To understand rightly the construction of the human body, and to compare our own limbs and organs with those of other animals, requires a thorough knowledge of anatomy and physiology. It will not be attempted here to draw up an abstract of these sciences, for which such handbooks should be studied as Huxley’s Elementary Physiology and Mivart’s Elementary Anatomy. But it will be useful to give a slight outline of the evidence as to man’s place in the animal world, which may be done without requiring special knowledge in the reader.

That the bodies of other animals more or less correspond in structure to our own is one of the lessons we begin to learn in the nursery. Boys playing at horses, one on all-fours and the other astride on his back, have already some notion how the imagined horse matches a real one as to head, eyes, and ears, mouth and teeth, back and legs. If one questions a country lad sitting on a stile watching the hunters go by, he knows well enough that the huntsman and his horse, the hounds and the hare they are chasing, are all creatures built up on the same kind of bony scaffolding or skeleton, that their life is carried on by means of similar organs, lungs to breathe with, a stomach to digest the food taken in by the mouth and gullet, a heart to drive the blood through the vessels, while the eyes, ears, and nostrils receive in them all in like manner the impressions of sight, hearing, and smell. Very likely the peasant has taken all this as a matter of course without ever reflecting on it, and even more educated people are apt to do the same. Had it come as a new discovery, it would have set any intelligent mind thinking what must be the tie or connexion between creatures thus formed as it were on one original pattern, only varied in different modes for different ends. The scientific comparison of animals, even when made in the most elementary way, does at once bring this great problem before our minds. In some cases, more exact knowledge shows that the first rough comparison of man and beast may want correction. For instance, when a man’s skeleton and a horse’s are set side by side, it becomes plain that the horse’s knee and hock do not answer, as is popularly supposed, to our elbow and knee, but to our wrist and ankle. The examination of the man’s limb and the horse’s leads to a further and remarkable conclusion, that the horse’s fore- and hind-leg really correspond to a man’s arm and leg in which all the fingers and toes should have become useless and shrunk away, except one finger and one toe, which are left to be walked upon, with the nail become a hoof. The general law to be learnt from the series of skeletons in a natural history museum, is that through order after order of fishes, reptiles, birds, beasts, up to man himself, a common type or pattern may be traced, belonging to all animals which are vertebrate, that is, which have a backbone. Limbs may still be recognised though their shape and service have changed, and though they may even have dwindled into remnants, as if left not for use, but to keep up the old model. Thus, although a perch’s skeleton differs so much from a man’s, its pectoral and ventral fins still correspond to arms and legs. Snakes are mostly limbless, yet there are forms which connect them with the quadrupeds, as for instance, the boa-constrictor’s skeleton shows a pair of rudimentary hind-legs. The Greenland whale has no visible hind-limbs, and its fore-limbs are paddles or flippers, yet when dissected, the skeleton shows not only remnants of what in man would be the leg-bones, but the flipper actually has within it the set of bones which belong to the human arm and hand. It is popularly considered that man is especially distinguished from the lower animals by not having a tail; yet the tail is plainly to be seen in the human skeleton, represented by the last tapering vertebræ of the spine.

