Physically, the chimpanzee, as we have seen, closely resembles man, but there are certain points that have not been mentioned in which he differs from him, also from other apes. We may here take note of a few of those points.

The model and structure of the ear of this ape are somewhat the same as those of man, but the organ is larger in size, and thinner in proportion. It is very sensitive to sound, but dull to the touch, indicating that the surface is not well provided with nerves. He cannot move it as other animals move theirs by the use of the muscles at its base, but, like the human ear, it is quite fixed and helpless in this respect.

The hand of the chimpanzee is long and narrow. The finger bones are longer, in proportion to their size, than those of the human hand, and slightly more curved in the plane of the digits. One thing peculiar in the hand of the chimpanzee, is that the tendons inside of the hand, which are called the flexors, and designed to close the fingers, are shorter than the line of the bones, and on this account the fingers of the ape are always held in a curve, so that he cannot possibly straighten them into a line. This is probably due to the habit of climbing in which he indulges to a great extent; also to the practice of hanging by the hands. In making his way through the bush, he often swings from bough to bough by the arms alone, and sometimes suspends himself by one arm, while he uses the other to pluck and eat fruit. This characteristic is transmitted to the young, and is found in the first stages of infancy. The thumb is not truly opposable, but is inclined to close towards the palm of the hand. It is of little use to him. His nails are thick, dark in colour, and not so flat as those of man.

Instead of having the great toe in line with the others, it projects at an angle from the side of the foot, something after the manner of the human thumb. The foot itself is flexible, and has great prehensile power. In climbing, and in many other ways, it is used as a hand. The tendons in the sole of the foot are equal in length to the line of the bones, and the digits of the foot can be straightened, but both members are inclined to curve into an arch in the line of the first and second digits.

His habit of walking is peculiar. The greater part of the weight is borne upon the legs. The sole of the foot is placed almost flat on the ground, but the pressure is greatest along the outer edge of it, in the line of the last digit. This is easily noticed where he walks through plastic ground. In the act of walking he always uses the hands, but does not place the palm on the ground; he uses the backs of the fingers instead, sometimes only the first joints are placed on the ground, resting on the nails; at other times the first and second joints are used, while at others the backs of all the fingers from the knuckles to the nails serve as a base for the arm. The integument on these parts is not callous, like that of the palm; the colour pigment is distributed the same as on other exposed parts of the body, which shows that the weight of the body is not borne on the fore limbs, as it is in the case of a true quadruped, but indicates that the hand is only used to balance the body and shift the weight from foot to foot, while in the act of walking. The weight is not equally distributed between the hands and the feet.

His waddling gait is caused by his short legs, stooping habit and heavy body. All bipeds with stout bodies and short legs are predisposed to a waddling motion, which is due to the wide angle between the weight and the changing centre of gravity.

The chimpanzee is neither a true quadruped, nor a true biped, but combines the habits of both. It appears to be a transition state from the former to the latter, and a vestige of this habit is still to be found in man, whose arms alternate in motion with his legs in the act of walking, which suggests the idea that he may, at some time, have had a similar habit of locomotion. Such a fact does not show that he was ever an ape, but it does point to the belief that he has once occupied a like horizon in nature to that now occupied by the ape, and that having emerged from it, he still retains traces of the habit.

This peculiarity is still more easily observed in children than in adults. In early infancy all children are inclined to be bow-legged, and in their first efforts at walking, invariably press most of their weight on the outer edge of the foot, and curve the toes inward, as if to grasp the surface on which the foot is placed. The instinct to prehension cannot be mistaken; it differs in degree in different races, and is vastly more pronounced in negro than in white infants.

There is another peculiar feature in the walk of the chimpanzee. The motion of the arms and legs do not alternate with the same degree of regularity that they do in man or quadrupeds. This ape uses his arms more like crutches. They are moved forward, not quite, but almost at the same instant, and the motion of the legs is not at equal intervals. To be more explicit: the hands are placed almost opposite each other; the right foot is advanced about three times its length; the left foot placed about one length in front of it; the arms are again moved; the right foot again advanced about three lengths forward of the left; and the left again brought about one length in front of it. The same animal does not always use the same foot to make the long stride. It will be seen by this that each foot moves through the same space, and that in a line, the tracks of either foot are the same distance apart, but the distance from the track of the right foot to that of the left is about three times as great as the distance from the track of the left foot to that of the right; or the reverse may be the case. The distance from the track of either foot to the succeeding track of the other, is never the same between the right and left tracks, except where the animal is walking at great leisure.

