; and on the sides, to the ossa ilia. That triangular chain of bones depending from the os sacrum, in which each bone becomes smaller as it descends, till the last ends in a small tubercle, is called os coccygis. It is convex be- hind, and concave before; from which crooked pyramidal figure, which was thought to resemble a cuckoo's beak, the name is derived. There are four pieces in people of middle age. In children, they are almost wholly cartilaginous. In old subjects, all the bones are united, and become frequently one continued bone with the os sacrum. The highest of the four bones is the largest, with shoulders extended farther to each side than the end of the os sacrum; which enlargement may serve as a distinguishing mark to fix the limits of either bone. The upper surface of this bone is a little hollow. From the back of that bulbous part called its shoulders, a process often rises up on each side, to join with the os sacrum. Sometimes these shoulders are joined to the sides of the open end of the vertebral canal, to form the hole in each side common to these two bones, for the passage of the twenty- ninth pair of spinal nerves. Immediately below the shoulders of the os coccygis, a notch may be remarked on each side, where the thirtieth pair of the spinal nerves passes. The lower end of this bone is formed into a small head, which very often is hollow in the middle. The three lower bones gradually become smaller, an~! are spongy, but are strengthened by a strong ligament, which covers and connects them. Their ends, by which they are articulated, are formed in the same manner as those of the first bone. Between each of these four bones of young subjects a carti- lage is interposed; therefore their articulation is analogous to VERTEBRAL CAVITY. igc that of the bodies of the vertebras of the neck; for the lower end of the os .sacrum, and of each of the three superior bones of the os coccygis, has a small depression in the middle; and the upper part of all the bones of the os coccygis is a little concave, and, consequently, the interpo-ed cartilages are thickest in the middle, to fill up both cavities; by which they connect the bones more firmly. When the cartilages ossify, the upper end of each bone is formed \ to a cavity, exactly adapted to the protuberant lower end of the bo. e immediately above. From this sort of articula- tion, it is evident that, unless when these bones grow together, all of them are capable of motion; of which the first and second enjoy the largest share. The lower end of the fourth bone terminates in a rough point, to which a cartilage is appended. To the sides of these bones of the os coccygis, the coccygasi muscles, and part of the levatores ani, and of the glutasi maximi, are fixed. The connexions of these bones hinder them from being moved to either side; and their motion backwards and forwards is much confined : yet, as their ligaments can be stretched by a considerable force, it is of great advantage in the excretion of the fasces alvinas, and much more in child-bearing, that these bones should remain movable; and the right management of them, in delivering women, is very important. The mobility of the os coccygis diminishing as people advance in age, especially when its ligaments and cartilages have not been kept flexible by being stretched, is, probably, one reason why women, who are advanced in years before they marry, have generally difficult parturition. These bones serve to sustain the intestinum rectum; and, therefore, are curved forwards; by which they are preserved, as well as the muscles and teguments, from any injury when sitting with the body reclined back. The Vertebral Cavity for containing the Spinal Marrow. The canal, formed by the foramina of the different vertebras, when these bones are placed in their natural order, extends from 130 THE THORAX—RIBS. the great occipital foramen to the end of the sacrum. Its direc- tion varies with the different curvatures of the spine, and its figure and diameter are also very different in different places. In the cervical vertebras, it is largest, and nearly triangular in form; in the dorsal, it is much smaller and almost cylindrical; in the lumbar, it is somewhat enlarged, and approaches again to the triangular figure; in the sacrum, it is broad, but flat, and diminishes gradually, so as to assume the form of a long triangle. It has a ligamentous lining, which will be described, when an account is given of the fresh bones and their ligaments. The Thorax. The thorax resembles a flattened cone, cut away obliquely at its basis; and regularly truncated at its apex. It is formed by the dorsal vertebras behind, the ribs on the sides, and the sternum before. The Ribs Are long crooked bones, placed in an oblique direction down- wards as respects the back-bone. Their number is generally twelve on each side; though sometimes eleven or thirteen have been found. They are convex externally, and concave internally. They are made smooth by the action of the contained parts, which, on this account, are in no danger of being hurt by them. The ribs approach towards a round form at their extremities, near the vertebras. Farther forwards they are flat and broad, and have an upper and lower edge; each of which is made rough by the action of the intercostal muscles inserted into them. These muscles being all of nearly equal force, and equally stretched in the interstices of the ribs, prevent the broken ends of these bones, in a fracture, from being removed far out of their natural place, to interrupt the motion of the vital organs. The upper edge of the ribs is more obtuse, and rounder than the lower, which is deepened on its internal side by a long fossa, for lodging the intercostal vessels and nerves: on each side of which there is a ridge, to which the intercostal muscles are fixed. The THE RIBS. I37 fossa is not observable at the ends of the ribs; for, at the poste- rior, or root, the vessels have not yet reached the bones; and, at the fore end, they are split away into branches, to serve the parts between the ribs. From this situation of the blood-vessels, has originated the rule adopted by surgeons, that the incision, in cases of empyema, &c. should be made midway between the spine and sternum, and that the lower edge of the upper rib should be avoided. At the posterior end of each rib, a little head is formed, which is divided by a middle ridge into two flat or hollow surfaces; the lowest of which is generally the broadest and deepest. The two surfaces are joined to the bodies of two different vertebras, and the ridge forces itself into the intervening cartilages. A little way from this head, we find, on the external surface, a small cavity, where mucilaginous glands are lodged; and round the head, the bone appears spongy, where the capsular ligament of the articulation is fixed. Immediately beyond this, a flattened tubercle rises, with a small cavity at its root, which is surrounded by a roughness, for the articulation of the rib with the trans- verse process of the lowest of the two vertebras, with which the head of the rib is joined. Advancing farther on this external surface, another smaller tubercle may be observed in most cases, into which ligaments connecting the ribs to each other, and to the transverse processes of the vertebras and portions of the longissimus dorsi, are inserted. Beyond this, these bones are made flat by the sacro-lumbalis muscle, which is inserted into the part of this flat surface farthest from the spine, where each rib makes a considerable curve, called by some its angle. Then the rib begins to turn broad, and continues so to its anterior end, which is hollow and spongy, for the reception of, and firm coali- tion with, the cartilage that runs thence to be inserted into the sternum, or to be joined with some other cartilage. In adults, the cavity at this end of the ribs is generally smooth. The substance of the ribs is spongy, cellular, and only covered with a very thin external lamellated surface, which increases in thickness and strength as it approaches the vertebras. 12* 138 THE RIBS To the fore end of each rib a long, broad, and strong cartilage is fixed, which reaches thp sternum, or is joined to the cartilage of the next rib. This course, however, is not in a straight line with the rib: for the cartilages generally make a considerable flexure, the concave part of which is upwards; therefore, at their insertion into the sternum, they make an obtuse angle above, and an acute one below. These cartilages are of such a length as never to allow the ribs to come to a right angle with the spine; but they keep them situated so obliquely as to make the angle very considerably obtuse above, till a force exceeding the elasticity of the cartilage is applied. These cartilages, as all others, are firmer and harder internally than they are on their external surface; and, sometimes, in old people, all their middle substance becomes bony, while a thin cartilaginous lamella ap- pears externally. The ossification, however, begins frequently at the external surface. The greatest alternate motions of the cartilages being made at their great curvature, that part remains frequently cartilaginous after all the rest is ossified. The ribs then are articulated at each end, and that behind is doubly joined to the vertebras; for the head is received into the cavities of two bodies of the vertebras, and a larger tubercle is received into the depression in the transverse process of the lower vertebras. When we examine the double articulation, we must immediately see, that no other motion can here be allowed than upwards and downwards. Since the transverse process hinders the rib to be thrusted back, the resistance of the sternum on the other side prevents the ribs coming forward; and each of the two joints, with the other parts attached, oppose its turn- ing round. But then it is likewise as evident, that even the mo- tion upwards and downwards can be but small in any one rib at the articulation itself. But as the ribs advance forwards, the distance from their centre of motion increasing, the motion must be larger; and it would be very conspicuous at their anterior ends, were they not resisted there by the cartilages which yield so little, that the principal motion is performed by the middle part of the ribs, which turns outwards and upwards, and occa- THE RIBS. 139 sions the twist remarkable in the long ribs at the place near their fore end where they are more resisted. The ribs differ from each other in the following respects: The upper rib is the most crooked; and as they descend they become straighter. Their obliquity, with respect to the spine, increases as they descend, so that though their distances from each other are nearly equal at their back part, yet at their fore ends the distances between the lower ribs must increase. In consequence of this increased obliquity of the lower ribs, each of their cartilages makes a greater curve in its progress from the rib towards the sternum; and the tubercles that are articu- lated to the transverse processes of the vertebras, have their smooth surfaces gradually facing more upwards. The ribs be- coming thus more oblique, while the sternum advances forwards in its descent, makes the distance between the sternum and the anterior end of the lower ribs greater than between the sternum and the ribs above; consequently, the cartilages of those ribs that are joined to the breast bone are longer in the lower than in the higher ones. These cartilages are placed nearer to each other as the ribs descend, which occasions their curvature to be greater. The length of their ribs increases from the first and upper- most rib, as far down as the seventh; and from that to the twelfth, it gradually diminishes. The superior of the two sur- faces, by which the ribs are articulated to the bodies of the ver- tebras, gradually increases from the first to the fourth rib, and is diminished after that in each lower rib. The distance of their angles from the heads always increases as they descend to the ninth, because of the greater breadth of the sacro-lumbalis muscle. The ribs are commonly divided into true and false. The true ribs are the seven uppermost of each side. Their cartilages are all gradually longer as they descend, and are joined to the breast bone: so that, being pressed constantly be- tween two bones, they are flattened at both ends; and are thicker, harder, and more liable to ossify than the other carti- 140 THE RIBS lages that are not subject to so much pressure. These bones include the heart and lungs; and therefore are called true ribs. The five inferior ribs of each side are the false, whose car- tilages do not reach to the sternum; but on this account having less pressure, their substance is softer. To these five ribs the circular edge of the diaphragm is connected. The first rib of each side is so situated, that the flat sides are above and below, while one edge is placed inwards, and the other outwards, or nearly so; therefore sufficient space is left above it for the subclavian vessels and muscles ; and the broad concave surface is opposed to the lungs. But in consequence of this situation, the channel for the intercostal vessels is not to be found. The head of this rib is not divided into two plane sur- faces by a middle ridge, because it is only articulated with the first vertebra of the thorax. Its cartilage is frequently ossified in adults, and is united to the sternum at right angles. This first rib frequently has a ridge rising near the middle of its posterior edge, where one of the heads of the scalenii muscles rises. Farther forward it is flattened, or sometimes depressed by the clavicle. The position of the second rib is such that its two broad sur- faces have oblique aspects, inward and downwards, outwards, and upwards, so as to make the surface of the thorax uniform: and it may be observed of all the ribs, that the aspect of their surfaces is varied upon this principle, according to their situation in the thorax. The sixth, seventh, and eighth ribs have their cartilages nearly contiguous. They are frequently joined to each other by cross cartilages; and frequently the cartilages of the eighth, ninth, and tenth, are connected to the former, and to each other by firm ligaments. The eleventh, and sometimes the tenth rib, has no tubercle for its articulation with the transverse process of the vertebra, to which it is only loosely fixed by ligaments. The fossa, in its lower edge, is not so deep as in the upper ribs; because the ves- sels run more towards the interstice between the ribs. Its front THE STERNUM. 141 end is smaller than its body; and its short small cartilage is but loosely connected to the cartilage of the rib above. The twelfth rib is the shortest and straightest. Its head is only articulated with the last vertebra of the thorax; and therefore is not divided into two surfaces. This rib is not joined to the transverse process of the vertebra, and therefore has no tubercle, being often pulled necessarily inwards by the diaphragm, which an articulation with the transverse process would not have allowed. The fossa is not found at its upper edge, because the vessels run below it. The forepart of this rib is smaller than its middle, and has only a very small pointed cartilage fixed to it. To its whole internal side the diaphragm is connected. The Sternum Is the broad flat bone, in the front part of the thorax. In adults it is composed of three pieces, which easily separate after the cartilages connecting them are destroyed. The two lower pieces are frequently found intimately united; and very often, in old people, the sternum is a continued bony substance from one end to the other; though we still observe two, some- times three, transverse lines on its surface; which are marks of the former divisions. The sternum, considered as one bone, is broadest and thickest above, and smaller as it descends. The internal surface of this bone is somewhat concave for enlarging the thorax: but the convexity on the external surface is not so conspicuous, because the sides are pressed outwards by the true ribs; the round heads of whose cartilages are received into seven smooth pits, formed in each side of the sternum, and are kept firm there by strong ligaments, which, on the external surface, have a parti- cular radiated texture. The pits, at the upper part of the sternum, are at the greatest distance one from another, and as they descend, are nearer; so that the two lowest are contiguous. The substance of the breast bone is cellular, with a very thin external plate, especially on its internal surface, where we may frequently observe a cartilaginous crust spread over it. On both 142 THE STERNUM. surfaces, however, a strong ligamentous membrane is closely braced; and the cells of this bone are so small, that a consider- able quantity of osseous fibres must be employed in the com- position of it. Whence, with the defence which the muscles give it, and the movable support it has from the cartilages, it is sufficiently secured from being broken: for it is strong by its quantity of bone; its parts are kept together by ligaments; and it yields enough to elude considerably any violence offered. The three pieces which compose this bone are very different from each other. The first piece resembles a triangle, with the corners cut off The upper edge of it is thick, and has a regular depression in the middle, to accommodate the trachea. On each side of this depression is a superficial cavity, which, on viewing it trans- versely, from before backwards, appears a little convex. Into these cavities the ends of the clavicles are received. Imme- diately below them, the sides of this bone become thinner ; and in each a superficial cavity, or a rough surface is to be seen, where the first ribs are received or joined to the sternum. In the side of the under end of this first bone, the half of the pit for the second rib on each side is formed. The upper part of the surface behind is covered with a strong ligament, which secures the clavicles ; and is afterwards to be more particularly taken notice of. The second, or middle division of this bone, is much longer, narrower, and thinner, than the first; but, excepting that it is a little narrower above than below, it is nearly uniform in its dimensions of breadth or thickness. In the sides of it are com- plete pits for the third, fourth, fifth, and sixth ribs, and one half of the pits for the second and seventh; the lines, which are marks of the former division of this bone, being extended from the middle of the pits of one side, to the middle of the corre- sponding pits of the other side. Near its middle an unossified part of the bone has sometimes been found; which, freed of the ligamentous membrane or cartilage that fills it, is described as a hole. When the cartilage between this and the first bone is not THE STERNUM. 143 ossified, a manifest motion of this upon the first may be observed in respiration ; or in raising the sternum, by pulling the ribs up- wards ; or distending the lungs with air, in a recent subject. The third bone is much less than the other two, and has only one half of the pit for the seventh rib formed in it; wherefore it might be reckoned only an appendix of the sternum. In young subjects it is always cartilaginous, and is better known by the name of cartilago-xiphoides or ensiformis, than any other. This third bone is seldom of the same figure, magnitude, or situation, in any two subjects; for, sometimes, it is triangular; with one of the angles below, and perpendicular to the middle of the upper side, by which it is connected to the second bone. In other persons, the point is turned to one side; or obliquely for- wards or backwards. Frequently it is nearly of an equal breadth, and often it is bifurcated ; sometimes, also, it is unossified in the middle. In the greatest number of adults, it is ossified, and tipped with a cartilage ; in some, one half of it is cartilaginous; and in others, it is all in a cartilaginous state. The sternum is joined by cartilages to the seven upper ribs, except when the first coalesce with it. It is also articulated with the clavicles. It contributes to the formation of the cavity of the thorax, and supports the mediastinum. As a movable fulcrum for the ribs, it assists in respiration; and it affords origin and insertion to several muscles. The movement of the Ribs and Sternum in inspiration. The ribs and their cartilages are articulated to the spine behind, and the sternum before, in a way which admits of a compound motion. They are drawn from a position which slopes obliquely down- wards and forwards, into one which is more horizontal; and the posterior extremity of each rib, which is the centre of this motion, is moved very little, while the anterior extremity moves much more. At the same time, the ribs perform a rotation outwards, upon their extremities connected with the spine and sternum ; in con- 144 THE PELVIS. sequence of which, the middle of each rib is moved outwards to a considerable extent. It is very obvious, that, by these motions, the thorax must be enlarged from side to side, and from behind forwards. As the ribs are raised from the oblique towards the horizontal position, the sternum is necessarily moved forward by them ; and, if this bone does not move upon the first rib, the rib must move to accommodate it: a small motion at the articulation of the rib with the spine, being sufficient to produce considerable motion at the lower end of the sternum. The sternum, therefore, vibrates forward when the ribs are elevated, and backward when they are depressed. In easy respiration, these motions are not very great, for then the enlargement of the thorax appears to be produced by the in- crease of its vertical diameter, in consequence of the descent of the diaphragm; but when the inspirations are very large, and when the descent of the diaphragm is impeded, as in preg- nancy, and in ascites, these motions are very considerable- It ought to be observed, that the first rib has very little motion, except the rotation which favours the motion of the sternum; and that the lower ribs, having no support at their anterior extremities, have no rotation. The Pelvis. The pelvis is the cavity at the lower part of the trunk, formed by the os sacrum, os coccygis, and ossa innominata. The ossa innominata are the two large bones which are con- nected to the sacrum behind, and to each other by the interven- tion of a cartilage in front. Each of the ossa innominata is composed of three portions, in children; and although these are united in adults, so as to form but one bone, yet anatomists have generally considered the bone as divided into its original parts, which are denominated os ilium, os ischium, and os pubis. The original separation is at the acetabulum, or cavity for re- ceiving the head of the os femoris, which is on the outside of the os innominatum. The upper and posterior part of this cavity, OS ILIUM. 145 to the amount of two-fifths, is formed by the os ilium, two-fifths of the inferior portion by the os ischium, and the anterior fifth by the os pubis. The Os Ilium Is the largest of the three portions. Its external surface has been called its dorsum, and the internal concave surface its costa or venter. The semicircular edge at the upper part of the bone, is named the spine ; the external oblique muscle of the ab- domen is inserted into it, and the internal oblique, and the trans- versalis arise from it. The ends of the spine are prominent, and therefore are called processes. At a small distance bel6w the anterior spinous process, is another protuberance, called the inferior anterior spinous process ; and the edge of the bone be- tween these two processes is curved. Below the posterior spinal process, another protuberance is also observable, which is applied closely to the os sacrum. Under this is a large notch, which, with the ligaments that pass from the os sacrum to the os ischium, forms a foramen, through which the great sciatic nerve, the pyriform muscle, and some blood-vessels pass. The external surface, or dorsum, of the os ilium, is greatly undulated by the action of muscles that lie upon it; the gluteus maximus, on the posterior, and the gluteus medius and minimus, on the anterior parts of it. The lower part of this bone, which contributes to the formation of the acetabulum, is the thickest. The internal surface of the os ilium is concave, and supports some of the intestines. From this concave surface a slight con- cavity is continued obliquely forwards, at the inside of the ante- rior inferior spinal process, where part of the psoas and iliacus muscles, with the crural vessels and nerves pass. The large concavity is bounded below by a sharp ridge, which runs from behind forwards; and, being continued with such another ridge of the os pubis, forms a line of partition between the cavities of the abdomen and pelvis. Into this ridge the broad tendon of the psoas parvus is inserted. All the internal surface of the os ilium, behind the continu- vol. i. 13 146 OS ISCHIUM. ance of this ridge, is very unequal: for the upper part is flat, but spongy, where the sacro-lumbalis and longissimus dorsi rise. Lower down, there is a transverse ridge from which ligaments go out to the os sacrum. Immediately below this ridge, the rough unequal cavities and prominences are placed, which are exactly adapted to those described on the side of the os sacrum. In the same manner, the upper part of this rough surface is po- rous, for the firmer adhesion of the ligamentous cellular sub- stance ; while the lower part is more solid, and covered with a thin cartilaginous skin, for its immovable articulation with the os sacrum. From all the circumference of this large unequal surface, ligaments are extended to the os sacrum, to secure more firmly the conjunction of these bones. The passages of the medullary vessels are very conspicuous, both in the dorsum and costa of many ossa ilia; but in others they are inconsiderable. The posterior and lower parts of these bones are thick; but they are generally exceedingly thin and compact at their middle, where they are exposed to the actions of the musculi glutasi and iliacus internus, and to the pressure of the bowels contained in the belly. The substance of the ossa ilia is cellular, except a thin external plate. The Os Ischium, Or hip-bone, is of a middle size, between the two other parts of the os innominatum, and of a very irregular figure. Its extent might be marked by a horizontal line drawn a little below the middle of the acetabulum; for the upper bulbous part of this bone forms rather less than the lower half of that great cavity, and the small leg of it rises to much the same height, on the other side of the great hole, common to this bone and the os pubis. From the upper thick part of the os ischium, a sharp process, called by some authors spinous, stands out backwards, from which chiefly the musculus coccygasus and superior gemellus, and part of the levator ani, rise; and the anterior, or internal, sacro-sciatic ligament is fixed to it. Between the upper part of this ligament and the bones, '' --- r— -' ' ----1 *'--- *"-_ OS PUBIS 147 pyriform muscle, the posterior crural vessels, and the sciatic nerve, pass out of the pelvis. Immediately below this process, is a depression for the tendon of the obturator internus muscle. In a recent subject, this part of the bone serves as a pulley on which the obturator muscle plays with a ligamentous cartilage. Below the depression of the obturator muscle, is the great knob or tuberosity, covered with cartilage or tendon. The up- per part of the tuberosity gives rise to the inferior gemellus muscle. To a ridge at the inside of this, the external, or poste- rior sacro-sciatic ligament is so fixed, that between it, the inter- nal ligament, and the sinuosity of the os ischium, a passage is left for the internal obturator muscle. The upper thick smooth part of the tuber, called by some its dorsum, has tw^o oblique im- pressions on it. The inner one gives origin to the long head of the biceps flexor cruris, and semitendinosus muscles; and the semimembranosus rises from the exterior one, which reaches higher and nearer the acetabulum than the other. The lower, thinner, more scabrous part of the knob, which bends forwards, is also marked with two flat surfaces; whereof the internal is what we lean upon in sitting, and the external gives rise to the largest head of the triceps adductor femoris. Between the ex- ternal margin of the tuberosity, and the great hole of the os in- nominatum, there is frequently an obtuse ridge extended down from the acetabulum, which gives origin to the quadratus femoris. As the tuber advances forwards, it becomes smaller, and is rough for the origin of the musculus transversalis and erector penis. The small leg of it, which mounts upwards to join the os pubis, is rough and prominent at its edge, where the two lower heads of the triceps adductor femoris take their rise. The upper and back part of theos ischium is broad and thick ; but its lower and forepart is narrower and thinner. Its sub- stance is of the structure common to broad bones. The os ilium and pubis, of the same sides, are the only bones which are contiguous to the os ischium. The Os Pubis, The least of the three portions of the os innominatum, is placed at the upper and front part of it. The thick, largest 148 os pubis. part of this bone is employed in forming the acetabulum; from which, becoming much smaller, it is stretched inwards to its fellow of the other side, where it again grows larger, and forms a surface to be connected with the cartilage of its sym- physis and then sends a small branch downwards to join the end of the small leg of the os ischium. The upper surface of each os pubis is broad, near its junction with the cartilage of the sym- physis ; on the internal edge of this surface begins a ridge, which is continued from it along the os ilium, and forms the division be- tween the cavities of the abdomen and pelvis. This ridge is called crista, and includes that on the ilium, linea innominata, or ileo-pectinea. On the anterior and external edge of this surface of the pubis, at a small distance from the cartilage, is a promi- nence or process, called the spine. From this process, another ridge, which is much more obtuse, extends to the acetabulum. The upper surface of the pubis, which is included between these ridges, is concave, for the transmission of the crural vessels, and nerve, and the psoas and iliacus internus muscles. Immediately below the lower ridge, and near the acetabulum, a winding notch is made, which is comprehended in the great contiguous foramen ; but is formed into a hole in the recent sub- ject by a subtended ligament, for the passage of the posterior crural nerve, and artery, and vein. The internal end of the os pubis is rough and unequal, for the firmer adhesion of the thick ligamentous cartilage that connects it to its fellow of the other side. The process which goes down from that to the os ischium is broad and rough before, where the gracilis and upper heads of the triceps adductor femoris have their origin. The substance of the os pubis is the same as that of other broad bones. Between the os ischium and pubis a very large irregular hole is left, which has been called thyroideum. The whole of this foramen, except the notch for the posterior crural nerve, is filled up, in a recent subject, with a strong ligamentous mem- brane, that adheres very firmly to its circumference. From this membrane chiefly, the two external and internal obturator mus- cles take their rise. The great design of this hole, besides ren- dering the bone lighter, is, to ~"~— - -* ■ • acetabulum. 149 rator muscles, and sufficient space for lodging them; that there may be no danger of disturbing the functions of the contained viscera of the pelvis by the actions of the internal; nor of the external being bruised by the thigh bone, especially by its lesser trochanter, in the motions of the thigh inwards: both which in- conveniences must have happened, had the ossa innominata been complete here, and of sufficient thickness and strength, as the fixed point of these muscles. The bowels sometimes make their way through the notch for the vessels at the upper part of this thyroid hole; and this causes a hernia in this place. The acetabulum is situated near the outside of the great fora- men. The margin of this cavity is very high, and is still much more enlarged by the ligamentous cartilage, with which it is tipped in a recent subject; round the base of this margin the bone is rough and unequal, where the capsular ligament of the articulation is fixed. At the upper and back part of the aceta- bulum the margin is much larger and higher than any where else ; which is very necessary to prevent the head of the femur from slipping out of its cavity at this place, where the whole weight of the body bears upon it, and consequently might other- wise thrust it out. As the margin is extended downwards and forwards, it becomes less; and, at the internal lower part, is a deficiency in it; from the one side of which to the other, a liga- ment is placed in the recent subject, under which a large hole is left. Besides this difference in the height of the margin, the acetabulum is otherwise unequal; for the lower internal part of it is depressed below the cartilaginous surface of the upper part, and is not covered with cartilage; into the upper part of this particular depression, where it is deepest, and of a semilunar form, the ligament of the thigh bone, commonly, though impro- perly called the round one, is inserted: while, in its more super- ficial lower part, a mass of adipose matter is lodged. The great- est part of this separate depression is formed in the os ischium. The ossa innominata are joined, at their back part, to each side of the os sacrum, by a sort of suture, with a very thin inter- vening cartilage, which serves to cement these bones together: 13* 150 CAVITY OF THE PELVIS. and strong ligaments go from the circumference of this unequal surface to connect them more firmly. They are connected to- gether at their forepart by the ligamentous cartilage interposed between the two ossa pubis, and therefore have no motion in a natural state, except what is common to the trunk of the body, or to the os sacrum. Considering the great weight that is supported in our erect posture, by the articulation of the ossa innominata with the os sacrum, there is great reason to think, that, if the conglutinated surfaces of these bones were once separated, (without which the ossa pubis cannot move on each other,) the ligaments would be violently stretched, if not torn. Each os innominatum affords a socket (the acetabulum) for the thigh bones to move in; and the trunk of the body rolls so much on the heads of the thigh bones as to allow here the most conspicuous motions of the trunk, which are commonly thought to be performed by the bones of the spine. The form of the cavity of the pelvis, at its upper opening, or brim, is somewhat oval; as a line drawn from one side to the other, is about an inch longer than a line drawn from the back to the front part of it. This margin is well defined by the ridge on the surface of the ossa ilia, and the upper edge of the os pubis; but the margin of the lower opening is very irregular; and it ought to be observed, that the dimensions of this opening are made less by the sacro- sciatic ligaments, than they appear upon an examination of the bare bones. In consequence of the oblique position of the sacrum, sloping downwards and backwards, the position of the pelvis is very oblique. A line drawn through the centre of this cavity, per- pendicular to the plane of the upper orifice, or brim, would not coincide with the vertical diameter of the cavity of the abdo- men, but would pass out of that cavity near the umbilicus. This cavity, and the bones which form it, are different in the two sexes. In women, the brim of the pelvis is wider, and inclines more to the oval form. In men this opening is mo: ': \- CAVITY OF THE PELVIS. 151 The outlet or lower opening of the pelvis is also larger in women. This greater size of the pelvis and its openings, in women, is derived particularly from the following circumstances: The os sacrum is broader, and sometimes straighter than in men. The ossa ilia are flatter, and consequently the ossa ischia are farther apart. The ligamentous cartilage at the symphysis pubis is broader, and shorter. The angle formed by the crura of the ossa pubis with each other, at the symphysis, is much larger. —The pelvis, considered as a whole, is very irregular, though symmetrical in its shape. It has the form of a truncated cone, or a funnel with its base upwards, curved from behind forward with its concavity in front, and is bounded both above and be- low by bony walls of unequal elevation. It is divided by the projection of the base of the sacrum and the two ilio-pectineal lines, into a greater and lesser pelvis, the former of which is above. The dividing line is called the superior strait of the lesser pelvis. The bony walls of the greater pelvis is incom- plete. The boundaries of this cavity, are formed upon the sides by the iliac fossas, and behind by a notch which is nearly filled up, when the last lumbar vertebras is left connected with the sa- crum,* and in front all the wide triangular opening between the anterior superior spine of the ilium of each side and the sym- physis pubis is filled up by the lower part of the abdominal muscles. From the flaring direction of the upper part of the ilia, the diameters of the base of this cavity, or that towards the abdomen, is greater than those opposite the ilio-pectineal lines. —The lesser pelvis, forms nearly an entire bony canal, and which the student is too apt to consider as constituting the whole pelvis. This cavity is larger at its middle than at its extremities. It is bounded behind by the sacrum and coccyx; in front by the symphysis pubis and a part of the obturator foramen; and upon the sides, by the bony surface which corresponds to the cotyloid * The attachment of the lumbar muscles completes this wall behind. 152 DIMENSIONS OF THE PELVIS. cavity. Its superior margin (superior strait,) is regular and ovoidal in its shape. Its longest diameter is transverse. Its in- ferior strait is very irregular, though symmetrical in the form of its bony walls ; and in consequence of the posterior walls of this pelvis being of much greater length than the anterior, presents an oblique cut, which presents slightly forwards, so that if its axis was extended downwards, it would cross just above the middle of the thigh. It is bounded behind, by the point of the coccyx; in front, by the symphysis pubis; and on the side, by the tuberosities of the ischium. The sacro-sciatic notches and the arch of the pubis, filled up by ligaments and soft parts. From the general form of the whole pelvic cavity it will then be obvious, that a body passing through its axis from above down- wards, must advance successively in three directions: 1st, as it passes through the greater pelvis, obliquely backwards; 2d, ver- tically; and 3d, as it passes through the inferior strait, obliquely forwards. —For obstetrical purposes, it is necessary for the student to have precise notions in regard to the dimensions of the pelvis. To determine this, it is necessary to measure the superior open- ing of the greater pelvis, and the two straits of the lesser. —The pelvis of the male, differs in many respects from that of the female. In the former length predominates, in the latter, breadth. In the female all the diameters of the pelvis are more extensive than those of the male, which is caused by the greater size and outward direction of the iliac fossas, and from a less degree of curvature in the iliac crests, from the roundness of the pubic arch which in the male forms an acute angle. In con- sequence of the wider space which exists between the cotyloid cavities, the gait of the female is characterised by more lateral rotation or waddling, than that of man. —In a well formed woman, the different measurements are nearly as follows: Greater Pelvis. —In the superior opening of the greater pelvis, we distinguish but two diameters, both transverse. The posterior extended from the middle of one iliac crest "' -L......; DIMENSIONS OF THE PELVIS. 153 anterior, between the two anterior superior spinous processes of the ilium, ten inches. From the middle of the iliac crest, to the superior strait, three and a half inches. From the middle of the iliac crest to the tuberosity of the ischium, (whole depth of the pelvis) seven and a half inches nearly.* Lesser Pelvis. Superior Strait, sometimes called ab- Inferior Strait, or perineal. dominal. Inches. Inches. Anteroposterior diameter,from Antero-posterior diameter, be- the symphysis of the pubis to tween the symphysis pubis and the promontory of the sacrum, 4 front of the coccyx, which may Transverse, or iliac, which be increased near an inch by crosses the former, at a right an- the mobility of the coccyx gle, ... 5 backwards, ... 4 Oblique, from the acetabulum Transverse, or ischiatic, from of one side, to the sacro-iliac ar- one tuberosity of the ischium to ticulation of the other, - 4J the other, .... 4 Oblique, from the tuberosity of the ischium of one side, to the middle of the great sacro-sciatic ligament of the other, nearly 4 The height of the posterior wall of the lesser pelvis, formed by the sacrum and coccyx, (of which the latter forms an inch,) is nearly - - - - 5 inches. Height of the anterior wall formed by the os pubis, - H " Height of the lateral walls,.....3£ " Thickness of the symphysis pubis, about - - - i " Depth or sine of the cavity of the sacrum,f nearly - 1 " The Trunk of the Foetus. At birth, each vertebra consists of three pieces, connected by cartilages, viz.: The body, not perfectly ossified; and a bone on each side of it, of a form almost rectangular, on which the oblique processes are very distinguishable, and the transverse processes * The depth or length of the pelvis is rather greater in the male than in the female. t Dimensions of the child's head at birth. The long diameter, from the vertex or posterior extremity of the sagittal suture to the chin, 5$ inches; antero-pos- terior, from the middle of the frontal bone to the tubercle of the occipital, 4 inches; transverse, from one parietal protuberance to the other, 3£ inches. 154 OF THE SUPERIOR EXTREMITIES. may be ascertained. These bones are so applied to the body, as to include a triangular space for the vertebral cavity. The ends of the longest portions are nearly in contact behind; but the spinous process is not formed. The atlas is cartilaginous in front, and has only the two lateral portions ossified. The vertebra dentata consists of four pieces; for, in addition to the three pieces common to the other vertebras, the processus dentatus is a dis- tinct portion. The false vertebra, of which the sacrum consists, are each formed of three bones as the true vertebras. The bones of the os coccygis are cartilaginous, except the first, which is partly ossified. The ribs are almost perfect at birth: their heads and tuber- cles covered with cartilage. The necessity of their motion in respiration, immediately after birth, explains this difference be- tween them, and most of the other bones of the foetus. The sternum consists of several small bones, surrounded by flat cartilages. Ossification goes on in these cartilages from various points; and the distinct bones finally unite into the three pieces of which the sternum is finally composed. The ossa innominata, on each side, are formed of three dis- tinct pieces, united at the acetabulum. The spine of the os ilium is cartilaginous; and the lower part of the bone is not completely ossified. The back part of the os ischium is ossified; but the portion which forms the acetabulum, the tuber, and the crus, is carti- laginous. The upper part of the os pubis, and that portion which forms the symphysis, are ossified. The crus, like that of the ischium, is cartilaginous. Of the Superior Extremities. Each superior extremity consists of the Shoulder, the Arm, the Forearm, and the Hand. The shoulder is composed of the clavicle and scapula. It has been supposed by some persons that the two last mentioned bones belong properly to the thorax; but upon examining the motions of the upper extremi / " " THE CLAVICLE. I55 essential part of it: and it is equally evident that they do not contribute to the perfection of the thorax; they are, therefore, considered as a part of the upper extremity. The Clavicle, Is the long crooked bone resembling the italic f, which is placed almost horizontally between the upper lateral part of the sternum and the acromion, or most prominent process of the scapula which it keeps off from the trunk of the body. The clavicle, as well as other long bones, is larger at its two ends than in the middle. The end next to the sternum is triangular; the angle behind is considerably protruded, to form a sharp ridge, to which the transverse ligament, extended from one clavicle to the other, is fixed. The side opposite to this is somewhat rounded. The middle of this protuberant end is irregularly hollowed, as well as the cavity in the sternum for receiving it: but, in a recent subject, the irregular concavities of both are supplied by a movable cartilage; which is not only much more closely connected every where, by ligaments, to the circumference of the articulation, than those of the lower jaw are, but it grows to the two bones at both its internal and ex- ternal end; its substance at the external end being soft, but very strong, and resembling the intervertebral cartilages. From its internal end, the clavicle, for about two-fifths of its length is bended obliquely forwards. On the upper and front part of this curvature a small ridge is seen, with a plane rough surface before it; whence the sterno-hyoidcus and sterno-mas- toideus muscles have in part their origin. Near the lower angle, a small plane surface is often to be remarked, where the first rib and this bone are contiguous, and are connected by a firm liga- ment. From this a rough plane surface is extended outwards, where the pectoral muscle has part of its origin. Behind, the bone is made flat and rough by the insertion of the larger share of the subclavian muscle. The clavicle is then curved backwards, and at first is round; but it soon after becomes broad and thin; which shape it retains to its external end. Along the external concavity a rough sinuosity runs; from which some part of the deltoid muscle takes its rise : opposite to 156 THE CLAVICLE. this, on the convex edge, a scabrous ridge gives insertion to a share of the trapezius muscle. The upper surface of the clavi- cle is here flat; but the lower is hollow, for lodging the begin- ning of the musculus subclavius; and towards its back part a tubercle rises; to which, and to a roughness near it, the strong, short, thick, ligament, connecting this bone to the coracoid pro- cess of the scapula, is fixed. The external end of this bone is oblong horizontally, smooth, sloping at the posterior side, and tipped in a recent subject with a cartilage, for its articulation with the acromion scapulas. Round this the bone is spongy, for the firmer connexion of the ligaments. The surfaces of contact with this bone, and the scapula are remarkably small, and flat also. The medullary arteries, having their direction obliquely out- wards, enter the clavicles by one or more small passages in the middle of their back part. The substance of this bone is the same as that of the other round long bones. The ligaments which surround the articulation of this bone with the sternum, are so short and strong, that little motion can be allowed any way ; and the strong ligament that is stretched across the upper furcula of the sternum, from the posterior pro- minent angle of the one clavicle to the same place of the other clavicle, serves to keep each of these bones more firmly in its place. By the assistance, however, of the movable intervening cartilage, the clavicle can move at this articulation, so that the external extremity may be elevated or depressed, and moved backwards and forwards. The whole bone may be moved so as to describe a cone; of which the end at the sternum is the apex. The movements of the scapula and arm are the objects of these motions of the clavicle ; and the general use of the bone is to regulate the motions of these parts. From the situation, figure, and use of the clavicles, it is evi- dent that they are much exposed to fractures; that their broken parts must generally pass each other, and that they will be kept in their places with difficulty- THE SCAPULA. 157 The Scapula, Or shoulder-blade, is the triangular bone situated on the upper and back part of the thorax. The back part of the scapula has nothing but the thin ends of the serratus anticus major, and sub- scapularis muscles between it and the ribs: but as this bone ad- vances forwards, its distance from the ribs increases. The longest side of this bone is nearest the spine, and has an oblique position as respects it. The upper or shortest side, called the superior costa of the scapula, is nearly horizontal, and parallel with the second rib. The lower side, which is named the in- ferior costa, is extended obliquely from the third to the eighth rib. The situation of this bone, here described, is, when people are sitting or standing, in a state of inactivity, and allowing the members to remain in the most natural easy posture. The in- ferior angle of the scapula is very acute; the upper one is near to a right angle; and what is called the anterior does not de- serve the name, for the two sides do not meet to form an angle. The body of this bone is concave towards the ribs, and convex behind, where it has the name of dorsum. Three processes are generally reckoned to proceed from the scapula. The first is the large spine that rises from its convex surface behind, and divides it unequally. The second process stands out from the forepart of the upper side ; and, from its imaginary resemblance to a crow's beak, is named coracoides. The third process is the whole thick bulbous forepart of the bone. Into the oblique space the musculus patientias (levator scapula) is inserted. At the root of the spine, on the back part of the base, a triangular flat surface is formed by the pressure of the lower fibres of the trapezius. Below this, the edge of the scapula is scabrous and rough, for the insertion of the serratus major anticus and rhomboid muscles. The back part of the inferior angle is made smooth by the latissimus dorsi passing over it. This muscle also alters the direction of the inferior costa some ,way forwards from this angle: and so far it is flattened behind by the origin of the teres major. As the inferior costa advances forward, it is of con- vol. i. 14 158 THE SCAPULA. siderable thickness, is slightly hollowed, and made smooth be- hind, by the teres minor; while it has a fossa formed into it be- low, by part of the subscapularis ; and between the two, a ridge with a small depression appears, where the longus extensor cubiti has its origin. The superior costa is very thin ; and near its forepart there is a semilunar notch, from one end of which to the other, a liga- ment is stretched; and sometimes the bone is continued to form one, or sometimes two holes, for the passage of the scapula, blood-vessels and nerves. Immediately behind this semilunar cavity, the coraco-hyoideus muscle has its rise. From the notch, to the termination of the fossa for the teres minor, the scapula is narrower than any where else, and supports the third process. This part has the name of cervix. The whole dorsum of the scapula is always said to be convex; but, by reason of the raised edges that surround it, it is divided into two cavities by the spine, which is stretched from behind forwards, much nearer to the superior than to the inferior costa. The cavity above the spine is really concave, where the supra- spinal muscle is lodged; while the surface of this bone below the spine, on which the infra-spinatus muscle is placed, is convex, except a fossa that runs at the side of the inferior costa. The internal or anterior surface of this bone is hollow, except in the part above the spine, which is convex. The subscapularis muscle is extended over this surface, where it forms several ridges and intermediate depressions, commonly mistaken for prints of the ribs: they point out the interstices of the bundles of fibres of which the subscapularis muscle is composed. The spine rises small at the base of the scapula, and becomes higher and broader as it advances forwards. On the sides it is unequally hollowed and crooked, by the action of the adjacent muscles. Its ridge is divided into two rough, flat surfaces: into the upper one the trapezius muscle is inserted; and the lower one has part of the deltoid fixed to it. The end of the spine, called acromion, or top of the shoulder, is broad and flat, and is, sometimes, only joined to the spine by a cartilage. The anterior edge of the acromion is flat, smooth, and covered with a carti- THE SCAPULA. ■ cq lage, for its articulation with the external end of the clavicle; and it is hollowed below, to allow a passage to the infra and supra-spinati muscles, and free motion to the os humeri. The coracoid process is crooked, with its point inclining for- wards; so that a hollow is left at the lower side of its root for the passage of the subscapularis muscle. The end of this pro- cess is marked with three plane surfaces. Into the internal, the pectoralis is inserted ; from the external, one head of the biceps flexor cubiti rises ; and from the lower one, the coraco-brachialis has its origin. At the upper part of the root of this process, immediately before the semilunar cavity, a smooth tubercle ap- pears, where a ligament from the clavicle is fixed. From the whole of the external side of this coracoid apophysis a broad ligament goes out, which becomes narrower where it is fixed to the acromion. From the cervix scapulas the third process is produced. The forepart of this is formed into a glenoid cavity, which is of the shape of the longitudinal section of an egg, being broad below and narrow above. Between the margin of this cavity and the forepart of the root of the spine, a large sinuosity is left for the transmission of the supra and infra-spinati muscles; and on the upper part of this margin we may remark a smooth surface, where the second head of the biceps flexor cubiti has its origin. The root of the margin is rough all around, for the firmer adhe- sion of the capsular ligament of the articulation, and of the car- tilage ; which is thick on the margin, but becomes very thin as it is continued towards the middle of the cavity, which it lines all over. The medullary vessels enter the scapula near the base of the spine. The substance of the scapula, as in all other broad flat bones, is cellular, but of an unequal thickness: for the neck and third process are thick and strong ; the inferior costa, spine, and cora- coid process, are of a middle thickness; and the body is so pressed by the muscles, as to become thin and transparent. The scapula and clavicle are joined by plane surfaces, tipped with cartilage; by which neither bone is allowed any considera- IgO THE SCAPULA. ble motion, being tightly tied down by the common capsular liga- ment, and by a very strong one which proceeds from the cora- coid process; but divides into two before it is fixed into the cla- vicle, with such a direction as can either allow this bone to have a small rotation, in which its posterior edge turns more back- wards, while the anterior one rises farther forwards; or it can yield to the forepart of the scapula moving downwards, while the back part of it is drawn upwards : in both which cases, the oblong, smooth articulated surfaces of the clavicle and scapula are not in the same plane, but stand a little transversely, or across each other, and thereby preserve this joint from luxations, to which it would be subject if either of the bones were to move on the other perpendicularly up and down, without any rotation. Sometimes a movable ligamentous- cartilage is found in this joint; and sometimes such a cartilage is only interposed at the anterior half of it; and in some old subjects a sesamoid bone has been found here. The scapula is connected to the head, os hyoides, vertebras, ribs, and arm bone, by muscles that have one end fastened to these parts, and the other to the scapula, which can move it up- wards, downwards, backwards, or forwards : by the quick suc- cession of these motions, its whole body is carried in a circle. But being also often moved, as upon an axis perpendicular to its plane, its circumference turns in a circle whose centre this axis is. Whichever of these motions it performs, it always car- ries the outer end of the clavicle and the arm along with it. The glenoid cavity of this bone receives the os humeri, which plays in it, as will be more fully explained hereafter. The use of the scapula is, to serve as a fulcrum to the arm; and by altering its position on different occasions, to allow always to the head of the os humeri a socket to move in properly situated; and thereby to assist and to enlarge greatly the motions of the superior extremity, and to afford the muscles which rise from it more advantageous actions, by altering their directions with re- spect to the bone which they are to move. This bone also serves to defend the back part of the thorax, and is often employed to sustain weights, or to resist forces too great for the arm to bear. THE OS HUMERI. 161 Os Humeri, or Arm bone. The arm has only one bone, best known by the Latin name of os humeri; which is long, round, and nearly straight. The upper end of this bone consists of a large round smooth head, which forms the segment of a sphere, whose axis is not in a straight line with the axis of the bone, but stands obliquely backwards from it. The extent of the head is distinguished by a circular fossa surrounding its base, where the head is united to the bone, and the capsular ligament of the joint is fixed. Below the forepart of its base, two tubercles stand out: the smaller one, which is situated most to the inside, has the tendon of the sub- scapularis muscle inserted into it. The larger more external protuberance is divided, at its upper part, into three smooth plane surfaces: into the anterior of which, the musculus supra-spina- tus ; into the middle or largest, the infra-spinatus ; and into the one behind, the teres minor, is inserted. Between these two tu- bercles, exactly in the forepart of the bone, a deep long groove is formed, for lodging the tendinous head of the biceps flexor cu- biti ; which, after passing, in a manner peculiar to itself, through the cavity of the articulation, is tied down, by a tendinous sheath extended across the groove; in which, and in the neighbouring tubercles, are several remarkable holes, which are penetrated by the tendinous and ligamentous fibres, and by vessels. On each side of this groove, as it descends in the os humeri, a rough ridge, gently flattened in the middle, runs from the roots of the tubercles. The tendon of the pectoral muscle is fixed into the anterior of these ridges, and the latissimus dorsi and teres major are inserted into the internal one. A little behind the lower end of this last, another rough ridge may be observed, where the co- raco-brachialis is inserted. From the back part of the root of the largest tubercle, a ridge also is continued; from which the ' extensor brevis cubiti arises. This bone is flattened on the in- side, about its middle, by the belly of the biceps flexor cubiti. In the middle of this plane surface, the entry of the medullary ar- tery is seen slanting obliquely downwards. At the foreside of this plane, the bone rises in a sort of ridge, which is rough, and 14* 102 THE OS HUMERI. often has a great many small holes in it, where the strong del- toid muscle is inserted ; on each side of which the bone is smooth and flat, where the brachialus internus rises. The exterior of these two flat surfaces is the largest: behind it a superficial spi- ral channel, formed by the muscular nerve, and the vessels that accompany it, runs from behind forwards and downwards. The body of the os humeri is flattened behind by the extensors of the forearm. Near the lower end of this bone, a large sharp ridge is ex- tended on its outside; from which the musculus supinator radii longus, and the longest head of the extensor carpi radialis, arise. Opposite to this there is another small ridge to which the apo- neurotic tendon, that gives origin to the fibres of the internal and external brachial muscles, is fixed ; and from a little depression on the foreside of it, the pronator radii teres arises. The body of the os humeri becomes gradually broader towards the lower end, where it has several processes; at the roots of which there is a cavity before, and one behind called sigmoid. The anterior is divided by a ridge into two; the external, which is the least, receives the end of the radius; and the internal re- ceives the coronoid process of the ulna, in the flexions of the forearm; while the posterior deep triangular cavity lodges the olecranon in the extensions of that limb. The bone between these two cavities is pressed so thin by the processes of the ulna, as to appear transparent in many subjects. The sides of the posterior cavity are stretched out into two processes, one on each side. These are called condyles; from each of which a strong ligament goes out to the bones of the forearm. The ex- ternal condyle, which has an oblique direction forwards with re- spect to the internal, when the arm is in the most natural pos- ture, is equally broad, and has an obtuse smooth head rising from it forwards. From the rough part of the condyle, several muscles arise; and on the smooth head the upper end of the radius plays. The internal condyle is more pointed and protu- berant than the external, to give origin to the flexor muscles of the wrist and hands, &c. Between the two condyles, is the trochlea, or pulley; which consists of two lateral protuberances THE OS HUMERI. 163 and a middle cavity that are smooth, and covered with cartilage. When the forearm is extended, the tendon of the internal bra- chialus muscle is lodged in the forepart of the cavity of this pul- ley. The external protuberance, which is less than the other, has a sharp edge behind: but forwards, this ridge is obtuse, and only separated from the little head, already described, by a small fossa, in which the adjoining edges of the ulna and radius move. The internal protuberance of the pulley is largest and highest; and therefore, in the motions of the ulna upon it, that bone would be inclined outwards, were it not supported by the radius on that side. Between this internal protuberance and condyle, a sinuosity may be remarked, where the ulnar nerve passes. The substance and the internal structure of the os humeri are the same, and disposed in the same way, as in the other long bones. The round head, at the upper end of this bone, is articulated with the glenoid cavity of the scapula; which being superficial, and having long ligaments, allows the arm a free and extensive motion. These ligaments are, however, considerably strong. For, besides the common capsular ligament, the tendons of the muscles perform the office, and have been described under the name of ligaments. Then the acromion and coracoid process, with the strong broad ligaments stretched between them, secure the articulation above; where the greatest and most frequent force is applied, to thrust the head of the bone out of its place. It is true, that there is not near so strong a defence in the lower part of the articulation ; but, in the ordinary postures of the arm, that is, so long as it is an acute angle with the trunk of the body, there cannot be any force applied at this place to occasion a luxation, since the joint is protected so well above. The motions which the arm enjoys by this articulation, are to every side: and, by the succession of these different motions, a circle may be described. Besides which, the bone performs a small rotation round its own axis; but, when the axis of the bone is the centre of motion, the movements are very different from those which take place when the axis of its head is the centre; for the axis of the'head forms a very large angle with the axis of the body of the bone. Thus, when the arm swings back- 164 ULNA- wards and forwards, the axis of the head is the centre of motion; but when the elbow is bent, and the forearm forms a right angle with the os humeri, the motion which applies the forearm to the thorax, or removes it, is a rotation of this bone on its axis. Though the motions of the arm seem to be very extensive, yet the larger share of them depends on the motions of the sca- pula ; for the surface of the glenoid cavity is directed upwards or downwards, and, to a certain degree, backwards or forwards, to support the head of the os humeri. This is exemplified when we press the hand against a body which is before, or above, or to one side of us. The lower end of the os humeri is articulated to the bones of the forearm, and carries them with it in all its motions; but serves as a base, on which they perform the motions peculiar to themselves; as will shortly be described. The Forearm Consists of two bones, one of which is called ulna, from its being used as a measure; and the other radius, from the sup- posed resemblance to the spoke of a wheel. These bones are concerned in very different operations. The ulna forms the elbow joint with the os humeri; the radius is the movable basis of the hand. Ulna. The length of this bone is equal to the forearm, of which it is a part. It is thickest above, and gradually diminishes until near its lower end. The body of the bone is nearly triangular in form. At the upper extremity of the ulna, on its anterior sur- face, is a semicircular notch. The end of the bone which forms the posterior part of this notch is denominated olecranon. The anterior part of the notch is formed by a process called coro- noid. This notch applies to the pulley-like surface on the inter- nal side of the lower extremity of the os humeri, to form the articulation of the elbow. In the middle of the concave surface is a ridge, in consequence of which, a small rocking motion is performed by the ulna. The external surface of the olecranon is rough, and strongly marked- T1^ pvtpn«nr mn^io r.f *Ut> THE ULNA 165 forearm is inserted into the end of it, and below this is a flat surface on which we lean. On the outside of the coronoid pro- cess is a semilunated smooth cavity, lined with cartilage; in which, and in a ligament extended from the one to the other end of this cavity, the round head of the radius plays. Imme- diately below it, a rough hollow gives lodging to mucilaginous glands. Below the root of the coronoid process, this bone is scabrous and unequal, where the brachialus internus is inserted. On the outside of that, we observe a smooth concavity, where the beginning of the flexor digitorum profundus sprouts out. The external angle of the triangular part of the ulna is very sharp, where the ligament that connects the two bones is fixed: the sides which make this angle are flat and rough, by the action and adhesion of the many muscles which are situated here. At the distance of one-third of the length of the ulna from the top, in its forepart, the passage of the medullary vessels may be seen slanting upwards. The internal side of this bone is smooth, somewhat convex, and the angles at each edge of it are blunted by the pressure of the muscles equally disposed about them. As this bone descends, it becomes gradually smaller; so that its lower end terminates in a little head, standing on a small neck: towards the inner and back part of which last, an oblique ridge runs, that gives rise to the pronator radii quadratus. The head is sometimes cylindrical, smooth, and covered with a car- tilage on its external side, to be received into the semilunar cavity of the radius; while a styloid process rises from its in- side, to which is fixed a strong ligament that is extended to the os cuneiforme and pisiforme of the wrist. At the root of the process, the end of the bone is smooth, and covered with a car- tilage. Between it and the bones of the wrist, a doubly concave movable cartilage is interposed; which is a continuation of the cartilage that covers the lower end of the radius, and is con- nected loosely to the root of the styloid process, and to the rough cavity there; in which mucilaginous glands* are lodged. The ulna is principally concerned in the articulation with the * All these so called glands are mere masses of adipose matter, supposed, though wrongly, by Havers to be the glands which secrete the synovia.—p. 166 RADILS os humeri, and forms a hinge-like joint, which allows extension nearly to a straight line, and flexion to an acute angle. By the sloping of the pulley-like surface, the lower part of the arm is turned outwards in the extension, and inwards in the flexion; which greatly facilitates the motion of the hand towards the head. Radius. Before the radius is described, it is necessary to observe that the lower end of this bone occasionally revolves half round the lower end of the ulna, and the hand with it. The relative situation of these parts is, therefore, different in different positions of the hand. In the following description, the palm of the hand is supposed to present forwards, and the thumb out- wards ; in which case, the two bones of the forearm will be parallel to each other. The radius is situated on the outside of the forearm, and is rather shorter than the ulna. Its extremities are the reverse of those of the ulna in their proportionate size; and the body is not triangular, although it approaches towards that form. Its upper end is formed into a cylindrical head, which is hollowed on the top for an articulation with the tubercle at the side of the pulley of the os humeri; and the half cylindrical circumference next to the ulna is smooth, and covered with a cartilage, in order to be received into the semilunated cavity of that bone. Below the head, the radius is much smaller; and, therefore, this part is named its cervix. At the internal root of this neck is a flat tubercle, into the inner part of which the biceps flexor cubiti is inserted. From this a ridge runs downwards and outwards where the supinator radii brevis is inserted; and a little below, and behind this ridge, there is a rough scabrous surface, where the pronator radii teres is fixed. The body of the radius is not straight, but curved externally the greater part of its length. Its external surface is rounded ; the anterior and posterior surfaces are flattened ; and between them is a sharp spine, to which the strong ligament extended between the two bones of the forearm is fixed. On the anterior surface, at a distance from its head, nearly equal to one-third RADIUS. 107 the length of the bone, is the orifice of the canal for the medul- lary vessels, which has a direction obliquely upwards. Towards the lower end the radius becomes broader and flatter, especially on its forepart, where the pronator quadratus muscle is situated. Its back part, at this end, has a flat strong ridge in the middle, and fossas on each side. In a small groove, imme- diately on the inside of the ridge, the tendon of the extensor of the last joint of the thumb plays, In a large one, inside of this, the tendons of the indicator, and of the common extensor muscles of the fingers pass. On the outside of the ridge there is a broad depression, which seems again subdivided, where the two tendons of the extensor carpi radialis are lodged. The ex- ternal side of this end of the radius is also hollowed by the ex- tensors of the first and second joints of the thumb. The ridges at the sides of the grooves, in which the tendons play, have an annular ligament fixed to them, by which the several sheaths for the tendons are formed. The forepart of this end of the radius is also depressed, where the flexors of the fingers and flexor carpi radialis pass. The internal side is formed into a semilunated smooth cavity, lined with a cartilage, for receiving the lower end of the ulna. The lowest part of the radius is formed into an oblong cavity; in the middle of which is a small transverse rising, gently hollowed, for lodging mucilagi- nous glands; while the rising itself is insinuated into the con- junction of the two bones of the wrist that are received into the cavity. The external side of this articulation is defended by a remarkable process of the radius, from which a ligament passes to the wrist; and this structure resembles that of the styloid process of the ulna with its ligament. The ends of both the bones of the forearm being thicker than the middle, and the radius being curved, there is a considerable distance between the bodies of these bones; in the larger part of which a strong, tendinous, but thin ligament, is extended, to give a sufficient surface for the origin of the numerous fibres of the muscles situated here, that are so much sunk between the bones as to be protected from injuries, to which they would otherwise be exposed. But this ligament is wanting near the 168 THE HAND. upper end of the forearm, where the supinator radii brevis and flexor digitorum profundus, are immediately connected. As the head of the radius receives the tubercle of the os humeri, it is not only bended and extended along with the ulna, but may be moved almost half round its axis; and that this motion round its axis may be sufficiently large, the ligament of the articulation is extended farther down than ordinary, on the neck of this bone, before it is connected to it; and it is very thin at its upper and lower part, but makes a firm ring in the middle. This bone is also joined to the ulna by a double articulation : for above, a tubercle of the radius plays in a socket of the ulna; whilst below, the radius gives the socket, and the ulna the tubercle. But then the motion performed at the two ends is very different: for, at the upper end, the radius does little more than turn round its axis; while, at the lower end, it moves nearly half round the cylindrical end of the ulna; and, as the hand is articulated and firmly connected here with the radius, they must move together. When the palm is turned uppermost, the radius is said to perform supination: when the back of the hand is above, it is said to be prone. But then the quickness and large extent of these two motions are assisted by the ulna, which, as was before observed, can move with a kind of small rotation on the sloping sides of the pulley. This rocking motion, though very inconsiderable in the elbow joint itself, is conspicuous at the lower end of such a long bone; and the strong ligament con- necting this lower end to the carpus, makes the hand more readily obey these motions. The Hand. The hand comprehends the whole structure, from the end of the radius to the points of the fingers. Its back part is convex, for greater firmness and strength; and it is concave before, for containing more surely and conveniently such bodies as we take hold of. One half of the hand has an obscure motion in com- parison of what the other has ; it serves as a base to the mova- ble half, which can be extended back very little farther than to a CARPUS. ,fig straight line with the forearm, but can be considerably bent for- wards. The hand consists of the carpus or wrist; metacarpus, or part adjoining the wrist; and the fingers, among which the thumb is reckoned. Carpus. No part of the skeleton is more complex than the carpus. The following description will, therefore, be of little use to a young student, unless the bones are before him when he is reading it. Great advantage will be de- rived from examining two sets of carpal bones: each set belonging to the same side. In one of these sets the bones should be connected by their natural ligaments; but the two rows separated from each other. The bones of the other set should be accurately cleaned, so that their forms and surfaces may be examined. The carpus is composed of eight small bones, arranged in two rows; one of which rows is attached to the bones of the fore- arm, and the other to the body of the hand. These bones are named from their figure, and shall be men- tioned in the order in which they occur, beginning with the row next to the forearm; and with the external bone in each row. They are, Os Scaphoides, Lunare, Cuneiforme, Pisiforme, forming the upper row; Os Trapezium, Trapezoides, Magnum, and Unciforme, forming the lower row7. First Row. Os scaphoides is the largest of the eight, excepting one. It is convex above, concave and oblong below; from which small resemblance to a boat, it has got its name. Its smooth convex surface is divided by a rough middle fossa, which runs obliquely across it. The upper largest division is articulated with the radius. The common ligament of the joint of the wrist is fixed into the fossa; and the lower division is joined to the trapezium and tra- pezoides. The concavity receives more than half of the round head of the os magnum. The internal side of this hollow is formed into a semilunar plane to be articulated with the follow- ing bone. The external, posterior, and anterior edges are rough, for fixing the ligaments that connect it to the surrounding bones. vol. i. 15 170 CARPUS. Os lunare has a smooth convex upper surface, by which it is articulated with the radius. The external side, which gives the name to the bone, is in the form of a crescent, and is joined with the scaphoid: the lower surface is hollow, for receiving part of the head of the os magnum. On the inside of this cavity is another smooth, but narrow, oblong sinuosity, for receiving the upper end of the unciforme: and on the inside of this a small convexity is found, for its connexion with the os cunei- forme. Between the great convexity above, and the first deep inferior cavity, there is a rough fossa, in which the circular liga- ment of the joint of the wrist is fixed. Os cuneiforme is broader above, and towards the back of the hand, than it is below and forwards; which gives it the resem- blance of a wedge. The superior slightly convex surface is in- cluded in the joint of the wrist, being opposed to the lower end of the ulna. Below this the cuneiforme bone has a rough fossa, wherein the ligament of the articulation of the wrist is fixed. On the external side of this bone, where it is contiguous to the os lunare, it is smooth, and slightly concave. Its lower surface, where it is contiguous to the os unciforme, is oblong, somewhat spiral, and concave. Near the middle of its anterior surface, a circular plane appears, where the os pisiforme is sustained. Os pisiforme is almost spherical, except one circular plane, or slightly hollowed surface, which is covered with cartilage for its motion on the cuneiforme bone, from which its whole rough body is prominent forwards into the palm ; having the tendon of the flexor carpi ulnaris, and a ligament from the styloid process of the ulna fixed to its upper part; the transverse ligament of the wrist is connected to its external side: ligaments extended to the unciforme bone, and to the os metacarpi of the little finger, are attached to its lower part; the abductor minimi digiti has its origin from its forepart; and, at the external side of it, a small depression is formed for the passage of the ulnar nerve. Second Row. Os Trapezium has four unequal sides and angles in its back part, from which it has got its name. Above, its surface is smooth, slightly hollowed, and semicircular, for its conjunction with the CARPUS. 