All these are animals now living. But geology shows that in long-past ages the earth has been inhabited by species different from those at present existing, and yet evidently related to them. In the tertiary period, Australia was distinguished as now by its marsupial or pouched animals, but these were not of any present species, and mostly far larger; even the tallest kangaroo now to be seen is a puny creature in comparison with the enormous extinct diprotodon, whose skull was three feet long. So in South America there lived huge edentate animals, now poorly represented by the sloths, anteaters and armadillos, to be seen in our Zoological Gardens. Elephants are found fossil in the miocene deposits, but the species were all different from those in Africa and India now. These are common examples of the great principle now received by all zoologists, that from remote geological antiquity there have from time to time appeared on earth new species of animals, so far similar to those which came before them as to look as if the old types had been altered to fit new conditions of life, the earlier forms then tending to die out and disappear. This relation between the older species of vertebrate animals and the newer species which have supplanted them, is a matter of actual observation, and beyond dispute. Many zoologists, now perhaps the majority, go a step farther than this, not only acknowledging that there is a relation between the new species and the old, but seeking to explain it by the hypothesis of descent or development, now often called, from its great modern expounder, the Darwinian theory. The formation of breeds or varieties of animals being an admitted fact, it is argued that natural variation under changed conditions of life can go far enough to produce new species, which by better adaptation to climate and circumstances may supplant the old. On this theory, the present kangaroos of Australia, sloths of South America, and elephants of India, are not only the successors but the actual descendants of extinct ones, and the fossil bones of tertiary horse-like animals with three-toed and four-toed feet show what the remote ancestors of our horses were like, in ages before the unused toes dwindled to the splint-bones which represent them in the horse’s leg now. According to the doctrine of descent, when several species of animals living at the same time show close resemblance in structure, it is inferred that this resemblance must have been inherited by all from one ancestral species. Now of all the mammalia, or animals which suckle their young, those whose structure brings them closest to man are the apes or monkeys, and among these the catarhine or near-nostrilled apes of the Old World, and among these the group called anthropoid or manlike, which inhabit tropical forests from Africa to the Eastern Archipelago. By now comparing their skeletons, it will be seen that in any scale of nature or scheme of creation these animals must be placed in somewhat close relation to man. No competent anatomist who has examined the bodily structure of these apes considers it possible that man can be descended from any of them, but according to the doctrine of descent they appear as the nearest existing offshoots from the same primitive stock whence man also came.

Professor Huxley’s Man’s Place in Nature, in which this anatomical comparison is made, contains a celebrated drawing which is copied in Fig. 5 as the readiest means of showing how the anthropoid apes correspond bone for bone with ourselves. At the same time it illustrates some main points in which their bodily actions are unlike ours. It has been said that the child first takes on him the dignity of man when he leaves off going on all-fours. But in fact, standing and walking upright is not a mere matter of training; it belongs to the arrangement of the human body being different from that of quadrupeds. The limbs of the dog or cow are so proportioned as to bring them down on all-fours, and this is to a less degree the case with the apes, while the head and trunk of the growing child are lifted toward the erect attitude by the disproportionate growth of the lower limbs. Though man’s standing upright requires continued muscular effort, he is so built as to keep his balance more readily than other animals in this position. It may be noticed from the figure how in man the opening at the base of the skull (occipital foramen) through which the spinal cord passes up into the brain, is farther to the front than in the apes, so that his skull, instead of pitching forward, is balanced on the top of the atlas vertebra (so called from Atlas supporting the globe). The figure shows also the S-like curvature of man’s spine, and how the bony pelvis or basin forms a broad support for his intestines as he stands upright, in which attitude the feet serve as bases enabling the legs to carry the trunk. Thus the erect posture, only imitated with difficult effort by the showman’s performing animals, is to man easy and unconstrained. Not through great differences of structure, but by adjustments of bones and muscles, the fore- and hind-limbs of quadrupeds work in accord, while in man, whose muscular adaptation is for going on his legs, there is no such reciprocal action between the legs and arms. Of the monkey tribes, many walk fairly on all-fours as quadrupeds, with legs bent, arms straightened forward, soles and palms touching the ground. But the higher manlike apes are adapted by their structure for a climbing life among the trees, whose branches they grasp with feet and hands. When the orang-utan takes to the ground he shambles clumsily along, generally putting down the outer edge of the feet and the bent knuckles of the hands. The orang and gorilla have the curious habit of resting on their bent fists, so as to draw their bodies forward between their long arms, like a cripple between his crutches. The nearest approach that apes naturally make to the erect attitude, is where the gibbon will go along on its feet, touching the ground with its knuckles first on one side and then on the other, or will run some distance with its arms thrown back above its head to keep the balance, or when the gorilla will rise on its legs and rush forward to attack. All these modes of locomotion may be understood from the skeletons in the figure. The apes thus present interesting intermediate stages between quadruped and biped. But only man is so formed that, using his feet to carry him, he has his hands free for their special work.

