ON THE RELATIONS OF MAN TO THE LOWER ANIMALS

By Thomas H. Huxley

 Multis videri poterit, majorem esso differentiam Simiae et Hominis, quam diei et noctis; verum tamen hi, comparatione instituta inter summos Europae Heroes et Hottentottos ad Caput bonae spei degentes, difficillime sibi persuadebunt, has eosdem habere natales; vel si virginem nobilem aulicam, maxime comtam et humanissimam, conferre vellent cum homine sylvestri et sibi relicto, vix augurari possent, hunc et illam ejusdem esse speciei. --'Linnaei Amoenitates Acad. "Anthropomorpha. "'

THE question of questions for mankind--the problem which underliesall others, and is more deeply interesting than any other--is theascertainment of the place which Man occupies in nature and of hisrelations to the universe of things. Whence our race has come; what arethe limits of our power over nature, and of nature's power over us; towhat goal we are tending; are the problems which present themselves anewand with undiminished interest to every man born into the world. Most ofus, shrinking from the difficulties and dangers which beset the seekerafter original answers to these riddles, are contented to ignore themaltogether, or to smother the investigating spirit under the featherbedof respected and respectable tradition. But, in every age, one or tworestless spirits, blessed with that constructive genius, which canonly build on a secure foundation, or cursed with the spirit of merescepticism, are unable to follow in the well-worn and comfortable trackof their forefathers and contemporaries, and unmindful of thorns andstumbling-blocks, strike out into paths of their own. The sceptics endin the infidelity which asserts the problem to be insoluble, or inthe atheism which denies the existence of any orderly progress andgovernance of things: the men of genius propound solutions which growinto systems of Theology or of Philosophy, or veiled in musical languagewhich suggests more than it asserts, take the shape of the Poetry of anepoch. 

Each such answer to the great question, invariably asserted by thefollowers of its propounder, if not by himself, to be complete andfinal, remains in high authority and esteem, it may be for one century, or it may be for twenty: but, as invariably, Time proves each replyto have been a mere approximation to the truth--tolerable chiefly onaccount of the ignorance of those by whom it was accepted, and whollyintolerable when tested by the larger knowledge of their successors. 

In a well-worn metaphor, a parallel is drawn between the life of manand the metamorphosis of the caterpillar into the butterfly; but thecomparison may be more just as well as more novel, if for its formerterm we take the mental progress of the race. History shows that thehuman mind, fed by constant accessions of knowledge, periodically growstoo large for its theoretical coverings, and bursts them asunderto appear in new habiliments, as the feeding and growing grub, atintervals, casts its too narrow skin and assumes another, itself buttemporary. Truly the imago state of Man seems to be terribly distant, but every moult is a step gained, and of such there have been many. 

Since the revival of learning, whereby the Western races of Europe wereenabled to enter upon that progress towards true knowledge, which wascommenced by the philosophers of Greece, but was almost arrested insubsequent long ages of intellectual stagnation, or, at most, gyration, the human larva has been feeding vigorously, and moulting in proportion. A skin of some dimension was cast in the 16th century, and anothertowards the end of the 18th, while, within the last fifty years, theextraordinary growth of every department of physical science has spreadamong us mental food of so nutritious and stimulating a character thata new ecdysis seems imminent. But this is a process not unusuallyaccompanied by many throes and some sickness and debility, or, it maybe, by graver disturbances; so that every good citizen must feel boundto facilitate the process, and even if he have nothing but a scalpel towork withal, to ease the cracking integument to the best of his ability. 

In this duty lies my excuse for the publication of these essays. For itwill be admitted that some knowledge of man's position in the animateworld is an indispensable preliminary to the proper understanding of hisrelations to the universe--and this again resolves itself, in the longrun, into an inquiry into the nature and the closeness of the ties whichconnect him with those singular creatures whose history [1] has beensketched in the preceding pages. 

The importance of such an inquiry is indeed intuitively manifest Broughtface to face with these blurred copies of himself, the least thoughtfulof men is conscious of a certain shock, due perhaps, not so much todisgust at the aspect of what looks like an insulting caricature, asto the awakening of a sudden and profound mistrust of time-honouredtheories and strongly-rooted prejudices regarding his own position innature, and his relations to the under-world of life; while that whichremains a dim suspicion for the unthinking, becomes a vast argument, fraught with the deepest consequences, for all who are acquainted withthe recent progress of the anatomical and physiological sciences. 

I now propose briefly to unfold that argument, and to set forth, ina form intelligible to those who possess no special acquaintancewith anatomical science, the chief facts upon which all conclusionsrespecting the nature and the extent of the bonds which connect man withthe brute world must be based: I shall then indicate the one immediateconclusion which, in my judgment, is justified by those facts, and Ishall finally discuss the bearing of that conclusion upon the hypotheseswhich have been entertained respecting the Origin of Man. 

The facts to which I would first direct the reader's attention, thoughignored by many of the professed instructors of the public mind, areeasy of demonstration and are universally agreed to by men of science;while their significance is so great, that whoso has duly pondered overthem will, I think, find little to startle him in the other revelationsof Biology. I refer to those facts which have been made known by thestudy of Development. 

It is a truth of very wide, if not of universal, application, that everyliving creature commences its existence under a form different from, andsimpler than, that which it eventually attains. 

[Illustration: FIG. 12. --A. Egg of the Dog, with the vitelline membraneburst, so as to give exit to the yelk, the germinal vesicle (a), andits included spot (b). B. C. D. E F. Successive changes of the yelkindicated in the text. After Bischoff. ]

The oak is a more complex thing than the little rudimentary plantcontained in the acorn; the caterpillar is more complex than the egg;the butterfly than the caterpillar; and each of these beings, in passingfrom its rudimentary to its perfect condition, runs through a seriesof changes, the sum of which is called its Development. In the higheranimals these changes are extremely complicated; but, within the lasthalf century, the labours of such men as Von Baer, Rathke, Reichert, Bischof, and Remak, have almost completely unravelled them, so thatthe successive stages of development which are exhibited by a Dog, forexample, are now as well known to the embryologist as are the steps ofthe metamorphosis of the silkworm moth to the school-boy. It will beuseful to consider with attention the nature and the order of thestages of canine development, as an example of the process in the higheranimals generally. 

The Dog, like all animals, save the very lowest (and further inquiriesmay not improbably remove the apparent exception), commences itsexistence as an egg: as a body which is, in every sense, as much an eggas that of a hen, but is devoid of that accumulation of nutritive matterwhich confers upon the bird's egg its exceptional size and domesticutility; and wants the shell, which would not only be useless to ananimal incubated within the body of its parent, but would cut it offfrom access to the source of that nutriment which the young creaturerequires, but which the minute egg of the mammal does not contain withinitself. 

The Dog's egg is, in fact, a little spheroidal bag (Fig. 12), formedof a delicate transparent membrane called the 'vitelline membrane', andabout 1/130 to 1/120th of an inch in diameter. It contains a mass ofviscid nutritive matter--the 'yelk'--within which is inclosed a secondmuch more delicate spheroidal bag, called the 'germinal vesicle' (a). Inthis, lastly, lies a more solid rounded body, termed the 'germinal spot'(b). 

The egg, or 'Ovum, ' is originally formed within a gland, from which, in due season, it becomes detached, and passes into the living chamberfitted for its protection and maintenance during the protracted processof gestation. Here, when subjected to the required conditions, thisminute and apparently insignificant particle of living matter becomesanimated by a new and mysterious activity. The germinal vesicle andspot cease to be discernible (their precise fate being one of the yetunsolved problems of embryology), but the yelk becomes circumferentiallyindented, as if an invisible knife had been drawn round it, and thusappears divided into two hemispheres (Fig. 12, C). 

By the repetition of this process in various planes, these hemispheresbecome subdivided, so that four segments are produced (D); and these, in like manner, divide and subdivide again, until the whole yelk isconverted into a mass of granules, each of which consists of a minutespheroid of yelk-substance, inclosing a central particle, the so-called'nucleus' (F). Nature, by this process, has attained much the sameresult as that at which a human artificer arrives by his operations in abrickfield. She takes the rough plastic material of the yelk and breaksit up into well-shaped tolerably even-sized masses, handy for buildingup into any part of the living edifice. 

[Illustration: FIG. 13. --Earliest rudiment of the Dog. B. Rudimentfurther advanced, showing the foundations of the head, tail, andvertebral column. C. The very young puppy, with attached ends of theyelk-sac and allantois, and invested in the amnion. ]

Next, the mass of organic bricks, or 'cells' as they are technicallycalled, thus formed, acquires an orderly arrangement, becoming convertedinto a hollow spheroid with double walls. Then, upon one side of thisspheroid, appears a thickening, and, by and bye, in the centre of thearea of thickening, a straight shallow groove (Fig. 13, A) marks thecentral line of the edifice which is to be raised, or, in other words, indicates the position of the middle line of the body of the futuredog. The substance bounding the groove on each side next rises up intoa fold, the rudiment of the side wall of that long cavity, which willeventually lodge the spinal marrow and the brain; and in the floor ofthis chamber appears a solid cellular cord, the so-called 'notochord. 'One end of the inclosed cavity dilates to form the head (Fig. 13, B), the other remains narrow, and eventually becomes the tail; the sidewalls of the body are fashioned out of the downward continuation of thewalls of the groove; and from them, by and bye, grow out little budswhich, by degrees, assume the shape of limbs. Watching the fashioningprocess stage by stage, one is forcibly reminded of the modeller inclay. Every part, every organ, is at first, as it were, pinched uprudely, and sketched out in the rough; then shaped more accurately; andonly, at last, receives the touches which stamp its final character. 

Thus, at length, the young puppy assumes such a form as is shown inFig. 13, C. In this condition it has a disproportionately large head, asdissimilar to that of a dog as the bud-like limbs are unlike his legs. 

The remains of the yelk, which have not yet been applied to thenutrition and growth of the young animal, are contained in a sacattached to the rudimentary intestine, and termed the yelk sac, or 'umbilical vesicle. ' Two membranous bags, intended to subserverespectively the protection and nutrition of the young creature, havebeen developed from the skin and from the under and hinder surfaceof the body; the former, the so-called 'amnion, ' is a sac filled withfluid, which invests the whole body of the embryo, and plays the partof a sort of water-bed for it; the other, termed the 'allantois, ' growsout, loaded with blood-vessels, from the ventral region, and eventuallyapplying itself to the walls of the cavity, in which the developingorganism is contained, enables these vessels to become the channelby which the stream of nutriment, required to supply the wants of theoffspring, is furnished to it by the parent. 

The structure which is developed by the interlacement of the vessels ofthe offspring with those of the parent, and by means of which the formeris enabled to receive nourishment and to get rid of effete matters, istermed the 'Placenta. '

It would be tedious, and it is unnecessary for my present purpose, totrace the process of development further; suffice it to say, that, bya long and gradual series of changes, the rudiment here depicted anddescribed becomes a puppy, is born, and then, by still slower and lessperceptible steps, passes into the adult Dog. 

There is not much apparent resemblance between a barndoor Fowl and theDog who protects the farm-yard. Nevertheless the student of developmentfinds, not only that the chick commences its existence as an egg, primarily identical, in all essential respects, with that of the Dog, but that the yelk of this egg undergoes division--that the primitivegroove arises, and that the contiguous parts of the germ are fashioned, by precisely similar methods, into a young chick, which, at one stageof its existence, is so like the nascent Dog, that ordinary inspectionwould hardly distinguish the two. 

The history of the development of any other vertebrate animal, Lizard, Snake, Frog, or Fish, tells the same story. There is always, tobegin with, an egg having the same essential structure as that of theDog:--the yelk of that egg always undergoes division, or 'segmentation'as it is often called: the ultimate products of that segmentationconstitute the building materials for the body of the young animal;and this is built up round a primitive groove, in the floor of whicha notochord is developed. Furthermore, there is a period in which theyoung of all these animals resemble one another, not merely inoutward form, but in all essentials of structure, so closely, that thedifferences between them are inconsiderable, while, in their subsequentcourse, they diverge more and more widely from one another. And it is ageneral law, that, the more closely any animals resemble one anotherin adult structure, the longer and the more intimately do their embryosresemble one another: so that, for example, the embryos of a Snake andof a Lizard remain like one another longer than do those of a Snake andof a Bird; and the embryo of a Dog and of a Cat remain like one anotherfor a far longer period than do those of a Dog and a Bird; or of a Dogand an Opossum; or even than those of a Dog and a Monkey. 