171 os scaphoides. Its internal side is an oblong concave square, for receiving the following bone. The inferior surface is formed into a pulley, which faces obliquely outwards and downwards when the palm presents forward. On this pulley the first bone of the thumb is moved. At the internal side of the pulley, a small oblong smooth sur- face is formed by the os metacarpi indicis. The forepart of the trapezium is prominent in the palm, and near to the internal side has a sinuosity in it, where the tendon of the flexor carpi radialis is lodged, on the ligamentous sheath of which the tendon of the flexor longus pollicis manus plays: near this the bone is sca- brous, where the transverse ligament of the wrist is connected, the abductor and the flexor brevis pollicis have their origin, and ligaments go out to the first of the thumb. Os trapezoides, so called from the irregular quadrangular figure of its back part, is the smallest bone of the wrist, except the pisiforme. The figure of it is an irregular cube. It has a small hollow surface above, by which it joins the scaphoides; a long convex one externally, where it is contiguous to the trapezium ; a small internal concavity, for its conjunction with the os mag- num ; and an inferior convex surface, the edges of which are, however, so raised before and behind, that a sort of pulley is formed, where it sustains the os metacarpi indicis. Os magnum, so called because it is the largest bone of the carpus, is oblong, having four quadrangular sides, with a round upper end, and a triangular plane one below. The round head is divided by a small rising, opposite to the connexion of the os scaphoides and lunare, which together form the cavity for re- ceiving it. On the outside a short plane surface joins the os magnum to the trapezoides. On the inside is a long narrow con- cave surface where it is contiguous to the os unciforme. The lower end, which sustains the metacarpal bone of the middle finger, is triangular, slightly hollowed, and farther advanced on the external side than on the internal, having a considerable ob- long depression made on the advanced outside by the metacarpal bone of the fore-finger ; and generally there is a small mark of the os metacarpi digiti annularis on its internal side. i«2 CARPUS. Os unciforme has got its name from a thin broad process that stands out from it forwards into the palm, and is hollow, for af- fording passage to the tendons of the flexors of the fingers. To this process, also, the transverse ligament is fixed that binds down, and defends these tendons; and the flexor and abductor muscles of the little finger have part of their origin from it. The upper plane surface is small, convex, and joined with the os lunare: the external side is long and slightly convex, adapted to the contiguous os magnum. The internal surface is oblique, and irregularly convex, to be articulated with the cuneiforme bone. The lower end is divided into two concave surfaces ; the internal is joined with the metacarpal bone of the little finger; and the external one is fitted to the metacarpal bone of the ring finger. The nature of the carpus will be best understood by studying the bones placed together, in their natural order, in the two rows. When thus placed, they compose a structure of an oblong form, whose greatest length extends across the wrist, and forms a concavity in front, while it is convex posteriorly. Two bones of the first row, viz. the scaphoides and lunare, form an oblong convex surface, which has a transverse position with respect to the arm, and applies to the concave surface at the end of the radius. These surfaces are particularly calcu- lated for flexion and extension, and also for a considerable motion to each side; and by a succession of these flexures, in different directions, the hand performs a circular motion, although it can- not perform at this joint a rotation, or revolution, on the axis of the carpus. The under surface of these bones has a deep concavity, which is composed by the scaphoides, lunare and cuneiforme, and re- ceives a prominence of the second row. It also presents a con- vex surface, formed by the scaphoides, which is received by the second row. The upper surface of the second row, which is concerned in this articulation, is very irregular; it has a head formed by the magnum and unciforme, which penetrates deeply into the cavity THE METACARPUS. 173 of the first row. On the outside of this head the trapezium and trapezoides form a surface, which receives the projecting part of the scaphoides ; so that the first row receives, and is received by the second, and the two surfaces are well calculated for moving, to a certain extent, in the way of flexion and extension, upon each other. The lower surface of the second row, which is connected to the metacarpal bones, appears like the side of an arch, which is partly induced by the wedge-like form of the two bones in the centre ; viz. the trapezoides, and the magnum. When the hand hangs by the side, and the palm is forward, all of this surface presents downwards, except that portion of it which is formed by the trapezium. This bone is placed obliquely between the two rows, and its surface for supporting the thumb presents ob- liquely downwards and outwards. The trapezoides supports the fore-finger, the magnum the middle finger. The scaphoides and the trapezium are very prominent at the external side of the anterior concave surface of the carpus; and the unciforme process, and the os pisiforme on the internal. The Metacarpus, Consists of four bones, which sustain the fingers. Each bono is long and round, with its ends larger than its body. The up- per end, which some call the base, is flat and oblong, inclining somewhat to the wedge-like form, without any considerable head or cavity; but it is, however, somewhat hollowed for the articu- lation with the carpus. It is made flat and smooth on the sides where these bones are contiguous to each other. Their bodies are flattened on the back part, particularly below the middle, by tendons of the extensors of the fingers. The anterior surface of these bodies is a little convex, especially in their middle; along which a sharp ridge stands out, separating the musculi interossei placed on each side of these bones, which are there made flat and plain by these muscles. Their lower ends are raised into large oblong smooth heads, whose greatest extent is forwards from the axis of the bone. At 15* 174 THE METACARPUS. the forepart of each side of the root of these heads, one or two tubercles stand out, for fixing the ligaments that go from one metacarpal bone to another, to preserve them from being drawn asunder. Around the heads a rough ring may be remarked, for the capsular ligaments of the first joints of the fingers to be fixed to; and both sides of these heads are flat, by pressing on each other. The substance of the metacarpal bones is the same with that of all long bones. The metacarpal bones are joined above to the bones of the carpus, and to each other by surfaces almost flat. These con- nexions do not admit of much motion. The articulation of the round heads, at their lower ends, with the cavities of the first bones of the fingers, will soon be described. The concavity on the forepart of the metacarpal bones, and the position of their bases on the arched carpus, cause them to form a hollow in the palm of the hand, which is often useful to us. The spaces between them lodge muschss, and their small motion makes them fit supporters for the fingers to play on. Though the ossa metacarpi so far agree, yet they may be dis- tinguished from each other by the following marks : The metacarpal bone of the fore-finger is generally the longest. Its base, which is articulated with the os trapezoides, is hollow in the middle. The small ridge on the external side of this oblong cavity is smaller than the one opposite to it, and is made flat on the side by the trapezium. The internal ridge is also smooth, and flat on its ulnar side, for its conjunction with the os magnum ; immediately below which, a semicircular smooth flat surface shows the articulation of this to the second metacarpal bone. The back part of this base is flattened where the long head of the extensor carpi radialis is inserted, and its forepart is pro- minent where the tendon of the flexor carpi radialis is fixed. The tubercle at the internal root of its head is larger than the external. Its base is so firmly fixed to the bone it is connected with, that it has no motion. The metacarpal bone of the middle finger is generally the se- cond in length; but often it is as long as the former: sometimes THE METACARPUS. 175 it is longer; and it frequently appears only to equal the first by the os magnum being farther projected downwards than any other bone of the wrist. Its base is a broad superficial cavity, slanting inwards; the external posterior angle of which is so prominent, as to have the appearance of a process. The exter- nal side of this base is made plane in the same way as the exter- nal side of the former bone, while its internal side has two hol- low circular surfaces, for joining the third metacarpal bone ; and between these surfaces there is a rough fossa, for the adhesion of a ligament, and lodging mucilaginous glands. The extensor carpi radialis brevior is inserted into the back part of this base. The two sides of this bone are almost equally flattened ; but the ridge on the forepart of the body inclines inwards. The tu- bercles at the forepart of the root of the head are equal. The motion of this bone is very little more than that of the former; and therefore these two firmly resist bodies pressed against them by the thumb or fingers, or both. The metacarpal bone of the ring finger is shorter than the se- cond metacarpal bone. Its base is semicircular and convex, for its conjunction with the os unciforme. On its external side are two smooth convexities, and a middle fossa, adapted to the second metacarpal bone. The internal side has a triangular smooth concave surface to join it with the fourth one. The an- terior ridge of its body is situated more to the inside than to the outside. The tubercles near the head are equal. The motion of this third metacarpal bone is greater than the motion of the se- cond. The metacarpal bone of the little finger is the smallest and sharpest. Its base is irregularly convex, and rises slanting in- wards. Its external side is exactly adapted to the third meta- carpal bone. The internal has no smooth surface, because it is not contiguous to any other bone ; but it is prominent where the extensor carpi ulnaris is inserted. As this metacarpal bone is furnished with a proper moving muscle, has the plainest articu- lation, is most loosely connected and least confined, it not only enjoys a much larger motion than any of the rest, but draws the third bone with it, when the palm of the hand is to be made hoi- 176 THUMB AND FINGERS. low by its advancement forwards, and by the prominence of the thumb opposite to it. Thumb and Fingers. The thumb and fore-fingers are each composed of three bones. The thumb is situated obliquely in respect to the fingers; neither opposite directly to them, nor in the same plane with them. All its bones are much thicker and stronger in propor- tion to their length, than the bones of the fingers are; which is extremely necessary, as the thumb counteracts all the fingers. The first bone of the thumb has its base adapted to the pecu- liar articulating surface of the trapezium ; for, in viewing it from one side to the other, it appears convex in the middle ; but, when viewed from behind forwards, it is concave there. The edge at the forepart of this base is extended farther than any other part; and round the back part of the base a rough fossa may be seen, for the connexion of the ligaments of this joint. The body and head of this bone are of the same shape as the ossa metacarpi; only that the body is shorter, the head flatter, and tubercles at the forepart of its root larger. The articulation of the upper end of this bone is remarkable; for, though it has protuberances and depressions adapted to the double pulley of the trapezium, yet it enjoys a circular motion, as the joints do where a round head of the one plays in the orbi- cular socket of another: it is, however, more confined, and less expeditious, but stronger and more secure than such joints gene- rally are. The second bone of the thumb has a large base formed into an oblong cavity, whose greatest length is from one side to the other. Round it several tubercles may be remarked, for the in- sertion of ligaments. Its body is convex, or half round behind; but flat before, for lodging the tendon of the long flexor of the thumb, which is tied down by ligamentous sheaths, that are fixed on each side to the angle at the edge of this flat surface. The lower end of this second bone has two lateral round protu- berances, and a middle cavity, whose greatest extent of smooth surface is forwards and backwards. FINGERS. -I'll The articulation of the upper end of this second bone would seem calculated for motion in all directions; yet, on account of the strength of its lateral ligaments, the oblong figure of the joint itself, and mobility of the first joint, it only allows flexion and extension ; and these are generally much confined. The third bone of the thumb is the smallest, with a large base, whose greatest extent is from one side to the other. This base is formed into two cavities and a middle protuberance, to be adapted to the pulley of the former bone. This bone becomes gradually smaller, till near the lower end, where it is a little enlarged, and has an oval scabrous edge. Its body is rounded behind, but is flatter than in the former bone, for sustaining the nail. It is flat and rough before, by the insertion of the flexor longus pollicis. The motion of this third bone is confined to flexion and ex- tension. The regular arrangement of the bones of the fingers in three rows, has obtained for them the name of the three phalanges. All of them have half round convex surfaces, covered with an, aponeurosis, formed by the tendons of the extensors, lumbricales, and interossei, and placed directly backwards, for their greater strength; and their flat concave part is forwards, for taking hold more surely, and for lodging the tendons of the flexor mus- cles. The ligaments for keeping down these tendons are fixed to the angles that are between the convex and concave sides. The bones of the first phalanx of the fingers answer to the description of the second bone of the thumb; only that the cavity in their base is not so oblong; nor is their motion on the meta- carpal bones so much confined ; for they can move laterally or circularly, the fore-finger in particular, but have no rotation, or a very small degree of it, round their axis. The second bone of the fingers has its base formed into two lateral cavities, and a middle protuberance: while the lower end has two lateral protuberances, and a middle cavity; therefore, it is joined at both ends in the same manner; which none of the bones of the thumb are. The third bone differs nothing from the description of the third 17Q THE THIGH. bone of the thumb, except in the general distinguishing marks ; and, therefore, the second and third phalanx of the fingers enjoy only flexion and extension. All the difference of the phalanges of the several fingers con- sists in their magnitude. The bones of the middle finger being the longest and largest; those of the fore-finger come next to these in thickness, but not in length, for those of the ring finger are a little longer. The little finger has the smallest bones. Which disposition is the best contrivance for holding the largest bodies; because the longest fingers are applied to the middle largest periphery of such substances as are of a spherical figure. The Inferior Extremities. The inferior extremities consist of the Thigh, Leg, and Foot. The Thigh. Consists of one bone only; the os femoris, which is very strong, and larger than any other in the skeleton. It is nearly cylindrical in the middle, and slightly curved. The upper ex- tremity is a spherical head, connected to the body of the bone by a neck. The lower extremity is much larger than the body. and is formed into two condyles. The upper end of this bone is not continued in a straight line with the body of it, but the axis of it inclines obliquely inwards and upwards, whereby the distance between these two bones, at their upper part, is considerably increased. The head is the greater portion of a sphere. Towards its lower internal part, a round, rough, spongy pit is observable, where the strong liga- ment, commonly, but inaccurately, called the round one, is fixed, to be extended from thence to the lower internal part of the re- ceiving cavity, where it is considerably broader than near to the head of the thigh bone. The neck of the os femoris has a great many large holes, into which the fibres of the strong liga- ment, continued from the capsular, enter, and are thereby firmly united'to it; and round the root of the neck, where it rises from the bone, a rough ridge is found, where the capsular ligament of the articulation itself is connected. Below this root, a large THE THIGH. i*g unequal protuberance, called trochanter major, stands out; the external convex part of which is distinguished into three different surfaces; whereof the one on the upper and front part is sca- brous and rough, for the insertion of the glutasus minimus; the superior one is smooth, and has the glutasus medius inserted into it; and the one behind is made flat and smooth, by the tendon of the glutasus maximus passing over it. The upper edge of this process is sharp and pointed at its back part, where the glutasus medius is fixed; but forwards it is more obtuse, and under it is a depression, into which some of the muscles, which rotate the thigh outwards, are fixed. From the posterior pro- minent part of this great trochanter, a rough ridge runs back- wards and downwards, into which the quadratus is inserted. In the deep hollow, at the internal upper side of this ridge, the ob- turator externus is implanted. More internally, a conical pro- cess, called trochanter minor, rises, for the insertion of the mus- culus psoas and iliacus internus ; and the pectineus is implanted into a rough hollow, below its internal root. The muscles inserted into these processes being the principal instruments of the rotary motion of the thigh, have occasioned the name of trochanters to be given to these processes. The body of the os femoris is convex on the forepart and concave behind, which enables us to sit without leaning too much on the posterior muscles. On the posterior concave surface is a broad rough ridge called linea aspera, which commences near the great trochanter, and continues downwards, more than two-thirds of the length of the bone, when it divides into two ridges, which descend towards each condyle. The internal of these ridges is the most smooth, and the space between them is nearly flat. Near the end of each of these ridges, a small, smooth protuberance may often be remarked, where the two heads of the external gastrocne- mius muscle take their rise; and from the forepart of the in- ternal tubercle, a strong ligament is extended to the inside of the tibia. The lower end of the os femoris is larger than any other part of it, and is formed into two great protuberances, one on each 180 OS FEMORIS. side, which are called its condyles: between them a considerable cavity is found, especially at the back part, in which the crural vessels and nerves lie. The internal condyle is longer than the external, which must happen from the oblique position of this bone, to give less obliquity to the leg. These processes are of an oblong form, and are placed obliquely with respect to each other; being in contact before and separated to a considerable distance behind. They form in front a smooth pulley-like surface, the externa] side of which is highest, on which the patella moves. Below, they are flat; and posteriorly, they are regularly con- vex. Between these convex portions is a rough cavity, from which the crucial ligament arises, to be attached to the tibia. Round the lower end of the thigh bone, large holes are found, into which the ligaments for the security of the joint are fixed, and blood-vessels pass to the internal substance of the bone. The thigh bone being articulated above with the acetabulum of the os innominatum, which affords its round head a secure and extensive play, can be moved to every side: but it is re- strained in its motion outwards by the high brims of the cavity, and by the round ligament; for otherwise the head of the bone would have been frequently thrust out at the breach of the brims on the inside, which allows the thigh to move considerably in- wards. The body of this bone enjoys little or no rotary motion, though the head most commonly moves round its own axis; be- cause the oblique direction of the neck and head from the bone, is such, that the rotary motion of the head can only bring the body of the bone forwards and backwards. Nor is the head, as in the arm, ever capable of being brought to a straight direction with its body; so far, however, as the head can move within the cavity backwards and forwards, the rest of the bone may have a partial rotation. From the oblique position of these bones it results, that there is a considerable distance between them above, while the knees are almost contiguous. Sufficient space is thereby left for the external parts of generation, for the two great outlets of urine THE TIBIA. 181 and fasces, and for the large thick muscles that move the thigh inwards. At the same time this situation of the thigh bone renders our progression quicker, surer, straighter, and in less room : for, had the knees been at a greater distance from each other, we must have been obliged to describe some part of a circle with the trunk of our body in making a long step; and when one leg was raised from the ground, our centre of gravity would have been too far from the base of the other, and we should consequently have been in danger of falling; so that our steps would neither have been straight nor firm, nor would it have been possible to walk in a narrow path, had our thigh bones been otherwise placed. In consequence, however, of the weight of the body bearing so obliquely on the joint of the knee by this situation of the thigh bones, weak rickety children be- come knock-kneed. The Leg Is composed of the two bones, the tibia and fibula. The patella being evidently appropriated to the knee-joint, may be regarded as common both to the thigh and leg. The Tibia Is the long thick triangular bone, situated at the internal part of the leg, and continued in almost a straight line from the thigh bone. The name is derived from its resemblance to the ancient musical instrument. The upper end of the tibia is large, bulbous, and spongy. It has a horizontal surface, divided into two cavities, by a rough, irregular protuberance, which is hollow at its most prominent part, as well as before and behind. The anterior of the two ligaments that compose the great crucial is inserted into the middle cavity; and the depression behind receives the posterior ligament. The two broad cavities at the sides of this protube- rance are not equal; for the internal is oblong and deep, to re- ceive the internal condyle of the thigh bone; while the external is more superficial and round, for the external condyle. In each of these two cavities of a recent subject, a semilunar cartilage vol. i. 16 182 TIBIA- is placed, which is thick at its convex edge, and becomes gradually thinner towards the concave or interior edge. The thick convex edge of each cartilage is connected to the capsular and other ligaments of the articulation; but so near to their rise from the tibia, that the cartilages are not allowed to change their places ; while their narrow ends are fixed at the insertion of the strong cross ligament into the tibia, and seem to have their substance mited with it; therefore a circular hole is left between each cartilage and the ligament, in which the most prominent convex part of each condyle of the thigh bone moves. The cir- cumference of these cavities is rough and unequal, for the firm connexion of the ligaments of the joint. Immediately below the edge, at its back part, two rough flattened protuberances stand out; into the internal, the tendon of the semimembranosus muscle is inserted; and a part of the cross ligament is fixed to the ex- ternal. On the outside of this last tubercle, a smooth slightly hollowed surface is formed by the action of the poplitasus muscle. Before the forepart of the upper end of the tibia, a large rough protuberance rises, to which the strong tendinous liga- ment of the patella is fixed. On the internal side of this, there is a broad scabrous slightly hollowed surface, to which the internal long ligament of the joint, the aponeurosis of the vastus internus, and the tendons of the semitendinosus, gracilis, and sartorius, are fixed. Below the external edge of the upper end of the tibia, there is a flat circular surface, covered in a recent subject with cartilage, for the articulation of the fibula. The body of the tibia is triangular. The anterior angle is very sharp, and is commonly called the spine or shin. This ridge is not straight; but turns first inwards, then outwards, and lastly inwards again. The plane internal side is smooth and equal, being little subjected to the actions of muscle ; but the external side is hollowed above by the tibialis anticus, and below by the extensor digitorum longus and extensor pollicis longus. The two angles behind these sides are rounded by the action of the muscles; the pos- terior side comprehended between them is not so broad as those already mentioned, but is more oblique and flattened by the FIBULA. jog action of the tibialis posticus and flexor digitorum longus. A little above the middle of the bone, the internal angle terminates, and the bone is made round by the pressure of the musculus solaeus. Near to this, the passage of the medullary vessels is seen slanting obliquely downwards. The lower end of the tibia is hollowed, with a small protu- berance in the middle. The internal side of this cavity, which is smooth, and in a recent subject is covered with cartilage, is extended into a considerable process, commonly named malleolus internus; the point of which is divided by a notch, and from it ligaments are sent out to the foot. The external side of this end of the tibia has a rough- irregular cavity formed in it, for re- ceiving the lower end of the fibula. The posterior side has two lateral grooves, and a small middle protuberance. In the internal depression, the tendons of the musculus tibialis posticis and flexor digitorum longus are lodged ; and in the external, the tendon of the flexor longus pollicis plays. From the middle protuberance, ligamentous sheaths go out, for tying down these tendons. The Fibula Is the small bone, placed on the outside of the leg, opposite to the external angle of the tibia ; the shape of it is irregular. The head of the fibula has a circular surface formed on its inside, which, in a recent subject is covered with a cartilage; and it is so closely connected to the tibia by ligaments, as to allow only a very small motion backwards and forwards. This head is protuberant and rough on its outside, where a strong round ligament and the musculus biceps are inserted, and, below the back part of its internal side, a tubercle may be re- marked, that gives rise to the strong tendinous part of thesolasus muscle. The body of this bone is a little crooked inwards and back- wards: which figure is owing to the actions of the muscles. The sharpest angle of the fibula is forwards; on each side of which the bone is considerably, but unequally, depressed by the bellies of the several muscles that rise from or act upon it. The external surface of the fibula is depressed obliquely from above Ig4 FIBULA. downwards and backwards, by the two peronasi. Its internal surface is unequally divided into two narrow longitudinal planes, by an oblique ridge extended from the upper part of the anterior angle. To this ridge the ligament stretched between the two bones of the leg is connected. The anterior of the two planes is very narrow above, where the extensor longus digitorum and extensor longus pollicis arise from it: but is broader below, where it has the print of the nonus vesalii. The posterior plane is broad and hollow, giving origin to the larger share of the tibialis posticus. The internal angle of this bone has a tendinous membrane fixed to it, from which some fibres of the flexor digi- torum longus take their rise. The posterior surface of the fibula is the plainest and smoothest; but is made flat above by the solasus, and is hollowed below by the flexor pollicis longus. In the middle of this surface, the canal for the medullary vessels may be seen slanting downwards. The lower end of the fibula is extended into a spongy oblong head: on the inside of which is a convex, irregular, and fre- quently a scabrous surface, that is received by the external hol- low' of the tibia, and so firmly joined to it by a very thin inter- mediate cartilage and strong ligaments, that it scarce can move. Below this the fibula is stretched out into a smooth coronoid pro- cess, covered with cartilage on its internal side, and is there con- tiguous to the outside of the first bone of the foot, the astragalus, to secure the articulation. This process, named malleolus exter- nus, being situated farther back than in the internal malleolus, and in an oblique direction, obliges us, naturally, to turn the forepart of the foot outwards. At the lower internal part of this process, a spongy cavity for mucilaginous glands may be re- marked ; from its point, ligaments are extended to the bones of the foot, viz. the astragalus, os calcis, and os naviculare ; and from its inside short strong ones go out to the astragalus. On the back part of it a sinuosity is made by the tendons of the pe- ronasi muscles. When the ligament, extended over these tendons from the one side of the depression to the other, is broken, stretched too much, or made weak by the sprain, the tendons frequently start forwards to the outside of the fibula. THE PATELLA OR ROTULA. jgg The conjunction of the upper end of the fibula with the tibia is by plane surfaces tipped with cartilage; and at its lower end the cartilage seems to glue the two bones together; not, how- ever, so firmly in young people, but that the motion at the other end is very observable. In old subjects, the two bones of the leg are sometimes united by anchylosis at their lower ends. The principal use of this bone is to afford origin and insertion to muscles; and to give a particular direction to their tendons. It likewise assists to make the articulation of the foot more se- cure and firm, and to complete the hinge-like joint at the ankle. The ends of the tibia and fibula being larger than their middle, a space is here left, which is filled up with a ligament similar to that which is extended between the bones of the forearm; and which is also discontinued at its upper part, where the tibialis anticus immediately adheres to the solasus and tibialis posticus; but every where else it gives origin to muscular fibres. The Patella or Rotula Is a small flat bone situated at the forepart of the joint of the knee. Its shape resembles the common figure of the heart with its point downwards. The anterior convex surface of the rotula is pierced by a great number of holes, into which are inserted the fibres of the strong ligament that is spread over it. Its poste- rior surface is smooth, covered with cartilage, and divided by a middle convex ridge into two cavities, of which the external is largest; and both are exactly adapted to the pulley of the os femoris, on which they are placed in the most ordinary unstrain- ing postures of the legs : but, when the leg is much bent, the pa- tella descends far down on the condyles; and when the leg is fully extended, the patella rises higher in its upper part than the pul- ley of the thigh bone. The plane smooth surface is surrounded by a rough prominent edge, to which the capsular ligament adheres. Below, the point of the bone is scabrous, where the strong tendinous ligament from the tubercle of the tibia is fixed. The upper horizontal part of this bone is flattened and une- qual where the tendons of the extensors of the leg are inserted. The substance of the patella is cellular, with very thin firm ex- 16* 186 PATELLA. ternal plates; but then these cells are so small and such a quan- tity of bone is employed in their formation, that scarce any bone of its bulk is so strong. But, notwithstanding this strength, it is sometimes broken by the violent straining effort of the mus- cles. The principal motions of the knee joint are flexion and extension. In the former of these, the leg may be brought to a very acute angle with the thigh, by the condyles of the thigh bones being round, and made smooth far backwards. In performing this, the patella is pulled down by the tibia. When the leg is to be extended, the patella is drawn upwards, consequently, the tibia forwards, by the extensor muscles; which, by means of the protuberant joint, and of this thick bone with its ligament, have the chord, with which they act, fixed to the tibia at a considerable angle, and act, on that account, with advantage; but they are restrained from pulling the leg farther than to a straight line with the thigh, by the posterior part of the cross ligament, that the body might be supported by a firm perpendicular column: for, at this time, the thigh and leg are as little movable in a rotary way, or to either side, as if they were one continued bone. But, when the joint is a little bent, the rotula is not tightly braced, and the pos- terior ligament is relaxed ; therefore, this bone may be moved a little to either side, or with a small rotation in the superficial cavities of the tibia; which is done by the motion of the exter- nal cavity backwards and forwards, the internal serving as a sort of axis. Seeing, then, one part of the cross ligament is situated perpendicularly, and the posterior part is stretched ob- liquely from the internal condyle of the thigh outwards, that pos- terior part of the cross ligament prevents the leg from being turned much inwards; but it could not hinder it from turning outwards almost round, were not that motion confined by the lateral ligaments of this joint, which can yield little. This rotation of the leg outwards is of great advantage to us in crossing our legs, and turning our feet outwards, on several necessary occasions; though it is necessary that this motion should not be very large, to prevent frequent luxations here. While all these motions are performing, the part of the tibia that moves THE FOOT—TARSUS. 187 immediately on the condyles is that which is within the cartila- ginous rings, which, by the thickness on their outsides, make the cavities of the tibia more horizontal, by raising their external side where the surface of the tibia slants downwards. By these means the motions of this joint are more equal and steady than otherwise they would have been. The cartilages being capable of changing a little their situation, contribute to the different mo- tions and postures of the limb, and, likewise, make the motions larger and quicker. The Foot. The foot is divided into the tarsus, metatarsus, and toes. The sole of the foot is necessarily described as the inferior part, and the side of the great toe as the internal. Tarsus. The tarsus consists of seven spongy bones; to wit, the astra- galus, os calcis, naviculare, cuboides, cuneiforme externum, cunei- forme medium, and cuneiforme internum. The astragalus is the uppermost of these bones. The os calcis is below the astragalus, and forms the heel. The os naviculare is in the middle of the internal sides of the tarsus. The os cu- boides is the most external of the row of four bones, at its fore- part. The os cuneiforme externum is placed at the inside of the cuboid. The cuneiforme medium is between the external and internal cuneiforme bones; and the internal cuneiforme is at the internal side of the foot. The upper part of the astragalus is formed into a large smooth head, which is slightly hollowed in the middle; and therefore resembles a superficial pulley, by which it is fitted to the lower end of the tibia. The internal side of this head is flat and smooth, to play on the internal malleolus. The external side has also such a surface, but larger, for its articulation with the externa] malleolus. Round the base of this head there is a rough fossa; and immediately before the head, as also below its in- ternal smooth surface, we find a considerable rough cavity. The lower surface of the astragalus is divided by an irregular 188 ASTRAGALUS. deep rough fossa, which, at its internal end, is narrow, but gra- dually widens as it stretches obliquely outwards and forwards. The smooth surface, covered with cartilage, behind this fossa, is large, oblong, extended in the same oblique situation with the fossa, and concave for its conjunction with the os calcis. The posterior edge of this cavity is formed by two sharp-pointed rough processes, between which is a depression made by the tendon of the flexor pollicis longus. The lower surface before the fossa is convex, and composed of three distinct smooth planes. The long one behind, and the exterior or shortest, are articulated with the heel bone; while the internal, which is the most convex of the three, rests and moves upon a cartilaginous ligament, that is continued from the os calcis to the os navicu- lare, without which ligament the astragalus could not be sus- tained, but would be pressed out of its place by the great weight it supports; and the other bones of the tarsus would be separated. Nor would a bone be fit here, because it must have been thicker than could conveniently be allowed; otherwise it would break, and would not prove such an easy bending base, to lessen the shock which is given to the body, in leaping, running, &c. The forepart of this bone is formed into a convex oblong smooth head, which is received by the os naviculare, and is placed obliquely; its longest axis inclining downwards and in- wards. Round the root of this head, especially on the upper surface, a rough fossa may be remarked. The astragalus is articulated above to the tibia and fibula, which together form one cavity. In this articulation, flexion and extension are the most considerable motions; the other mo- tions being restrained by the malleoli, and by the strong liga- ments which go out from the points of these processes, to the astragalus and os calcis. When the root is bent, as it commonly is when we stand, no lateral or rotary motion is allowed in this joint; for then the head of the astragalus is sunk deep between the malleoli, and the ligaments are tense: but when the foot is extended, the astragalus can move a little to either side, and with a small rotation. By this contrivance, the foot is firm, when the weight of the body is to be supported on it; and, when OS CALCIS. 189 a foot is raised, we are at liberty to direct it more exactly to the place we intend next to step upon. The astragalus is joined below to the os calcis; and before to the os naviculare, in the manner to be explained when these bones are described. The os calcis is the largest bone of the seven. Behind, it is formed into a large knob, commonly called the heel, the poste- rior surface of which is rough below for the insertion of what is called the tendo-achillis, and oblique above to allow the heel to be depressed without pressing against the tendon. On the upper surface of the os calcis, there is an irregular oblong smooth convexity, adapted to the concavity at the back part of the astragalus; and beyond this a narrow fossa is seen, which divides it from two small concave smooth surfaces, that are joined to the forepart of the astragalus. The posterior of these smooth surfaces, which is the largest, is the upper surface of a process which projects inwards: and under it is a small sinuosity for the tendon of the flexor digitorum longus. The external side of this bone is flat, with a superficial fossa running horizontally, in which the tendon of the musculus pero- nasus longus is lodged. The internal side of the heel bone is hollowed, for lodging the origin of the massa carnea, and for the safe passage of tendons, nerves, and arteries. Under the side of the internal smooth concavity, a particular groove is made by the tendon of the flexor pollicis longus; and from the thin protuberance of this internal side a cartilaginous ligament that supports the astragalus, goes out to the os naviculare; bn which ligament, and on the edge of this bone to which it is fixed, the groove is formed for the tendon of the flexor digitorum pro- fundus. The lower surface of this bone is flat at the back part, and immediately before this plane, there are two tubercles, from the internal of which the musculus abductor pollicis, flexor digitorum sublimis, as also part of the aponeurosis plantaris, and of the ab- ductor minimi digiti, have their origin ; and the other part of the abductor minimi digiti and aponeurosis plantaris rises from the external. Before these protuberances, this bone is concave, for 190 os CUBOIDES. lodging the flexor muscles ; and, at its forepart, we may observe a rough depression, from which, and a tubercle behind it, the ligament goes out that prevents this bone from being separated from the os cuboides. The forepart of the os calcis is formed into an oblong pulley- like smooth surface, which is circular at its upper external end, but is pointed below. The smooth surface is fitted to the os cuboides. Though the surfaces by which the astragalus and os calcis are articulated, seem fit enough for motion, yet the very strong liga- ments, by which these bones are connected, prevent much mo- tion, and give firmness to this principal part of our base, which rests on the ground. Os naviculare is somewhat oval. It is formed into an oblong concavity behind, for receiving the anterior head of the astraga- lus. The upper surface is convex. Below, the surface is very unequal and rough; but hollow for the safety of the muscles. Its internal extremity is very prominent. The abductor pollicis takes in part its origin from it, the tendon of the tibialis posticus is inserted into it, and to it two remarkable ligaments are fixed; the first is the strong one, formerly mentioned, which supports the astragalus; the second is stretched from this bone obliquely across the foot, to the metatarsal bones of the middle toe, and of the toe next to the little one. On the outside of the os navi- culare there is a semicircular smooth surface, where it is joined to the os cuboides. The forepart of this bone is covered with cartilage, and divided into three smooth planes, fitted to the three ossa cuneiformia. The os naviculare and astragalus are joined as a ball and socket; and the naviculare moves in several directions in turn- ing the toes inwards, or in raising or depressing either side of the foot, though the motions are greatly restrained by the liga- ments which connect this to the other bones of the tarsus. Os cuboides is an irregular cube. Behind, it is formed into an oblong unequal cavity, adapted to the forepart of the os calcis. On its internal side, there is a small semicircular smooth cavity, to join the os naviculare. Immediately before which, an oblong OS CUNEIFORME. igj smooth plane is made by the os cuneiforme externum ; below this the bone is hollow and rough. On the internal side of the lower surface, a round protuberance and fossa are found, where the musculus adductor pollicis has its origin. On the external side of this surface, there is a broad ridge running forwards and inwards, covered with cartilage; immediately before which a smooth fossa may be observed, in which the tendon of the peronasus primus runs obliquely across the foot. Before, the surface of the os cuboides is flat, smooth, and slightly divided into two planes, for sustaining the os metatarsi of the little toe, and of the toe next to it. The form of the back part of the os cuboides, and the liga- ments connecting the joint with the os calcis, both concur in allowing little motion in this part. Os cuneiforme externum is shaped like a wedge, being broad and flat above, with long sides running obliquely downwards, and terminating in an edge. The upper surface of this bone is an oblong square. The one behind is nearly a triangle, but not complete at the inferior angle, and is joined to the os naviculare. The external side is an oblong square divided as it were by a diagonal; the upper half of it is smooth, for its conjunction with the os cuboides: the other is a scabrous hollow, with a small smooth impression made by the os metatarsi of the toe next to the little one. The internal side of this bone is flattened before by the metatarsal bone of the toe next to the great one, and the back part is also flat and smooth where the os cuneiforme medium is contiguous to it. The forepart of this bone is triangular, fof sustaining the os metatarsi of the middle toe. Os cuneiforme, or minimum, is still more exactly the shape of a wedge than the former. Its upper part is square; its internal side has a flat smooth surface for its connexion with the adjoin- ing bone; the external side is smooth and a little hollowed, where it is contiguous to the last described bone. Behind, this bone is triangular, where it is articulated with the os naviculare; and it is also triangular at its forepart, where it is contiguous to the os metatarsi of the toe next to the great one. The broad thick part of the os cuneiforme maximum, or in- ig2 METATARSUS. ternum, is placed below, and the small thinner edge is above. The surface of the os cuneiforme behind, where it is joined to the os naviculare, is hollow, smooth, and of a circular figure be- low, but pointed above. The external side consists of two smooth and flat surfaces. With the posterior, that runs ob- liquely forwards and outwards, the os cuneiforme minimum is joined; and with the anterior, whose direction is longitudinal, the os metatarsi of the toe next to the great one is connected. The forepart of this bone is flat and smooth, for sustaining the os metatarsi of the great toe. The internal side is scabrous, with two remarkable tubercles below, from which the musculus abductor pollicis rises, and the tibialis anticus is inserted into its upper part. The three cuneiforme bones are all so secured by ligaments, that very little motion is allowed in any of them. These seven bones of the tarsus, when joined, are convex above, and leave a concavity below, for lodging safely the seve- ral muscles, tendons, vessels, and nerves, that lie in the sole of the foot. In the recent subject, their upper and lower surfaces are covered with strong ligaments, which adhere firmly to them; and all the bones are so tightly connected by these and the other ligaments, which are fixed to the rough ridges and fossas, that notwithstanding the many surfaces covered with cartilage, some of which are of the form of the very movable articulations, no more motion is here allowed, than is necessary to prevent too great a shock of the fabric of the body in walking, leaping, &c. by falling on too solid a base. If the tarsus was one continued bone, it would likewise be much more liable to be broken, and the foot could not accommodate itself to the surfaces we tread on by becoming more or less hollow, or by raising or depressing either of its sides. Metatarsus. The Metatarsus is composed of five bones, which agree, in their general characters, with the metacarpal bones; but may be distinguished from them by the following marks: 1. They are longer, thicker, and stronger. 2. Their anterior round ends are METATARSUS. 193 not so broad, and are less in proportion to their bases. 3. Their bodies are sharper above and flatter on their sides, with their in- ferior ridge inclined more to the outside. 4. The tubercles at the lower part of the round head are larger. The first or internal metatarsal bone is easily distinguished from the rest by its thickness. The one next to it is the longest, and with its sharp edge almost perpendicular. The others are shorter and more oblique, as their situation is more external. Which general remarks, with the description now to be given of each, may teach us to distinguish them from each other. Os metatarsi pollicis is by far the thickest and strongest, as having much the greatest weight to sustain. Its base is oblong, irregularly concave, and of a semilunar figure, to be adapted to the os cuneiforme maximum. The inferior edge of this base is a little prominent and rough, where the tendon of the peronasus primus muscle is inserted. On its outside, an oblique circular depression is made by the second metatarsal bone. Its round head has generally on its forepart a middle ridge, and two ob- long cavities, for the ossa sesamoidea; and, on the external side, a depression is made by the following bone. Os metatarsi of the second toe is the longest of the five, with a triangular base supported by the os cuneiforme medium, and the external side produced into a process; the end of which is an oblique smooth plane, joined to the os cuneiforme externum. Near the internal edge of the base, this bone has two small de- pressions, made by the os cuneiforme maximum, between which is a rough cavity. Farther forwards we may observe a smooth protuberance, which is joined to a foregoing bone. On the out- side of the base are two oblong smooth surfaces for its articula- tion with the following bone; the superior smooth surface being extended longitudinally, and the inferior perpendicularly, be- tween which there is a rough fossa. Os metatarsi of the middle toe is the second in length. Its base, supported by the os cuneiforme externum, is triangular, but slanting outwards, where it ends in a sharp-pointed little process, and the angle below it is not completed. The internal side of this base is best adapted to the preceding vol. i. 17 194 TH£ TOES. bone; and the external side has also two smooth surfaces covered with cartilage, but of a different figure; for the upper one is concave, and being round behind, turns smaller as it advances forwards; and the lower surface is a little smooth, convex, and very near the edge of the base. Os metatarsi of the fourth toe is nearly as long as the former, with a triangular slanting base joined to the os cuboides, and made round at its external angle; having one hollow smooth surface on the outside, where it is pressed upon by the following bone; and two on the internal side, corresponding to the former bone, behind which is a long narrow surface impressed by the os cuneiforme externum. Os metatarsi of the little toe is the shortest, situated with its two flat sides above and below, and with the ridges laterally. The base of it, part of which rests on the os cuboides, is very large, tuberous, and produced into a long-pointed process ex- ternally, where part of the abductor minimi digiti is fixed; and into its upper part the peronasus secundus is inserted. Its inside has a flat conoidal surface, where it is contiguous to the pre- ceding bone. When we stand the fore ends of these metatarsal bones, and the os calcis, are our only supporters, and, therefore, it is neces- sary that they should be strong, and should have a confined mo- tion. The Toes. The bones of the toes are nearly similar to those of the thumb and fingers; particularly the two of the great toe, which are precisely formed as the two last of the thumb; but their position, as respects the other toes, is not oblique; and they are propor- tionally much stronger, because they are subjected to a greater force; for they sustain the force by which our bodies are pushed forwards by the foot behind at every step we make; and on them principally the weight of the body is supported, when we are raised on our tip-toes. The three bones in each of the other four toes, compared with those of the fingers, differ from them in these particulars. STRUCTURE OF THE FOOT. I95 They are less, and smaller in proportion to their lengths'. Their bases are much larger than their anterior ends. The first pha- lanx is proportionally much longer than the bones of the second and third, which are very short. The toe next to the great one has the largest bones in all di- mensions, and the bones of the other toes diminish according to the order of their position; those of the exterior being least. The general Structure of the Foot. The foot may be considered as an arch, of which the back part of the heel, and the anterior extremities of the metatarsal bones and the toes, are the abutments. The heel, or posterior abutment, is not so broad as the anterior, and is placed on the outside and not in the middle of the extremity of the arch. The process on the inside of the os calcis, which supports the astra- galus, increases the breadth of the arch; and the os naviculare completes it. The arch, thus constructed, does not appear very firm, and this apparent want of strength seems increased by the position of the anterior portion of the astragalus, a part of which is between the os calcis and os naviculare, and not supported by either. These bones, however, are firmly connected by liga- ments, and one which passes from the os calcis to the os navicu- lare, under the forepart of the astragalus, gives effectual support to that bone. The outside of the foot, formed by the os calcis, os cuboides, and the lesser metatarsal bone, does not partake much of the nature of an arch; for it is almost flat. As the internal side forms a considerable arch, the foot is to be considered as possessing a double convexity, viz. transversely, as well as longitudinally. The great toe, from its internal situation, is the principal ante- rior abutment of the arch on the internal side of the foot; hence its great importance. The astragalus, which is the basis of the tibia, and of course pressed by half of the weight of the body when we stand, appears to be in a situation which is very oblique, and imperfectly sup- ported; and accordingly it has been completely forced from its position, by accidents in which the leg has been twisted or turned 190 SESAMOID BONES-EXTREMITIES OF THE FCETUS. inward, and the foot prevented from turning with it. It is pro- bable that this misfortune would often take place if the fibula did not previously yield, as in some of the cases of fracture of that bone near the external ankle. One great object of this peculiar structure is, that the foot may yield in cases of violent and sudden pressure, as when we jump or fall upon the feet. The safety of the foot, and the facility of its ordinary movement, are not the only objects of its peculiar structure, but concussion of the whole body, and particularly of the brain, is thereby avoided to a certain degree. This may be inferred from the fact that many persons suffer violent concussions, in consequence of falling upon other parts of the body, who are free from these effects when they fall upon the feet. The Sesamoid Bones Are seldom larger than half a pea. They are most commonly found at the second joint of the thumb, and of the great toe; and are placed in pairs, especially at the great toe, between the tendons of the flexor muscles and the bones. In these situations they are convex externally, and on their interna] surfaces they are concave and covered with cartilage. They are also sometimes found between the heads of the gastrocnemius muscle and the condyles of the os femoris. In the joints of the thumb and toe they appear to be very analogous to the patella. The Extremities of the Foetus. In the upper extremity the clavicle is almost perfect at birth; but the acromion and coronoid processes of the scapula, as well as the head, are in a cartilaginous state. Both ends of the os humeri are cartilaginous. They after- wards ossify in the form of epiphyses, and are united to the body of the bone. The two bones of the forearm are in the same situation. There are no bones of the carpus; but in their situation is an equal number of cartilages, which resemble them exactly. These EXTREMITIES OF THE FCETUS 197 cartilages are separated from each other, by synovial membranes, as the bones afterwards are. Each of them ossifies from a single point, except the unciforme. The metacarpal bones, and the first bone of the thumb, have cartilages at each extremity, which afterwards become epiphyses. The bones of the phalanges are likewise cartilaginous at each extremity. The extremities next to the hand are epiphyses; but it is probable that the other extremities ossify gradually from their centres.* In the lower extremity, the head and neck, and two trochanters of the os femoris are cartilaginous and form three epiphyses. The other end of this bone is also cartilaginous, and constitutes but one epiphysis, notwithstanding its size; the ossification com- mencing in the centre. At birth, the body of the os femoris is less curved than it becomes afterwards; and the angle formed by the neck of the bone is less obtuse than in the adult. The patella is entirely cartilaginous at birth. The two extremities of the tibia and fibula are also cartilagi- nous, and become epiphyses. The astragalus and os calcis are somewhat ossified within, and have a large portion of cartilage exteriorly. In place of the other bones of the tarsus there are cartilages of their precise shape, which are as distinct from each other as the future bones are. The state of the metatarsal bones, and the phalanges of the toes, resembles that of the bones of the hand.f * See Nesbit's Osteology, page 126. t Volehn Koyter, a disciple of Fallopius, has given to the profession one of the best accounts of Osteogeny, according to Lassus.—h. 17* 199 ANATOMICAL PLATES. EXPLANATION OF THE PLATES OF OSTEOLOGY. Plate II. Fig. 1. A Front View of the Male Skeleton. A, The os frontis. B, The os parietale. C, The coronal suture. D, The squamous part of the temporal bones. E, The squamous suture. F, The zygoma. G, The mastoid process. H, The temporal process of the sphenoid bone. I, The orbit. K, The os mate. L, The os maxillare su- perius. M, Its nasal process. N. The ossa nasi. 0, The os unguis. P, The maxilla inferior. Q, The teeth, which are sixteen in number in each jaw. R, The seven cervical vertebrae, with their intermediate cartilages. S, Their transverse processes. T, The twelve dorsal vertebra?, with their intermediate cartilages. U, The five lumbar vertebra?. V, Their trans- verse process. W, The upper part of the os sacrum. X, Its lateral parts. The holes seen on its forepart are the passages of the undermost spinal nerves and small vessels. Opposite to the holes, the marks of the original division of the bones are seen. Y, The os ilium. Z, Its crest or spine, a, The interior spinous processes, b, The brim of the pelvis, c, The ischi- atic notch, d, The os ischium, e, Its tuberosity, f, Its spinous process. g, Its crus. h, The foramen thyroideum. i, The os pubis, k, The sym- physis pubis. 1, The crus pubis, m, The acetabulum, n, The seventh or last true rib. o, The twelfth or last false rib. p, The upper end of the sternum, q, The middle piece, r, The upper end, or cartilago ensiformis. s, The clavicle, t, The internal surface of the scapula, u, Its acromion. v, Its coracoid process, w, Its cervix, x, The glenoid cavity, y, The os humeri, z, Its head, which is connected to the glenoid cavity. 1, Its in- ternal tubercle. 2, Its external tubercle. 3, The groove for lodging the long head of the biceps muscle of the arm. 4, The internal condyle. Be- tween 4 and 5, the trochlea. 6, The radius. 7, Its head. 8, Its tubercle. 9, The ulna. 10, Its coronoid process. 11, 12, 13, 14, 15, 16, 17, 18, The carpus, composed of the os naviculare, os lunare, os cuneiforme, os pisi- forme, os trapezium, os trapezoides, os magnum, os unciforme. 19, The five bones of the metacarpus. 20, The two bones of the thumb. 21, The three bones of each of the fingers. 22, The os femoris. 23, Its head. 24, Its cervix. 25, The trochanter major. 26, Trochanter minor. 27, The in- ternal condyle. 28, The external condyle. 29, The rotula. 30, The ti- bia. 31, Its head. 32, Its tubercle. 33, Its spine. 34, The malleolus in- ternus. 35, The fibula. 36, Its head. 37, The malleolus externus. The tarsus is composed of, 38, The astragalus; 39, The os calcis; 40, The os naviculare; 41, Three ossa, cuneiformia, and the os cuboides, which is not 200 EXPLANATION OF THE PLATES OF OSTEOLOGY. seen in this figure. 42, The five bones of the metatarsus. 43, The two bones of the great toe. 44, The three bones of each of the small toes. Fig. 2. A Front View of the Skull. A, The os frontis. B, The lateral part of the os frontis, which gives origin to part of the temporal muscle. C, The superciliary ridge. D, The superciliary hole through which the frontal vessels and nerves pass. E E, The orbitar processes. F, The middle of the transverse suture. G, The upper part of the orbit. H, The foramen opticum. I, The foramen lacerum. K, The inferior orbitar fissure. L, The os unguis. M, The ossa nasi. N, The os maxillare superius. O, Its nasal process. P, The ex- ternal orbitar hole through which the superior maxillary vessels and nerves pass. Q. The os mate. R, A passage for small vessels into or out of the orbit. S, The under part of the left nostril. T, The septum narium. U, The os spongiosum superius. V, The os spongiosum inferius. W, The edge of the alveoli, or spongy sockets for the teeth. X, The maxilla infe- rior. Y, The passage for the inferior maxillary vessels and nerves. Fig. 3. A Side View of the Skull. A, The os frontis. B, The coronal suture. C, The os parietale. D, An arched ridge, which gives origin to the temporal muscle. E, The squamous suture. F, The squamous part of the temporal bone; and farther forwards, the temporal process of the sphenoid bone. G, The zygomatic process of the temporal bone. H, The zygomatic suture. I, The mastoid process of the temporal bone. K, The meatus auditorius externus. L, The orbitar plate of the frontal bone, under which is seen the transverse suture. M, The pars plana of the ethmoid bone. N, The os unguis. O, The right os nasi. P, The superior maxillary bone. Q, Its nasal process. R, The two dentes incisores. S, The dens caninus. T, The two small molares. U, The three large molares. V, The os mate. W, The lower jaw. X, Its angle. Y, The coronoid process. Z, The condyloid process by which the jaw is articulated with the temporal bone. Fig. 4. The Posterior and Right Side of the Skull. A, The os frontis. BB, The ossa parietalia. C, The sagittal suture. D, The parietal hole, through which a small vein runs to the superior longi- tudinal sinus. E, Thelambdoid suture. FF, Ossa triquetra. G, The os occipitis. H, The squamous part of the temporal bone. I, The mastoid process. K, The zygoma. L, The os mate. M, The temporal part of the sphenoid bone. N, The superior maxillary bone and teeth. Fig. 5. The External Surface of the Os Frontis. A, The convex part. B, Part of the temporal fossa. C, The external angular process. D, The internal angular process. E, The nasal process. F, The superciliary arch. G, The superciliary hole. H, The orbitar plate. Fig. 6. The Internal Surface of the Os Frontis. A A, The serrated edge which assists to form the coronal suture. B, The external angular process. C, The internal angular process. D, The nasal process. E, The orbitar plate. F, The cells which correspond with those EXPLANATION OF THE PLATES OF OSTEOLOGY. 201 of the ethmoid bone. G, The passage from the frontal sinus. H, The opening which receives the cribriform plate of the ethmoid bone. I, The cavity which lodges the forepart of the brain. K, The spine to which the falx is fixed. L, The groove which lodges the superior longitudinal sinus. Plate III. Fig. 1. A Back View of the Skeleton. A A, The ossa parietalia. B, The sagittal suture. C, The lambdoid su- ture. D, The occipital bone. E, The squamous suture. F, The mastoid process of the temporal bone. G, The os mate. H, The palate plates of the superior maxillary bone. I, The maxilla inferior. K, The teeth of both jaws. L, The seven cervical vertebra?. M, Their spinous processes. N, Their transverse and oblique processes. O, The last of the twelve dor- sal vertebra?. P, The fifth or last lumbar vertebra?. Q, The transverse processes. R, The oblique processes. S, The spinous process. T, The upper part of the os sacrum. U, The posterior holes which transmit small blood-vessels and nerves. V, The under part of the os sacrum which is co- vered by a membrane. W, The os coccygis. X, The os ilium. Y, Its spine or crest. Z, The isehiatic notch, a, The os ischium, b, Its tube- rosity, c, Its spine, d, The os pubis, e, The foramen thyroideum. f, The seventh or last true rib. g, The twelfth or last false rib. h, The clavicle. i, The scapula, k, Its spine. 1, Its acromion, m, Its cervix, n, Its su- perior costa. o, Its posterior costa. p, Its inferior costa. q, The os hu- meri, r, The radius, s, The ulna, t, Its olecranon, u, All the bones of the carpus, excepting the os pisiforme, which is seen in Plate II. Fig. 1. v, The five bones of the metacarpus, w, The two bones of the thumb, x, The three bones of each of the fingers, y, The two sesamoid bones of the root of the left thumb, z, The os femoris. 1, The trochanter major. 2, The trochanter minor. 3, The linea aspera. 4, The internal condyle. 5, The external condyle. 6 6, The semilunar cartilages. 7, The tibia. 8, The malleolus internus. 9, The fibula. 10, The malleolus externus. 11, The tarsus. 12, The metatarsus. 13, The toes. Fig. 2. The External Surface of the left Os Parietale. A, The convex smooth surface. B, The parietal hole. C, An arch made by the beginning of the temporal muscle. Fig. 3. The Internal Surface of the same Bone. A, Its superior edge, which, joined with the other, forms the sagittal su- ture. B, The anterior edge, which assists in the formation of the coronal su- ture. C, The inferior edge for the squamous suture. D, The posterior edge for the lambdoid suture. E, A depression made by the lateral sinus. F, The prints of the arteries of the dura mater. Fig. 4. The External Surface of the left Os Temporis. A, The squamous part. B, The mastoid process. C, The zygomatic process. D, The styloid process. E, The petrosal process. F, The mea- tus auditorius externus. G, The glenoid cavity for the articulation of the lower jaw. H, The foramen stylo-mastoideum for the portio dura of the seventh pair of nerves. I, Passages for blood-vessels into the bone. K, The foramen mastoideum, through which a vein goes to the lateral sinus. 202 EXPLANATION OF THE PLATES OF OSTEOLOGY. Fig. 5. The Internal Surface of the left Os Temporis. A, The squamous part, the upper edge of which assists in forming the squamous suture. B, The mastoid process. C, The styloid process. D, The pars petrosa. E, The entry of the seventh pair, or auditory nerve. F, The fossa, which lodges a part of the lateral sinus. G, The foramen mastoideum. Fig. 6. The External Surface of the Osseous Circle, which terminates the Meatus Auditorius Externus. A, the anterior part. B, A small part of the groove in which the mem- brana tympani is fixed. N. B. This, with the subsequent bones of the ear, are here delineated as large as the life. Fig. 7. The Internal Surface of the Osseous Circle. A, the anterior part. B, the groove in which the membrana tympani is fixed. Fig. 8. The Situation and Connexion of the Small Bones of the Ear. A, The malleus. B, The incus. C, the os orbiculare. D, The stapes. Fig. 9. The Malleus, with its Head, Handle, and Small Processes. Fig. 10. The Incus, with its Body, Superior and Inferior Branches. Fig. 11. The Os Orbiculare. Fig. 12. The Stapes, with its Head, Base, and two Crura. Fig. 13. An Internal View of the Labyrinth of the Ear. A, The hollow part of the cochlea, which forms a share of the meatus au- ditorius internus. B, The vestibulum. C C C, The semicircular canals. Fig. 14. An External View of the Labyrinth. A, the semicircular canals. B, The fenestra ovalis, which leads into the vestibulum. C, The fenestra rotunda which opens into the cochlea. D, The different turns of the cochlea. Fig. 15. The Internal Surface of the Os Sphenoides. A A, The temporal processes. B B, The pterygoid processes. C C, The spinous processes. D D, The anterior clinoid processes. E, The posterior clinoid process. F, The anterior process which joins the ethmoid bone. G, The sella turcica for lodging the glandula pituitaria. H, The foramen op- ticum. K. The foramen lacerum. L, The foramen rotundum. M, The foramen ovale. N, The foramen spinale. Fig. 16. The External Surface of the Os Sphenoides. A A, The temporal processes. B B, The pterygoid processes. C C. The spinous processes. D, The processus azygos. E, The small triangular pro- 9320 EXPLANATION OF THE PLATES OF OSTEOLOGY. 203 cesses which grow from the body of the bone. F F, The orifices of the sphe- noid sinuses. G, The foramen lacerum. H, The foramen rotundum. I, The foramen ovale. K, The foramen pterygoideum. Fro. 17. The External View of the Os Ethmoides. A, The nasal lamella. B B, The grooves between the nasal lamella and ossa spongiosa superiora. CC, The ossa spongiosa superiora. DD, The sphenoidal cornua. See Fig. 16, E. Fig. 18. The Internal View of the Os Ethmoides. A, The crista galli. B, The cribriform plate, with the different passages of the olfactory nerves. C C, Some of the ethmoidal cells. D, The right os planum. EE, The sphenoidal cornua. Fig. 19. The right Sphenoidal Cornu. Fig. 20. The left Sphenoidal Cornu. Fig. 21. The External Surface of the Os Occipitis. A, The upper part of the bone. B, The superior arched ridge. C, The inferior arched ridge. Under the arches are prints made by the muscles of the neck. D D, The two condyloid processes which articulate the head with the spine. E, The cuneiforme process. F, The foramen magnum through which the spinal marrow passes. GG, The posterior condyloid fora- mina which transmit veins into the lateral sinuses. H H, The foramina lin- gualia for the passage of the ninth pair of nerves. Fig. 22. The Internal Surface of the Os Occipitis. A A, The two sides which assist to form the lambdoid suture. B, The point of the cuneiforme process, where it joins the sphenoid bone. C C, The prints made by the posterior lobes of the brain. D D, Prints made by the lobes of the cerebellum. E, The cruciforme ridge for the attachment of the process of the dura mater. F, The course of the superior longitudinal sinuses. GG, The course of the two lateral sinuses. H, The foramen magnum. 11, The posterior condyloid foramina. Plate IV. Fig. 1. A Side View of the Skeleton. A A, The ossa parietalia. B, The sagittal suture. C, The os occipitis. DD, The lambdoid suture. E, The squamous part of the temporal bone. F, The' mastoid process. G, The meatus auditorius externus. H, The os frontis I, The os mate. K, The os maxillare superius. L, The maxilla inferior M, The teeth of both jaws. N, The seventh or last cervical vertebra O, The spinous processes. P, Their transverse and oblique pro- cesses Q, The twelfth or last dorsal vertebra. R, The fifth or last lum- bar vertebra. S, The spinous processes. T, Openings between the ver- tebra? for the passage of the spinal nerves. U, The under end of the os sacrum. V, The os coccygis. W, The os ilium. X, The anterior spinous processes Y, The posterior spinous processes. Z, Ischiatic notch, a, Ihe riffht os ilium, b, The ossa pubis, c, The tuberosity of the left os ischium. d, The scapula, e, Its spine, f, The os humeri, g, The radius, h, Ihe 204 EXPLANATION OF THE PLATES OF OSTEOLOGY. ulna, i, The carpus, k, The metacarpal bone of the thumb. 1, The meta- carpal bones of the fingers, m, The two bones of the thumb, n, The three bones of each of the fingers, o, The os femoris. p, Its head, q, The trochanter major, r, The external condyle, s, The rotula. t, The tibia, u, The fibula, v, The malleolus externus. w, The astragalus, x, The os calcis. y, The os naviculare. z, The threeossa cuneiformia. 1, The os cuboides. 2, The five metatarsal bones. 3, The two bones of the great toe. 4, The three bones of each of the small toes. Fig. 2. A View of the Internal Surface of the Base of the Skull. AAA, The two tables of the skull with the diploe. B B, The orbitar plates of the frontal bone. C, The crista galli, with cribriform plate of the ethmoidal bones on each side of it, through which the first pair of nerves pass. D, The cuneiforme process of the occipital bone. E, The cruciforme ridge. F, The foramen magnum for the passage of the spinal marrow. G, The zygoma, made by the joining of the zygomatic processes of the os tem- porum and os mate. H, The pars squamosa of the os temporis. I, The pars mammillaris. K, The pars petrosa. L, The temporal process of the sphenoid bone. M M, The anterior clinoid processes. N, The posterior clinoid process. O, The sella turcica. P, The foramen opticum for the passage of the optic nerve and ocular artery of the left side. Q, The fora- men lacerum, for the third, fourth, sixth, and first of the fifth pair of nerves and ocular vein. R, The foramen rotundum, for the second of the fifth pair. S, The foramen ovale, for the third of the fifth pair. T, The foramen spinale, for the principal artery of the dura mater. U, The entry of the auditory nerve. V, The passage for the lateral sinus. W, The pas- sage of the eighth pair of nerves. X, The passage of the ninth pair. Fig. 3. A View of the External Surface of the Base of the Skull. A, The two dentes incisores of the right side. B, The dens caninus. C, The two small molares. D, The three large molares. E, The foramen incisivum, which gives passage to small blood-vessels and nerves. F, The palate plates of the ossa maxillaria and palati, joined by the longitudinal and transverse palate sutures. G, The foramen palatinum posterius, for the pa- latine vessel and nerves. H, The os maxillare superius of the right side. I, The os mate. K, The zygomatic process of the temporal bone. L, The posterior extremity of the ossa spongiosa. M, The posterior extremity of the vomer which forms the back part of the septum nasi. N, The ptery- goid process of the right side of the sphenoid bone. O O, The foramina ovalia. P P, The foramina spinalia. Q, Q, The passages of the internal carotid arteries. R, A hole between the point of each pars petrosa and cuneiforme process, of the occipital bone, which is filled with a ligamentous substance in the recent subject. S, The passage of the left lateral sinus. T, The posterior condyloid foramen of the left side. U, The foramen mas- toideum. V, The foramen magnum. W, The inferior orbitar fissure. X, The glenoid cavity, for the articulation of the lower jaw. Y, The squam- ous part of the temporal hone. Z, The mastoid process, at the inner side of which is a fossa for the posterior belly of the digastric muscle, a, The sty- loid process, b, The meatus auditorius externus. c, The left condyle of the occipital bone, d, The perpendicular occipital spine, e e, The inferior horizontal ridge of the occipital bone, f f. The superior horizontal ridge which is opposite to the crucial ridge where the longitudinal sinus divides to form the lateral sinuses, ggg, The lambdoid suture, h, The left squamous suture, i, The parietal bone. explanation of the plates of osteology. 205 Fig. 4. The Anterior Surface of the Ossa Nasi. A, The upper part which joins the os frontis. B, The under end, which joins the cartilage of the nose. C, The inner edge, where they join each other. Fig. 5. The Posterior Surface of the Ossa Nasi. A A, Their cavity, which forms part of the arch of the nose. B B, Their ridge or spine, which projects a little to be fixed to the forepart of the sep- tum narium. Fig. 6. The External Surface of the Os Maxillare Superius of the left side. A, The nasal process. B, The orbitar plate. C, The unequal surface which joins the os mate. D. The external orbitar hole. E, The opening into the nostril. F, The palate plate. G, The maxillary tuberosity. H, Part of the os palati. I, The two dentes incisores. K. The dens caninus. L, The two small dentes molares. M, The three large dentes molares. Fig. 7. The Internal Surface of the Os Maxillare Superius and Os Palati. A, The nasal process. B B, Eminences for the connexion of the os spon- giosum inferius. D, The under end of the lachrymal groove. E, The an- trum maxillare. F, The nasal spine, between which and B is the cavity of the nostril. G, The palate plate. H, The orbitar part of the os palati. I, The nasal plate. K, The suture which unites the maxillary and palate bones. The pterygoid process of the palate bone. Fig. 8. The External Surface of the right Os Unguis. A, The orbitar part. B, The lachrymal part. C, The ridge between them. Fig. 9. The Internal Surface of the right Os Unguis. This side of the bone has a furrow opposite to the external ridge; all be- hind this is irregular, where it covers part of the ethmoidal cells. Fig. 10. The External Surface of the left Os Mal,e. A, The superior orbitar process. B, The inferior orbitar process. C, The malar process. D, The zygomatic process. E, The orbitar plate. F, A passage for small vessels into or out of the orbit. Fig. 11. The Internal Surface of the left Os MaljE. A, The superior orbitar process. B, The inferior orbitar process. C, The malar process. D, The zygomatic process. E, The internal orbitar plate or process. Fig. 12. The External Surface of the right Os Spongiosum Inferius. A, The anterior part. B, The hook-like process for covering part of the vol. I. 18 206 explanation of the plates of osteology. antrum maxillare. C, A small process which covers part of the under end of the lachrymal groove. D, The inferior edge turned a little outwards. Fig. 13. The Internal Surface of the Os Spongiosum Inferius. A, The anterior extremity. B, The upper edge which joins the superior maxillary and palate bones. Fig. 14. The Posterior and External Surface of the right Os Palati. A, The orbitar process. B, The nasal lamella. C, The pterygoid pro- cess. D. The palate process. Fig. 15. The Interior and External Surface of the right Os Palati. A, The orbitar process. B, An opening through which the lateral nasal vessels and nerves pass. C, The nasal lamella. D, The pterygoid process. E, The posterior edge of the palate process for the connexion of the velum palati. F, The inner edge by which the two ossa palati are connected. Fig. 16. The Right Side of the Vomer. A, The upper edge which joins the nasal lamella of the ethmoid bone and the middle cartilage of the nose. B, The inferior edge, which is connected to the superior maxillary and palate bones. C, The superior and posterior part which receives the processus azygos of the sphenoid bone. Fig. 17. The Maxilla Inferior. A, The chin. B, The base and left side. C, The angle. D, The coro- noid process. E, The condyloid process. F, The beginning of the inferior maxillary canal of the right side, for the entry of the nerves and blood-ves- sels. G, The termination of the left canal. H, The two dentes incisores. I, The dens caninus. K, the two small molares. L, The three large mo- lares. Fig. 18. The Different Classes of the Teeth. 1, 2, A fore and back view of the two anterior dentes incisores of the lower jaw. 3, 4, Similar teeth of the upper jaw. 5, 6, A fore and back view of the dentes canini. 7, 8, The anterior dentes molares. 9, 10, 11, The posterior dentes molares. 