In comparing man with the lower animals, it is wrong to set down his pre-eminence entirely to his mind, without noticing the superiority of his limbs as instruments for practical arts. If one looks at the illustrations to “Reynard the Fox,” where the artist does his best to represent the lion holding a sceptre, the she-wolf flirting a fan, or the fox writing a letter; what he really shows is, how ill adapted the limbs of quadrupeds are to such actions. Man’s being the “tool-using animal” is due to his having hands to use the tool as well as mind to invent it; and only the apes, as most nearly approaching man in their limbs, can fairly imitate the use of such instruments as a spoon or a knife. In Fig. 6 the hand and foot of the chimpanzee may be compared with those of man. Here the ape’s foot b, looks so like a hand, that many naturalists have classed the higher apes under the name of four-handed animals, or quadrumana. In anatomical structure it is a foot, but it is a prehensile or grasping foot, able to clip or pinch an object by setting the great toe thumb-wise against the others, which the human foot d, cannot do. It is true that among people who go barefoot the great toe is not quite so helpless as that of a boot-wearing European. With the naked foot the savage Australian picks up his spear, and the Hindu tailor holds his cloth as he squats sewing. The above drawing is purposely taken, not from the free foot of the savage, but from the European foot cramped by the stiff leather boot, because this shows in the utmost way the contrast between ape and man. In the ape, it is seen that both the hands and feet gain their suitability for a tree-climbing life at the loss of their suitability for walking on the ground. But man’s upper and lower extremities have become differentiated or specialised in two opposite ways, the human foot becoming a stepping-machine with less grasping-power than the ape-foot, while the human hand comes to excel the ape-hand as a special organ for feeling, holding, and handling. The figure c shows the longer and freely-acting thumb and the wider flexible palm in man, the sensitive cushions at our finger-ends also giving us greater delicacy of touch. It is most instructive to visit the monkey-house at the Zoological Gardens for the purpose of comparing hands of high and low kinds. The hand of the marmoset with its five claw-nailed digits, is a mere grasping instrument hardly capable of handling. Other low monkeys have the thumbs small and not opposable, that is, their ends do not meet those of the other fingers, whereas the thumbs of the higher apes are (as the figure shows) opposable like ours. How far the value of the hand as a mechanical instrument depends on this opposability, any one may satisfy himself by using his hand with the thumb stiff. It is plain that man’s hand, enabling him to shape and wield weapons and tools to subdue nature to his own ends, is one cause of his standing first among animals. It is not so obvious, but it is true, that his intellectual development must have been in no small degree gained by the use of his hands. From handling objects, putting them in different positions, and setting them side by side, he was led to those simplest kinds of comparing and measuring which are the first elements of exact knowledge, or science.

Outwardly, the shaggy hair of the apes contrasts with the comparative nakedness of the human skin. In man as in lower animals, the thatch of hair indeed forms an effective shelter to the head. The hairy fringe round the human mouth in the adult male has in some races a strong growth, as in the European or the native of Australia. But in others, as the African negro and the so-called American Indian, the scanty face-hair looks as though it had dwindled to the mere remnant of a fuller growth. Looked at in this way, the hairy patches on the Englishman’s breast and limbs, though practically of no importance, are an object of curious interest to the naturalists who consider them relics from the remote period when man’s ancestral stock had a fuller hairy covering, whose want is now supplied by artificial shelter suited to season and climate. It is interesting to notice that there are some few human beings to be met with, whose faces and bodies are largely covered with long shaggy hair. Such a face-covering hides the play of feature—that expressive means of intercourse between mind and mind. Had the skeletons of apes and man in our figure been clothed with flesh, we should have seen plainly the signs of man’s higher organisation in the flexible versatile features, in whose movements and folds are symbolised the pleasures and pains, the loves and hates, of every phase of human life. How coarse and clumsy are the corresponding changes of face in the monkey-tribes, such as the drawing back of the corners of the mouth and wrinkling of the lower eyelid which constitute an ape’s smile, or the rise and fall of the baboon’s eyebrow’s and forehead in anger. The visitor from some other planet, so often imagined as coming to our earth and forming his judgments by what he sees, might well discern in the difference between man’s face and the gorilla’s muzzle some measure of the discrepancy within.

