ON MORPHOLOGY AND TELEOLOGY, ESPECIALLY IN THE LIMBS OF MAMMALIA. By BURT 0. WILDER, S.B. I FROM THE MEMOIRS READ REFORK THE BOSTON SOCIETY OF NATURAL HISTORY, VOL. I. NO. I.] CAMBRIDGE: PRINTED AT THE RIVERSIDE PRESS. November, 1865. ON MORPHOLOGY AND TELEOLOGY. ESPECIALLY IN THE LIMBS OF MAMMALIA. By BURT G. WILDER, S.B. [FROM THE MEMOIRS READ BEFORE THE BOSTON SOCIETY OF NATURAE HISTORY, VOL. I. NO. I.] CAMBRIDGE: PRINTED AT THE RIVERSIDE PRESS. November, 1865. ON MORPHOLOGY AND TELEOLOGY, ESPECIALLY IN THE LIMBS OF MAMMALIA. BURT G. WILDER, S. B. Read June 3d, 1863. It is not many years since the very title of this paper would have been enough to insure its remaining unread by most professional men, or, if read, to excite their derision of him who should have so wasted his time as to write, or even think, of such vain abstractions, fit expressions of the useless imaginings of the half-crazy enthusiast Oken, and his only less crazy, because less gifted, disciples. And there are, even now, stern votaries of practical science who would scorn any attempt to raise their eyes above the mere facts of Nature which are as patent to the ignorant vision as to their own, and who refuse to seek an insight into those hidden relations, for the correct understanding of which their superior knowledge might be the surest preparation. But there are others, and their number is increasing, who, believing in the existence of a general plan underlying all the more external phenomena of Nature, are willing to try to comprehend it in its greater and lesser manifestations; and they, in reading the “ Physio- philosophy,” may be able to discern, amongst much that is fanciful and absurd, many sug- gestions of a sound as well as original and striking philosophy. No apology, therefore, is now required for thinking or writing upon subjects which have engaged the attention of the most celebrated students of both animal and vegetable anatomy, and which, I am con- vinced, will, erelong, be acknowledged to be as essential to the proper understanding of these sciences as the classifications of which they form the only true basis. To express the various relations which have been observed among the several parts and their functions, of animals and plants, the following terms have gradually come into use: homology, affinity, morphology, analogy, teleology; to these may be added physiology, which, though a term long employed to denote the general study of function, has now acquired a certain technical significance, equivalent to the more strictly scientific, and therefore preferable term, teleology. Analogy is used to indicate similarity of function, which may be very close, when yet the two parts are widely dissimilar in structure; as, for instance, the organs of aerial locomotion of a bird and a butterfly, which both go by the name of wings, though one is built upon the vertebrate, and the other upon the articulate plan of structure. Of course the structure may correspond with the external form and function, and then the analogy is more com- plete, as between the foot of man and that of a bear. Now the general function or use of a part is its physiology • the special or principal use of a part is its final cause or end, or teleology; and parts which are teleologically similar are said to be analogous. It is evident that the external form and the function must to a great extent correspond, at least much more fully than either may with the internal structure, and here we observe the first distinction between the two groups of terms given above; for this intimate structure and arrangement, in other words, the pure anatomy of anything, is its morphology, and parts which are morphologically similar are said to be homologous ; there is homology or affinity, or, in still plainer words, more or less identity of structure between them; and here again, as was seen in speaking of analogy, parts or organs which are homologous, that is, identical in their 2 WILDER ON MORPHOLOGY AND TELEOLOGY general plan of structure, may be intended to perform functions most diverse, and their out- ward forms be in like degree modified. For instance, the fin-like flipper of the seal bears little resemblance to the anterior extremity of the ape, and yet they are identical in their general structure, — they are homologous. It may have been inferred, from what has been said above, that we have necessarily two systems of nomenclature, according as morphology or teleology is taken as the basis. For it is the latter which confers common and popular names on objects of Natural History, and arranges them in a way which, though convenient enough under ordinary circumstances, utterly fails of precision for all scientific purposes; and the anatomist and zoologist soon learn that morphology alone must be their guide in scientific nomenclature. Thus the name fish is applied to several animals in structure very unlike the true Pisces, merely be- cause, like that group of Vertebrates, they live in the water: to certain Radiates, as the star-fish and sun-fish; to Articulates, as the cray-fish; and, formerly, even to the whale, an air-breathing Mammalian Vertebrate. So among Articulates, the monosyllable fly forms the ending of the common names of many insects, as butter-fly, dragon-fly, harvest-fly, ichneu- mon-fly, members respectively of the sub-orders Lepidoptera, Neuroptera, Hemiptera, and Hymenoptera, though it is only to the Diptera that the name fly properly belongs. These are zoological ambiguities; anatomical ones are even more frequent. All organs of aerial locomotion are commonly called wings, whether they are articulate or vertebrate in type, or whether, within the latter group, they are avian or mammalian, as those of the bats; and the same is the case with other parts and organs, thorax, abdomen, heart, liver, and stomach. I could not well pass over this most important branch of the subject; but the great ne- cessity to the philosophical naturalist for a revised anatomical nomenclature has already been strongly urged by Professor Agassiz, before the