12, 13,14,15, 16, Unusual appearances in the shape and size of the teeth. Fig. 19. The External Surface of the Os Hyoides. A, The body. B B, The cornua. C C, The appendices. PART II. SYNDESMOLOGY. CHAPTER III. GENERAL ANATOMY OF THE LIGAMENTOUS, FIBROUS, OR DESMOID TISSUE. Of the ligaments and membranes which connect the different parts of the body to each other—Of the articular cartilages—Fibro-cartilages—Synovial capsules, and particular articulations. The tendons and the strong membranes connected with them called aponeuroses, the fascia which bind down some of the muscles and afford an origin to many of their fibres, and the membranes which confine the tendons, appear to be composed of the same substance. —Notwithstanding some slight shades of difference which exist in the physical and chemical composition of these different parts, they are all now included with the periosteum, perichon- drium, dura mater, sclerotic coat of the eye, &c, under the gene- ral head of ligamentous, fibrous, or desmoid tissue.* This tissue is sometimes called, from the whiteness of its appearance, the albugineous tissue. It is spread very generally throughout the body, and is found wherever extraordinary strength and resist- ance is required, without elasticity or muscular contraction. It has been called ligamentous or desmoid, from its fastening to- gether the bones and cartilages, as in the ligaments proper, and from binding down the muscles so as to preserve the symmetry * The term ligament is frequently/though not with exact propriety applied to the duplicatures of serous membranes, which are attached to and assist in sup- porting different viscera, as the liver, bladder, uterus, &c, since these doubtless do not belong to the fibrous or desmoid tissue.—p. 208 FIBROUS TISSUE. of the limbs, in the form of fascia and aponeurosis, and from fastening the tendons in their grooves in the form of their theca's or sheaths. The term fibrous'was applied to it by Bichat, (though its elements are dissimilar to muscular fibre,) in consequence of its performing the office of bands or chords, and being composed essentially of firm inelastic threads, or albuminous fibres. These fibres crossing each other in various directions and woven dense- ly together, with some intervening cellular tissue, form the apo- neuroses, fasciae, sheaths, articular capsules, periosteum, dura mater, and tunica albuginea; arranged longitudinally, they form the tendons of the muscles and the straight ligaments of the joints. The tendons, by a little dissection, may be spread out into a membrane, and in some parts of the body we see them naturally unfolding themselves to form an aponeurosis. —Between all these different parts there is more or less con- nexion. The tendons are inserted upon the bones only through the intermedium of the periosteum, by which they are covered. The aponeuroses are connected with the periosteum by the fasciae which they send down between the muscles. The ligaments and periosteum are directly continuous, and the dura mater, as it sends out processes around the nerves, becomes continuous with the periosteum that lines the foramina of the bones, through which the nerves pass. Bichat, considered the periosteum the source and centre of this system; Bonn, of Amsterdam, as well as Clarus, believed the aponeuroses investing the limbs to be the centre;—an opinion more venerable than either of these, that of the Arabian anatomists, fixed it in the dura mater. But, in truth there is no proper centre. In many parts, there is a fibrous tissue isolated from the rest, as the investing coat of the spleen and kidneys, and the fibrous portion of the pericardium. —The fibrous tissue in all parts of 4he body is continuous, at its surfaces and margins, with the common cellular tissue, and in many parts we find it, especially in the aponeuroses and fasciae, degenerating insensibly into it. There appears in fact to be a close relationship between these two tissues; in its developement in the foetus, it first appears as a soft, flexible, extensible, homo- geneous tissue, resembling much the cellular, and presents no ap- FIBROUS TISSUE. 209 pearance of fibres, till near the period of birth. As life advances it becomes more hard, solid and yellow, and in extreme old age presents much rigidity, and is occasionally even converted into bone. When macerated in water, or imbued with fluids, as in scrofulous inflammation of the joints, it presents a pulpy, spongy appearance, in the cells of which the fluid is contained. If the maceration is carried only to a limited extent, the fibres will separate into filaments, as delicate as those of the silk worm; but by prolonged maceration these filaments themselves disap- pear in the cellular mass. Mascagni, believed these fibres were lymphatics enclosed in a vascular web. Beclard, that they were nothing but condensed cellular tissue. Isenflam, that it was cellular tissue, with the walls imbued and the cells filled with gluten and albumen, and more or less in the advance of life with earthy matter; an opinion which seems to accord with the dif- ferent phases which the tissue presents. Chaussier and Bichat, considered the fibre as primitive and peculiar, and that macera- tion only brought into view the cellular tissue which connected the fibres together. —However this may be, and it is a question not yet decided, in the form in which it presents itself to study, it differs in many respects from cellular tissue. It is not elastic or yielding to the application of sudden force as the latter; the fibres will break or tear up at their bony attachment, but cannot be stretched or strained in the proper sense of the word. But when the force is gradually applied, as by the accumulation of a fluid in a joint, they yield to receive it, by a sort of interstitial expansion or growth, and retract in the same gradual manner, when the dis- tending power is removed. Fibrous tissue contains but little adipose matter, and is affected only to a slight extent in ana- sarca. The Ligaments of the Joints, —Are all divided into the capsular or bag-like, and into funicu- lar, or cords. —The capsular, are fibrous bags, of greater or less thickness, open at both ends, into which the heads of the bones forming the 18* 210 FIBROUS TISSUE. respective joints are thrust, and round.the necks of which it is closely inserted, where they are continuous with the periosteum of the bones. In very many of the joints the capsules are im- perfect in some part of their periphery, and in others are repre- sented only by a few scattered fibres. The hip and shoulder joint furnish the best specimen of a perfect capsule. —The funicular ligaments are cords, flat, round, or oval, in- tended to give a side support to the joints, and constitute the lateral ligaments. These are placed, some within, some without, and some in the very thickness of the capsular ligament.— They consist of fibres which are flexible but extremely strong, and in general have but little elasticity; their surfaces are smooth and polished; their colour is whitish and silver-like. The vessels which enter into their composition do not com- monly carry red blood ; and although it seems certain that they must have nerves, many very expert anatomists have declared that no nerves could be traced into them. In a healthy state, they are entirely void of sensibility, and can be cut and punctured, or corroded with caustic applications, without pain. When inflamed they are extremely painful. The ligaments which connect the different bones to each other, have a very strong resemblance to these tendinous parts, not only in their structure but in their qualities also. Many of them appear rather more firm in their texture and more vascular. Their vessels are also larger; their colour sometimes inclines to a dull white, and when examined chemically, they appear to differ, in some respects, from tendons. They agree, however, with the tendinous parts as to their in- sensibility in a sound state, and the extreme pain which occurs when they are inflamed. No nerves have been traced into their structure. Notwithstanding the ordinary insensibility of these parts, it was asserted by M. Bichat that several animals who seem to suffer no pain from cutting, puncturing, or corroding the liga- ments of their joints, appeared to be in great agony when these parts were violently stretched or twisted; and he declared this to be the case when all the nerves which passed over the liga- FIBROUS TISSUE. Ol I ments, and could have been affected by the process, were cut away. He explained by this the pain which sometimes occurs instantaneously in sprains, in the reduction of luxations, and in other analogous processes. The ultimate structure of these parts is, perhaps, not perfectly understood. An anatomist of the highest authority, Haller, appears to have considered them as formed of membrane, while a late writer, who has paid great attention to the subject, and is also, of high authority, M. Bichat, has satisfied himself that their structure is essentially fibrous. If a tendon, or portion of tendinous membrane, be spread out, or forcibly extended, in a direction which is transverse with re- spect to its fibres, it will seem to be converted into a fine mem- brane, and the fibres will disappear to the naked eye. The same circumstances will occur when a ligament is treated in a similar way; but much more force is required. Thus constructed, these parts are perfectly passive portions of the animal fabric, and have no more power of motion than the bones with which many of them are connected. But notwithstanding their ordinary insensibility, they often in- duce a general violent affection of the system when they are dis- eased. A high degree of fever, as well as severe pain, attends their acute inflammations; and hectical symptoms, in their great- est extent, are often induced by their suppurations. There is another circumstance in their history which is very difficult to reconcile with their ordinary insensibility. They are the most common seats of gouty painful affections. In these cases, pain does not seem to be the simple effect of inflammation: it often occurs as the first symptom of the disease; it frequently exists with great violence for a short time and goes off without inflammation, and it is frequently vicarious with af- fections of the most sensible and irritable parts. Parts of a tendinous and ligamentous structure do not appear retentive of life, but lose their animation very readily, in conse- quence of the inflammation and other circumstances which at- tend wounds. 212 YELLOW ELASTIC LIGAMENTOUS TISSUE. When thus deprived of life, they retain their usual appearance and their texture a long time. The dead parts separate from the living in large portions, in a way which has a considerable analogy with the exfoliation of bones. The tendons and their expansions, and the various fasciae, have the same chemical composition. If boiled a long time, they dissolve completely, and form the substance called by chem- ists gelatine, or pure glue. The ligaments differ from them in some respects. When boiled they yield a portion of gelatine, and do not dissolve entirely; but are said to retain their form and even their strength, after a very long boiling. The composition of the part so insoluble in water, has not yet been ascertained. Of the Yellow Elastic Ligamentous Tissue. —This is a modification of the common ligamentous tissue, which though not usually treated apart, differs from' it in many essential particulars. It contains, according to the younger Gi- rard, some fibrine in its composition; it is eminently elastic, and is placed to give resistance and support to parts, where in other animals, we meet with muscular fibres, for which it is in some sort a substitute. In some situations it is of a deep yellow co- lour, and rarely presents the silvery aspect of the common tissue. It forms the middle coat of the arteries, the ligaments between the bridges of the vertebrae, the ligamentum nucha in quadru- peds with heavy pendant heads, the elastic involucrum of the corpus cavernosum and spongiosum penis in the male, of the clitoris in the female, and the elastic covering of the spleen; we might also add, the elastic membrane of the nose and ear, which are more allied to it, than to cartilage, though they are called membraniform cartilage. Of the Fibro-cartilaginous or Ligamento-cartilaginous Tissue. —There is another variety of the desmoid tissue, which holds a middle station between ligament and cartilage, partakes partly of the nature of both, and has been treated of by Bichat as a distinct tissue under this compound name. Vesalius and Mor- FIBRO-LIGAMENTOUS TISSUE. 91 *} gagni, called them cartilaginous ligaments; Haase, mixed liga- ments. Like ligaments, they present a well marked fibrous ap- pearance, and are strong and resisting. Like cartilages, they are white, very dense and elastic. Beclard divides them into the temporary and permanent* —The temporary, are those which pass regularly and at deter- mined periods to the state of ossification, and are developed in the midst of the ligaments and tendons, as the patella and sesa- moid bones. —The permanent are of several kinds. 1. Those which are free at both these surfaces, and are lined by the synovial mem- brane. These constitute the interarticular or meniscous carti- lages, (menisci,) and are attached at their outer surface to the inner face of the capsular ligament. They are found in the knee, maxillary, clavicular, and lower ulnar articulations. 2. Those which are adherent by one of their surfaces; these are found whenever the fibrous tissue is subjected to habitual friction by the tendons, as in the different grooves, through which they play, or upon the sides of the ligaments or cartilages, against which they rub; the periosteum, or whatever fibrous membrane it may be, first becomes thickened and then converted into a semicartilage. It also exists in the fibrous rings, placed at the margin of the glenoid and cotyloid cavities for the purpose of deepening their sockets. 3. Those adherent by both surfaces. These are found between the bodies of the vertebrae and the pubic bones. —The accidental production of this tissue is by no means un- common; it is found occasionally in the cavities of fractures forming false joints, in the tubercular cavities of the lungs, in the uterus, ovaries, etc. * Bichat considered the elastic cartilaginous membranes of the nose, oar, and trachea, as belonging to this division of the tissues, but they certainly have a closer affinity to the yellow elastic fibrous tissue.—p. 214 OF ARTICULATIONS CHAPTER IV. A GENERAL ACCOUNT OF ARTICULATIONS, AND OF BURSiE MUCOSAE. Of Articulations. Those surfaces of bones which form the movable articula- tions are covered with cartilaginous matter which has been al- ready described.* —In many of the immobile articulations, as the sacro-iliac symphysis for instance, a thin lamen of cartilaginous matter, with all the other appurtenances of joints, are likewise met with. The connexion between the articular cartilage and the bones is strong, but its nature is not well known. None of the vessels of the bone pass into the cartilage, but terminate in its immediate neighbour- hood. Gerdy (page 29) considers it a secretion from these ves- sels, and that its formation is like that of the cuticle, from the vessels of the skin. It presents the appearance of a couch of white wax spread over the end of the bones, though it is com- posed of vertical fibres like the frill of velvet, so crowded toge- ther as to leave no sensible interval between them, and presenting a free extremity to the cavity of the joint. The cartilages ter- minate insensibly at their circumference on the surface of the bone. On the heads of the bones they are thicker at the central part, than at their circumference; in the corresponding socket, the cartilaginous coating is thickest at the margin, and sometimes spreads out into a sort of cartilaginous rim.— They are retained in their relative situations by ligaments, such as have been lately mentioned, which are exterior to the cavities of the articulations, and placed in such situations that they permit the motions the joints are calculated to perform, while they keep the respective bones in their proper places. * See page 35. SYNOVIAL CAPSULES. 215 Of the Synovial Capsules. —The synovial capsules are formed of an extremely thin transparent, double reflected tissue, the vessels of which circu- late in the healthy state only the serous portions of the blood, and which, though erected into a distinct tissue or system by Bi- chat, under the name of synovial, is now generally considered as forming only a part of the general serous tissue, which it closely resembles in structure, and with which it intimately sympathises in disease. They are of three kinds: 1st. Those which line the inner surface of the ligaments of the joints, and are reflected over the surfaces of the articular cartilages. These are called the articular synovial cartilages. 2d. Those which are placed be- tween the tendons of the muscles, and the bones and cartilages against which the tendons rub. These are called bursa mucosa. 3d. Those which are placed between the skin and the bones, tendons, or other hard parts, over which it performs frequent and extensive movements. These are called the subcutaneous syno- vial capsules.— Of the Articular Synovial Capsules. They are invested in a particular manner by a thin delicate membrane, which in some joints, as those of the hip and shoul- der, seems to be the internal lamina of a stronger ligament called the capsular; and, in other joints, the knee, for example, appears to be independent of any other structure. In each case, this synovial membrane, as it has lately been called, forms a complete sac or bag, which covers the articular surface of one bone, and is reflected from it to the corresponding surface of the other ; adhering firmly to each of the articulating surfaces, and extending loosely from the margin of one surface to that of the other. In the distribution it supplies the place of perichondrium to the cartilages, and of periosteum to those surfaces of bone with which it is connected. It seems greatly to resemble the membranes which line the abdomen and thorax, and invests the parts contained in these cavities; and like them it may be termed a reflected membrane. 216 BURS^E MUCOSAE. It is thin and very flexible, but dense and strong. It secretes, or effuses from its surface, a liquor, called synovia; which is particularly calculated to lubricate parts that move upon each other. The fluid is nearly transparent: it has the consistence of a thin syrup, and is very tenacious or ropy. It mixes with cold water, and, when heated, becomes milky, and deposits some pellicles without losing its viscidity. It appears to be composed of eighty parts in one hundred of water; above eleven parts of fibrous matter; and between four and five parts of albumen. It also contains a small portion of soda, of muriate of soda, and of phosphate of lime. There are in many of the joints masses of fat which appear to project into the cavity, but a^ exterior to the synovial mem- brane, and covered by it; as the viscera in the abdomen are covered by the peritoneum. They are generally situated so as to be pressed gently, but not bruised, by the motions of the bones. In some joints, they appear like portions of the common adi- pose membrane; in others, they appear more vascular, and have a number of blood-vessels spread upon them. Small processes often project from their side-like fringe. These masses have been considered as synovial glands; but they do not appear like glands; and it is probable that the syno- via is secreted by the whole internal surface of the membrane.* The synovial membrane, like the other parts of joints, is in- sensible in a sound state, but extremely painful when inflamed. The synovia, which is secreted, during the inflammation of this membrane, has a purulent appearance. Of Bursa Mucosa. There are certain membranous cavities called bursae mucosae, which are found between tendons and bones, near the joints, * Clopton Havers, ignorant that the synovia was derived by a sort of perspira- tion from the inner surface of this membrane, supposed it to be secreted by these masses of adipose matter, which are still known, in perpetuation of his mistake, as Havers'1 glands.—p. BURSjE MUCOSAE. 217 and in other places also, which have so strong a resemblance to the synovial membrane, and are so intimately connected with some of the articulations, that they ought now to be mentioned. They are formed of a thin dense membrane, and are attached to the surrounding parts by cellular substance; they contain a fluid like the synovia; and sometimes there are masses of fat, which, although exterior to them, appear to project into their cavities. There is, commonly, a thin cartilage, or tough membrane, beween them and the bone on which they are placed. They often communicate with the cavities of joints, without inducing any change in the state of the part. As they are always situated between parts that move upon each other, there is the greatest reason to believe that they are intended to lessen friction.* These bursae mucosae are very numerous, as will appear from a subsequent account of them. Several of them are very interesting on account of their con- nexion with very important joints. —These bursae form synovial sheaths to the tendons, where they run through grooves in the bones, or under their vaginal ligaments, or where they glide over each other, as in the palms of the hands and the soles of the feet: but they are especially met with, wherever a tendon changes its direction, and converts a bone, a cartilage, or ligament into a pulley; of which instances will be detailed hereafter. When a bursae, or tendinous sheath, invests a tendon about to subdivide, as the flexor tendons of the fingers at the wrist, the sheath also subdivides so as to send a process along each parting tendon; a knowledge of which fact is of importance to the surgeon, as this membrane when injured, is much disposed to continuous inflammation. —The number of these bursae vary in different individuals. Ollivier reckons them at one hundred pairs. * For farther information respecting this subject, as well as joints in general, the reader is referred to a Description of the Bursae Mucosae of the Human Body, by Alexander Monro; to whom the world is so much indebted for the elucidation of many important points in anatomy and physiology. VOL. I. 19 218 SUBCUTANEOUS SYNOVIAL CAPSULES. Subcutaneous Synovial Capsules. —These have been long observed about the wrist, ankle and knee, where they sometimes attain the size of walnuts, and are known to surgeons under the names of ganglions and hygroma. They were studied and described for the first time, however, by Beclard. They exist wherever the skin is strongly and fre- quently moved over a resisting part: as between the skin and the patella; between the olecranon and skin; over the trochanter; acromion; thyroid cartilage; at the metacarpal and metatarsal articulations, &c. &c. They are developed accidentally in dif- ferent parts, when from any cause, as in curvature of the spine, the friction of the tendons is increased. When inflated, the ca- vities appear oblong and cellulated, contain some synovial fluid, and look like dilated cells of the cellular tissue, of which they are in all probability formed; many of them, however, are visible in the foetus during the latter period of utero-gestation.— PARTICULAR ARTICULATIONS. 219 CHAPTER V. OF PARTICULAR ARTICULATIONS. The connexion of the Head with the Vertebra. The condyles of the occipital bone, and the corresponding cavities of the atlas, are covered with cartilage. The condyle and cavity on each side are invested with a synovial ligament, as described in the general account of articulations. An anterior ligament, (ligamentum occipito-atloidal anterior,) descends from the front part of the great occipital foramen, and is inserted into all the front part of the atlas, between its articu- lating processes. That portion of .this ligament which is in the middle, and inserted into the tubercle of the atlas, appears stronger, and is distinct from the rest of it. A posterior ligament, (ligamentum occipito-atloidal posterior,) passes from the posterior margin of the occipital foramen to the upper edge of the posterior arch of the atlas. From each side of the upper end of the tooth-like process of the vertebra dentata, a ligament (oblique, or moderator,) passes upwards and outwards, to be inserted into the internal side of the basis of each condyle of the occipital bone. There is a small ligament, called the middle straight ligament (ligamentum me- dium rectum,) which passes from the tip of the dentated process, to be inserted on the inner face of the occipital foramen between the insertion of the moderator ligaments. From the anterior margin of the great occipital foramen, a ligament passes down on the inside of the vertebral cavity, over the tooth-like process, which is inserted in the body of the verte- bra dentata, and the ligaments connected with it. This liga- ment is composed of a number of fibrous bands called by Cal- dani, lacerti ligamentosi. 220 ARTICULATIONS OF THE VERTEBRAE. There is also a ligament which runs across from one side of the atlas to the other, to confine the tooth-like process in its an- terior cavity, (transverse ligament, ligamentum transversale at- lantis.) This ligament adheres above to the occipital bone, and below to the body of the vertebra dentata. The anterior sur- face of the tooth-like process plays on the anterior arch of the atlas; the posterior surface plays on this ligament. A synovial capsule is placed on each surface of the tooth-like process. The articulating surfaces of the oblique process of the atlas and vertebra dentata on each side, are invested by a synovial membrane. There are, also, additional ligaments placed before and behind these processes, that have an effect on their motions. The uses of these different ligaments are very obvious when they are dis- sected. The transverse ligament of the atlas, with the synovial mem- branes, form an articulation for the tooth-like process, which is of a pecu- liar kind. The ligaments that pass from this process, to the bones of the condyles of the occipital bone, must have an effect in restraining the rota- tion of the head and atlas on this process, and therefore have been called moderator ligaments. The Articulations of the Vertebra with each other. To acquire a perfect idea of the construction of the Spine it is necessary to examine at least two preparations of it: in one of which the bodies of the vertebra? should be sawed off from the processes, so that the spinal canal may be laid open. The bodies of all the vertebrae, except the atlas, are connected to each other by the intervertebral fibrocartilaginous matter de- scribed in page 121, which unites them very firmly, at the same time that it allows of some motion, in consequence of its elasti- city and compressibility. This connexion is strengthened By two ligaments, which extend the whole length of the spine, from the second cervical vertebra to the sacrum. The first of these, denominated the anterior vertebral ligament, covers a considerable part of the anterior surface of the bodies of the vertebrae; it is thickest in the middle, and varies in its breadth in different parts of the vertebral column; it adheres very firmly to the intervertebral substance, and not so firmly to ARTICULATIONS OF THE VERTEBRAE. 221 the bodies of the vertebrae. It has the shining silver-like appear- ance of tendon, and seems to consist entirely of longitudinal fibres. There are many fibres which appear to be connected with it, that do not extend the whole length of the spine. On the posterior surface of the bodies of the vertebrae, in the cavity which contains the spinal marrow, is the posterior or in- ternal vertebral ligament, which, like the anterior, extends from the upper part of the spine to the sacrum. In its progress downwards it is broader where it is in contact with the intervertebral matter, and narrower about the middle of each of the bodies of the vertebrae. It appears to consist of longitudinal tendinous fibres, which are similar to those of the anterior ligament. The fibres of which these ligaments are composed, are more closely connected by origin and insertion with the intervertebral matter, than with the bodies of the ver- tebrae. Some of the fibres are inserted into the next vertebrae or intervertebral substance below their place of origin, others into the second or third, and some into the fourth or fifth. The oblique processes of the vertebrae are covered with car- tilage, and are invested with a synovial membrane, like the other movable articulations. In the neck and back these membranes are thin and delicate; but in the loins they are blended with liga- mentous fibres which give them additional strength. Some of the most curious and interesting ligaments of the spine, or indeed of the body, arc those which are attached to the bony plates or arches that extend from the oblique to the spi- nous processes of each vertebrae. These plates form a great portion of the posterior part of the vertebral canal and the va- cant spaces between them are filled up by these ligaments, which extend from the plates of each upper vertebra to those of the next vertebra below. They are situated between the spinal process and the oblique processes on each side. They are, therefore, two distinct ligaments between the two vertebrae, one on each side of the spinal process; and as they extend only from the plates or arches of one vertebrae to those of the other, they must necessarily be very short. They are 19* 222 ARTICULATIONS OF THE VERTEBRAE. much more conspicuous on the infernal surface of the vertebral cavity than they are externally. They are thick and substantial, and very elastic; their colour resembles that of a yellowish adeps; and from that circumstance they are called by some anatomists the yellow ligaments. They complete the cavity for the spinal marrow. There are twenty-three pairs in all. As the plates or arches to which they are conaected must re- cede from each other, when the spine is bent forwards, it seems that they should be elastic. There are also ligaments between the spinous processes, which extend from the under surface of one spinous process to the upper surface of the spinous process below it. These are com- posed of tendinous shining fibres, and are sufficiently loose to permit the anterior flexure of the vertebral column. From their situation they are denominated interspinal ligaments. There is also a thin and narrow ligamentous band, which ex- tends from the spinous process of the seventh cervical vertebras to the spinous processes of the os sacrum, and adheres to the ends of the intermediate spinous processes. It is exterior to the ten- dinous origins of the trapezii and latissimi dorisi muscles. The upper portion is slightly connected to the trapezius, the lower part adheres more firmly to the latissimus dorsi. The ligamentum nucha, ligament of Diemerbrack, as it has been denominated, is a narrow but firm strip, which extends from the spinous process of the last cervical vertebra, to the oc- cipital bone, at or near its protuberance. That portion of the trapezius muscle which is between the occipital bone and the seventh cervical vertebra, originates from it, or is intimately connected with it; and a portion of the splenius muscle is also connected with it. From the internal surface of this ligament, a thin tendinous membrane arises, whose fibres run obliquely upwards nnd for- wards, and are inserted into the spinous processes of each of the cervical vertebrae above the seventh, and also into the atlas and the os occipitis. Attached to the ligamentum nuchae and to the spine, this membrane seems like a partition between the muscles which lie on each side of the back of the neck. ARTICULATION OF THE LOWER JAW. 223 After inspecting the different ligaments of the spine, it will be obvious that the yellow ligaments are among the most important of them; in conse- quence of their position, their strength, and their elasticity. Articulation of the Lower Jaw, (Temporo-maxillary.) The glenoid cavity of the temporal bone with the tubercle be- fore it, and the condyle of the lower jaw, are covered with car- tilages. A cartilage is placed between them called interarticu- lar, which being flexible, is accommodated to the convexity of the condyle and hollowness of the glenoid cavity, and also to the figure of the aforesaid tubercle to which it is extended. A synovial capsule, or bag, invests the glenoid cavity and the tu- bercle, and covers the upper surface of the cartilage. A second capsule of the same kind is attached to the condyle of the lower jaw, and the lower surface of the cartilage. A few ligamentous fibres extend from the circumference of the cavity and tubercle of the temporal bone, over both synovial capsules and the carti- lage between them, to the lower jaw below the condyle, and ap- pear to be attached to the cartilage. These fibres are collected in such numbers, on the external and internal sides of the articulation, that they have been called the external and internal lateral ligaments. Another ligament called stylo-maxillary, is mentioned which arises from the styloid process of the temporal bone, and is in- serted into the lower jaw near its angle; but this seems rather appropriated to the stylo-glossus muscle than to this articula- tion. In consequence of this structure, the condyle of the lower jaw moves out of the glenoid cavity upon the tubercle, when the mouth is opened widely. Articulation of the Clavicle and Sternum, called Sterno-cla- vicular. The connexion of the clavicle and sternum resembles strongly that of the lower jaw and temporal bone. A movable carti- lage is placed between the articulating surfaces, with a distinct synovial capsule on each side of it, applied in the usual manner 224 ARTICULATIONS OF THE SHOULDER. to the corresponding surface of the clavicle and of the sternum. Exterior to these capsules and the intervening cartilage, are many ligamentous fibres, which are most numerous on the ante- rior and posterior surfaces, but diverge from each other as they proceed from the clavicle to the sternum, and are, therefore, called Radiated Ligaments. There is a strong ligament called the Interclavicular, which passes across the sternum internally, from one clavicle to the other. And another ligament, which arises from the inferior rough surface of the clavicle, near the sternum, which is inserted into the cartilage of the first rib. This is called the Rhomboid, or Costo-clavicular ligament. Articulations of the Clavicle and Scapula, (Scapulo-clavicular.) These are two in number; one which connects the acromion and external end of the clavicle called acromio-clavicular, and one which connects the lower surface of the outer part of the clavicle with the coracoid process of the scapula, called coraco- clavicular. Acromioclavicular. The small surfaces of the clavicle and scapula, which are in contact with each other, are furnished with the apparatus of a movable articulation. They are co- vered with cartilage, and are invested with a small synovial capsule. The upper and lower surfaces of the extremities of the clavicle and acromion are covered by a ligamentous membrane, which is called, from its situation, the superior and inferior liga- ment of this articulation. Coraco-clavicular, consisting of two portions, conoid and trape- zoid. But these bones are more firmly connected by the liga- ment which passes to the coracoid process of the scapula from the under side of the clavicle, and is very strong. Some of the fibres which compose this ligament are so arranged that they have the appearance of an inverted cone: the remaining fibres appear like another ligament, and therefore they have been called the trapezoid and conoid ligaments. —The base of the conoid ligament is upwards, and its apex ARTICULATIONS OF THE SHOULDER. £25 or origin is at the root of the coracoid process. It is the stronger of the two. The trapezoid is at the outer side of the conoid. It is broad and thin, with its fibres separated by interstices. It rises from the root of the coracoid process, and is inserted on an oblique ridge, leading from the tubercle of the clavicle to its acromial end.— By their situation and strength they are enabled to retain the bones in their proper relative positions, at the same time that they permit a peculiar rotary motion. —There is a bifid ligament called ligamentum bicorne, arising from the root of the coracoid process, at the inner side of the conoid, which runs inwards in front of the subclavius muscle, to which it serves as a fascia, and bifurcates; one horn is at- tached to the under surface of the clavicle near the rhomboid ligament, and the other to the end of the first rib, under the ten- don of the subclavius muscle.— Articulation of the Os Humeri and Scapula, (Scapulo-humeral.) The spherical portion of the upper extremity of the os humeri is the part of that bone which is principally concerned in the articulation, and is covered with cartilage; as is also the gle- noid cavity of the scapula. The glenoid cavity of the scapula, which is so small in the dried bone when compared with the head of the os humeri, is enlarged by the long tendon of the biceps muscle, which is at- tached to the upper edge of its margin, and then divides and passes down on each side of the cavity, increasing the breadth of it considerably, thus forming what is called the glenoid liga- ment, deepening the socket, and giving greater latitude of motion to the arm, from its elasticity, than if the socket had all been formed of bone. It appears to be blended with the cartilage that lines the cavity, and also with the capsular ligament which is exterior to it. The articulating surface, thus composed, is perfectly regular and uniform. The synovial ligament, in this articulation, is so blended with an external stronger ligament, that it cannot be separated in the 226 ARTICULATIONS OF THE SHOULDER. recent subject; but, notwithstanding, it is applied to the articu- lating surfaces in the same way that it is applied to the other joints forming a capsule. The stronger exterior lamina is, of course, only applied to that part of the synovial capsule which proceeds from the margin of one cartilaginous articulating sur- face to the other: it appears to be most intimately connected with the periosteum, and is rendered more firm and thick in par- ticular parts, by the addition of fibres from the tendons of the supra and infra-spinatus, and subscapularis muscles with which it is blended. It arises from the scapula at a small distance from the margin or edge of the glenoid cavity, as formed by the tendon of the biceps, and is inserted into the os humeri at a small distance from the edge of the cartilaginous articulating surface; and, if dissected away from the bones, would appear like a cylindrical bag with both extremities open.—The capsular ligament is thick- ened in front by a band of fibres, arising from the outer part of the back surface of the coracoid process, which proceeds beneath the triangular ligament to the upper part of the os humeri; it is closely blended with, and forms a part of the capsular ligament, and is denominated the coraco-humeral ligament, or ligamentum adscititium.— The long tendon of the biceps muscle, in the groove at the head of the os humeri, appears to penetrate this ligament; but it is not within the cavity of the synovial membrane; for this membrane sends down a process like the finger of a glove, which lines the groove, and is reflected from its surface upon the sur- face of the tendon, and covers it during its whole extent, being reflected from the tendon, at its upper termination, to the adjoin- ing surface; so that the tendon is in fact outside of the synovial capsule, which, therefore, confines the synovia completely. This capsular ligament, which is one of the strongest, would not avail much in keeping the bones in their proper situations, if the muscles and their tendons were not disposed in such a man- ner, that when the muscles act, their power is excited to the same effect. In some cases of paralytic affection, where the muscles exert no influence, the weight of the arm, when it is allowed to ARTICULATION OF THE ELBOW. 227 hang without support, draws the head of the os humeri, below the glenoid cavity, notwithstanding the capsular ligament. At the same time it ought to be observed, that this ligament must be lacerated in every case of complete luxation of the os humeri; as it cannot possibly distend sufficiently to permit the separation of the bones to the extent which then takes place. The Articulation of the Elbow. Those surfaces of the os humeri, ulna, and radius, which move upon each other, are covered with cartilage. The motion of the ulna and radius on the os humeri is that of the simple flexion and extension. The cylindrical head of the radius performs a part of a revolution, nearly on its own axis, without moving from the depression in the side of the ulna, with which it is in contact. The synovial membrane adheres very firmly to the surface covered with cartilage on each of the bones, and is reflected from the margin of this surface, on one bone, to that of the others. As the principal motion performed is hinge-like, the principal ligaments are on the sides. There is also a circular ligament, which arises from the ulna and invests the narrow part of the radius immediately below its cylindrical head like a loop, to confine the radius in contact with the ulna, and at the same time permit its motion. This ligament is so blended with the synovial membrane, that it sometimes cannot be separated from it. The lateral ligaments are denominated from their origin and insertion, Brachio-radial, and Brachio-cubital, or Internal and External. The ligament which invests the neck of the radius is called Coronary or Orbicular. There are also some ligamentous bands, which run upon the front and back parts of the joint to strengthen it, which are called Anterior and Posterior accessory ligaments. Within the syno- vial membrane, in the upper margins of the depressions for the olecranon and coronoid processes of the ulna, are the adipose substances usually found in joints. 228 ARTICULATION OF THE WRIST. Articulation of the Wrist. The structure of the wrist is particularly complex, because it consists of three articulations, which are contiguous to each other, viz. That of the ulna and radius; of the radius and first row of carpal bones; and of the first and second row of carpal bones with each other. An oblong convex head is formed by the upper surfaces of the scaphoides and lunare, and a portion of the upper surface of the cuneiforme bone. This head is covered by one cartilage, which is so uniform that the different bones cannot be distin- guished from each other. The lower end of the radius is arti- culated with this head, but does not cover the whole of it; a portion of this head, therefore, is under the ulna, but not in con- tact with that bone: for the cartilage which lines the concavity of the radius, is continued beyond the radius, so as to cover the remainder of the head, formed by the carpal bones. The lower end of the ulna is in contact with the upper surface of this car- tilage, and is articulated laterally with the semilunar cavity of the radius. This semilunar cavity is lined by a cartilaginous process, continued from the upper surface of the aforesaid car- tilage ; so that the extremity and the side of the ulna play upon the cartilage continued from the radius. This articulation of the ulna and radius is distinct from that of the radius and carpus. A synovial membrane covers the articulating head formed by the three bones of the carpus, and is reflected from the margin of their cartilaginous surface, to the cartilage at the end of the radius. A plait or fold of this membrane passes from the head of the carpus, at the junction of the scaphoides and lunare, to the opposite part of the cartilage of the radius, and has been called the Mucous Ligament, (ligamentum mucosum.) A strong ligament (internal lateral) is placed on the internal side of this articulation, which arises from the styloid process of the ulna, and is inserted into the anterior transverse ligament which confines the flexor tendons, and into the ligament of the os pisiforme. Another ligament, (external lateral,) on the external side, arises from the styloid process of the radius, and is inserted into the ARTICULATION OF THE WRIST. 229 scaphoides, some of its fibres being continued into the aforesaid transverse ligament, and the trapezium. There are two broad irregular ligamentous membranes: one of which arises from the anterior margin of the articulating sur- face of the radius ; and the other from the posterior margin. One of them is inserted anteriorly, and the other posteriorly, into the margin of the corresponding surface of the scaphoides, lunare and cuneiforme. They adhere to the synovial membrane; but in some places this membrane appears through apertures which are in them. The surfaces, by which the first and second rows of carpal bones are articulated with each other, are very irregular. The magnum and part of the unciforme form a prominent oblong head ; on each side of which is a much lower surface, formed by the trapezium and trapezoides externally, and the remaining portion of the unciforme internally.* The scaphoides, lunare, and cuneiforme, form a cavity which corresponds with this head, and also with the lower surface formed by the unciforme; while another surface of the sca- phoides is articulated with the trapezium and trapezoides. These corresponding surfaces, formed by the two rows of carpal bones, irregular as they are, compose but one articulation, which is ca- pable of a limited flexion and extension. It has a synovial mem- brane, with two lateral ligaments, and an anterior and posterior ligament; these last, however, are short, and can be best exa- mined from within, by cutting open the articulation. The bones of each row move laterally upon each other. Their lateral surfaces, which are in contact, are covered with carti- lage; and the synovial sac which exists between the first and second row of bones, sends off processes between these surfaces, which are disposed like the ordinary synovial membranes in other articulations; adhering to each of the cartilaginous sur- faces, while they communicate with the larger cavity between the two rows. * The palm of the hand is supposed to present forward. vol. i. 20 230 ARTICULATION OF THE CARPAL BONES, &c. Articulation of the Carpal and Metacarpal Bones. The metacarpal bones are connected to the last row of the carpus by surfaces which are covered with cartilages, and sup- plied with synovial membranes, as the most movable articula- tions are; but the ligaments which connect these bones do not permit much motion between them. The ligaments are all dor- sal and palmar. The irregularity of the articulating surfaces of the metacarpal bones of the index and middle finger also con- tribute to restrain their motion; and these bones accordingly move less than the other two metacarpal bones, whose surfaces are better adapted for motion. Articulation of the Fingers. The first joint of the fingers has a large synovial membrane, which invests the head of the metacarpal bone and the corre- sponding cavities of the bones of the first phalanx. On each side is a strong lateral ligament, which arises from the side of the head of the metacarpal bone, and is inserted into the side of the base of the first phalanx. Anteriorly there is also a ligament, which, although thick and strong, is very flexible. It is thickened by cartilaginous matter on its palmar face, which serves as a sort of pully to the ten- dons, and increases their power by removing them from their line of action. Posteriorly the expansion of the tendons of the ex- tensor muscle, and the tendons of the interossei, have the effect of a ligament. The different phalanges are articulated with each other in a similar manner. The lateral ligaments are very strong: the tendon of the extensor covers the articulation posteriorly; and anteriorly, under the flexor tendons, there is a soft, but thick ligamentous substance. The metacarpal bone of the thumb dif- fers greatly from the other metacarpal bones in its articulation with the wrist, as respects its motions. The articulating sur- faces are calculated for lateral motion as well as flexion and ex- tension ; and there are no ligaments which prevent it. Its cap- sular ligament forms a complete sac. The first joint of the ARTICULATION OF THE RIBS. 231 thumb resembles considerably that of the fingers; and the se- cond joint resembles the last of the phalanges. Articulation of the Ribs. The ribs are connected to the bodies of the vertebrae and the intervertebral cartilages, by one articulation, and to the trans- verse processes of the vertebrae by another: these articulations have the ordinary apparatus for motion, with capsular ligaments, which in one case pass from the heads of the ribs to the bodies of the vertebrae, and in the other from the tubercles to the trans- verse processes. These form what are called the costo-vertebral, and coslo-transverse articulations. —The capsular ligament of the costo-vertebral articulation, is not complete. It is much thickest in front and upon the sides, and radiates from its origin on the head of the ribs, whence it is usually called the anterior or radiating ligament. —There is also a small inter-articulating ligament, in this articu- lation, which passes from a ridge on the head of the rib to a cor- responding line on the intervertebral substance. It thus divides the joint into two halves, each of which has a separate synovial membrane. This ligament does not exist where the ribs are at- tached to a single vertebrae, as the first, eleventh and twelfth. —The costo-transverse articulation, besides its feeble capsular ligament and synovial membrane connecting the tubercle of the rib with the facet of the transverse process, includes three other ligaments, the internal transverse, the external transverse, and the middle costo-transverse. —The internal transverse, arises from the inferior margin of the transverse process, and is inserted into the upper margin of the neck of the rib below. —The external transverse, arises from the extremity of the transverse process and is inserted into the corresponding rib, just beyond the tubercle. —The middle costo-transverse ligament is extended between the neck of the rib and the contiguous transverse process. To be well seen it is necessary to saw longitudinally through the neck of the rib and its transverse process.— 232 HIP JOINT. These ligaments permit the motions necessary for respiration, and restrain all others. The connexion of the ribs anteriorly with their cartilages, is such as admits of no motion whatever between them; but the extremities of the cartilages are articulated with the sternum, at the pits on the edges of that bone. In many instances there is no appearance of synovia between the ends of the cartilages and the sternum; but this fluid is mostly to be found in the pits, on the lower extremity of the sternum. —In the articulations between the cartilages of the ribs and the sternum, there is a synovial membrane, and two ligaments, anterior and posterior. These radiate from the sternal end of the cartilage, one over the anterior, the other over the posterior face of the sternum, and are blended with its periosteum.— The Hip Joint. The acetabulum is lined with cartilage; and the brim or mar- gin of it is much enlarged, and the cavity deepened, by the addition of fibro-cartilaginous matter, which forms a regular smooth edge. This cartilaginous ring is continued across the upper part of the notch in the acetabulum ; so that it completes the circular margin of the cavity, but leaves the under part of the notch open. This forms what is called the cotyloid liga- ment. The head of the os femoris is covered with cartilage, but the depression in it is still visible. From this depression a strong round ligament (ligamentum teres or rotundum) arises, which appears to pass into the depression, near the centre of the ace- tabulum ; but actually terminates in the lower edge of the car- tilaginous ring or margin, where it crosses over the notch, and not in the bone. This ligament is in fact divided into two parts at its insertion; one passes out at the inferior part of the coty- loid notch and is inserted on the margin of the ischium ; the other runs to the superior end of the notch, and besides being blended with the cotyloid ligament, is attached to the margin of the acetabulum. The thin (synovial) membrane with which this ligament is invested extends to the centre of the acetabulum, and KNEE JOINT. 033 has given rise to the opinion that the ligament was inserted in the bottom of the acetabulum.* This ligament allows the head of the os femoris to rise out of the acetabulum, but it is probably torn in every luxation of the os femoris. The capsular ligament, which contains these articulating parts, is the strongest in the body. It arises around the acetabulum, near the basis of the cartilaginous brim, but it does not ad- here to the cartilaginous edge; and it is inserted into the os femoris, near the roots of the trochanters, so that it includes a large portion of the neck of the bone. It is not every where of the same thickness and strength ; for, in various places, there are additional ligamentous fibres. The largest portion of these additional fibres appears to arise from the inferior anterior spinous process of the ilium. It is thinnest at its internal and posterior part. The synovial membrane forms the internal lamina of this liga- ment : it invests the articulating surfaces in the usual manner, and being reflected from the internal surface of the capsular ligament to the neck of the os femoris, it is in the place of peri- osteum to that part of the bone'. It seems probable that this membrane is so reflected and ar- ranged, that the internal ligament is covered by it also, and, of course, that this ligament is exterior to the synovial membrane. There is a considerable quantity of adipose matter near the ter- mination of the aforesaid internal ligament, which is also exterior to the synovial membrane: some of this can be pressed out of the acetabulum, at the vacuity in the notch under the cartilagi- nous margin. Articulation of the Knee. The synovial membrane of the knee joint is, in some places, without the support of a proper capsular ligament, or external lamen, so that it is easier distinguished in this articulation than in many others. It adheres firmly to the cartilaginous surfaces of the os femo- * See motions of skeleton. 20 * 234 KNEE JOINT. ris, tibia, and patella, and is reflected in the usual manner from one to the other of these surfaces. It arises closely from the edge of the cartilaginous surface at the top of the tibia; but on the anterior part of the os femoris, it is continued to some dis- tance from the margin of the pulley-like surface, and the edges of the condyles. On each of the portions of the cartilaginous surfaces of the tibia is a cartilage of a semilunar form, so placed, that its convex edge rests on the margin of the cartilaginous surface, and its concave edge is internal. These cartilages are thick at their external, and very thin at their internal edges; so that they form two superficial concavities on the top of the tibia. Their extremities are attached by ligaments to the central protuberance of the tibia, and their anterior extremities are also connected by a ligament to each other. The synovial membrane is so reflected as to cover the whole surface of these cartilages, except the exterior edge, which is connected with the external ligaments of the articulation. The use of these cartilages, is evidently to form concavities on the top of the tibia, for accommodating the condyles of the os femoris; and upon examination, they will not appear so ano- malous as they are at first view, for there is a considerable ana- logy between them and the cartilaginous edges of the glenoid cavity and of the acetabulum. These are called the semi-lunar cartilages. The internal is but little more than a semicircle; the external is nearly circular in its shape. The patella appears to project into the cavity of the joint, and its internal surface is very prominent; around the margin of this surface, and especially at the under part of it, the adipose sub- stance found in joints is very abundant. On each side of the adi- pose mass, under the patella, is a plait of the synovial membrane, called ligamentum alare minus, and majus; and a process of the membrane, called ligamentum mucosum, passes from the neigh- bourhood of the adipose mass to the os femoris between the condyles. These processes retain the adipose substance in its proper place, during the motions of the joint. There are two very strong ligaments, called the anterior and KNEE JOINT 235 posterior crucial, which arise from the middle protuberance of the tibia, one of which is inserted posteriorly into the corner face of the external condyle of the os femoris, and the other, into the outer face of the internal. These ligaments decussate each other partially, on which account the name crucial is applied to them. They are in a state of tension w7hen the leg is extended, and prevent it from moving farther forward : when it is bended they are relaxed. They add greatly to the strength of the con- nexion between the os femoris and tibia. These ligaments are generally supposed to be in the cavity of the joint; but the synovial membrane is reflected round them in such a manner that they are exterior to it. In addition to the crucial ligaments, this articulation has the following external supports. When the leg is extended, these ligaments are tense, they therefore prevent rotation in the extended state: when the leg is bent, they are relaxed, and, therefore, admit of that motion. 1. Two strong lateral ligaments, one on each side of the knee; the external of which arises from the tubercle above the exter- nal condyle of the os femoris, and is attached to the fibula a lit- tle below its head; and the internal, from the upper part and tu- bercle of the internal condyle, and is inserted into the upper and inner part of the tibia. 2. The posterior ligament, or ligament of Winslow, whose fibres run obliquely from the external condyle, to the back part of the internal side of the head of the tibia. This ligament also prevents the leg from being drawn too far forwards. 3. The connexion of the tendons of the extensor muscles of the leg, with this articulation, has a great effect upon it. Their insertion into the patella places them in the situation of the up- per part of the anterior ligament, of which the very strong liga- ment, that passes from the lower margin of the patella to the tubercle of the tibia, is only the lower portion; while the patella may be considered as an inducted part of the ligament. The tendons of the ham-string muscles, also, serve to strengthen the articulation on the back and sides. —The fascia lata of the thigh as it passes down upon the leg, 236 ARTICULATION OF THE TIBIA AND FIBULA. is thickened by a process of the extensor tendons, and forms a strong external investment or involucrum to the knee joint. It constitutes in fact a sort of capsular ligament to the joint; it closely embraces the patella and its ligaments, covers in and is partly blended with the lateral ligaments, and is firmly attached to the condyles. At the posterior part of the joint, it forms a thin membrane, and can scarcely be traced. Its place is there supplied by the posterior ligament. On either side of the liga- ment of the patella its inner face is in contact with the synovia] membrane of the joint.— Articulation of the Tibia and Fibula. The surfaces of the upper extremities of the tibia and fibula, which are articulated with each other, are very small. When the bones are in their natural position, these surfaces are nearly horizontal, that of the tibia looking down, and that of the 'fibula looking up: they are covered with cartilages, and have a syno- vial membrane. This articulation is supported by some liga- mentous fibres, which have been called anterior and posterior liga- ments ; but it is strengthened by the external lateral ligament of the knee, and by the tendon of the biceps muscle which is inserted into the upper end of the fibula. At their lower extremities, the cartilaginous crust, which, on each of them, forms part of the articulating surface with the as- tragalus, is turned up on their lateral surfaces, which are in con- tact with each other; so that a small portion (equal in breadth only to one-sixth of an inch) of the contiguous surfaces, is co- vered with cartilage; the other parts of these surfaces which are very considerable, are attached to each other by the inter- vention of fibrous or membranous matter, and there is very little motion of the bones on each other. There are very strong external ligaments, anteriorly and pos- teriorly, which connect the fibula to the tibia ; and from the pos- terior end of the fibula a small short ligament passes to the near- est part of the tibia, which resembles the margins of the glenoid cavity and acetabulum; for it enlarges the articulation with the astragalus, while it serves as a ligament to the tibia and fibula. ANKLE JOINT. 237 Articulation of the Leg and Foot. It should be observed that the tibia and fibula are so firmly connected with each other below, that they may be considered as forming but one member of this articulation. The varied surfaces formed by the tibia and fibula, and by the astragalus, when it is contiguous to them, are invested with the usual apparatus of articulation. The synovial fluid is generally observed to be very redundant in this joint. A lateral ligament (internal) passes downwards from the tibia at the internal malleolus, and is inserted into the inside of the astragalus, and also into the os calcis and naviculare. Some of the fibres are blended with those of the sheath for the tendon of the flexor communis; and some of them have a radiated arrange- ment, in consequence of which this has been called the deltoid ligament. From the fibula three ligaments arise, spoken of collectively as one ligament, external lateral, (ligamentum triquetrum.) The middle ligament, which is strong and thick, passes downwards from the end of that bone, to be inserted into the outside of the os calcis. The anterior and posterior ligaments pass also from the exter- nal malleolus, and are inserted into the anterior and posterior portions of the astragalus. Articulation of the Astragalus and Os Calcis. The astragalus is attached firmly to the os calcis by very strong and short ligamentous fibres, which arise from the fossa on its under surface, and are inserted into the fossa between the upper articulating surfaces of the os calcis. This is called the interosseous. This ligament separates the posterior articulations of the astragalus and os calcis from the anterior. The posterior articulation has a synovial membrane exclusively appropriated to it. The anterior articulation is supplied by an extension of the membrane which invests the articulating surfaces of the as- tragalus and naviculare. The connexion of the astragalus, with the os calcis is sup- 238 ARTICULATION OF THE TARSAL BONES. ported by the lateral ligaments of the ankle joint, and also by many irregular ligamentous fibres. Articulation of the Astragalus with the Os Naviculare. This articulation appears calculated for considerable motion as well from the form of the two surfaces concerned in it, as the perfect state of their articulating investments. Their motions are restrained to a certain degree, by ligaments, which are situ- ated on the upper and internal surfaces of the fool. —On the upper surface of the foot, is a thin broad ligament formed of parallel and oblique fibres, stretched from the upper and inner face of the astragalus to the upper surface of the sca- phoides or naviculare; some of the fibres extend even to the cuneiforme bones. —On the under surface of the foot, these bones are connected by two ligaments, calcaneo-scaphoid internum, and externum. —The internal arises from the inner margin of the lesser apo- physis of the os calcis, and runs obliquely forwards and inwards, to be inserted on the inner and under surface of the os navicu- lare. It is a strong ligament, and contributes much to the pre- servation of the arched form of the foot. On its under surface is a trochlea for the tendons of the flexor pollicis and flexor longus digitorum. Below it is also in contact with the tendon of the tibialus posticis, and above with the head of the astragalus, which it in part supports. —The external is at the outer side of the last; it arises from the under surface of the greater apophysis of the os calcis, and is inserted upon the under internal surface of the os naviculare.— The ligaments which pass from the anterior internal extremity of the os calcis to the os naviculare, and support the head of the astragalus, ought to be observed with attention during the examination of this joint. Articulation of the Os Calcis and Cuboides. The articulating surfaces of this joint are arranged in the usual manner. There are two additional ligaments: one placed on the upper, and the other on the under surfaces of the bones. The upper ARTICULATION OF THE OS CALCIS AND CUBOIDES. 239 ligament is thin; but the under ligament is one of the strongest of the foot; and its fibres are blended with those which form the sheath for the tendon of the peroneus longus, as it passes along the groove in the cuboides. —These, ligaments are called the superior and inferior calca- neocuboid. —The superior passes from the upper anterior surface of the os calcis to the adjoining surface of the os cuboides. —The inferior is the strongest ligament of the foot. It arises from the inferior back part of the os calcis, and is inserted upon the oblique ridge which traverses the under part of the os cu- boides. A great part of the fibres of this ligament, pass beyond the ridge and are inserted in fasciculi upon the basis of the third and fourth metatarsal bones. These subtend the groove, in which passes the tendon of the peroneus longus muscle. —The other bones of the foot are united in general by dorsal and plantar ligaments like the corresponding bones of the hand.— 240 PARTICULAR LIGAMENTS CHAPTER VI. OF PARTICULAR LIGAMENTS, AND OF THE SITUATION OF THE INDIVIDUAL BURSAE MUCOSAE. Enumeration of the most important Ligaments, which have not been described. Ligaments proper to the Scapula. The triangular ligament (ligamentum coraco-acromialis) arises broad from the external surface of the coracoid process, and be- comes narrower where it is fixed to the posterior margin of the acromion. It confines the tendon of the supra-spinatus muscle, and assists in protecting the upper and inner part of the joint of the humerus. The posterior ligament of the scapula (coracoid) is sometimes double, and is stretched across the semilunar notch of the scapula, forming that notch into one or two holes for the pas- sage of the superior posterior scapulary vessels and nerves. It also gives rise to part of the omo-hyoideus muscle. The Interosseous Ligament of the Forearm, Extends between the sharp ridges of the radius and ulna, fill- ing up the greater part of the space between these two bones, and is composed of small fasciculi, or fibrous slips, which run obliquely downwards and inwards. Two or three of these, however, go in the opposite direction, and one of them, termed oblique ligament and chorda transversalis cubiti, is stretched be- tween the tubercle of the ulna and under part of the tubercle of the radius. In different parts of the ligament there are perfora- tions for the passage of blood-vessels from the fore to the back part of the bone, and a large opening is found at the upper part LIGAMENTS OF THE HAND. 241 of it which is filled up by muscles. It prevents the radius frorn rolling too much outwards, and furnishes a commodious attach- ment for muscles. Ligaments retaining the 7'endons of the Muscles of the Hand and Fingers in their proper positions. The anterior annular ligament of the wrist is stretched across from the projecting points of the pisiform and unciform bones, to the os scaphoides and trapezium, and forms an arch which covers and preserves in their places the tendons of the flexor muscles of the fingers. The vaginal ligaments of the flexor tendons are five mem- branes, connecting the tendons of the sublimis, first to each other, and then to those of the profundis; forming, at the same time, bursae mucosae which surround the tendons. The vaginal or crucial ligaments of the phalanges arise from the ridges on the concave side of the phalanges, and run over the tendons of the flexor muscles of the fingers. Upon the body of the phalanges, they are thick and strong, to bind down the tendons, but over the joints they are thin, and have, in some parts, a crucial appearance, to allow the ready motion of the joints. The accessary ligaments of the flexor tendons of the fingers are small tendinous fraena, arising from the first and second phalanges of the fingers. They run obliquely forwards within the vaginal ligaments, terminate in the tendons of the two flexor muscles of the fingers, and assist in keeping them in their places. The posterior annular ligament of the wrist is part of the aponeurosis of the forearm, extending across the back of the wrist, frorn the extremity of the ulna and os pisiforme to the extremity of the radius. It is connected with the small annular ligaments which tie down the tendons of the extensores ossis metacarpi et primi internodii pollicis, and the extensor carpi ulnaris. The vaginal ligaments a Jhere to the last mentioned, and serve as sheaths and bursae mucosae to the extensor tendons of the hand and fingers. vol. i. 21 242 LIGAMENTS OF THE STERNUM. The transverse ligaments, of the extensor tendons, are apo- neurotic slips running between the tendons, near the heads of the metacarpal bones, and retaining them in their places. Ligaments on the Anterior part of the Thorax. The membrane proper to the sternum is a firm expansion, com- posed of tendinous fibres running in different directions, and covering the anterior and posterior surfaces of the bone, being confounded with the periosteum. The ligaments of the cartilago ensiformis are part of the pro- per membrane of the sternum, divided into strong bands, which run obliquely from the under and forepart of the second bone of the sternum, and from the cartilages of the seventh pair of ribs, to be fixed to the cartilago ensiformis. The ligaments covering the sternum serve considerably to strengthen that bone. There are also thin tendinous expansions which run over the intercostal muscles at the fore part of the thorax, and connect the cartilages of the ribs to each other. Ligaments of the Bones of the Pelvis. The two transverse ligaments of the Pelvis (ilio-lumbar) arise from the posterior part of the spine of the os ilium, and run transversely. The superior is fixed to the transverse process of the last vertebra of the loins; the inferior to the first transverse process of the os sacrum. The sacro-spinous ligaments (Jig. sacro-spinosum) arise from the posterior superior spinous process of the os ilium, descend obliquely, and are fixed to the first, third, and fourth spurious transverse processes of the os sacrum. These with the two transverse ligaments, assist in binding the bones together, to which they are connected. The two sacro-ischiatic ligaments are situated in the under and back part of the pelvis. They arise in common from the trans- verse processes of the os sacrum, and likewise from the under and lateral part of that bone, and from the upper part of the os coccygis. The first, called the large external or posterior, de- scends obliquely, to be fixed to the tuberosity of the os ischium. LIGAMENTS OF THE PELVIS. 243 The other, called the small, internal or anterior, runs trans- versely to be fixed to the spinous process of the os ischium. These two ligaments assist in binding the bones of the pelvis, in supporting its contents, and in giving origin to part of its muscles. There are two membranous productions which are connected with the large sacro-ischiatic ligament, termed its superior and inferior appendices. The superior appendix, which is tendinous, arises from the back part of the os ilium, and is fixed along the outer edge of the ligament, which it increases in breadth. The inferior or falciform appendix, situated within the cavity of the pelvis, the back part of which is connected with the middle of the large external ligament, and the rest of it is extended round the curvature of the os ischium. These two productions assist the large sacro-ischiatic ligament in furnishing a more commodious situation for, and insertion of, part of the gluteus maximus, and obturator internus muscles. Besides the sacro-spinous, and sacro-ischiatic ligaments, several other slips are observed upon the back of the os sacrum, which descend in an irregular manner, and strengthen the connexion between that bone and the os ilium. This constitutes the sacro- iliac ligament. It is also found on the anterior face of the joint, but there it is much thinner and weaker. The large holes upon the back part of the os sacrum are also surrounded with various ligamentous expansions, projecting from one tubercle to another, and giving origin to muscular fibres, and protection to small vessels and nerves which creep under them. A general covering is sent down from the ligaments of the os sacrum, which spreads over and connects the different pieces of the os coccygis together, allowing considerable motion, as al- ready mentioned, in the description of this bone. This forms what is called the anterior and posterior coccygeal ligaments. The posterior longitudinal ligaments of the os coccygis descend from those upon the dorsum of the os sacrum, to be fixed to the back part of the os coccygis. The ligaments of this bone pre- vent it from being pulled too much forwards by the action of the 244 LIGAMENTS OF THE FOOT. coccygeus muscle, and they restore the bone to its natural situa- tion, after the muscle has ceased to act. The ligamentous cartilage, which unites the two ossa pubis so firmly together as to admit of no motion, excepting in the state of pregnancy, when it is frequently found to be so much softened as to yield a little in the time of delivery. —There are a few transverse ligamentous fibres on the front part of the symphysis pubis, called the anterior pubic ligament. —The sub, or interpubic ligament occupies the summit of the arch of the pubis. It is about half an inch in breadth, and passes from the crus of the pubis of one side to that of the other.— The obturator membrane, or ligament of the foramen thy- roideum, adheres to the margin of the foramen thyroideum, and fills the whole of that opening, excepting the oblique notch at its upper part for the passage of the obturator vessels and nerve. It assists in supporting the contents of the pelvis, and in giving origin to the obturator muscles. The interosseous ligament of the leg fills the space between the tibia and fibula like the interosseous ligament of the forearm, and is of a similar structure; being formed of the oblique fibres, and perforated in various places for the passage of vessels and nerves. At the upper part of it there is a large opening, where the muscles of the opposite sides are in contact; and where vessels and nerves pass to the fore part of the leg. It serves chiefly for the origin of part of the muscles which belong to the foot. Ligaments retaining the Tendons of the Muscles of the Foot and Toes in their proper position. The annular ligament of the tarsus is a thickened part of the aponeurosis of the leg, splitting into superior and inferior por- tions, which bind down the tendons of the extensors of the toes upon the forepart of the ankle. The vaginal ligament of the tendons of the peronei muscles, behind the ankle is common to both, but divides at the outer BURSAE MUCOSAE. 245 part of the foot, and becomes proper to each. They preserve the tendons in their places, and are the bursae of these tendons. The laciniated ligament arises from the inner ankle, and spreads in a radiated manner, to be fixed partly in the cellular substance and fat, and partly to the os calcis, at the inner side of the heel. It encloses the tibialis posticus and flexor digitorum longus. The vaginal ligament of the tendon of the extensor proprius pollicis runs in a crucial direction. The vaginal ligament of the tendon of the flexor longus pollicis surrounds this tendon in the hollow of the os calcis. The vaginal and crucial ligaments of the tendons of the flexors of the toes inclose these tendons on the surfaces of the phalanges, and form their bursae mucosae. The accessary ligaments of the flexor tendons of the toes, as in the fingers, arise from the phalanges, and are included in the sheaths of the tendons in which they terminate. The transverse ligaments of the extensor tendons run between them, and preserve them in their places behind the roots of their toes. Enumeration of the most important Bursae Mucosa?. Those about the articulation of the Shoulder are situated, 1. Under the clavicle, where it plays upon the coracoid pro- cess. 2. Between the triangular ligament of the scapula and the capsular ligament of the humerus. 3. Between the point of the coracoid process and capsular ligament of the humerus. 4. Between the tendon of the subscapularis muscle and capsular ligament of the humerus, frequently communicating with the cavity of that joint. 5. Between the origin of the coraco-brachialis and short head of the biceps muscles, and capsular ligament of the humerus. 6. Between the tendon of the teres major and the os humeri, and upper part of the tendon of the latissimus dorsi. 21 * 246 BURSjE mucosae of the UPPER EXTREMITY. 7. Between the tendon of the latissimus dorsi and os humeri. 8. Between the tendon of the long head of the biceps flexor cubiti and the humerus. The bursas marked 3 and 5 are sometimes absent. Near the articulation of the Elbow there are, 1. With a peloton of fat, between the tendon of the biceps and tubercle of the radius. 2. Between the tendon common to the extensor carpi radialis brevior, extensor digitorum communis, and round head of the radius. 3. A small bursa, between the tendon of the triceps extensor cubiti and olecranon. On the Forearm and Hand are situated, 1. A very large bursa surrounding the tendon of the flexor pollicis longus. 2. Four long bursae lining the sheaths which enclose the tendons of the flexors upon the fingers. 3. Four short bursae on the forepart of the tendons of the flexor digitorum sublimis in the palm of the hand. 4. A large bursa between the tendons of the flexor pollicis longus, the forepart of the radius, and capsular ligament of the os trapezium. 5. A large bursa between the tendons of the flexor digitorum profundis, and the forepart of the end of the radius, and capsular ligament of the wrist. These two iast mentioned bursa? are sometimes found to communicate with each other. 7. A bursa between the tendon of the flexor carpi radialis and os trapezium, 8. Between the tendon of the flexor carpi ulnaris and os pisi- forme. 9. Between the tendon of the extensor ossis metacarpi pollicis and radius. BURS.E MUCOSAE OF THE THIGH. 247 10. A large bursa common to the extensores carpi radialis, where they cross behind the extensor ossis metacarpi pollicis. 11. Another common to the extensores carpi radialis, where they cross behind the extensor secundi internodii pollicis. 12. A third, at the insertion of the tendon of the extensor carpi radialis brevior. 13. A bursa for the tendon of the extensor secundi internodii pollicis, which communicates with the second bursa common to the extensores carpi radiales. 