The brain being the instrument or organ of mind, anatomists comparing the brains of animals have looked for well-marked distinctions between the less and the more intelligent. In the natural order of Primates, to which man belongs with the monkeys and lemurs, the series of brains shows a remarkable rise or development from lower to higher forms. The lemur has a small and comparatively smooth brain, whereas the high anthropoid apes have brains which strikingly approach man’s. In fact the lemur has very little mind in comparison with the sagacious and teachable chimpanzee or orang-utan. But man’s reason so vastly surpasses that of the highest apes, that naturalists have wondered at the likeness of their brain to ours, which is illustrated in the accompanying Fig. 7, representing the brain of the chimpanzee a, and of man b, whole on the left to show the convolutions, and cut across on the right to expose the interior. To compare their structure the two brains are drawn of the same size, but in fact the chimpanzee brain is much smaller than the human. It is one great difference between man and the anthropoid apes, that his brain exceeds theirs in quantity; in a rough way he has three pounds of brain to their one. It is seen also that in the ape-brain the lobes or hemispheres have fewer and simpler windings than the more complex convolutions of the human brain, which in general outline they resemble. Now both size and complexity mean mind-power. The lobes of the brain consist within of the “white matter” with its innumerable fibres carrying nerve-currents, while the outer coating is formed of the “grey matter,” containing the brain-corpuscles or cells from which the fibres issue, and which are centres through which the combinations are made which we are conscious of as thoughts. As the coating of grey matter follows the foldings of the brain down into the fissures, it is evident that the increased complexity of the convolutions, combined with greater actual size of brain, furnishes man with a vastly more extensive and intricate thinking-apparatus than the animals nearest below him in the order of nature.

Having looked at some of the important differences between the bodies of man and lower animals, we may venture to ask the still harder question, How far do their minds work like ours? No full answer can be given, yet there are some well ascertained points to judge by. To begin, it is clear that the simple processes of sense, will, and action, are carried on in man by the same bodily machinery as in other high vertebrate animals. How like their organs of sense are, is well illustrated by the anatomist who dissects a bullock’s eye as a substitute for a man’s, to show how the picture of the outer world is thrown by the lenses on the retina or screen, into which spread the end-fibres of the optic nerve leading into the brain. Not but what the touch, sight, and other senses in the various orders of animals have their special differences, as where the eagle’s eyes are focussed to see small objects far beyond man’s range, while the horse’s eyes are so set in his head that they do not converge like ours, and he must practically have two pictures of the two sides of the road to deal with. Such special differences, however, make the general resemblance all the more striking. Next, the nervous system in beast and man shows the same common plan, the brain and spinal cord forming a central nervous organ, to which the sensory nerves convey the messages of the senses, and from which the motor nerves carry the currents causing muscular contraction and movement. The involuntary acts of animals are like our own, as when the sleeping dog draws his leg back if it is touched, much as his master would do, and when awake, both man and beast wink when a finger pretends to strike at their eyes. If we go on to voluntary actions, done with conscious will and thought, the lower creatures can for some distance keep company with mankind. At the Zoological Gardens one may sometimes see a handful of nuts divided between the monkeys inside the bars and the children outside, and it is instructive to notice how nearly both go through the same set of movements, looking, approaching, elbowing, grasping, cracking, munching, swallowing, holding out their hands for more. Up to this level, the monkeys show all the mental likeness to man that their bodily likeness would lead us to expect. Now we know that in the scramble, there passes in the children’s minds a great deal besides the mere sight and feel of the nuts, and the will to take and eat them. Between the sensation and action there takes place thought. To describe it simply, the boy knows a nut by sight, wishes to renew the pleasant taste of former nuts, and directs his hands and mouth to grasp, crack, and eat. But here are complicated mental processes. Knowing a nut by sight, or having an idea of a nut, means that there are grouped together in the child’s mind memories of a number of past sensations, which have so become connected by experience that a particular form and colour, feel and weight, lead to the expectation of a particular flavour. Of what here takes place in the boy’s mind we can judge, though by no means clearly, from what we know about our own thoughts and what others have told us about theirs. What takes place in the monkeys’ minds we can only guess by watching their actions, but these are so like the human as to be most readily explained by considering their brain-work also to be like the human, though less clear and perfect. It seems as though a beast’s idea or thought of an object may be, as our own, a group of remembered sensations compacted into a whole. What makes this the more likely is that when part of the sensations present themselves, the animal seems to judge that the rest must be there also, much as we ourselves are so apt to do. Thus a dog will jump upon a scum-covered stream which it takes for dry land, or when offered a sham biscuit will come for it, turning away when smell and taste prove that the rest of the idea does not agree with what sight suggested.