Boston Society of Natural History.1 Premising that the members of the four great types have nothing in common beyond their all being animals, and that, therefore, no parts, however similar in function, can pos- sibly be homologous in animals belonging to any two of these types, he showed the propri- ety of restricting the common names mouth, stomach, heart, and the like, to one of these groups, the Vertebrates perhaps, and of applying other names to the analogous parts in the other three types. Perhaps the change should be even greater than this; for, since these new names would of course be classical in their derivation, and the common ones, though scientifically restricted, would in general discourse retain the same loose application, it would seem better to employ new terms for the various parts and organs in each of the four types, leaving the common ones as they are now. It is evident that much remains to be done in this matter of anatomical nomenclature, and that it is of as much importance to the anatomist as are the names of the animals themselves to the zoologist. Popular descriptive zoology concerns rather the teleological characters of animals, while the strictly scientific and systematic arrangements are based upon anatomy, and thus upon morphology. We have noticed one distinction between the terms given above: that morphology and homology both refer to structure, while teleology and analogy both refer to function. Affin- ity is merely a common synonym for homology, and may therefore be omitted. And now the four principal terms pair off on another basis; morphology and teleology are absolute terms, as it were, and may refer to the structure or the function of but a single part or organ; 1 See also his section on Morphology and Nomenclature, in Contributions to the Natural History of the United States, vol. iii. chapter ii. section iv.: also section iii. p. 69. JN THE LIMBS OF MAMMALIA. 3 while homology and analogy are the corresponding relative terms, and necessarily refer to two or more parts or organs which are morphologically or teleologically similar. Morphology is not exactly synonymous with anatomy, for the latter term embraces all the characters of a part, external as well as internal; so that, strictly speaking, parts which are anatomically similar, are likewise physiologically so. But morphology refers rather to the general plan of structure of a part, without altering which, great modifica- tions may be wrought in its outward aspect, with reference to the various functions it is to perform. In like manner teleology is not exactly synonymous with physiology, for the latter term embraces all the functions which can be performed by the part, the less as well as the more essential, otherwise the converse of the previous proposition would be true, and parts which were teleologically similar would be also morphologically similar, which is not the case ; every form or morph has a certain general use or function proper to it, and which may remain under many of its modifications. It is thus of the utmost importance to discriminate between essential structure or morphology, and general structure or anatomy; so also between special function or tele- ology, and general function or physiology. Most objects, whether animal or vegetable, and their various organs, possess more than one attribute ; their anatomy is compound ; their morphology is that simple essential struc- ture which, as a foundation, underlies the more external attributes, one of which is specially developed for the performance of the function from which it has its name; by an easy transfer, the name is finally associated in our mind with the morphology; and then, if this primary attribute be overshadowed by an excessive development of one of the secondary attributes, although the function of the part may be entirely changed, yet, as the essential structure is still recognizable through the external mask, the name is unchanged. Morpho- logically it is the same, though teleologically it may be quite another thing. For examples, and, if I remember rightly, a clearer explanation of this transfer of the name of a part, see the opening paragraphs in Owen’s Report on the “ Homologies of the Vertebrate Skeleton,” to the British Association for the Advancement of Science for the year 1846. With things inanimate the teleology is the use which is made of them. As a familiar illustration, the round Dutch cheeses, used as missiles by one of the parties in a sea-fight years ago, were none the less cheeses, and perhaps excellent ones, because on this occasion put in the place of round shot, thus making the use for which they were intended and named subservient to one rendered possible by a secondary attribute, their extreme hard- ness. As a second example, far too familiar in these days, a shell may strike a victim before it explodes, and thus be teleologically a solid shot, while yet its structure, as adapted to its intended use, remains unaltered. It is needless to multiply illustrations. Whenever anything, without alteration in its essential structure, even though its external form be somewhat modified, fulfils a function other than that for which it was originally intended, then its morphology and its teleology, previously coinciding, are at variance. It thus appears that the teleology may differ from the morphology, as the spirit of the law from the letter thereof, as the expression of a face from the features composing it, as the practical from the technical or theoretical, as the actual or virtual from the nominal or ostensible ; in short, as the thing may differ from its name, the cle facto from the de jure. Morphology is substantive; teleology is adjective. Morphology is the noun ; teleology is its modifier. And as the noun with its modifier may be regarded as a compound substantive, 4 WILDER ON MORPHOLOGY AND TELEOLOGY and may thus be further modified by other adjectives, so in comparative anatomy, nothing is absolutely morphological or teleological, but only with reference to some organ or function more general