14. Another bursa between the tendon of the extensor secundi internodii pollicis and metacarpal bone of the thumb. 15. A bursa between the tendons of the extensor of the fore, middle, and ring fingers, and ligament of the wrist. 16. For the tendons of the extensor of the little finger. 17. Between the tendon of the extensor carpi ulnaris and liga- ment of the wrist. Upon the Pelvis and upper part of the Thigh there are, 1. A very large bursa between the iliacus internus psoas mag- nus muscle, and capsular ligament of the thigh bone. 2. One between the tendon of the pectinalis muscle of the thigh bone. 3. Between the gluteus medius and trochanter major, and before the insertion of the tendon of the pyriformis. 4. Between the tendon of the gluteus minimis and trochanter major. 5. Between the gluteus maximus and vastus externus. 6. Between the gluteus medius and pyriformis. 7. Between the obturator internus and os ischium. 8. An oblong bursa continued a considerable way between the obturator internus, gemini, and capsular ligament of the thigh bone. 9. A small bursa at the head of the semimembranosus and biceps flexor cruris. 10. Between the origin of the semitendinosus and that of the two former muscles. 248 BURSAE MUCOSAE OF THE KNEE AND ANKLE. 11. A large bursa between the tendon of the gluteus maximus and root of the trochanter major. 12. Two small bursae between the tendon of the gluteus maximus and thigh bone. About the Joint of the Knee are, 1. A large bursa behind the tendon of the extensors of the leg, frequently found to communicate with the cavity of the knee joint. 2. Behind the ligament which joins the patella to the tibia, in the upper part of the cavity of which a fatty substance projects. 3. Between the tendons of the sartorius, gracilis, semitendi- nosus, and tibia. 4. Between the tendons of the semimembranosus and gemellus, and ligament of the knee. This bursa contains a small one within it, from which a passage leads into the cavity of the joint of the knee. 5. Between the tendon of the semimembranosus and the lateral internal ligament of the knee, from which also there is a passage leading into the joint of the knee. 6. Under the popliteus muscle, likewise communicating with the cavity of the knee joint. About the Ankle there are, 1. A bursa between the tendon of the tibialis anticus, and under part of the tibia and ligament of the ankle. 2. Between the tendon of the extensor proprius pollicis pedis, and the tibia and capsular ligament of the ankle. 3. Between the tendons of the extensor digitorum longus, and ligament of the ankle. 4. Common to the tendons of the peronei muscles. 5. Proper to the tendon of the peroneus brevis. 6. Between the tendon achillis and os calcis, into the cavity of which a peloton or mass of fat projects. 7. Between the os calcis and flexor pollicis longus. 8. Between the flexor digitorum longus and the tibia and os calcis. BURSjE MUCOS/E of the foot. 249 9. A bursa between the tendon of the tibialis posticus and the tibia and astragalus. On the Sole of the Foot are also, 1. A second bursa for the tendon of the peroneus longus, with an oblong peloton of fat within it. 2. One common to the tendon of the flexor pollicis longus, and that of the flexor digitorum profundus, at the upper end of which a fatty substance projects. 3. Another for the tendon of the tibialis posticus. 4. Several for the tendons of the flexors of the toes. - < \*'•>?■■■ lift &:.*. 251 ANATOMICAL PLATES. EXPLANATION OF THE PLATES OF OSTEOLOGY. Plate V. Fig. 1. A Posterior View of the Sternum and Clavicles, with the liga- ment connecting the clavicles to each other. a, The posterior surface of the sternum, b b, The broken end of the cla- vicle, cccc, The tubercles near the extremity of each clavicle, d, The ligament connecting the clavicles. Fig. 2. A Fore View of the Left Scapula, and a half of the Clavicle, with their Ligaments. a, The spine of the scapula, b, The acromion, c, The inferior angle. d, Inferior costa. e, Cervix, f, Glenoid cavity, covered with cartilages for the arm bone, g g, The capsular ligament of the joint, h, Coracoid pro- cess, i, The broken end of the clavicle, k, Its extremity joined to the acromion. 1, A ligament coming out single from the acromion to the cora- coid process, m, A ligament coming out single from the acromion, and di- viding into two, which are fixed to the coracoid process. Fig. 3. The Joint of the Elbow of the Left Arm, with the Ligaments. a, The os humeri, b, Its internal condyle, cc, The two prominent parts of its trochlea appearing through the capsular ligament, d, The ulna, e, The radius, f, The part of the ligament including the head of the radius. Fig. 4. The Bones of the Right Hand, with the Palm in view. a, The radius, b, The ulna, c, The scaphoid bone of the carpus, d, The os lunare. e, The os cuneiforme. f, The os pisiforme. g, Trape- zium, h, Trapezoides. i, Magnum, k, Unciforme. 1, The four meta- carpal bones of the fingers, m, The first phalanx, n, The second phalanx. o, The third phalanx, p, The metacarpal bone of the thumb, q. The first joint, r, The second joint. Fig. 5. The Posterior View of the Bones of the Left Hand. The explication of Fig. 4, serves for this figure; the same letters point- ing out the same bones, though in a different view. vv EXPLANATION OF THE PLATES OF OSTEOLOGY. Fig. 6. The Upper Extremity of the Tibia, with the Semilunar Cartilages of the Joint of the Knee, and some Ligaments. a, The strong ligament which connects the patella to the tubercle of the tibia, b b, The parts of the extremity of the tibia covered with cartilage. which appear within the semilunar cartilages, c c, The semilunar carti- lages, d, The two parts of what is called the cross ligament. Fig. 7. The Posterior View of the Joint of the Right Knee. a, The os femoris cut. b, Its internal condyle, c, Its external condyle. d, The back part of the tibia, e, The superior extremity of the fibula, f, The edge of the internal semilunar cartilage, g, An oblique ligament, h, A large perpendicular ligament, i, A ligament connecting the femur and fibula. Fig. 8. The Anterior View of the Joint of the Right Knee. b, The internal condyle, c, Its external condyle, d, The part of the os femoris, which the patella moves, e, A perpendicular ligament, ff, The two parts of the crucial ligaments, g g, The edges of the two movable semilunar cartilages, h, The tibia, i, The" strong ligament of the patella. k, The back part of it where the fat has been dissected away. 1, The ex- ternal depression, m, The internal one. n, The cut tibia. Fig. 9. A View of the Inferior part of the Bones of the Right Foot. a, The great knob of the os calcis. b, A prominence on its outside, c, The hollow for tendons, nerves and blood-vessels, d, The anterior extre- mity of the os calcis. e, Part of the astragalus, f, Its head covered with cartilage, g, The internal prominence of the os naviculare. h, The os cu- boides. i, The os cuneiforme internum, k, Medium. 1, Externum, m, The metatarsal bones of the four lesser toes, n, The first, o,' The second. p, The third phalanx of the four lesser toes, q, The metatarsal bones of the great toe. r, Its first—s, Its second joint. Fig. 10. The Inferior Surface of the two large Sesamoid Bones, at the first Joint of the Great Toe. Fig. 11. The Superior View of the Bones of the Right Foot. a, b, as in Fig. 9. c, The superior head of the astragalus, d, &c, as in Fig. 9. Fig. 12. The View of the Sole of the Foot, with its Ligaments. a, The great knob of the os calcis. b, The hollow for the tendons, nerves, and blood-vessels, c, The sheaths of the flexores pollicis and digi- torum longi opened, d, The strong cartilaginous ligament supporting the head of the astragalus, e, h, Two ligaments which unite into one, and are fixed to the metatarsal bone of the great toe. f, A ligament from the nob of the os calcis to the metatarsal bone of the little toe. g, A strong triangular ligament which supports the bones of the tarsus, i, The ligaments of the joints of the five metatarsal bones. EXPLANATION OF THE PLATES OF OSTEOLOGY. 253 Fig. 13. a, The head of the thigh bone of a child, b, The ligamentum ro- tundum connecting it to the acetabulum, c, The capsular ligament of the joint with its arteries injected, d, The numerous vessels of the mucilagi- nous gland injected. Fig. 14. The Back View of the Cartilages of the Larynx, with the Os Hyoides. a, The posterior part of the base of the os hyoides. b b, Its cornua. c, The appendix of the right side, d, A ligament sent out from the appendix of the left side, to the styloid process of the temporal bone, e, The union of the base with the left cornu. f f, The posterior sides of (g) the thyroid cartilage, h h, Its superior cornua. i i, Its inferior cornua. k, the cricoid cartilage. 11, The arytenoid cartilages., m, The entry into the lungs, named glottis, n, The epiglottis, o o, The superior cartilages of the tra- chea, p, Its ligamentous back part. Fig. 15. The Superior Concave Surface of the Sesamoid Bones at the first joint of the Great Toe, with their Ligaments. a, Three sesamoid bones, b, The ligamentous substance in which they are formed. vol. i. 22 PART III. MYOLOGY. CHAPTER VII. GENERAL ANATOMY OF MUSCLES.* That soft, fibrous, red-coloured substance, which constitutes so large a proportion of the volume of the more perfect animals. is called Flesh or Muscle. By the contraction of this substance, the spontaneous motions of animals are produced; and, on this account the fibres which compose it have long been regarded with particular attention. Muscular fibres are not only arranged in those regular masses on the trunk and limbs of the body, which are so familiar to us by the name of muscles, but they also exist in some of the most important viscera, and produce the internal, as well as the exter- nal, motions of animals. —Muscles have been divided in man, and the superior ani- mals, into two classes. The first class consists of those which produce the external motions of the body, and are placed exte- riorly; these contract under the influence of the will, are the agents by which are executed the animal or voluntary functions which place the animal in relation with the exterior world, and are called the muscles of animal life, muscles of the life of rela- tion, voluntary muscles, etc. These form by far the largest por- tion of the whole mass, and are attached in general, by one or both extremities to the skeleton. They are solid, that is, have no cavity in their interior, and vary much in their size. The second class consists of those placed in the interior of the * Muscles were first named according to their figure and situation, in 1587, by Jacques Dubois, surnamed Sylvius, a member of the Faculty of Medicine in Paris.'—h. 256 GENERAL ANATOMY OF MUSCLES. body, and which effect the movements requisite in the various processes of nutrition and generation. These are not under the control of the will, and are called the muscles of organic life, muscles of the life of nutrition, involuntary muscles, etc. They are generally membraniforme, and assist in forming the hollow organs, as in the heart, digestive canal, uterus and bladder. With the exception of those of the heart, the fibres of this class of muscles are of a pale colour, and some entirely colourless. A few of the muscles of animal life, as those of the ears and some of those of the face, are likewise faintly coloured, and are considered by Isenflam,* as existing even in the adult in a state of rudimental developement, as their colour and functions are found much more fully manifested in some quadrupeds.f —The muscles in the inferior grades of animals appear to exist in a rudimental condition, and become more and more numerous, and of a colour more and more red, generally, as we advance upwards from the zero point of the animal scale. In the deve- lopement of the human fetus they seem to undergo analogous changes. —They present themselves during the three first months of foetal life, as gelatinous or viscous masses, very slightly tinged with yellow, and with thin tendons, according to Isenflam, already apparent in the flexors and extensors of the fingers and toes. —At the end of the fourth or fifth month, the muscles present a reddish aspect, and at the period of birth, though they may be readily dissected from each other, they are very soft, and of a colour much less deep than those of the adult.— Muscular fibres are connected to each other by cellular mem- brane. This membrane surrounds each muscle; and its various lamina, gradually diminishing in thickness, pass between the dif- * Anatomische Untersuchungen, by H. F. Isenflam, Professor at the University of Dorpat. t This physiological division of the muscles into two classes, after Bichat, is eminently useful to the student, in enabling him to simplify and generalise his studies of the muscular system; one class is not, however, wholly separate from the other. Between, is interposed another subdivision of muscles, called the Re- spiratory of Sir C. Bell, Excito-motory of Marshal Hall, Miiller, and Grainger.—p. GENERAL ANATOMY OF MUSCLES. 957 ferent bundles of fibres, and the different fibres of which each muscle is composed. The fibres of muscles, when examined with magnifying glasses, appear to be composed of fibrillar still smaller; and it has been supposed that this division of them extended beyond our powers of vision, even when assisted by microscopes: but so many errors have occurred in microscopical observations of very minute objects, and so much difference exists between the reports of different observers, that the subject at this time does not in- terest many persons; and very little attention is paid, by the anatomists and physiologists of the present day, to the opinions of those observers who supposed they had ascertained the struc- ture of the ultimate fibrillae. —The cellular or reticular membrane investing the whole muscle, is called the muscular sheath. It is formed round every muscle of the body, but varies much in different places in regard to thickness and strength. Each of the many fasciculi, or bundles of fibres, (lacerti,) of which every muscle is obviously composed, is surrounded in like manner by processes sent inwards from the sheath, and is a perfect, though diminutive, representa- tive of the entire muscle. —This secondary sheath surrounding the fasciculi, sends pro- cesses likewise inwards, and invests and separates the individual fibres of which each fasciculus is formed. These fibres themselves are again susceptible of subdivision into what are called the ulti- mate muscular filaments, between which, it is probable, though not susceptible of demonstration, the elementary particles of cellular tissue likewise pass. In the muscles of organic life, the cellular tissue is less abundant, but more dense than in those of animal life. In some parts, especially in the digestive canal it is so dense and resistant as to represent a sort of ligamentous tissue, and give attachment to muscular fibres. —The entire muscle thus appears naturally susceptible of three subdivisions. 1st. Into fasciculi, or bundles of fibres. These are the minutest subdivisions which can be made with the naked eye, without resort to boiling or other mechanical means. These are themselves collected into bundles, by septa which pass in 22* 258 STRUCTURE OF MUSCULAR FIBRES. from the general sheath of the muscles, but which are easily un- ravelled by a little dissection; so that what is at first sight mis- taken by the student for a fasciculus, is in reality but a bundle of fasciculi. The size of the ultimate fasciculus, varies in the different muscles of the body, and occasionally in the same mus- cle, according to the number of fibres of which it is composed. 2d. Into fibres. These are rendered very apparent by boiling, as seen daily in culinary preparations, by which the muscular fibre is swoln, while the cellular envelope, at the same time softened and reduced to a gelatinous pulp, is readily burst. These fibres also vary in their thickness, some having a diameter three or four times as great as that of others, depending upon the num- ber of elementary filaments of which it is composed. 3d. Into the elementary, or ultimate muscular filament. These are wholly microscopical, are uniform in their diameter in all muscles, and vary considerably in the numbers taken to consti- tute the muscular fibres of different size.* Each of the muscu- lar fibres, and also, each of the ultimate filaments, according to Prochaska and Rudolphi, extend the whole length of the fleshy part of the muscles, differing entirely in this respect from the ul- timate structure of the bones. —Anatomists do not agree in regard to the diameter assigned the ultimate muscular filament, and from its microscopical diminu- tiveness any measurement can be considered as little more than an approximation. They have been examined by Hook, Lew- enhceck, Dehayde, Muys, and' more recently still by Prochaska and others. According to Prochaska, they are generally straight and parallel with each other, flattened or prismatic, and of a diameter one-fifth of that of the red globules of blood. Auten- reith supposed them equal to one-third of the diameter. Prevost and Dumas found them by their measurement, T4TTtn Part °f an inch in diameter, five or six times smaller than the red globules of the blood, and nearly equal, as Miiller also has asserted, to the diameter of the chyle globules, or to the central nuclei of the red globules of blood, which may be considered the most minute compound constituents of the economy. —Much of this discordance of opinion, is probably owing to * Meckel, torn. i. p. 378. STRUCTURE OF MUSCULAR FIBRES. 259 the examinations not having always been practised upon single and well isolated filaments. From more recent observations by Bauer and Home, Beclard, Prevost, and Dumas, H. Cloquet, and H. M. Edwards, the ultimate filament may be considered as identical in its structure with the particles of blood deprived of their colouring matter, of which the central globules (nuclei) form the filaments by being articulated end to end, by a sort of delicate jelly or mucus, which is probably the elementary form of the cellular tissue.*— These fibrillae have been represented as simple hollow tubes, as a series of globular vesicles, as continuations of arteries, as termination of nerves, as structures of rhomboidal bodies, and finally, as cellular.! It is supposed by one of the latest observers, who appears to be entitled to great attention,! that the muscular fibres are not thus minutely divided: that a single fibre, when separated from the adhering extraneous substances, and viewed in a powerful microscope, is a solid cylinder, formed of a pulpy substance, ir- regularly granulated, and covered by a portion of the reticular membrane. —The opinions of Sir A. Carlysle, are not at the present time, deemed of much weight in anatomy; subsequent researches having shown them to be full of empty and reckless speculation. Among those who consider the muscular fibre as hollow, are Sink and Mascagni; the latter considered it as formed of little cylinders, the walls of which are composed of absorbent vessels and filled with a glutinous substance. More recently, Raspail (Chimie Organique) has adopted a view which appears a modifi- cation of that of Mascagni. He considers each fibre formed of a bundle of cylinders, the cylinders made up of elongated vesi- cles, attached end to end, and having a spiral arrangement.— * For a more full and interesting account of these microscopical investigations, see Human Physiology, fourth edition, by R. Dunglison, M. D., Professor of the Institutes of Medicine and Medical Jurisprudence in Jefferson Medical Col- lege, &c. &c. Phila. 1838.—p. t A statement of these descriptions, witli reference to the publications in which they are contained, may be seen in the Elementa Physiologic of Haller, vol. iv. | Carlysle, in the Croonian Lecture, London Philosophical Transactions, 1805, Part I. 2(50 VASCULARITY OF MUSCLES The connexion of these fibres, with the blood-vessels and nerves, is an important circumstance in the structure of muscles. The arteries of muscles are very numerous; and they ramify minutely. They are accompanied by veins; and it appears, by the successful labours of Ruysch, that when these arteries are fully injected, they not only communicate with the veins, but also pour out some of their contents in a dew-like effusion in the muscle.* —With the exception of some of the viscera, as the lungs and kidneys, there are few organs that receive as much blood as the muscles. —The arteries that supply the muscles, enter them at all points. The larger trunks more generally enter at the middle of the muscle, and ramify towards each extremity, the branches being placed between the larger fasciculi or lacerti, so that the flow of blood, may be less impeded during muscular contraction; mi- nute branches only passing into the structure of the fasciculi. The veins which attend the arteries, are said by Bichat to have few valves. The free distribution of blood to the muscles, ap- pears to be necessary to preserve them in a condition, healthy and capable of contraction. When the supply of blood is cut off, by a ligature, the muscle gradually becomes paralysed, and does not regain its power, till it is again supplied by the anasto- mosing branches. —The colour of the muscle does not seem dependant wholly on the blood, but in part at least, on their own peculiar structure, as seen in many animals, where the flesh is white and the blood red ; and in the muscles of organic life in man, many of which are colourless, though more vascular than those of animal life. —The absorbent vessels exist no doubt in all the muscles, but they are traced with difficulty. They have been found in the muscles of the tongue, face and diaphragm.f— The blood-vessels must terminate, not in the cavities of the mus- cular fibres, but exterior to these fibres ; otherwise the dew-like effusion, would not be apparent; and it is probable, that the red * See Ruysch's description of the 96th preparation in his Thesaurus Quartus; and of the 35th preparation in Thesaurus Decimus. t Vide Breschet, Sur le Systeme Absorbante. Paris, 1836.—p. COLOUR OF MUSCLES. 261 colour, which is so general in muscles, depends upon a portion of blood effused from these vessels, and not contained in them ; for it has been observed by Bichat, that in drowned or strangled animals, black disoxygenated blood occupied all the vessels, while the florid colour of the muscles continued unchanged; which could not have been the case if the colour of the muscles was owing to the blood in the vessels. That the colour of the red muscles is owing to blood, is ren- dered certain by the fact that this colour may be completely washed away while the fibrous structure of the muscle remains unchanged. From this also it may be inferred that the blood is exterior to the muscular fibre, and to the vessels likewise. It is said by Sabatier, that the colour will likewise be com- pletely removed, by injecting a large quantity of water through the arteries; this does not invalidate the inferences drawn from the other facts ; for the water effused from the extreme branches of the arteries must necessarily wash away the blood which was previously effused from the same branches. The water with which muscles have been washed, appears as if some blood had been mixed with it; it contains albumen and gelatine, with some fibrine, and a peculiar extractive substance, as well as the red colouring matter. The substance of the muscle, when thus separated from the above mentioned matter by washing, appears to be of the same nature with the fibrine of the blood: and after boiling some time in the water, it seems, like that substance, to consist of brown insoluble fibres, which are brittle when dry. When the great function of muscles is under consideration, nerves appear of more importance than blood-vessels. The nerves appropriated to muscles of voluntary motion are more numerous than those appropriated to any other parts, except the organs of sense. They subdivide into very fine fibrillae; and it is the opinion of one of the latest observers, that these fibrillae become soft and transparent, and finally blended with the reticu- lar membrane which surrounds the muscular fibres. It ought to be noted that muscles are indued with great sensi- 262 OF THE TENDONS. bility, and that the smallest puncture cannot be made in them without exciting pain. Of the Tendons. Thus arranged, the fibres of muscles are most generally at- tached to tendons, which are inserted into the bones these mus- cles are intended to move. They are also, in some cases, inserted into tendinous membranes, and other parts necessary to be moved; but in all such instances these parts are perfectly passive; and the motion in which they are concerned is alto- gether produced by the contraction of the muscular fibres. —The tendons appear to be formed of a continuation of the cellular membrane which envelopes the fibres of the muscles. The ultimate construction of muscles was shown in page 259, to consist of a multitude of filaments each one composed of a linear series of the muscular molecules; each of the mole- cules being contained in a series of cells of the cellular tissue, all of which are continuous with each other. The muscular matter is found in general only in the middle part of the cellular tissue; the latter is continued on at each extremity of the mus- cle, where it is compacted into a solid mass, presents a liga- mentous appearance, and constitutes the tendons, or cords by which the muscles are attached to the periosteum covering the bone. Hence the tendons are continuous with, and must obey to a certain extent the contraction of every muscular fibre. —The tendons exist under a great variety of forms: most ge- nerally round or cylindrical, sometimes flat, radiated, bifurcated, etc., but are always susceptible, by a little dissection, of being un- folded into a membrane. They have little vascularity, no sensa- tion in a healthy state, no nerves having ever been traced into them, and are of a strength surpassing that of almost any other substance of equal size. They have a great affinity for phos- phate of lime especially in old persons, in whom it is not very unusual to find them ossified; and very frequently at all stages of life, we find developed in their substance sesamoid bones. —The muscles are often from inanition or want of use much wasted away, the red muscular matter disappearing from the OF THE TENDONS. 263 cells in which its particles are contained. The cells, however, remaining, if the system regains its vigour, or the muscles are brought into use, they are filled anew with the muscular mole- cules, and the muscle is restored to its former size, and its con- traction will take place with its usual force. —From this mode of formation, it is evident that there must be an exact relation between the force of the muscle, and the strength of its tendons, even when the muscle is most fully de- veloped. The size and power of the muscle is much dependent upon its use. —The muscles of the legs in dancers, of the arms in black- smiths, of the shoulders and back in porters, all obtain an increase of bulk from use, which still better fits them for the duties they have to perform. This is strongly exemplified in birds; the breast bone and muscles attached to it being more strongly developed than those of the legs, in birds which are much upon the wing; the reverse taking place in the ostrich, cassowary and penguin, which employ the wings only as aids to the feet.— Notwithstanding the great attention that has been paid to this important operation of muscular fibres, the immediate cause is yet unknown. Muscular motion takes place under the following different cir- cumstances :— 1st. When irritation or stimulus is applied directly to the mus- cular fibre. 2d. When irritation is applied to a nerve connected with the muscles. 3d. When it is induced by volition. There are several causes of muscular action which cannot be arranged under either of these heads, although it is probable they are not essentially different; such as the motions of cough- ing and sneezing, of yawning, &c. The immediate irritation of a muscle is effected by every me- chanical process, which punctures, divides, lacerates or extends its fibres; by acrid, and, perhaps, other chemical and peculiar qualities of the substance applied to the muscles; by a sudden change of temperature; and by electricity and galvanism. 264 PHENOMENA OF MUSCULAR MOTION. No satisfactory explanation has yet been made of the manner in which muscular contraction is excited, either by the above- mentioned agents, by irritation applied to a nerve, or by volition. When a muscular fibre begins to contract, there is often the appearance of a slight tremor in it. It becomes hard and rigid: its length diminishes, and its diameter increases. If a muscle makes an effort to contract, when the parts to which its extremi- ties are attached are prevented from moving towards each other, so that contraction cannot take place, the muscle will become hard and rigid notwithstanding. —This tremor of the fibres, is called fibrillary agitation, (agi- tation fibrillaire,) and is heard when a stethoscope is applied over the belly of a muscle during its contraction, or when the end of the finger is introduced into the auditory meatus. During the contraction of a muscle there is no change in its colour, nor any increase in the amount of blood thrown into it by the arte- ries as was once supposed. —With the aid of the microscope it is easy to distinguish the manner in which the contraction of a muscle is effected. Fig. 12, exhibits a magnified view of the muscular fibres in a state of relaxation. When they contract they form suddenly a number of zigzag flexions, or angular undulations, opposite each other, as seen it) Fig. 13, page 265, according to the observation of Edwards,-f Prevost, and Dumas. By repeated experiments, these gentlemen have determined that the flexures of each fibre take place at certain determined points, and nowhere else. These points are precisely at the places where the nerve a, the brink of * a, Nerve, b b, Fasciculi of muscular fibres which are straight and parallel, c, Nervous filament which separates from the nerve a, and crosses at right angles, and at regular distances, the muscular fasciculi. t Elements de Zoologie, etc., par M. H. Edwards. Paris, 1838. Fig. 12.* h ? 6 PHENOMENA OF MUSCULAR MOTION. 265 which runs parallel with the muscular fibres, sends off its filaments to traverse the muscu- lar fibres, at the spot where the angles of the undulations are formed. These nervous fila- ments after having continued the course for c< some time, are reflected in the form of loops, and return towards the brain, so as to consti- tute with that organ a continuous circle. Du- c< ring the contraction of the muscle its extremi- ties approach, for though the absolute length of the fibre remains the same, the distance i h between its extremities is diminished by the undulations. The will transmitted through the nerves is the usual stimulus, which excites the voluntary muscles to contraction. Galvanic elec- tricity, or disease of nervous centres will produce the same result; that of the involuntary muscles, usually results from the impression made upon the organs, as by food in the stomach, blood in the heart, urine in the bladder, &c.— It has often been inquired whether the whole bulk of a muscle is diminished or increased by its contraction. It now seems generally agreed that the bulk is not increased; and, if there is any real diminution of the fibre itself, it is very small indeed. The irritability of the muscular fibre, or its power of contract- ing upon the application of stimulus, exists in a greater degree in some muscular parts than others. It is suspended by the ap- plication of narcotic substances; and it remains, in many cases, a short time after the vital functions have ceased. In a majority of cases a general contraction seems to take place in the last moments of life; and after death the body is stiff in consequence of it; all the movable parts being fixed in the pre- cise situation in which they were when the vital motions ceased. The limbs being generally in a bended position at that time, if an attempt be made to extend them it will be very evident that the contracted state of the muscles impedes this extension. When this contraction is once overcome, the limbs continue perfectly * Fig. 13. The same muscle at the moment of contraction, and a b c, indicates the same, as in Fig. 12. vol. i. 23 266 PHENOMENA OF MUSCULAR MOTION. flexible, and the muscles are ever after relaxed ; but the force ef contraction is sometimes so great that it will require a consider- able exertion of strength to overcome it. This condition of the muscles, after death, although very common, is not universal: and some dead subjects are perfectly relaxed and flexible from the first cessation of the vital functions. The force with which muscles contract exceeds greatly their inanimate power of cohesion. Thus, a muscle deprived of life, would be completely lacerated by a weight suspended from it, which it could readily raise by its contraction during life. This force of contraction is so great, that the tendo-achillis and the patella have been repeatedly broken by the mere power of the muscles, inserted into them. The rapidity with which the successive contractions of the same parts take place is extreme; and as a striking proof of it, the motions of the tongue, in rapid speaking or reading, are re- ferred to by physiologists. The extent or degree of muscular contraction, is, in some cases, very great. In proof of this it was stated by the second Monro, that crude mercury, which passes so readily through the intes- tines, could not be carried along any parts of them whose posi- tion happened to be perpendicular, (as the colon on the right side when we stand,) unless the circular fibres of the intestine contract behind it to such a degree as to close completely the cavity of that tube. An interesting question may be proposed here,—Whether the power of motion, as above described, is exclusively enjoyed by muscular fibres; whether these fibres must be supposed to exist in all those parts of the body which occasionally perform contraction! It has often been inferred, that parts were muscular because they were capable of contraction; but the question above ought to be decided affirmatively before such inferences can be pro- perly made. The sac of the tasnia hydatigena appears to be a membrane of a peculiar structure, very different from muscle; yet it is as capable of contracting as if it were perfectly muscular.* * See the Croonian Lecture by Mr. Home; London Philosophical Transactions for 1795, Part I. page 204. PHENOMENA OF MUSCULAR MOTION. og* The membrane of the urethra does not appear to be muscular in its structure; and yet it has been seen to protrude a bougie, which had passed near to the neck of the bladder, in a way that indicated regular successive contraction, throughout its whole extent. The question above stated, may, therefore, be considered as not yet decided affirmatively. Muscular fibres are situated very differently in different parts. They compose almost the whole substance of the heart, which is therefore called a hollow muscle. They also form one of the coats of the stomach and intestines, and of the urinary bladder. In the muscles on the trunk and limbs, their arrangement is very various, being rectilinear, penniform, radiated, &c. There are a great many short fibres, with an oblique direc- tion, in some muscles of small volume, which have therefore great power and little motion, as in the semimembranosus. —Contraction, though the only power that muscles appear to exercise, is found likewise existing to some extent, in other tissues of the body, where some effort and resistance is required in the performance of their functions, without the necessity of that perfect antagonism of action which muscles usually establish. There appears, in fact, to be a regular gradation in the changes of the condition of the muscular fibre. The muscles of animal life in man are the most fully developed, most highly coloured, and enjoy to the fullest extent, the powers of contraction. Their only vital action is that of contraction, which has been before explained, (see page 264,) which causes their ends to approach each other, by moving one or the other of the bones, to which the two ends of the muscles are attached. One of the bones is usually more readily moved than the other, and that is the action of the muscle as usually set down in books. But the student will do well to impress upon his mind, that that is not the only movement which the muscle can effect, and that if the part which it usually moves, becomes, from some adventitious cause more solidly fixed than the other, as from a weight attached to it, or the opposing action of other muscles, the contraction of the muscles will produce a movement of the part, at which its 268 ANTAGONISM OF MUSCLES. other extremity is inserted. In this way the action of muscles is beautifully varied, and very complicated and useful move- ments are produced in the body, by what seems a very simple arrangement of the muscles. Thus the action of the great pec- toral and latissimus dorsi muscles is usually to pull down the arms when they have been elevated by other muscles. But if the arms are thrown upwards, and the hands grasp some place above, as the limbs of a tree, they then raise the body upwards towards the arms, and thus become the muscles used in climbing. —In violent dyspnoea, arising from spasmodic croup, asthma, or other causes, the arms are frequently drawn upwards so firmly by the muscles at the top of the shoulders, that the pectoralis major and latissimus dorsi cannot pull them down. When they contract, therefore, their extremities are made to approach by raising the ribs to which they are in part attached, and thus be- come muscles of forced inspiration. —The muscles of animal life are arranged, so that each one has its antagonist, or opposing muscle. Thus, there are flexors to bend the limbs, and extensors to straighten them, supinators and pronators, elevators and depressors. The muscles, which are very numerous, and like the bones are variously estimated, from 368 by Chaussier, to 400 or more by other writers, and produc- ing by their single action a great variety of movements, are yet combined together in pairs or much larger numbers, so as to extend beyond computation the variety of movements they are capable of producing. Thus the two muscles already named, one of which, when acting separately, draws the arm usually downwards and forwards, the other downwards and back- wards, when combined together draw it down in the diagonal or middle line. —The antagonism of the muscles is dependent upon their alter- nate contraction: the shortened or contracted muscle, is re- stored to its former length chiefly by the contraction of its anta- gonist, but partly also by the resiliency of the cellular tissue in its composition. They are also capable of acting to a certain extent in unison, and thus give firmness and steadiness to the limbs or other parts, and hold them in a fixed direction, as MODE OF INSERTION. 269 occurs habitually in walking or standing, or pointing with the arm. —The antagonising muscles do not appear to be equally ba- lanced in regard to power; thus the most usual attitudes, in sleep, palsy or tetanus, where the muscles are uninfluenced by the will, is the extended position for the back, flexion to the arm in general, pronation to the fore arm, flexion to the lower ex- tremities and adduction to the foot. This is not dependent upon a difference in length, as was supposed by Borelli, but, according to Beclard, chiefly upon a difference in size, and the relative ad- vantages of insertion upon the bones. —Muscles have their tendons attached to the bones, in a manner to give them the least mechanical power, but to effect the greatest rapidity of motion; for, as has been observed by Archdeacon Paley, it is of far greater importance to man, to be able to carry his arm quickly to his head, than to raise several hundred weight more than he is now able to do: the two qualities could not well exist together. All that could be done to increase the power, with- out impairing the symmetry of the body, or diminishing the celerity of its movements, has been accomplished in endowing the mus- cles, with an extraordinary force of contraction, at least ten fold as great as the student would at first suppose it. The muscles are nearly all levers of the third order. —The force with which a muscle contracts, depends upon its volume and the energy of the will, as well as some other circum- stances. But the effect produced by the contraction will depend in a great measure upon the manner in which it is inserted upon the bone on which it acts. —Thus, all things being the same, the effect of the contraction will be the greater, in proportion as the muscle is less obliquely con- nected with the bone. Thus of the muscle m, figure 14, the force of which we suppose equal to 10, is fixed perpendicularly to the bone I, the extremity of which a, is mova- ble upon the fulcrum point r, it will have to overcome only the weight 23* Fig. 14. & 1} i 270 FORCE OF MUSCULAR CONTRACTION. of the bone, and will carry it from the position a b, into the direction of the line a c. But if this muscle acted obliquely upon the bone in the direction of the line n b, it would then tend to carry it in the direction of the line b n, and consequently to force it against the fixed articular surface r. This latter being a fixed surface, the bone can only turn upon the point r, as upon a pivot, and the contraction of the muscle n, having the same force as the muscle m, would only be able to carry the bone in the direc- tion a d, and would require a force equal to 40, or four times that of m, to raise it in the direction of the line a c. —In the animal economy the muscles are inserted most usually, very obliquely, and consequently in a manner little favourable to the intensity of the result of their contraction. There is never- theless a very happy contrivance, which tends to diminish the obliquity of their insertions, without marring the usefulness or symmetry of the limbs. It is the articular swellings at the ex- tremities of the bones, which contribute also to the stability of the joints. —The tendon i of the muscles m, Fig. 15, are inserted in general immediately below the articulation, upon the mobile bone o, in a direction more Fig. 15. approaching the perpendicular, thus making the head of the bone a sort of pulley over m which it acts, by which the effect of the contraction is considerably increased. 1 —A more striking instance is met with in the deltoid muscle. Baron Haller, has made an interesting cal~ culation of the absolute force required to be exerted by the del- toid muscle, in order to raise a weight of 60 pounds at the elbow, reckoning the weight of the arm^at 5 pounds of this. Its inser- tion is at an angle of 10 degrees upon the humerus, and at about one-third of the distance between the shoulder and elbow. The force requisite to raise a weight is exactly in the proportion, of the distance which the weight from the fulcrum bears to that of the power from the fulcrum. Thus, from the disadvantage of insertion, the force requisite to be exercised there is three times as great as it would be if inserted at the elbow; therefore the MUSCLES OF ORGANIC LIFE. 27] actual weight lifted, as far as the muscle is concerned, is equal to 180 pounds. —But this is not all. The insertion of the muscle at an angle of 10 instead of 90 degrees, takes off the purchase in the proportion, as mathematicians have calculated, which 173 bears to 1000. The augmented weight, or what is the same thing, the increase of power necessary to raise it, amounts, therefore, to no less than 1058, instead of the original 60 pounds. There is yet another source of loss of effect in its contraction, which requires great additional power in the muscle to counteract it. The tendon of the muscle is never directly continuous with the muscular fibres, and the loss of power is exactly in proportion to the obliquity of their junction. The manner of this loss is evinced, when we attempt to draw a body to us, at one time with a crooked, and at another, with a straight bar or stick. From this cause there would be a further loss of power of 228 pounds, which would augment the muscular energy, required to raise the 60 pounds, up to 1284, according to this physiologist. —In the muscles of organic life, destined to act without the aid of the will, the system of antagonism, is much less perfectly de- veloped. These muscles are hollow, and their fibres are arranged generally into layers, which cross each other at right angles, and contribute, to a certain extent, to produce this effect. The alternate contractions of the auricles and ventricles of the heart, and of the uterus, though these organs have, properly speaking, no antagonist muscles, belong to this class. In some of the hollow organs, as the bladder, the contracted muscular fibres are ex- panded or antagonised, only by the matters which collect in their cavities. —The muscles of organic life, with the exception of the heart, are of a pale or grayish white colour. Some of them are so thin, and of so pale a colour, that it is impossible to draw the line of distinction between them and cellular or aponeurotic tissue. —There is a regular gradation between muscular and desmoid cellular tissue, and an occasional substitution of the one for the other, in parts that require elastic resistance, or firm support, that has been overlooked by anatomists. The yellow elastic 272 CHEMICAL COMPOSITION. ligamentous tissue, appears to be the medium between the mus- cular and ligamentous tissue. Comparative anatomy shows us that parts formed in one animal of the elastic yellow tissue, are in others composed of muscular fibres. Thus, the suspensory ligaments of the sheath of the penis, are ligamentous in the horse, and muscular in the mule and bull. The middle coat of the arteries, which is composed of the elastic yellow tissue in man, is muscular in certain parts of the arterial system of the elephant. —The parietes of the urethra, which, in man, is strongly elastic, in the horse and many other animals is endowed with a strong coat of palish muscular fibres. The kindred nature of these two tissues, is likewise strongly manifested by chemical analysis. The yellow elastic tissue consists chemically of albumen, os- mazome and fibrine.* The thick yellow elastic ligament which supports the weight of the abdominal viscera in the horse, and others of the solipediee, consists, in man, only of the fascia su- perficialis abdominis, and forms, as a late writer is disposed to think, the abdominal pouch, (poche musculaire,) of the didelphic animals, such as the opossum and kangaroo. The muscular fibres on the inner face of the prostate glands, and the muscles of Wilson, on the membranous part of the urethrae seem to be allied to this class of tissue. It also seems borne out by the de- velopement of the muscles in the foetus, as previously quoted from Isenflam. —Muscles are composed chemically, according to Berzelius, prin- cipally of fibrine; but they contain also albumen, gelatine, os- mazome, phosphates of soda, ammonia and lime, carbonate of lime, and some free lactic acid. If the analysis is pushed farther to the destruction of the flesh, there is developed a great quan- tity of nitrogen, hydrogen, oxygen and carbon, some iron, phos- phorus, soda and lime. * Consid. sur les aponeuroses abdom. servant d'introduction & l'histoire des Hernies, dans les Monodactyles, par Girard, fils. INDIVIDUAL MUSCLES. 273 CHAPTER VIII. OF THE INDIVIDUAL MUSCLES. Muscles of the Teguments of the Cranium. The skin that covers the cranium is moved by a single broad digastric muscle, and one small pair. 1. Occipito-Fron talis, Arises fleshy from the transverse protuberant ridge near the middle of the os occipitis laterally, where it joins with the tem- poral bone; and tendinous from the rest of that ridge back- wards, opposite to the lateral sinus; it rises after the same man- ner on the other side. From thence it comes straight forwards, by a broad thin tendon, which covers the upper part of the cra- nium at each side, as low down as the atlollens auris, to which it is connected, as also to the zygoma, and covers a part of the aponeurosis of the temporal muscle; at the upper part of the forehead it becomes fleshy, and descends with straight fibres. Inserted into the orbicularis palpebrarum of each side, and into the skin of the eyebrows, sending down a fleshy slip between them, as far as the compressor naris and levator labii superioris alaeque nasi. Use. Pulls the skin of the head backwards; raises the eye- brows upwards; and, at the same time, it draws up and wrin- kles the skin of the forehead. 2. Corrugator Supercilii. Arises fleshy from the internal angular process of the os fron- tis, obove the joining of the os nasi, and nasal process of the su- perior maxillary bone; from thence it runs outwards, and a little upwards. Inserted into the inner and inferior fleshy part of the occipito- frontalis muscle, where it joins with the orbicularis palpebrarum, 274 MUSCLES OF THE EAR. and extends outwards as far as the middle of the superciliary ridge. Use. To draw the eyebrow of that side towards the other, and make it project over the inner canthus of the eye. When both act, they pull down the skin of the forehead, and make it wrinkle particularly between the eyebrows. Muscles of the Ear. 1. Atlollens Auris, Arises, thin, broad, and tendinous, from the tendon of the occipito-frontalis, from jy_ jg* which it is almost in- separable, where it co- vers the aponeurosis of the temporal muscle. Inserted into the up- per part of the ear, op- posite to the antihelix. Use. To draw the ear upwards, and make the parts, into which it is inserted, tense. 2. Anterior Auris, Arises, thin and mem- branous, near the pos- terior part of the zygo- ma. Inserted into a small eminence on the back of the helix, opposite to the concha. Use. To draw this eminence a little forwards and upwards. * Fig. 16.—g, Occipito-frontalis. wi, Nasal slip of do. n. Compressor naris. k, Levator labii superioris alaeque nasi. 5, Masseter. q, Atlollens auris. r, Re- trahentes auris, usually two in number, p, Plat.ysma myoides. «, Stemo-cleid'o- mastoid. u, Trapezius, v, Splenius capitis, b, Splenius colli, to, Deltoid. The rest of the muscles known by references to the cuts No. 17, 18,19. MUSCLES OF THE EYELIDS. 275 3. Retrahentes Auris, Arise, sometimes by three, but always by two distinct small muscles, from the external and posterior part of the root of the mastoid process, immediately above the insertion of the sterno- cleido-mastoid muscle. Inserted into that part of the back of the ear which is opposite to the septum that divides the scapha and concha. Use. To draw the ear back, and stretch the concha. Muscles of the Eyelids. The palpebrse or eyelids, have one muscle common to both, and the upper eyelid one proper to itself. 1. Orbicularis Palpebrarum, Arises, by a number of fleshy fibres, from the outer edge of the orbitar process of the superior maxillary bone, and from a tendon near the inner angle of the eye; these run a little down- wards, then outwards, over the upper part of the cheek, below the orbit, covering the under eyelid, and surround the external angle, being loosely connected only to the skin and fat; run over the superciliary ridge of the os frontis, towards the inner canthus, where they intermix with those of the occipito-frontalis and corrugator supercilii; then covering the upper eyelid, they descend to the inner angle opposite to the inferior origin of this muscle, firmly adhering to the internal angular process of the os frontis, and to the short round tendon which serves to fix the palpebrae and muscular fibres arising from it. Inserted, by the short round tendon, into the nasal process of the superior maxillary bone, covering the anterior and upper part of the lachrymal sac; which tendon can be easily felt at the inner canthus of the eye. Use. To shut the eye, by drawing both lids close together, the fibres contracting from the outer angle towards the inner, press the eyeball, squeeze the lachrymal gland, and convey the tears towards the puncta lachrymalia. —When the muscle is in strong action, its upper fibres cause 276 MUSCLES OF THE EYEBALL. the skin of the forehead to descend, the lower ones elevate the integuments of the cheek. Like the other sphincters, this is a mixed muscle. The fibres which are supposed to be the proper voluntary portion, are those which correspond to the margin of the orbit, and are of a red colour. The involuntary fibres, form the thin portion which covers the lids, (musculus ciliaris ofAlbi- niis,) and are of a pale colour, like the muscles of organic life. They contract involuntarily while we are awake, in the action of winking, and during sleep in maintaining the lids closed.— The ciliaris of some authors is only a part of this muscle co- vering the cartilages of the eyelids, called cilia or tarsi. There is often a small fleshy slip, which runs down from the outer and inferior part of this muscle above the zygomaticus mi- nor, and joints with the levator labii superioris alaeque nasi. 2. Levator Palpebra Superioris, Arises from the upper part of the foramen opticum of the sphenoid bone, through which the optic nerve passes, above the levator oculi, near the trochlearis muscle. Inserted, by a broad thin tendon, into the cartilage that sup- ports the upper eyelid, named tarsus. Use. To open the eye, by drawing the eyelid upwards; which it does completely, by being fixed to the tarsus, pulling it below the eyebrow, and within the orbit.* Muscles of the Eyeball. The muscles which move the globe of the eye are six, viz.: four straight, and two oblique. The four straight muscles very much resemble each other: all Arising by a narrow beginning, a little tendinous and fleshy, from the bottom of the orbit around the foramen opticum of the sphenoid bone, where the optic nerve enters, so that they may be taken out adhering to this nerve; and all having strong fleshy bellies. * There is no antagonist muscle provided especially to depress the lower lid. Its depression is effected, according to the suggestion of Sir C. Bell, by the protru- sion of the eyeball.-—p. MUSCLES OF THE EYE. 277 Inserted at the forepart of the globe of the eye into the anterior part of the tunica sclerotica, and under the tunica adnata, at op- posite sides, which indicates both their names and Use; so that they scarcely require any farther description than to name them singly. 1. Levator Oculi, (Rectus Superior,) Arises from the upper part of the foramen opticum of the sphe- noid bone, below the levator palpebrae superioris, and runs for- wards to be Inserted into the superior and forepart of the tunica sclerotica, by a broad thin tendon. Use. To raise up the globe of the eye. 2. Depressor Oculi, (Rectus Inferior,) Arises from the inferior part of the foramen opticum. Inserted opposite to the former. Use. To pull the globe of the eye down. 3. Adductor Oculi, (Rectus Internus,) Arises, as the former, between the obliquus superior and de- pressor, being, from its situation, the shortest. Inserted opposite to the inner angle. Use. To turn the eye towards the nose. 4. Adductor Oculi, (Rectus Externus,) Arises from the bony partition between the foramen opticum and lacerum, being the longest from its situation ; and is Inserted into the globe opposite to the outer canthus. Use. To move the globe outwards. The oblique muscles are two: Obliquus Superior, seu Trochlearis, Arises, like the straight muscles, from the edge of the foramen opticum at the bottom of the orbit, between the levator and ad- ductor oculi; from thence, runs straight along the pars plana of the ethmoid bone to the upper part of the orbit, where a cartila- vol. i. 24 278 MUSCLE OF THE NOSE. ginous trochlea is fixed to the inside of the internal angular pro- cess of the os frontis, through which its tendon passes, and runs a little downwards and outwards, enclosed in a loose membra- nous sheath. Inserted, by a broad thin tendon, into the tunica sclerotica, about half way between the insertion of the atlollens oculi and optic nerve. Use. To roll the globe of the eye, and turn the pupil down- wards and outwards, so that the upper side of the globe is turned inwards, and the inferior part to the outside of the orbit, and the whole globe drawn forwards towards their inner canthus. 2. Obliquus Inferior, Arises, by a narrow beginning, from the outer edge of the orbitar process of the superior maxillary bone, near its juncture with the os unguis ; and running obliquely outwards, is Inserted into the sclerotica, in the space between the adductor and optic nerve, by a broad and thin tendon. Use. To draw the globe of the eye forwards, inwards, and downwards; and, contrary to the superior, to turn the pupil up- wards towards the inner extremity of the eyebrow; at the same time, the external part of the globe is turned towards the inferior side, and the internal rolls towards the upper part. The Muscle of the Nose. There is only one muscle on each side that can be called proper to the nose, though it is affected by several muscles of the face. Compressor Naris, (Triangularis seu Transversalis Nasi,) Arises, by a narrow beginning, from the root of the ala nasi externally, where part of the levator labii superioris alaeque nasi is connected to it; it spreads into a number of thin separate fibres, which run up along the cartilage in an oblique manner towards the dorsum of the nose, where it joins with its fellow, and is Inserted slightly into the anterior extremity of the os nasi and MUSCLES OF THE MOUTH AND LIPS. 279 nasal process of the superior maxillary bone, where it meets with some of the fibres descending from the occipito-frontalis muscle.* Use. To compress the ala towards the septum nasi, particu- larly when we want to smell acutely; but, if the fibres of the frontal muscle, which adhere to it, act, the upper part of this thin muscle assists to pull the ala outwards. It also corrugates the skin of the nose, and assists in expressing certain passions. —It has been called by Columbus dilataus nasi, from a belief, in which Bougery coincides, that when it acts with its extremity upon the nose as the fixed point, it dilates the nostril. When the other extremity of the muscle is the fixed point, it compresses it.— Muscles of the Mouth and Lips. The mouth has nine pair of muscles, which are inserted into the lips, and a common one formed by the termination of these, viz. three above, three below, three outwards, and the common muscle sur- rounds the mouth. The three above are, 1. Levator Anguli Oris, Arises, thin and fleshy, from the hollow of the superior maxillary bone, between the root of the socket of the first dens molaris and the foramen infra orbita- rium. * The nasal slip of fibres descending from the occipito-frontalis, is sometimes spoken of as a distinct muscle, under the name of Pyramidalis nasi. Fig. 17.—g, OccipitO'frontalis. I, Levator labii superioris aleeque nasi. I, Levator anguli oris. n, Compressor naris. o, Orbicularis palpebrarum; the external palpebral ligament, Fig. 17. 2gQ MUSCLES OF THE FACE. Inserted into the angle of the mouth and under lip, where it joins with its antagonist. Use. To draw the corner of the mouth upwards, and make that part of the cheek opposite to the chin prominent, as in smiling. 2. Levator Labii Superioris Alaque Nasi, Arises by two distinct origins: the first broad and fleshy, from the external part of the orbitar process of the superior maxillary bone which forms the lower part of the orbit, immediately above the foramen infra-orbitarium; the second portion arises from the nasal process of the superior maxillary bone, where it joins the os frontis at the inner canthus, descending along the edge of the groove for the lachrymal sac. The first and shortest portion is Inserted into the upper lip and orbicularis labiorum; the second and longest, into the upper lip and outer part of the ala nasi. Use. To raise the upper lip towards the orbit, and a little out- wards ; the second portion serves to draw the skin of the nose upwards and outwards, by which the nostril is dilated. 3. Depressor Labii Superioris Alaque Nasi, Arises, thin and fleshy, from the os maxillare superius, imme- diately above the joining of the gums with the two dentes inci- sores and the dens caninus ; from thence it runs up under part of the levator labii superioris alaeque nasi. Inserted into the upper lip and root of the ala nasi. Use. To draw the upper lip and ala nasi downwards and backwards. The three below are, seen on the right side, extending to the ear. 3 3, Zygomaticus major, and minor. 4, Orbicularis oris, with the slip to the lower part of the septum of the nose, called by Albinus, nasalis labii superioris. 5, Masseter. t, Depressor anguli oris, s s, Sternal and clavicular portions of the sterno-cleido-mastoid. w, Trapezius seen at its upper part. 6, Sterno-hyoid. 7, Sterno-thyroid. 8, Omo-hyoid. 9, Scalenus anticus. 10, Scalenus medius. MUSCLES OF THE FACE. 281 1. Depressor Anguli Oris, Arises, broad and fleshy, from the lower edge of the maxilla inferior, at the side of the chin, being firmly connected to that part of the platysma myoides, which runs over the maxilla to the angle of the mouth, to the depressor labii inferioris within, and to the skin and fat without, gradually turning narrower; and is Inserted into the angle of the mouth, joining with the zygo- matics major and levator anguli oris. Use. To pull down the corner of the mouth. 2. Depressor Labii Inferioris, Arises, broad and fleshy, intermixed with fat, from the inferior part of the lower jaw next to the chin; runs obliquely upwards, and is Inserted into the edge of the under lip, extends along one half of the lid, and is lost in its red part. Lse. To pull the under lip and the skin of the side of the chin downwards, and a little outwards. 3. Levator Labii Inferioris, Arises, from the lower jaw, at the roots of the alveoli of two dentes incisores and of the cani- nus; is Inserted into the under lip and skin of the chin, Use. To pull the parts, into which it is inserted, upwards. The three outward are, 1. Buccinator, Arises, tendinous and fleshy, from the lower jaw, as far back * Fig. 18.—a, Depressor labii inferioris. b, Buccinator, c, Levator anguli "oris, e, Levator labii inferioris (levator mcnti;) this will he best seen in dissection 24 * Fig. 18. 282 MUSCLES OF THE FACE. as the last dens molaris and forepart of the root of the coronoid process; fleshy from the upper jaw, between the last dens mo- laris and pterygoid process of the sphenoid bone; from the ex- tremity of this process it arises tendinous, being continued between both jaws to the constrictor pharyngis superior, with which it joins; from thence, proceeding with straight fibres, and adhering close to the membrane that lines the mouth, it is Inserted into the angle of the mouth within the orbicularis oris. Use. To draw the angle of the mouth backwards and out- wards, and contract its cavity, by pressing the cheek inwards, by which the food is thrust between the teeth. —The buccinator acts principally in front on the commissure of the lips, which it draws backwards horizontally, increasing the transverse aper- ture of the mouth, and throwing the cheek into the vertical folds, so conspicuous in old age. It thus antagonises the orbicularis oris. If both these muscles act together, the lips are extended and pressed against the teeth. When the cavity of the mouth is distended with air or liquids, the fibres of this muscle are pro- truded and curved. If the muscle now acts, the fibres become straightened, and the fluid is expelled from the mouth, suddenly or gradually, according to the resistance made by the orbicu- laris. —This muscle assists also in mastication and deglutition, by pressing the food from between the cheek and gums into the cavity of the mouth.— 2. Zygomaticus Major, Arises, fleshy, from the os mala?, near the zygomatic suture. Inserted into the angle of the mouth, appearing to be lost in the depressor anguli oris and orbicularis oris. Use. To draw the corner of the mouth and under lip towards the origin of the muscle, and make the cheek prominent, as in laughing. by inverting the lip and dissecting off the mucous membrane. /, Depressor anguli oris. 5, Masseter. g, Tendon of the superior or internal oblique muscle of the eye, after it passes its trochlea, h, Inferior oblique. MUSCLES OF THE LOWER JAW 283 2. Zygomaticus Minor, Arises from the upper prominent part of the os mala?, above the origin of the former muscle; and, descending obliquely downwards and forwards, is Inserted into the upper lip, near the corner of the mouth, along with the levator anguli oris. Use. To draw the corner of the mouth obliquely outwards and upwards towards the external canthus of the eye. The common muscle is the Orbicularis Oris. This muscle is, in a great measure, formed by the muscles that move the lips; the fibres of the superior descending, those of the inferior ascending, and decussating each other about the corner of the mouth, run along the lip to join those of the oppo- site side, so that the fleshy fibres appear to surround the mouth like a sphincler. Use. To shut the mouth, by contracting and drawing both lips together, and to counteract all the muscles that assist in form- ing it. There is another small muscle described by Albinus, which he calls Nasalis labii superioris; but it seems to be only some fibres of the former connected to the septum nasi. —The orbicularis, possesses a very varied and extensive ac- tion, and may act as a whole or in parts. Its simplest action is to close the mouth by bringing the lips together. The upper or lower labial fibres may act separately, as well as those at the commissures of the lips, by which they are enabled in turn, to antagonise the different muscles which are attached around. By a very strong contraction of the labial and commissural fibres, the lips are thrown forwards in a circular projection, as in whistling. By the contraction of the inner labial fibres, they are drawn inwards upon the teeth.— Muscles of ihe Lower Jaw. The lower jaw has four pair of muscles for its elevation or 284 MUSCLES OF THE LOWER JAW lateral motions, namely, two, which are seen on the side of the face, and two concealed by the angle of the jaw. 1. Temporalis, Arises, fleshy, from a semicircular ridge of the lower and late- ral part of the parietal bone, from all the pars squamosa of the temporal bone, from the external angular process of the os fron- tis, from the temporal process of the sphenoid bone, and from an aponeurosis which covers it; from these different origins the fibres descend like radii towards the jugum, under which they pass; and are Inserted, by a strong tendon, into the upper part of the coro- noid process of the lower jaw ; in the duplicature of which ten- don this process is enclosed as in a sheath, being continued down all its forepart to near the last dens molaris. Use. To pull the lower jaw upwards, and press it against the upper, at the same time drawing it a little backwards. N. B. This muscle is covered with a tendinous membrane, called its aponeurosis, which arises from the bones that give ori- gin to the upper and semicircular part of the muscle; and de- scending over it, is inserted into all the jugum, and the adjoining part of the os frontis. The use of this membrane is to give room for the origin of a greater number of fleshy fibres, to fortify the muscle in its ac- tion, and to serve as a defence to it. 2. Masseter, Arises, by strong, tendinous, and fleshy fibres, which run in different directions, from the superior maxillary bone, where it joins the os mala?, and from the inferior and anterior part of the zygoma, its whole length, the external fibres slanting backwards, and the internal forwards. Inserted into the angle of the lower jaw, and from that up- wards to near the top of its coronoid process. Use. To pull the lower to the upper jaw, and by means of its oblique decussation, a little forwards and backwards. MUSCLES OF THE NECK. 285 3. Pterygoideus Internus, Arises, tendinous and fleshy, from the inner and upper part of the internal plate of the ptery- goid process, filling all the space Fig. 19.* between the two plates; and from the pterygoid process of the os palati between these plates. Inserted into the angle of the lower jaw internally. Use. To draw the jaw up- wards, and obliquely towards the opposite side. 4. Pterygoideus Externus, Arises from the outer side of the external plate of the ptery- goid process of the sphenoid bone, from part of the tuberosity of the os maxillare adjoining to it, and from the root of the tempo- ral process of the sphenoid bone. Inserted into the cavity in the neck of the condyloid process of the lower jaw; some of its fibres are inserted into the liga- ment that connects the movable cartilage and that process to each other. Use. To pull the lower jaw forwards, and to the opposite side; and to pull the ligament from the joint, that it may not be pinch- ed during these motions : when both external pterygoid muscles act, the fore teeth of the under jaw are pushed forwards beyond those of the upper jaw. The Muscles which appear about the anterior part of the Neck. On the side of the neck are two muscles, or layers. 1. Musculus Cutaneus, vulgo Platysma Myoides, (see Fig. 16,) Arises, by a number of slender separate fleshy fibres, from the *Fig. 19.—b, Buccinator, d, Depressor labii inferioris. A, Corrugator Super- cilii. n, Compressor naris. s, Sterno-cleido-mar-toid. t, Temporal, u, Tra- pezius, v, Splenius capitis, v, Splenius colli, x, Digaslricus. y, Mylo-hyoid, ?, Stylo hyoid. &, Hyo-glossus. 286 MUSCLES OF THE NECK. cellular substance that covers the upper parts of the deltoid and pectoral muscles; in their ascent they all unite to form a thin muscle, which runs obliquely upwards along the side of the neck, adhering to the skin. Inserted into the lower jaw, between its angle and the origin of the depressor anguli oris, to which it is firmly connected, and but slightly to the skin that covers the inferior part of the mas- seter muscle and parotid glands. Use. To assist the depressor anguli oris in drawing the skin of the cheek downwards; and when the mouth is shut, it draws all that part of the skin, to which it is connected, below the lower jaw, upwards. —Some of its fibres are inserted into the angle of the mouth, and are connected with the muscles of that region. They draw the corner of the mouth downwards, and constitute the musculus risorius of Santorini.— 2. Stemo-cleido-mastoideus, (see Fig. 17,) Arises by two distinct origins: the anterior tendinous and a little fleshy, from the top of the sternum near its junction with the clavicle; the posterior, fleshy, from the upper and anterior part of the clavicle; both unite a little above the anterior articulation of the clavicle, to form one muscle, which runs obliquely up- wards and outwards, to be Inserted, by a thick strong tendon, into the mastoid process, which it surrounds; and, gradually turning thinner, is inserted as far back as the lambdoid suture. Use. To turn the head to one side, and bend it forwards. Muscles situated between the Lower Jaw and Os Hyoides. There are four layers before, and two muscles at the side. The four layers are, 1. Digastricus, (see Fig. 18,) Arises, by a fleshy belly, intermixed with tendinous fibres, from the fossa at the root of the mastoid process of the temporal bone, and soon becomes tendinous; runs downwards and for- wards : the tendon passes generally through the stylo-hyoideus MUSCLES OF THE NECK. 287 muscle; then it is fixed by a ligament to the os hyoides; and, havino- received from that bone an addition of tendinous and muscular fibres, runs obliquely forwards, turns fleshy again, and is Inserted, by its anterior belly, into a rough sinuosity at the in- ferior and anterior edge of that part of the lower jaw called the chin. Use. To open the mouth by pulling the lower jaw downwards, and backwards; and when the jaws are shut, to raise the os hyoides, and, consequently, the pharynx, upwards, as in deglu- tition. 2. Mylo-Hyoideus, (See Fig. 18,) Arises, fleshy, from all the inside of the lower jaw, between the last dens molaris and the middle of the chin, where it joins with its fellow. Inserted into the lower edge of the basis of the os hyoides, and joins with its fellow. Use. To pull the os hyoides forwards, upwards, and to one side. 3. Genio-Hyoideus, Arises, tendinous, from a rough protuberance in the middle of the lower jaw internally, or on the inside of the chin. Inserted into the basis of the os hyoides. Use. To draw this bone forwards to the chin. 4. Genio-Hyo-Glossus. Arises, tendinous, from a rough protuberance in the inside of the middle of the lower jaw; its fibres run like a fan, forwards, upwards, and backwards ; and are Inserted into the whole length of the tongue, and base of the os hyoides, near its cornu. Use. According to the direction of its fibres, to draw the tip of the tongue backwards into the mouth, the middle downwards, and to render its dorsum concave; to draw its root and os hy- oides forwards, and to thrust the tongue out of the mouth. The two muscles at the side are, 288 MUSCLES OF THE NECK. I. Hyo-Glossus, Arises, broad and fleshy, from the base, cornu, and appendix of the os hyoides; the fibres run upwards and outwards; to be Inserted into the side of the tongue, near the stylo-glossus. Use. To pull the tongue inwards and downwards. 2. Lingualis, Arises from the root of the tongue laterally; runs forwards between the hyo-glossus and genio-glossus, to be Inserted into the tip of the tongue, along with part of the sty- lo-glossus. Use. To contract the substance of the tongue, and bring it backwards, and to elevate the point of the tongue. Muscles situated between the Os Hyoides and Trunk. These may be divided into two layers. The first layer consists of two muscles, 1. Sterno-Hyoideus, Arises, thin and fleshy, from the cartilaginous extremity of the first rib, the upper and inner part of the sternum, and from the clavicle where it joins with the sternum. Inserted into the base of the os hyoides. Use. To pull the os hyoides downwards. 2. Omo-Hyoideus, Arises, broad, thin, and fleshy, from the superior costa of the scapula, near the semilunar notch, and from the ligament that runs across it; thence ascending obliquely, it becomes tendinous below the sterno-cleido-mastoid muscle; and, growing fleshy again, is Inserted into the base of the os hyoides, between its cornu and the insertion of the sterno-hyoideus. Use. To pull the os hyoides obliquely downwards. The second layer consists of three muscles. MUSCLES BETWEEN THE JAW AND OS HYOIDES. 289 1. Sterno-Thyroideus, Arises, fleshy, from the whole edge of the uppermost bone of the sternum internally, opposite to the cartilage of the first rib, from which it receives a small part of its origin. Inserted into the surface of the rough line at the external part of the inferior edge of the thyroid cartilage. Use. To draw the larynx downwards. 2. Thyro-Hyoideus, Arises from the rough line opposite to the former. Inserted into part of the basis, and almost all the cornu of the os hyoides. Use, To pull the os hyoides downwards, or the thyroid car- tilage upwards. 3. Crico-Thyroideus, Arises from the side and forepart of the cricoid cartilage, running obliquely upwards. Inserted by two portions; the first, into the lower part of the thyroid cartilage; the second, into its inferior cornu. Use. To pull forwards and depress the thyroid, or to elevate and draw backwards the cricoid cartilage. Muscles situated between the Lower Jaw and Os Hyoides laterally. They are five in number. They proceed from the styloid process of the temporal bone, from which they have half of their names; and two from the pterygoid process of the sphe- noid bone. The three from the styloid process are, 1. Stylo-Glossus, Arises, tendinous and fleshy, from the styloid process, and from a ligament that connects that process to the angle of the lower jaw. vol. i. 25 290 STYLOID MUSCLES. Inserted into the root of the tongue, runs along its side, and is insensibly lost near its apex. Use. To draw the tongue laterally and backwards. 2. Stylo-Hyoideus, Arises, by a round tendon, from the middle and inferior part of the styloid process. Inserted into the os hyoides at the junction of the base and cornu. Use. To pull the os hyoides to one side, and a little upwards. N. B. Its fleshy belly is generally perforated by the tendon of the digastric muscle, on one or both sides. There is often an- other accompanying it, called stylo-hyoideus alter; and has the same origin, insertion, and use. 3. Stylo-Pharyngeus, Arises, fleshy, from the root of the styloid process. Inserted into the side of the pharynx and back part of the thyroid cartilage. Use. To dilate and raise the pharynx and thyroid cartilage upwards. The two from the pterygoid process are, 1. Circumflexus, or Tensor Palati, Arises from the spinous process of the sphenoid bone, behind the foramen ovale, which transmits the third branch of the fifth pair of nerves, from the Eustachian tube, not far from its osse- ous part; it then runs down along the pterygoideus internus, passes over the hook of the internal plate of the pterygoid pro- cess by a round tendon, which soon spreads into a broad mem- brane. Inserted into the velum pendulum palati, and the semilunar edge of the os palati, and extends as far as the suture which joins the two bones. Generally some of its posterior fibres join with the constrictor pharyngis superior, and palato-pharyngeus. Use. To stretch the velum, to draw it downwards, and to one MUSCLES OF THE PALATE. 291 side towards the hook. It has little effect upon the tube, being chiefly connected to its osseous part. 2. Levator Palati, Arises, tendinous and fleshy, from the extremity of the pars petrosa of the temporal bone, where it is perforated by the Eusta- chian tube, and also from the membranous part of the same tube. Inserted into the whole length of the velum pendulum palati, as far as the root of the uvula, and unites with its fellow. Use. To draw the velum upwards and backwards, so as to shut the passage from the fauces into the mouth and nose. Muscles situated about the passage of the Fauces. There are two on each side, and a single one in the middle. The two on each side are, 1. Constrictor Isthmi Faucium, Arises, by a slender beginning, from the side of the tongue, near its root; thence running upwards within the anterior arch, before the amygdala, it is Inserted into the middle of the velum pendulum palati, at the root of the uvula anteriorly, being connected with its fellow, and with the beginning of the palato-pharyngeus. Use. Draws the velum towards the root of the tongue, which it raises at the same time, and with its fellow, contracts the pas- sage between the two arches, by which it shuts the opening into the fauces. 