Thus the study of development affords a clear test of closeness ofstructural affinity, and one turns with impatience to inquire whatresults are yielded by the study of the development of Man. Is hesomething apart? Does he originate in a totally different way from Dog, Bird, Frog, and Fish, thus justifying those who assert him to have noplace in nature and no real affinity with the lower world of animallife? Or does he originate in a similar germ, pass through the sameslow and gradually progressive modifications, --depend on the samecontrivances for protection and nutrition, and finally enter the worldby the help of the same mechanism? The reply is not doubtful for amoment, and has not been doubtful any time these thirty years. Withoutquestion, the mode of origin and the early stages of the development ofman are identical with those of the animals immediately below him in thescale:--without a doubt, in these respects, he is far nearer the Apes, than the Apes are to the Dog. 

The Human ovum is about 1/125 of an inch in diameter, and might bedescribed in the same terms as that of the Dog, so that I need onlyrefer to the figure illustrative (14 A) of its structure. It leaves theorgan in which it is formed in a similar fashion and enters the organicchamber prepared for its reception in the same way, the conditions ofits development being in all respects the same. It has not yet beenpossible (and only by some rare chance can it ever be possible) tostudy the human ovum in so early a developmental stage as that of yelkdivision, but there is every reason to conclude that the changesit undergoes are identical with those exhibited by the ova ofother vertebrated animals; for the formative materials of which therudimentary human body is composed, in the earliest conditions in whichit has been observed, are the same as those of other animals. Some ofthese earliest stages are figured below, and, as will be seen, they arestrictly comparable to the very early states of the Dog; the marvellouscorrespondence between the two which is kept up, even for some time, asdevelopment advances, becoming apparent by the simple comparison of thefigures with those on page 249. 

[Illustration: Fig. 14. --A. Human ovum (after Kolliker). A. Germinalvesicle. B. Germinal spot. B. A very early condition of Man, withyelk-sac, allantois, and amnion (original). C. A more advanced stage(after Kolliker), compare Fig. 13, C. ]

Indeed, it is very long before the body of the young human being can bereadily discriminated from that of the young puppy; but, at a tolerablyearly period, the two become distinguishable by the different form oftheir adjuncts, the yelk-sac and the allantois. The former, in the Dog, becomes long and spindle-shaped, while in Man it remains spherical; thelatter, in the Dog, attains an extremely large size, and the vascularprocesses which are developed from it and eventually give rise to theformation of the placenta (taking root, as it were, in the parentalorganism, so as to draw nourishment therefrom, as the root of a treeextracts it from the soil) are arranged in an encircling zone, whilein Man, the allantois remains comparatively small, and its vascularrootlets are eventually restricted to one disk-like spot. Hence, whilethe placenta of the Dog is like a girdle, that of Man has the cake-likeform, indicated by the name of the organ. 

But, exactly in those respects in which the developing Man differsfrom the Dog, he resembles the ape, which, like man, has a spheroidalyelk-sac and a discoidal--sometimes partially lobed--placenta. So thatit is only quite in the later stages of development that the young humanbeing presents marked differences from the young ape, while the latterdeparts as much from the dog in its development, as the man does. 

Startling as the last assertion may appear to be, it is demonstrablytrue, and it alone appears to me sufficient to place beyond all doubtthe structural unity of man with the rest of the animal world, and moreparticularly and closely with the apes. 

Thus, identical in the physical processes by which heoriginates--identical in the early stages of his formation--identical inthe mode of his nutrition before and after birth, with the animals whichlie immediately below him in the scale--Man, if his adult and perfectstructure be compared with theirs, exhibits, as might be expected, amarvellous likeness of organization. He resembles them as they resembleone another--he differs from them as they differ from one another. --And, though these differences and resemblances cannot be weighed andmeasured, their value may be readily estimated; the scale or standardof judgment, touching that value, being afforded and expressed by thesystem of classification of animals now current among zoologists. 

A careful study of the resemblances and differences presented byanimals has, in fact, led naturalists to arrange them into groups, orassemblages, all the members of each group presenting a certain amountof definable resemblance, and the number of points of similarity beingsmaller as the group is larger and 'vice versa'. Thus, all creatureswhich agree only in presenting the few distinctive marks of animalityform the 'Kingdom' ANIMALIA. The numerous animals which agree only inpossessing the special characters of Vertebrates form one 'Sub-Kingdom'of this Kingdom. Then the Sub-kingdom VERTEBRATA is subdivided into thefive 'Classes, ' Fishes, Amphibians, Reptiles, Birds, and Mammals, andthese into smaller groups called 'Orders'; these into 'Families'and 'Genera'; while the last are finally broken up into the smallestassemblages, which are distinguished by the possession of constant, not-sexual, characters. These ultimate groups are Species. 

Every year tends to bring about a greater uniformity of opinionthroughout the zoological world as to the limits and characters of thesegroups, great and small. At present, for example, no one has theleast doubt regarding the characters of the classes Mammalia, Aves, orReptilia; nor does the question arise whether any thoroughly well-knownanimal should be placed in one class or the other. Again, there isa very general agreement respecting the characters and limits ofthe orders of Mammals, and as to the animals which are structurallynecessitated to take a place in one or another order. 

No one doubts, for example, that the Sloth and the Ant-eater, theKangaroo and the Opossum, the Tiger and the Badger, the Tapir andthe Rhinoceros, are respectively members of the same orders. Thesesuccessive pairs of animals may, and some do, differ from one anotherimmensely, in such matters as the proportions and structure of theirlimbs; the number of their dorsal and lumbar vertebrae; the adaptationof their frames to climbing, leaping, or running; the number and formof their teeth; and the characters of their skulls and of the containedbrain. But, with all these differences, they are so closely connected inall the more important and fundamental characters of their organization, and so distinctly separated by these same characters from other animals, that zoologists find it necessary to group them together as membersof one order. And if any new animal were discovered, and were found topresent no greater difference from the Kangaroo and the Opossum, forexample, than these animals do from one another, the zoologist would notonly be logically compelled to rank it in the same order with these, buthe would not think of doing otherwise. 

Bearing this obvious course of zoological reasoning in mind, let usendeavour for a moment to disconnect our thinking selves from the maskof humanity; let us imagine ourselves scientific Saturnians, if youwill, fairly acquainted with such animals as now inhabit the Earth, andemployed in discussing the relations they bear to a new and singular'erect and featherless biped, ' which some enterprising traveller, overcoming the difficulties of space and gravitation, has brought fromthat distant planet for our inspection, well preserved, may be, in acask of rum. We should all, at once, agree upon placing him among themammalian vertebrates; and his lower jaw, his molars, and his brain, would leave no room for doubting the systematic position of the newgenus among those mammals, whose young are nourished during gestation bymeans of a placenta, or what are called the 'placental mammals. '

Further, the most superficial study would at once convince us that, among the orders of placental mammals, neither the Whales, nor thehoofed creatures, nor the Sloths and Ant-eaters, nor the carnivorousCats, Dogs, and Bears, still less the Rodent Rats and Rabbits, or theInsectivorous Moles and Hedgehogs, or the Bats, could claim our 'Homo', as one of themselves. 

There would remain then, but one order for comparison, that of the Apes(using that word in its broadest sense), and the question for discussionwould narrow itself to this--is Man so different from any of these Apesthat he must form an order by himself? Or does he differ less from themthan they differ from one another, and hence must take his place in thesame order with them?

Being happily free from all real, or imaginary, personal interest in theresults of the inquiry thus set afoot, we should proceed to weigh thearguments on one side and on the other, with as much judicial calmnessas if the question related to a new Opossum. We should endeavour toascertain, without seeking either to magnify or diminish them, all thecharacters by which our new Mammal differed from the Apes; and ifwe found that these were of less structural value, than those whichdistinguish certain members of the Ape order from others universallyadmitted to be of the same order, we should undoubtedly place the newlydiscovered tellurian genus with them. 

I now proceed to detail the facts which seem to me to leave us no choicebut to adopt the last mentioned course. 

It is quite certain that the Ape which most nearly approaches man, in the totality of its organization, is either the Chimpanzee or theGorilla; and as it makes no practical difference, for the purposes ofmy present argument, which is selected for comparison, on the one hand, with Man, and on the other hand, with the rest of the Primates, [2]I shall select the latter (so far as its organization is known)--as abrute now so celebrated in prose and verse, that all must have heard ofhim, and have formed some conception of his appearance. I shall take upas many of the most important points of difference between man andthis remarkable creature, as the space at my disposal will allow me todiscuss, and the necessities of the argument demand; and I shall inquireinto the value and magnitude of these differences, when placed side byside with those which separate the Gorilla from other animals of thesame order. 

In the general proportions of the body and limbs there is a remarkabledifference between the Gorilla and Man, which at once strikes the eye. The Gorilla's brain-case is smaller, its trunk larger, its lower limbsshorter, its upper limbs longer in proportion than those of Man. 

I find that the vertebral column of a full-grown Gorilla, in the Museumof the Royal College of Surgeons, measures 27 inches along its anteriorcurvature, from the upper edge of the atlas, or first vertebra of theneck, to the lower extremity of the sacrum; that the arm, without thehand, is 31-1/2 inches long; that the leg, without the foot, is 26-1/2inches long; that the hand is 9-3/4 inches long; the foot 11-1/4 incheslong. 

In other words, taking the length of the spinal column as 100, the armequals 115, the leg 96, the hand 36, and the foot 41. 

In the skeleton of a male Bosjesman, in the same collection, theproportions, by the same measurement, to the spinal column, taken as100, are--the arm 78, the leg 110, the hand 26, and the foot 32. In awoman of the same race the arm is 83, and the leg 120, the hand and footremaining the same. In a European skeleton I find the arm to be 80, theleg 117, the hand 26, the foot 35. 

Thus the leg is not so different as it looks at first sight, in itsproportion to the spine in the Gorilla and in the Man--being veryslightly shorter than the spine in the former, and between 1/10 and 1/5longer than the spine in the latter. The foot is longer and the handmuch longer in the Gorilla; but the great difference is caused by thearms, which are very much longer than the spine in the Gorilla, verymuch shorter than the spine in the Man. 

The question now arises how are the other Apes related to the Gorillain these respects--taking the length of the spine, measured in the sameway, at 100. In an adult Chimpanzee, the arm is only 96, the leg 90, thehand 43, the foot 39--so that the hand and the leg depart more from thehuman proportion and the arm less, while the foot is about the same asin the Gorilla. 

In the Orang, the arms are very much longer than in the Gorilla (122), while the legs are shorter (88); the foot is longer than the hand (52and 48), and both are much longer in proportion to the spine. 

In the other man-like Apes again, the Gibbons, these proportions arestill further altered; the length of the arms being to that of thespinal column as 19 to 11; while the legs are also a third longer thanthe spinal column, so as to be longer than in Man, instead of shorter. The hand is half as long as the spinal column, and the foot, shorterthan the hand, is about 5/11ths of the length of the spinal column. 

Thus 'Hylobates' is as much longer in the arms than the Gorilla, as theGorilla is longer in the arms than Man; while, on the other hand, itis as much longer in the legs than the Man, as the Man is longer in thelegs than the Gorilla, so that it contains within itself the extremestdeviations from the average length of both pairs of limbs (See theillustration on page 196). 

The Mandrill presents a middle condition, the arms and legs being nearlyequal in length, and both being shorter than the spinal column; whilehand and foot have nearly the same proportions to one another and to thespine, as in Man. 

In the Spider monkey ('Ateles') the leg is longer than the spine, andthe arm than the leg; and, finally, in that remarkable Lemurine form, the Indri ('Lichanotus'), the leg is about as long as the spinal column, while the arm is not more than 11/18 of its length; the hand havingrather less and the foot rather more, than one-third the length of thespinal column. 

These examples might be greatly multiplied, but they suffice to showthat, in whatever proportion of its limbs the Gorilla differs fromMan, the other Apes depart still more widely from the Gorilla and that, consequently, such differences of proportion can have no ordinal value. 

We may next consider the differences presented by the trunk, consistingof the vertebral column, or backbone, and the ribs and pelvis, orbony hip-basin, which are connected with it, in Man and in the Gorillarespectively. 