above, or more special below; it is the possibility of the configuration of an organ being modified without change to a corresponding degree in the internal structure and arrangement of parts. Zoologically speaking, it is the possibility of specific modifica- tions of generic ideas, so that from a limited number of substantives, by adjective additions, are made designations of many more objects; and few at this day dare affirm that this is only a matter of human invention for human convenience. Every genus represents the morphology of the species embraced within it, and they are teleological modifications of the generic idea; now this is the relation between each higher group and the next lower; the further we recede from the species, from the indi- vidual in fact, the more occult and ideal becomes the morphology, till we reach at last the four great groups called types, which, as we shall see hereafter, may even be represented by geometrical figures. How far are these removed from the living sentient individuals which form the other zoological extreme! And yet it does not follow that the existence of the order, the class, or even the type, is any less real and actual than that of the species or of the individual; it is less material, but none the less substantial; in fact, the higher the group, the more real and enduring it is, for it exists in all the members of all the groups embraced within it, though it would exist if it had but a single individual representative. It was said above, that morphology refers only to the general plan of structure; in a certain sense this is so, since it refers to a more hidden interior grade of anatomical charac- ters than those which ordinarily appear upon the surface. The zoologist will see that each of his categories of structure is based upon a different grade of morphology; thus there is a type morphology, the most interior of all, beyond which there are no homologies, but within which are more and more apparent ones, the class homologies, the ordinal homol- ogies, the homologies of the family, genus, and species. I do not mean to say that these groups, as at present characterized by Professor Agassiz, or by any other naturalist, are the true ones, or that they should bear these names, or even that there is just this number of categories of structure; but I do believe that a classification does exist in Nature entirely independent of human thought; that the various kinds of groups in this natural classifica- tion are founded upon categories of structure radically distinct, not at all merging or inter- changing ; and finally, that these categories are simply statements of the various grades of morphology, upon which alone classifications are based. But though this seems to carry us away from direct material function or use, it by no means negatives the idea that each natural group does really represent some use in the grand operations of Nature. Indeed, this would follow as the converse of what was said above, that every higher group represents the morphology of the groups next below, which are themselves teleological modifications of it; conversely, each lower group is, with reference to the next higher, more directly teleological, and increasingly so as we ap- proach the species and the individual. Even the types, ideal and unsubstantial as they seem, represent the four ways in which the powers of sensation and voluntary motion may be embodied and brought into use in the economy of Nature : the idea of an animal is distinct enough in our minds, but so hard to put into words that no really satisfactory definition has ever been proposed. What better evidence of the immaterial character ot the principle which distinguishes the animal from the vegetable and mineral subdivisions of Nature. It seems at first rather strange that the progress in philosophical anatomy may be esti- IN THE LIMBS OF MAMMALIA. 5 mated by the more frequent occurrence of the term homology, especially in the works of Professor Owen, who has done so much toward dispelling the mystery and almost odium attached to the subject, and has cleared up some of its most difficult problems,1 while the philosophy of botany is measured by the term morphology, although it has appar- ently never been perceived that they are corresponding terms, the one relative, the other absolute. But much of the wonder vanishes when it is remembered that the unit of vegetable structure is very simple, consisting, in the Dicotyledones, of the phyton, or leaf with its segment of stem ; and that out of these, by wonderful transmutation and combination, the whole plant is built up. The morphology of a vegetable organ is enunciated when it is shown in what manner it is referable to the typical phyton; and since so few elements compose this, seldom would there arise questions of special and thus of general or serial homology. But with animals the case is otherwise. Having left the simple cell, of which vegetables also are composed, we find at once that their bodies are made up of many organs which cannot possibly be referred to any one unit of structure. The nervous, circulatory, and digestive systems are entirely isolated from each other, and differ, not only physiologi- cally, but microscopically and chemically. Still more complex are the relations existing in the muscular and osseous systems, as presented in the Vertebrates; for here the skele- ton is made up of a series of segments called vertebrae, which are themselves composed of smaller parts or elements having definite relations and bearing distinct names, and by variation in the number, size, and shape of which an almost endless diversity is produced. And now the questions which arise are emphatically those of relation, of homology: what parts represent each other in different animals; what position one element of a vertebra holds with reference to the others in the same; and what elements in two different verte- brae repeat each other ; — questions of special, of general, and of serial homology, respec- tively. It is not, then, so strange that botanists