2. Palato-Pharyngeus, Arises, by a broad beginning, from the middle of the velum palati, at the root of the uvula posteriorly, and from the tendinous expansion of the circumflexus palati. The fibres are collected within the posterior arch behind the amygdala, and run back- wards to the top and lateral part of the pharynx, where the fibres are scattered, and mix with those of the stylo-pharyngeus. Inserted into the edge of the upper and back part of the thy. 292 MUSCLES OF THE FAUCES. roid cartilage; some of the fibres being lost between the mem- brane of the pharynx, and the two inferior constrictors. Use. Draws the uvula and velum downwards and backwards; and, at the same time, pulls the thyroid cartilage and pharynx upwards, and shortens it; with the constrictor superior and tongue, it assists in shutting the passage into the nostrils; and, in swallowing, it thrusts the food from the fauces into the pha- rynx. Salpingo-Pharyngeus, (from gaXiriXg, trumpet,) Of Albinus, is composed of a few fibres of this muscle, which Arise from the anterior and lower part of the cartilaginous extremity of the Eustachian tube; and are, Inserted into the inner part of the last-mentioned muscle. Use. To assist the former, and to dilate the mouth of the tube. The one in the middle is the Azygos Uvula, Arises, fleshy, from the extremity of the suture which joins the palate bones, runs down the whole length of the velum and uvula, resembling a small earth-worm, and adhering to the tendons of the circumflexi. Inserted into the apex of the uvula. Use. Raises the uvula upwards and forwards, and shortens it. Muscles situated on the posterior part of the Pharynx. Of these there are three pair: 1. Constrictor Pharyngis Inferior, Arises from the side of the thyroid cartilage, near the attach- ment of the thyroideus and thyro-hyoideus muscles; and from the cricoid cartilage, near the crico-thyroideus. This muscle is the largest of the three; and is Inserted into the white line, where it joins with its fellow; the superior fibres running obliquely upwards, covering nearly one half of the middle constrictor, and terminating in a point; the MUSCLES OF THE GLOTTIS. 293 inferior fibres run more transversely and covers the beginning of the oesophagus. Use. To compress that part of the pharynx which it covers, and to raise it with the larynx a little upwards. 2. Constrictor Pharyngis Medius, Arises from the appendix of the os hyoides, from the cornu of that bone, and from the ligament which connects it to the thyroid cartilage; the fibres of the superior part running obliquely up- wards, and, covering a considerable part of the superior con- strictor, terminate in a point. Inserted into the middle of the cuneiforme process of the os occipitis, before the foramen magnum, and joined to its fellow at a white line in the middle back part of the pharynx. The fibres at the middle part run more transversely than those above or below. Use. To compress that part of the pharynx which it covers. and to draw it and the os hyoides upwards. 3. Constrictor Pharyngis Superior, Arises, above, from the cuneiforme process of the os occipitis, before the foramen magnum, near the holes where the ninth pair of the nerves passes out; lower down, from the pterygoid pro- cess of the sphenoid bone; from the upper and under jaw, near the roots of the last dentes molares; and between the jaws, it is continued with the buccinator muscle; and with some fibres from the root of the tongue, and from the palate. Inserted into a white line in the middle of the pharynx, where it joins with its fellow, and is covered by the constrictor medius. Use. To compress the upper part of the pharynx, and draw it forwards and upwards, Muscles situated about the Glottis. They consist generally of four pair of small muscles, and a single one. 25* 294 MUSCLES OF THE GLOTTIS. 1. Crico-Arytanoideus Posticus, Arises, fleshy, from the back part of the cricoid cartilage; and is Inserted into the posterior part of the base of the arytenoid cartilage. Use. To open the rima glottidis a little, and, by pulling back the arytenoid cartilage, to stretch the ligament so as to make it tense. 2. Crico-Arytanoideus Lateralis, Arises, fleshy, from the cricoid cartilage, laterally, where it is covered by part of the thyroid, and is Inserted into the side of the base of the arytenoid cartilage near the former. Use. To open the rima glottidis, by pulling the ligaments from each other. 3. Thyreo-Arytanoideus, Arises from the under and back part of the middle of the thy- roid cartilage; and, running backwards and a little upwards, along the side of the glottis, is Inserted into the arytenoid cartilage, higher up and farther forwards than the crico-arytaenoideus lateralis. Use. To pull the arytenoid cartilage forwards nearer the mid- dle of the thyroid, and consequently to shorten and relax the ligament of the larynx or glottis vera. 4. Arytanoideus Obliquus, Arises from the base of one arytenoid cartilage ; and, crossing its fellow, is Inserted near the tip of the other arytenoid cartilage. Use. When both act they pull the' arytenoid cartilages to- wards each other. N. B. One of these is very often wanting. The single muscle is, the MUSCLES OF THE GLOTTIS. 295 Arytanoideus Transversus, Arises from the side of one arytenoid cartilage, from near its articulation with the cricoid to near its tip. The fibres run straight across, and are Inserted, in the same manner, into the other arytenoid car- tilage. Use. To shut the rima glottidis, by bringing 'these two carti- lages, with the ligaments, nearer one another. Besides these, there are a few separate muscular fibres on each side; which, from their general direction, are named, 1. Thyreo-Epiglottideus, Arises, by a few pale separated fibres, from the thyroid car- tilage : and is Inserted into the epiglottis laterally. Use. To draw the epiglottis obliquely downwards, or, when both act, directly downwards ; and at the same time, it expands that soft cartilage. 2. Arytano-Epiglottideus, Arises, by a number of small fibres, from the lateral and up- per part of the arytenoid cartilage; and, running along the outer side of the external rima, is Inserted into the epiglottis along with the former. Use. To pull that side of the epiglottis towards the external rima; or, when both act, to pull it close upon the glottis. It is counteracted by the elasticity of the epiglottis. Muscles situated on the anterior Part of the Neck, close to the Vertebra. These consist of one layer, formed by four muscles. 1. Longus Colli, Arises, tendinous and fleshy from the bodies of the three ver- tebrae of the back laterally; and from the transverse process of 296 MUSCLES OF THE SIDE OF THE NECK. the third, fourth, fifth, and sixth vertebra? of the neck, near their roots. Inserted into the forepart of the bodies of all the vertebra? of the neck, by as many small tendons, which are covered with flesh. Use. To bend the neck gradually forwards, and to one side. 2. Rectus Capitis Internus Major, Arises from the anterior points of the transverse process of the third, fourth, fifth, and sixth vertebra? of the neck, by four distinct beginnings. Inserted into the cuneiforme process of the os occipitis, a little before the condyloid process. Use. To bend the head forwards. 3. Rectus Capitis Internus Minor, Arises, fleshy, from the forepart of the body of the first verte- bra of the neck opposite to the superior oblique process. Inserted near the root of the condyloid process of the os oc- cipitis, under, and a little farther outwards, than the former muscle. Use. To bend the head forwards. 4. Rectus Capitis Lateralis, Arises, fleshy, from the anterior part of the point of the trans- verse process of the first vertebra of the neck. Inserted into the os occipitis, opposite to the foramen stylo- mastoideum of the temporal bone. Use. To bend the head a little to one side. Muscles situated on the Anterior Part of the Thorax. These may be divided into two layers. The first layer con- sists of one muscle, named Pectoralis Major, Arises from the cartilaginous extremities of the fifth and sixth ribs, where it always intermixes with the external oblique muscle MUSCLES OF THE THORAX. 297 of the abdomen ; from almost the whole length of the sternum: and from near half of the anterior part of the clavicle; the fibres run towards the axilla in a folding manner. Inserted, by two broad tendons, which cross each other at the upper and inner part of the os humeri, above the insertion of the deltoid muscle, and outer side of the groove for lodging the tendon of the long head of the biceps. Use. To move the arm forwards, and obliquely upwards, to- wards the sternum. The second layer consists of three muscles. 1. Subclavius, Arises, tendinous, from the cartilage that joins the first rib to the sternum. Inserted, after becoming fleshy, into the inferior part of the clavicle, which it occupies from within an inch of the sternum, as far outwards as to its connexion, by ligament, with the cora- coid process of the scapula. Use. To pull the clavicle downwards and forwards. 2. Pectoralis Minor, Arises, tendinous and fleshy, from the upper edge of the third, fourth, and fifth ribs, near where they join with their cartilages. Inserted, tendinous, into the coracoid process of the scapula: but soon grows fleshy and broad. Use. To bring the scapula forwards and downwards, or to raise the ribs upwards. 3. Serratus Magnus, Arises from the nine superior ribs, by an equal number of fleshy digitations, resembling the teeth of a saw. Inserted, fleshy, into the whole base of the scapula internally, between the insertion of the rhomboid and the origin of the sub- scapularis muscle, being folded about the two angles of the scapula. Use. To move the scapula forwards: and, when the scapula is forcibly raised, to draw upwards the ribs. 29s MUSCLES OF THE THORAX. Muscles situated between the Ribs, and within the Thorax. Between the ribs, on each side, there are eleven double rows of muscles, which are, therefore, named intercostals. These de- cussate each other like the strokes of the letter X. 1. Intercostales Externi, Arise from the inferior acute edge of each superior rib, and run obliquely forwards, the whole length from the spine to near the joining of the ribs with their cartilages; from which, to the sternum, there is only a thin membrane covering the internal in- tercostals. Inserted into the upper obtuse edge of each inferior rib, as far back as the spine, into which the posterior portion is fixed. 2. Inter costales Inter ni, Arise in the same manner as the external: but they begin at the sternum, and run obliquely backwards, as far as the angle of the rib; and from that to the spine they are wanting. Inserted in the same manner, as the external. Use. By means of these muscles, the ribs are equally raised upwards, during inspiration. Their fibres being oblique, give them a greater power of bringing the ribs near each other, than could be performed by straight ones. But, by the obliquity of the fibres, they are almost brought contiguous: and as the fixed points of the ribs are before and behind, if the external had been continued forwards to the sternum, and the internal backwards to the spine, it would have hindered their motion, which is greatest in the middle, though the obliquity of the ribs renders it less perceptible; and, instead of raising the fibres fixed to the sternum and spine, would have depressed the ribs. N B. The portions of the external intercostals, which arise from the transverse processes of the vertebra? where the ribs are fixed to them, and other portions that pass over one rib and ter- minate in the next below it, Albinus calls Levatores costarum Ion- giores et breviores. The portions of the internal that pass over one rib, and are ABDOMINAL MUSCLES. 299 inserted into the next below it, are, by Douglas, called Costarum depressores proprii Cowperi. These portions of both rows assist in raising the ribs in the same manner as the rest of the intercostals. The muscles within the thorax form one pair, viz. Triangularis, or Sterno-Costalis, Arises, fleshy, and a little tendinous, from all the length of the cartilago-ensiformis laterally, and from the edge of the lower half of the middle bone of the sternum, from whence its fibres ascend obliquely upwards and outwards. Inserted, generally by three triangular terminations, into the lower edge of the cartilages of the third, fourth, and fifth ribs: near where these join with the ribs. Use. To depress these cartilages, and the extremities of the ribs; and consequently to assist in contracting the cavity of the thorax. This muscle often varies; and is sometimes inserted into the cartilage of the second rib, sometimes into the cartilages of the sixth rib. Muscles situated on the anterior part of the Abdomen. They consist of three broad layers on each side of the belly and, of one layer in front. The three layers are: 1. Obliquus Descendens Externus, Arises, by eight heads, from the lower edges of an equal num- ber of inferior ribs, at a little distance from their cartilages: it always intermixes in a serrated manner, with portions of the serratus major anticus; and generally coheres to the pecto- ralis major, intercostals, and latissimus dorsi; which last covers the edge of a portion of it extended from the last rib to the spine of the ilium. —It interdigitates by its five upper heads with the serratus major anticus, and by the three lower with the latissimus dorsi, where the latter arises from the ribs; a slip from the pec- toralis covers the first or upper head.— 300 ABDOMINAL MUSCLES From these origins the fibres run obliquely downwards and forwards, and terminate in the anterior half of the spine of the ilium, and in a tendinous membrane, whose fibres are continued in the same direction until they meet the fibres of the correspond- ing tendon of the other side, in a line which extends from the en si form cartilage to the os pubis. This line is called linea alba, from its white appearance, which is owing to the connexion of three tendons with each other, without the intervention of muscles, namely, those of the exter- nal and internal oblique, and the transversalis.* On each side of this line, two long narrow muscles (therecti,) are situated between these tendons, and do away the white ap- pearance ; but exterior to these muscles, the tendons are again united, and form a white line on each side, which is called linea semilunaris, from its curved shape. At the lower part of the tendon, near the os pubis, the fibres are so arranged, that they form two bands more firm and dense than the rest of the tendon, which are called columns: these columns are separated from each other; and the vacuity between them is the abdominal ring, or aperture, for the passage of the spermatic chord in males and the round ligament of the uterus in females. This vacuity or aperture has an oval form, which is occasioned by some additional tendinous fibres at the upper part of it, that have a transverse direction. The uppermost of the two columns is continued obliquely downwards, and is inserted into the os pubis of the opposite side, near the symphysis, decussating the fibres of the corresponding column of that side. The lower edge of the tendon of the external oblique is at- tached to the superior anterior spinous process of the ilium, and * According to Meckel, the linea alba performs the same office in the abdomen as the sternum does in the thorax, with this only difference, that it is not formed of bone. The anterior tendons of the broad muscles are attached to it, in the same way that the cartilages of the ribs are articulated with the sternum, and the difference of tissue which exists between it and the sternum is attributable to the general difference of structure between the abdominal and pectoral cavities, the latter being formed almost entirely of osseous parts, whilst the walls of the former are fleshy and tendinous.—p. ABDOMINAL MUSCLES. 301 is there blended with the tendinous fascia, which extends down the thigh. From this process the edge of the tendon is extended, like the chord of a bow, across the concavity formed by the os ilium and os pubis, and is inserted into the pubis near its symphysis. As it proceeds from the spine of the ilium towards the pubis, the edge is folded inwards, so that the membrane is doubled. The portion which is turned inwards is very small at its com- mencement, and continues so for a great part of its extent; but becomes much broader within an inch of its termination. This broad extremity is inserted into the small process of the pubis near the symphysis, and into a ridge which continues backward from the process to the brim of the pelvis, so that the tendinous membrane at this part is doubled; the part which is turned back being about an inch broad at the place of its insertion into the pubis. This doubling forms a partial sheath near the pubis for con- taining the spermatic chord, and supports it for a short distance on the inside of the abdominal ring. The edge formed by the fold of the membrane is called Pou- parVs ligament, and is very firm and strong; owing to the mem- brane being thicker at that place. The real edge, or termination of the portion which is folded inwards, is arranged in the follow- ing manner: the part which is nearest to the spine of the ilium is continued into the cellular membrane, or the fascia, which is between the internal oblique and transversalis muscles, and the iliacus internus. But the edge of that part which is inserted into the ridge of the pubis seems to form a portion of a circular opening, which is occupied in part, but not completely, by the crural vessels. —This edge of Poupart's ligament, inserted into the ridge or crest of the pubis is of a triangular shape, and is called GimbernaVs ligament. It is one of the seats of stricture in crural hernia. The base of the triangle is towards the symphysis pubis.— A portion of the fascia of the thigh, which covers these ves- sels, passes under this portion of the tendon, and. is also inserted into the ridge of the pubis; so that when the intestines protrude vol. i. 26 302 ABDOMINAL MUSCLES. at this aperture, and are strangulated, this portion of the fascia of the thigh must also compress them. —This portion of the fascia lata femoris, is called the crescentic or falciform portion of the fascia lata. The sharp edge at its inner part, by which it is nearly continuous with Gimbernat's ligament, and which is directed downwards and backwards, is called Hay's ligament or the femoral ligament; it is directly above or in front of the crural ring; that space between the crural vein and Gimbernat's liga- ment, included in the sheath of the femoral vessels, and through which the viscera protrude in crural hernia.— The fascia of the thigh is connected with the external edge, or Poupart's ligament, its whole extent: and there is also a fas- cia (fascia superficialis abdominis) which covers the whole ten- don of the external oblique muscle, and passes from it down upon the fascia of the thigh: which also connects the tendon of the external oblique to the fascia of the thigh, and serves to bind it down. From these connexions it is probable that the tendon is in a very different situation before dissection, from what it is afterwards; as the division of these connexions, necessarily made by the dissection, renders it much more loose than it could have been while the parts were undivided. This structure has latterly been called the crural arch.* * The fascia which covers the tendon of the external oblique muscle, and de- scends upon the thigh, can be examined very easily in anasarcous subjects; as in them, the cellular membrane, which is situated between this fascia and the tendon, is somewhat distended by the effused fluid. To prepare Poupart's ligament, or the crural arch, for examination, remove care- fully the cellular membrane from the tendon of the external oblique, and also from the fascia of the thigh, taking care not to remove any part of the fascia which passes under the tendon to be inserted into the os pubis. Then make an incision in the tendon of the external oblique, about three inches above Poupart's ligament, parallel to it, and nearly of the same length ; make a second incision from the up- per end of this, to the junction of the aforesaid ligament with the superior ante- rior spine of the ilium; and a third incision from the lower end to the abdominal ring. Dissect this flap carefully from the internal oblique, until the spermatic chord, the cremaster muscle, and the lower origin of the internal oblique, are perfectly uncovered. After examining the internal surface of the tendon and its insertion at the pubis, the fascia of the thigh may be dissected, so that its con- nexion with the folded edge of the tendon, and its insertion into the pubis, may also be examined. ABDOMINAL MUSCLES. 303 The external oblique muscles compress the abdomen, and therefore contribute to the evacuation of its contents: if the dia- phragm is in a passive state, they force it upwards, by pressing the abdominal viscera against it; and thus assist in producing expiration and its various modifications of coughing, sneezing, &c. They bend the spine forwards, or approach the thorax to the pelvis. When one acts separately, it bends the trunk obliquely to the side on which it is situated. 3. Obliquus Ascendens Internus, Arises from the spine of the ilium the whole length between the posterior and superior anterior spinous process ; from the os sacrum and the three undermost lumbar vertebra?, by a tendon, (fascia lumborum) common to it, to the serratus posticus inferior muscle, and to the latissimus dorsi; from Poupart's ligament, at the middle of which it sends off the beginning of the cremaster muscle; the spermatic chord in the male, or round ligament of the womb in the female, passes under its thin edge, with the exception of a few detached fibres. Inserted into the cartilago-ensiformis, into the cartilages of the seventh, and those of the false ribs; but, at the upper part, it is extremely thin, resembling a cellular membrane, and only becomes fleshy at the cartilage of the tenth rib. Here its tendon divides into two layers ; the anterior layer, with a great portion of the inferior part of the posterior layer, joins the tendon of the external oblique, and runs over the rectus to be inserted into the whole length of the linea alba. The posterior layer joins the tendon of the transversalis muscle as low as half way between the umbilicus and os pubis; but, below this place, only a few fibres of the posterior layer are seen, and the rest of it passes before the rectus muscle, and is inserted into the linea alba ; so that the whole tendon of the external oblique muscle, with the anterior layer of the internal oblique, passes before the rectus muscle; and the whole posterior layer of the internal oblique, together with the whole tendon of the transversalis muscle, ex- 304 ABDOMINAL MUSCLES. cepting at the inferior part, passes behind the rectus, and is in- serted into the linea alba. At its undermost part, it is inserted into the forepart of the os pubis. Fig. 20.* Use. To assist the former; but it bends the trunk in the re- verse direction. 3. Transversalis, Arises, tendinous, but soon becoming fleshy, from the inner or back part of the cartilages of the seven lower ribs, where some of its fibres are continued with those of the diaphragm and the intercostal muscles; by a broad thin tendon, connected to the transverse processes of the last vertebra of the back, and the four superior vertebra? of the loins; fleshy, from the whole spine of the os ilium internally, and from the tendon of the external ob- lique muscle where it intermixes with some fibres of the inter- nal oblique. * Transverse section of abdomen.—a, Division of the tendon of the internal oblique into two layers, forming a sheath in which is contained the rectus muscle. b, External oblique, c, Internal oblique, d, Transversalis. e, Between the last rib and the crista of the ilium, the fibres of the transversalis, arise from a ten- dinous layer, which is trifoliate in its origin, according to Todd. /, The anterior division, arising from the roots of the transverse processes, and covering the quad- ratus lumborum muscle, h, g, The middle, which is weak, attached to the apices of the transverse processes. The posterior is the fascia lumborum. ABDOMINAL MUSCLES. 305 Inserted into the" cartilago-ensiformis, and into the whole length of the linea alba, excepting its lowermost part. Use. To support and compress the abdominal viscera, and it is so particularly well adapted for the latter purpose, that it might be called the proper constrictor of the abdomen. The long muscle in the middle is named Rectus Abdominis, Arises, by two heads, from the ligament of the cartilage which joins the two ossa pubis to each other; runs upwards the whole length of, and parallel to the linea alba, growing broader and thinner as it ascends. Inserted into the cartilages of the three inferior true ribs, and often intermixed with some fibres of the pectoral muscle. It is generally divided by three tendinous intersections: the first is at the umbilicus; the second, where it runs over the car- tilage of the seventh rib; and the third in the middle between these; and there is commonly a half intersection below the um- bilicus. These intersections (linea transversa) seldom penetrate through the whole thickness of the muscle : they adhere firmly to the anterior part of the sheath, but very slightly to the posterior layer.* Use. To compress the forepart, but more particularly the low- er part of the belly; to bend the trunk forwards, or to raise the pelvis. By its tendinous intersection, it is enabled to contract at any of the intermediate spaces; and, by its connexion with the tendons of the other muscles, it is prevented from changing place, and from rising into a prominent form when in action. The short muscle in the middle is named * To obtain an accurate idea of the arrangement of the tendons of the three large pair of abdominal muscles, it will be necessary to raise or separate the exter- nal oblique muscle and tendon from the internal oblique and its tendon, as far as the linea semilunaris, and to separate the internal oblique in the same manner from the transversalis; and then to make an incision in the tendon of the exter- nal oblique parallel to the linea alba, and about an inch and a half from it, so as to bring the whole of the rectus muscle into view. The structure of the sheath which contains the rectus can then be examined. 26 - 306 ABDOMINAL MUSCLES. Pyramidalis, Arises along with the rectus; and running upwards within the same sheath, is Inserted, by an acute termination, near halfway between the os pubis and umbilicus, into the linea alba and inner edge of the rectus muscle. As it is frequently wanting in both sides without any inconve- nience, its Use seems to be, to assist the inferior part of the rectus. Muscles about the male Organs of Generation. The testicles are said to have a thin muscle common to both, and one proper to each. The common muscle is called the Dartos. This consists of muscular fibres blended with the cellular membrane lining the scrotum; and therefore this portion of skin is capable of being corrugated and relaxed in a greater degree than the skin in other places. The muscle proper to each testicle is the Cremaster. Arises from the internal oblique, where a few fibres of that mus- * Cremaster, from Sir A. Cooper's work, a, Rectus muscle. 6, Descending fibres of transversalis. c, The internal oblique, d, Conjoined tendons, c, The descending fibres of oblique. /, Point of insertion into the pubis, g, Ascending fibres, h, One of the reversed arches. The formation of the cremaster, appears to be effected by the testicle in its de- scent, (as Scarpa, Cloquet, Cooper, Velpeaa, and Todd admit,) for before that takes place, the muscle does not exist, according to Cloquet. Prior to the descent, the gu- bernaculum testis occupies the inguinal canal, and is covered by the fibres of the internal oblique, which adhere to it. When the gubernacular is drawn down, these fibres descend with it, forming a series of reversed arches. Fig. 21.* PERINEAL MUSCLES, 307 cle intermix with the transversalis, near the juncture of the os ilium and pubis, over which part it passes, after having pierced the ring of the externus obliquus; and then it descends upon the spermatic chord. Inserted into the tunica vaginalis of the testicle, upon which it spreads, and is insensibly lost.* Use. To suspend and draw up the testicle, and to compress it in the act of coition. The penis has three pair of muscles: 1. Erector Penis, Arises, tendinous and fleshy, from the tuberosity of the os ischium, and runs upwards, embracing the whole crus of the penis. Inserted into the strong tendinous membrane that covers the corpora cavernosa penis, nearly as far up as the union of these bodies. Use. To compress the crura penis, by which the blood is pushed from it into the forepart of the corpora cavernosa ; and the penis is by that means more completely distended. The erectores seem, likewise, to keep the penis in its proper direction. 2. Accelerator Urina seu Ejaculaior Seminis, Arises, fleshy, from the sphincter ani and membranous part of * M. J. Cloquet says, that the scattered fasciculi of this muscle are collected after their distribution on the tunica vaginalis, and run up on the inner side of the chord, to be inserted into the spine of the pubis. He makes the inference from this, that the cremaster is a kind of muscular loop, drawn down by the descent of the testicle. I am satisfied that the muscle in robust subjects, frequently exists, more or less, after the manner in which he speaks of it; but, in the emaciated, it is very indistinct, as regards such an insertion. In the cases where I have seen this insertion into the spine of the pubis, the quantity of muscular fibre has been by no means so great there as at its origin. This observation of M. Cloquet's is in- genious and interesting, but it is well worthy of consideration, that Mr. John Hun- ter's opinion, in his paper on the descent of the testicle, is opposed to it, and on the following grounds: in the young ram, and in several other animals, the cre- master muscle is formed before the testicle descends from the abdomen into the scrotum, being reflected along the gubernaculum testis upwards towards the loins. Mr. Hunter could not, it is true, verify the same observation on the human sub- ject, but he is disposed, from analogy, to believe that something of the kind ex- ists.—H. 308 PERINEAL MUSCLES. the urethra; and tendinous, from the crus, nearly as far for- wards as the beginning of the corpus cavernosum penis: the inferior fibres run more transversely; and the superior descend, in an oblique direction. Inserted into a line in the middle of the bulb where it joins with its fellow, by which the bulb is completely enclosed. Use. To drive the urine or semen forwards; and, by grasp- ing the bulb of the urethra, to push the blood towards the corpus cavernosum and the glans, by which these parts are distended. . 3. Transversus Perinei, Arises from the tough fatty membrane that covers the tube- rosity of the os ischium; from thence it runs transversely in- wards, and is Inserted into the accelerator urina?, and into that part of the sphincter ani which covers the bulb. The place of junction of these muscles is called the perineal point or centre. Use. To dilate the bulb, and draw the perineum and verge of the anus a little outwards and backwards. There is often a fourth muscle, named Transversus Perinei Alter, Arises behind the former, runs more obliquely forwards, and is Inserted into that part of the accelerator urina? which covers the anterior part of the bulb of the urethra. Use. To assist the former. In the Medico-Chirurgical Transactions, James Wilson, Esq. F. R. S. gives the following account of two small muscles of the membranous part of the urethra, viz: Each muscle has a tendon which, at first, is round, but soon becomes flattened as it descends. It is affixed to the back part of the symphysis pubis, about one-eighth of an inch above the lower edge of the cartilaginous arch of the pubes, and nearly at the same distance, below the attachment of the tendon of the bladder: to which, and to the tendon of the corresponding muscle, it is connected by very loose cellular membrane. The tendon descends at first in contact with, and parallel to, its fellow : it soon becomes broader, and sends off fleshy fibres, which also increase in breadth, and, when near the upper surface of the membranous part of the urethra, separate from those of the opposite side, spread themselves on the side of the membranous part of the urethra through its whole extent; then fold MUSCLES OF THE ANUS. 309 themselves under it, and meet in a middle tendinous line with similar fibres of the opposite side. Its action seems to be to draw up the membranous part of the urethra, and compress it against the inside of the cartilaginous arch of the puhes; and also to contract the circle round the membranous portion, so as to di- minish and even close up the passage for the urine.* Muscles of the Anus. The anus has a single muscle, and one pair. The single muscle is Sphincter Ani. Arises from the skin and fat that surrounds the verge of the anus on both sides, nearly as far as the tuber of the os ischium; the fibres are gradually collected into an oval form, and surround the extremity of the rectum. Inserted, before, by a narrow point, into the perineum, acce- leratores urina?, and transversi perinei; behind, by an acute ter- mination, into the extremity of the os coccygis. Use. Shuts the passage through the anus into the rectum; pulls down the bulb of the urethra, by which it assists in eject- ing the urine and semen. —The sphincter ani is always in a contracted state, except at the time of the evacuation of the fa?ces. When the sphincter is in a healthy state, it may be made by an effort of the will to contract more strongly, but it cannot be made to relax. —The irritation induced by the accumulation of faeces in the rectum, causes it at first to contract more strongly, and the con- traction continues till it is overcome, by the increasing effort of the muscular fibres of the rectum, and the action of the dia- phragm and abdominal muscles. It acts also as an antagonist to the levator ani muscle.— N. B. The sphincter internus of Albinus and Douglas, is only * I have frequently dissected for this muscle, and in only two or three cases have been able to satisfy myself of its having an existence distinct from that of the Levator Ani. My friend, Mr. Shaw, who occupies a distinguished rank among the cultivators of Anatomy in London, admits of this muscle, but says there is much difficulty in distinguishing it from the ligament of the urethra, meaning, I presume, its triangular ligament.—h. 310 MUSCLES OF THE ANUS. that part of the circular fibres of the muscular coat of the rectum which surrounds its extremity. Levator Ani, Arises from the os pubis within the pelvis, as far up as the upper edge of the foramen thyroideum, and joining of the os pubis with the os ischium; from the thin tendinous membrane that covers the obturator internus and coccygeus muscle, and from the spinous process of the os ischium: its fibres run down like rays from a circumference to a centre. Inserted into the sphincter ani, acceleratores urina?, and ante- rior part of the two last bones of the os coccygis; surrounds the extremity of the rectum, neck of the bladder, prostate gland, and part of the vesicula? seminales ; so that its fibres behind and below the os coccygis joining it with its fellow, they together very much resemble the shape of a funnel. Use. To draw the rectum upwards after the evacuation of the faeces, and to assist in shutting it; to sustain the contents of the pelvis, and to help in ejecting the semen, urine, and contents of the rectum; and, perhaps by pressing upon the veins, to con- tribute greatly to the erection of the penis. —The muscular funnel, formed by the levator ani muscles of the two sides is antagonised by the action of the sphincter ani, which, by its connexion with the coccyx and perineal centre pre- vents its lower extremity from being drawn upwards. —When the sphincter is inflamed, and a fluid effused among its fibres, as is an occasional occurrence in the bowel complaint of children, the sphincter loses its power, and the levator ani mus- cles, unopposed, retract; and thus by everting the lower margin of the rectum, contribute mainly to the formation of prolapsus ani.— Muscles of the Female Organs of Generation, The clitoris has one pair. Erector Clitoridis, Arises from the crus of the os ischium internally, and in its ascent covers the crus of the clitoris as far up as the os pubis. Inserted into the upper part of the crus and body of the clitoris. PERINEAL MUSCLES OF THE FEMALE. g j j Use. Draws the clitoris dowrnwards and backwards; and may serve to make the body of the clitoris more tense by squeezing the blood into it from its crus. The vagina has one pair. Sphincter Vagina, Arises from the sphincter ani, and from the posterior side of the vagina, near the perineum ; from thence it runs up the side of the vagina, near its external orifice, opposite to the nympha? and covers the corpus cavernosum vagina?. Inserted into the crus and body or union of the crura clito- ridis. Use. Contracts the mouth of the vagina, and compresses its corpus cavernosum. Transversus Perinei, Arises, as in the male, from the fatty cellular membrane which covers the tuberosity of the os ischium. Inserted into the upper part of the sphincter ani, and into a white hardish tough substance in the perineum, between the lower part of the pudendum and anus. Use. To sustain and keep the perineum in its proper place. The anus, as in the male, has a single muscle, and one pair. Sphincter Ani. Arises, as in the male, from the skin and fat surrounding the extremity of the rectum. Inserted, above, in the white tough substance of the perineum (perineal centre); and below, into the point of the os coccygis. Use. To shut the passage into the rectum; and, by pulling down the perineum, to assist in contracting the mouth of the vagina. Levator Ani, Arises, as in the male, within the pelvis, and descends along the inferior part of the vagina and rectum. Inserted into the perineum, sphincter ani extremity of the va- gina and rectum. 312 MUSCLES OF THE ABDOMINAL CAVITY. Use. To raise the extremity of the rectum upwards, to con- tract the inferior part of the rectum, and to assist in contracting and supporting the vagina; and, perhaps, by pressing on the veins, to contribute to the distention of the cells of the clitoris and corpus cavernosum of the vagina. Muscles situated within the Cavity of the Abdomen. These consist of a single muscle, and four pair. Diaphragma. This broad thin muscle, which makes a complete septum between the thorax and abdomen, is concave below and convex above ; the middle of it on each side reaching as high with- in the thorax of the skele- ton as the fourth rib : it is commonly divided into two portions. 1. The superior or, Greater Muscle of the Dia- phragm, Arises, by distinct fleshy fibres, from the cartilago-ensiformis, from the cartilages of the seventh, and of all the inferior ribs on both sides. The fibres from the cartilago.-ensiformis, and from the seventh and eighth * Thorax of a male.—On the left side the muscles are removed; on the right they are left in situ, a, a, Cervical and lumbar parts of the spinal column, the dorsal portion is concealed by the sternum, b. c, c, The true ribs. c\ The false ribs, d, The clavicle, c, Intercostal muscles. /, Last false rib, concealed by the origin of a part of the greater muscle of the diaphragm, g, The arch formed in the interior of the thorax by the diaphragm: the position of this arch on the right side, is indicated by a dotted line, h, Columns, or crura of the lesser mus- cles of the diaphragm, arising from the lumbar vertebrae, i, Levatores costarum, longiores, and breviores. Fig. 22.* a i MUSCLES OF THE ABDOMINAL CAVITY. 313 ribs, run obliquely upwards and backwards ; from the ninth and tenth, transversely inwards and upwards, and from the eleventh and twelfth, obliquely upwards. From these different origins the fibres run, like radii from the circumference to the centre of a circle; and are Inserted into a cordiform tendon, of a considerable breadth, which is situated in the middle of the diaphragm, and in which, therefore, the fibres from opposite sides are interlaced. To- wards the right side the tendon is perforated, by a triangular hole, for the passage of the vena cava inferior; and to the upper convex part of it the pericardium and mediastinum are con- nected. The inferior, lesser muscle, or Appendix of the Diaphragm, Arises from the second, third and fourth lumbar vertebra?, by eight heads, of which, two in the middle, commonly called its crura, are the longest, and begin tendinous. Between the crura, the aorta and thoracic duct pass; and on the outside of these, the great sympathetic nerves and branches of the vena azygos perforate the shorter heads. The muscular fibres run obliquely upwards and forwards, and form in the middle two fleshy columns, which decussate and leave an oval space be- tween them for the passage of the oesophagus and eighth pair of nerves. Inserted, by strong fleshy fibres, into the posterior part of the middle tendon. Use. The diaphragm is the principal agent in respiration, particularly in inspiration: for when it is in action, the fibres, from their different attachments, endeavour to bring themselves into a plain towards the middle tendon, by which the cavity of the tho- rax is enlarged, particularly at the sides, where the lungs are chiefly situated; and as the lungs must always be contiguous to the inside of the thorax and upper side of the diaphragm, the air rushes into them, in order to fill up the increased space. This muscle is assisted by the two rows of intercostals, which elevate the ribs, and the cavity of the thorax is more enlarged. In time vol. i. 27 314 MUSCLES OF THE ABDOMINAL CAVITY. of violent exercise, or whatever cause drives the blood with un- usual celerity towards the lungs, the pectoral muscles, the ser- rati antici majores, the serrati postici superiores, and scaleni muscles, are brought into action. These effect the lateral dila- tation of the thorax. And in laborious inspiration, the muscles which arise from the upper part of the thorax, when the parts into which they are inserted are fixed, likewise assist. In expi- ration, the diaphragm is relaxed and pushed up by the pressure of the abdominal muscles upon the viscera of the abdomen ; and at the same time that they press it upwards, they also, to- gether with the sterno-costales and serrati postici inferiores, pull down the ribs, and are assisted, in a powerful manner, by the elasticity of the cartilages that join the ribs to the sternum; by which the cavity of the thorax is diminished, and the air sud- denly pushed out of the lungs : and, in laborious expiration, the quadrati lumborum, sacro-lumbales, and longissimi dorsi, concur in pulling down the ribs. —The diaphragm, contributes the principal share to the dilatation of the chest during inspiration. When relaxed, the diaphragm is arched, and the top of the arch is nearly on a horizontal level with the anterior portion of the fourth rib, as seen in Fig. 22, page 312. When contracted, the arch is flattened, (though the cordiform tendon itself, is but little depress- ed,) and the capacity of the thorax is increased, at the same time that the abdominal viscera are pressed downwards, so as to pro- duce the protrusion of the abdomen observed during inspiration. The abdominal muscles and the diaphragm, usually antagonise each other, by contracting alternately. Occasionally they con- tract in unison, as in straining during defecation, parturition, &c, and compress the viscera and their contents, between the two planes which they form, with such force, as to give rise at times to hernial protrusions. —In natural tranquil inspiration, the dilatation of the chest is ef- fected almost wholly by the diaphragm.— The four pair are, 1. Quadratus Lumborum, Arises, somewhat broad, tendinous and fleshy, from the poste- rior part of the spine of the os ilium. MUSCLES OF THE ABDOMINAL CAVITY. 315 Inserted into the transverse processes of all the vertebra? of the loins, into the last rib near the spine, and by a small tendon into the side of the last vertebra of the back. Use. To move the loins to one side, pull down the last rib, and, when both act, to bend the loins forwards. 2. Psoas Parvus, Arises, fleshy, from the sides of the two upper vertebra? of the loins, and sends off a small long tendon, which ends thin and flat, and is Inserted into the brim of the pelvis, at the junction of the os ilium and pubis. Use. To assist the psoas magnus in bending the loins for- wards ; and, in certain positions, to assist in raising the pelvis. N. B. This muscle is very often wanting. 3. Psoas Magnus, Arises, fleshy, from the side of the body and transverse pro- cess of the last vertebra of the back; and, in the same manner, from those of the loins, by as many distinct slips. —At its su- perior portion, this muscle is covered by a thin fibrous expan- sion which is attached on the one hand to the points of the transverse processes, and on the other to the bodies of the upper lumbar vertebra?. This expansion, the arcus interior of Senac and Haller, separates the psoas from the diaphragm. On the outer side of this is another aponeurotic arch, called ligamentum arcu- atum; it passes from the outer extremity of the former, to the inferior margin of the last rib, embracing in its curve below, the quadratus lumborum muscle. Both these arches give origin on their upper margin to fibres of the lesser muscle of the diaphragm, and serve to cut off more effectually any communication between the thoracic and abdominal cavities.— Inserted, tendinous, into the trochanter minor of the os femo- ris; and fleshy into that bone, a little below the same tro- chanter. Use. To bend the thigh forwards; or, when the inferior ex- tremity is fixed, to assist in bending the body. 316 MUSCLES WITHIN THE PELVIS. 4. Iliacus Internus, Arises, fleshy, from the transverse process of the last vertebra of the loins, from all the inner lip of the spine of the os ilium, from the edge of that bone between its anterior spinous process and the acetabulum, and from most of the hollow part of the ilium. It joins with the psoas magnus, over the pubis, where it begins to become tendinous; and is Inserted along with it on the trochanter minor. Use. To assist the psoas in bending the thigh, and to bring it directly forwards. N. B. The insertion of the two last muscles should not be traced till the muscles of the thigh are dissected. Muscles situated within the Pelvis. Of these there are two pair. 1. Obturator Internus, Arises from more than one half of the internal circumference of the foramen thyroideum, formed by the os pubis and ischium, and from the upper part of the plane of the ischium, where it joins the ileum. Its inner face is covered by a portion of the levator ani; and appears to be divided into a number of fasciculi, which unite, and form a roundish tendon, that passes out of the pelvis, between the posterior sacro-ischiatic ligament and tuberosity of the os ischium; where it passes over the capsular ligament of the thigh bone, it is enclosed as in a sheath, by the gemini mus- cles. Inserted, by a round tendon, into the large pit at the root of the trochanter major. Use. To roll the os femoris obliquely outwards. N. B. The insertion of this muscle should not be traced until the muscles of the thigh, to which it belongs, are dissected. 2. Coccygeus. Arises, tendinous and fleshy, from the spinous process of the os ischium, and covers the inside of the posterior sacro-ischiatic MUSCLES OF THE BACK. 317 ligament; from this narrow beginning, it gradually increases to form a thin fleshy belly, interspersed with tendinous fibres. Inserted into the extremity of the os sacrum, and nearly the whole length of the os coccygis laterally. Use. To support and move the os coccygis forwards, and to tie it more firmly to the sacrum. Muscles situated on the Posterior Part of the Trunk. These may be divided into four layers and a single pair. The first layer consists of two muscles, which cover almost the whole posterior part of the trunk. Trapezius seu Cucullaris, Arises, by a strong round tendon, from the lower part of the protuberance in the middle of the os occipitis behind; and, by a thin membranous tendon, which covers part of the splenius and complexus muscles from the rough curved line that extends from the protuberance towards the mastoid process of the tem- poral bone; runs down along the nape of the neck, where it seems to arise from its fellow, and covers the spinous processes of the superior vertebra? of the neck ; but rises from the spinous processes of the two inferior, and from the spinous processes,of all the vertebra? of the back: adhering tendinous, to its fellow, the whole length of its origin. Inserted, fleshy, into the posterior half of the clavicle; tendin- ous and fleshy, into the acromion, and into almost all the spine of the scapula. Use. Moves the scapula according to the three different direc- tions of its fibres: for the upper descending fibres draw it ob- liquely upwards; the middle transverse straight fibres draw if directly backwards; and the inferior ascending fibres draw it obliquely downwards and backwards. N. B. Where it is inseparably united to its fellow in the nape of the neck, it is named Ligamentum Nucha, or Colli. —The two - trapezii taken together, have some resemblance to the monk's cowl hanging over the neck, hence the name of cucullares given to them.— 27* 318 MUSCLES OF THE BACK. 2. Latissimus Dorsi, Arises, by a broad thin tendon, from the posterior part of the spine of the os ilium, from all the spinous processes of the os sacrum and vertebra? of the loins, and from the seven inferior ones of the vertebra? of the back; also tendinous and fleshy, from the extremities of the three or four inferior ribs, a little beyond their cartilages, by as many distinct slips. The inferior fibres ascend obliquely, and the superior run transversely, over the inferior angle of the scapula, towards the axilla where they are collected, twisted, and folded. —Sometimes a few additional fibres of the muscle, arise from the inferior angle of the sca- pula.— Inserted, by a strong thin tendon, into the inner edge of the groove for lodging the tendon of the long head of the biceps. Use. To pull the arm backwards and downwards, and to roll the os humeri. N. B. The insertion of this muscle should not be prosecuted till the muscles of the os humeri, to which it belongs, are dis- sected. The second layer consists of three pair, two on the back, and one on the neck. On the back: 1. Serratus Posticus Inferior, Arises, by a broad thin tendon, in common with that of the latissimus dorsi, from the spinal process of the two inferior ver- tebra? of the back, and from the three superior vertebra? of the loins. Inserted into the lower edge of the four inferior ribs, at a lit- tle distance from their cartilages, by as many distinct fleshy slips. Use. To depress the ribs into which it is inserted. 2. Rhomboideus. This muscle is divided into two portions. 1. Rhomboideus major, arises, tendinous, from the spinous pro- cesses of the five superior vertebra? of the back. Inserted into all the basis of the scapula below its spine. MUSCLES OF THE BACK. oig Use. To draw the scapula obliquely upwards, and directly in- wards. 2. Rhomboideus minor, arises, tendinous, from the spinous pro- cesses of the three inferior vertebra? of the neck, and from the ligamentum nucha?. Inserted into the base of the scapula, opposite to its spine. Use. To assist the former. On the neck: 3. Splenius, Arises, tendinous, from the four superior spinous processes of the vertebra? of the back: tendinous and fleshy, from the five inferior of the neck, and adheres firmly to the ligamentum nucha?. At the third vertebra of the neck, the splenii recede from each other, so that part of the complexus muscle is seen. Inserted, by as many tendons, into the five superior transverse processes of the vertebra? of the neck; and tendinous and fleshy, into the superior part of the mastoid process, and into the os oc- cipitis, where it joins with the root of that process. Use. To bring the head and upper vertebra? of the neck back- wards laterally: and, when both act, to pull the head directly backwards. N. B. Albinus divides this muscle into two, viz. That por- tion which arises from the five inferior spinous processes of the neck, and is inserted into the mastoid process and os occipitis, he calls splenius capitis; and that portion which arises from the third and fourth of the back, and is inserted into the five superior transverse processes of the neck, is called by him splenius colli. The single pair, Serratus Superior Posticus, Arises, by a broad thin tendon, from the spinous processes of the three last vertebra? of the neck, and the two uppermost of the back. Inserted into the second, third, fourth, and fifth ribs, by as many fleshy slips. Use. To elevate the ribs, and dilate the thorax. The third layer consists of three pair on the back, and three on the neck. Those on the back are, 320 MUSCLES OF THE BACK. 1. Spinalis Dorsi, Arises from the spinous processes of the two uppermost verte- bra? of the loins, and the three inferior of the back, by as many tendons. Inserted into the spinous processes of the nine uppermost ver- tebra? of the back, except the first, by as many tendons. Use. To erect and fix the vertebra?, and to assist in raising the spine. 2. Longissimus Dorsi, Arises, tendinous without, and fleshy within, from the side, and all the spinous processes of the os sacrum ; from the posterior spine of the os ilium; from all the spinous processes, and from the roots of the transverse processes of the vertebra? of the loins. Inserted into all the transverse processes of the vertebra? of the back, chiefly by small double tendons; also, by a tendinous and fleshy slip, into the lower edge of all the ribs, except the two inferior, at a little distance from their'tubercles. Use. To extend the vertebra?, and to raise and keep the trunk of the body erect. N B. From the upper part of this muscle, there runs up a round fleshy portion which joins with the cervicalis descendens. 3. Sacro-Lumbalis, Arises, in common with the longissimus dorsi. Inserted into all the ribs, where they begin to be curved for- wards, by as many long and thin tendons; and, From the upper part of the six or eight lower ribs, arise as many bundles of thin fleshy fibres, which soon terminate in the inner side of this muscle, and are named musculi ad sacro-lum- balem accessorii. Use. To pull the ribs down, and assist in erecting the trunk of the body. N. B. There is a fleshy slip which runs from the upper part of this muscle into the fourth, fifth, and sixth transverse pro- cesses of the vertebra? of the neck, by three distinct tendons: it is named cervicalis descendens; and its use is to turn the neck obliquely backwards, and to one side. MUSCLES OF THE BACK AND NECK. 321 On the neck are, 1. Complexus, Arises from the transverse processes of the seven superior vertebra? of the back, and four inferior of the neck, by as many distinct tendinous origins ; in its ascent, it receives a fleshy slip from the spinous process of the first vertebra of the back. From these different origins it runs upwards, and is every where inter- mixed with tendinous fibres. Inserted, tendinous and fleshy, into the inferior edge of the protuberance in the middle of the os occipitis, and into a part of the curved line that runs forwards from that protuberance. Use. To draw the head backwards, and to one side, and when both act, to draw the head directly backwards. N. B. The long portion of this muscle that is situated next the spinous processes, lies more loose, and has a roundish ten- don in the middle of it: for which reason Albinus calls it biven- ter cervicis. 2. Trachelo-Mastoideus, Arises from the transverse processes of the three uppermost vertebra? of the back, and from the five lowermost of the neck, (where it is connected to the transversalis cervicis,) by as many thin tendons, which unite into a belly, and run up under the splenius. Inserted into the middle of the posterior side of the mastoid process, by a thin tendon. Use. To assist the complexus; but it pulls the head more to one side. 3. Levator Scapula, Arises, tendinous and fleshy, from the transverse processes of the five superior vertebra? of the neck, by as many distinct slips, which soon unite to form a muscle that runs downwards and outwards. Inserted, fleshy, into the superior angle of the scapula. Use. To pull the scapula upwards and a little forwards. The fourth layer consists of two pair on the back, two on the posterior part of the neck, four small pair situated immediately 322 MUSCLES OF THE BACK AND NECK. below the posterior part of the occiput, and three on the side of the neck. On the back are, 1. Semi-Spinalis Dorsi, Arises, from the transverse processes of the seventh, eighth, ninth, and tenth vertebra? of the back, by as many distinct tendons, which soon grow fleshy, and then become tendinous; and are Inserted into the spinous processes of all the vertebra? of the back above the eighth, and into the two lowermost of the neck, by as many tendons. Use. To extend the spine obliquely backwards. 2. Multifidus Spina, Arises from the side and spinous processes of the os sacrum, and from the posterior part of the os ilium, where it joins with the sacrum; from all the oblique and transverse processes of the vertebra? of the loins; from all the transverse processes of the vertebra? of the back, and from those of the neck, except the three first, by as many distinct tendons, which soon grow fleshy, run in an oblique direction; and are Inserted, by distinct tendons, into all the spinous processes of the vertebra? of the loins, of the back, and of the neck, except the first. Use. When the different portions of this muscle act on one side, they extend the back obliquely, or move it laterally; but if they act together on both sides, they extend the vertebra? backwards. On the posterior part of the neck are, 1. Semi-Spinalis Colli, Arises from the transverse processes of the uppermost six vertebrae of the back, by as many distinct tendons ascending obliquely under the complexus. Inserted into the spinous processes of all the vertebra? of the neck, except the first and the last. Use. To extend the neck obliquely backwards. 2. Transversalis Colli, Arises from the transverse processes of the five uppermost MUSCLES OF THE BACK AND NECK. 323 vertebra? of the back, by as many tendinous and fleshy origins; runs between the trachelo mastoideus, and splenius colli and cervicalis descendens. Inserted into the transverse processes of all the cervical verte- bra?, except the first and the last. Use. To turn the neck obliquely backwards, and a little to one side. Below the posterior part of the occiput are. 1. Rectus Capitis Posticus Major, Arises, fleshy, from the external part of the spinous process of the second vertebra of the neck, and grows broader in its as- cent, which is not straight, but obliquely outwards. Inserted, tendinous and fleshy, into the os occipitis, near the rectus capitis lateralis, and the insertion of the obliquus capitis superior. Use. To pull the head backwards, and to assist a little in its rotation. 2. Rectus Capitis Posticus Minor, Arises, by a narrow beginning, close to its fellow, from a little protuberance in the middle of the back part of the first vertebra of the neck, its outer edge being covered by the rectus major. Inserted, somewhat broad, into the sides of a dimple in the os occipitis, near its foramen magnum. Use. To assist the rectus major in moving the head backwards. 3. Obliquus Capitis Superior, Arises from the transverse process of the first vertebra of the neck. Inserted, tendinous and fleshy, into the os occipitis behind the back part of the mastoid portion of the temporal bone, and under the insertion of the complexus muscle. Use. To draw the head backwards. 4. Obliquus Capitis Inferior, Arises, fleshy, from the spinous process of the second vertebra of the neck, its whole length; and, forming a thick fleshy belly, is 324 MUSCLES OF THE BACK AND NECK. Inserted into the transverse process of the first vertebra of the neck. Use. To give a rotary motion to the head. On the side of the neck are, 1. Scalenus Anticus, Arises from the fourth, fifth, and sixth transverse processes of the first vertebra of the neck, by as many tendons. Inserted, tendinous and fleshy, into the upper side of the first rib near its cartilage. 2. Scalenus Medius, Arises from all the transverse processes of the vertebra? of the neck, by as many strong tendons; the nerves to the superior ex- tremity pass between it and the former. Inserted into the upper and outer part of the first rib, from its root, to within the distance of an inch from its cartilage. 3. Scalenus Posticus, Arises from the fifth and sixth transverse processes of the vertebra? of the neck. Inserted, into the upper edge of the second rib, not far from the spine. Use of the three scaleni: to bend the neck to one side; or, when the neck is fixed, to elevate the ribs, and to dilate the thorax. There are a number of small muscles situated between the spinous and transverse processes of contiguous vertebra?; which are accordingly named, 1. Interspinales Colli. The space between the spinous processes of the vertebra? of the neck, most of which are bifurcated, is filled up with fleshy portions; each of which Arises, double, from the spinous processes of the cervical ver- tebra? below, and ascends to be Inserted, in the same manner, into the spinous process of the vertebra? above. They are five in number. MUSCLES OF THE SUPERIOR EXTREMITIES. 325 Use. To draw these processes nearer to each other. 2. Intertransversales Colli. They begin from the transverse process of the first vertebra of the back, and fill up the spaces between the transverse pro- cesses of the vertebra? of the neck, which are likewise bifurcated; and, consequently, there are six distinct double muscles, which Arise from the inferior transverse process of each vertebra of the neck, and first of the back, and are Inserted into the superior transverse processes. Use. To draw these processes towards each other, and turn the neck a little to one side, Interspinals Dorsi et Lumborum, and the Intertransversales Dorsi, Are rather small tendons than muscles, serving to connect the spinal and transverse processes. Intertransversales Lumborum, Are four distinct small bundles of flesh, which fill up the space between the transverse processes of the vertebra? of the loins, and serve to draw them towards each other. MUSCLES OF THE SUPERIOR EXTREMITIES. These may be divided into the muscles that are situated on the scapula, on the os humeri, on the cubit or forearm, and on the hand. Muscles situated on the Scapula. These are called muscles of the os humeri; and are three behind, one along its inferior costa, two before, and one beneath it. Behind are, 1. Supra-spinatus, Arises, fleshy, from all that part of the base of the scapula that is above its spine; also from the spine and superior costa; passes vol. 1. 28 326 MUSCLES SITUATED ON THE SCAPULA. under the acromion, and adheres to the capsular ligament of the os humeri. Inserted, tendinous, into that part of the large protuberance on the head of the os humeri, that is next the groove for lodging the tendon of the long head of the biceps. Use. To raise the arm upwards; and, at the same time to pull the capsular ligament from between the bones, that it may not be pinched. 2. Infraspinatus, Arises, fleshy, from all that part of the base of the scapula that is between its spine and inferior angle; and from the spine as far as the cervix of the scapula. The fibres ascend and descend ob- liquely towards a tendon in the middle of the muscle, which runs forwards, and adheres to the capsular ligament. Inserted, by a thick and short tendon, into the upper and middle part of the large protuberance on the head of the os humeri. Use. To roll the humerus outwards: to assist in raising, and in supporting it when raised; and to pull the ligament from between the bones. N. B. These two muscles are covered with a tendinous mem- brane, from which a number of their fleshy fibres arise. It serves besides to strengthen their actions, and keeps them from swelling too much outwardly when in action. 3. Teres Minor, Arises, fleshy, from all the round edge of the inferior costa of the scapula, and runs forwards along the inferior edge of the infra-spinatus muscle, and adheres to the ligament. Inserted, tendinous, into the back part of the large protuberance on the head of the os humeri, a little behind and below the ter- mination of the last named muscle. Use. To roll the humerus outwards, to draw the humerus back- wards; and to prevent the ligament from being pinched between the bones. Along the inferior costa of the scapula is, MUSCLES SITUATED ON THE SCAPULA. 327 Teres Major, Arises, fleshy, from the inferior angle of the scapula, and from all that portion of its inferior costa that is rough and thicker than the rest; its fleshy fibres are continued over part of the infra-spinatus muscle, to which they firmly adhere. Inserted, by a broad, short, and thin tendon, into the ridge at the inner side of the groove for lodging the tendon of the long head of the biceps, along with the latissimus dorsi. Use. To roll the humerus inwards, and to draw it backwards and downwards. The two before the scapula are, 1. Deltoides, Arises, fleshy, from all the posterior part of the clavicle that the pectoralis major does not occupy; tendinous and fleshy, from the acromion, and lower margin of almost the whole spine of the scapula opposite to the insertion of the cucullaris muscle: from the origins it runs in three different directions, i. e. from the clavicle outwards and downwards; from the spine of the scapula outwards, forwards, and downwards; and from the acromion, straight downwards; and is composed of a number of fasciculi, which form a strong fleshy muscle that covers the anterior part of the joint of the os humeri. Inserted, tendinous into a rough protuberance in the outer side of the os humeri, near its middle, where the fibres of this muscle intermix with some part of the brachialis externus. Use. To pull the arm directly outwards and upwards, and a little forwards or backwards, according to the different direc- tions of its fibres. 2. Coraco-Brachialis, Arises, tendinous and fleshy, from the forepart of the coracoid process of the scapula; adhering in its descent, to the short head of the biceps. Inserted, tendinous and fleshy, about the middle of the internal part of the os humeri, near the origin of the third head of the 328 MUSCLES SITUATED ON THE OS HUMERI triceps, called brachialis externus, where it sends down a thin tendinous expansion to the internal condyle of the os humeri. Use. To raise the arm upwards and forwards. N B. There passes a nerve through this muscle, called mus- culo cutaneus. The one beneath the scapula is, Subscapularis, Arises, fleshy, from all the base of the scapula, internally, and from its superior and inferior costa?, being composed of a num- ber of tendinous and fleshy fasciculi, which make prints on the bone; they all join together, fill up the hollow of the scapula, and pass over the joint, adhering to the capsular ligament. Inserted, tendinous, into the upper part of the internal protu- berance at the head of the os humeri. Use. To roll the humerus inwards, and to draw it to the side of the body; and to prevent the capsular ligament from being pinched. Muscles situated on the Os Humeri. These are called Muscles of the Cubit or Forearm. They consist of two before, and two behind. Before are, 1. Biceps Flexor Cubiti, Arises, by two heads. The first and outermost called longus, begins tendinous from the upper edge of the glenoid cavity of the scapula, passes over the head of the os humeri within the joint; and, in its descent without the joint, is enclosed in a groove near the head of the os humeri, by a membranous liga- ment that proceeds from the capsular ligament and adjacent ten- dons. The second or innermost head, called brevis, arises ten- dinous and fleshy, from the coracoid process of the scapula, in common with the coraco-brachialis muscle. A little below the middle of the forepart of the os humeri, these heads unite. MUSCLES SITUATED ON THE OS HUMERI. 329 Inserted, by a strong roundish tendon, into the tubercle on the upper end of the radius internally. Use. To turn the hand supine, and to bend the forearm. N. B. At the bending of the elbow, where it begins to grow tendinous, it sends off an aponeurosis which covers all the mus- cles on the inside of the forearm, and joins with another tendin- ous membrane, which is sent off from the triceps extensor cubiti, and covers all the muscles on the outside of the forearm, and a number of the fibres, from opposite sides, decussate each other. It serves to strengthen the muscles, by keeping them from swell- ing too much outwardly, when in action; and a number of their fleshy fibres take their origin from it. 2. Brachialis Internus, Arises, fleshy, from the middle of the os humeri, at each side of the insertion of the deltoid muscle, covering all the inferior and forepart of this bone, runs over the joint and adheres firmly to the ligament. Inserted, by a strong tendon, into the coronoid process of the ulna. Use. To bend the forearm, and to prevent the capsular liga- ment of the joint from being pinched. Behind, are 1. Triceps Extensor Cubiti, Arises, by three heads; the first called longus, somewhat broad and tendinous, from the inferior costa of the scapula, near its cervix. The second head, called brevis, arises by an acute, ten- dinous, and fleshy beginning, from the back part of the os hu- meri, a little below its head, outwardly. The third, called bra- chialis externus, arises by an acute beginning, from the back part of the os humeri. These three heads unite lower than the insertion of the teres major, and cover the whole posterior part of the humerus, from which they receive addition in their de- scent. Inserted into the upper and external part of the process of the 28* 330 MUSCLES ON THE ANTERIOR PART OF THE FOREARM. ulna, called olecranon, and partly into the condyles of the os hu- meri, adhering firmly to the ligament. Use. To extend the forearm. 2. Anconeus, Arises, tendinous, from the posterior part of the external con- dyle of the os humeri; it soon grows fleshy, and is continued from the third head of the triceps. Inserted, fleshy, and thin into a ridge on the outer and poste- rior edge of the ulna, being continued some way before the ole- cranon, and covered with a tendinous membrane. Use. To assist in extending the forearm. Muscles situated on the Forearm. These may be divided into three classes, viz. 1. The muscles which bend and extend the wrist, and of course the whole hand. 2. Those which bend and extend the fingers exclusively. 3. Those which act on the radius so as to roll it backwards and forwards on the ulna; which are called supinators and pronators. The flexors both of the wrist and fingers, and the pronators, lie on the front of the forearm. The extensors and the supinators on the back. The flexors generally originate from the internal condyle of the os hu- meri, and the parts adjacent to it; the extensors from the external con- dyle of the same bone, and the parts which are near it. In the following description they are arranged in the order in which they occur in the dissection of the arm; beginning with those which origi- nate with the internal condyle, without regard to their particular func- tions. Muscles on the anterior part of the Forearm. 1. Palmaris Longus, Arises, tendinous, from the internal condyle of the os humeri, soon grows fleshy, and, after a short progress, sends off a long slender tendon. Inserted into the ligamentum carpi annulare, and into a ten- dinous membrane that is expanded on the palm of the hand, named aponeurosis palmaris; which, above, begins at the trans- MUSCLES ON THE ANTERIOR PART OF THE FOREARM. 331 verse or annular ligament of the wrist, and, below, is fixed to the roots of the fingers. Use. To bend the hand, and to stretch the membrane that is expanded on the palm. N B. This muscle is sometimes wanting, but the aponeurosis palmaris is always to be found. 2. Pronator Radii Teres, Arises, fleshy, from the internal condyle of the os humeri, and tendinous from the coronoid process of the ulna. Inserted, thin, tendinous, and fleshy, into the middle of the posterior part of the radius. Use. To roll the radius, together with the hand, inwards. 3. Flexor Carpi Radialis, Arises, tendinous and fleshy, from the internal condyle of the os humeri, and from the anterior part of the upper end of the ulna, where it firmly adheres to the pronator radii teres. Inserted, by a flat tendon, into the fore and upper part of the metacarpal bone that sustains the forefinger, after running through a fossa in the os trapezium. Use. To bend the hand, and to assist in its pronation. 4. Flexor Carpi Ulnaris, Arises, tendinous, from the internal condyle of the os humeri. It has, likewise, a small fleshy beginning from the outer side of the olecranon, between which, and the origin from the condyle, there is a space left, through which the ulnar nerve passes to the forearm; and a number of its fleshy fibres arise from the tendi- nous membrane that covers the forearm. Inserted, by a short strong tendon, into the os pisiforme. At a little distance from its insertion, a small ligament is sent off to the metacarpal bone that sustains the little finger. Use. To assist the former in bending the arm. 5. Flexor Sublimis Perforatus, Arises, tendinous and fleshy, from the internal condyle of the 332 MUSCLES ON THE ANTERIOR PART OF THE FOREARM os humeri; tendinous from the coronoid process of the ulna, near the edge of the cavity that receives the head of the radius; fleshy from the tubercle of the radius; and membranous and fleshy from the middle of the forepart of the radius, where the flexor pollicis longus arises. Its fleshy belly sends off four round tendons before it passes under the ligament of the wrist. Inserted into the anterior and upper part of the second bone of each finger, being near the extremity of the first bone, di- vided for the passage of the perforans. Use. To bend the second joint or phalanx of the fingers. 6. Flexor Profundus Perforans, Arises, fleshy, from the external side, and upper part of the ulna, for some way downwards, and from a large share of the interosseous ligament. It splits into four tendons, a little be- fore it passes under the ligamentum carpi annulare; and these pass through the slits in the tendons of the flexor sublimis. Inserted into the fore and upper part of the third or last bone of all the four fingers. Use. To bend the last joint of the fingers. 7. Flexor Longus Pollicis Manus, Arises, by an acute fleshy beginning, from the upper part of the radius, immediately below its tubercle, and is continued down for some space on the forepart of this bone. It has likewise generally another origin from the internal condyle of the os hu- meri, which forms a distinct fleshy slip, that terminates near the upper part of the origin from the radius. Inserted into the last joint of the thumb, after having passed its tendon under the ligament of the wrist. Use. To bend the last joint of the thumb.* • The thumb has but one flexor muscle on the front of the arm, although it has three extensors on the back part. —No animal but man has a distinct flexor lon- gus pollicis muscle. In the monkey even, its place is supplied by a branch of the communis digitorum tendon; man only can bring the thumb in direct opposition to the fingers, and make the hand a perfect instrument of prehension.—p. MUSCLES ON THE BACK OF THE FOREARM. 333 8. Pronator Radii Quadratus, Arises, broad, tendinous, and fleshy from the lower and inner part of the ulna; the fibres run transversely, to be Inserted into the lower and anterior part of the radius, oppo- site to its origin. Use. To turn the radius, together with the hand, inwards. Muscles of the External Side and Back of ihe Arm. 1. Supinator Radii Longus, Arises, by an acute and fleshy origin, from the external ridge of the os humeri, above the external condyle, nearly as far up as the middle of that bone. Inserted into the outer side of the inferior extremity of the radius. Use. To roll the radius outwards, and consequently the palm of the hand upwards. 2. Extensor Carpi Radialis Longior, Arises, broad, thin, and fleshy, immediately below the supina- tor radii longus, from the lower part of the external ridge of the os humeri, above its external condyle. Inserted, by a round tendon, into the posterior and upper part of the metacarpal bone that sustains the fore-finger. Use. To extend and bring the hand backwards. 3. Extensor Carpi Radialis Brevior, Arises, tendinous, from the external condyle of the os humeri, and from the ligament that connects the radius to it, and runs along the outside of the radius. Inserted, by a round tendon, into the upper and back part of the metacarpal bone that sustains the middle finger. Use. To assist the last mentioned muscle. 4. Extensor Carpi Ulnaris, Arises, tendinous from the external condyle of the os humeri, 334 MUSCLES ON THE BACK OF THE FOREARM and in its progress, fleshy, from the middle of the ulna, where it passes over the ulna. Its round tendon is enclosed by a mem- branous sheath, in a groove which is situated at the extremity of the ulna. Inserted, by its round tendon, into the posterior and upper part of the metacarpal bone that sustains the little finger. Use. To assist the former in extending the hand. 5. Extensor Digitorum Communis, Arises, by an acute, tendinous, and fleshy beginning, from the external condyle of the os humeri, where it adheres to the supinator radii brevis. Before it passes under the ligamentum carpi annulare externum, it splits into four tendons; some of which may be divided into several smaller; and about the fore- part of the metacarpal bones they remit tendinous filaments to each other. Inserted into the posterior part of all the bones of the four fin- gers, by a tendinous expansion. Use. To extend all the joints of the fingers. 6. Supinator Radii Brevis, Arises, tendinous, from the external condyle of the os humeri; tendinous and fleshy, from the external and upper part of the ulna, and adheres firmly to the ligament that joins these two bones. Inserted, into the head, neck, and tubercle of the radius, near the insertion of the biceps, and into the ridge running from that downwards and outwards. Use. To roll the radius outwards, and so bring the hand supine. 7. Indicator, Arises, by an acute fleshy beginning, from the middle of the posterior part of the ulna; its tendon passes under the same ligament with the extensor digitorum communis, with part of which it is Inserted into the posterior part of the fore-finger. Use. To extend the fore-finger separately. MUSCLES ON THE PALM OF THE HAND. 335 8. Extensor Ossis Metacarpi Pollicis Manus, Arises, fleshy, from the middle and posterior part of the ulna, immediately below the insertion of the anconeus muscle, from the posterior part of the middle of the radius, and from the in- terosseous ligament. Inserted, generally by two tendons, into the os trapezium, and upper back part of the metacarpal bone of the thumb, and often joins with the adductor pollicis. Use. To extend the metacarpal bone of the thumb, outwardly. 9. Extensor Primi Internodii, (Ext. Major Pollicis Manus,) Arises, fleshy, from the posterior part of the ulna near the former muscle, and from the interosseous ligament. Inserted, tendinous, into the posterior part of the first bone ol the thumb; and a part of it may be traced as far as the second bone. Use. To extend the first bone of the thumb obliquely out- wards. 