In Man, in consequence partly of the disposition of the articularsurfaces of the vertebrae, and largely of the elastic tension of some ofthe fibrous bands, or ligaments, which connect these vertebrae together, the spinal column, as a whole, has an elegant S-like curvature, beingconvex forwards in the neck, concave in the back, convex in the loins, or lumbar region, and concave again in the sacral region; an arrangementwhich gives much elasticity to the whole backbone, and diminishes thejar communicated to the spine, and through it to the head, by locomotionin the erect position. 

Furthermore, under ordinary circumstances, Man has seven vertebrae inhis neck, which are called 'cervical'; twelve succeed these, bearingribs and forming the upper part of the back, whence they are termed'dorsal'; five lie in the loins, bearing no distinct, or free, ribs, andare called 'lumbar'; five, united together into a great bone, excavatedin front, solidly wedged in between the hip bones, to form the back ofthe pelvis, and known by the name of the 'sacrum', succeed these; andfinally, three or four little more or less movable bones, so small as tobe insignificant, constitute the 'coccyx' or rudimentary tail. 

In the Gorilla, the vertebral column is similarly divided into cervical, dorsal, lumbar, sacral, and coccygeal vertebrae, and the total numberof cervical and dorsal vertebrae, taken together, is the same as inMan; but the development of a pair of ribs to the first lumbar vertebra, which is an exceptional occurrence in Man, is the rule in the Gorilla;and hence, as lumbar are distinguished from dorsal vertebrae only by thepresence or absence of free ribs, the seventeen "dorso-lumbar" vertebraeof the Gorilla are divided into thirteen dorsal and four lumbar, whilein Man they are twelve dorsal and five lumbar. 

[Illustration: FIG. 15. --Front and side views of the bony pelvis of Man, the Gorilla and Gibbon: reduced from drawings made from nature, of thesame absolute length, by Mr. Waterhouse Hawkins. ]

Not only, however, does Man occasionally possess thirteen pair ofribs, but the Gorilla sometimes has fourteen pairs, while an Orang-Utanskeleton in the Museum of the Royal College of Surgeons has twelvedorsal and five lumbar vertebrae, as in Man. Cuvier notes the samenumber in a 'Hylobates'. On the other hand, among the lower Apes, manypossess twelve dorsal and six or seven lumbar vertebrae; theDouroucouli has fourteen dorsal and eight lumbar, and a Lemur ('Stenopstardigradus') has fifteen dorsal and nine lumbar vertebrae. 

The vertebral column of the Gorilla, as a whole, differs from thatof Man in the less marked character of its curves, especially in theslighter convexity of the lumbar region. Nevertheless, the curves arepresent, and are quite obvious in young skeletons of the Gorilla andChimpanzee which have been prepared without removal of the ligaments. Inyoung Orangs similarly preserved, on the other hand, the spinal columnis either straight, or even concave forwards, throughout the lumbarregion. 

Whether we take these characters then, or such minor ones as those whichare derivable from the proportional length of the spines of the cervicalvertebrae, and the like, there is no doubt whatsoever as to the markeddifference between Man and the Gorilla; but there is as little, thatequally marked differences, of the very same order, obtain between theGorilla and the lower Apes. 

The Pelvis, or bony girdle of the hips, of Man is a strikingly humanpart of his organization; the expanded haunch bones affording supportfor his viscera during his habitually erect posture, and giving spacefor the attachment of the great muscles which enable him to assume andto preserve that attitude. In these respects the pelvis of the Gorilladiffers very considerably from his (Fig. 15). But go no lower than theGibbon, and see how vastly more he differs from the Gorilla than thelatter does from Man, even in this structure. Look at the flat, narrowhaunch bones--the long and narrow passage--the coarse, outwardly curved, ischiatic prominences on which the Gibbon habitually rests, and whichare coated by the so-called "callosities, " dense patches of skin, whollyabsent in the Gorilla, in the Chimpanzee, and in the Orang, as in Man!

In the lower Monkeys and in the Lemurs the difference becomes morestriking still, the pelvis acquiring an altogether quadrupedalcharacter. 

But now let us turn to a nobler and more characteristic organ--thatby which the human frame seems to be, and indeed is, so stronglydistinguished from all others, --I mean the skull. The differencesbetween a Gorilla's skull and a Man's are truly immense (Fig. 16). In the former, the face, formed largely by the massive jaw-bones, predominates over the brain case, or cranium proper: in the latter, theproportions of the two are reversed. In the Man, the occipital foramen, through which passes the great nervous cord connecting the brain withthe nerves of the body, is placed just behind the centre of the base ofthe skull, which thus becomes evenly balanced in the erect posture; inthe Gorilla, it lies in the posterior third of that base. In the Man, the surface of the skull is comparatively smooth, and the supraciliaryridges or brow prominences usually project but little--while, in theGorilla, vast crests are developed upon the skull, and the brow ridgesoverhang, the cavernous orbits, like great penthouses. 

Sections of the skulls, however, show that some of the apparent defectsof the Gorilla's cranium arise, in fact, not so much from deficiency ofbrain case as from excessive development of the parts of the face. The cranial cavity is not ill-shaped, and the forehead is not trulyflattened or very retreating, its really well-formed curve being simplydisguised by the mass of bone which is built up against it (Fig. 16). 

But the roofs of the orbits rise more obliquely into the cranial cavity, thus diminishing the space for the lower part of the anterior lobes ofthe brain, and the absolute capacity of the cranium is far less thanthat of Man. So far as I am aware, no human cranium belonging to anadult man has yet been observed with a less cubical capacity than62 cubic inches, the smallest cranium observed in any race of men byMorton, measuring 63 cubic inches; while, on the other hand, the mostcapacious Gorilla skull yet measured has a content of not more than34-1/2 cubic inches. Let us assume, for simplicity's sake, that thelowest Man's skull has twice the capacity of that of the highestGorilla. [4]

No doubt, this is a very striking difference, but it loses much of itsapparent systematic value, when viewed by the light of certain otherequally indubitable facts respecting cranial capacities. 

The first of these is, that the difference in the volume of the cranialcavity of different races of mankind is far greater, absolutely, thanthat between the lowest Man and the highest Ape, while, relatively, it is about the same. For the largest human skull measured by Mortoncontained 114 cubic inches, that is to say, had very nearly double thecapacity of the smallest; while its absolute preponderance, of 52 cubicinches--is far greater than that by which the lowest adult male humancranium surpasses the largest of the Gorillas (62 - 34-1/2 = 27-1/2). Secondly, the adult crania of Gorillas which have as yet been measureddiffer among themselves by nearly one-third, the maximum capacity being34. 5 cubic inches, the minimum 24 cubic inches; and, thirdly, aftermaking all due allowance for difference of size, the cranial capacitiesof some of the lower Apes fall nearly as much, relatively, below thoseof the higher Apes as the latter fall below Man. 

Thus, even in the important matter of cranial capacity, Men differ morewidely from one another than they do from the Apes; while the lowestApes differ as much, in proportion, from the highest, as the latter doesfrom Man. The last proposition is still better illustrated by the studyof the modifications which other parts of the cranium undergo in theSimian series. 

It is the large proportional size of the facial bones and the greatprojection of the jaws which confers upon the Gorilla's skull its smallfacial angle and brutal character. 

[Illustration: FIG. 16. --Sections of the skulls of Man and various Apes, drawn so as to give the cerebral cavity the same length in each case, thereby displaying the varying proportions of the facial bones. The line'b' indicates the plane of the tentorium, which separates the cerebrumfrom the cerebellum; 'd', the axis of the occipital outlet of the skull. The extent of cerebral cavity behind 'c', which is a perpendicularerected on 'b' at the point where the tentorium is attached posteriorly, indicates the degree to which the cerebrum overlaps the cerebellum--thespace occupied by which is roughly indicated by the dark shading. Incomparing these diagrams, it must be recollected, that figures on sosmall a scale as these simply exemplify the statements in the text, theproof of which is to be found in the objects themselves. ]

But if we consider the proportional size of the facial bones to theskull proper only, the little 'Chrysothrix' (Fig. 16) differs verywidely from the Gorilla, and, in the same way, as Man does; while theBaboons ('Cynocephalus', Fig. 16) exaggerate the gross proportions ofthe muzzle of the great Anthropoid, so that its visage looks mild andhuman by comparison with theirs. The difference between the Gorilla andthe Baboon is even greater than it appears at first sight; for the greatfacial mass of the former is largely due to a downward development ofthe jaws; an essentially human character, superadded upon that almostpurely forward, essentially brutal, development of the same parts whichcharacterizes the Baboon, and yet more remarkably distinguishes theLemur. 

Similarly, the occipital foramen of 'Mycetes' (Fig. 16), and stillmore of the Lemurs, is situated completely in the posterior face of theskull, or as much further back than that of the Gorilla, as that of theGorilla is further back than that of Man; while, as if to render patentthe futility of the attempt to base any broad classificatory distinctionon such a character, the same group of Platyrhine, or American monkeys, to which the Mycetes belongs, contains the Chrysothrix, whose occipitalforamen is situated far more forward than in any other ape, and nearlyapproaches the position it holds in Man. 

Again, the Orang's skull is as devoid of excessively developedsupraciliary prominences as a Man's, though some varieties exhibit greatcrests elsewhere (See pp. 231, 232); and in some of the Cebine apes andin the 'Chrysothrix', the cranium is as smooth and rounded as that ofMan himself. 

What is true of these leading characteristics of the skull, holds good, as may be imagined, of all minor features; so that for every constantdifference between the Gorilla's skull and the Man's, a similar constantdifference of the same order (that is to say, consisting in excess ordefect of the same quality) may be found between the Gorilla's skulland that of some other ape. So that, for the skull, no less than for theskeleton in general, the proposition holds good, that the differencesbetween Man and the Gorilla are of smaller value than those between theGorilla and some other Apes. 

In connection with the skull, I may speak of the teeth--organs whichhave a peculiar classificatory value, and whose resemblances anddifferences of number, form, and succession, taken as a whole, areusually regarded as more trustworthy indicators of affinity than anyothers. 

[Illustration: FIG. 17. --Lateral views, of the same length, of the upperjaws of various Primates. 'i', incisors; 'c', canines' 'pm', premolars;'m', molars. A line is drawn through the first molar of Man, 'Gorilla', 'Cynocephalus', and 'Cebus', and the grinding surface of the secondmolar is shown in each, its anterior and internal angle being just abovethe 'm' of 'm2'. ]

Man is provided with two sets of teeth--milk teeth and permanent teeth. The former consist of four incisors, or cutting teeth; two canines, oreyeteeth; and four molars, or grinders, in each jaw--making twenty inall. The latter (Fig. 17) comprise four incisors, two canines, foursmall grinders, called premolars or false molars, and six largegrinders, or true molars, in each jaw--making thirty-two in all. Theinternal incisors are larger than the external pair, in the upper jaw, smaller than the external pair, in the lower jaw. The crowns of theupper molars exhibit four cusps, or blunt-pointed elevations, and aridge crosses the crown obliquely, from the inner, anterior cusp to theouter, posterior cusp (Fig. 17 m2). The anterior lower molars have fivecusps, three external and two internal. The premolars have two cusps, one internal and one external, of which the outer is the higher. 

In all these respects the dentition of the Gorilla may be described inthe same terms as that of Man; but in other matters it exhibits many andimportant differences (Fig. 17). 

Thus the teeth of man constitute a regular and even series--without anybreak and without any marked projection of one tooth above the level ofthe rest; a peculiarity which, as Cuvier long ago showed, is shared byno other mammal save one--as different a creature from man as can wellbe imagined--namely, the long extinct 'Anoplotherium'. The teeth ofthe Gorilla, on the contrary, exhibit a break, or interval, termed the'diastema', in both jaws: in front of the eye-tooth, or between it andthe outer incisor, in the upper jaw; behind the eyetooth, or betweenit and the front false molar, in the lower jaw. Into this break in theseries, in each jaw, fits the canine of the opposite jaw; the size ofthe eye-tooth in the Gorilla being so great that it projects, like atusk, far beyond the general level of the other teeth. The roots of thefalse molar teeth of the Gorilla, again, are more complex than in Man, and the proportional size of the molars is different. The Gorilla hasthe crown of the hindmost grinder of the lower jaw more complex, andthe order of eruption of the permanent teeth is different; the permanentcanines making their appearance before the second and third molars inMan, and after them in the Gorilla. 