have used the absolute term morphology with reference to the objects of their study, when so few parts or elements compose the morph or type of which the members of any one large group are built up, as that the anatomist, in his anxiety to determine the manifold relations existing in the bodies of animals, should look upon morphology only as the necessary guide to the more difficult questions of homology, which in itself implies more than one morph. Teleological diversities are as of more and less, and the resulting varieties communicate with each other only by continuity; by continuous degrees. Morphological diversities are as of interior and exterior, as of superior and inferior, and the resulting varieties communicate only by contiguity ; by discrete degrees. Here, if rightly appreciated, is contained the essence of two most interesting and not always easily understood generalizations, which are potent weapons of the modern zoolo- gist : the one defensive of his belief in a natural classification, the other offensive against those who assert the existence of a regular, uninterrupted succession of organic forms from lowest to highest, because, forsooth, they cannot see how else creation was effected; thus profanely daring to limit Infinite power by their own wilfully diminished capacity. 1 In his elaborate and admirable Report on the Homolo- gies of the Vertebrate Skeleton, Professor Owen defines three relations of homology: “1st. When a part is said to occu- py a certain position in its vertebra, its general homology is enunciated. 2d. When such a part is said to repeat in its vertebra that which occupies a corresponding position in another vertebra before or behind, its serial homology is given. 3d. When a part is said to have the same relations in two different animals, then its special homology is indicated.” These definitions, as we shall see, do not cover all relations of homology* 6 WILDER ON MORPHOLOGY AND TELEOLOGY These are, 1st, the law of Parallel Relations; and, 2d, the teleological rising above or sinking below their morphological level, of certain groups or species or individuals, whereby they seem to be of a higher or lower grade than the rest of the group of which they are generally the extreme aberrant forms. Illustrations of either of these laws are almost superfluous; of the former many will have occurred to the naturalist who observes similar functions exercised by animals belonging to different groups, or even types: — the aerial bird and butterfly; the heavy, graminivorous cattle among Mammalia, and the phytophagous Scarabei among Coleoptera; the monkey and the parrot; the whole type of Articulates, and the vertebrate class Aves; the type of Mollusks, and the vertebrate class Reptilia; the three classes of Articulates, with the three orders of its highest class, Insecta; and, finally, the striking parallelism between the orders of the two groups of Mammalia, called by Dana Megasthenes and Microsthenes, (American Journal of Science and Art, vol. xxxv. p. 70,) with the less evident one between the A1 trices and the Precoces among birds. Between all these pairs of groups is so evident a similarity as to have suggested the term “Parallel Relation;” but it is to be observed that the rela- tion is one of analogy, not homology; that the differences are morphological, and the resem- blances are comparatively teleological, while between component parts of the same group the resemblances are morphological and the differences teleological. Many insects are 'physiologically more highly organized than the lowest fishes, and the eagle seems a creature vastly superior to the whale; but in each case the groups to which, according to their essential structure, the insect and the eagle belong, are, as groups, on a plane below the fishes and the mammals. The two relations are commonly expressed by representing the groups by parallel vertical lines; there may be such morphological differ- ences between the groups as to clearly indicate which are higher and which lower, but the lines may be overlapped, to show that the lowest in one group is teleologically inferior to the highest of the next group, though, as said above, there would be no doubt concerning the groups taken as wholes. There is not, at least among the higher groups, any such lineal shading off into each other as to afford any support to the idea of a regular, uninterrupted succession of organic forms, whether zoological or genealogical. Nor does the present state of Paleontology fur- nish the disciples of Darwin much assistance in this respect. Position may determine a morphology in addition to that dependent upon structure, and nowhere is this more clear than with the teeth of Mammalia. Professor Owen, in his Odontography, has shown that every classification of these organs based upon their form, and thus upon their special masticatory function, utterly fails in precision on general appli- cation, and that the position of the teeth in the jaws is the only safe guide to their arrange- ment. In this case, it so happens that the teeth were originally named, from their shape and function, incisors, canines, and molars; and this is the order in which they stand in the jaws from before backward. But, while this would answer very well in designating the corresponding teeth in two animals having the same number, and where the variations in form were slight, it utterly failed, even in the hands of Cuvier, accurately to determine such correspondence when applied to the whole range of the mammalian series. Without entering into details, which are given in abundance in the Odontography, it may be said that the teeth collectively are distinguished from all other parts and organs, hard or soft, by a peculiar structure or morphology of their own; but that, to ascertain the limits of the several groups of teeth in the jaws of a single species, or to point out corre- sponding or homologous teeth in animals having a different number, their position in the jaws is the only safe standard, this constituting a minor morphology. IN THE LIMBS OF MAMMALIA. 