10. Extensor Secundi Internodii, (Ext. Minor Pollicis Manus,) Arises, by an acute, tendinous, and fleshy beginning, from the middle back part of the ulna, and from the interosseous liga- ment ; its tendon runs through a small groove at the inner and back part of the lower end of the radius. Inserted into the last bone of the thumb. Use. To extend the last joint of the thumb obliquely back- wards. Muscles on the Palm of the Hand. To obtain a full view of the muscles situated on the palm of the hand, it will be necessary to remove the annular or transverse ligament, which is stretched across from the projecting points of the pisiform and unciform bones on the inside of the wrist to the scaphoid and trapezium on the outside; for the purpose of retaining the tendons of the flexor muscles in their proper situation. And also, to remove from the palm of the hand the aponeurosis palmaris, which has been described with the palmaris longus muscle. 336 MUSCLES ON THE PALM OF THE HAND. 1. Palmaris Brevis, Arises from the ligamentum carpi annulare, and tendinous membrane that is expanded on the palm of the hand. Inserted, by small bundles of fleshy fibres, into the skin and fat that covers the adductor minimi digiti, and into the os pisi- forme. Use. To assist in contracting the palm of the hand. 2. Adductor Pollicis Manus, Arises, by a broad tendinous, and fleshy beginning, from the ligamentum carpi annulare, and from the os trapezium. Inserted, tendinous, into the outer side of the root of the first phalanx of the thumb. Use. To draw the thumb from the fingers. 3. Flexor Osiss Metacarpi Pollicis, or Opponens Pollicis, Arises, fleshy, from the os trapezium and ligamentum carpi annulare, lying under the adductor pollicis. Inserted, tendinous and fleshy, into the under and anterior part of the metacarpal bone of the thumb. Use. To bring the thumb inwards, opposite to the other finger. 4. Flexor Brevis Pollicis Manus, Is divided into two portions by the tendon of the flexor longus pollicis, and is placed beneath the adductor, and at the side of the opponens. It is divided into two heads. The first arises fleshy from the volar sides of the trapezium, trapezoides, and from the contiguous part of the internal surface of the annular ligament. The second head arises from the magnum, unciforme, and from the base of the metacarpal bone of the middle finger. Inserted, by the first head into the outer sesamoid bone, and by the second into the inner sesamoid bones. These bones act the parts of patella?, by having a tendinous connexion with the first phalanx of the thumb. Use. To bend the first joint of the thumb. MUSCLES ON THE PALM OF THE HAND. 337 5. Abductor Pollicis Manus, Aidses, fleshy, from almost the whole length of the metacar- pal bone that sustains the middle finger; from thence its fibres are collected together. Inserted, tendinous, into the inner part of the root of the first phalanx of the thumb. Use. To pull the thumb towards the fingers. There are four small flexors, called, from their form, 6. Lumbricales, Which arise, thin and fleshy, from the outside of the tendons of the flexor profundus, a little above the lower edge of the liga- mentum carpi annulare. Inserted, by long slender tendons, into the outer sides of the broad tendons of the interossei muscles, about the middle of the first joint. Use. To increase the flexion of the fingers while the long flexors are in full action. 7. Adductor Metacarpi Minimi Digiti Manus, Arises, fleshy from the thin edge of the os unciforme, and from that part of the ligament of the wrist next to it. Inserted, tendinous, into the inner side and anterior part of the metacarpal bone of this finger. Use. To bend and bring the metacarpal bone of this finger towards the wrist. , 8. Flexor Parvus Minimi Digiti, Arises, fleshy, from the outer side of the os unciforme, and from the ligament of the wrist which joins with that bone. Inserted, by a roundish tendon, into the inner and anterior part of the upper end of the first bone of this finger. Use. To bend the little finger, and assist the adductor. vol. i. 29 338 MUSCLES ON THE PALM OF THE HAND. 9. Abductor Minimi Digiti Manus, Arises, fleshy, from the os pisiforme, and from that part of the ligamentum carpi annulare next it. Inserted, tendinous, into the inner side of the upper end of the first bone of the little finger. Use. To draw this finger from the rest. The spaces between the metacarpal bones are occupied by muscles, called, from their situation, interosseous. The four fol- lowing are to be seen on the palm of the hand. Anterior Interosseous Muscles. 1. Prior Indicis, Arises, tendinous and fleshy, from the upper and outer part of the metacarpal bone that sustains the fore-finger. Inserted into the outside of that part of the tendinous expan- sion from the extensor digitorum communis, which covers the posterior part of the fore-finger. Use. To draw the fore-finger outwards towards the thumb, and extend it obliquely. 2. Posterior Indicis, Arises, tendinous and fleshy, from the root and inner part of the metacarpal bone that sustains the fore-finger. Inserted into the inner side of the tendinous expansion which is sent off from the extensor digitorum communis, along the pos- terior part of the fore-finger. Use. To extend the fore-finger obliquely, and to draw it in- wards. 3. Prior Annularis, Arises, from the root of the outside of the metacarpal bone that sustains the ring finger. Inserted into the outside of the tendinous expansion of the ex- tensor digitorum communis which covers the ring finger. Use. To extend and pull the ring finger towards the thumb. MUSCLES ON THE BACK OF THE HAND. 339 4. Interosseous Auricularis, Arises, from the root and outer side of the metacarpal bone of the little finger; and is Inserted into the outside of the tendinous expansion of the ex- tensor digitorum communis, which covers the posterior part of the little finger. Use. To extend and draw the little finger outwards. On the back of the hand three muscles of the same kind are to be seen, which also appear on the palm. Posterior Interosseous Muscles. 1. Prior Medii, Arises, by two origins, from the root of the metacarpal bones that sustain the fore and middle fingers externally, and next each other: runs along the outside of the middle finger; and, being conspicuous on both sides of the hand, is Inserted into the outside of the tendinous expansion from the extensor digitorum communis, which covers the posterior part of the middle finger. Use. To extend and to draw the middle finger outwards. 2. Posterior Medii, Arises, by two origins, from the roots of the metacarpal bones next each other, that sustain the middle and ring fingers. Inserted into the inside of the tendinous expansion from the extensor digitorum communis, which runs along the posterior part of the middle finger. Use. To extend and draw the middle finger inwards. 3. Posterior Annularis, Arises, by two origins, from the roots of the metacarpal bones that sustain the ring and little fingers, next each other. Inserted into the inside of the tendon on the back of the ring finger. 340 MUSCLES OF THE OS FEMORIS. Use. To draw the ring finger inward. The following muscle also appears on the back of the hand. Abductor Indicis Manus, Arises, from the os trapezium, and from the superior part and inner side of the metacarpal bone of the thumb. Inserted, by a short tendon, into the outer and back part of the first bone of the fore finger. Use. To bring the fore finger towards the thumb. MUSCLES OF THE INFERIOR EXTREMITIES. These may be divided into the muscles situated on the outside of the pelvis, on the thigh, on the leg, and on the foot. The muscles on the outside of the pelvis, which are called muscles of the thigh, Are composed of one layer before and three layers behind. The layer before consists of five muscles: 1. Psoas Magnus. > gee p 31g> 31fl_ 2. Iliacus Internus. y 3. Pectinalis, Arises, broad and fleshy, from the upper and anterior part of the os pubis or pectinis, immediately above the foramen thy- roideum. Inserted into the anterior and upper part of the linea aspera of the os femoris, a little below the trochanter minor, by a flat and short tendon. Use. To bring the thigh upwards and inwards, and to give it a degree of rotation outwards. 4. Triceps Adductoi' Femoris, Under this appellation are comprehended three distinct mus- cles: MUSCLES OF THE OS FEMORIS. 34 J a. Adductor Longus Femoris, Arises, by a strong roundish tendon, from the upper and ante- rior part of the os pubis, and from the symphysis pubis, on the inner side of the pectinalis. Inserted, tendinous, near the middle of the posterior part of the linea aspera, being continued for some way down. b. Adductor Brevis Femoris, Arises, tendinous, from the os pubis near its joining with the opposite os pubis, below and behind the former. Inserted, tendinous and fleshy, into the inner and upper part of the linea aspera, from a little below the trochanter minor, to the beginning of the insertion of the adductor longus. c. Adductor Magnus Femoris, Arises, a little lower down than the former, near the symphysis of the ossa pubis, tendinous and fleshy from the tuberosity of the os ischium; the fibres run outwards and downwards. Inserted into almost the whole length of the linea aspera; into a ridge above the internal condyle of the os femoris; and, by a roundish long tendon, into the upper part of that condyle, a little above which, the femoral artery takes a spiral turn towards the ham, passing between this muscle and the bone. Use of these three muscles, or triceps. To bring the thigh inwards and upwards, according to the different directions of their fibres; and, in some degree, to roll the thigh outwards. 5. Obturator Externus, Arises, fleshy, from the lower part of the os pubis, and fore- part of the inner crus of the ischium; surrounds the foramen thyroideum; a number of its fibres, arising from the membrane which fills up that foramen, are collected like rays towards a centre, and pass outwards around the root of the back part of the cervix of the os femoris. 29* 342 MUSCLES OF THE OS FEMORIS Inserted, by a strong tendon, into the cavity at the inner and back part of the root of the trochanter major, adhering in its course to thecapsular ligament of the thigh bone. Use. To roll the thigh bone obliquely outwards, and to pre- vent the capsular ligament from being pinched. Behind are, First layer, Gluteus Maximus, Arises, fleshy, from the posterior part of the spine of the os ilium, a little higher up than the joining of the ilium with the os sacrum, from the whole external side of the os sacrum, below the posterior spinous process of the os ilium ; from the posterior sacro-ischiatic ligament, over which part of the inferior edge of this muscle hangs in a folded manner, and from the os coccygis. All the fleshy fibres run obliquely forwards, and a little down- wards, to form a thick broad muscle, which is divided into a number of strong fasciculi. The upper part of it covers almost the whole of the trochanter major, between which and the ten- don of this muscle there is a large bursa mucosa, and where it is inseparably joined to the broad tendon of the tensor vagina femoris. Inserted, by a strong, thick, and broad tendon, into the upper and outer part of the linea aspera, which is continued from the trochanter major, for some way downwards, as far as the origin of the short head of the biceps flexor cruris—and also into the fascia femoris. Use. To extend the thigh, by pulling it directly backwards, and a little outwards. Second layer, Gluteus Medius, Arises, fleshy, from the anterior superior spinous process of the os ilium, and from all the outer edge of the spine of the ilium; except its posterior part, where it arises from the dorsum of that bone. Inserted, by a broad tendon, into the outer and upper margin of the trochanter major. MUSCLES OF THE OS FEMORIS. 343 Use. To draw the thigh bone outwards, and a little back- wards; to roll the thigh bone outwards, especially when it is bended. N. B. The anterior and upper part of this muscle is covered by a tendinous membrane, from which a number of its fleshy fibres arise, and which joins with the broad tendons of the glu- teus maximus, tensor vagina? femoris, and latissimus dorsi. Third layer consists of four muscles. 1. Gluteus Minimus, Arises, fleshy, from a ridge that is continued from the superior anterior spinous process of the os ilium, and from the middle of the dorsum of that bone, as far back as its great niche. Inserted, by a strong tendon, into the fore and upper part of the trochanter major. Use. To assist the former in pulling the thigh outwards and backwards, and in rolling it. 2. Pyriformis, Arises, within the pelvis, by three tendinous and fleshy ori- gins, from the second, third, and fourth pieces of the os sacrum; from thence growing gradually narrower, it passes out of the pelvis along with the posterior crural nerve, below the niche in the posterior part of the os ilium, where it receives a few fleshy fibres. Inserted, by a roundish tendon, into the upper part of the ca- vity, at the inner side of the root of the trochanter major. Use. To move the thigh a little upwards, and roll it outwards. 3. Gemini, Arises, by two distinct origins ; the superior from the spinous process, and the inferior from the tuberosity of the os ischium; also, from the posterior sacro-ischiatic ligament. They are both united by a tendinous fleshy membrane, and form a purse for the tendon of the obturator internus muscle, which was for- merly described. Inserted, tendinous and fleshy, into the cavity at the inner side 344 MUSCLES OF THE THIGH. of the root of the trochanter major, on each side of the tendon of the obturator internus, to which they firmly adhere. Use. To roll the thigh outwards, and to preserve the tendon of the obturator internus from being hurt by the hardness of that part of the os ischium over w hich it passes; also, to hinder it from starting out of its place, while the muscle is in action. 4. Quadratus Femoris, Arises, tendinous and fleshy, from the outside of the tuberosity of the os ischium; and, running transversely, is Inserted, fleshy, into a rough ridge, continued from the root of the large trochanter to the root of the small one. Use. To roll the thigh outwards. Muscles situated on the Thigh. These are called muscles of the leg; and consist of one, on the outside; two, on the inside; four, before; and four, behind. Previous to the description of the muscles that are situated on the thigh and leg, it is necessary to take notice of a broad ten- dinous fascia or sheath, (aponeurosis of the lower extremities,) which is sent off from the back and from the tendon of the glutei and adjacent muscles. It is a strong thick membrane on the outside of the thigh and leg; but, towards the inside of both, it gradually turns thinner, and has rather the appearance of cellular substance than a ten- dinous membrane. A little below the trochanter major, it is firmly fixed to the linea aspera; and, farther down, to that part of the head of the tibia that is next the fibula; where it sends off the tendinous expansion along the outside of the leg. It serves to strengthen the action of the muscles, by keeping them firm in their proper places while in action, particularly the tendons that pass over the joints where this membrane is thickest, and it gives origin to a number of the fleshy fibres of the mus- cles. On the outside is, MUSCLES OF THE THIGH. 345 Tensor Vagina Femoris, Arises, by a narrow, tendinous, and fleshy beginning, from the external part of the anterior superior spinous process of the os ilium. Inserted, a little below the trochanter major, into the inner side of the membranous fascia which covers the outside of the thigh. Use. To stretch the membranous fascia, to assist in the ad- duction of the thigh, and somewhat in its rotation inwards. On the inside are, 1. Sartorius, Arises, tendinous from the anterior superior spinous process of the os ilium, soon grows fleshy, runs down for some space upon the rectus, and going obliquely inwards, it passes over the vastus internus, and, about the middle of the os femoris, over part of the triceps; it runs down farther between the tendon of the ad- ductor magnus and that of the gracilis muscles. Inserted, by a broad and thin tendon, into the inner side of the tibia, near the inferior part of its tubercle. Use. To bend the leg obliquely inwards, or to bring one leg across the other. 2. Gracilis, Arises, by a thin tendon, from the os pubis, near the symphysis of these two bones, soon grows fleshy, and, descending by the in- side of the thigh, is Inserted, tendinous, into the tibia under the sartorius. Use. To assist the sartorius. Before are, 1. Rectus, Arises, fleshy, from the inferior anterior spinous process of the os ilium, and tendinous from the dorsum of the ilium, a little above the acetabulum; runs down over the anterior part of the 346 MUSCLES OF THE THIGH. cervix of the os femoris; the fibres not being straight, but run- ning down like the plumage of a feather obliquely outwards and inwards, from a tendon in the middle. Inserted, tendinous, into the upper part of the patella, from which a thin tendon runs down, on the forepart of this bone, to terminate in a thick strong ligament, which is sent off from the inferior part of the patella, and inserted into the tubercle of the tibia. Use. To extend the leg, and, in a powerful manner, by the intervention of the patella, like a pulley. 2. Vastus Externus, Arises, broad, tendinous and fleshy, from the root of the tro- chanter major, and upper part of the linea aspera; its origin be- ing continued from near the insertion of the gluteus minimus, the whole length of the linea aspera, by fleshy fibres which run obliquely forwards to a middle tendon, where they terminate. Inserted into a large share of the upper part of the patella; and part of it ends in an aponeurosis, which is continued down to the leg, and in its passage is firmly fixed to the head of the tibia. Use. To extend the leg. 3. Vastus Internus, Arises, tendinous and fleshy, from between the forepart of the os femoris and root of the trochanter minor, and from almost all the inside of the linea aspera, by fibres running obliquely for- wards and downwards. Inserted, tendinous, into the upper and inside of the patella, continuing fleshy lower than the vastus externus. Part of it likewise ends in an aponeurosis continued down to the leg, and fixed in its passage to the upper part of the tibia. Use. To extend, the leg. 4. Cruralis, Arises, fleshy, from between the two trochanters of the os MUSCLES OF THE THIGH. 347 femoris, but nearer the lesser trochanter, and firmly adhering to most of the forepart of the os femoris, and connected to both vasti muscles. Inserted, tendinous, into the upper part of the patella, behind the rectus. Use. To assist in the extension of the leg. N B. These four muscles, before, being inserted into the pa- tella, have the same effect upon the leg as if they were imme- diately inserted into it by means of the strong tendon, or rather ligament which is sent off from the inferior part of the patella to the tibia. Behind are, 1. Semitendinosus, Arises, tendinous and fleshy, in common with the long head of the biceps, from the posterior part of the tuberosity of the os ischium ; and sending down a long roundish tendon, which ends flat, is Inserted into the inside of the ridge of the tibia, a little below its tubercle. Use. To bend the leg backwards and a little inwards. 2. Semimembranosus, Arises, tendinous, from the upper and posterior part of the tuberosity of the os ischium; sends down a broad flat tendon, which ends in a fleshy belly, and, in its descent, runs at first on the forepart of the biceps, and lower, between it and the semi- tendinosus. Inserted, tendinous, into the inner and back part of the head of the tibia. Use. To bend the leg, and bring it directly backward. N B. The two last form what is called the inner hamstring. 3. Biceps Flexor Cruris, Arises by two distinct heads. The first, called longus, arises, in common with the semitendinosus, from the upper and poste- rior part of the tuberosity of the os ischium. The second, 348 MUSCLES ON THE FRONT OF THE LEG. called brevis, arises from the linea aspera, a little below the ter- mination of the gluteus maximus, by a fleshy acute beginning, which soon grows broader as it descends to join with the first head, a little above the external condyle of the os femoris. Inserted, by a strong tendon, into the upper part of the head of the fibula. Use. To bend the leg. N. B. This muscle forms what is called the outer hamstring; and between it and the inner, the nervus popliteus, the arteria and vena poplitea, are situated. 4. Popliteus, Arises, by a round tendon, from the lower and back part of the external condyle of the os femoris, then runs over the liga- ment that involves the joint; firmly adhering to it, and part of the semilunar cartilage. As it runs over the joint, it becomes fleshy, and the fibres run obliquely inwards, being covered with a thin tendinous membrane. Inserted, broad, thin and fleshy, into a ridge at the upper and internal edge of the tibia, a little below its head. Use. To assist in bending the leg, and to prevent the capsular ligament from being pinched. After the leg is bent, this muscle serves to roll it inwards. Muscles situated on the Leg. These muscles may be arranged in the two general classes of flexors and extensors of the foot, and flexors and extensors of the toes; but several of them, viz. the tibialis and the peronei, produce effects which are different from flexion or extension. For the accommodation of the student of ana- tomy, they may be studied in the order of their position as they lie on the front, on the outside, and on the back of the leg. Muscles on the Front of the Leg. 1. Tibialis Anticus, Arises, tendinous and fleshy, from the middle of that process of the tibia, to which the fibula is connected above; then it runs down fleshy on the outside of the tibia; from which, and MUSCLES ON THE LEG, 349 the upper part of the interosseous ligament, it receives a number of distinct fleshy fibres; near the extremity of the tibia, it sends off a strong round tendon, which passes under part of the liga- mentum tarsi annulare near the malleolus internus. Inserted, tendinous, into the inside of the os cuneiforme inter- num, and posterior end of the metatarsal bone that sustains the great toe. Use. To bend the foot, by drawing it upwards, and, at the same time, to turn the toes inwards. Extensor Proprius Pollicis Pedis, Arises, by an acute, tendinous, and fleshy beginning, some way below the head and anterior part of the fibula, along which it runs to near its lower extremity, connected to it by a number of fleshy fibres, which descend obliquely towards a tendon. Inserted, tendinous, into the posterior part of the first and last joint of the great toe. Use. To extend the great toe. 3. Extensor Longus Digitorum Pedis, Arises, tendinous and fleshy, from the upper and outer part of the head of the tibia, and from the head of the fibula where it joins with the tibia, and from the interosseous ligament; also from the tendinous fascia, which covers the upper and outside of the leg by a number of fleshy fibres ; and tendinous and fleshy from the anterior spine of the fibula, almost its whole length, where it is inseparable from the peroneus tertius. It splits into four round tendons, under the ligamentum tarsi annulare. Inserted, by a flat tendon, into the root of the first joint of each of the four small toes ; and is expanded over the upper side of the toes, as far as the root of the last joint. Use. To extend all the joints of the four small toes. N. B. A portion of this muscle, which is called 4. Peroneus Tertius, Arises, from the middle of the fibula, continues down to near vol. i. 30 350 MUSCLES ON THE LEG. its inferior extremity, and sends its fleshy fibres forwards to a tendon, which passes under the annular ligament, and is Inserted, into the root of the metatarsal bone that sustains the little toe. Use. To assist in bending the foot. Muscles on the outside of the Leg. 1. Peroneus Longus, Arises, tendinous and fleshy, from the forepart of the head of the peroneus,or fibula, the fibres running straight down; also from the upper and external part of the fibula, where it begins to rise into a round edge; as, also, from the hollow between that and its anterior edge, as far down as to reach within a hand's breadth of the ankle, by a number of fleshy fibres, which run outwards towards a tendon, that subsequently becomes long and round, and passes through a channel at the outer ankle, in the back part of the inferior extremity of the fibula; then being reflected to the sinuosity of the os calcis, it runs along a groove in the os cuboides, above the muscles in the sole of the foot. Inserted, tendinous, into the outside of the root of the meta- tarsal bone that sustains the great toe, and by some tendinous fibres into the os cuneiforme internum. Use. To turn the foot outwards, and to extend it a little. 2. Peroneus Brevis, Arises, by an acute fleshy beginning, from above the middle of the external part of the fibula; from the outer side of the an- terior spine of this bone; as also from its round edge externally, the fibres running obliquely outwards towards a tendon on its external side : it sends off a round tendon which passes through the groove at the outer ankle, being there included under the same ligament with that of the preceding muscle; and a little farther, it runs through a particular one of its own. Inserted, tendinous, into the root and external part of the metatarsal bone that sustains the little toe. Use. To assist the former in pulling the foot outwards, and extending it a little. MUSCLES ON THE LEG. 351 Muscles on the back of the Leg. 1. Gastrocnemius Externus, seu Gemellus, Arises, by two distinct heads. The first head arises from the upper and back part of the internal condyle of the os femoris, and from that bone, a little above its condyle, by two distinct tendinous origins. .The second head arises tendinous from the upper and back part of the external condyle of the os femoris. A little below the joint, their fleshy bellies unite in a middle ten- don ; and, below the middle of the tibia, it sends off a broad thin tendon, which joins a little above the extremity of the tibia with the tendon of the following. 2. Soleus, seu Gastrocnemius Internus, Arises by two origins. The first is from the upper and back part of the head of the fibula, continuing to receive many of its fleshy fibres from the posterior part of that bone for some space below its head. The other origin begins from the posterior and upper part of the middle of the tibia; and runs inwards along the inferior edge of the popliteus towards the inner part of the tibia, from which it receives fleshy fibres for some way down. The flesh of this muscle, covered by the tendon of the gemellus, runs down nearly as far as the extremity of the tibia; a little above which the tendons of both gastrocnemii unite, and form a strong round chord, which is called tendo-achillis. Inserted into the upper and posterior part of the os calcis, by the projection of which the tendo-achillis is placed at a considera- ble distance from the tibia. Use. To extend the foot, by bringing it backwards and down- wards. 3. Plantains, Arises, thin and fleshy, from the upper and back part of the root of the external condyle of the os femoris, near the interior extremity of that bone, adhering to the ligament that involves the joint in its descent. It passes along the second origin of the soleus and under the gemellus, where it sends off a long, slender, 352 MUSCLES ON THE LEG. thin tendon, which comes from between the great extensors, where they join tendons; then runs down by the inside of the tendo-achillis. Inserted, into the inside of the posterior part of the os calcis, below the tendo-achillis. Use. To assist the former, and to pull the capsular ligament of the knee from between the bones. It seems likewise to as- sist in rolling the foot forwards. 4. Flexor Longus Digitorum Pedis, Profundis, Perforans, Arises by an acute tendon, which soon becomes fleshy from the back part of the tibia, some way below its head, near the entry of the medullary artery; which beginning, is continued down the inner edge of this bone by short fleshy fibres, ending in its tendon ; also by tendinous and fleshy fibres, from the outer edge of the tibia, and between this double order of fibres, the tibialis posticus muscle lies enclosed. Having passed under two annular ligaments, it then passes through a sinuosity at the inside of the os calcis; and about the middle of the sole of the foot, divides into four tendons, which passes through the slits of the perforatus; and just before its division it receives a considera- ble tendon from that of the flexor pollicis longus. Inserted into the extremity of the last joint of the four lesser toes. Use. To bend the last joint of the toes. 5. Tibialis Posticus, Arises, by a narrow fleshy beginning, from the fore and upper part of the tibia, just under the process which joins it to the fibula; then passing through a perforation in the upper part of the interosseous ligament, it continues its origin from the back part of the fibula next the tibia, and from near one half of the upper part of the last named bone; as also, from the interosse- ous ligament, the fibres running towards a middle tendon, which sends off a round one that passes in a groove behind the malleo- lus internus. Inserted, tendinous, into the upper and inner part of the os MUSCLES ON THE SOLE OF THE FOOT. 353 naviculare, being farther continued to the os cuneiforme inter- num and medium; besides it gives some tendinous filaments to the os calcis, os cuboides, and to the root of the metatarsal bone that sustains the middle toe. Use. To extend the foot, and to turn the toes inwards. 6. Flexor Longus Pollicis Pedis, Arises, by an acute, tendinous, and fleshy beginning, from the posterior part of the fibula, some way below its head, being con- tinued down the same bone, almost to its inferior extremity, by a double order of oblique fleshy fibres; its tendon passes under an annular ligament at the inner ankle. Inserted into the last joint of the great toe, and, generally, sends a small tendon to the os calcis. Use. To bend the last joint of this toe. On the upper surface of the foot there is one muscle, viz. Extensor Brevis Digitorum Pedis, Arises, fleshy and tendinous, from the fore and upper part of the os calcis; and soon forms a fleshy belly, divisible into four portions, which send oft' an equal number of tendons that pass over the upper part of the foot, under the tendons of the former. Inserted, by four slender tendons, into the tendinous expansion from the extensor longus which covers the small toes, except the little one; also into the tendinous expansion from the extensor pollicis, that covers the upper part of the great toe. Use. To extend the toes. Muscles on the Sole of the Foot. On the sole of the foot there is a strong tendinous membrane called Apo- neurosis Plantaris, which originates from the tuberosity of the os calcis, and proceeds forward to the toes, increasing gradually in breadth. It is divided into three portions. That in the middle is the largest; it pro- tects and covers the short flexor muscles, and the tendons in the middle of the foot. That on the outside, which covers the adductor and flexor of the little toe, is next in size. The internal portion, which covers the ad- ductor of the great toe, is the smallest. 30 '' 354 MUSCLES ON THE SOLE OF THE FOOT. The edges of these portions dip down so as to separate the muscles they cover from each other. They are divided into five processes, correspond- ing with the heads of the metatarsal bones; each of these portions is di- vided into two bands, which are inserted into each side of the head of each metatarsal bone, and the tendons, nerves, and arteries pass between them. Immediately under the middle portion of this aponeurosis are the common short flexors of the toes, viz. 1. Flexor Brevis Digitorum Pedis Sublimis Perforatus, Arises, by a narrow fleshy beginning, from the inferior and posterior part of the protuberance of the os calcis, between the adductors of the great and little toes, soon forms a thick fleshy belly, which sends off four tendons that split for the passage of the flexor longus. Inserted into the second phalanx of the four lesser toes. The tendon of the little toe is often wanting. Use. To bend the second joint of the toes. 2. Flexor Digitorum Accessorius, seu, Massa Cornea Jacobii Sylvii, Arises, by a thin fleshy origin, from most part of the sinuosity at the inside of the os calcis, which is continued forwards, for some space on the same bone; also, by a thin tendinous begin- ning, from before the tuberosity of the os calcis, externally, and, soon becoming all fleshy, is Inserted into the tendon of the flexor longus, just at its division into four tendons. Use. To assist the flexor longus. 3. Lumbricales Pedis, Arises, by four tendinous and fleshy beginnings, from the ten- don of the flexor profundus, just before its division, near the in- sertion of the massa carnea. Inserted, by four slender tendons, into the inside of the first joint of the four lesser toes, and are lost in the tendinous expan- sion that is sent from the extensors to cover the upper part of the toes. MUSCLES ON THE SOLE OF THE FOOT. 355 Use. To increase the flexion of the toes, and to draw them inwards. On the inside of the foot, and under the common flexors, are the muscles which are considered as exclusively appropriated to the great toe, viz. 1. Abductor Pollicis Pedis, Arises from the internal side of the tuberosity of the os calcis, and from a ligament which extends from this tuberosity to the sheath of the tendon of the tibialis posticus muscle, and also from the internal and inferior side of the os naviculare and cuneiforme internum. It likewise arises from that portion of the aponeurosis plantaris, which separates it from the short flexor of the toes, and many of its fibres appear to be connected with the ligaments which pass from the posterior to the anterior bones of the foot: as it passes under the cuneiform bone, a portion of its lower surface is tendinous. It is inseparably connected to the flexor of the great toe, and is inserted into the internal sesamoid bone, and the inferior and internal part of the root of the first bones of the great toe. This muscle not only separates the great toe from the other toes, but it must increase the curvature, or arched form of the foot. 2. Flexor Brevis Pollicis Pedis, Arises, tendinous, from the under and forepart of the os calcis, where it joins with the os cuboides, from the os cuneiforme ex- ternum, and is inseparably united with the abductor and adduc- tor pollicis. Inserted into the internal and external sesamoid bones, along with the abductor and adductor pollicis, and into the root of the first joint of the great toe. Use. To bend the first joint. 3. Adductor Pollicis Pedis, Arises, by a long thin tendon, from the os calcis, from the os cuboides, from the os cuneiforme externum, and from the root of the metatarsal bone of the second toe. 356 MUSCLES ON THE SOLE OF THE FOOT. Inserted into the external os sesamoideum, and root of the metatarsal bone of the great toe. Use. To bring this toe nearer the rest. Near the outer edge of the foot, under the second portion of the aponeurosis plantaris, are the muscles peculiar to the little toe, viz. 1. Abductor Minimi Digiti Pedis, Arises, tendinous and fleshy, from the semicircular edge of a cavity on the inferior part of the protuberance of the os calcis, and from the root of the metatarsal bone of the little toe. Inserted into the root of the first joint of the little toe exter- nally. Use. To draw the little toe outwards from the rest, and assist in preserving the arched form of the foot. 2. Flexor Brevis Minimi Digiti Pedis, Arises, tendinous, from the os cuboides, near the sulcus or fur- row for lodging the tendon of the peroneus longus; fleshy from the outside of the metatarsal bone that sustains the little toe, be- low its protuberant part. Inserted, into the anterior extremity of the metatarsal bone, and root of the first joint of this toe. Use. To bend this toe. Between the metatarsal bones are four external and three internal inter- ossei : and one muscle which is common to all the metatarsal bones. Interossei Pedis Externi, Bicipites. 1. Abductor Indicis Pedis, Arises, tendinous and fleshy, by two origins, from the root of the inside of the metatarsal bone of the fore toe, from the outside of the root of the metatarsal bone of the great toe, and from the os cuneiforme internum. Inserted, tendinous, into the inside of the root of the first joint of the fore toe. INTEROSSEOUS MUSCLES. 357 Use. To pull the fore toe inwards from the rest of the small toes. 2. Adductor Indicis Pedis, Arises, tendinous and fleshy, from the roots of the metatarsal bones of the fore and second toe. Inserted, tendinous, into the outside of the root of the first joint of the fore toe. Use. To pull the fore toe outwards towards the rest. 3. Adductor Medii Digiti Pedis, Arises, tendinous and fleshy, from the roots of the metatarsal bones of the second and third toes. Inserted, tendinous, into the outside of the root of the first joint of the second toe. Use. To pull the second toe outwards. 4. Adductor Tertii Digiti Pedis, Arises, tendinous and fleshy, from the roots of the metatarsal bones of the third and little toe. Inserted, tendinous into the outside of the root of the first joint of the third toe. Use. To pull the third toe outwards. Interossei Pedis Inlerni, 1. Abductor Medii Digiti Pedis, Arises, tendinous and fleshy, from the inside of the root of the metatarsal bone of the middle toe internally. Inserted, tendinous, into the inside of the root of the first joint of the middle toe. Use. To pull the middle toe inwards. 2. Abductor Tertii Digiti Pedis, Arises, tendinous and fleshy, from the inside and inferior part of the root of the metatarsal bone of the third toe. 358 INTEROSSEOUS MUSCLES. Inserted, tendinous, into the inside of the root of the first joint of the third toe. Use. To pull the third toe inwards. 3. Abductor Minimi Digiti Pedis, Arises, tendinous and fleshy, from the inside of the root of the metatarsal bone of the* little toe. Inserted, tendinous, into the inside of the root of the first joint of the little toe. Use. To pull the little toe inwards. The common muscle, Transversalis Pedis, Arises, tendinous, from the under part of the anterior extremity of the metatarsal bone of the great toe, and from the internal os sesamoideum of the first joint, adhering to the adductor pollicis. Inserted, tendinous, into the under and outer part of the anterior extremity of the metatarsal bone of the little toe, and ligament of the next toe. Use, to contract the foot, by bringing the great toe and the two outermost toes nearer each other. MOTIONS OF THE SKELETON. 359 CHAPTER IX. OBSERVATIONS ON THE MOTIONS OF THE SKELETON. The falling down of the body during life, when muscular ac- tion is suspended, as well as the examination of the artificial skeleton, evince that this machine is not constructed to preserve the erect position of itself; but that, when unsupported, it bends at the joints, and invariably falls forward. It is retained in the erect position by the action of muscles : and that the muscles should produce this effect, it is necessary that they should have a fixed basis to act from. This basis is the feet, and they are fixed to the ground by the weight of the body. To keep the body from falling, it is necessary that the centre of gravity should be immediately over the centre of the com- mon basis. All our movements, both in walking, standing, and rising from our seats, are regulated by this principle; and whenever we move our body, so that the centre of gravity is changed, we must change the position of the feet, that the centre of the basis may be directly under it. If this proposition were not almost self-evident, it might be illustrated by several very easy experiments. If a person stand against a wall with his heels and the back parts of his legs and thighs in contact with it, and, in this situa- tion, attempts to stoop forward, he will fall upon his face; there is no power in his muscles, or in any other part of the body, when thus circumstanced, to prevent it; but a small movement forward of one foot, will enable him to stoop with ease by alter- ing the basis of the body. When we sit in such a position that we cannot bring the cen- 360 ADJUSTMENT OF THE CENTRE OF GRAVITY. tre of gravity over the feet, the lower limbs are divested of all power of elevating the body: this is always the case when we sit with the thighs and legs at right angles with each other. Bend the knees to an acute angle, so that the feet are placed un- der the body, and we rise with ease. When we wish to stoop forward without advancing one of our feet, we acquire the power in a small degree, by placing our hands behind us, to preserve the equilibrium. Some old persons, whose spines curve forwards in conse- quence of age, bend their lower limbs, so that the pelvis may be projected backwards beyond the centre of the base of the body, and form a counterpoise to the upper part of the trunk. Bending the knees alone, without projecting the pelvis back- wards, will not produce this effect; for a person who stands with his back to a wall will bend his knees without obtaining this advantage, while the heels and back part of the pelvis are in contact with the wall. When we stand with the toes pointing directly forwards, the base of the body is a square; of which the feet are two of the sides. As the positions of the feet are changed, the figure of the base and its centre necessarily change also. When the feet are placed one immediately before the other, the centre is between the toes of the one and the heel of the other. When the posi- tion of the feet is such, that the toes point directly outwards, and the heels are opposite to each other, the centre of the base is be- tween the heels. In these cases, when the situation of the centre of the base is changed, we immediately change the centre of gravity. Thus, as we turn the toes outwards, the centre of the base moves backwards, we, therefore, immediately make the body more erect; and by that means keep the centre of gravity over the centre of the base. We move the centre of gravity laterally, as well as back- wards and forwards, in conformity to this principle. Thus, when we raise one foot from the ground, the body in- clines so much in the opposite direction, that the centre of ADJUSTMENT OF THE CENTRE OF GRAVITY. 361 gravity is directly over the other. If the spine is diseased in one spot, and assumes a lateral curvature, placing the centre of gravity on one side of the natural centre of the base; another curve is formed by muscular action, in a sound part of the spine, to counteract the first, and keep the centre of gravity in its natural position. The perception of a tendency to fall, when the centre of gra- vity is in a wrong situation, first induces us to make efforts to resist this tendency ; we learn by experience what these efforts ought to be: and by habit we at length make them without con- sciousness. As the natural tendency of the skeleton, when we stand, is to bend at the articulations, and, therefore, to fall forwards; the muscles which have the principal effort in keeping the body erect, must be the extensors. Thus, the muscles on the back of the leg, and particularly the soleus, keep the tibia erect: while the muscles on the front of the thigh, the vasti and crureus, produce the same effect upon the os femoris: the bones being kept steady by the occasional counteraction of the antagonist muscles. The whole lower limb is thus made erect by an exertion which begins at the foot, v/hile the foot is fixed to the ground by the weight and pressure of the body above it. The trunk of the body has a strong tendency to bend forward at the articulations of the thigh bones and the ossa innominata. This tendency is resisted by the muscles which lie on the back part of the ossa femoris, and extend the trunk on those bones viz. the glutei maximi. The muscles which arise from the tuberosity of the ischium, and are inserted into the leg, the semitendinosus, semimembra- nosus, and the long head of the biceps flexor cruris, have also this effect. The flexure of the thoracic and lumbar portions of the spine is counteracted by the sacro-lumbalis, and longissimus dorsi, which act from the sacrum and back parts of the pelvis. The yellow ligaments, which are elastic, must also co-operate to this effect: vol. i. 31 362 MUSCLES WHICH KEEP THE BODY ERECT. so that with regard to the spine, there is an additional agent dis- tinct from the muscular power. Indeed, respecting the vertebral articulations in general, it may be observed, that the connexion of the bodies of the verte- bra?, by the intervertebral cartilaginous matter, and of the plates behind, by the elastic ligament, renders these articulations per- fectly anomalous; and very different in their principles from the articulations in general. In no part of the skeleton is this tendency to bend forward more strongly perceived than in the head. When we are awake, and the muscles in a healthy situation, it is effectually restrained, and the head kept erect, by the splenius and com- plexus, and other muscles, which act from the spine below, upon the back part of the head and the vertebra? of the neck. When we stand on one foot, some very different muscles are called into action; the tendency of the body is to fall sideways, towards the foot which is raised from the ground. To counter- act this tendency the two larger peronei muscles, which are situated on the outside of the leg, act from the foot, to keep the leg erect. The vastus externus acts upon the same principle from the leg upon the os femoris. The gluteus medius and mi- nimus, and the muscle of the fascia lata, act from the os femoris upon the pelvis and trunk ; while the quadratus lumborum, and those abdominal muscles which draw the spine to that side, con- tinue the operation: and so do likewise the muscles which act on the same side of the neck and head. In rising from a seat, the tibialis anticus acts very powerfully, to keep the tibia erect, and prevent it from inclining backwards. The two vasti, and the crurseus, raise up the os femoris, while the gluteus maximus, the semitendinosus, and semimembranosus, and the long head of the biceps, extend the trunk of the body. There are several modes of walking, which are different from each other, in a small degree. We may walk, for example, with the knee of the hind limb straight or bent, as we bring it forward. This circumstance is merely a matter of accommodation. But there are two essential MUSCLES EMPLOYED IN RISING FROM A SEAT. oog processes in walking, viz. 1. Projecting one foot forward, and placing it on the ground while thus projected; and 2. Moving the body over that foot. The mode of projecting the foot requires no explanation ; but the manner of bringing it to the ground, when thus advanced ought to be noticed. If, after standing with both feet on the same line, we move one foot forwards, suppose the right foot, it cannot be applied flat to the ground, unless we either incline the body for vard or move the pelvis on the left thigh, so that the right side may pre- sent obliquely forward; or lower the right side of the pelvis, so that it may be nearer the ground. When we incline the body forward, and thus bring the right foot to the ground, we perform the second essential process in walking, along with the first: for we move the body over the fore foot. The muscles on the front part of the hind leg, and particularly the tibialis anticus, seem to produce this effect, by bending, or inclining forward, the tibia on the foot. When the foot is brought to the ground by a rotation of the pelvis, it is likewise the tibialis anticus, and the muscles on the front of the hind leg, that move the body over it, or that begin the motion. The gastrocnemius and soleus, and the flexors of the toes, par- ticularly that of the great toe, occasionally co-operate with great effect. By raising the heel, and thus lengthening the hind limb, they push the body forward, and continue its motion in that di- rection after the effect of the tibialis anticus ceases. The length of the step appears, therefore, to require this elevation of the heel, and depression of the toes; but it should be observed, that when we take long steps, we also turn the pelvis partly round, pre- senting the side obliquely forward ; and in this manner increase the anterior projection of the front leg. Although the action of the gastrocnemius, &c. seems neces- sary to walking with long steps, we can walk without their ope- ration. This is proved incontestably by the act of walking on the heel: when the gastrocnemii and the flexors are so far from 364 MOTIONS NECESSARY IN WALKING. acting, that they are in a state of extension. In this operation, the principal effort seems to be made by the tibialis anticus, and the muscles on the front of the leg; and the extensor muscles on the front of the thigh. Notwithstanding these facts, the action of the gastrocnemius and soleus is essential whenever we raise the heel from the ground, while the weight of the body presses on the front part of the foot; and it then acts with a force which equals, if it does not exceed, the weight of the body. Jumping, at the first view of it, appears an extraordinary ope- ration; but if a man who lies on the ground, with his feet against a wall, makes a muscular exertion, such as is necessary for jumping, the nature of the operation is very intelligible. It is a sudden extension of the feet and knees, and sometimes of the trunk of the body. The stroke is made against the wall; but as that does not yield, the whole motion is impressed upon the body; which is projected from the wall horizontally in the same way that in jumping, it is projected from the ground ver- tically. / 365 EXPLANATION OF PLATES VI. AND VII. Plate VI. Fig. 1. The Muscles immediately under the common teguments on the an- terior part of the body are represented on the right side; and on the left side the Muscles are seen which come in view when the exterior ones are taken away. A, The frontal muscle. JB, The tendinous aponeurosis which joins it to the occipital; hence both are named occipito-frontalis. C, Attollens aurem. D, The ear. E, Anterior auris. F F, Orbicularis palpebrarum. G, Le- vator labii superioris alseque nasi. H, Levator anguli oris. I, Zygomati- cus minor. K, Zygomaticus major. L, Masseter. M, Orbicularis oris. N, Depressor labii inferioris. O, Depressor anguli oris. P, Buccinator. Q.Q, Platysma myoides. RR, Sterno-cleido-mastoideus. S, Part of the trapezius. T, Part of the scaleni. Superior Extremity.—U, Deltoides. V, Pectoralis major. W, Part of the latissimus dorsi. X X, Biceps flexor cubiti. Y Y, Part of the tri- ceps extensor. Z Z, The beginning of the tendinous aponeurosis, (from the biceps,) which is spread over the muscles of the forearm, a a, Its' strong tendon inserted into the tubercle of the radius, bb, Part of the brachialis internus. c, Pronator radii teres, d, Flexor carpi radialis. e, Part of the flexor carpi ulnaris. f, Palmaris longus. g, Aponeurosis palmaris. 3, pal- maris brevis. 1, Ligamentum carpi annulare. 2 2, Abductor minimi digi- ti. h, Supinator radii longus. i, The tendons of the thumb, k, Abductor pollicis. 1, Flexor pollicis longus. m m, The tendons of the flexor subli- mis perforatus, profundus perforans, and lumbricales. The sheaths are en- tire in the right hand,—in the left cut open to show the tendons of the flexor profundus perforating the sublimis. Muscles—not referred to—in the left superior extremity, n, Pectoralis minor, seu serratus anticus minor, o, The two heads of (x x) the biceps. p, Coraco-brachialis. q q, The long head of the triceps extensor cubiti. r r, Teres major, ss, Subscapularis. tt, Extensores radialis. u, Supinator brevis. v, The cut extremity of the pronator teres, w, Flexor sublimis perforatus. x, Part of the flexor profundus, y, Flexor pollicis longus. z, Part of the flexor pollicis brevis. 4, Abductor minimi digiti. 5, The four lumbricales. Trunk.—6. Serrated extremities of the serratus anticus major. 7 7, Ob- liquus* externus abdominis. 88, The linea alba. 9, The umbilicus. 10, Pyramidalis. 11 11, The spermatic cord. On the left side it is covered by 31 * 366 EXPLANATION OF THE PLATES OF THE MUSCLES. the cremaster. 12 12, Rectus abdominis. 13, Obliquus internus. 14 14, &c. Intercostal muscles. Inferior Extremities.—a a, The gracilis, b b, Parts of the triceps. c c, Pectinalis. d d, Psoas magnus. e e, Iliacus internus. /, Part of the gluteus medius. g, Part of the glutaeus minimus, h, Cut extremity of the rectus femoris. i i, Vastus externus, k, Tendon of the rectus femoris. 11, Vastus internus, * Sartorius muscle. * * Fleshy origin of the tensor vagina? femoris or membranosus. Its tendinous aponeurosis covers (i) the vastus externus on the right side, m m, Patella, n n, Ligament or tendon from it to the tibia, o, Rectus femoris. p, Crurseus. q q, The ti- bia, r r, Part of the Gemellus, or gastrocnemius externus. sss, Part of the soleus or gastrocnemius internus. t, Tibialis anticus. u, Tibialis pos- ticus, v v, Peronsei muscles, w w, Extensor longus digitorum pedis, xx, Extensor longus pollicis pedis, y, Abductor pollicis pedis. Fig. 2. The muscles, Glands, &c., of the Left Side of the Face and Neck, after the common Teguments and Platysma myoides have been taken off. a, The frontal muscle, b. Temporalis and temporal artery, c, Orbicularis palpebrarum, d, Levator labii superioris alseque nasi, e, Levator anguli oris, f, Zygomaticus, g, Depressor labii inferioris. h, Depressor anguli oris, i, Buccinator, k, Masseter. 11, Parotid gland, m, Its duct, n, Sterno-cleido-mastoideus. o, Part of the trapezius, p, Sterno-hyoideus. q, Sterno-thyroideus. r, Omo-hyoideus. s, Levator scapulee. 11, Scaleni! u, Part of the splenius. Fig. 3. The Muscles of the Face and Neck in view after the exterior ones are taken away. a a, Corrugator supercilii. b, Temporalis, c, Tendon of the Levator palpebral superioris. d, Tendon of the orbicularis palpebrarum, e, Mas- seter. f, Buccinator, g, Levator anguli oris, h, Depressor labii superi- oris alseque nasi, i, Orbicularis oris, k, Depressor anguli oris. 1, Muscles of the os hyoides. m, Sterno-cleido-mastoideus. Fig. 4. Some of the Muscles of the Os Hyoides and Submaxillary Gland. a, Part of the masseter muscle, b. Posterior head of the digastric, c, Its anterior head, d d, Sterno-hyoideus. e, Omo-hyoideus. f, Stylo-hyoid- eus. g, Submaxillary gland in situ. Fig. 5. The Submaxillary Gland and Duct. a, Musculus mylo-hyoideus. b, Hyo-glossus. c, Submaxillary gland re- moved from its place, d, Its duct. Plate VII. Fig. 1. The Muscles immediately under the common teguments on the posterior part of the body, are represented on the right side; and on the left side the Muscles are seen which come in view when the exterior ones are taken away. EXPLANATION OF THE PLATES OF THE MUSCLES. 367 Head.—A A, Occipito-frontalis. B, Attollens aurem. C, Part of the orbicularis palpebrarum. D, Masseter. E, Pterygoideus internus. Trunk.—Right side. F F F, Trapezius seu cucullaris. G G G G, Latis- simus dorsi. H, Part of the obliquus externus abdominis. Trunk.—Left side. I, Splenius. K, Part of the complexus. L, Le- vator scapula?. M, Rhomboides. NN, Serratus posticus inferior. O, Part of the longissimus dorsi. P, Part of the sacro-lumbalis. Q, Part of the semi-spinalis dorsi. R, Part of the serratus anticus major. S, Part of the obliquus internus abdominis. Superior Extremity.—Right side. T, Deltoides. U, Triceps exten- sor cubiti. V, Supinator longus. W W, Extensores carpi radialis longior and brevior. X X, Extensor carpi ulnaris. Y Y, Extensor digitorum com- munis. Z, Abductor indicis. 1, 2, 3, Extensores pollicis. Superior Extremity.—Left side, a, Supra-spinatus. b, Infra-spina- tus. c, Teres minor, d, Teres major, e, Triceps extensor cubiti. f f, Extensores carpi radialis. g, Supinator brevis. h, Indicater. 1,2,3, Ex- tensores pollicis. i, Abductor minimi digiti. k, Interossei. Inferior Extremity.—Right side. 1, Gluteeus maximus. m, Part of the Gluteeus medius. n, Tensor vagina? femoris. o, Gracilis, p p, Ad- ductor femoris magnus. q, Part of the vastus internus. r, Semimembra- nosus, s, Semitendinosus. t, Long head of the biceps flexor cruris, uu, Gastrocnemius externus seu gemellus, v, Tendo Achillis. w, Soleus seu gastrocnemius internus. x x, Peronseus longus and brevis. y, Tendons of the flexor longus digitorum pedis; and under them * flexor brevis digitorum pedis, z, Abductor minimi digiti pedis. Inferior Extremity.—Left side, m, n, o, p p, q, r, s, t, v, w w, x x, y, z, Point to the same parts as in the right side, a, Pyriformus. b b, Gemini. cc, Obturator internus. d, Quadratus femoris. e, Coccygseus. f, The short head of the biceps flexor cruris, g g, Plantaris. h, Popliteus. i, Flexor longus pollicis pedis. Fig. 2. The Palm of the Left Hand after the common Teguments are removed, to show the Muscles of the Fingers. a, Tendon of the flexor carpi radialis. b, Tendon of the flexor carpi ul- naris. c, Tendons of the flexor sublimis perforatus, profundus perforans and lumbricales. d, Abductor pollicis. e e, Flexor pollicis longus. f, Flexor pollicis brevis. g, Palmaris brevis. h, Abductor minimi digiti. i, Ligamentum carpi annulare, k, A probe put under the tendons of the flexor digitorum sublimis; which are performed by 1, the flexor digitorum profun- dus, m m m m, Lumbricales. n, Abductor pollicis. Fig. 3. A Fore-View of the Foot and Tendons of the Flexores Digitorum. a, Cut extremity of the Tendo Achillis. b, Upper part of the astragalus. c, Os calcis. d, Tendon of the tibialis anticus. e, Tendon of the extensor pollicis longus. f, Tendon of the peroneus brevis. g, Tendons of the flexor digitorum longus, with the nonus Vesalii. h h, The whole of the flexor digitorum brevis. 368 EXPLANATION OF THE PLATES OF THE MUSCLES. Fig. 4. Muscles of the Anus. a a, An outline of the buttocks, and upper part of the thighs, b. The estes contained in the scrotum, cc, Sphincter ani. d, Anus, e, Leva! tor am. ff, Erector penis, gg, Accelerator urina?. h, Corpus caver- nosum urethra?. K ^aver Fig. 3. Muscles of the Penis. T«lbe^,iLh'P°int,heSame,3i"Fi^4- «• Sphincter ani. gg, PART IV. OF THE GENERAL INTEGUMENTS, OR OF THE CELLULAR MEMBRANE, AND THE SKIN.* CHAPTER X. OF THE CELLULAR MEMBRANE. That substance which is situated between the skin and the muscles, which is insinuated between the different muscles, and between the fibres which compose them; which also connects the different parts of the body to each other, is denominated the Cellular Membrane, or Tela Cellulosa. * The integuments of the body consist of the skin or dermoid tissue, and of that portion of the common cellular tissue which is subcutaneous, and seems to con- nect the skin, to the subjacent parts. The cellular tissue is loose and elastic, and by this simple arrangement, the skin is loosely connected to the muscles, and not forced to follow them rigidly in their contractions; thus, the roundness of the sur- face and the smoothness of the skin, is in a great measure preserved. The skin is directly continuous in the mouth, nares, urethra, vagina, anus, and external au- ditory meatus, with the mucous membranes, lining the interior of all the cavities of the body. The continuation or conversion of one into the other at these orifices, is so gradual as to be almost insensible, as will be more carefully shown under the head of mucous membrane. For this reason, by many of the French anatomists, the skin is called the external tegumentary membrane, and the mucous membrane the internal tegumentary membrane. The basis or derma of the two tissues being considered with some modification the same, the cuticle analogous to the undried mucous of the latter membrane, the papilli and sebaceous glands of the skin, to the villi and follicles of the latter membrane. This division into two membranes is not new; it may be traced to the time of Galen, but wc are indebted for its re-introduction to science, principally to Bonn, and Bichat. The physiological and morbid sympathies of the two membranes have been long known, as being more intimate, than that which exists between any two thoroughly distinct tissues in the human body.—p. 370 THE CELLULAR MEMBRANE. As it extends over the whole of the body, and is most inti- mately connected with the skin, it is considered as one of the integuments, although it is found in great quantities in some of the internal parts. It appears to be composed of membranous laminae, exquisitely fine and delicate in their structure, which are so connected to each other that they compose cells or cavities of various forms and sizes. When these cavities are empty, ihis arrangement of the cellu- lar membrane is not apparent; but when they are distended by water or air it is very evident. The laminae which pass from one contiguous part to another are of different lengths, according to the motions performed by the different parts; thus,, about the muscles and their tendons they are of considerable length, and between the coats of the eye they are very short. In some places, these laminae are compressed together, and form a dense membrane somewhat resembling tendon; but whenever they are separated from each other, they appear pel- lucid, and extremely delicate. —The cellular tissue serves as the connecting medium of other tissues, and might very properly be called the connecting tissue. In the fcetus, when all the parts are soft, and as yet un- formed, it presents the aspect of mucus, filling up the interstices of the other nascent organs. Hence Bordeu and Meckel, have denominated it the mucous tissue, and supposed that its cellular and membranous structure, was produced mechanically by the traction of surrounding air, or the infiltration of fluid. The term mucous, however, is inappropriate and confusing, and applicable only to the nascent state of the organ; it has been proved by mi- croscopical investigations to be erroneous when the develope- ment of the tissue is complete. —The ultimate elements of all cellular tissue are fibres, not merely globules or lamellae. These primary fibres, are among the most minute constituent elements of the human body. Their diameter, according to the microscopical measurements of Jor- dan, is the titJ7tn Part °f an English line. They are transparent, THE CELLULAR MEMBRANE. 371 and yield gelatine on boiling, in which respect they correspond with the primitive fibres of tendons. Treviranus has recently asserted from microscopical observations, that they are hollow cylinders, which terminate by one extremity in the minute lym- phatic vessels.* This, which possibly may be the case, and is supported by the opinion of Fohman, wants confirmation from other observers. —These fibres of the cellular tissue, are united so as to form lamellated membranes which cross each other in all directions, and produce an irregular interlacement, constituting a series of cells, which communicate together.— These lamina?, when ih a healthy state, appear to have no sensibility; but so many nerves pass through them, that pain is generally felt when incisions are made in the cellular mem- brane. No vessels can be seen in their composition when they are free from disease, although many pass through them. On this account they have been considered by some very respectable physiologists as inorganic; but there are good reasons for regard- ing this sentiment as erroneous. If a portion of cellular membrane, in the living subject, be brought into view by a surgical operation or a wound, and be allowed to remain some time covered by an emollient cataplasm, or a soft plaster, a complete change of colour will gradually take place; it will become uniformly red, in consequence of the great number of minute vessels into which blood has penetrated during inflammation; and granulations will form on its surface. These vessels must have existed previously in the sound state of the membrane, and conveyed a transparent fluid; although no structure of this kind was visible. This single fact therefore proves completely its organization. In some parts of the body, this cellular membrane appears to be moistened by a small quantity of fluid, or halitus, in its cells; which seems merely sufficient to keep it soft and flexible. In other places it is loaded with fat. » Mailer's Archives for 1834, p. 410. r Vide Breschet, sur le Systeme Lymphatique, etc. Paris, 1836. 372 THE CELLULAR MEMBRANE. There is great reason to believe that the fat is contained in cavities which are somewhat different from the ordinary cavi- ties of the cellular membrane. The cells or cavities which contain the moisture or halitus communicate with each other, over the whole body. Thus, air insinuated into the cellular membrane exterior to the pleura, in consequence of a fractured rib, will be diffused over the whole body; and produce the disease called emphysema. In a patient who is affected with that species of dropsy called anasarca, a portion of the fluid will be effused in the head and upper parts of the body, after he has passed a night in bed in a horizontal po- sition ; but after he has been in an erect position for some time, the fluid will be accumulated in the legs and feet, or most de- pending parts of the body, in consequence of its gravity. It is well known in dissecting-rooms, that the effused water may be completely discharged from anasarcous subjects, by making incisions in the feet and placing the subject erect. Blood effused in the cellular membrane is sometimes dispersed in the same way; an ecchymosis often appears in the eyelids in consequence of a contusion on the upper part of the head; and similar appearances occur in almost every part of the body, in consequence of effusion of blood at a distance from them. The fat or adipose matter is not diffused in this manner: wherever it is first effused, it remains, uninfluenced by gravity, or the ordinary pressure. Fat is not observed in every part of the body; it is never seen in the cellular membrane of the eyelids; of the penis; of the lungs; or of the parts within the cranium; as well as of se- veral other places. The inconvenience which would result from the accumulation of fat in these places is very obvious: and it is equally certain that the cellular membrane in them must be different from that in which fat is produced. From these peculiar circumstances, relative to the adeps, it has been inferred, that there was a peculiar apparatus for the production and retention of fat, superadded to the cellular mem- brane ; and some anatomists, with a view to precision, have called the part containing fat, Adipose Membrane, and the other ADIPOSE TISSUE. 373 part Reticular Membrane.* They state that in dropsical sub- jects, who are much emaciated, the membrane, which in a healthy state contained adeps, is more ligamentous than the or- dinary cellular membrane. It seems to be proved, by reasoning, that there must be a con- siderable difference between these different parts of the cellular membrane ; but it ought to be observed that those parts of the omentum which are especially appropriated to the production of adeps, do not exhibit any peculiarity of structure. This adipose substance is distributed in unequal proportions in different parts of the body. In corpulent persons there is a con- siderable quantity of it, immediately under the skin, and espe- cially under the skin of the abdomen. It is also between the muscles, in the orbits of the eyes; in the omentum and mesentery; in the joints and the bones; as well as about the kidneys, and heart also, in elderly persons. In the foetus, and for some time after birth, it appears to be con- fined to the parts immediately under the skin, but it soon be- comes more diffused. —The fat in the adipose tissue, is unor- ganised, and at the common temperature of the human body, is almost fluid. On the latter account it produces the softness and smoothness of the exterior, particularly obvious in obese indivi- duals. Its use, probably, besides contributing to the roundness and softness of the exterior, is in part to protect the body against the extremes of heat and cold, in consequence of its being a bad conductor of caloric. It may be considered also, as a de- posit of nutriment held in reserve, to be dissolved and taken up again by the absorbents, during fasting, or when any wasting disease has impaired the functions of nutrition.— It is observed by dissectors that there are no subjects, how- ever emaciated, who are entirely free from fat; except those who have been affected with anasarca. The cellular membrane has been already observed to form granulations very promptly; and it has been asserted that the granulations, which arise from all the different parts of the body r See remarks on the cellular membrane, &c, by Dr. W. Hunter, in the Lon- don Medical Observations and Inquiries, vol. ii. vol. i. 32 374 CELLULAR TISSUE. when wounded, originate from the cellular membrane in those parts. Whether this proposition be true or not, to the extent above stated, it is a fact that granulations, in some instances, seem to have a cellular structure; as the following case will prove. A patient, with a compound fracture of the leg, which was attended with a large wound, covered with luxuriant granula- tions, was attacked with an cedematous swelling of the limb, which increased suddenly to a great degree. While this was going on, the granulations on the surface of the wound tumefied with the limb; and, upon examination, appeared somewhat pel- lucid, with an effused fluid indenting by pressure, precisely as the skin was indented. The cellular membrane appears to have a most intimate con- nexion with the skin; and cannot be completely separated from it by dissection. It is said that in certain cases of disease, where it is reduced to a slough, while the texture of the skin remains unchanged, as in some species of anthrax or carbuncle, this sepa- ration may be completely effected. In such cases the under surface of the skin will appear to be composed of pits or excava- tions, which penetrate very deep into its substance, and were occupied by the cellular or adipose membrane while it was in its natural condition. THE SKIN. 375 CHAPTER XI. OF THE SKIN. The skin is composed of three dissimilar lamina, which are denominated the Cuds Tera, the Rete Mucosum, and the Cuticula. Of the Cutis Vera. The innermost of the above-mentioned lamina is much more substantial than the others, and therefore is called Cutis Vera. It is an elastic, dense, and strong membrane; which contains in its texture a large proportion of fibres that appear to be tendi- nous, and are woven together in an intricate manner.* Blended with these fibres is an immense number of vessels which enter into the texture of the skin; these vessels do not generally convey red blood, and therefore they are not very visible; yet they may be readily brought into view, by the appli- cation of rubefacients during life; and by fine injections, in the dead subject. Their existence is also demonstrated in the vigor- ous infant, at birth, by the universal redness of the skin, which is observable at that time. Nerves are also distributed to every part of the skin. They can be traced to it very easily; and as there is no part of the skin into which the finest needle can be pushed without pain, it is certain that their distribution must extend to every part. It is highly probable that the processes of absorption and ex- halation are effected by small vessels which originate or terminate on the surface of the skin, and of course form a part of its texture. The skin, thus constructed, extends over the whole of the * These fibres hold a middle station between ligamentous and common cellular tissue, and are supposed to consist of the latter in a very compacted state. The meshes, which they leave when woven together, allow of the introduction of vessels and nerves to the papilla? and to the outer surface of the catis vera.—p. 376 CUTIS VERA. body, and is continued into those cavities which open upon the surface, as the mouth, nose, &c, although its texture changes im- mediately upon its reflection. It varies in thickness in different parts ; thus, it is thicker on the back than the front of the body. It is thin on the insides of the arms and leg, where opposite surfaces touch each other.* It is, in general, thinner in women than in men. The elasticity of the skin is made evident by its yielding to distention, and returning to its usual size; as in pregnancy, dropsy, &c.; but it is particularly demonstrated in some cases of par- turition, when the skin of the perinaeum stretches immensely, and, after labour, very quickly recovers its size. The external surface of the skin is very generally divided by superficial grooves or sulci, into small spaces of various angular forms; most commonly rhomboidal. On the palms of the hands and soles of the feet, instead of these figures, we perceive the whole surface composed of furrows and ridges, which, in some places, are rectilineal, and, in others, oval and spiral. There are also a number of depressions or grooves which seem formed to accommodate the various articulations, particu- larly about the fingers and toes. There are other furrows, occasioned by muscles, as those on the forehead : and some depend on the subjacent cellular mem- brane. On the external surface of the true skin, when the two exterior laminae are removed, many papillae are to be seen. They differ in size in different parts of the body; they are vascular, and, on the ends of the fingers, appear like villi, when examined by a magnifying glass. There are many perforations or pores to be seen on the skin with the naked eye, which are probably the ducts of sebaceous glands, and the passages which transmit hairs. Other pores, different from either of these, are to be seen when magnifying glasses are used ; as those on the fingers; these probably are the * The thickness on the back, is about double what it is on the front of the body.—p. SEBACEOUS FOLLICLES. 377 exhaling or absorbing pores, but their connexion with the vessels which perform these functions has not yet been demonstrated. The internal surface of the skin, when carefully dissected from the subjacent cellular membrane, in a subject of ordinary corpulency, appears to have some adipose substance in its tex- ture; but, as has been already mentioned, when the cellular membrane is destroyed, these portions of adipose matter disap- pear, and the surface of the skin appears pitted. It is probable (hat this connexion of the cellular membrane and skin may oc- casion that delicacy of skin which appears in some hydropic patients. In some places on the under surface of the skin are small glands called miliary, from their resemblance to the millet seed; these glands are supposed to secrete a sebaceous matter, but they are not so general as has been supposed. There are sebaceous follicles or ducts, which open on the ex- ternal surface of the skin, and contain an oily substance, which, sometimes, has the consistence of suet or tallow; when these ducts are filled with sebaceous matter, their orifices are often covered by a black substance, which accidentally adheres to the surface of the matter, and forms very small black spots in the skin. These often occur on the nose and ears, and may be removed by pressing out the sebaceous substance, which rises up in the form of small worms. Sometimes this secretion accumulates in the ducts in such quantities, that it forms small tumours in the skin. —Fig. 23, is a portion of skin cut vertically from the nose of an old man, in order to show the Fig. 23. sebaceous follicles and their ducts, which are <3F-*gs=Sap35gaa, magnified to about double their natural size. "^^P^^^t They are found in all parts of the body, with the exception of the palms of the hands and soles of the feet; but in many parts only become visible to the naked eye, in diseased conditions of the skin. They are most numerous in the face, behind the ears, and in the arm-pits and groin. There is a strong analogy between them and the follicles of mucous mem- branes. 32* 378 SEBACEOUS FOLLICLES. Fig. 24. —Fig. 24, represents the orifices of the sebaceous glands, as they are seen in the nose, after it has been deprived of its epidermis. Each follicle consists of a simple depression or doubling inwards of the cutis vera, which becomes more vascular and thin where it forms the walls of the follicle. The sebaceous follicles, according to E. Weber, are much larger and entirely distinct from those forming the bulbs of the hairs. The latter, too, are situated more deeply, being often found in the subcu- taneous cellular tissue. They differ also, according to him, in their structure; each sebaceous follicle being composed of four or five compartments or cells agglomerated together. They are also larger than those of the bulbs of the hairs; the largest diameter of a sebaceous gland, (the transverse,) observed by Dr. Weber, was three-fourths of a line.— Muscular fibres have been supposed by some persons to exist in the skin, but such fibres have never been demonstrated in it. The skin of the scrotum is often much contracted, but the fibres which produce this effect are very visible in the cellular mem- brane, and have a muscular appearance. Although the skin is not muscular, it sometimes changes its appearance in a surprising manner. When the surface of the body is suddenly exposed to cold, or when the chill of fever exists to a considerable degree, the skin will contract very sensibly, and, at the same time, a great number of conical papillae will project from its surface. This constitutes the Cutis Anserini; and is supposed to be produced by a sudden contraction of the vessels in the skin, which forces out their contents, and of course, diminishes its bulk; while the papillae do not contract in the same degree, and, therefore, are somewhat projected. When the skin is free from disease, the two exterior laminae, RETE MUCOSTTM. 379 (Cuticle and Rete Mucosum,) maybe separated from it completely, after maceration or putrefaction, and the surface will appear smooth; but, in an inflamed skin, a net-work of vessels has been injected; which is considered, by Mr. Cruikshank* as an ad- ditional lamen. In this lamen, the pustules of small-pox originate. When the skin is injected, they appear to be formed at first by very small vessels, arranged in a radiated manner, with a white uninfected substance in the centre, which is supposed to be a slough, occasioned by the irritation of the variolous matter. Mr. (ruikshank, after removing this lamella, was able, by continued maceration of the same skin, to separate another, which was also vascular. It is to be observed that this skin had been preserved for some time in spirits, and was macerated in putrid water a week during the heat of summer, before the first lamella was removed. The colour of the healthy skin is invariably white, when all the lamellae exterior to it are removed. This is the case not only with the European, but with the blackest African, and the people of all the intermediate colours. The variety of colours in the human species depends upon the lamella next to the cutis, which is now to be described. Of the Rete Mucosum. Immediately in contact with the external surface of the cutis vera is a thin stratum, of a pulpy or mucilaginous consistence, which appears to be spread uniformly over it, but cannot be de- tached without deranging its own texture.f It can be best examined after the cuticle is raised in a blister. In this case it appears like a pulpy substance, spread upon a membrane of a soft and delicate texture. This is the Rete, or Corpus Mucosum. In this pulpy substance resides the pigmentum, or colouring matter, which gives the peculiar complexion to the different races of men. The cutis vera is white, and the cuticle is nearly * See Experiments on Insensible Perspiration, &c. by W. Cruikshank. t It has been asserted that the rete mucosum of the scrotum can sometimes be exhibited in a separate state. 