Thus, while the teeth of the Gorilla closely resemble those of Man innumber, kind, and in the general pattern of their crowns, they exhibitmarked differences from those of Man in secondary respects, such asrelative size, number of fangs, and order of appearance. 

But, if the teeth of the Gorilla be compared with those of an Ape, nofurther removed from it than a 'Cynocephalus', or Baboon, it will befound that differences and resemblances of the same order are easilyobservable; but that many of the points in which the Gorilla resemblesMan are those in which it differs from the Baboon; while variousrespects in which it differs from Man are exaggerated in the'Cynocephalus'. The number and the nature of the teeth remain the samein the Baboon as in the Gorilla and in Man. But the pattern of theBaboon's upper molars is quite different from that described above (Fig. 17), the canines are proportionally longer and more knife-like; theanterior premolar in the lower jaw is specially modified; the posteriormolar of the lower jaw is still larger and more complex than in theGorilla. 

Passing from the old-world Apes to those of the new world, we meet witha change of much greater importance than any of these. In such a genusas 'Cebus', for example (Fig. 17), it will be found that while insome secondary points, such as the projection of the canines and thediastema, the resemblance to the great ape is preserved; in other andmost important respects, the dentition is extremely different. Insteadof 20 teeth in the milk set, there are 24: instead of 32 teeth in thepermanent set, there are 36, the false molars being increased from eightto twelve. And in form, the crowns of the molars are very unlike thoseof the Gorilla, and differ far more widely from the human pattern. 

The Marmosets, on the other hand, exhibit the same number of teeth asMan and the Gorilla; but, notwithstanding this, their dentition is verydifferent, for they have four more false molars, like the other Americanmonkeys--but as they have four fewer true molars, the total remains thesame. And passing from the American apes to the Lemurs, the dentitionbecomes still more completely and essentially different from that ofthe Gorilla. The incisors begin to vary both in number and in form. Themolars acquire, more and more, a many-pointed, insectivorous character, and in one Genus, the Aye-Aye ('Cheiromys'), the canines disappear, andthe teeth completely simulate those of a Rodent (Fig. 17). 

Hence it is obvious that, greatly as the dentition of the highest Apediffers from that of Man, it differs far more widely from that of thelower and lowest Apes. 

Whatever part of the animal fabric--whatever series of muscles, whateverviscera might be selected for comparison--the result would be thesame--the lower Apes and the Gorilla would differ more than the Gorillaand the Man. I cannot attempt in this place to follow out all thesecomparisons in detail, and indeed it is unnecessary I should do so. Butcertain real, or supposed, structural distinctions between man and theapes remain, upon which so much stress has been laid, that they requirecareful consideration, in order that the true value may be assigned tothose which are real, and the emptiness of those which are fictitiousmay be exposed. I refer to the characters of the hand, the foot, and thebrain. 

Man has been defined as the only animal possessed of two handsterminating his fore limbs, and of two feet ending his hind limbs, whileit has been said that all the apes possess four hands; and he has beenaffirmed to differ fundamentally from all the apes in the characters ofhis brain, which alone, it has been strangely asserted and re-asserted, exhibits the structures known to anatomists as the posterior lobe, theposterior cornu of the lateral ventricle, and the hippocampus minor. 

That the former proposition should have gained general acceptance is notsurprising--indeed, at first sight, appearances are much in its favour:but, as for the second, one can only admire the surpassing courageof its enunciator, seeing that it is an innovation which is not onlyopposed to generally and justly accepted doctrines, but which isdirectly negatived by the testimony of all original inquirers, who havespecially investigated the matter: and that it neither has been, nor canbe, supported by a single anatomical preparation. It would, in fact, be unworthy of serious refutation, except for the general and naturalbelief that deliberate and reiterated assertions must have somefoundation. 

Before we can discuss the first point with advantage we must considerwith some attention, and compare together, the structure of the humanhand and that of the human foot, so that we may have distinct and clearideas of what constitutes a hand and what a foot. 

The external form of the human hand is familiar enough to every one. Itconsists of a stout wrist followed by a broad palm, formed of flesh, andtendons, and skin, binding together four bones, and dividing into fourlong and flexible digits, or fingers, each of which bears on the back ofits last joint a broad and flattened nail. The longest cleft between anytwo digits is rather less than half as long as the hand. From the outerside of the base of the palm a stout digit goes off, having only twojoints instead of three; so short, that it only reaches to a littlebeyond the middle of the first joint of the finger next it; and furtherremarkable by its great mobility, in consequence of which it can bedirected outwards, almost at a right angle to the rest. This digit iscalled the 'pollex, ' or thumb; and, like the others, it bears aflat nail upon the back of its terminal joint. In consequence of theproportions and mobility of the thumb, it is what is termed "opposable";in other words, its extremity can, with the greatest ease, be broughtinto contact with the extremities of any of the fingers; a property uponwhich the possibility of our carrying into effect the conceptions of themind so largely depends. 

The external form of the foot differs widely from that of the hand; andyet, when closely compared, the two present some singular resemblances. Thus the ankle corresponds in a manner with the wrist; the sole with thepalm; the toes with the fingers; the great toe with the thumb. But thetoes, or digits of the foot, are far shorter in proportion than thedigits of the hand, and are less moveable, the want of mobility beingmost striking in the great toe--which, again, is very much largerin proportion to the other toes than the thumb to the fingers. Inconsidering this point, however, it must not be forgotten that thecivilized great toe, confined and cramped from childhood upwards, isseen to a great disadvantage, and that in uncivilized and barefootedpeople it retains a great amount of mobility, and even some sort ofopposability. The Chinese boatmen are said to be able to pull an oar;the artisans of Bengal to weave, and the Carajas to steal fishhooks, byits help; though, after all, it must be recollected that the structureof its joints and the arrangement of its bones, necessarily render itsprehensile action far less perfect than that of the thumb. 

But to gain a precise conception of the resemblances and differences ofthe hand and foot, and of the distinctive characters of each, we mustlook below the skin, and compare the bony framework and its motorapparatus in each (Fig. 18). 

[Illustration: FIG. 18--The skeleton of the Hand and Foot of Man reducedfrom Dr. Carter's drawings in Gray's 'Anatomy. ' The hand is drawn toa larger scale than the foot. The line 'a a' in the hand indicates theboundary between the carpus and the metacarpus; 'b b' that between thelatter and the proximal phalanges; 'c c' marks the ends of the distalphalanges. The line "a' a'" in the foot indicates the boundary betweenthe tarsus and metatarsus; "b' b'" marks that between the metatarsusand the proximal phalanges; and "c' c'" bounds the ends of the distalphalanges; 'ca', the calcaneum; 'as', the astragalus; 'sc', the scaphoidbone in the tarsus. ]

The skeleton of the hand exhibits, in the region which we term thewrist, and which is technically called the 'carpus'--two rows of closelyfitted polygonal bones, four in each row, which are tolerably equal insize. The bones of the first row with the bones of the forearm, form thewrist joint, and are arranged side by side, no one greatly exceeding oroverlapping the rest. 

The four bones of the second row of the carpus bear the four long boneswhich support the palm of the hand. The fifth bone of the same characteris articulated in a much more free and moveable manner than the others, with its carpal bone, and forms the base of the thumb. These are called'metacarpal' bones, and they carry the 'phalanges', or bones of thedigits, of which there are two in the thumb, and three in each of thefingers. 

The skeleton of the foot is very like that of the hand in some respects. Thus there are three phalanges in each of the lesser toes, and onlytwo in the great toe, which answers to the thumb. There is a long bone, termed 'metatarsal', answering to the metacarpal, for each digit; andthe 'tarsus', which corresponds with the carpus, presents four shortpolygonal bones in a row, which correspond very closely with the fourcarpal bones of the second row of the hand. In other respects the footdiffers very widely from the hand. Thus the great toe is the longestdigit but one; and its metatarsal is far less moveably articulated withthe tarsus, than the metacarpal of the thumb with the carpus. But a farmore important distinction lies in the fact that, instead of fourmore tarsal bones there are only three; and, that these three are notarranged side by side, or in one row. One of them, the 'os calcis' orheel bone ('ca'), lies externally, and sends back the large projectingheel; another, the 'astragalus' ('as'), rests on this by one face, andby another, forms, with the bones of the leg, the ankle joint; while athird face, directed forwards, is separated from the three inner tarsalbones of the row next the metatarsus by a bone called the 'scaphoid'('sc'). 

Thus there is a fundamental difference in the structure of the foot andthe hand, observable when the carpus and the tarsus are contrasted; andthere are differences of degree noticeable when the proportions andthe mobility of the metacarpals and metatarsals, with their respectivedigits, are compared together. 

The same two classes of differences become obvious when the muscles ofthe hand are compared with those of the foot. 

Three principal sets of muscles, called "flexors, " bend the fingers andthumb, as in clenching the fist, and three sets--the extensors--extendthem, as in straightening the fingers. These muscles are all "longmuscles"; that is to say, the fleshy part of each, lying in and beingfixed to the bones of the arm, is, at the other end, continued intotendons, or rounded cords, which pass into the hand, and are ultimatelyfixed to the bones which are to be moved. Thus, when the fingers arebent, the fleshy parts of the flexors of the fingers, placed in the arm, contract, in virtue of their peculiar endowment as muscles; and pullingthe tendinous cords, connected with their ends, cause them to pull downthe bones of the fingers towards the palm. 

Not only are the principal flexors of the fingers and of the thumb longmuscles, but they remain quite distinct from one another through theirwhole length. 

In the foot, there are also three principal flexor muscles of the digitsor toes, and three principal extensors; but one extensor and one flexorare short muscles; that is to say, their fleshy parts are not situatedin the leg (which corresponds with the arm), but in the back and in thesole of the foot--regions which correspond with the back and the palm ofthe hand. 

Again, the tendons of the long flexor of the toes, and of the longflexor of the great toe, when they reach the sole of the foot, do notremain distinct from one another, as the flexors in the palm of thehand do, but they become united and commingled in a very curiousmanner--while their united tendons receive an accessory muscle connectedwith the heel-bone. 

But perhaps the most absolutely distinctive character about the musclesof the foot is the existence of what is termed the 'peronaeus longus', a long muscle fixed to the outer bone of the leg, and sending its tendonto the outer ankle, behind and below which it passes, and then crossesthe foot obliquely to be attached to the base of the great toe. Nomuscle in the hand exactly corresponds with this, which is eminently afoot muscle. 

To resume--the foot of man is distinguished from his hand by thefollowing absolute anatomical differences:--

1. By the arrangement of the tarsal bones. 

2. By having a short flexor and a short extensor muscle of the digits. 

3. By possessing the muscle termed 'peronaeus longus'. 

And if we desire to ascertain whether the terminal division of a limb, in other Primates, is to be called a foot or a hand, it is by thepresence or absence of these characters that we must be guided, and notby the mere proportions and greater or lesser mobility of the great toe, which may vary indefinitely without any fundamental alteration in thestructure of the foot. 

Keeping these considerations in mind, let us now turn to the limbsof the Gorilla. The terminal division of the fore limb presents nodifficulty--bone for bone and muscle for muscle, are found to bearranged essentially as in man, or with such minor differences as arefound as varieties in man. The Gorilla's hand is clumsier, heavier, andhas a thumb somewhat shorter in proportion than that of man; but no onehas ever doubted its being a true hand. 

[Illustration: FIG 19. --Foot of Man, Gorilla, and Orang-Utan of the sameabsolute length, to show the differences in proportion of each. Letters as in Fig. 18. Reduced from original drawings by Mr. WaterhouseHawkins. ]

At first sight, the termination of the hind limb of the Gorilla looksvery hand-like, and as it is still more so in many of the lower apes, it is not wonderful that the appellation "Quadrumana, " or four-handedcreatures, adopted from the older anatomists [5] by Blumenbach, andunfortunately rendered current by Cuvier, should have gained suchwide acceptance as a name for the Simian group. But the most cursoryanatomical investigation at once proves that the resemblance of theso-called "hind hand" to a true hand, is only skin deep, and that, in all essential respects, the hind limb of the Gorilla is as trulyterminated by a foot as that of man. The tarsal bones, in all importantcircumstances of number, disposition, and form, resemble those ofman (Fig. 19). The metatarsals and digits, on the other hand, areproportionally longer and more slender, while the great toe is not onlyproportionally shorter and weaker, but its metatarsal bone is united bya more moveable joint with the tarsus. At the same time, the foot is setmore obliquely upon the leg than in man. 