7 Thus we have teeth morphologically canine, but teleologically incisor,—the outer pair of teeth in the incisive row in the lower jaw of the typical Ruminants, (sheep, cattle, &c.;) and, on the other hand, we have teeth which are morphologically incisor, but teleologically canine,—the only pair of teeth in the intermaxillary bone of the Camelidse, in which aberrant group of Ruminants the lower canines above mentioned assume their proper form and function, as if to compensate for the absence of horns. And this brings us at once to the consideration of the important question, whether every anatomical generalization is not an expression of morphology; whether every grouping of facts which we regard as natural, and which enables us better to comprehend and arrange other facts, is not morphology in the strictest sense of the word. If so, as I believe, then all anatomy is or should be morphology; for all particulars should be studied with refer- ence to generals already ascertained or to be elucidated. And thus morphology comes to be a very simple thing, and not at all a mystery, and will be avoided only by those who confound rational philosophy with unprofitable imaginings of pretty, pleasing fancies. The Creator did not work with barren isolated facts; and only those who strive to rise above these, will ever gain an insight into the way in which He did work, with general laws first established, but only with reference to the particular ultimate facts which were grouped around them. In the human body must exist just such complication of structure and arrangement of parts as best adapt it to be the fit and willing agent of the human mind; and as this is, if not always actually, yet potentially, on a plane superior to that of brutes, so we are pre- pared to find in its fleshy covering a perfection of structure and harmonious arrangement of parts, which, in their totality, far surpass what we observe in inferior animals. In animals, it is true, there may often exist a higher development of one function or class of functions; but this, as we shall see, is always at the expense of the rest, besides mar- ring that beauty of proportion which is really an important element in the human frame. The fish and the whale swim better than man, but the form and structure requisite for this simplest mode of locomotion render every other impossible; even the limbs of the seal, though rather more free, are awkward imitations of anything unless it be paddles. The teeth and stomachs of the strictly carnivorous or herbivorous animals are better adapted for seizing and lacerating or chewing, and for digesting certain kinds of food; but the necessary limitation, as regards other kinds, is an obvious imperfection, taking the creat- ure as a whole. The bird flies through the air with a velocity which man will probably never equal by any mechanical contrivance; but the necessary concentration of weight between the wings makes the anterior and posterior extremities mere bony supports for air and earth, the head taking the place of the hand as an organ of prehension, and becom- ing thereby incapable of speech or expression. The great strength of the ox, and the speed of the horse or of the deer, are gained by such an arrangement of the muscles of the limbs, and modification of their bony frame, as almost to preclude any other motion than simple flexion and extension forward and backward, involving also the loss of prehensile power in the hand. Even the ape, whose structure is so perfectly fitted for climbing, is, so far as regards the location of the organs of prehension and of progression, a man reversed;1 and the power of free rotation in the forearm, with the great strength of the fingers, is specially adapted to its peculiar mode of progression, and not to the elevated uses which the human hand performs. 1 Contributions to the Compai’ative Myology of the Chimpanzee, Boston Journal of Natural History, vol. vii. 8 WILDER ON MORPHOLOGY AND TELEOLOGY In short, looking merely at man’s body, beside being cosmopolitan and typically omniv- orous, although it has a position and mode of locomotion peculiar to itself, and in which it certainly is unrivalled, it is also endowed with the power to assume with grace almost every conceivable attitude, and to employ at will the typical modes of locomotion of other Verte- brates, such as swimming, crawling, leaping, and climbing; and all these the human mind has found means to outstrip in point of speed; even the tlying of the bird, though probably it can never be equalled in rapidity, has been imitated by the aerial mode of locomotion contrived by the same continent of man’s essential superiority. But, leaving the mind wholly out of view, the human body is so constituted as not only to best execute its own peculiar movements, but also to assume more readily than the brutes some which are peculiar to other species. In other words, while endowed with sufficient strength and firmness for all ordinary occasions, it has at the same time such flexibility and independence of action as to be able to apply this strength in many and very diverse ways. For clearer illustration let us contrast two extremes, the arm of man with the fore-leg of the horse. The former can do nearly anything and everything except that of which alone the latter is capable, namely, to support and propel the body on the earth; yet in the two limbs are the same joints, and, except in the hand, the same bones and muscles; but in the quadruped the latter* are short and thick, and so disposed on the front and back of the limb as to pull it with great force in those two directions, and in no other; while in man they are arranged evenly around the bony shafts, thus adding to the symmetry of the limb, as well as increasing its mobility. But the most striking difference is, that, while the movements of each segment of the human arm are, if necessary, entirely independent of those of the other segments, in the horse they are much less so, and flexion or extension at the elbow causes a mechanical movement at the