In much the same way, all people who attend to the proceedings of animals, account for them by faculties more or less like their own. Not only do creatures of all high orders give unmistakable signs of pleasure and pain, but our dealings with the brutes go on the ground of their sharing with us such more complex emotions as fear, affection, anger, nay, even curiosity, jealousy, and revenge. Some of these show themselves in bodily symptoms which are quite human, as every one must admit who has felt the trembling limbs and throbbing heart of a frightened puppy, or looked at the picture in Darwin’s Expression of the Emotions of the chimpanzee who has had his fruit taken from him, and displays his sulkiness by a pout which is a caricature of a child’s. Again, the lower animals show a well-marked will, which like man’s is not simply wish, but the resultant or balance of wishes, so that it is possible for two people calling a dog different ways, or both offering him bones, to distract his will in a way that reminds us of the philosopher’s imaginary ass that died of starvation between its hay and its water. As to the power of memory in brutes, we have all had opportunities of noticing how lasting and exact it is. Some things which the animals remember may be explained simply by their ideas becoming associated through habit, as when the horse betrays its former owner’s ways by stopping at every public-house; this may only mean that the familiar door suggests to the beast the memory of rest, and he stops. But to watch a dog dreaming makes us think that whole trains of ideas from the storehouse of memory are passing before his consciousness, as in our dreams. A memory in which such a revival of the past is possible, is a source of experience whence to extract understanding of the present, and foresight of the future. To make the memory of what has been, the means of controlling what shall be, is the great intellectual faculty in man, and in simple and elementary forms it comes into view among lower creatures. To tell but one of the innumerable animal stories which show expectation and design founded on experience. A certain Mr. Cops, who had a young orang-utan, one day gave it half an orange, put the other half away out of its sight on a high press, and lay down himself on the sofa, but the ape’s movements attracting his attention, he only pretended to go to sleep; the creature came cautiously and satisfied himself of his master being asleep, then climbed up the press, ate the rest of the orange, carefully hid the peel among some shavings in the grate, examined the pretended sleeper again, and then went to lie down on his own bed. Such behaviour is only to be explained by a train of thought involving something of what in ourselves we call reason.

To measure the differences between beast and man is really more difficult than tracing their resemblances. One plain mark of the higher intellectual rank of man is that he is less dependent on instinct than the animals which migrate at a fixed season, or build nests of a fixed and complicated pattern peculiar to their kind. Man has some instincts plainly agreeing with those of inferior animals, such as the child’s untaught movements to ward off danger, and the parental affection which preserves the offspring during the first defenceless period of life. But if man were possessed by a resistless longing to set off wandering southward before winter, or to build a shelter of boughs laid in a particular way, this would be less beneficial to his species than the use of intelligent judgment adapting his actions to climate, supply of food, danger from enemies, and a multitude of circumstances differing from district to district, and changing from year to year. If man’s remote progenitors had instincts like the beavers’ implanted in the very structure of their brain, these instincts have long ago fallen away, displaced by freer and higher reason. Man’s power of accommodating himself to the world he lives in, and even of controlling it, is largely due to his faculty of gaining new knowledge. Yet it must not be overlooked that this faculty is in a less measure possessed by other animals. We may catch them in the act of learning by experience, which is indeed one of the most curious sights in natural history, as when telegraph-wires are set up in a new district, and after the second year partridges no longer kill themselves by flying against them, or where in Canada the wily marten baffles the trapper’s ingenuity, finding out how to get the bait away, even from a new kind of trap, without letting it fall. The faculty of learning by imitation comes out in the apes in an almost human way. The anthropoid ape Mafuka, kept lately in the Zoological Gardens at Dresden, saw how the door of her cage was unlocked, and not only did it herself, but even stole the key and hid it under her arm for future use; after watching the carpenter she seized his bradawl and bored holes with it through the little table she had her meals on; at her meals she not only filled her own cup from the jug, but, what is more remarkable, she carefully stopped pouring before it ran over. The death of this ape had an almost human pathos; when her friend the director of the gardens came to her, she put her arms round his neck, kissed him three times, and then lay down on her bed and giving him her hand fell into her last sleep. One cannot but think that creatures so sagacious must learn in their wild state. Indeed less clever animals seem to some extent to teach their young, birds to sing, wolves to hunt, although it is most difficult for naturalists in such cases to judge what comes by instinct and what is consciously learnt.