380 RETE MUCOSUM. transparent in them all; but this substance is black in the negro: copper-coloured, yellow, or tawny, in many of the Asiatics; and yellow, with a tincture of red, in the aborigines of America; while it is transparent, or whitish, in the people of Europe and their descendants. It can therefore be best examined in the negroes; and if it be inspected immediately after the cuticle of a blister is removed, it will appear as above described, with a black matter diffused through it. The particular structure of this substance has not been ascer- tained, although anatomists have paid a good deal of attention to it. It is generally believed by them that no vessels can be in- jected in it; but Dr. Baynham of Virginia, while he was en- gaged in anatomical pursuits in London, made a preparation which excited the attention of the British anatomists, on account of its particular relation to this subject. He injected one of the lower extremities, the os femoris of which was diseased with an exostosis; and with a view to an examination of the lamina of the skin, he removed a portion of it from the leg ; and after immersing it a few seconds in boiling water, to thicken the lamina, he macerated it in cold water for some days. Upon separating the cuticle, after this treatment, he discovered a texture of vessels on the surface of the cutis vera, which was distinct from the cutis itself. This has often been mentioned as injection of the rete mucosum. It is to be regretted that Dr. Baynham, who is particularly qualified to decide, has not published his opinion on the subject. Mr. Cruikshank, to whom he afforded the most satisfactory op- portunity of examining his preparation, believes that the afore- said vessels were not a part of the rete mucosum ; but that the rete mucosum was to be seen on the epidermis, (being raised with it when it was separated from the cutis,) while this texture remained on the surface of the cutis. He considers these vessels as belonging to the additional lamellae already mentioned, of which he says Dr. Baynham is the discoverer. There is therefore every reason to believe that there is a tex- CHANGE OF COLOUR. 381 ture of vessels, either in the rete mucosum, or between the cutis vera and the rete mucosum. After putrefaction, or maceration for a long time, the cuticle separates readily.from the cutis vera; and the rete mucosum sometimes adheres to the skin, and sometimes to the cuticle. If the parts are much softened by putrefaction, the rete mucosum can be washed away, like the pigmentum nigrum of the eye; leaving the cutis white, and the cuticle nearly transparent. In the negroes the black colour of the rete mucosum is greatly diminished, on the palms of the hands, and soles of the feet, and under the nails; but it is perceptible. It is said that the black colour does not appear in the cicatrices of the blacks. This is the fact with respect to recent cicatrices; but those of long standing are often dark-coloured, although not so black as the original skin. The pits of the small-pox in their skins, although white at first, become finally as dark as the original surface. In Europeans and their descendants the colour of the rete mu- cosum becomes darker, as they are more exposed to the air and the rays of the sun; and soon changes again to its original fair- ness, by confinement to the house. In negroes the skin loses some of its deep glossy black colour during the winter season of cold climates, and recovers it again in summer. The rete mucosum sometimes undergoes very important changes; there have been several instances in the United States, where large portions of the skin of the African have changed from black to white; owing probably to an absorption of the black pigment from the rete mucosum; or, perhaps, to an ab- sorption of the rete mucosum itself. There is now in Philadelphia a female, between thirty and forty years of age, in whom this process is going on. One of her parents was a negro and the other a mulatto ; and her ori- ginal complexion accorded with her origin. But a change of colour began during her childhood, in small spots, which have gradually increased so much, that at this time the whole of her body and limbs are nearly white, with the exception of her hands and feet. A large proportion of her face is also white, and the remainder of it much lighter than it was originally. At this 382 CHANGE OF COLOUR. time, some part of her face has an unnatural whiteness; but the skin of her forearms appears like that of a European in a per- fectly healthy state. This change of colour is attended with no unusual sensation ; so that if she did not see the alteration, she would not suspect that her skin was any way different now from what it had originally been. She does not appear sensible that the white parts are more susceptible of irritation from the rays of the sun than they were originally; but they are so much covered by her dress that the experiment has not yet been fairly made. The first appearance of a change is slight diminution of the dark- colour;'this change goes on gradually, and then small spots appear, which are perfectly white. They gradually in- crease, and run into each other, and thus a large white spot is formed. In a former case, where this process had gone on to a great extent, it is said that the black pigment was again deposited, and the skin resumed its original blackness. These circumstances in negroes have been considered as great deviations from the ordinary course of nature, but a process very analogous to it sometimes goes on in persons who are white. Thus, there are some in whom the skin becomes much browner than natural in some parts of the body, particularly on the arms; and in these brown portions, spots are formed which are much more white than the natural colour of the skin. In such cases there appears to be a deposition of colouring matter in the rete mucosum of the brown places; while the white spots are rendered more white than natural, either by an absorption of the rete mucosum, or by a deposition of whiter matter in it. The colour of the rete mucosum sometimes undergoes a tem- porary change in particular places. Thus, at a certain period of pregnancy, a dark circle forms round the nipple. In some cases, where the peculiar whiteness occurs, the skin becomes very susceptible of irritation from the rays of the sun ; so as to be blistered, if exposed to them for a short time; this circumstance renders it probable that the colouring matter in the rete mucosum of the blacks, was originally designed to pro- ALBINOES. " 383 tect their skins from the very powerful rays of the sun to which they are exposed. There are some persons to be found, amongst most of the dif- ferent races of men, who are born with this peculiar whiteness of the whole skin, which continues during life. In these per- sons, the hair has a remarkably white colour, and the eyes are without the pigmentum nigrum. They appear to be in a state of imperfection, and are unable to endure the ordinary light of day. They are generally designated by the epithet of Albinoes. The texture which exists between the cutis vera and the epi- dermis is probably the principal seat of several important cuta- neous diseases; as the Scarlatina Pemphigus, &c* and from what has been stated, there is good reason to believe that the small-pox, also, commences in it. It is, therefore, much to be wished that its structure was more precisely ascertained. —The variety of diseases which have their seat in the skin, as well as the important functions which it exercises in health, have led modern anatomists to believe that it was formed of more than the three layers, that Malpighi assigned it, and induced them to investigate its structure with scrupulous care. From the innate difficulties of the subject, its anatomy cannot as yet, however, be considered as satisfactorily made out, for its inves- tigators have too frequently resorted to hypothesis, when the means of demonstration failed them. The doctrines of the learned and judicious Malpighi, which have been admirably de- tailed above, were generally admitted by anatomists, till M. Gaultier,f a mere student of medicine, full of zeal and candour * In severe cases of the scarlatina, at the termination of the disease, large por- tions of the cuticle are sometimes detached from the cutis, so that several practi- tioners have seen the whole cuticle of the hand come off like a glove. As the texture of the cutis does not appear to be altered in these cases, and the cuticle is also unchanged, the cause of this separation must exist in the intervening struc- ture which connects them. t Gaultier, whose opinions have been adopted in the main by Beclard, Blandin, Cloquet and others, would, if he had lived, most probably done much towards sim- plifying and perfecting his views. Appointed army surgeon immediately after his graduation, he fell a victim to the disasters of the Russian campaign. The in- vestigation has, however, been taken up by Dutrochet who extended it to the skins of quadrupeds, by several of the German and Italian anatomists, and lastly by Breschet and Roussel de Vauzeme. The last have made it a subject of elaborate 384 STRUCTURE OF THE SKIN published in 1813 his researches on the skin, which, though im- perfect in some respects, went far towards establishing its real structure. —The rete mucosum, which Malpighi considered a simple coat- ing of mucus, between the cutis vera and cuticle, a sort of varnish covering the papillae, was considered by Bichat as essentially formed of vessels, and divided by him into two vascular layers, one over the other, in the outermost of which was placed the colouring matter or pigment But Gaultier, from his observation of the skin of the negro, and Dutrochet from that of quadrupeds, consider it composed of many distinct parts. Gaultier selected for observation the skin of the heel of a negro where the cuticle is thickest, but which he thought differed in no other respect from the skin in other parts of the body. —This figure is a magnified representation of a section of the Fig. 25. skin cut obliquely in regard to its J thickness, and transversely to the -4- lines formed by the papillae. In 2 this, according to Gaultier, we see Jr-i at a, the lower surface of the derm, or cutis vera. 1, The prominences or asperities of the derm, form- ing the papillae, each one with a slight depression upon the top. 2, Immediately above these and continuous with them we see a series of vascular fasciculi surmounting these prominences, called bloody pimples, (bourgeons sanguins.) 3, The tunica Fig. 26.* albida profunda, covering these papillae upon their top and sides, and united to the upper surface of the derma, and composed entirely of white vessels, (serous capilla- ipippi I""1" ries.) 4, Gemmules; a sort of membrane so named microscopical research, not only in man, but in the whale and many of the larger animals. The views of Gaultier thus modified and improved, are well deserving of study as the most satisfactory yet given, though, from the doubt which is always attached to microscopical observations, they must be looked upon rather as the probable than the proven structure.—p. * Fig. 26—Is a representation of the skin, and the basis of the papillffi, the latter surmounted by the vascular villi or fasciculi, (bourgeons sanguins.) The space between these fasciculi is filled up, in the natural state of the parts, accord- ing to Gaultier, with the tunica albida profunda. ACCORDING TO GAULTIER. 385 from its undulations, excavated on its internal face, which covers in the tunica albida profunda. This is the seat of the colouring matter of the skin, and each one receives two of the bifid tops of the papillae, called bourgeons sanguins. 5, Tunica albida superfi- cialis, which covers over the gemmules, and also formed entirely of white vessels. 6, The external face of the skin, which is only the dried surface of the tunica albida superficiaHs, or the proper epidermis. Gaultier considers four of these layers as belonging to the rete mucosum; the perpendicular vascular fasciculi (bour- geons sanguins,) the gemmules Fig. 27.* and the two white tunics. ?, 3 imnir~ mmmnmM —The first and second of these MilgiiWiMwimisWiillp four, correspond with the two >nH*^,™™^^mm^mmMmiM0m vascular layers which Bichat assigns to the rete mucosum; and the views of Gaultier differ from this writer's in his adding two more tunics, tun. albid. profunda, and tun. albid. superficiaHs. But the vascular fasciculi, as Dutrochet and Beclard have asserted, be- long to the cutis vera, and form a part of the proper papillary body; and were probably the parts injected by Baynham and Cruikshank—thus leaving the rete mucosum formed of three layers. Thus modified, Gaultier's researches have been adopted by many writers. —But there were not wanting others who entertained different views. Gall believed the rete mucosum a nervous expansion for the reception of tactile impressions; an opinion purely hypotheti- cal and erroneous; Chaussier, that the skin was composed of but two parts, the dermis and epidermis, and that that, which had been called the rete mucosum was probably a part of the dermis; Blandin,f that the rete mucosum, consisting of three layers ac- cording to Dutrochet placed between the papillary bodies and the epidermis, had neither vessels or nerves, was a product of secretion from the papillae, like the epidermis, and formed in fact a second epidermis thicker and softer than the external, and that it had no more vitality than the hair and nails. * F»g- 27, is a representation of the derm, or cutis vera, with a line of promi- nences on its upper surface, constituting the basis of the papilla. t See Anat. Generate of Bichat. Paris, 1831.—p. vol. 1. 33 386 STRUCTURE OF THE SKIN —Breschet and Roussel de Vauzeme,* have in this uncertain and imperfect state of our knowledge, endeavoured with the aid of the scalpel and the microscope, to determine positively its struc- ture. Their researches have been extended not only to the skin of man, but to that of whales and others of the cetaceas. The dis- coveries which they allege to have made are surprising, and though their researches appear to have been made with much labour and ingenuity, their confirmation or overthrow must de- pend upon the investigation of others equally familiar with the same instruments. —But it must not be forgotten that such high magnifying pow- ers as they have used, expose the most wary and honest observer to optical illusions. This cause led De la Torre, to assert that the globules of the blood were annular. —According to these writers, the skin consists of but two layers. The derm, or cutis vera, and an external layer, which they call indifferently epidermis, corneous matter, corneous tissue, or epi- dermic layers, and which comprises the rete mucosum arid epi- dermis of other writers, which they consider composed of the same substance, mucus, in a greater or less state of desiccation. It is, however, composed of many distinct parts, not arranged in the form of layers. Fig. 28, represents an imaginary scheme or plan, in which they have placed together the constituent parts of the skin, the existence of which they had proved separately under the microscope. —Thus, a is the derm, b, The corneous or horny epidermic matter, c, The vessels and nerves which go out from the der- mis, d, Space filled up by their capillary branches, e, Ner- vous or tactile papillae. The diapnogenous, or sudoriferous ap- paratus, composed of a glandular parenchyma, /, and of spiral sudoriferous canals, g. The glandular or secretory organ is in- closed in the substance of the skin, and the canals pass up be- tween the papillae and open obliquely on the surface of the epidermis, constituting the microscopical orifices, from which we * Nouvelle recherches sur la structure de la peau, par G. H. Breschet and Rous- scl de Vauzeme.—Paris, 1835.—p. ACCORDING TO BRESCHET AND ROUSSEL DE VAUZEME. 397 Fig. 28. see the sweat exuding on the palms of the hand, and soles of the feet, h, The inhaling apparatus, or absorbent canals, which re- semble in many respects the lymphatic vessels : they are situated in the corneous matter or rete mucosum; they are seen to com- mence under the most superficial layer of the corneous matter which forms the cuticle; no mouth or orifices, and it is impossi- ble to say, whether they commence in the form of a cul de sac or not. They pass down between the papillae, by the side of the sudoriferous canals, and communicate with a net-work of ves- sels, which they believe to be lymphatics mixed up with veins, spread upon the surface of the derm.* i, The organs which secrete the mucus of which the rete mucosum and cuticle is formed, or blennogenous apparatus; this consists of a glandular parenchyma situated in the thickness of the derm, and of short excretory canals k, which deposit the mucous matter between the bases of the papillae. The chromatogenous organs or glands, which secrete the colouring matter or scales, run parallel with, * The existence of these inhalent vessels, from some observations I have made with a very powerful microscope, I should consider extremely doubtful.—p. 388 STRUCTURE OF THE SKIN and immediately below the grooves on the surface, and between the papilli, which they are also placed a little below. The ends of them, marked by a collection of dots, can of course only be seen in the plan, in consequence of their running parallel with the grooves, and between the parallel ranges of papillae. —They consist of a glandular parenchyma, receiving an abun- dance of capillary vessels from the derm below, and possess- ing excretory canals above, which throw upon the surface of the derm, the colouring principle, which is mixed with the soft and diffluent corneous or mucous matter, thrown up by the blennogenous apparatus. From this mixture results the pre- tended rete mucosum of Malpighi, and the epidermis or cuticle. From this apparatus is also produced, they think, the horns, scales, spines, bristles, hair, wool, hoofs, nails, etc. of different animals. It is solidified in successive couches, to the right and left, as seen in the section across the grooves, I; but in the longi- tudinal section m, these layers present a series of straight lines one above another like the leaves of a book. —In consequence of this arrangement, the corneous matter, when macerated, throws off layer after layer. The superior face of the epidermis presents grooves, as represented at n, which cor- respond to the interpapillary grooves of the derm, o, Are the prominent ridges in the cuticle formed over the papilli, separated by transverse grooves, p, at the bottom of which are found the pores of the sudoriferous canals, e, Are the vessels and nerves which enter into, or go out from the derm, d, An inter- val filled up by capillary filaments. Of the Derm. —The external surface of the derm, is lined by a very thin ad- herent membrane, which is reflected over the tops of the papil- lary bodies and forms their neurilema. The horny or epidermic matter is secreted in the grooves between the papilla, is moulded around all the inequalities, the form of which is exactly impressed on all the layers of the epidermis. In serpents, the derm, has a singular arrangement; it is elevated in imbricated projections, ACCORDING TO BRESCHET AND ROUSSEL DE VAUZEME 399 covered by a thin layer of epidermis; these are called scales. In fishes, on the contrary, the surface of the derm is smooth, and the scales are formed only of the horny matter. The derm is a membrane, the fibres of which are solidly interlaced together, with interstices for the passage of vessels, nerves and canals, and in which are lodged many organs, as has been shown in the plan, page 387.* Of the Papillary Body, or Neurothelic Apparatus.} —This consists of a series of little prominences on the upper surface of the derm, cleft at the top into two portions, each of which is composed of a bundle of nerves and vascular filaments, bourgeons sauguins of Gaultier. The form of each papilla is that of a cone. The base is expanded in the upper surface of the derm, and its two prominences or villi, terminating in a rounded point, are received in the horny layers of the epidermis, like a sword in its sheath, (see page 390.) —The direction of the papilla is slightly oblique in the epi- dermic layers, as seen in Fig. 29.J The nerves are here seen passing up into the papilla through the dermis; the vascular branches which accompany them are not here represented. The papilla first gets a neurilematic covering from the upper * The method adopted by these writers for microscopical examination of the skin, was to take a piece of recent skin in which the vessels were distended by cadaveric accumulation of blood, or filled with injection. A portion from the heel is preferable. This is to be allowed partially to dry, and the thinnest possible transparent slice, cut off vertically. This is to be placed upon a piece of moist- ened glass and examined under the microscope with the use of a lamp and reflec- tor. In this way they were able readily to see, and isolate with curved cataract needles, all the vessels, nerves and glandular apparatus of the skin.—p. t From neuron, nerve, and thela, papilla.—p. I According to these writers the nerves, as they pass up from the under surface of the skin, become soft, flexuous, and capillary, and as they enter the villi on the top of the papilli, lose their neurilema, and are expanded in the form of pulp. They look upon the changes which the nerve undergoes, and upon the derm, villi, and epidermic covering, as so many parts necessary to constitute the perfect organ of touch: thereby assimilating it to the more complicated organs of sight and hear- ing.—Loc. cit. p. 15, et seq.—p. 33 * 390 STRUCTURE OF THE SKIN surface of the derm, and is there furnished with several layers of the epidermic horny matter, which Fig. 29* cover it like a hood. This horny co- vering is particularly thick at the heel, and serves to protect the papillae by deadening shocks, and resisting the ..c pressure of the weight of the body. The papillae are most numerous on the palms of the hands and soles of the feet, but are also scattered in other parts of the body.f Of the Sudoriferous or Diapnogenous Apparatus. —This consists of a gland, see Fig. 28, p. 387, placed in the substance of the dermis, near its inner surface, into which a great many capillary vessels run, and of a spiral duct which runs up through the horny layer sand opens obliquely through the outer epidermic crust by a slight depression or pore, on the back of the epidermic ridges, formed over the papillary bodies. These are the orifices from which the sweat exudes, and may be readily seen with a single lens of moderate magnifying power, on the palms of the hands, soles of the feet, nose, and other portions of the body. The obliquity of the orifice, gives it a valvular ar- rangement, like that of the ureters where they enter the bladder. In consequence of this the valve closes the orifice, when the epi- dermis is raised by cantharides, and the duct is broken off, so that the pores are not generally visible, which has occasioned some * Fig. 29, represents the apparatus which constitutes the organ of touch in man. a, Nerve entering into the dermis, where it becomes capillary, b, Its entry into the papilla, c, Neurilema furnished by the dermis, d, Proper envelope of the nerve, e. Corneous layers more or less thick, which form the organ of protection to the nerve. The capillary blood-vessels which pass up with the nerves are not here shown. t From their observations upon the papillae of the whale, these anatomists are disposed to believe that the nervous fibrils terminate at the top of the villi, by loops with one another, as Prevost and Dumas have shown them to do in other parts of the body.—p. ACCORDING TO BRESCHET AND ROUSSEL DE VAUZEME 391 anatomists, of great reputation, J. F. Meckel, Cruikshank, Blumen- bach, etc.^ to deny altogether the porosity of the epidermis, and to believe that the sweat passed by exudation or exosmosis di- rectly through its substance. In carefully elevating the cuticle from the subjacent coats, these ducts are visible as very fine trans- parent elastic filaments; the spiral being converted into straight tubes by the traction, and which W. Hunter, Bichat, and Chaussier, according to these writers, mistook for the exhalent and absorbent vessels.f Others supposed there were filaments of cellular tissue, uniting the epidermis to the subjacent layer.J The sudoriferous organs, which are exceedingly numerous, are probably the only exhaling organs of the skin. The Inhaling Apparatus. —This is properly an appendage of the absorbent system; and may be seen, according to these anatomists, with a lens of feeble magnifying power, or even with the naked eye, in raising the epidermis with proper precaution. They have not, however, been enabled to make out their anatomy satisfactorily. They describe them, see Fig. 28, as arising by isolated radicles from the under surface of the grooves of the epidermis, and not open- ing to the surface; the fluids which they take up getting into their cavities by previous imbibition through the outer cuticular covering. In passing downwards towards the derm, they are in company with the sudoriferous ducts, and in the substance of the derm, become continuous with the common absorbent vessels.^ * Beclard, was disposed to consider these pores as the orifices of the sebaceous glands, though he expresses himself doubtingly upon the subject, and says that the rout by which the sweat traverses the epidermis is entirely unknown.__p. t The existence of exhalent vessels, was a mere presumption of Bichat, and has never been demonstrated.—p. X Eichhorn has also observed these sudoriferous canals, and his description of them corresponds in many respects with that of Breschet. Memoire sur les *x- halations que se font par la peau, et sur la voies par lesquelles elles sont lieu; par Henri Eichhorn. Arch, de Meckel.—p. § The existence of these absorbent vessels immediately beneath the cuticle and on the upper surface of the dermis, has been demonstrated byTiedemann, Fohman, and Lauth. Breschet asserts the discovery of an additional structure, in his in- haling apparatus, arising in the corneous tissue.—p. 392 STRUCTURE OF THE SKIN Blennogenous Apparatus, —Or organs which, produce the mucous substance, which, in its first soft condition, forms the mucous body, heretofore known under the name of rete mucosum, and which, hardened upon the surface constitutes the horny matter of the epidermis. To see these well with the microscope, it is necessary to have a piece of fresh skin well injected with blood. There is then to be seen at the base of the derm, little reddish glands, irregular on the surface and grooved by blood-vessels. They are enveloped in cellular membrane and surrounded by a multitude of minute adipose vesicles. From the top of each of these glands as seen in Fig. „. 30,* passes up a duct, Fig. 30. ' f *\, which opens on the up- per surface of the derm in the grooves between a the papillae. Many capil- lary vessels adhere to the tube and the gland, and a vessel of conside- rable size enters the base of the latter. The mu- cous matter thrown on the surface of the derm by these organs, quickly unites with a colouring matter, from which results the different tints of the corneous or epidermic substance, hair, nails, scales, feathers, etc., in man and other animals. This colouring is formed by the * Fig. 30.—Chromatogenous organ torn in two places, b and c, to show the escape of the scales, and the thread-like vessels of which this organ is composed, d, Its small excretory canals, torn in removing the corneous matter, e, Blennogenous or mucous gland, which throws its secretion above the chromatogenous organ. /, Fluid state of the corneous matter, that is to say, pigmentum or scales floating in the midst of mucus, (rete mucosum of Malpighi.) g, Layers of corneous or horny matter stratified to the right and left, more and more condensed, the nearer they approach the surface. Into the mucous gland is seen running a sanguineous vessel, and round it are placed a number of little whitish granules. ACCORDING TO BRESCHET AND ROUSSEL DE VAUZEME. 393 Chromatogenous* Apparatus, (See Fig. 30.) —Which is placed at right angles to the ducts of the mucous glands, at the upper surface of the derm, and at the bottom of the grooves. Its structure is parenchymatous or spongy. On its under surface, it receives a great number of minute capillary vessels, which is the outer limit of the vascular system, with the exception of the vessels which pass up into the villi. On its surface arises many short ducts, and which open in the grooves between the papillae, to convey up the colouring matter in the form of small granules to mix with the mucus. When this tissue is torn, a great many small filaments are seen (a,) from which es- cape small scales or colourless corpuscles in great quantities. (b, c.) This reservoir of scales is found in no other part of the derm. —At /, is seen the fluid state of the corneous matter, that is to say, the pigment of the scales floating in the midst of the mucus. At g, couches of this matter, hardened and stratified, to the right and left, as they approach the surface, and which form the coverings of the villi, and which is thus secreted and mould- ed around them. —The whole of the corneous tissue of the skin, (included usually under the terms of rete mucosum and epidermis,) is formed ac- cording to these anatomists of the mingled products of these mucous and colouring glands.f * From yjutJL-L, colour, and ytvrtui, to create.—p. t In investigating this obscure and difficult part of anatomy, it has been usual with observers to select the skin of the palms of the hands and soles of the feet' as a type of the whole cutaneous system. There is, however, a difference between them. In the palms and soles resides pre-eminently the sense of touch. These parts are likewise destitute of hair, and the papillae which are there very numerous and visible to the naked eye, are very sparsely distributed and appear rudimental in other parts of the body. Much of the discrepancy among anatomists in regard to the structured the skin, appears to be owing to whether they have made their researches mainly upon the palms and soles, or upon the skin of other parts of the body. Chevalier* and Wallace,! have described, especially in the skin of the * Lectures on the general structure of the human body, and on the anatomy and functions of the skin, by J. Chevalier. t Lectures on the structure of the skin, by W. Wallace, London Lancet, 1837. 394 0F THE CUTICLE. The Cuticula or Epidermis, Has been examined with the greatest care by several of the most successful anatomists; but notwithstanding their labours, the structure of this substance is by no means understood. It appears to have some resemblance to the matter of the nails, and of horn; but is rather more flexible, even after allow- ing for the difference in thickness. In those parts where it is thinnest it is semitransparent. It is insensible, and no vessels can be seen in it.* It extends over the whole external surface of the body, except the parts covered by the nails, and is accommodated to the sur- face of the skin, by forming ridges or furrows, corresponding to it. It adheres most closely to the cutis; and when abraded by mechanical violence, the surface of the skin appears moistened by effusion. It is not certain that its mode of union with the skin is per- fectly understood; the adhesion of these membranes to each other is as uniform as that of two smooth surfaces glued together, but it is generally said that the cuticle is attached to the cutis by very numerous and fine filaments. It has often been asserted that these filaments are the exhal- ing and absorbing vessels, which pass through the cuticle, to and face, arms and legs, a system of epidermoid glands, seated in the rete mucosum, and so minute that the latter counted one hundred of them in the 2 4th part of a square inch, and which gives issue to the sweat. These appear to me, to corre- spond with the diapnogenous apparatus of Breschet, as he represents them in the palms and soles. This opinion of Bichat, is therefore erroneous, viz. that the sense of touch is only more perfect in the hands than other parts, in consequence of the shape of the parts, and the facility with which they may be applied round objects, and that the skin of the abdomen substituted for that of the fingers, would have constituted organs of touch.—p. * In the early part of the last century, an anatomist by the name of St. Andre, exhibited a preparation of the cuticle which appeared to be injected with mercury. Ruysh declared the thing impossible, and invited him to an investigation of the subject. This invitation was not accepted, and the affair has been generally con- sidered as a mistake or an imposition.—h, OF THE CUTICLE. 395 from the skin. This sentiment appears very reasonable, but no vessels that pass in this way can be injected. There are innumerable processes which pass from the cuticle to the skin. Many of these are the linings of the cavities which contain the roots of the hairs ; but they are reported by micro- scopical observers to be like the fingers of a glove, closed at their extremities. There are also many processes which contain a sebaceous substance that may be pressed out of them in the form of worms: these are the ducts of sebaceous glands. Besides these, there is an immense number of whitish filaments, which are as fine as the most delicate thread of a spider's web. These filaments can be best seen while the cuticle is separating from the skin of the sole of the foot, as suggested by Dr. Wil- liam Hunter.* They are supposed, to be vascular, but they have never been injected. When the cuticle is in its naturul situation, in union with the skin, there appears to be three species of foramina or pores, on its external surface: viz. 1. Those formed by the passage of the hairs; and 2. Those which are the orifices of the ducts of the sebaceous glands; each of which has been already mentioned. And 3. Such pores as exist on the ends of the fingers and the inside of the hands. It is said that these last are very visible, when magnified to twice or thrice their original bulk, and drawings of them have accordingly been made by Dr. Grewf and by Mr. Cruikshank.J Small specks of fluid can be seen with the naked eye, in the same situations, in warm weather, or when the ends of the fingers are made turgid by a ligature. It is probable that they are formed by the accumulation of fluid at these orifices. The above described pores are situated on the ridges at the ends of the fingers and not in the furrows; and it is probable that similar pores are distributed over the surface of the body. Notwithstanding the appearance of these foramina, when the » Sec the London Medical Observations and Inquiries, vol. ii.—h. t In the Philosophical Transactions, vol. iii. Lowthrop's Abridgement. t Sec his Experiments on Insensible Perspiration. 396 OF THE CUTICLE. cuticle is in its natural situation, several of the most successful investigators of the subject have declared that they could not discover any pores or foramina in the cuticle, when it was sepa- rated from the cutis. The late Professor Meckel of Berlin, who was one of this number, was induced to believe that the matter of exhalation, and, of absorption, soaked through the cuticle, as the vapour of warm water passes through leather.* In support of this doctrine he states that perspiration goes on through the cuticle on the palms of the hands and soles of the feet when it is very thick ; and observes, that if it were transmitted by delicate vessels, the vessels in the feet must be torn by the weight of the body, in persons who walk; and those in the hands would experience the same fate, in labourers, who work with heavy harnmers, &c. On the other hand, Mr. Cruikshank, who could likewise find no pores in the separated cuticle, contends strenuously for their existence notwithstanding; and explains their non-appearance by the following facts, among others, viz. that no foramen will ap- pear in the separated cuticle, although it has been punctured by a needle; and that when the cuticle has been peeled off, from portions of the cutis on which were hairs which must necessa- rily have perforated it, no foramina have appeared in it. M. Bichat took very different ground: he asserted that the pores of the separated cuticle were to be seen distinctly, in large numbers, by looking through it towards the light; he also be- lieved that the course of the exhalent vessels, through the cuticle, might be seen in the same manner; and that they passed ob- liquely. That the cuticle is pervious, is proved incontestably by the functions of perspiration and sweating, as well as of absorption; but there are good reasons for believing that the perforations of the cuticle have a peculiar structure; and are not simple fora- mina. Thus, when a vesicle is formed by the operation of can- tharides or any other process, if the cuticle is not lacerated, it * See Memoirs of the Royal Academy of Sciences of Berlin, vol. xiii. for 1757. CAUSES WHICH PRODUCE VESICATION. 397 will confine the effused fluid for a considerable time, without any appearance of its escape through these pores. This fact, which is strongly opposed to the hypothesis of Meckel, is explained by Cruikshank upon the supposition that the pores of the skin are lined by processes of the cuticle, and that when the cuticle is separated from the cutis, these processes go with it, and act like valves in confining the fluid. Bichat supposes the oblique vessels to produce the same effect upon analogous principles; and compares their situation to that of the ureters, which pass obliquely between the coats of the bladder. This peculiar quality of the cuticle, in admitting of perspira- tion and sweat, and also absorption, while it prevents evapora- tion from the parts which it encloses, is of immense importance. If a portion of skin be deprived of cuticle a short time before death, by a blister for example, this portion will, in a few days, become perfectly dry and hard, like horn ; while the other parts of the skin of the subject, covered by the cuticle, retain their moisture and flexibility. It may, therefore, be admitted, that the use of the cuticle is to keep the skin soft and flexible, by confining its moisture, as well as to defend it.* And it is probable that the sebaceous matter is secreted for the purpose of preserving the cuticle in a state of flexibility. As the cuticle is capable of confining fluid, and resisting the action of chemical agents, it is surprising that epispastics and rubefacients should act through it, upon the skin, with so much certainty as we find they do ; and that cantharides should pro- duce vesications, when applied dry. The thickness of the cuticle on every part of the body is much increased by long continued pressure, forming corns and excres- cences of its own nature. By this cause also it is rendered very thick on the palms of the hands and soles of the feet; although it is originally thicker there than in other parts. * This property of the cuticle is rendered very apparent in attempting to dry anatomical preparations with the skin on, in which the student will fail, unless the cuticle is previously removed by maceration.—p. VOL. I. 34 398 SEPARATION OF THE CUTICLE. It is said that, after long boiling, these thick portions of cuticle may be separated into distinct lamina. In the living subject, the cuticle, when immersed in warm water, seems to absorb some of that fluid; as is evinced by the hands when they have been long in that situation; and also by those parts of the skin to which poultices have been applied. Notwithstanding the uniform adhesion of the cuticle to the cutis, it is observed, in the living subject, to be separated, and formed into vesicles, by a variety of causes, viz. 1. Pinching of the skin, or violent mechanical irritation; such as labouring with hard instruments. 2. By the application of cantharides, and certain other sub- stances which produce vesications. Sometimes these substances appear to inflame the skin; but on other occasions the vesica- tion is produced while the skin appears unchanged in colour, and free from inflammation. The process appears different from that of simple inflammation; for certain rubefacients often in- flame the skin considerably without vesicating or blistering it. 3. The boiling heat will, very generally, produce vesication. 4. Certain diseased processes seem to occasion vesication in a manner which is not well understood, viz. erysipelas, zona, or shingles, pemphigus, and some other eruptions which have no name. In erysipelas there is an obvious inflammation of the skin ; but in some of the other diseases the vesication takes place without the appearance of inflammation. 5. Vesications often appear when there is a tendency to gan- grene. 6. They also occur in some cases of simple fracture, where there is considerable injury. In these cases the fluid effused is often tinged with blood. After death the cuticle is separated from the cutis: 1. By putrefaction; in which case large vesicles are some- times formed. 2. By long continued maceration. 3. By boiling, and 4. By violent dry heat. The cuticle appears to be least deranged when it is separated CHEMICAL QUALITIES' OF THE CUTICLE. 399 by putrefaction and maceration: in these cases the internal sur- face corresponds to the surface of the skin; and the processes which contain the hairs, as well as those which are the ducts of the sebaceous glands, are particularly obvious. The external surface of the cuticle varies in different places, according to the surface of the skin. In some places it appears scaly at times, and has therefore been supposed to consist entirely of scales; but in other parts, when examined attentively, it ap- pears like a half transparent concreted substance, with a rough surface. When the skin has continued dry for a long time, bran-like scales can be rubbed off from it. These are probably composed of the residuum of the secretion deposited on the skin, and of a portion of the external surface of the cuticle. The same sub- stance appears upon the first washing of the skin, after that pro- cess has been discontinued for any length of time. Many speculations have arisen respecting the manner in which the cuticle is originally formed, and reproduced; but none of these are perfectly satisfactory. It is also a question whether the cuticle is endued with vitality, or is merely an inanimate unorganised concrete. No decisive argument have been adduced in favour of its vitality; and it has already been stated, that neither nerves nor vessels can be demonstrated in it. It appears particularly calculated for protecting the skin which it covers; for it is insoluble in water, and resists the action of several powerful chemical agents. Thus, it is not affected by immersion for a considerable time in the sulphuric and muriatic acids; although the nitric acid acts upon it. It resists for a short time, but is at length dissolved, by the pure fixed alkalies, and by lime. It is supposed by the chemists to consist of albumen, in a pecu- liar state of modification. —Malpighi, was the first to discover, by the use of the mi- croscope, an intervening substance between the cuticular cover- ing, and the cutis vera, which he called the rete mucosum or corpus reticulare. This he considered the seat of coloration in 400 CHEMICAL QUALITIES OF THE CUTICLE. the negro, and asserted the cuticle to be alike in all varieties of the human race, that is, colourless. For a long period his re- searches formed the basis of all the systematic treatises upon the skin, and it is only within a recent period, as has before been ob- served, that the study of the subject has been resumed. —The cuticle of the black is now, generally admitted to be of an ashy colour.* And Flourensf has shown, that the reticular appearance of the rete mucosum is entirely an adventitious cir- cumstance. Malpighi first discovered his rete mucosum on the tongue of the ox, and subsequently under the epidermis of the human hand, and from which he drew his description. By ebul- lition he softened the outer covering of the cutis vera, and then tearing off the epidermis, he saw a layer of soft substance with holes in it like the meshes of a net. This was owing to a lacera- tion of the mucous layer: the part covering the apices of the villi going off with the cuticle, while that between the villi and the bases of the papillae adhered to the cutis vera. By maceration in water, which is the surest and most successful method of ef- fecting a dissection in delicate parts, Flourens, found in the same organs, the cuticle to come off, leaving the whole of the mucous body attached, which then presented none of the reticular appear- ance. The cuticle and mucous body were both continuous lay- ers, covering the papillae and forming their sheaths. The sheaths formed by the latter body were broken in Malpighi's preparation- —The cuticular sheaths in the ox, were thin and delicate over * Breschet has asserted that the colour of the skin in different animals is depen- dent upon the form of the scales of the epidermis, by which the light is reflected. The larger cut represents, after this observer, the scales of the epidermic or corneous matter of a white man, diluted with water, and highly magnified, in which are seen fragments of the sudoriferous canals and inhalent vessels. The scales all have a trape- zoidal or lozenge shape. The smaller cut, represents a single scale from the skin of a whale, highly mag- nified. It is black at its .summit, and whitish at its pedicle of insertion. The skin of the whale is black, and these writers assert, that in all animals with black skins, including negroes, the scales of the epidermis, appear under the microscope of this shape or spatulatc.—p. \ Annales des sciences naturelles, 1837.—p. THE NAILS. 401 the fungiform or smaller papillae, but formed thick horny layers over the larger which assist in the action of mastication. —Albinus, repeating the experiments of Malpighi, corrected his error, and in the beautiful designs of Ladmiral, has represented the mucous body as a continuous layer. Since then by Bichat and others, the use of the term rete mucosum, has been con- tinued, not exactly in the original signification of Malpighi, but under the belief that it contained a net-work of vessels. Its foliated structure has been well established by Cruikshank, Gaul- tier, and Flourens. It thus appears that the whole of the anato- my of the skin, requires to be constructed anew. Several of the German and French anatomists have applied themselves to the task, among whom may especially be mentioned, Weber* of Leipzig, and Breschet of Paris.f The views of the latter, on account of his having treated the subject more extensively than the rest, as well as from his high situation in the school of Paris, have already been given.— The Nails. The roots of the nails appear to originate in a fold of the cutis vera, from the epidermis which lines the fold; but the bo- dies of the nails adhere firmly to the cutis on which they lie, and appear to cover it, in the place of the cuticle. The papillae of those parts of the cutis which are covered by the nails are very conspicuous when the nails are removed. It has been sup- posed that there was no rete mucosum between the nails and cutis; but this opinion is probably erroneous, as the black pig- ment is perceptible under the nails of some negroes. The nails can be separated from the cutis by all those pro- cesses which separate the cuticle from it. When this is effected, they remain connected with the cuticle, which appears to be continued into them ; and on this account, as well as their insen- sibility, and their resemblance to the horny excrescences of the cuticle, they are considered as appendages of it. * Arch, fur die Physiologie.—p. t Nouvelles Recherches sur la Structure de la Peau, par G. W. Breschet et Roussel de Vauzeme. Paris, 1835.—p. 44* 402 GROWTH OF THE NAILS. The root is opaque, and appears white. The body is trans- parent, and in health shows the florid colour of the cutis which it covers; but the colour of this portion of the cutis depends upon the state of the circulation; and becomes livid when the blood is disoxygenated, or when the circulation^ ceases there: and this colour also appears through the nails. The nails are unquestionably organised, although their ulti- mate structure is not known. They appear to be composed of lamellae, and these lamellae of fibres. They grow rapidly, and when they are not pared or worn away, they sometimes acquire an immense size. As' a remarkable instance of this, it is related, that a nail of the great toe was sent from Turin to the Academy of Sciences at Paris, which measured four inches and a half in length. The growth seems to take place altogether at the roots. The nails, when chemically examined, appear to consist of a modification of albumen; and thus resemble cuticle and horn in their composition. —The growth of the nails, forwards, is entirely from a fold of the cutis vera, at its root, called, though not with exact pro- p- gg priety, the matrix of the nail, as seen in Fig. 32. It grows also in thickness from the upper surface of the skin, upon which the nail rests. In the formation of a new nail the lamen which starts from the matrix, receives successive layers, as it approaches the extremity, the deepest seated of which is the shortest. In this way the nail gets its thickness and strength, and occasionally, where the deposition of new matter, goes on more rapidly under the body of the nail than at the matrix, the body is thrown up into unsightly rugosities. Its developement is exactly similar to that of the horns and hoofs of animals. The striated appearances of the nail, is said to be owing to the papillary prominences below. The white semicircular line at the root, is called the lunula. —The nails are not exactly analogous in structure to the cuticle, in the ordinary acceptation of the term, to that part which is raised up under a blister. The proper cuticle is that thin coatin EPIGLOTTIS. 441 and muscle. At a small distance above these ligaments are two others, which also pass from the arytenoid to the thyroid carti- lages. They are not so tendinous and distinct as the first men- tioned, and cannot be drawn so tense by the muscles of the ary- tenoid cartilages. They are also situated at a greater distance from each other, and thus form a large aperture. On the external side of the upper extremity of each of the arytenoid cartilages, and nearly in contact with it, is a small cartilaginous body, not so large as a grain of wheat, and nearly oval in form. These are connected firmly to the arytenoid car- tilages, and are called their appendices.* Being in the margin of the aperture of the larynx, they have an effect upon its form. The arytenoid cartilages are the posterior parts of the larynx: the Epiglottis, which has already been mentioned is the anterior. When this cartilage is divested of its membrane, it is oval in its upper extremity, and rather angular below, terminating in a long narrow process, which is like the stalk of a leaf. It is firmly attached to the internal surface of the angular part of the thyroid by this lower process; and, being placed in a perpendicular position, one of its broad surfaces is anterior to- wards the tongue, and the other posterior, towards the opening of the windpipe. It is attached to the os hyoides by dense cellular texture or ligament, and to the tongue by those plaits of the membrane of the mouth which have been already described. It is elastic, but more flexible than the other cartilages; being somewhat different in its structure. Its surface is perforated by the orifices of many mucous ducts. There is a small space between the lower part of this carti- lage, and the upper part of the thyroid and the ligamentous membrane passing from it to the os hyoides. In this is a sub- stance, which appears to consist of glandular and of adipose mat- ter, (see Fig. 36.) It is supposed that some of the orifices on the lower part of the epiglottis communicate with this substance. —This substance is a collection of mucous glands, called glandula epiglottida; the ducts which arise from them are • They are also called Cornicula Laryngis, Tubercles of Santorini.—p. 442 VENTRICLE OF GALEN OR MORGAGNI.-RIMA GLOTTIDIS. twenty or thirty in number, and perforate the epiglottis to throw their mucus on the side of the larynx.— In the erect position of the body, the epiglottis is situated rather higher up than the arytenoid cartilages, and at the dis- tance of ten or twelve lines from them. The mucous membrane which covers the epiglottis, is reflected backwards from the base of the tongue, and is extended from each side of it to the arytenoid cartilages, and being continued into the cavity of the larynx, as well as upon the general surface of the throat, it is necessarily doubled: this doubling forms the lateral margins of the orifice of the cavity of the larynx. In these folds of the membrane are seen some very delicate mus- cular fibres, forming the Aryteno-epiglottideus muscle. —The epiglottis maintains its vertical position, partly from its own elasticity of structure, and partly from the folds of mucous membrane, reflected to it from the tongue, which contain some yellow elastic ligamentous fibres.— The membrane continues down the cavity of the larynx, and, covering the upper ligaments, penetrates into the vacuity between them and the lower ligaments, so as to form a cavity on each side of the larynx, opening between the two ligaments, which is called the Ventricle of Morgagni. The shape of these cavities is oblong. Its greatest length extends from behind forward, on each side of the opening into the windpipe formed by the two lower or principal ligaments; so that when the larynx is re- moved from the subject, upon looking into it from above, you per- ceive three apertures: one in the middle, formed r.- S7 * by the two lower ligaments; and one on each side of it, between the lower and upper liga- Vw—JJ •/„ ment, which is the orifice of the ventricle of fr\/^4 Morgagni. ,it'-VT.p; |^,/ l The aperture between the two lower liga- ti""'\^~^j ments is called the Rima Glottidis, or Chink \jr^----~l>- of the Glottis; the upper aperture, formed by the fold of the membrane extending ~& 7' * Fig. 37. Front view of the larynx; plan of its interior cavity, represented by the lines a a, b b. Is, Superior ligaments of the glottis, li, Inferior ligaments. GLOTTIS. 443 from the epiglottis to the arytenoid cartilages, may be termed Glottis. —The folds of the membrane forming the upper margin of the glottis is loose and distensible, and is liable in laryngeal inflam- mation to become cedematous and bag out so as to impede re- spiration to a great extent, and even produce suffocation.— If the windpipe is divided near the larynx, and the larynx in- verted, so that the rima glottidis may be examined from below, the structure appears still more simple: it resembles a septum fixed abruptly in the windpipe, with an aperture in it of the figure of the rima glottidis. The anterior surface of the two arytenoid cartilages is con- cave. This concavity is occupied in each by a glandular substance, which lies between the cartilage and the lining mem- brane ; and extends itself horizontally, covered by the upper ligament of the glottis. The nature of these bodies is not per- fectly understood ; but they are supposed to secrete mucus.* The membrane which lines the cavity of the glottis being continued from the mouth and throat, resembles the membranes which invest those parts. In some places, where it is in close contact with the cartilages, it appears united with the perichon- drium, and acquires more firmness and density. The general motions of the larynx are very intelligible to those who are acquainted with the muscles which are connected with the thyroid cartilage, and which move the os hyoides. They take place particularly in deglutition, and in some modifications of the voice; and also in vomiting.f The motions of the particular cartilages on each other can also be well understood, by attending to the origin and insertion of the various small muscles connected with them. The most important of these muscles are the crico-arvtenoidei postici and or ligarncnta vocales; the space between the two vocal ligaments forms the chink of the glottis. All the space above them bounded by the epiglottis cartilage, forms the glottis. A, Os hyoides. t, Thyroid, c, Cricoid cartilage. * They constitute the glandula arytenoidea.—p. t For an excellent exposition of the uses of the larynx, see Dunglison's Physi- ology, 4th edition.—p. 444 VESSELS AND NERVES OF THE LARYNX. laterales, the thyreo-arytenoidei, the arytenoidei obliqui, and the arytenoideus transversus. The effects of their actions appear to be the dilating or contracting the rima glottidis, and relaxing or extending the ligaments which form it. The arteries of the larynx are derived from two sources, namely, the superior thyroid, or laryngeal branch of the ex- ternal carotid, and the thyroid branch of the subclavian. The nerves of the larynx also come to it in two very different directions on each side. It receives two branches from the par vagum ; one which leaves that nerve high up in the neck, and is called the Superior Laryngeal branch; and another which pro- ceeds from it after it has passed into the cavity of the thorax, and is called from its direction the Recurrent. —According to M. Blandin, who has rather recently made some research upon this subject, the superior laryngeal nerve, is distributed chiefly to the mucous membrane and cryptae of the larynx, but likewise sends some filaments to the arytenoid and crico-thyroid muscles, and others which anastomose with the branches of the recurrent. The recurrent supplies all the mus- cles of the larynx, with the exception of the crico-thyroid. There is still among anatomists some difference of opinion in regard to the distribution of these nerves.— The extreme irritability of the glottis is unequivocally demonstrated by the cough which is excited when a drop of water, or any other mild liquid, or a crumb of bread enters it. Notwithstanding this, a flexible tube, or catheter, has several times been passed into the windpipe through the rima glottidis, and been endured by the patient a considerable time. The cough, which occurs when these parts are irritated, does not appear to arise exclusively from the irritation of the membrane within the glottis; for, if it were so, mucilaginous substances, when swallowed slowly, could not suspend it. Their effect in relieving cough is universally known; and as they are only applied to the surface exterior to the glottis, it is evi- dent that the irritation of this surface must also produce coughing. Several curious experiments have been made to determine the effect of divi- ding the different nerves which go to the larynx; by which it appears that the recurrent branches supply parts which are essentially necessary to the formation of the voice, whilst the laryngeal branches supply parts which merely influence its modulation, or tone. See Mr. Haighton's Essay on this subject: Memoirs of the Medical Society of London, vol. iii. THE THYROID GLAND. 445 The Thyroid Gland, (see Fig. 34, p. 417,) May be described here, although a part of it is situated below the larynx. This body consists of two lobes, which are united at their lower extremities by a portion which extends across the anterior part of the windpipe. Each lobe generally rises upwards and backwards from the second cartilaginous ring of the windpipe over the cricoid cartilage and a portion of the thyroid. It lies behind the sterno-hyoidei, and sterno-thyroidei muscles. It is of a reddish-brown colour, and appears to consist of a granulous substance; but its ultimate structure is not understood. It is plentifully supplied with blood, and receives two arteries on e~ach side: one from the laryngeal branch* of the external carotid: and the other from the thyroid branch of the subclavian. Notwithstanding this large supply of blood, there is no proof that it performs any secretion: for although several respectable anatomists have supposed that they discovered excretory ducts passing to the windpipe, larynx, or tongue, it is now generally agreed that such excretory ducts are not to be found. Several instances have, however, occurred, in which air has been forced, by violent straining, from the windpipe into the substance of this gland.f —The two lobes of the thyroid gland, when extended and mea- sured from side to side are together about three inches in diameter. The lobes extend upwards on the sides of the larynx and down- wards on the oesophagus, and He upon the inner face of, and partly covering the primitive carotid artery and internal jugular vein. That part of the gland which unites the lobes together, and is * The main branch from the external carotid, is now more commonly called su- perior thyroid.—r. t There are two membranous expansions in the neck which should be noticed in its dissection. The first, called Fascia Superficialis, lies immediately beneath the skin, may be considered as a continuation of the fascia superficialis abdominis, and is strongly connected to the base of the lower jaw, being also spread over the parotid gland. It is not very distinct in all subjects. The second is called the Fascia Profunda Cervicis; it extends from the larynx and thyroid gland to the upper part of the sternnm and first ribs; the great vessels, &c. of the superior me- diastinum are placed immediately below it.—h. VOL. I. 38 446 STRUCTURE OF THE PHARVNX. stretched across the trachea, covering the two or three usually and sometimes the seven upper rings of the trachea, is called the isthmus of the gland. From the upper surface of the isthmus a process of the gland is usually seen extending upwards, on the left side over the front surface of the larynx, to be attached by ligamentous fibres to the os hyoides. A small muscle called the levator glandulae thyroideas, has been described by Duverney, Soemmering and others, running down from the os hyoides in front of the larynx to the upper part of the isthmus of the gland. According to Professor Horner, its existence is very rare, with which opinion my own more limited observation coincides. —The lobes of the gland are composed of smaller lobules, and the spongy structure of the latter, is filled with a yellowish and somewhat oily fluid. Of the uses of this gland nothing positively is known. Its importance in the system of the adult cannot be great, as its removal by extirpation, which has been many times practised, has not appeared to leave any functional lesion in the economy.— Of the Pharynx. The pharynx is a large muscular bag, which forms the great cavity behind the nose and mouth that terminates in the oeso- phagus. It has been compared to a funnel, of which the oesophagus is the pipe; but it differs from a funnel in this respect, that it is in- complete in front, at the part occupied by the nose and mouth and larynx. It is connected a'bove, to the cuneiform process of the occi- pital bone, to the pterygoid processes of the sphenoidal, and to both the upper and lower maxillary bones. It is in contact with the cervical vertebrae behind; and, opposite to the cricoid carti- lage, it terminates in the oesophagus. If the pharynx and oesophagus be carefully dissected and de- tached from the vertebrae, preserving the connexion of the pharynx with the head, and the head then be separated from the body, by dividing the articulation of the atlas and the os occipitis, and cutting through the soft parts below the larynx, the resem- blance to a funnel will be ve ' STRUCTURE OF THE PHARYNX. 447 In this situation, if an incision be made from above down- wards through the whole extent of the posterior part of the pharynx, the communication of the nose, mouth, and windpipe, with this cavity, will be seen from behind at one view. The openings into the nose, or the posterior nares, appear up- permost. Their figure is irregularly oval, or oblong; they are separated from each other by a thin partition, the vomer. Im- mediately behind, on the external side of each of these orifices, is the Eustachian tube. (See Fig. 34, p. 417.) The soft palate will appear extending from the lower boun- dary of the posterior nares, obliquely backwards and downwards, so as nearly to close the passage into the mouth. The uvula hangs from it: and, on each side of the uvula, the edge of the palate is regularly concave. Below the palate, in the isthmus of the fauces, are the ridges or half arches, and the tonsils between them. The half arch which presents first, in this view, runs obliquely downward and backward, and not parallel to the other. Close to the root of the tongue is the epiglottis erect; and, immediately adjoining it, is an aperture large enough to admit the end of a middle-sized finger. This aperture is widest at the extremity next to the epiglottis, and rather narrower at the other extremity: it is the glottis or opening of the windpipe. When the larynx is elevated, the epiglottis can be readily depressed so as to cover it completely. The extremities of the arytenoid cartilages, and their appen- dices, may be recognised at the posterior edge of the glottis. At a short distance below this edge, the oesophagus begins. The Pharynx is composed of the membrane continued from the nose and mouth internally, and of a stratum of muscular fibres externally. The internal membrane is very soft and flexible and perforated by many muciferous ducts. The surface which it forms is rather rough, owing to the mucous glands which it covers. It has a red colour, but not so deep as that of some other parts. It is connected to the muscular stratum by a loose cellular membrane. The muscular coat consists of three different portions, which 448 CONSTRICTOR MUSCLES OF THE PHARYNX. • are considered as so many distinct muscles. They are called the superior, middle, and inferior constrictor muscles of the pharynx. The fibres of each of these muscles originate on each side, and run in an oblique direction to meet in the middle, thus forming the posterior external surface of the dissected pharynx. The fibres of the upper muscles originate from the cuneiform process of the occipital bone, from the pterygoid processes of the os sphenoides, and from the upper and lower jaws, near the last dentes molares, on each side. They unite in a middle line in the back of the pharynx. The fibres of the middle muscles originate principally from the lateral parts of the os hyoides, and from the ligaments which connect that bone to the thyroid cartilage. The superior fibres run obliquely upwards, so as to cover a part of the first men- tioned muscle, and terminate in the cuneiform process of the occipital bone; while the other fibres unite with those of the opposite side in the middle line. The fibres of the lower muscles arise from the thyroid and the cricoid cartilages, and terminate also in the middle line: those which are superior, running obliquely upwards; the inferior, nearly in a transverse direction. It is obvious, from the origin and insertion of these fibres, that the pharynx must have the power of contracting its dimensions in every respect; and, particularly, that its diameter may be lessened at any place, and that the whole may be drawn upwards. PART VI. OF THE THORAX. Before the thorax is described, it will be in order to consider the Mamma; Or those glandular bodies situated on the anterior part of it> which, in females, are destined to the secretion of milk. These glands lie between the skin and the pectoral muscles, and are attached to the surfaces of those muscles by cellular membrane. They are of a circular form; and consist of a whitish firm substance, divisible into small masses or lobes, which are com- posed of smaller portions or lobuli. Between these glandular portions, a great deal of adipose matter is so diffused, that it constitutes a considerable part of the bulk of the mammae. The gland, however, varies greatly in thickness in the same person at different periods of life. The mammae become much enlarged about the age of pu- berty. They are also very large during pregnancy and lacta- tion ; but after the period of child-bearing they diminish consider- ably. They are supplied with blood by the external and inter- nal mammary arteries, the branches of which enter them irre- gularly in several different places. The veins correspond with the arteries. From the small glandular portions that compose the mamma, fine excretory tubes arise, which unite together and form the great lactiferous ducts of the gland. These ducts proceed in a radiated manner from the circumference to the centre, and ter- minate on the surface of the nipple.* * Described in the 10th century, by Charles Etienne, Vesalius and Posthius, but their uses were unknown.—h. 38* 450 MAMMAE. They are commonly about fifteen in number, and vary con- siderably in size: the largest of them being more than one-sixth of an inch in diameter.* They can be very readily injected by the orifices of the nip- ple, from a pipe filled with mercury, in subjects who have died during lactation or pregnancy; but they are very small in sub- jects of a different description. It has been asserted by respectable anatomists, that these ducts communicate freely with each other; but they do not appear to do so ; each duct seems to be connect- Fig. 38.f ed with its proper 3 branches only.J Haller appears to have entertained the remarkable sentiment, that some of the ducts originate in the adi- pose matter about the gland, as well as in the glandular sub- stance.§ The papilla, or nip- ple, in which these ducts terminate, is in the centre of the mam- ma: it consists of a firm elastic substance, and is nearly cylin- * These ducts vary in number in different individuals, from fifteen to twenty.—p. t Fig. 38, is a vertical section of the mammary gland of a young female who died during lactation. The ducts were injected with wax, and two dissected oul their full length to their origin in the lobules of the gland. 2, 2, Base of the nip- ple. 3,3,3, Lactiferous ducts cut off at the base of the nipple. 4,4, The top of the ducts which exhibited their whole length. 5, 5, Sinuses formed by these ducts at the base of the nipple. 6,6,6,6, Branches of these ducts running to the lo- bules. 7, 7, 7,7,7, The lobules separated from each other. 8,8, The orifices of these ducts on the top of the nipple. t See Edinburgh Medical Commentaries, vol. i. p. 31.—A paper by Meckel.—h. § Elementa Physiologic, Tom. 7, Pars II. page 7. —In the adipose matter about the gland, the lactiferous tubes (ducti galactophori) appear to communicate with the absorbent vessels. In injecting the gland with mercury, I have frequently found the metal to pass off from the ducts along the absorbent vessels,—p. LACTIFEROUS DUCTS. 451 drical in form. It is rendered tumid by irritation, and by cer- tain emotions. The lactiferous ducts terminate upon its extremity. When it is elongated they can freely discharge their contents; but when it contracts, this discharge is impeded. The skin immediately around the nipple is of a bright red colour in virgins of mature age. In pregnant women it is sometimes almost black; and in women who have borne children it is often brownish. It abounds with sebaceous glands, which form small eminences on its sur- face. This gland exists in males, although it is very small. In boys, soon after birth, it has often been known to tumefy, and become very painful, in consequence of the secretion and accumulation of a whitish fluid, which can be discharged by pressure. It also sometimes swells and is painful, in males at the age of puberty. There have been some instances in which it has secreted milk in adult males; and a few instances also in which it has been af- fected with cancer, in the same sex. The mamma is plentifully supplied with absorbent vessels, which pass from it to the lymphatic glands in the axilla. Its nerves are principally derived from the great plexus formed by the nerves of the arm. —The skin covering the mammary gland, is exceedingly thin, delicate and vascular, and that of the nipple and areola, more delicate and sensitive than any other portion.^ —Each lactiferous duct by its branching and convolutions, forms a distinct lobule of the gland, and terminates in a series of vas- cular granules* about the size of millet seed, which are readily distinguished from each other in individuals who have died dur- ing lactation. The lobules of the gland vary in size, which, in subjects where the subcutaneous matter is not abundant, gives a feeling of unevenness or roughness to the gland. —There are no valves in the lactiferous tubes.— * Histoire de la Generation, par Grimaud de Caux et Martin Saint-Anee 4to Paris, 1H.I7.—p. s ' 452 CAVITY OF THE THORAX. CHAPTER XV. OF THE GENERAL CAVITY OF THE THORAX. Of the Form of the Cavity of the Thorax. The osseous structure of the thorax is described in page 136. The cavity is completed by the intercostal muscles, which close the vacuities between the ribs; and by the diaphragm, which fill up the whole space included within its lower margin. If we except the apertures of the diaphragm, which are com- pletely occupied by the aorta, the vena cava, and the oesopha- gus, &c, the only outlet of this cavity is above: it is formed by the upper ribs, the first dorsal vertebra, and the sternum. The figure of this aperture is between that of the circle and the oval; but it is made irregular by the vertebrae, and by the upper edge of the sternum. When the superior extremities and the muscles appropriated to them are removed, the external figure of the thorax is coni- cal ; but the cavity formed by it is considerably influenced by the spine, which protrudes into it; while the ribs, as they pro- ceed from the spine, curve backwards, and thus increase its pro- minency of the cavity. The diaphragm has a great effect upon the figure of the cavity of the thorax. It protrudes into it from below, with a convexity of such form that it has been compared to an inverted bowl; so that although it arises from the lower margin of the thorax, the central parts of it are nearly as high as the fourth rib. The position of the diaphragm is also oblique. The anterior portion of its margin, being connected to the seventh and eighth ribs, is much higher than the posterior portion, which is attached to the eleventh and twelfth. In consequence of the figure and position of the diaphragm, PLEURAE. 453 the form of the cavity of the thorax resembles that of the hoof of the ox when its posterior part is presented forwards. Of the Arrangement of the Pleura. The thorax contains the two lungs and heart, as well as se- veral very important parts of smaller size. The lungs occupy the greatest part of the cavity; and to each of them is appointed a complete sac, called Pleura, which is so arranged that it covers the surface of the lungs, and is con- tinued from it to the contiguous surface of the thorax, which it lines. After covering the lung, it is extended from it to the spine posteriorly: so that in tracing the pleura in a circular direction, if you begin at the sternum, it proceeds on the inside of the ribs, to the spine; at the spine it leaves the surface of the thorax, and proceeds directly forwards towards the sternum. In its course from the spine to the sternum, it soon meets with the great branch of the windpipe and blood-vessels, which go to the lung: it continues on these vessels and round the lung until it arrives at the anterior side of the vessels, when it again proceeds forwards until it arrives at the sternum. Each sac being arranged in the same way, there is a part of each extended from the spine to the sternum. These two laminae form the great vertical septum of the thorax, called Mediastinum. They are situated at some dis- tance from each other; and the heart, with its investing mem- brane or pericardium, is placed between them. The pericardium is also a complete sac or bladder, which, after covering perfectly the surface of the heart, is extended from it so as to form a sac, which lies loose about it, and appears to contain it. This loose portion adheres to those parts of the laminae of the mediastinum with which it is contiguous; and thus three chambers are formed within the cavity of the thorax: one for each lung, and one for the heart. The two lamina of the pleura, which constitute the mediasti- num, are at different distances from each other, in different places. At the upper part of the thorax, they approach each other from the internal edges of the first ribs; and as these include a 454 MEDIASTINUM. space which is nearly circular, the vacuity between these lamina is necessarily of that form, at its commencement above. Here, therefore, is a space between them above, which is oc- cupied by the transverse vein that carries the blood of the left subclavian and the left internal jugular to the superior cava; by the trachea; by the oesophagus; and by the subclavian and carotid arteries, as they rise from the curve of the aorta. This space is bounded below by the above mentioned curve of the aorta. The heart and pericardium are so placed that there is a small distance between them and the sternum : in this space the two lamina of the mediastinum are very near to each other; and cellular substance intervenes between them. This portion of the mediastinum is called the Anterior Mediastinum.* Posteriorly, the heart and pericardium are also at a small dis- tance from the spine; and here the lamina of the mediastinum are at a greater distance from each other, and form a long nar- row cavity which extends down the thorax in front of the ver- tebrae : this is called the Posterior Mediastinum. It contains a considerable portion of the aorta as it descends from its curve, the oesophagus, the thoracic duct, and the vena azygos. The aorta is in contact with the left lamen, and can often be seen through it when the left lung is lifted up. The oesophagus is in contact with the right lamen; in its pro- gress downwards, it inclines to the left side and is advanced be- fore the aorta. The vena azygos appears posterior to the oesophagus; it pro- ceeds upwards until it is as high as the right branch of the wind- pipe : here it bends forward, round that branch, and opens into the superior cava, before that vein opens into the right auricle. The thoracic duct proceeds upwards from below, lying in * This mediastinum, being placed in front of the longitudinal diameter of the pericardium is found at its lower part inclined to the left of the middle line. The cellular tissue between its layers, communicates indirectly with the cellular tissue on the outer side of the peritoneum, in the notch formed by the origin of the greater muscle of the diaphragm, under the xiphoid appendix of the sternum. By this channel, abscesses of the anterior mediastinum, may make their way ex- ternally upon the abdomen.—p. PREPARATION OF THE THORAX. 