wrist, and vice versa : the independence of the movements of these two joints seems to correspond with the degree of development of the humeral condyles ; these processes, when they exist, are situated just above the insertions of the external and internal lateral ligaments of the elbow, at which two points there is of course no motion ; the condyles lie a little above and therefore change position, though very slightly, during movement at the joint. The extensor muscles of the wrist and fingers arise from the external condyle, the flexors from the internal, both processes being very prominent in man; but it is evident that when the condyles are very small or absent, the origins of the muscles must in like degree reach above or below the centres of motion, and thus, with the parts into which they are inserted, be more or less affected by any movements at the joint. Now in the horse the condyles are almost wholly wanting, the flexors of the hand arising below the centre of motion on the inner side of the humerus, and the extensors above the corresponding point on the outer side; when, therefore, the hand is flexed, the humerus and fore-arm are also flexed at the elbow, and when the hand is extended, these other segments are also extended. Hold the fore-leg of a horse horizontally by the part between the elbow and wrist, and flex the hand; the limb bends at the elbow also. Now if you rest the limb in its natural position upon the earth, the obliquity in the direction of the hoof tends to extend the hand at the wrist, and thus to straighten the limb at the elbow, so that the heavier you press upon the top of the humerus, the firmer the limb becomes. It is evident that this would be a mechanical aid in sustaining the weight of the animal, but I have had no opportunity to look for a similar arrangement in the posterior extremity. On account of this same IN THE LIMBS OF MAMMALIA. 9 structure, however, the fore-leg gives way suddenly and completely when the animal stumble's so as to bear upon the tip of the hoof and so flex the hand at the wrist, for that brings the humerus down with it. In the hind-leg of the frog, which is used for little else than leaping, there is a somewhat similar arrangement, the great extensor of the foot being connected with that of the leg by a strong tendinous band on the inner side of the knee, so that extension of one segment is mechanically connected with that of the other. In the quadrumana and carnivora the condyles are present, though less prominent than in man ; and indeed the degree of their development seems to correspond nearly with that of the clavicle, both of them being concerned in the freedom and mobility of the anterior ex- tremity. The new relations of morphology observed among the muscles of the mammalian limbs are intimately connected with two other generalizations applying to these parts; and these again are subordinate to the great anatomical law of “ antero-posterior symmetry,” as it has been hitherto called; and since little or nothing has been published concerning this in the form it has of late assumed, it may be well to state the law here, chiefly according to the views of Professor Jeffries Wyman, by whom it was suggested to me, and who, almost alone in this country, has devoted time to eliminating, from the indefinite and often extravagant and absurd shape in which it was left by Oken, the real truth of a principle the most potent and elevated of which the vertebrate body, considered by itself, is capable. Yet in my opinion even this is subordinate to a still higher law which pertains as well to the other types of the animal kingdom, and also coincides with a geometrical law so closely as to afford new ground for its belief. In order to appreciate the full force and value of lesser laws, it must first be shown how they depend upon greater ones; and there- fore the latter shall be first considered. A partial statement of this higher law, which for reasons given further on I have called the law of animal polarity, was made by Professor Agassiz, at a meeting of the Boston Soci- ety of Natural History, December 4th, 1861. He characterized the four leading types of the animal kingdom by four terms indicative of the general arrangement of their organs, or their plan of structure : the Radiates by “ radiality,” the Mollusks by “laterality,” the Articulates by “ tergalityf and the Vertebrates by “ cephality” In the Radiates all the parts are disposed about a common centre, encircling which also is the dynamic portion of the nervous system, a ganglion for each diverging segment or spheromere. These spheromeres are morphologically exact repetitions of each other, though their size and shape may be greatly modified, and even one of them may be entirely wanting, so that the animal appears as if divisible into two lateral halves, when really this is due to a teleological modification not at all affecting the real plan of structure, but only foreshadowing, as it were, the characteristic arrangement of the next higher type, just as the molluscan Bryozoa present an appearance of radiation in the disposition of their groups of tentacles. These two instances show the importance of always looking first at the more essential parts of the body, rather than at the outside, which, like other ap- pearances, is often deceitful. The laterality which Professor Agassiz considers characteristic of the Mollusks, must be carefully distinguished from the bilaterality or bilateral symmetry of all animals above Radiates : for the latter terms mean only that the body is composed of two lateral halves which are right and left repetitions of each other; and this is often more conspicuous in 10 WILDER ON MORPHOLOGY AND TELEOLOGY the Vertebrates, and especially in the Articulates with their sharply defined outlines, than in the almost amorphous forms of the Mollusca; but here again we must go beneath the surface, and then we find that in the Mollusks not only are the organs arranged upon the two sides of the body, but the “ weight of organization,” as Professor Agassiz expresses