As this passage was published in 1699, M. I. G. St. Hilaire is clearlyin error in ascribing the invention of the term "quadrumanous" toBuffon, though "himanous" may belong to him. Tyson uses "Quadrumanus"in several places, as at p. 91.... "Our 'Pygmie' is no Man, nor yet the'common Ape', but a sort of 'Animal' between both; and though a 'Biped', yet of the 'Quadrumanus'-kind: though some 'Men' too have been observedto use their 'Feet' like 'Hands', as I have seen several. "

As to the muscles, there is a short flexor, a short extensor, and a'peronaeus longus', while the tendons of the long flexors of the greattoe and of the other toes are united together and with an accessoryfleshy bundle. 

The hind limb of the Gorilla, therefore, ends in a true foot, with avery moveable great toe. It is a prehensile foot, indeed, but is in nosense a hand: it is a foot which differs from that of man not inany fundamental character, but in mere proportions, in the degree ofmobility, and in the secondary arrangement of its parts. 

It must not be supposed, however, because I speak of these differencesas not fundamental, that I wish to underrate their value. They areimportant enough in their way, the structure of the foot being in strictcorrelation with that of the rest of the organism in each case. Nor canit be doubted that the greater division of physiological labour in Man, so that the function of support is thrown wholly on the leg and foot, isan advance in organization of very great moment to him; but, after all, regarded anatomically, the resemblances between the foot of Man andthe foot of the Gorilla are far more striking and important than thedifferences. 

I have dwelt upon this point at length, because it is one regardingwhich much delusion prevails; but I might have passed it over withoutdetriment to my argument, which only requires me to show that, be thedifferences between the hand and foot of Man and those of the Gorillawhat they may--the differences between those of the Gorilla, and thoseof the lower Apes are much greater. 

It is not necessary to descend lower in the scale than the Orang forconclusive evidence on this head. 

The thumb of the Orang differs more from that of the Gorilla thanthe thumb of the Gorilla differs from that of Man, not only by itsshortness, but by the absence of any special long flexor muscle. Thecarpus of the Orang, like that of most lower apes, contains nine bones, while in the Gorilla, as in Man and the Chimpanzee, there are onlyeight. 

The Orang's foot (Fig. 19) is still more aberrant; its very longtoes and short tarsus, short great toe, short and raised heel, greatobliquity of articulation in the leg, and absence of a long flexortendon to the great toe, separating it far more widely from the foot ofthe Gorilla than the latter is separated from that of Man. 

But, in some of the lower apes, the hand and foot diverge still morefrom those of the Gorilla, than they do in the Orang. The thumb ceasesto be opposable in the American monkeys; is reduced to a mere rudimentcovered by the skin in the Spider Monkey; and is directed forwards andarmed with a curved claw like the other digits, in the Marmosets--sothat, in all these cases, there can be no doubt but that the hand ismore different from that of the Gorilla than the Gorilla's hand is fromMan's. 

And as to the foot, the great toe of the Marmoset is still moreinsignificant in proportion than that of the Orang--while in the Lemursit is very large, and as completely thumb-like and opposable as inthe Gorilla--but in these animals the second toe is often irregularlymodified, and in some species the two principal bones of the tarsus, the 'astragalus' and the 'os calcis', are so immensely elongated as torender the foot, so far, totally unlike that of any other mammal. 

So with regard to the muscles. The short flexor of the toes of theGorilla differs from that of Man by the circumstance that one slip ofthe muscle is attached, not to the heel bone, but to the tendons of thelong flexors. The lower Apes depart from the Gorilla by an exaggerationof the same character, two, three, or more, slips becoming fixed to thelong flexor tendons--or by a multiplication of the slips. --Again, theGorilla differs slightly from Man in the mode of interlacing of the longflexor tendons: and the lower apes differ from the Gorilla in exhibitingyet other, sometimes very complex, arrangements of the same parts, andoccasionally in the absence of the accessory fleshy bundle. 

Throughout all these modifications it must be recollected that thefoot loses no one of its essential characters. Every Monkey and Lemurexhibits the characteristic arrangement of tarsal bones, possesses ashort flexor and short extensor muscle, and a 'peronaeus longus'. Variedas the proportions and appearance of the organ may be, the terminaldivision of the hind limb remains, in plan and principle ofconstruction, a foot, and never, in those respects, can be confoundedwith a hand. 

Hardly any part of the bodily frame, then, could be found bettercalculated to illustrate the truth that the structural differencesbetween Man and the highest Ape are of less value than those between thehighest and the lower Apes, than the hand or the foot, and yet, perhaps, there is one organ the study of which enforces the same conclusion in astill more striking manner--and that is the Brain. 

But before entering upon the precise question of the amount ofdifference between the Ape's brain and that of Man, it is necessary thatwe should clearly understand what constitutes a great, and what a smalldifference in cerebral structure; and we shall be best enabled todo this by a brief study of the chief modifications which the brainexhibits in the series of vertebrate animals. 

The brain of a fish is very small, compared with the spinal cord intowhich it is continued, and with the nerves which come off from it: ofthe segments of which it is composed--the olfactory lobes, the cerebralhemisphere, and the succeeding divisions--no one predominates so muchover the rest as to obscure or cover them; and the so-called optic lobesare, frequently, the largest masses of all. In Reptiles, the mass ofthe brain, relatively to the spinal cord, increases and the cerebralhemispheres begin to predominate over the other parts; while in Birdsthis predominance is still more marked. The brain of the lowest Mammals, such as the duck-billed Platypus and the Opossums and Kangaroos, exhibits a still more definite advance in the same direction. Thecerebral hemispheres have now so much increased in size as, more orless, to hide the representatives of the optic lobes, which remaincomparatively small, so that the brain of a Marsupial is extremelydifferent from that of a Bird, Reptile, or Fish. A step higher in thescale, among the placental Mammals, the structure of the brain acquiresa vast modification--not that it appears much altered externally, ina Rat or in a Rabbit, from what it is in a Marsupial--nor that theproportions of its parts are much changed, but an apparently newstructure is found between the cerebral hemispheres, connecting themtogether, as what is called the 'great commissure' or 'corpus callosum. 'The subject requires careful re-investigation, but if the currentlyreceived statements are correct, the appearance of the 'corpus callosum'in the placental mammals is the greatest and most sudden modificationexhibited by the brain in the whole series of vertebrated animals--it isthe greatest leap anywhere made by Nature in her brain work. For thetwo halves of the brain being once thus knit together, the progress ofcerebral complexity is traceable through a complete series of steps fromthe lowest Rodent, or Insectivore, to Man; and that complexity consists, chiefly, in the disproportionate development of the cerebral hemispheresand of the cerebellum, but especially of the former, in respect to theother parts of the brain. 

In the lower placental mammals, the cerebral hemispheres leave theproper upper and posterior face of the cerebellum completely visible, when the brain is viewed from above; but, in the higher forms, thehinder part of each hemisphere, separated only by the tentorium (p. 281) from the anterior face of the cerebellum, inclines backwards anddownwards, and grows out, as the so-called "posterior lobe, " so as atlength to overlap and hide the cerebellum. In all Mammals, each cerebralhemisphere contains a cavity which is termed the 'ventricle, ' and asthis ventricle is prolonged, on the one hand, forwards, and on the otherdownwards, into the substance of the hemisphere, it is said to have twohorns or 'cornua, an 'anterior cornu, ' and a 'descending cornu. ' Whenthe posterior lobe is well developed, a third prolongation of theventricular cavity extends into it, and is called the "posterior cornu. "

In the lower and smaller forms of placental Mammals the surface of thecerebral hemispheres is either smooth or evenly rounded, or exhibits avery few grooves, which are technically termed 'sulci, 'separating ridgesor 'convolutions' of the substance of the brain; and the smaller speciesof all orders tend to a similar smoothness of brain. But, in the higherorders, and especially the larger members of these orders, the grooves, or sulci, become extremely numerous, and the intermediate convolutionsproportionately more complicated in their meanderings, until, in theElephant, the Porpoise, the higher Apes, and Man, the cerebral surfaceappears a perfect labyrinth of tortuous foldings. 

Where a posterior lobe exists and presents its customary cavity--theposterior cornu--it commonly happens that a particular sulcus appearsupon the inner and under surface of the lobe, parallel with and beneaththe floor of the cornu--which is, as it were, arched over the roof ofthe sulcus. It is as if the groove had been formed by indenting thefloor of the posterior horn from without with a blunt instrument, sothat the floor should rise as a convex eminence. Now this eminence iswhat has been termed the 'Hippocampus minor;' the 'Hippocampus major'being a larger eminence in the floor of the descending cornu. What maybe the functional importance of either of these structures we know not. 

As if to demonstrate, by a striking example, the impossibility oferecting any cerebral barrier between man and the apes, Nature hasprovided us, in the latter animals, with an almost complete series ofgradations from brains little higher than that of a Rodent, to brainslittle lower than that of Man. And it is a remarkable circumstance thatthough, so far as our present knowledge extends, there 'is' one truestructural break in the series of forms of Simian brains, this hiatusdoes not lie between Man and the man-like apes, but between the lowerand the lowest Simians; or, in other words, between the old and newworld apes and monkeys, and the Lemurs. Every Lemur which has yet beenexamined, in fact, has its cerebellum partially visible from above, andits posterior lobe, with the contained posterior cornu and hippocampusminor, more or less rudimentary. Every Marmoset, American monkey, old-world monkey, Baboon, or Man-like ape, on the contrary, has itscerebellum entirely hidden, posteriorly, by the cerebral lobes, andpossesses a large posterior cornu, with a well-developed hippocampusminor. 

[Illustration: FIG. 20. --Drawings of the internal casts of a Man's andof a Chimpanzee's skull, of the same absolute length, and placed incorresponding positions. 'A'. Cerebrum; 'B'. Cerebellum. The formerdrawing is taken from a cast in the Museum of the Royal College ofSurgeons, the latter from the photograph of the cast of a Chimpanzee'sskull, which illustrates the paper by Mr. Marshall 'On the Brain of theChimpanzee' in the 'Natural History Review' for July, 1861. The sharperdefinition of the lower edge of the cast of the cerebral chamber in theChimpanzee arises from the circumstance that the tentorium remained inthat skull and not in the Man's. The cast more accurately represents thebrain in Chimpanzee than in the Man; and the great backward projectionof the posterior lobes of the cerebrum of the former, beyond thecerebellum, is conspicuous. ]

In many of these creatures, such as the Saimiri ('Chrysothrix'), thecerebral lobes overlap and extend much further behind the cerebellum, inproportion, than they do in man (Fig. 16)--and it is quite certain that, in all, the cerebellum is completely covered behind, by well-developedposterior lobes. The fact can be verified by every one who possesses theskull of any old or new world monkey. For, inasmuch as the brain in allmammals completely fills the cranial cavity, it is obvious that a castof the interior of the skull will reproduce the general form of thebrain, at any rate with such minute and, for the present purpose, utterly unimportant differences as may result from the absence of theenveloping membranes of the brain in the dry skull. But if such a castbe made in plaster, and compared with a similar cast of the interior ofa human skull, it will be obvious that the cast of the cerebral chamber, representing the cerebrum of the ape, as completely covers overand overlaps the cast of the cerebellar chamber, representing thecerebellum, as it does in the man (Fig. 20). A careless observer, forgetting that a soft structure like the brain loses its propershape the moment it is taken out of the skull, may indeed mistake theuncovered condition of the cerebellum of an extracted and distortedbrain for the natural relations of the parts; but his error must becomepatent even to himself if he try to replace the brain within the cranialchamber. To suppose that the cerebellum of an ape is naturally uncoveredbehind is a miscomprehension comparable only to that of one who shouldimagine that a man's lungs always occupy but a small portion of thethoracic cavity--because they do so when the chest is opened, and theirelasticity is no longer neutralized by the pressure of the air. 