There is, perhaps, no animal more awkward than the chimpanzee, when he attempts to run. He sometimes swings his body with such force between his arms as to lose his balance, and falls backward on the ground. I have often seen him do this, and when he would right himself again, would be half his length farther backward than forward of his starting-point.

The chimpanzee is doubtless a better climber than the gorilla. He finds much of his food in trees, but is not arboreal in habit in the proper sense of that term. To be arboreal, the animal must sleep in trees or on a perch, but the chimpanzee cannot do so. He sleeps the same as a human being does. He lies down on the back or side, and, as a rule, uses his arms for a pillow. I do not believe it possible for him to sleep on a perch. He may sometimes doze in that way, but the grasp of his foot is only brought into use when he is conscious of it. I have often known Moses to climb down from the trees and lie upon the ground to take a nap. I never even saw him so much as doze in any other position.

I may here call attention to one fact concerning the arboreal habit. There appears to be a rule to which this habit conforms. Among apes and monkeys the habit is in keeping with the size of the animal. The largest monkeys, as a rule, are only found among the lowest trees, and the smaller monkeys among the taller trees. It is a rare thing ever to see a large monkey in the top of a tall tree. He may venture there for food or to make his escape, but it is not his proper element. This same rule appears to hold good among the apes themselves. The gibbon has this habit in a more pronounced degree than any other true ape. The orang appears to be next; the chimpanzee then comes in for a third place, and the gorilla last. It must not be understood that all of these apes do not frequently climb, even to the tops of the highest trees; but that is not their normal mode of life any more than the top of a mast is the proper place on a ship for a sailor.

The chimpanzee is nomadic in habit, and, like the gorilla, seldom or never passes two nights in the same spot. As to his building huts or nests in trees or elsewhere, I am not prepared to believe that he ever does so. I hunted in vain, for months, and made diligent inquiry in several tribes, but failed to find a specimen of any kind of shelter built by an ape. I do not assert that it is absolutely untrue, but I have never been able to obtain any evidence, except the statement of the natives that it was true. On the contrary, certain facts point to the opposite belief. If the ape built him a permanent home the natives would soon discover it, and there would be no difficulty in having it pointed out. If he built a new one every night, however rude and primitive it might be there would be so many of them in the forest that there would be no difficulty in finding them. The nomadic habit plainly shows that he does not build the former kind, and the utter absence of them shows that he does not build the latter kind, and the whole story appears to be without foundation.

In addition to these facts, one thing to be noticed is that few or none of the mammals of the tropics ever build any kind of a home. Even the animals that have the habit of burrowing in other climates, do not appear to do so in the tropics. This is due, no doubt, to the warm climate, in which they are not in need of shelter. Of course birds, and other oviperous animals, build nests, as they do elsewhere.

The longevity of these apes is largely a matter of conjecture, but from a cursory study of their dentition and other factors of their development, it appears that the male reaches the adult stage at an age ranging from nine to eleven years, while the female matures at six or seven. These appear to be the periods at which they pass from the state of adolescence. Some of them live to be perhaps forty years of age, or upwards, but the average of life is doubtless not more than twenty-two or twenty-three years. The average of life is more uniform with them than with man. These figures are not mere guesswork, but are deduced from reliable data.

The period of gestation in both these apes is a matter that cannot be stated with certainty. Some of the natives say that it is nine months, while others believe that it is seven months or less, and there are some facts to support both of these claims, but nothing quite conclusive. The sum of the evidence that I could find rather pointed to a term of three months or thereabouts as the true period. During the months of February and March the male gorillas are vociferous in their screaming, the young adults separate from the families, and some other things indicate that this is the season of pairing and breeding. Such may not be the case, but the inference is well-founded. It is quite certain that the season of bearing the young is from the beginning of May to the end of June. It is about this time that the dry season begins and continues for four months. It would appear that nature has selected this period of the year because it is more favourable for rearing the young. During this season food is more abundant and can be secured with less effort. The lowlands are drier, and this enables the mother to retire to the dense jungle with her young, where she is less exposed to danger than she would be in the more open forest.