it, is thrown upon the sides, which even in common usage we recognize to have superior value over the front and hind ends, or the upper and lower edges; we examine and figure only the sides, and, except with the Cephalopoda, their natural position is such as to exhibit prominently one of the sides. This distinction between the Ulaterality common to all above Radiates, and the laterality proper to the Mollusks, is well set forth by Mr. N. S. Shaler, in the Proceedings of the Boston Society of Natural History, December 4th, 1861. With the type of Articulata, it is not the right and left sides that we chiefly regard in either a popular or a scientific examination, but the upper and lower regions, which are, as it were, set off against each other. We no more think of placing or viewing an insect on its side than a bivalve on its upper or lower edge, which correspond to the tergal and ventral regions of the Articulate. This seems to confirm the idea that the single ring representing the articulate unit is composed of an equal number of segments above and below a horizontally bisecting plane, and that the legs and wings when they exist are tergal and ventral repetitions of each other. But the internal anatomy is less satisfactory, at least as now understood, and I leaye it to others, more familiar wTith its details, to determine whether this type, whose sharply defined outlines so clearly illustrate the law, has at the same time the most unsatisfactory internal arrangement; it is certain that in our present state of knowledge the laterality of the Mollusks is more apparent than either the tergality of the Articulates or the cephality of the Vertebrates. This latter term, cephality, applied by Professor Agassiz to the highest type, indicates the extreme preponderance in function of one end of the body; which, at first on the same level with the other end, is gradually raised, till it attains the greatest possible elevation in the erect position of man. Professor Dana’s term, “ cephalization,” is indicative of this gradual ennobling of one end of the vertebrate body, and, in man, of the devotion of the arms and hands to its requirements, a physiological return to an allegiance they always owed the head, to which, in fishes, they are actually attached. In this connection it may be added, that, besides the overwhelming evidence adduced by Professor Owen in support of the view now generally received, that the scapular arch is really the modified pair of ribs of the posterior or occipital cranial vertebra©, there are other facts which indicate that in the early stages of even the higher Vertebrates, the shoulders and head are much nearer together than in their adult condition. 1st. The singular course of the inferior laryngeal nerve, whence comes its name of the recurrent, is inexplicable on any other than strictly morphological grounds; for, instead of proceeding by the shortest and most direct route to the larynx from its origin on the pneu- mogastric, it always forms a loop around the subclavian artery on the right side and the arch of the aorta on the left, even in the giraffe, where its length is several times as many feet as it would be inches on the ground of teleology alone. An account of a case of mal- formation, which first drew attention to this peculiarity, was published in the “ Edinburgh Medical and Surgical Journal,” for 1823, and the same Journal for the month of April, 1826, contains an account of a similar case, with an explanation of this apparent waste of nervous matter. Both of these accounts are quoted on page 379 of “Power’s Surgical Anatomy of the Arteries.” 2d. Professor Vrolik, in his work on Monstrosities, “Tabula© ad illustrandam Embryogene- IN THE LIMBS OF MAMMALIA. 11 sin Hominis et Mammalium,” figures, and briefly describes, the skeleton of an anencephalous monster, in which one arm appears attached to the base of the skull, as if by arrest of de- velopment, while the other is in its normal position on the side of the thorax. With a view to ascertain whether, at any period, the shoulders of the mammalian foetus are in actual contact with the cranium, I made careful examination of large numbers of foetal pigs, and in the very smallest, just when the limbs begin to protrude from the sides as little fleshy buds, it is always at some distance from the head; so that, in the Mammalia at least, the fact of actual contact must be regarded as doubtful. 3d. But in most fishes they are firmly attached to the cranium, and in the tadpoles of the bull-frog (Rana pipiens) I have found the scapula closely connected with the poste- rior part of the cranium, either by muscle or ligament, which elongates as development proceeds. Now the three terms, laterality, tergality, and cephality, are more or less complete expres- sions of the arrangement of organs at the two poles of the three axes of a sphere, the lateral, the vertical, and the longitudinal, one of which is specially prominent in each of the higher types, Mollusks, Articulates, and Vertebrates, while the Radiates are represented by the sim- ple sphere itself, with no one axis more prominent than another; since the members of this type are not geometrical figures, but organic, living beings, they must have a structural axis around which their diverging segments or spheromeres are arranged; but this assumes such a variety of directions, being reversed between the Polyps and the Acalephs with most Echinoderms, and becoming horizontal in the Holothurians, as to entirely negative the idea of its having any such morphological significance as the axes of the other three types. These three are the main axes of a sphere, the only ones possible at right angles with each other; and they also correspond with the three dimensions of a solid, — breadth, thickness, and length, — while the sphere may be regarded as having no dimension, yet as capable of all. (See also Professor Agassiz’s “ Contributions to Natural History of the United States,” vol. iii. chap. ii. sect. iv. on Morphology and Nomenclature, p. 76.) This gives us four plans, four