And the error is the less excusable, as it must become apparent toevery one who examines a section of the skull of any ape above a Lemur, without taking the trouble to make a cast of it. For there is avery marked groove in every such skull, as in the human skull--whichindicates the line of attachment of what is termed the 'tentorium'--asort of parchment-like shelf, or partition, which, in the recent state, is interposed between the cerebrum and cerebellum, and prevents theformer from pressing upon the latter. (See Fig. 16. )

This groove, therefore, indicates the line of separation between thatpart of the cranial cavity which contains the cerebrum, and that whichcontains the cerebellum; and as the brain exactly fills the cavity ofthe skull, it is obvious that the relations of these two parts of thecranial cavity at once informs us of the relations of their contents. Now in man, in all the old-world, and in all the new-world Simiae, with one exception, when the face is directed forwards, this line ofattachment of the tentorium, or impression for the lateral sinus, as itis technically called, is nearly horizontal, and the cerebral chamberinvariably overlaps or projects behind the cerebellar chamber. In theHowler Monkey or 'Mycetes' (see Fig. 16), the line passes obliquelyupwards and backwards, and the cerebral overlap is almost nil; while inthe Lemurs, as in the lower mammals, the line is much more inclined inthe same direction, and the cerebellar chamber projects considerablybeyond the cerebral. 

When the gravest errors respecting points so easily settled asthis question respecting the posterior lobes can be authoritativelypropounded, it is no wonder that matters of observation, of no verycomplex character, but still requiring a certain amount of care, shouldhave fared worse. Any one who cannot see the posterior lobe in an ape'sbrain is not likely to give a very valuable opinion respecting theposterior cornu or the hippocampus minor. If a man cannot see a church, it is preposterous to take his opinion about its altar-piece or paintedwindow--so that I do not feel bound to enter upon any discussion ofthese points, but content myself with assuring the reader that theposterior cornu and the hippocampus minor, have now been seen--usually, at least as well developed as in man, and often better--not only in theChimpanzee, the Orang, and the Gibbon, but in all the genera of the oldworld baboons and monkeys, and in most of the new world forms, includingthe Marmosets. 

[Illustration: FIG. 21. --Drawings of the cerebral hemispheres of a Manand of a Chimpanzee of the same length, in order to show the relativeproportions of the parts: the former taken from a specimen, which Mr. Flower, Conservator of the Museum of the Royal College of Surgeons, was good enough to dissect for me; the latter, from the photograph ofa similarly dissected Chimpanzee's brain, given in Mr. Marshall's paperabove referred to. 'a', posterior lobe; 'b', lateral ventricle; 'c', posterior cornu; 'x', the hippocampus minor. ]

In fact, all the abundant and trustworthy evidence (consisting of theresults of careful investigations directed to the determination of thesevery questions, by skilled anatomists) which we now possess, leadsto the conviction that, so far from the posterior lobe, the posteriorcornu, and the hippocampus minor, being structures peculiar to andcharacteristic of man, as they have been over and over again assertedto be, even after the publication of the clearest demonstration of thereverse, it is precisely these structures which are the most markedcerebral characters common to man with the apes. They are among the mostdistinctly Simian peculiarities which the human organism exhibits. 

As to the convolutions, the brains of the apes exhibit every stage ofprogress, from the almost smooth brain of the Marmoset, to the Orangand the Chimpanzee, which fall but little below Man. And it is mostremarkable that, as soon as all the principal sulci appear, the patternaccording to which they are arranged is identical with that of thecorresponding sulci of man. The surface of the brain of a monkeyexhibits a sort of skeleton map of man's, and in the man-like apesthe details become more and more filled in, until it is only in minorcharacters, such as the greater excavation of the anterior lobes, theconstant presence of fissures usually absent in man, and the differentdisposition and proportions of some convolutions, that the Chimpanzee'sor the Orang's brain can be structurally distinguished from Man's. 

So far as cerebral structure goes, therefore, it is clear that Mandiffers less from the Chimpanzee or the Orang, than these do evenfrom the Monkeys, and that the difference between the brains of theChimpanzee and of Man is almost insignificant, when compared with thatbetween the Chimpanzee brain and that of a Lemur. 

It must not be overlooked, however, that there is a very strikingdifference in absolute mass and weight between the lowest humanbrain and that of the highest ape--a difference which is all the moreremarkable when we recollect that a full grown Gorilla is probablypretty nearly twice as heavy as a Bosjes man, or as many an Europeanwoman. It may be doubted whether a healthy human adult brain everweighed less than thirty-one or two ounces, or that the heaviest Gorillabrain has exceeded twenty ounces. 

This is a very noteworthy circumstance, and doubtless will one day helpto furnish an explanation of the great gulf which intervenes betweenthe lowest man and the highest ape in intellectual power; [6] but it haslittle systematic value, for the simple reason that, as may be concludedfrom what has been already said respecting cranial capacity, thedifference in weight of brain between the highest and the lowest menis far greater, both relatively and absolutely, than that betweenthe lowest man and the highest ape. The latter, as has been seen, isrepresented by, say twelve ounces of cerebral substance absolutely, orby 32:20 relatively; but as the largest recorded human brain weighedbetween 65 and 66 ounces, the former difference is represented bymore than 33 ounces absolutely, or by 65:32 relatively. Regardedsystematically, the cerebral differences of man and apes are not ofmore than generic value; his Family distinction resting chiefly on hisdentition, his pelvis, and his lower limbs. 

A man born dumb, notwithstanding his great cerebral mass and hisinheritance of strong intellectual instincts, would be capable of fewhigher intellectual manifestations than an Orang or a Chimpanzee, if hewere confined to the society of dumb associates. And yet there might notbe the slightest discernible difference between his brain and that ofa highly intelligent and cultivated person. The dumbness might be theresult of a defective structure of the mouth, or of the tongue, ora mere defective innervation of these parts; or it might result fromcongenital deafness, caused by some minute defect of the internal ear, which only a careful anatomist could discover. 

The argument, that because there is an immense difference between aMan's intelligence and an Ape's, therefore, there must be an equallyimmense difference between their brains, appears to me to be about aswell based as the reasoning by which one should endeavour to prove that, because there is a "great gulf" between a watch that keeps accuratetime and another that will not go at all, there is therefore a greatstructural hiatus between the two watches. A hair in the balance-wheel, a little rust on a pinion, a bend in a tooth of the escapement, asomething so slight that only the practised eye of the watchmaker candiscover it, may be the source of all the difference. 

And believing, as I do, with Cuvier, that the possession of articulatespeech is the grand distinctive character of man (whether it beabsolutely peculiar to him or not), I find it very easy to comprehend, that some equally inconspicuous structural difference may have been theprimary cause of the immeasurable and practically infinite divergence ofthe Human from the Simian Stirps. 

Thus, whatever system of organs be studied, the comparison of theirmodifications in the ape series leads to one and the same result--thatthe structural differences which separate Man from the Gorilla and theChimpanzee are not so great as those which separate the Gorilla from thelower apes. 

But in enunciating this important truth I must guard myself against aform of misunderstanding, which is very prevalent. I find, in fact, thatthose who endeavour to teach what nature so clearly shows us in thismatter, are liable to have their opinions misrepresented and theirphraseology garbled, until they seem to say that the structuraldifferences between man and even the highest apes are small andinsignificant. Let me take this opportunity then of distinctlyasserting, on the contrary, that they are great and significant; thatevery bone of a Gorilla bears marks by which it might be distinguishedfrom the corresponding bone of a Man; and that, in the present creation, at any rate, no intermediate link bridges over the gap between 'Homo'and 'Troglodytes'. 

It would be no less wrong than absurd to deny the existence of thischasm; but it is at least equally wrong and absurd to exaggerate itsmagnitude, and, resting on the admitted fact of its existence, to refuseto inquire whether it is wide or narrow. Remember, if you will, thatthere is no existing link between Man and the Gorilla, but do not forgetthat there is a no less sharp line of demarcation, a no less completeabsence of any transitional form, between the Gorilla and the Orang, orthe Orang and the Gibbon. I say, not less sharp, though it is somewhatnarrower. The structural differences between Man and the Man-like apescertainly justify our regarding him as constituting a family apart fromthem; though, inasmuch as he differs less from them than they do fromother families of the same order, there can be no justification forplacing him in a distinct order. 

And thus the sagacious foresight of the great lawgiver of systematiczoology, Linnaeus, becomes justified, and a century of anatomicalresearch brings us back to his conclusion, that man is a member of thesame order (for which the Linnaean term PRIMATES ought to be retained)as the Apes and Lemurs. This order is now divisible into seven families, of about equal systematic value: the first, the ANTHROPINI, containsMan alone; the second, the CATARHINI, embraces the old-world apes; thethird, the PLATYRHINI, all new-world apes, except the Marmosets; thefourth, the ARCTOPITHECINI, contains the Marmosets; the fifth, theLEMURINI, the Lemurs--from which 'Cheiromys' should probably be excludedto form a sixth distinct family, the CHEIROMYINI; while the seventh, the GALEOPITHECINI, contains only the flying Lemur 'Galeopithecus', --astrange form which almost touches on the Bats, as the 'Cheiromys' putson a rodent clothing, and the Lemurs simulate Insectivora. 

Perhaps no order of mammals presents us with so extraordinary a seriesof gradations as this--leading us insensibly from the crown and summitof the animal creation down to creatures, from which there is but astep, as it seems, to the lowest, smallest, and least intelligent ofthe placental Mammalia. It is as if nature herself had foreseenthe arrogance of man, and with Roman severity had provided that hisintellect, by its very triumphs, should call into prominence the slaves, admonishing the conqueror that he is but dust. 

These are the chief facts, this the immediate conclusion from themto which I adverted in the commencement of this Essay. The facts, Ibelieve, cannot be disputed; and if so, the conclusion appears to me tobe inevitable. 

But if Man be separated by no greater structural barrier from the brutesthan they are from one another--then it seems to follow that if anyprocess of physical causation can be discovered by which the generaand families of ordinary animals have been produced, that process ofcausation is amply sufficient to account for the origin of Man. In otherwords, if it could be shown that the Marmosets, for example, havearisen by gradual modification of the ordinary Platyrhini, or thatboth Marmosets and Platyrhini are modified ramifications of a primitivestock--then, there would be no rational ground for doubting that manmight have originated, in the one case, by the gradual modification ofa man-like ape; or, in the other case, as a ramification of the sameprimitive stock as those apes. 

At the present moment, but one such process of physical causationhas any evidence in its favour; or, in other words, there is but onehypothesis regarding the origin of species of animals in generalwhich has any scientific existence--that propounded by Mr. Darwin. ForLamarck, sagacious as many of his views were, mingled them with so muchthat was crude and even absurd, as to neutralize the benefit which hisoriginality might have effected, had he been a more sober and cautiousthinker; and though I have heard of the announcement of a formulatouching "the ordained continuous becoming of organic forms, " it isobvious that it is the first duty of a hypothesis to be intelligible, and that a qua-qua-versal proposition of this kind, which may be readbackwards, or forwards, or sideways, with exactly the same amount ofsignification, does not really exist, though it may seem to do so. 

At the present moment, therefore, the question of the relation of man tothe lower animals resolves itself, in the end, into the larger questionof the tenability, or untenability of Mr. Darwin's views. But herewe enter upon difficult ground, and it behoves us to define our exactposition with the greatest care. 

It cannot be doubted, I think, that Mr. Darwin has satisfactorily provedthat what he terms selection, or selective modification, must occur, anddoes occur, in nature; and he has also proved to superfluity that suchselection is competent to produce forms as distinct, structurally, assome genera even are. If the animated world presented us with none butstructural differences, I should have no hesitation in saying that Mr. Darwin had demonstrated the existence of a true physical cause, amplycompetent to account for the origin of living species, and of man amongthe rest. 

But, in addition to their structural distinctions, the species ofanimals and plants, or at least a great number of them, exhibitphysiological characters--what are known as distinct species, structurally, being for the most part either altogether incompetent tobreed one with another; or if they breed, the resulting mule, or hybrid, is unable to perpetuate its race with another hybrid of the same kind. 

A true physical cause is, however, admitted to be such only on onecondition--that it shall account for all the phenomena which comewithin the range of its operation. If it is inconsistent with anyone phenomenon, it must be rejected; if it fails to explain any onephenomenon, it is so far weak, so far to be suspected; though it mayhave a perfect right to claim provisional acceptance. 