455 the space between the aorta and the vena azygos, until the be- ginning of the curve of the aorta, when it inclines to the left, proceeding towards the place of its termination. —The anterior and posterior mediastinal are formed as is shown above, by the layers of the pleura, between the sternum and pericardium, and between the pericardium and spine. But the pericardium does not extend the whole length of the thoracic cavity; it terminates about two inches short of the top of the sternum, and at this part, there being nothing interposed to divide the layers into an anterior and posterior portion, they pass directly from the vertebrae to the sternum, and constitute what is called the Superior Mediastinum. The two layers constituting this, continuous below with the anterior and superior mediastinae, and each lining the upper margin of the first rib, so as to form a conical pouch projecting a slight distance above the middle of the clavicle, constitute a triangular cavity, the base of which is upwards, and corresponds to the root of the neck. This cavity contains the thymus gland, the arteria innominata, the primitive carotid and subclavian of the left side, the superior vena cava, the trachea, oesophagus, and par vagum nerve. —The sympathetic nerve is not contained in this mediastinum; it passes a little to the outside of the posterior external angle of it.— The formation of the mediastinum, and the arrangement of the pleura, as well as the connexion of these membranes with the parts contained in the thorax, may be studied advantageously, after the subject has been pre- pared in the manner now to be described. Take away, from each side, the five ribs which are situated between the first and last true ribs, by separating their cartilages from the sternum, and their heads from the spine; so that the great cavities of the thorax may be laid open. The precise course of the mediastinum is thus rendered obvious; and the sternum may now be divided with a saw throughout its whole length in the same direction; so that the division of the bone may correspond with the space between the lamina of the mediastinum. Separate the portion of the sternum cautiously, so as to avoid lacerating the lamina of mediastinum; and to keep them separate, while the trachea is dissected from the neck into the cavity of the thorax; the great trans- verse vein and the descending cava are dissected to the pericardium; and 456 PREPARATION OF THE THORAX. the left carotid artery, with the right subclavian and carotid, are dissected to the curve of the aorta, taking care not to destroy the lamina of the mediastinum. After this preparation the upper space between the lamina of the mediasti- num can be examined, and the relative situation of the trachea and the great vessels in it can be understood. The anterior mediastinum can also be studied: the root of each lung, or its connexion with the me- diastinum, may be seen perfectly; and the precise situation of the lung, in its proper cavity, may be well conceived. After this, while the portions of the sternum are separated, the pericardium may be opened, and the heart brought into view: the attachment of the pericardium, and to the mediastinum, and to the diaphragm, may be seen with advantage in this situation. The portions of the sternum may now be detached from the ribs, with which they remain connected; and fur- ther dissection may be performed to examine the posterior mediastinum and its contents, and the parts which constitute the roots of the lungs. OF THE PERICARDIUM. 457 CHAPTER XVI. OF THE HEART AND PERICARDIUM, AND THE GREAT VESSELS CON NECTED WITH THE HEART. Of the Pericardium. The heart is enclosed by a membranous sac, which, upon a superficial view, seems only connected with its great vessels. —The whole of the organ lays unattached in the cavity of the sac, except, by the arteries and veins connected with its base. The sac is in fact composed of two layers, one external and fibrous, and one internal and serous; the latter of these not only lines the inner face of the outer membrane, but is reflected like other serous membranes, over the roots of the vessels placed in the pericardium, and over the whole of the outer surface of the heart itself. This internal serous lining is very thin and delicate, and can only be raised in small shreds, either from the outer layer of the pericardium, or from the heart; except at the base of the latter organ, where, in females, it is usually, and in males, frequently, separated from the muscular tissue, by some sub-serous fatty matter.— If it were dissected from the heart, without laceration or wounding, it would be an entire sac. The pericardium, thus arranged, is placed between the two lamina of the mediastinum, and adheres firmly to them where they are contiguous to it; it also adheres firmly to the diaphragm below, and thus preserves the heart in its proper position. The figure of the pericardium, when it is distended, is some- what conical; the base being on the diaphragm. The cavity formed by it is larger than the heart after death, but it is pro- bable, that the heart nearly fills it during life; for when this organ is distended by injection, it often occupies the whole cavity of the pericardium. —The attachment of the pericardium to the diaphragm, is vol. r. 39 458 PERICARDIUM. exactly over the cordiform tendon of the latter. The French anatomists have erroneously considered the fibrous layer of the pericardium, as a mere reflection of the tendon upwards. By separating them with a knife, we find, they are united by a short cellular tissue, which is densest and strongest at the periphery of their junction. The sides of the pericardium are covered in part by the pleura, which gives the sac the appearance of being formed by three tunics. —Underneath the pleural lining, is found the phrenic nerve, and in fat subjects, a good deal of adipose matter.— The pericardium is composed of two lamina, the internal of which covers the heart, as has been already described; while the external merely extends over the loose portion of the other, and blends itself with the mediastinum, where that membrane invests the great vessels. —Its principal attachment or termination above, is upon the arteries and veins entering the heart, (with the exception of the vena cava inferior,) over which it sends tubular prolongations, which gradually blend with their external coats. Between these prolongations on the inside of the sac, hollow pouches are neces- sarily left, which are called the cornua of the pericardium. —The fibrous layer of the pericardium resembles in structure and appearance, the dura mater of the brain. —The arteries of the pericardium are very small; they are de- rived from the phrenic, bronchial, aesophageal, internal mammary arteries, and from the aorta itself. Its veins terminate in the vena azygos. Its nerves are few and small, and originate from the cardiac plexus.— The internal surface of the pericardium is very smooth and po- lished ; and in the living subject is constantly moistened with a fluid which is probably effused from the exhalent vessels on its surface. The quantity of this fluid does not commonly exceed two drachms; but in cases of disease it sometimes amounts to many ounces.* It is naturally transparent, but slightly tinged with red * The pericardium has been so distended, by effusion in dropsy, that it has formed a tumour, protruding on the neck from snder the sternum. This tumour had a strong pulsating motion. It disappeared completely when the other hydropic symptoms were relieved. OF THE HEART. 459 in children, and yellow in old persons. It is often slightly tinged with red in persons who have died by violence. Of the Heart. The great organ of the circulation consists of muscular fibres. which are so arranged that they give it a conical form, and compose four distinct cavities within it. Two of these cavities, which are called Auricles, receive the contents of the veins; the other two communicate with the ar- teries, and are called Ventricles. The auricles form the basis of the cone; the ventricles the body and apex. The structure of the auricles is much less firm than that of the ventricles, and consists of a smaller proportion of muscular fibres. They appear like appendages of the heart, while the ventricles compose the body of the viscus. The ventricles are very thick, and are composed of muscular fibres closely compacted. The figure of the heart is not regularly conical; for a portion of it, extending from the apex to the base, is flattened; and in its natural position, this flat part of the surface is downwards. It is placed obliquely in the body; so that its base presents backward and to the right, and its apex forward and to the left. Notwithstanding this obliquity, the terms right and left are applied to the different sides of the heart, and to the different auricles and ventricles; although they might, with equal pro- priety, be called anterior and posterior. The two great veins called Vena Cava, which bring the blood from every part of the body, open into the right auricle from above and below; the right auricle opens into the right ventricle; and from this ventricle arises the artery denominated Pulmonary, which passes to the lungs. The Pulmonary veins, which bring back the blood from the lungs, open into the left auricle; this auricle opens into the left ventricle; and from this ventricle proceeds the Aorta, or great artery, which carries blood to every part of the body. The heart is preserved in its position, 1st, by the venae cavas 460 RIGHT AURICLE. which are connected to all the parts to which they are contigu- ous in their course; 2d, by the vessels which pass between it and the lungs, which are retained in a particular position by the mediastinum; 3d, by the aorta, which is attached to the medias- tinum in its course downwards, after making its great curve; and 4th, by the pericardium, which is attached to the great vessels and to the mediastinum. By these different modes the basis of the heart is fixed, while its body and apex are perfectly free from attachment, and only contiguous to the pericardium. The external surface of the heart, being formed by the serous layer of the pericardium, is very smooth: under this surface a large quantity of fat is often found. The two auricles are contiguous to each other at the base, and are separated by a partition which is common to both. The Right Auricle originates from the junction of the two Fig. 39.* It Ti, fc u venae cavae. These veins are united at some distance behind the right ventricle,f and are di- lated anteriorly into a sac or pouch, which is called the Sinus, and extends to the right ventricle, to which it is united.J The upper part of this pouch, or sinus, forms a point with in- dented edges, which is detached from the ventricle, but lies loose on the right side of the aorta. This point has some resem- blance to the ear of a dog, from * Fig. 39.—Loiagitudinal section of the heart, showing its cavities, b, Right ventricle, c, Septum ventriculorum. d, Right auricle, e, left auricle. /, Sec- tion of the mitral valves, g, Section of tricuspid valves. A, Arch of aorta. A, de- scending aorta, i, i, Vena cava superior and inferior, k, k, Right and left branches of the pulmonary artery. I, I, Pulmonary veins. t In this description the heart is supposed to be in its natural position. t At the place of junction of these veins there is a projection, indistinctly seen in man, but very manifest in some of the larger mammalia, called tuberculum Loweri.—p. RIGHT AURICLE. 461 which circumstance the whole cavity has been called auricle; but by many persons the cavity is considered as consisting of two portions: the Auricle, strictly speaking; and the Sinus Ve- nosus, above described: they however form but one cavity. This portion of the heart, or Right Auricle, is of an irregular oblong figure. In its posterior surface, it is indented; for the direction of the two cavae, at their junction, is not precisely the same; but they form an angle, which causes this indentation. The anterior portion of the auricle, or that which appears like a pouch between the ventricle and the veins, is different in its structure from the posterior part, which is strictly a portion of the veins. It consists simply of muscular fibres, which are ar- ranged in fasciculi that cover the whole internal surface: this is also the case with the point, or that part which is strictly called auricle. These fasciculi are denominated Musculi Pectinati, from their resemblance to the teeth of a comb. That part of the internal surface, which is formed by the septum is smooth, and the whole is covered by a delicate mem- brane. On the surface of the septum, below the middle, is an oval de- pression, which has a thick edge or margin: this is called the Fossa Ovalis* In the foetal heart, it was the Foramen Ovale, or aperture which forms the communication between the twro auricles. Near this fossa is a large semilunar plait, or valve, with its points and concave edge uppermost, and convex edge down- wards. It was described by Eustachius, and therefore, is called the Valve of Eustachius. —It commences at the lower surface of the opening of the inferior vena cava, and runs forwards to terminate below the fossa ovalis. It served in the foetus to obstruct the passage of the venous blood from the right auricle into the right ventricle, and to direct it in a great measure through the foramen ovale.— Anterior to this valve, and near the union of the auricle and • The thick edge or margin is spoken of as the annulus ovalis.—p. 39* 462 RIGHT VENTRICLE. ventricle, is the orifice of the proper vein of the heart, or the coronary vein. This orifice is covered by another semilunar valve, which is sometimes reticulated.* The aperture, which forms the communication between the right auricle and right ventricle, is about an inch in diameter, and is called ostium venosum. From its whole margin arises a valvular ring, or duplicature of the membrane lining the surface: this circular valve is divided into three angular portions, which are called Valvula Tricuspides. From their margins proceed a great number of fine tendinous threads, which are connected to a number of distinct portions of muscular substance, which arise from the ventricle. The Right Ventricle, when examined separately from the other parts of the heart, is rather triangular in its figure. It is composed entirely of muscular fibres closely compacted; and is much thicker than the auricle, although not so thick as the other ventricle. Its internal surface is composed of bundles or co- lumns of fleshy fibres, which are of various thickness and length. Some of these columns (columna carnea) arise from the ven- tricle, and are connected with the tendinous threads, (chorda tendinea,) which are attached to the margin of the tricuspid valves: the direction of them is from the apex of the heart towards the base. Others of the columns arise from one part of the surface of the ventricle, and are inserted into another part. A third species are attached to the ventricle throughout their whole length, forming ridges or eminences on it. The columns of the two last described species are very numerous. They pre- sent an elegant reticulated surface when the ventricle is laid open, and appear also to occupy a considerable portion of the cavity of the heart, which some of them run across in every di- rection near the apex. They are all covered by a membrane continued from the auricle and the tricuspid valves; but this membrane appears more delicate and transparent in the ventri- cle than it is in the auricle. * The orifice is called the foramen Thebesii, and the valve, valvula Thebesii, from the anatomist who first described them. There are several other orifices in the neighbourhood of the foramen of Thebe- sius, by which some of (he lesser coronary veins discharge into the right auricle.—p. RIGHT VENTRICLE 463 —This is called the internal serous, or endo-cardial lining membrane of the heart. On the right side it is continuous with that of the veins and pulmonary artery, on the left with the aorta and pulmonary veins. It is extremely thin, smooth, and transpa- rent, covers all the interior surface of the cavities of the heart, and by being thrown into folds with some fibrous matter inter- posed between the layers to increase their strength, constitutes the valves.— A portion of the internal surface of the ventricle, which is to the left, is much smoother and less fasciculated than the rest: it leads to the orifice of the pulmonary artery, which arises from it near the basis of the ventricle. This artery is very conspicu- ous, externally, at the basis of the heart. It is very evident, upon the first inspection of the heart, that the valvulae tricuspides will permit the blood to flow from the auricle to the ventricle; but must rise and close the orifice, and thereby prevent its passage back again, when the ventricle con- tracts. The use of the tendinous threads, which connect the valves to the fleshy columns, is also very evident; the valve is supported by this connexion, and prevented from yielding to the pressure and opening a passage into the auricle. The blood, therefore, upon the contraction of the ventricle, is necessarily forced into the pulmonary artery; the passage to which is now perfectly free. Into this artery the membrane lining the ventricle seems continued; but immediately within the orifice of the artery, it is formed into three semicircular folds, each of which adheres to the surface of the artery by its circumference, while the edge constituting its diameter is loose. In the middle of this loose edge is a small firm tubercle, called Corpusculum Arantii,* which adds to the strength of the valve. Each of these valves, by its connexion with the artery, forms a sack or pocket, the orifice of which opens forward towards the course of the artery, and the bottom of it presents towards the ventricle. Blood will, therefore, pass from the ventricle in the artery, and along it • After Arantius, a professor at Bologna, who first described it. 464 LEFT AURICLE. without filling these sacks; and, on the contrary, in this course, will compress them and keep them empty. If it moves in the artery towards the heart, it will necessarily fill these sacks, and press the semicircular portions, from the sides of the artery, against each other; by this means a partition or septum, con- sisting of three portions, will be formed between the artery and the heart, which will always exist when the artery compresses, (or acts upon,) its contents. It is demonstrable, by injecting wax into the artery, in a retrograde direction, that these valves do not form a flat septum, but one which is convex towards the heart, and concave towards the artery; and that this convexity is composed of three distinct parts, each of which is convex. At the place where these valves are fixed, the artery bulges out when distended by a retrograde injection. The enlargements thus produced are called the Sinuses of Valsalva, after the ana- tomist who first described them. The valves are called Semi- lunar—and, although they are formed by a very thin membrane, they are very strong. The Left Auricle is situated on the left side of the basis of the heart. It originates from the junction of the four pulmonary veins; two of which come from each side of the thorax, and appear to form a large part of it. It is nearly of a cubic form; but has also an angular portion, which constitutes the proper auricle, that proceeds from the upper and left part of the cavity, and is situated on the left side of the pulmonary artery. This auricle is lined by a small membrane, from which the valves between it and the ventricle originate; but it has no fleshy columns or musculi pectinati, except in the angular pro- cess properly called auricle. These valves and the orifice communicating with the ventri- cle, resemble those which have been already described between the right auricle and ventricle; but with this difference, that the valvular ring is divided into two portions only, instead of three, which are called Valvula Mitrales.* The tendinous threads, which are connected to the muscular columns, are also attached to these valves, as in the case of the right auricle. * From a resemblance in shape to the mitre or bishop's cap.—p. LEFT VENTRICLE. 465 These valves admit the passage of blood from the auricle into the ventricle, but completely prevent its return when the ventricle contracts. One of them is so situated that it covers the mouth of the aorta while the blood is flowing into the ventri- cle, and leaves that orifice open when the ventricle contracts, and the passage to the auricle is closed. The Left Ventricle is situated posteriorly, and to the left of the Right Ventricle. Its figure is different, for it is rather conical, and it is also longer. The internal surface of this ventricle resembles that of the right ventricle: but the columnae carneae are stronger and larger. On the right side of this ventricle is the mouth of the aorta. The surface of the ventricle near this opening is smooth and po- lished, to facilitate the passage of the blood. The mouth of the aorta is furnished with three semilunar valves, after the manner of the pulmonary artery, but the former are stronger; the corpuscula Arantii are better developed in them. Indeed, Mr. Hunter does not admit of their existence in the pulmonary artery. The sinuses of Valsalva are about the same size in both arteries. The cavity of this ventricle is supposed to be smaller than that of the right: but the amount of the difference has not been accurately ascertained. This ventricle must have much more force than the right, as its parietes are so much thicker. Their thickness often exceeds half an inch. The difference in the strength of the two ventricles probably corresponds with the difference between the extent of the pul- monary artery and the aorta. The'thickness of the septum between the ventricles is thicker than the sides of the parietes of the right ventricle, and less thick than those of the left. The muscular fibres of the heart are generally less florid than those of the voluntary muscles; they are also more closely compacted together. The direction of many of them is oblique or spiral; but this general arrangement is very intricate: it is 466 FIBRES OF THE HEART. such, however, that the cavities of the heart are lessened, and probably completely obliterated, by the contraction of these fibres.* —The muscular fibres of the heart have been carefully stu- died by Wolf and Malpighi, and more recently still, by Gerdy.f According to this latter anatomist, there is a fibrous zone or gir- dle formed around each auricle and arterial orifice of the heart, which zones are connected with each other and with the valves. From these zones originate all the muscular fibres of the heart. Some which run upwards and turn in every direction round the auricles, and form loops, the extremities of which are in- serted on the opposite sides of the zone. Others which run downwards and embrace the ventricles, and are also inserted on the opposite sides of the same zone, or that which surrounds the orifices of the aorta or pulmonary artery. The structure of the ventricular fibres is most complicated. They are first superfi- ciaUy placed, and as they make their spiral turns, sink deep into the substance of the heart, somewhat like the contours of a leaf of paper rolled into fhe form of a cone. They consist of fibres proper to each ventricle, and fibres common to both. The former, after arising from the zone, turn spirally around the axis of the ventricle, so as to form many times the figure of 8, and coming upon the anterior face of the same side, terminate upon the zone surrounding the arterial orifice. The fibres common to the ventricles are of two kinds—superficial and deep-seated. The superficial are divided into anterior and posterior. The an- terior arising from the anterior part of the arterial and auricular zones, run obliquely downwards and to the left, converging to- wards the apex of the heart; these are rolled around the axis of the left ventricle, and dip inwards to terminate in, or form the columnae carneae. The superficial part of this order of fibres, is common to both ventricles; the deep-seated part belongs to the left only. The posterior superficial fibres arise behind from * Mr. Home has given a precise description of the muscular fibres of the heart in his Croonian Lecture. London Philosophical Transactions for 1795, part I page 215. t Journal Complementaire du Diet, des Scienc. Med. torn. ix. p. 97.—p. CORONARY VESSELS. 467 the auricular zones only, and run downwards, so as to embrace the right border of the heart, come in front of the heart, and op- posite to the septum ventriculorum, dip under the anterior super- ficial fibres, wind round the axis of the right ventricle and ter- minate in its columnae carneae. These also in part only, are com- mon to both ventricles. —The deep-seated fibres form the internal part of the walls of the right ventricle. They arise from the fibrous zones of the right side. The anterior portion of these fibres runs obliquely downwards, and backwards to the septum; the posterior and in- ternal, pass at once into the septum, roll themselves round the left ventricle and are lost amidst the other fibres. Thus it ap- pears, that by removing the superficial layer of the common stra- tum, the heart may be divided into lateral halves, each consist- ing of two muscular sacs, an auricle and ventricle, adjoined to those of the opposite side in the middle line.— The external surface of the heart is covered by that portion of the pericardium which adheres to it. Adipose matter is often deposited between this membrane and the muscular surface ; be- ing distributed irregularly in various places. This membrane is continued from the surface of the ventricles over that of the auricles. When it is dissected off from the place of their junction, these surfaces appear very distinct from each other. The proper blood-vessels of the heart appear to be arranged in conformity to the general laws of the circulation, and are very conspicuous on the surface. There are two arteries which arise from the aorta immediately after it leaves the heart, so that their orifices are covered by two of the semilunar valves. One of these pass from the aorta between the pulmonary artery and the right auricle, and continues in a circular course in the groove between the right auricle and the right ventricle, and sends off its principal branches to the right side of the heart. The other artery of the heart passes between the pulmonary artery and the left auricle. It divides into two branches : one, which is anterior, passes to a groove on the surface, correspond- 468 VESSELS AND NERVES OF THE HEART. ing to the septum between the two ventricles, and continues on it to the apex of the heart, sending off branches in its course; another, which is posterior and circumflex, passes between the left auricle and ventricle. The great vein of the heart opens into the under side of the right auricle, as has been already mentioned: the main trunk of this vein passes for some distance bewteen the left auricle and ventricle.* From the course of these different vessels round the basis of the ventricles of the heart, they are generally called Coronary Vessels: the arteries are denominated, from their position, Right and Left Coronary. The nerves of the heart come from the cardiac plexus, which is composed of threads derived from the intercostal or great sympathetic nerves, and the nerves of the eighth pair. * It was asserted by Vicussens, at an early period in the last century, and soon afterwards by Thebesius, a German Professor, that there were a number of small orifices in the texture of the heart, which opened into the different cavities on both sides of it. This assertion of a fact so difficult to reconcile with the general principles of the circulation, was received with great hesitation: and although it was confirmed by some very respectable anatomists of the last century, it was denied by others. Some of the anatomists of the present day have denied the existence of these ori- fices, and some others have neglected them entirely. The subject has lately been brought forward in the London Philosophical Transactions of 1798, Part I. by a very respectable anatomist, Mr. Abernethy, who states that he has often passed a coarse waxen injection from the proper ar- teries and veins of the heart into all the cavities of that organ, and particularly into the Left Ventricle. But it was only in subjects with diseased lungs that this was practicable. The existence of this communication between the coronary vessels and the great cavities of the heart seems therefore to be proved. The easy demonstration in such subjects is ingeniously referred by Mr. Abernethy, to the obstruction of the circulation in the lungs ; and he regards the communication as a provision en- abling the coronary vessels to unload themselves, when the coronary vein cannot discharge freely into the right auricle.* * This assertion of Mr. Abernethy's, has not been confirmed by subsequent investigations, except in cases where the tissue of the heart was softened, and its vessels had been ruptured by the force of the injection.—p. GREAT VESSELS OF THE HEART. 469 Of the Aorta, the Pulmonary Artery and Veins, and the Vena Cava; at their commencement. The two great arteries, which arise from the heart, commence abruptly, and appear to be extremely different in their com- position and structure from the heart. They are composed of a substance, which has a whitish co- lour, and very dense texture, and is very elastic as well as firm and strong. When the pericardium is removed, these arteries appear to proceed together from the upper part of the basis of the heart: the pulmonary artery being placed to the left of the aorta with the left auricle on the left side of it, and the right auricle on the right side of the aorta. The pulmonary artery arises from the most anterior, and left part of the basis of the right ventricle, and proceeds obliquely backwards and upwards ; inclining gra- dually to the left side for about eighteen or twenty lines; when it divides into two branches which pass to the two lungs. The aorta arises from the left ventricle, under the origin of the pulmonary artery, and immediately proceeds to the right, covered by that vessel, until it mounts up between it and the right auricle: it then forms a great curve, or arch, which turns backward and to the left, to a considerable distance beyond the pulmonary artery. In this course, it crosses the right branch of the pulmonary artery ; and, turning down in the angle between it and the left branch, takes a position on the left side of the spine. The course of this artery, from its commencement at the ven- tricle, to the end of the great curve or arch, is extremely varied. The uppermost part of the curve is in the bottom of the chamber formed by the separation of the lamina of the medias- tinum when they join the first rib on each side. From this part of the curve three large branches go off, namely, one, which soon divides into the carotid and the sub- clavian arteries of the right side; a second, somewhat smaller, which is the left carotid; and a third, which is the left subclavian artery. , When the heart and its great vessels are viewed from be- VOL. I. 40 470 PULMONARY ARTERY AND VEINS. A b k hind, (after they have all been filled with injection; and the pericardium, mediastinum, and windpipe have been re- moved,) the aorta appears first, descending behind the other vessels; the pulmonary artery then appears, dividing so as to form an obtuse angle with its two great branches, each of which divides again before it enters the lung to which it is destined. Under the main trunk of the pulmonary artery is the left auricle: its posterior sur- face is nearly of a square form, and each of the pulmo- nary veins proceeds from one of its angles. These veins ramify in the substance of the lungs, at a very short distance from the auricle: the two uppermost of them are situated rather anterior to the branches of the pulmonary artery. In this posterior view, the pulmonary vessels of the right side cover a great part of the right auricle, as it is anterior to them. The lower portion of the auricle, with the termination of the inferior cava, is to be seen below them. Above them the su- * Fig. 40.—a, Left ventricle. 6, Right ventricle, c, Right auricle. The left auricle is seen above the left ventricle of the same side, d, Vena cava inferior, e, Subclavian and jugular veins; those of the left side unite to form the vena trans- versa ; those of the right, to form the vena innominata; the junction of these larger trunks, constitutes the vena cava superior or descendens. /, Left carotid. g, Left subclavian artery, arising from the arch of the aorta, h, Descending aorta. i, k, Right subclavian, and right carotid, given off from the arteria innominata, which is seen arising from the arcli of the aorta. I, Pulmonary artery, dividing into two branches, one for each lung—the left passing in front of the descending aorta, the right, behind the aorta, where it begins to form the curve, m, Vena cava superior, n, Aorta, o, Left pulmonary veins, entering auricle of same side. The right pulmonary veins, are seen on the opposite side, p, p, Lungs, t, Trachea.—p. VENjE CAViE. 471 perior cava appears; and in that part of it which is immediately above \he right branch of the pulmonary artery, is the orifice of the vena azygos. In its natural situation in the thorax, the superior cava is con- nected by cellular membrane to the right lamen of the medias- tinum, and is supported by it. At a small distance below the upper edge of the sternum, it receives the trunk formed by the left subclavian and internal jugular vein, which passes obliquely across the sternum below its inner edge, in the upper space between the lamina of the mediastinum. 472 OF THE TRACHEA. CHAPTER XVII. OF THE TRACHEA AND THE LUNGS. Although the principal part of the windpipe is situated in the neck above the cavity of the thorax, it is so intimately connected with the lungs, that it is necessary to describe them together. Of the Trachea. Trachea is the technical name for the windpipe, or the tube which passes from the larynx to the lungs. This tube begins at the lower edge of the cricoid cartilage, and passes down the neck in front of the oesophagus as low as the third dorsal vertebra, when it divides into two branches called Bronchia, one of which goes to the right and the other to the left lung, and ramifies very minutely in them. —The right bronchium is larger than the left, in proportion to the greater size of the right lung. It is also shorter and placed, more anterior, and more horizontal than the left, in consequence of the right lung being shorter in its vertical diameter, and longer in its antero-posterior than the lung of the left side. It enters near the centre of the root of the lung, opposite to the fourth dorsal vertebra. —The left bronchium terminates or enters the root of the left lung, opposite the fifth dorsal vertebras. The right bronchium is embraced at its upper part by the vena azygos, the left by the arch of the aorta.— There is in its structure, a number of flat cartilaginous rings placed at small distances from each other, the edges of which are connected by membrane, so that they compose a tube. These cartilaginous rings are not complete, for they do not form more than three-fourths or four-fifths of a circle ; but their ends are connected by a membrane which forms the posterior part of the tube. They are not alike in their size or form; some of them are STRUCTURE OF THE TRACHEA AND BRONCHIA. 473 rendered broader than others, by the union of two or three rings with each other, as the uppermost. The lowermost also is broad, and has a form which is accommodated to the bifurcation of the tube. Their number varies in different persons, from fif- teen to twenty. These rings may be considered as forming a part of the first proper coat of the trachea; which is composed of them, and of an elastic membrane that occupies all the interstice between them; so that the cartilages may be regarded as fixed in this membrane. A similar arrangement of rings exists in the great branches of the bronchia; but after they ramify in the lungs, the carti- lages are no longer in the form of rings: they are irregular in their figures, and are so arranged in the membrane, that they keep the tube completely open. These portions of cartilage do not continue throughout the whole extent of the ramifications; for they become smaller, and finally disappear, while the mem- branous tube continues without them, ramifying minutely, and probably forming the air-cells of the lungs. This membrane is very elastic: the lungs are very elastic also; and it is probable that their elasticity is derived from this membrane. On the inside of this coat of the trachea is an arrangement of muscular fibres, which may be called a muscular coat. It is best seen by peeling off or removing the internal coat, to be next described. ^ On the membranous part of the trachea, where the cartilagi- nous rings are deficient, these muscular fibres run evidently in a transverse direction: in the Fig. 41.* * Ficr. 41, represents the larynx, trachea, and bronchia; on the right side is seen the lung; on the left, the lung has been destroyed to show the ramification of the 40* 474 OF THE TRACHEA. spaces between the cartilages their direction is longitudinal. There is some reason to doubt whether these longitudinal fibres are confined altogether to the spaces between the cartilaginous rings, and attached only to their edges, because there is a fleshy substance on the internal surface of the rings, which appears to be continued from the spaces between them. The internal coat of the trachea is a thin and delicate mem- brane, perforated with an immense number of small foramina, which are the orifices of mucous ducts. On the surface of this membrane there is an appearance of longitudinal fibres which are not distributed uniformly over it, but run in fasciculi in some places, and appear to be deficient in others. These fasciculi are particularly conspicuous in the rami- fications of the bronchia in the lungs. —Many of the German anatomists have described these as longitudinal muscular fibres, the object of which is to shorten to some extent the air-passages during their contraction, and to as- sist in loosening the mucus and other matters which accumulate in their cavities. I have examined these carefully in the ox and elephant, where they are strongly marked; they appeared to me to consist only of longitudinal folds of mucous membrane, with a fibro-cellular basis.— On the posterior membranous portion of the trachea, where the cartilages are deficient, a considerable number of small gland- -ular bodies are placed, which are supposed to communicate with the mucous ducts that open on the internal surface. If these bo- dies are removed from the external surface of this portion, and the muscular fibres are also removed from the internal, a very thin membrane only remains, which is very different from that which is left between the rings, when the fleshy substance is re- moved from that situation. The reason of the deficiency in the rings, at this posterior part, is not very obvious.* It continues in the bronchia until the form bronchia, a, Larynx, b, Trachea, dividing into right and left bronchium; the left is the smaller, longer, and inclined most downwards, c, Larger divisions of the left bronchium. e, The more minute, d, Right lung.—p. * Dr. Physick has advanced the opinion that it enables a person to expel the OF THE LUNGS. 475 of their cartilages is changed in the lungs: if it were only to accommodate the oesophagus, during the passage of food, there would be no occasion for its extension to the bronchia. At the bifurcation of the trachea, and on the bronchia, are a number of black-coloured bodies, which resemble the lymphatic glands in form and texture. They continue on the ramifications of the bronchia some distance into the substance of the lungs. Their number is often very considerable; and they vary in size from three or four lines in diameter to eighteen or twenty. As lymphatic vessels have been traced to and from them during their course to the thoracic duct, they are considered as lym- phatic glands. Of the Lungs. There are two of these organs : each of which occupies one of the great cavities of the thorax. When placed together, in their natural position, they resemble the hoof of the ox, with its back part forward ; but they are at such a distance from each other, and of such a figure, that they allow the mediastinum and heart to intervene; and they cover every part of the heart anteriorly, except a small portion at the apex. Each lung fills completely the cavity in which it is placed, and every part of its external surface is in contact with some part of the internal surface of the cavity; but when in a natural and healthy state, it is not connected with any part except the lamina of the mediastinum. —The lower extremity or base of each lung, rests upon the pleural lining of the diaphragm, and fills up the angle between the diaphragm and the ribs; and the upper projects upwards, and backwards, along the first rib above the level of the clavicle, so as to be separated from the scalenus anticus muscle, only by the pleura. In laborious respiration, the elevation of the apex of the lung is increased, and the motion it produces becomes visible at the root of the neck. The external face of the lungs mucus of the lungs by contracting the size of the trachea, and consequently in- creasing the velocity or impetus of the air.—h. 476 ROOT OF THE LUNGS. is concave, to suit the contour of the thoracic parietes. The in- ternal and especially that of the left, is concave to accommo- date the heart and pericardium. The anterior edge is thin and sinuous, and presents on the left side a deep notch fitted to the shape of the heart, and a sort of lobular projection which in part covers that organ during deep inspiration.— One great branch of the trachea and of the pulmonary artery passes from the mediastinum to each lung, and enters it at a place which is rather nearer to the upper rib than to the diaphragm, and much nearer to the spine than the sternum: at this place also the pulmonary veins return from the lungs to the heart. These vessels are enclosed in a membrane, which is continued over them from the mediastinum, and extended from them to the lung. Thus covered they constitute what has been called the Root of the Lung. When their covering, derived from the mediastinum, is re- moved, the situation of these vessels appears to be such that the bronchia are posterior, the branches of the pulmonary artery are rather above and before, and the veins below and before them. Each of these vessels ramifies before it enters into the sub- stance of the lungs: the bronchia and the branches of the pul- monary artery send each a large branch downward to the infe- rior part of the lungs, from which the lower pulmonary veins pass in a direction nearly horizontal. In general, each of the smaller ramifications of the bronchia in the lungs is attended by an artery and a vein. Each lung is divided, by very deep fissures, into portions which are called Lobes. The right lung is composed of three of these lobes, and the left lung of two. (See Fig. 40, page 470.) —Each of these lobes are subdivided into various smaller parts called lobules, which are marked out on the surface of the lungs, by various angular lines. Each bronchium divides into two principal branches for the lobes of the left lung, and into three for the right; after which, a still further subdivision takes place, so that a terminal bronchial branch is sent to each lobule.— The lungs are covered, as has been already stated, with the COLOUR OF THE LUNGS. 477 reflected portion of the pleura continued from the mediastinum, which is very delicate and almost transparent. They have, therefore, a very smooth surface, which is kept moist by exuda- tion from the arteries of the membrane. The Colour of the Lungs is different in different subjects. In children they are of a light red colour; in adults they are often of a light gray; owing to the deposition of a black pigment in the substance immediately under the membranes which form their external surface. Their colour is often formed by a mixture of red and black. In this case they are more loaded with blood, and the vessels of the internal membranes being distended with it, the red colour is derived from them. The black pigment sometimes appears in round spots of three or four lines in diameter: under the external membrane it is often in much smaller portions, and sometimes is arranged in lines in the interstices of the lobuli, to be hereafter mentioned. It is also diffused in small quantities throughout the substance of the lungs. The source of this substance, and the use of it, are unknown. The lungs are of a soft spongy texture; and, in animals that have breathed, they have always a considerable quantity of air in them. They consist of cells, which communicate with the branches of the trachea that ramify through them in every part. These cells are extremely small, and the membranes which compose them are(so thin and delicate, that if they are all filled by an in- jection of wax, thrown into the trachea, the whole cellular part of the lung will appear like a mass of wax. If a corroded pre- paration be made of a lung injected in this manner with force, the wax will appear like a concretion. These effects of injections prove that the membranes of which the cells are formed are very thin; and, of course, that their volume is very small when compared with the capacity of the cells . c ' In those corroded preparations, in which the ramifications of the bronchia are detached from the wax of the cells, these rami- fications become extremely small indeed. 478 STRUCTURE OF THE LUNGS. If the lungs of the human subject, or of animals of similar construction, be examined when they are inflated, their cellular structure will be very obvious, although their cells are so small that they cannot commonly be distinguished by the naked eye. Each of the extreme ramifications of the bronchia appears to be surrounded by a portion of this cellular substance, which is gra- dually distended when air is blown into the ramification. This cellular substance is formed into small portions of various angular figures, which are denominated Lobuli: these can be separated to a considerable extent from each other. They are covered by the proper coat of the lungs, which is extremely delicate, and closely connected to the general covering derived from the pleura. Between the lobuli, where they are in contact with each other, there is a portion of common cellular substance, which is easily distinguished through the membrane covering the lungs. This is very distinct from the cellular structure which communicates with the ramifications of the bronchia, and con- tains air; for it has no communication with the air, unless the proper coat of the lungs be ruptured. If a pipe be introduced by a puncture of the external coat of the lungs, and this inter- stitial cellular membrane be inflated, it will compress the lobuli. This cellular membrane is always free from adipose matter: it may be easily examined in the lungs of the bullock. Upon the membranes which compose the air-cells, the pulmo- nary artery and vein ramify most minutely; and it seems to have been proved within the last thirty years, by the united labours of chemists and physiologists, that the great object of respiration is to effect a chemical process between the atmospheric air, when taken into the air-cells, and the blood which circulates in these vessels. In addition to the blood-vessels which thus pass through the substance of the lungs, there are several smaller arteries deno- minated Bronchial, which arise either from the upper intercostal, or from the aorta itself: they pass upon the bronchia, and are distributed to the substance of the lungs. The veins which correspond with these arteries terminate ultimately in the vena azygos. STRUCTURE OF THE LUNGS. 479 The nerves of the lungs are small in proportion to the bulk of these organs. They are derived principally from the par vaguni and the intercostal nerves. —They form one plexus on the front, and another on the pos- terior surface of the bronchia, along which they are conducted to the minutest subdivision of the latter in the substance of the lungs.— The elasticity of the air-cells of the lungs and of the rami- fications of the bronchia which leads to them, is apparent in their rapid contraction after distention, and by the force with which they expel the air which is used to inflate them when taken out of the thorax. —The specific gravity of the lungs is not naturally greater than that of many other tissues. In a still-born child, sections of it sink in water like a piece of muscle. But when its cells have been once distended by air in respiration it becomes im- possible to extrude it completely, unless it is subjected to strong compression, and the lung floats upon the water and appears to have the least specific gravity of all the animal tissues. The lungs are endowed with a considerable degree of elasticity, which appears to be derived from the elastic tissue of the bron- chia which is spread universally through the lungs. When dis- tended they have a constant tendency either in or out of the body to return upon themselves and expel the air. —It will now be seen that the proper tissue of the lungs, the parenchyma, the areolar tissue, is very complicated. It consists of the cells of the bronchia for the reception of air, which are formed internally of mucous membrane, and externally most probably of a thin expansion of the yellow elastic ligamentous layer of the bronchia; of a branch of the pulmonary arteries and veins, which run over the outer surface of the cells, the former bringing the black blood, and the latter conveying it away after it has been changed by the action of the air through the walls of the cells; of the bronchial arteries and veins for the purpose of nutrition'; of absorbent vessels to remove the molecules as they become effete; of filaments of the sympathetic and par vagum nerves, which preside over the function of heemoptosis, and put 480 THORAX OF THE FCETUS. the lungs in connexion with the brain; and lastly of cellular tissue which unites the whole together. —Between the bronchial and pulmonary arteries and veins, there is an intimate anastomosis so that either system of vessels may be filled by the use of fine injecting fluid through the other. The cells of each lobule, according to Professor Horner, Cloquet, and some other anatomists of distinction, communicate laterally with each other. The diameter of these cells has been mea- sured by Weber of Leipzig,* by the aid of a micrometer attached with extreme care and ingenuity to a microscope. According to him they are upon an average about ^g^th part of an inch in diameter, which makes them five or six times larger than the cells of the parotid gland, and fifteen or twenty times larger than the finest capillary blood-vessels measured on a portion of skin which had been very perfectly injected by Dr. Pockels of Brunswick.— The Thorax of the Fatus. In the cavity between the lamina of the mediastinum, where they approach each other from the first ribs, is situated a sub- stance which is denominated the Thymus Gland. This substance gradually diminishes after birth, so that in the adult it is often not to be found : and when it exists it is changed in its texture, being much firmer, as well as greatly diminished. In the foetus it is of a pale red colour; and during infancy it has a yellowish tinge. It generally extends from the thyroid gland, or a little below it, to the pericardium. From its superior portion two lateral processes are extended upwards: below, it is formed into two lobes, which lie on the pericardium. If an incision be made into its substance, a fluid can be press- ed out, which has a whitish colour, and coagulates upon the addition of alcohol. Although it is called a gland, no excretory duct has ever been found connected with it. * Meckel's Archiv. fur Anat. und Physiol., 1830.—p. THE THORAX OF THE FCETUS. 481 The blood-vessels of this body are derived from the thyroid branches of the subclavians, from the internal mammaries, and the vessels of the pericardium and mediastinum. The Heart, And the great arteries which proceed from it, have some very interesting peculiarities in the foetus. In the septum between the two auricles, is a foramen of suffi- cient size to permit the passage of a large quill, which inclines to the oval form, with its longest diameter vertical when the body is erect. On the left side of the septum, a valve, formed by the lining membranes, is connected to this foramen; and allows a free passage to a fluid moving from the right auricle to the left; but prevents the passage of a fluid from the left to the right. This structure is evidently calculated to allow some of the blood which flows into the right auricle from the two venae cava? to pass into the left auricle of the heart, instead of going into the right ventricle. As the contents of the left auricle pass into the left ventricle, and from thence into the aorta, it is obvious that the blood which passes from the right auricle into the left through this foramen, must be transmitted from the system of the vena cava to the system of the aorta, without going through the lungs, as it must necessarily do in subjects who do not enjoy the fcetal structure. —The valve, with which in the foetus the foramen ovale is pro- vided, on the side of the left auricle, is of a semilunar shape and called the valve of Botal; it has a convex border, adherent, and turned downwards; and a concave border, free, and turned up- wards. The angles resulting from the union of these borders are attached to each side of the foramen about a quarter of an inch distant from each other at birth. The valve makes its appearance in the foetus at the third month of intra-uterine existence, and gradually increases in size, so as to more than cover the foramen at the period of birth. When the child breathes and the lungs become filled with blood, the fluid, entering the left auricle by the pulmonary veins, throws down the valve against the septum VOL. I. 41 482 THE THORAX OF THE FCETUS. auriculorum, to which its free border usually becomes firmly united. —Occasionally, however, the union of the parts is found so in- complete, even in old persons, as to allow a probe or even the handle of a scalpel to be passed obliquely through the opening: the obliquity of the orifice being such, as usually to enable it to act as a perfect valve. A communication of this sort, of greater or less magnitude between the auricles, exists in adults in the ratio of one to four. Sometimes the foramen is met with in adults di- lated so as to be nearly an inch in diameter. I have met with two cases of this sort in the dissecting-room, both of which occurred in females between twenty and thirty years of age. The nutri- tive functions appeared to have been perfectly well performed in both these subjects, judging from the state of the body; the right auricle and ventricle were dilated and hypertrophied so as to pre- sent the same thickness of parietes as the corresponding parts of the left side. The tricuspid valves, and the semilunar valves of the pulmonary artery were thickened, and presented cartilaginous con- cretions on their edges, in which the work of ossification had just commenced. This thickening and ossification of the valves is almost wholly peculiar in the normal formation of the heart to the valves of the left side, and appears to be caused, as was first suggested by Cruveilhier, by the force with which the blood is dashed against the valves, in the forcible contractions of the ventricle.— The Pulmonary Artery and the Aorta Have a communication in the foetus, which is very analogous to the communication between the auricles of the heart. From the pulmonary artery, where it divides into the two great branches, another large branch continues, in the direction of the main trunk, until it joins the aorta; with which it com- municates at a small distance below the origin of the left sub- clavian artery. In the young subject that has never respired, it appears as if the pulmonary artery was continued into the aorta, and sent off in its course a branch on each side, much smaller than itself, to each lung. In subjects that have lived a few days, GENERAL OBSERVATIONS. 483 these branches to the lungs are much larger; and then the main pulmonary artery appears to have divided into three branches: one to each lung, and one to the aorta; but that which continues to the aorta is larger than either of the others. In the course of time, however, this branch of the aorta is contracted, so that no fluid passes through it; and it has the ap- pearance of a ligament, in which state it remains. The course of the blood from the right ventricle, through the pulmonary artery, to the aorta below its curve, is more direct than that from the left ventricle to the same spot, through the aorta at its commencement. The column of blood in the aorta below its curve is evidently propelled by the force of both ven- tricles: and this circumstance, although it seems to proceed merely from the state of the foetal lungs, is particularly calcu- lated for the very extensive circulation which the foetus carries on, by means of the umbilical arteries and vein in the placenta. The Lungs of the Foetus Differ greatly from those of the adult. They appear solid, as if they were composed of the parenchymatous substance which constitutes the matter of glands, rather than the light spongy substance of the lungs of adults. They differ also in colour from the lungs of older subjects, being of a dull red. They have greater specific gravity than water; but if air be once inspired, so much of it remains in them that they ever af- terwards float in that fluid. The nature of the process of respiration, and its effects upon the animal economy, particularly upon the action of the heart, appear to be much better understood at this time than they were before the discovery of the composition of the atmosphere, by Dr. Priestley and Mr. Scheele. The publications upon this subject, which have appeared since that period, namely 1774, are therefore much more interesting to the student of medi- cine than those which preceded them. Two of these publicaUons ought to be particularly noticed by him; namely, an essay, by Dr. Edward Goodwyn, entitled, "The Connexion of Life wi* ^8P™to^^^ « Physiological Researches of M. Bichat upon Life and Death. Part Second.* . The student will derive much information respecting the publications on this subject, prior to 1804, from Dr. Bostock's Essay on Respiration.-Since the pubh- 484 CASES OF MALFORMATION. The general doctrines respecting the oxygenation or decarbonization of the blood and the absolute necessity that it should take place to a certain de- gree in order to preserve life, are confirmed by a number of cases of mal- formation of the heart or the great vessels, in which the structure was such that a considerable portion of venous blood passed from the right side of the heart to the aorta, without going through the lungs. In these different cases, notwithstanding the structure was somewhat varied, the symptoms produced were very much alike; differing in the respective pa- tients in degree only, and not in kind. The symptoms indicating this structure, are blue colour of the face, (such, as generally accompanies suffocation,) extending more or less over the whole body, and particularly apparent under the nails of the fingers and toes; anxiety about the region of the heart; palpitation; laborious respi- ration ; sensations of great debility, &c.: all of which are greatly aggra- vated by muscular exertion. These effects have generally appeared to be proportioned to the quantity of venous blood admitted into the aortic system.* When these appearances take place immediately after birth, it is probable that they depend entirely upon malformation of the heart or great vessels; but when they commence at a subsequent period, they are commonly the effect of a diseased alteration in the lungs. They sometimes occur near the termination of fatal cases of pneumonia or catarrh; but a different cause, which has not latterly been suspected, appears to have produced them in the following case, related by Dr. Marcet, in the first volume of the Edinburgh Medical and Physical Journal. The blue colour occurred in a young woman, twenty-one years of age, in whom it had never been observed before. It came on during an affection of the breast, and was attended with great prostration of strength and dif- ficulty of breathing; as well as cough, oedema of the hands and feet, and several other symptoms. About seven weeks after the commencement of these symptoms, she died; when it was ascertained by dissection, cation of that essay several interesting papers on respiration have appeared, namely, Two Memoirs by the late Abbe Spalanzani; "An Inquiry into the Changes induced on Atmospheric Air by the Germination of seeds," &c, by Ellis; two very important communications by Messrs Allen and Pepys in the Trans- actions of the Royal Society of London for 1808 and 1809 ; and "Farther In- quiries into the Changes induced on Atmospheric Air," also by Ellis. * Cases of this kind are related in several of the periodical publications on me- dical subjects. Two of them were described by the late Dr. William Hunter in the sixth volume of Medical Observations and Inquiries, by a Society of Physi- cians in London; one quoted by Dr. Goodwyn, is in the Observationes Anatomi- cal of Sandifort; and another by Dr. J. S. Dorsey, has lately been published in the first number of the New England Journal of Medicine and Surgery. EFFECT OF VENOUS BLOOD ON THE HEART. IS.J that there was no unnatural communication whatever between the cavi- ties of the heart, and that its valves were all in a perfect and natural state. The lungs were free from tubercles, or any other appearance of disease. Their substanee seemed more compact than usual, especially the left lung, although it did not sink in water; but they adhered every where to the inner surface of the thorax, to the diaphragm and to the pleura covering the pericardium.—This case is the more remarkable, be- cause numberless instances have occurred, in which very large portions of the external surface of the lungs have been found, upon dissection, to adhere to the internal surface of the thorax, without the occurrence of such symptoms during life. It may be inferred, from a statement published by M. Dupuytren, in a late volume of the Proceedings of the National Institute of France, that the oxygenation or decarbonation of the blood is much affected, in respiration, by an influence exercised by the nerves which are appropriated to the lungs. From his account it appears, that although the complete division of the eighth pair of nerves produces death after some time; yet in the horse, whose nerves are thus divided, life continues, and respiration goes on, from half an hour to ten hours; but his arterial blood is in a state of great disoxygenation or carbonation during this time. This fact is more remarkable because venous blood, contained in a bladder exposed to the open air, will become oxygenated or decarbonated. It is also asserted in another Memoir, read to the National Institute by Dr. J. M. Provengal; that animals, in whom the eighth pair of nerves has been divided, do not consume so much oxygen, or produce so much carbonic acid, by a considerable degree, as they did before the division of these nerves ; and that their temperature is considerably reduced.* The effect, that venous blood occasions death, when it is admitted into the left ventricle of the heart, and the aorta, is truly important. Dr. Good- win explained it by suggesting that this blood was not sufficiently stimu- lating to produce the necessary excitement of the heart; but on this oc- casion one of his friends proposed to him the following question : Why does venous blood affect the left side of the heart in this injurious manner, * These Memoirs are republished in the Eclectic Repertory of Philadelphia for April and October, 1811. 41* 486 SENTIMENTS OF SABATIER, ETC. when it appears to exert no noxious effects whatever on the right side of that organ 1 His reply may be seen in a note at the 82d page of his Essay, in the first edition. Bichat has offered a solution which completely resolves this difficulty, viz. " The effect of venous blood upon the heart is pro- duced by the presence of this blood in the proper, or coronary arteries of that organ, and not in its great cavities." For the animation of the heart, like that of the other parts of the body, depends upon the state of the blood in the arteries which penetrate its texture.* And while the heart acts, the blood of the coronary arteries will be the same with that of the left ventricle. See Bichat's Researches, P. II. art. 6, 5,2. The French anatomists appear to entertain some peculiar opinions respect- ing the course of the blood in the foetus, which have a particular relation to the subject last mentioned. Winslow, who paid great attention to the valve of Eustachius in the right auricle of the heart, was of opinion, that this valve was calculated for some important purpose in the foetal econo- hiy.f Although his hypothesis respecting its particular use has not been retained by his countrymen, many of them have adopted his general sen- timent ; and among others Sabatier. That learned anatomist believed that this valve, in the foetal state, serves to direct the blood of the infe- rior cava, after its arrival in the right auricle through the foramen ovale into the left auricle; while the blood of the upper cava passes directly into the right ventricle. His opinion seems to be supported to a certain degree— 1. By the direction in which the two columns of blood enter the auricles from the two venae cava?. 2. By the position of the Eustachian valve. 3. By the foramen ovale, when its valve is complete; as the passage through it from the right to the left, is at that time oblique, and from below upwards. The theory of Sabatier appears to be this:—the umbilical vein brings from the placenta blood which has a quality essential to the animation of the foetus. If there were no particular provision to the contrary, a large por- tion of this blood, after passing from the umbilical vein by the inferior cava into the right auricle of the heart, would proceed by the right ven- tricle through the pulmonary artery and arterial canal, into the aorta, be- low the origins of the carotid and subclavian arteries; and consequently none of it would pass to the head and upper extremities, but a considerable * It is probable that the contents of the great cavities of the heart have no more effect upon its animation than the contents of the stomach and bowels have upon the animation of those organs. t See Memoirs of the Academy of Sciences for 1717 and 1725. SENTIMENTS OF SABATIER, ETC. 4Q7 part would return again by the umbilical arteries to the placenta, with- out circulating through the body: while, on the other hand, the blood which passed by the carotid and subclavian arteries to the head and up- per extremities returning from them to the heart by the superior cava, might pass from the right auricle to the left auricle and ventricle and the aorta, and so to the head and upper extremities again, without passing through the placenta. But by means of this valve, the blood of the low er cava, and of course of the umbilical vein, is directed to the left auricle and ventricle and the aorta, by which a considerable portion of it will ne- cessarily pass to the head and upper extremities; while the blood which returns from these parts by the superior cava, must consequently pass from the right auricle into the right ventricle and pulmonary artery; from whence a large portion of it will proceed through the arterial canal into the aorta beyond the carotids and subclavians, and of this portion a con- siderable part will go to the placenta by the umbilical arteries. Sabatier compares the course of the blood in the foetus to the course of a fluid in a tube which has the form of the numeral character 8.* If this doctrine be true, the progress of the blood in the foetus and placenta is very analogous to that of the double circulation of the adult; the character 8 answering equally well in the description of either subject. According to Sabatier, the blood of the placenta takes this peculiar course through the heart, in order that some of it may be carried to the head and upper extremities. But an additional reason may be suggested, which appears to be of great importance; namely, the supplying of the coronary or proper vessels of the heart with some of the same blood. The heart of the adult, as has been before stated, cannot act without its pro- per or coronary arteries are supplied with arterial blood. The heart of the foetus performs a more extensive circulation than that of the adult, and, therefore, is probably in greater need of such blood. But ttnless the blood of the placenta pass through the foramen ovale into the left auricle and ventricle, and so to the aorta, it cannot enter the coronary arteries which originate at the commencement of the aorta ; for the blood which flows from the right side of the heart through the arterial canal, passes into the aorta at so great a distance from the orifices of the coronary ar- teries, that it certainly cannot enter them. The whole of this doctrine seems to be supported by a fact very familiar to accoucheurs, viz. the occurrence of death in the foetus whenever the cir- culation through the umbilical cord is suspended during fifteen or twenty minutes; for as the placenta imparts to the foetal blood a quality essential to life, some arrangement seems necessary to provide for the equal distri- * Sec Sabatier's Paper on this subject, in the Memoirs of the Academy of Sci- ences, for 1774. 488 UNUSUAL CASES OF MALFORMATION. bution of the blood which comes from this organ, and especially for carry- ing the requisite proportion of it to the substance of the heart. Life has existed for some time with a structure very different indeed from that which is natural. In the series of elegant engravings relating to morbid anatomy, published by Dr. Baillie, is the representation of a heart, in which the venae cavae opened into the right auricle, and the pulmonary veins into the left auricle, in the usual manner; but the aorta arose entirely from the right ventricle, and the pulmonary artery as completely from the left. The canalis arteriosus, however, passed from the pulmonary artery to the aorta, and the foramen ovale existed. In this case, it is evident, that the pulmonary artery must have carried back to the lungs the arterial blood which came from them by the pulmonary veins, with a small quantity of venous blood that passed into the left auricle through the foramen ovale; and that the aorta must have returned to the body the venous blood, which just before had been brought from it by the venae cavae, with a small ad- dition of arterial blood that passed through the ductus arteriosus. Yet with this structure the child lived two months after its birth. A case, which had a strong resemblance to the foregoing, occurred lately in Philadelphia, and was examined by the author of this work. The venae cavae terminated regularly in the right auricle, and the pulmonary veins in the same regular manner in the left; but the pulmonary artery arose from the left ventricle, and the aorta from the right. There was no com- munication between these vessels by a canalis arteriosus; but a large opening existed in the septum between the auricles. It is very evident, that, in this case also the pulmonary artery must have returned to the lungs the arterial blood as it came fr6m them, and the aorta must have carried back to the general system the venous blood brought to the heart by the cava?; excepting only those portions of the arterial and venous blood which must have flowed reciprocally from one auricle into the other, and thus changed their respective situations. The subject was about two years and a half old. The heart was nearly double the natural size, and the foramen, or opening in the septum between the auricles, was eight or nine lines in diameter. The pulmonary artery was larger in proportion than the aorta or the heart. With this organization, the child lived to the age above specified. His countenance was generally rather livid; and this colour was always much increased by the least irregularity of respiration. His nails were always livid. He sometimes appeared placid, but more frequently in distress. He never walked, and seldom, if ever, stood on his feet. When sitting on the floor, he would sometimes push himself about the room; but this muscular exertion always greatly affected his respiration. He attained FORAMEN OVALE. 489 the size common to children of his age, and had generally a great appetite. For some weeks before death his legs and feet were swelled. It is probable that the protraction of life depended upon the mixture of the blood in the two auricles; and that they really were to be considered as one cavity, in this case. There seems reason to believe, that in adults of the common structure, there is no passage of blood from one auricle to the other, when the foramen ovale has remained open; because in several persons in whom it was found by dissection to have remained open, there were no appearances during life, that indicated the presence of disoxygenated blood in the aortic system. It is probable, that the small size of the foramen ovale, the valvular structure which generally exists there, and the complete occupa- tion of the left auricle by the blood flowing from the pulmonary veins, prevent the passage of blood from the right auricle to the left, in such persons; whereas in the case in question, the opening between the auricles was very large indeed, and there was no appearance of a valve about it. Although it be admitted, that in adults with the foramen ovale pervious, there is no transmission of blood from the right to the left auricle ; there is every reason to believe, that this transmission goes on steadily in the foetus. To the arguments derived from the structure and the nature of the case, it may be added, that the pulmonary veins, in the foetal state, carry to the left auricle a Quantity of blood, not sufficient to fill it; while the venae cavae carry to the right auricle, not only the whole blood of the body, but of the umbilical cord and placenta : some of which must flow into the unfilled left auricle, when the right auricle becomes fully dis- tended. The question, how far the functions of the heart and lungs are dependen upon the brain, is very important, and has often been agitated with great zeal In favour of the opinion that the motions of the heart are indepen- dent of the brain, may be stated the numerous cases in -hich the brain has been deficient in children, who have notwithstanding lived the full Pe iod ot utero-gestation, and even a short time after birth, and have arrived at their full size, with every appearance of perfect vigour and action in Sefheart In support of the doctrine, that the action of the heart is im- Sly dependent upon the brain, it may be observed, that no organ of The body appears to be so much influenced by pass.ons and other mental 490 0N THE S0URCE OF THE MOTION OF THE HEART. affections as the heart. These contradictory facts have occasioned this question to be considered as undecided, if not incapable of solution; although Cruikshank and Bichat* have stated circumstances very favourable to the opinion that the motions of the heart are independent of the brain. This question seems now to be settled by the experiments of Dr. Legal- lois, a physician of Paris, which prove, that in animals who have suffered decapitation, the action of the heart does not cease as an immediate conse- quence of the removal of the head; but its cessation is an indirect effect, induced by suspension of respiration. That respiration is immediately affected by decapitation, and depends upon the influence of the brain transmitted through the eighth pair of nerves. That the action of the heart will continue a long time after decapitation, if inflation of the lungs, or artificial respiration, be performed; but, on the contrary, if the spinal marrow be destroyed, the action of the heart ceases irrecoverably. The inference from these experiments seems very conclusive, that the Spinal Marrow, and not the brain, is the source of the motions of the heart. It appears also by some of the experiments, that the power of motion in the trunk of the body, is derived from the spinal marrow; and that, when this organ is partially destroyed, the parts which receive nerves from the destroyed portion soon cease to live. By particular manage- ment of the spinal marrow, one part of the body can be preserved alive for some time after the other parts are dead. These experiments of Dr. Legallois, commenced in 1806, or 1807, and were communicated to the imperial Institute of France, in 1811. The committee of that body, to whom they were referred, namely, Messrs. Humboldt, Halle, and Percy, reported that the experiments had been re- peated before them, at three different meetings of several hours each; and that, to allow themselves sufficient time for reflection, they suffered an interval of a week to take place between the meetings. The committee believe these experiments to have proved, 1st. That the principle upon which all the movements of inspiration depend, has its seat about that part of the medulla oblongata from which the nerves of the eighth pair arise. * See Cruikshank's Experiments on the Nerves and Spinal Marrow of living Animals; London Philosophical Transactions for 1795. The eighth experiment has a particular relation to this subject. Bichat's Researches, part 2, article 9. The Abbe Fontana has considered this subject in his Treatise on the Venom of the Viper, vol. ii. page 194, English translation; and alsd in some of his other works. HUMBOLDT AND OTHERS ON LEGALLOIS' PAPER. 491 2d. That the principle which animates each part of the trunk of the body, is seated in that portion of the spinal marrow from which the nerves of the part arise. 3d. That the source of the life and strength of the heart is also in the Bpinal marrow; not in any distinct portion, but in the whole of it. 4th. That the great sympathetic nerve is to be considered as originating in the spinal marrow, and that the particular character of this nerve is to place each of the parts to which it is distributed under the immediate in- fluence of the whole nervous power. The interesting memoir of Dr. Legallois is confirmed to a certain degree by a communication of B. C. Brodie to the Royal Society of London in 1810, in which are detailed many very interesting experiments, which induced the author to conclude,— That the influence of the brain is not directly necessary to the action of the heart; and That when the brain is injured or removed, the action of the heart ceases only because respiration is under its influence; and if, under these circumstances, respiration is artificially produced, the circulation will still continue. These various experiments apply particularly to the cases in which the brain is deficient. The effects of mental agitation on the heart are like- wise reconcilable to the theory which arises out of them. But they throw no light on the question why the motions of the heart are so perfectly free from the influence of the will: and although they seem to prove incon- testably that the motion of the heart is independent of the brain, it ought to be remembered that in certain diseased states of the brain, where that organ appears to be compressed, the action of the heart is often very irre- gular, and its contractions less frequent than usual. END OF VOL. I. NLM032048270