morphs on which the animal kingdom is built, and this coincides with the number now be- lieved to exist. A strong corroboration from a different source is contained in the views of Professor Arnold Guyot, expressed in a course of lectures delivered during the winter of 1862, at the Smith- sonian Institution, on the “ Unity of Plan in Animals and Plants.” He presented, as an indication of the existence of no more nor less than four grand divis- ions among animals, the idea that the four types represent the four grand epochs in the life of a single animal; the Radiates are the starting-point, the germ, the simple cell, with life, but this of a low, indeterminate character, and inhabiting the water, the lowest medium; then comes a partial progress in one direction, with the development of the nutritive sys- tems of organs, and this second stage is represented by the Mollusks, with their heavy bodies, devoted to digestion and circulation, and confined to the earth; then comes a partial prog- ress in the opposite direction, with the development of the respiratory and motory apparatus, and this is well represented by the Articulates, chiefly inhabiting the air; and, finally, in the Vertebrates is typified the animal in its perfect state, with a more equal combination of both classes of functions. Again, for the existence of four classes in the Vertebrates the same reason holds good: the Fishes are the starting-point, and, like the Radiates, dwell in the water; then come the Reptiles, with their heavy bodies attached to the earth, and characterized by special promi- nence of the nutritive functions, thus corresponding to the Mollusks; then the Birds, the 12 WILDER ON MORPHOLOGY AND TELEOLOGY aerial Vertebrates, their very bones filled with the medium in which they dwell, and always in active motion; and the cycle-is again completed by the Mammals, which embody a more equal and harmonious combination of all the systems of organs, living, like the Reptiles, on the earth, but elevated above it into the free space of air. Professor Guyot considered the same law to prevail throughout all the lesser groups of Mammalia, and also in the three other types; and it is certainly worthy of remark, that in these latter are recognized only three subdivisions, while in the Vertebrates four are gen- erally acknowledged ; and so in every group containing man would be four lesser groups, but in all others only three, the highest being wanting, and the series thus incomplete. In this connection circle seems as proper as series ; for the most natural exhibition of the relative standing of the four types is by four equidistant points on the circumference of a circle, the Radiates below, the Mollusks above and to the left, the Articulates the same distance above and to the right, and the Vertebrates at the top; the two intermediate groups, the types of partial progress, being at the same distance from the lowest and highest, and thus of equal rank, though opposite nature. Nor can we overlook the fact that there are four regions of the body, pelvis, abdomen, thorax, and head ; and that, as I think Oken has said, Fishes are pelvic animals, Reptiles abdominalBirds thoracic, and Vertebrates cephalic ; and that neither Radiates nor Mollusks nor Articulates possess a distinct anterior segment containing any such overruling portions of the nervous system as does the head of the Vertebrates. There are four senses also, one general, the others special. The sense of touch is universal, and only more or less developed in different regions of the body : it is most exquisitely perceived through the agency of water or moisture, especially in the tongue ; for taste is a peculiar exaltation of the general sensibility, and forms, as it were, a transition therefrom to the smell, one of the three special senses with which, as anatomy clearly shows, it cannot be allied. Of these latter, smell is the lowest, and its exercise depends upon the presence of odoriferous particles of an earthy, solid nature. Hearing is the second special sense, and perceives vibrations in the atmosphere, the next higher medium; while sight, the highest, depends for the exercise of its functions, not upon this, but upon that invisible and imponderable yet material medium which is called ether. Again, sight is directly related to the central nervous system, and properly belongs to the head, below which its organ does not extend. Hearing goes lower down, into the pharynx, with which its organ is connected, anatomically by the Eustachian tube and physiologically when we listen to the speech of another. Smell and its accessory taste preside over the entrance to the alimentary canal, with which they descend through the head and thorax into the abdomen. Finally, in the pelvis is the organ which, as will be hereafter shown, is the posterior or reversed repetition of the tongue, and whose sensitiveness, like taste, is only a peculiar exaltation of the universal sense, the nerves in both cases being the common cranial or spinal nerves, and not special prolongations of the brain into the organ, as with the eye, the ear, and the nose. Professor James D. Dana, in a paper “ On the higher Subdivisions in the Classification of Mammalia,” (American Journal of Science and Arts, vol. xxxv. January, 1863,) proposes a similar quaternary division of that class wTith special reference to the “ cephalization” of the body, which he shows to increase as we ascend in the scale. To those who make classification their study it belongs to decide how much influence these principles exert among the lower groups; but certainly among the higher ones the IN THE LIMBS OF MAMMALIA. coincidences are too striking to be disregarded by the most matter-of-fact philosopher. I subjoin a diagram exhibiting the more evident correspondences in the various departments Geometrical. Morphological. Zoological. Physical. Physiological. Dimension. Prominent Axis. Characteristic polarity. Types. Classes of Element. Region. Sense. Function. State. Radiates. Mollusks. Articulates. Vertebrates. Length. VERT^