Now, Mr. Darwin's hypothesis is not, so far as I am aware, inconsistentwith any known biological fact; on the contrary, if admitted, the factsof Development, of Comparative Anatomy, of Geographical Distribution, and of Palaeontology, become connected together, and exhibit a meaningsuch as they never possessed before; and I, for one, am fully convinced, that if not precisely true, that hypothesis is as near an approximationto the truth as, for example, the Copernican hypothesis was to the truetheory of the planetary motions. 

But, for all this, our acceptance of the Darwinian hypothesis must beprovisional so long as one link in the chain of evidence is wanting; andso long as all the animals and plants certainly produced by selectivebreeding from a common stock are fertile, and their progeny are fertilewith one another, that link will be wanting. For, so long, selectivebreeding will not be proved to be competent to do all that is requiredof it to produce natural species. 

I have put this conclusion as strongly as possible before the reader, because the last position in which I wish to find myself is that ofan advocate for Mr. Darwin's, or any other views--if by an advocate ismeant one whose business it is to smooth over real difficulties, and topersuade where he cannot convince. 

In justice to Mr. Darwin, however, it must be admitted that theconditions of fertility and sterility are very ill understood, and thatevery day's advance in knowledge leads us to regard the hiatus in hisevidence as of less and less importance, when set against the multitudeof facts which harmonize with, or receive an explanation from, hisdoctrines. 

I adopt Mr. Darwin's hypothesis, therefore, subject to the production ofproof that physiological species may be produced by selective breeding;just as a physical philosopher may accept the undulatory theory oflight, subject to the proof of the existence of the hypothetical ether;or as the chemist adopts the atomic theory, subject to the proof of theexistence of atoms; and for exactly the same reasons, namely, that ithas an immense amount of prima facie probability: that it is the onlymeans at present within reach of reducing the chaos of observed factsto order; and lastly, that it is the most powerful instrument ofinvestigation which has been presented to naturalists since theinvention of the natural system of classification, and the commencementof the systematic study of embryology. 

But even leaving Mr. Darwin's views aside, the whole analogy of naturaloperations furnishes so complete and crushing an argument againstthe intervention of any but what are termed secondary causes, in theproduction of all the phenomena of the universe; that, in view of theintimate relations between Man and the rest of the living world, andbetween the forces exerted by the latter and all other forces, I can seeno excuse for doubting that all are co-ordinated terms of Nature's greatprogression, from the formless to the formed--from the inorganic to theorganic--from blind force to conscious intellect and will. 

Science has fulfilled her function when she has ascertained andenunciated truth; and were these pages addressed to men of science only, I should now close this essay, knowing that my colleagues have learnedto respect nothing but evidence, and to believe that their highest dutylies in submitting to it, however it may jar against their inclinations. 

But desiring, as I do, to reach the wider circle of the intelligentpublic, it would be unworthy cowardice were I to ignore the repugnancewith which the majority of my readers are likely to meet the conclusionsto which the most careful and conscientious study I have been able togive to this matter, has led me. 

On all sides I shall hear the cry--"We are men and women, not a merebetter sort of apes, a little longer in the leg, more compact in thefoot, and bigger in brain than your brutal Chimpanzees and Gorillas. The power of knowledge--the conscience of good and evil--the pitifultenderness of human affections, raise us out of all real fellowship withthe brutes, however closely they may seem to approximate us. "

To this I can only reply that the exclamation would be most just andwould have my own entire sympathy, if it were only relevant. But, it isnot I who seek to base Man's dignity upon his great toe, or insinuatethat we are lost if an Ape has a hippocampus minor. On the contrary, Ihave done my best to sweep away this vanity. I have endeavoured to showthat no absolute structural line of demarcation, wider than that betweenthe animals which immediately succeed us in the scale, can be drawnbetween the animal world and ourselves; and I may add the expression ofmy belief that the attempt to draw a psychical distinction is equallyfutile, and that even the highest faculties of feeling and of intellectbegin to germinate in lower forms of life. [7] At the same time, no oneis more strongly convinced than I am of the vastness of the gulf betweencivilized man and the brutes; or is more certain that whether 'from'them or not, he is assuredly not 'of' them. No one is less disposedto think lightly of the present dignity, or desparingly of the futurehopes, of the only consciously intelligent denizen of this world. 

We are indeed told by those who assume authority in these matters, thatthe two sets of opinions are incompatible, and that the belief inthe unity of origin of man and brutes involves the brutalization anddegradation of the former. But is this really so? Could not a sensiblechild confute by obvious arguments, the shallow rhetoricians who wouldforce this conclusion upon us? Is it, indeed, true, that the Poet, orthe Philosopher, or the Artist whose genius is the glory of his age, isdegraded from his high estate by the undoubted historical probability, not to say certainty, that he is the direct descendant of some nakedand bestial savage, whose intelligence was just sufficient to make him alittle more cunning than the Fox, and by so much more dangerous thanthe Tiger? Or is he bound to howl and grovel on all fours because of thewholly unquestionable fact, that he was once an egg, which no ordinarypower of discrimination could distinguish from that of a Dog? Or is thephilanthropist or the saint to give up his endeavours to lead a noblelife, because the simplest study of man's nature reveals, at itsfoundations, all the selfish passions and fierce appetites of the merestquadruped? Is mother-love vile because a hen shows it, or fidelity basebecause dogs possess it?

The common sense of the mass of mankind will answer these questionswithout a moment's hesitation. Healthy humanity, finding itself hardpressed to escape from real sin and degradation, will leave the broodingover speculative pollution to the cynics and the 'righteous overmuch'who, disagreeing in everything else, unite in blind insensibility tothe nobleness of the visible world, and in inability to appreciate thegrandeur of the place Man occupies therein. 

Nay more, thoughtful men, once escaped from the blinding influencesof traditional prejudice, will find in the lowly stock whence Man hassprung, the best evidence of the splendour of his capacities; and willdiscern in his long progress through the Past, a reasonable ground offaith in his attainment of a nobler Future. 

They will remember that in comparing civilised man with the animalworld, one is as the Alpine traveller, who sees the mountains soaringinto the sky and can hardly discern where the deep shadowed crags androseate peaks end, and where the clouds of heaven begin. Surely theawe-struck voyager may be excused if, at first, he refuses to believethe geologist, who tells him that these glorious masses are, after all, the hardened mud of primeval seas, or the cooled slag of subterraneanfurnaces--of one substance with the dullest clay, but raised by inwardforces to that place of proud and seemingly inaccessible glory. 

But the geologist is right; and due reflection on his teachings, insteadof diminishing our reverence and our wonder, adds all the forceof intellectual sublimity to the mere aesthetic intuition of theuninstructed beholder. 

And after passion and prejudice have died away, the same result willattend the teachings of the naturalist respecting that great Alpsand Andes of the living world--Man. Our reverence for the nobility ofmanhood will not be lessened by the knowledge that Man is, in substanceand in structure, one with the brutes; for, he alone possesses themarvellous endowment of intelligible and rational speech, whereby, in the secular period of his existence, he has slowly accumulated andorganized the experience which is almost wholly lost with the cessationof every individual life in other animals; so that now he stands raisedupon it as on a mountain top, far above the level of his humble fellows, and transfigured from his grosser nature by reflecting, here and there, a ray from the infinite source of truth. 

'A succinct History of the Controversy respecting the Cerebral Structureof Man and the Apes. '

UP to the year 1857 all anatomists of authority, who had occupiedthemselves with the cerebral structure of the Apes--Cuvier, Tiedemann, Sandifort, Vrolik, Isidore G. St. Hilaire, Schroeder van der Kolk, Gratiolet--were agreed that the brain of the Apes possesses a POSTERIORLOBE. 

Tiedemann, in 1825, figured and acknowledged in the text of his 'Icones'the existence of the POSTERIOR CORNU of the lateral ventricle inthe Apes, not only under the title of 'Scrobiculus parvus loco cornuposterioris'--a fact which has been paraded--but as 'cornu posterius'('Icones', p. 54), a circumstance which has been, as sedulously, kept inthe background. 

Cuvier ('Lecons', T. Iii. P. 103) says, "the anterior or lateralventricles possess a digital cavity [posterior cornu] only in Man andthe Apes... Its presence depends on that of the posterior lobes. "

Schroeder van der Kolk and Vrolik, and Gratiolet, had also figured anddescribed the posterior cornu in various Apes. As to the HIPPOCAMPUSMINOR Tiedemann had erroneously asserted its absence in the Apes; butSchroeder van der Kolk and Vrolik had pointed out the existence of whatthey considered a rudimentary one in the Chimpanzee, and Gratiolet hadexpressly affirmed its existence in these animals. Such was the state ofour information on these subjects in the year 1856. 

In the year 1857, however, Professor Owen, either in ignorance of thesewell-known facts or else unjustifiably suppressing them, submitted tothe Linnaean Society a paper "On the Characters, Principles of Division, and Primary Groups of the Class Mammalia, " which was printed in theSociety's Journal, and contains the following passage:--"In Man, the brain presents an ascensive step in development, higher andmore strongly marked than that by which the preceding sub-classwas distinguished from the one below it. Not only do the cerebralhemispheres overlap and the olfactory lobes and cerebellum, but theyextend in advance of the one and further back than the other. Theposterior development is so marked, that anatomists have assigned tothat part the character of a third lobe; 'it is peculiar to thegenus Homo, and equally peculiar is the posterior horn of the lateralventricle and the 'hippocampus minor, ' which characterise the hindlobe of each hemisphere'. "--'Journal of the Proceedings of the LinnaeanSociety, Vol. Ii. P. 19. 

As the essay in which this passage stands had no less ambitious an aimthan the remodelling of the classification of the Mammalia, itsauthor might be supposed to have written under a sense of peculiarresponsibility, and to have tested, with especial care, the statementshe ventured to promulgate. And even if this be expecting too much, hastiness, or want of opportunity for due deliberation, cannot now bepleaded in extenuation of any shortcomings; for the propositions citedwere repeated two years afterwards in the Reade Lecture, deliveredbefore so grave a body as the University of Cambridge, in 1859. 

When the assertions, which I have italicised in the above extract, first came under my notice, I was not a little astonished at so flat acontradiction of the doctrines current among well-informed anatomists;but, not unnaturally imagining that the deliberate statements of aresponsible person must have some foundation in fact, I deemed it myduty to investigate the subject anew before the time at which itwould be my business to lecture thereupon came round. The result of myinquiries was to prove that Mr. Owen's three assertions, that "the thirdlobe, the posterior horn of the lateral ventricle, and the hippocampusminor, " are "pecular to the genus 'Homo', " are contrary to the plainestfacts. I communicated this conclusion to the students of my class;and then, having no desire to embark in a controversy which could notredound to the honour of British science, whatever its issue, I turnedto more congenial occupations. 

The time speedily arrived, however, when a persistence in this reticencewould have involved me in an unworthy paltering with truth. 

At the meeting of the British Association at Oxford, in 1860, ProfessorOwen repeated these assertions in my presence, and, of course, Iimmediately gave them a direct and unqualified contradiction, pledgingmyself to justify that unusual procedure elsewhere. I redeemed thatpledge by publishing, in the January number of the 'Natural HistoryReview' for 1861, an article wherein the truth of the three followingpropositions was fully demonstrated (l. C. P. 71):--

"1. That the third lobe is neither peculiar to, nor characteristic of, man, seeing that it exists in all the higher quadrumana. "

"2. That the posterior cornu of the lateral ventricle is neitherpeculiar to, nor characteristic of, man, inasmuch as it also exists inthe higher quadrumana. "

"3. That the 'hippocampus minor' is neither pecular to, norcharacteristic of, man, as it is found in certain of the higherquadrumana. "

Furthermore, this paper contains the following paragraph (p. 76): "Andlastly, Schroeder van der Kolk and Vrolik (op. Cit. P. 271), though theyparticularly note that 'the lateral ventricle is distinguished from thatof Man by the very defective proportions of the posterior cornu, whereinonly a stripe is visible as an indication of the hippocampus minor;' yetthe Figure 4, in their second Plate, shows that this posterior cornu isa perfectly distinct and unmistakeable structure, quite as large as itoften is in Man. It is the more remarkable that Professor Owen shouldhave overlooked the explicit statement and figure of these authors, asit is quite obvious, on comparison of the figures, that his woodcut ofthe brain of a Chimpanzee (l. C. P. 19) is a reduced copy of the secondfigure of Messrs. Schroeder van der Kolk and Vrolik's first Plate. 