Philosophers have tried to draw a hard and fast line between the animal and human mind. The most celebrated of these attempts is Locke’s, where in his Essay concerning Human Understanding he lays it down that beasts indeed have ideas, but are without man’s faculty of forming abstract or general ideas. Now it is true that we have learnt to reason with abstract ideas, such as solidity and fluidity, quantity and quality, vegetable and animal, courage and cowardice; and that there is not the least reason to suppose that such abstractions are formed by dogs or apes. But though the faculty of thus abstracting and generalising is one which rises to the highest flights of philosophic thought, it must be borne in mind that it begins in easy mental acts which seem quite possible to animals. Abstraction is noticing what several thoughts have in common, and neglecting their differences; thus a general idea is obtained by not attending too closely to particulars. The simplest form of this is when only one sense at a time is attended to, as in Locke’s example of the idea of whiteness, as being that which chalk, snow, and milk, agree in. But, to judge by animals’ actions, they also will attend to one sense at a time, as where a bull is excited by anything red. And it is most interesting to watch animals comparing a new object with their recollections or ideas of previous ones, practically recognising in it what is already familiar, and expecting it to behave like other individuals of its class. Cats or monkeys do not require to be shown the use of a fresh rug or cushion, when it is at all like the old one it is put in place of, and the “dog of the regiment” will accept any man in the uniform as a master, whether he has seen him before or not. Thus, the very simplicity of animal thought foreshadows the results of man’s higher abstraction and generalisation. Let us now read a few lines farther in Locke, and we shall see why he concludes that animals have not the power of forming abstract ideas. It is, he says, because they have no use of words or other general signs. But this itself is an easier point and far more worth arguing, than the hard question whether brutes have abstract ideas. In fact the power of speech gives about the clearest distinction that can be drawn between the action of mind in beast and man. It is far more satisfactory than another division attempted by philosophers who lay it down that while other animals have consciousness, man alone has self-consciousness, that is, he not only feels and thinks, but is aware of himself as feeling and thinking. Man, we know, is capable of this self-consciousness, which is cultivated by his being able to talk about himself as he does about other persons; but it has never been proved that animals, who we know are not apt to mistake their own bodies for anything outside, have no consciousness of themselves. When we study the rules of sign-making and language, we really have some means of contrasting the animals with ourselves. Evidently it is by means of language that the human mind has been able to work out and mark the high abstract ideas we deal with so easily; without words, how could we have reached results of combined and compared thought such as momentum, plurality, righteousness? The great mental gap between us and the animals we study is well measured by the difference between their feeble beginnings in calling one another and knowing when they are called, and man’s capacity for perfect speech. It is not merely that the highest anthropoid apes have no speech; they have not the brain-organisation enabling them to acquire even its rudiments. Man’s power of using a word, or even a gesture, as the symbol of a thought and the means of conversing about it, is one of the points where we most plainly see him parting company with all lower species, and starting on his career of conquest through higher intellectual regions.

In the comparison of man with other animals the standard should naturally be the lowest man, or savage. Put the savage is possessed of human reason and speech, while his brain-power, though it has not of itself raised him to civilization, enables him to receive more or less of the education which transforms him into a civilized man. To show how man may have advanced from savagery to civilization is a reasonable task, worked out to some extent in the later chapters of this volume. But there is no such evidence available for crossing the mental gulf that divides the lowest savage from the highest ape. On the whole, the safest conclusion warranted by facts is that the mental machinery of the lower animals is roughly similar to our own, up to a limit. Beyond this limit the human mind opens out into wide ranges of thought and feeling which the beast-mind shows no sign of approaching. If we consider man’s course of life from birth to death, we see that it is, so to speak, founded on functions which he has in common with lower beings. Man, endowed with instinct and capable of learning by experience, drawn by pleasure and driven by pain, must like a beast maintain his life by food and sleep, must save himself by flight, or fight it out with his foes, must propagate his species and care for the next generation. Upon this lower framework of animal life is raised the wondrous edifice of human language, science, art, and law.