"As M. Gratiolet (l. C. P. 18), however is careful to remark, 'unfortunately the brain which they have taken as a model was greatlyaltered (profondement affaisse), whence the general form of the brainis given in these plates in a manner which is altogether incorrect. 'Indeed, it is perfectly obvious, from a comparison of a section of theskull of the Chimpanzee with these figures, that such is the case; andit is greatly to be regretted that so inadequate a figure should havebeen taken as a typical representation of the Chimpanzee's brain. "

From this time forth, the untenability of his position might have beenas apparent to Professor Owen as it was to every one else; but, so farfrom retracting the grave errors into which he had fallen, ProfessorOwen has persisted in and reiterated them; first, in a lecture deliveredbefore the Royal Institution on the 19th of March, 1861, which isadmitted to have been accurately reproduced in the 'Athenaeum' for the23rd of the same month, in a letter addressed by Professor Owen to thatjournal on the 30th of March. The 'Athenaeum report was accompanied bya diagram purporting to represent a Gorilla's brain, but in reality soextraordinary a misrepresentation, that Professor Owen substantially, though not explicitly, withdraws it in the letter in question. Inamending this error, however, Professor Owen fell into another ofmuch graver import, as his communication concludes with the followingparagraph: "For the true proportion in which the cerebrum covers thecerebellum in the highest Apes, reference should be made to the figureof the undissected brain of the Chimpanzee in my 'Reade's Lecture on theClassification, etc. , of the Mammalia', p. 25, fig. 7, 8 vo. 1859. "

It would not be credible, if it were not unfortunately true, that thisfigure, to which the trusting public is referred, without a word ofqualification, "for the true proportion in which the cerebrum covers thecerebellum in the highest Apes, " is exactly that unacknowledged copy ofSchroeder van der Kolk and Vrolik's figure whose utter inaccuracy hadbeen pointed out years before by Gratiolet, and had been brought toProfessor Owen's knowledge by myself in the passage of my article in the'Natural History Review' above quoted. 

I drew public attention to this circumstance again in my reply toProfessor Owen, published in the 'Athenaeum' for April 13th, 1861; butthe exploded figure was reproduced once more by Professor Owen, withoutthe slightest allusion to its inaccuracy, in the 'Annals of NaturalHistory' for June 1861!

This proved too much for the patience of the original authors of thefigure, Messrs. Schroeder van der Kolk and Vrolik, who, in a noteaddressed to the Academy of Amsterdam, of which they were members, declared themselves to be, though decided opponents of all forms of thedoctrine of progressive development, above all things, lovers of truth:and that, therefore, at whatever risk of seeming to lend support toviews which they disliked, they felt it their duty to take the firstopportunity of publicly repudiating Professor Owen's misuse of theirauthority. 

In this note they frankly admitted the justice of the criticisms ofM. Gratiolet, quoted above, and they illustrated, by new and carefulfigures, the posterior lobe, the posterior cornu, and the hippocampusminor of the Orang. Furthermore, having demonstrated the parts, atone of the sittings of the Academy, they add, "la presence des partiescontestees y a ete universellement reconnue par les anatomistes presentsa la seance. Le seul doute qui soit reste se rapporte au pes Hippocampiminor.... A l'etat frais l'indice du petit pied d'Hippocampe etait plusprononce que maintenant. "

Professor Owen repeated his erroneous assertions at the meeting of theBritish Association in 1861, and again, without any obvious necessity, and without adducing a single new fact or new argument, or being ablein any way to meet the crushing evidence from original dissections ofnumerous Apes' brains, which had in the meanwhile been brought forwardby Prof. Rolleston, [8] F. R. S. , Mr. Marshall, [9] F. R. S. , Mr. Flower, [10] Mr. Turner, [11] and myself, [12] revived the subject at theCambridge meeting of the same body in 1862. Not content with thetolerably vigorous repudiation which these unprecedented proceedingsmet with in Section D, Professor Owen sanctioned the publication ofa version of his own statements, accompanied by a strangemisrepresentation of mine (as may be seen by comparison of the 'Times'report of the discussion), in the 'Medical Times' for October 11th, 1862. I subjoin the conclusion of my reply in the same journal forOctober 25th. 

"If this were a question of opinion, or a question of interpretation ofparts or of terms, --were it even a question of observation in whichthe testimony of my own senses alone was pitted against that of anotherperson, I should adopt a very different tone in discussing this matter. I should, in all humility, admit the likelihood of having myself erredin judgment, failed in knowledge, or been blinded by prejudice. 

"But no one pretends now, that the controversy is one of the terms orof opinions. Novel and devoid of authority as some of Professor Owen'sproposed definitions may have been, they might be accepted withoutchanging the great features of the case. Hence though specialinvestigations into these matters have been undertaken during the lasttwo years by Dr. Allen Thomson, by Dr. Rolleston, by Mr. Marshall, and by Mr. Flower, all, as you are aware, anatomists of repute in thiscountry, and by Professors Schroeder Van der Kolk, and Vrolik (whomProfessor Owen incautiously tried to press into his own service) onthe Continent, all these able and conscientious observers have withone accord testified to the accuracy of my statements, and to the utterbaselessness of the assertions of Professor Owen. Even the venerableRudolph Wagner, whom no man will accuse of progressionist proclivities, has raised his voice on the same side; while not a single anatomist, great or small, has supported Professor Owen. 

"Now, I do not mean to suggest that scientific differences should besettled by universal suffrage, but I do conceive that solid proofs mustbe met by something more than empty and unsupported assertions. Yetduring the two years through which this preposterous controversy hasdragged its weary length, Professor Owen has not ventured to bringforward a single preparation in support of his often-repeatedassertions. 

"The case stands thus, therefore:--Not only are the statements made byme in consonance with the doctrines of the best older authorities, and with those of all recent investigators, but I am quite ready todemonstrate them on the first monkey that comes to hand; while ProfessorOwen's assertions are not only in diametrical opposition to both oldand new authorities, but he has not produced, and, I will add, cannotproduce, a single preparation which justifies them"

I now leave this subject, for the present. --For the credit of mycalling I should be glad to be, hereafter, for ever silent upon it. But, unfortunately, this is a matter upon which, after all that has occurred, no mistake or confusion of terms is possible--and in affirming that theposterior lobe, the posterior cornu, and the hippocampus minor exist incertain Apes, I am stating either that which is true, or that whichI must know to be false. The question has thus become one of personalveracity. For myself, I will accept no other issue than this, grave asit is, to the present controversy. 

FOOTNOTES:

[Footnote 1: It will be understood that, in the preceding Essay, I haveselected for notice from the vast mass of papers which have been writtenupon the man-like Apes, only those which seem to me to be of specialmoment. 

[Footnote 2: We are not at present thoroughly acquainted with the brainof the Gorilla, and therefore, in discussing cerebral characters, Ishall take that of the Chimpanzee as my highest term among the Apes. ]

[Footnote 3: "More than once, " says Peter Camper, "have I met with morethan six lumbar vertebrae in man.... Once I found thirteen ribs and fourlumbar vertebrae. " Fallopius noted thirteen pair of ribs and only fourlumbar vertebrae; and Eustachius once found eleven dorsal vertebrae andsix lumbar vertebrae. --'Oeuvres de Pierre Camper', T. 1, p. 42. AsTyson states, his 'Pygmie' had thirteen pair of ribs and five lumbarvertebrae. The question of the curves of the spinal column in the Apesrequires further investigation. ]

[Footnote 4: It has been affirmed that Hindoo crania sometimes containas little as 27 ounces of water, which would give a capacity of about46 cubic inches. The minimum capacity which I have assumed above, however, is based upon the valuable tables published by Professor R. Wagner in his "Vorstudien zu einer wissenschaftlichen Morphologie undPhysiologie des menschlichen Gehirns. " As the result of the carefulweighing of more than 900 human brains, Professor Wagner states thatone-half weighed between 1200 and 1400 grammes, and that abouttwo-ninths, consisting for the most part of male brains, exceed 1400grammes. The lightest brain of an adult male, with sound mentalfaculties, recorded by Wagner, weighed 1020 grammes. As a gramme equals15. 4 grains, and a cubic inch of water contains 252. 4 grains, this isequivalent to 62 cubic inches of water; so that as brain is heavier thanwater, we are perfectly safe against erring on the side of diminution intaking this as the smallest capacity of any adult male human brain. Theonly adult male brain, weighing as little as 970 grammes, is that of anidiot; but the brain of an adult woman, against the soundness of whosefaculties nothing appears, weighed as little as 907 grammes (55. 3 cubicinches of water); and Reid gives an adult female brain of still smallercapacity. The heaviest brain (1872 grammes, or about 115 cubic inches)was, however, that of a woman; next to it comes the brain of Cuvier(1861 grammes), then Byron (1807 grammes), and then an insane person(1783 grammes). The lightest adult brain recorded (720 grammes) wasthat of an idiotic female. The brains of five children, four years old, weighed between 1275 and 992 grammes. So that it may be safely said, that an average European child of four years old has a brain twice aslarge as that of an adult Gorilla. ]

[Footnote 5: In speaking of the foot of his "Pygmie, " Tyson remarks, p. 13:-- "But this part in the formation and in its function too, beingliker a Hand than a Foot: for the distinguishing this sort of animalsfrom others, I have thought whether it might not be reckoned and calledrather Quadru-manus than Quadrupes, 'i. E. ' a four-handed rather than afour-footed animal. "]

[Footnote 6: I say 'help' to furnish: for I by no means believe thatit was any original difference of cerebral quality, or quantity whichcaused that divergence between the human and the pithecoid stirpes, which has ended in the present enormous gulf between them. It isno doubt perfectly true, in a certain sense, that all difference offunction is a result of difference of structure; or, in other words, ofdifference in the combination of the primary molecular forces ofliving substance; and, starting from this undeniable axiom, objectorsoccasionally, and with much seeming plausibility, argue that the vastintellectual chasm between the Ape and Man implies a correspondingstructural chasm in the organs of the intellectual functions; so that, it is said, the non-discovery of such vast differences proves, not thatthey are absent, but that Science is incompetent to detect them. A verylittle consideration, however, will, I think, show the fallacy of thisreasoning. Its validity hangs upon the assumption, that intellectualpower depends altogether on the brain--whereas the brain is only onecondition out of many on which intellectual manifestations depend;the others being, chiefly, the organs of the senses and the motorapparatuses, especially those which are concerned in prehension and inthe production of articulate speech. ]

[Footnote 7: It is so rare a pleasure for me to find Professor Owen'sopinions in entire accordance with my own, that I cannot forbear fromquoting a paragraph which appeared in his Essay "On the Characters, etc. , of the Class Mammalia, " in the 'Journal of the Proceedings of theLinnean Society of London' for 1857, but is unaccountably omitted in the"Reade Lecture" delivered before the University of Cambridge two yearslater, which is otherwise nearly a reprint of the paper in question. Prof. Owen writes: "Not being able to appreciate or conceive of thedistinction between the psychical phenomena of a Chimpanzee, and of aBoschisman or of an Aztec, with arrested brain growth, as being of anature so essential as to preclude a comparison between them, or asbeing other than a difference of degree, I cannot shut my eyes to thesignificance of that all-pervading similitude of structure--every tooth, every bone, strictly homologous--which makes the determination of thedifference between 'Homo' and 'Pithecus' the anatomist's difficulty. "Surely it is a little singular, that the 'anatomist, ' who finds it'difficult' to 'determine the difference' between 'Homo' and 'Pithecus', should yet range them on anatomical grounds, in distinct sub-classes!]

[Footnotes 8: On the Affinities of the Brain of the Orang. 'Nat. Hist. Review', April, 1861. ]

[Footnotes 9: On the Brain of a young Chimpanzee. 'Ibid. ', July, 1861. ]

[Footnotes 10: On the Posterior lobes of the Cerebrum of the Quadrumana. 'Philosophical Transactions', 1862. ]

[Footnotes 11: On the anatomical Relations of the Surfaces of theTentorium to the Cerebrum and Cerebellum in Man and the lower Mammals. 'Proceedings of the Royal Society of Edinburgh', March, 1862. ]

[Footnotes 12: On the Brain of Ateles. 'Proceedings of ZoologicalSociety', 1861. ]