It is not certain whether the periods are the same with both apes or not, and native reports differ on this point, but it is probable that they are the same.

From a social point of view, the chimpanzee appears to be of a little higher caste than other animals. In his marital ideas he is polygamous, but is, in a certain degree, loyal to his family. The paternal instinct is a trifle more refined in him than in most other animals. He seems to appreciate the relationship of parent and child more, and retain it longer than others do. Most male animals discard their young, and become estranged to them at a very early age; but the chimpanzee keeps his children with him until they are old enough to go away and rear a family of their own.

The family of the chimpanzee frequently consists of three or four wives and ten or twelve children, with one adult male; but there are cases known in which two or three elderly males have been seen in the same family, but they appear to have their own wives and children. In such an event, however, there seems to be one who is supreme. This fact suggests the idea that among them a form of patriarchal government prevails. The wives and children do not appear to question the authority of the patriarch, or to rebel against it. The male parent often plays with his children, and appears to be fond of them.

There is one universal error that I desire here to correct. It is the common idea that animals are so strongly possessed of the parental instinct that they nobly sacrifice their own lives in defence of their young. I do not wish to dispel any belief that tends to dignify or ennoble animals, for I am their special friend and champion; but truth demands that we qualify this statement. It is quite true that many have lost their lives in such acts of defence, but it was not a voluntary sacrifice. It was not alone in the defence of their young, but in many cases it was in self-defence. In others, it was from a lack of judgment. These apes have often been frightened away from their young, and the latter captured while the parents were fleeing from the scene. This may have been the result of sagacity rather than of depravity, but the parental instinct in both sexes, in many instances, has failed to restrain them from flight. If it be a foe that appears to come within the measure of their own power, they will certainly defend their young, and this sometimes results in the loss of their own lives; but if it be one of such formidable aspect as to appear quite invincible, the parents leave the young to their fate. This is true of many other animals, including man.

I have no desire to detract from the heroic quality of this instinct, or to dim the glory it sheds upon noble deeds ascribed to it; but the fact that a parent incurs the risk of its own life in the defence of its young, is not a true test of its strength or quality. It is only in the few isolated cases of a voluntary sacrifice of the parent, foreknowing the result, that it can be said the act was due to the instinct. In most cases it is under the belief in its ability to rescue the one in danger, but the parent is not wholly aware of its own danger.

I doubt if any animal except man ever deliberately offered its own life as a ransom for that of another, and such instances in human history are so rare as to immortalise the actor.

To whatever extent the instinct may be found, it is much stronger in the female than in the male, and it appears to be stronger in domestic animals than in wild ones. To what extent this is due to their contact with man, it is difficult to say. The germ may be inherent, but it certainly yields to culture.

The fact of the ape deserting its offspring under certain conditions, may be taken as an evidence of its superior intelligence and its appreciation of life and danger, rather than a low, brutish impulse. It is the exercise of superior judgment that causes man to act with more prudence than other animals. It does not detract from his nobleness.

Within the family circle of the chimpanzee the father is supreme; but he does not degrade his royalty by being a tyrant. Each member of the family seems to have certain rights that are not impugned by others. For example, possession is the right of ownership. When one ape procures a certain article of food, the others do not try to dispossess it. It is from this source, doubtless, that man inherits the idea of private ownership. It is the same principle amplified by which nations hold the right of territory, but nations often violate this right, and so do chimpanzees when not held in check by something more potent than a sense of justice. With all due respect, I do not think the ape abuses the right by urging his claim beyond his real needs, while nations sometimes do.

When a member of a family of apes is ill, the others are quite conscious of it, and evince a certain amount of solicitude. Their conduct indicates that they have, in a small degree, the passion of sympathy, but the emotion is feeble and wavering. So far as I know, they do not essay any treatment, except to soothe and comfort the sufferer. They surely have some definite idea of what death is, and I have reason to believe that they have a name for it. They do not readily abandon their sick, but when one of them is unable to travel with the band, the others rove about for some days, within call of it, but do not minister to its wants.

It is said, if one of them is wounded, the others will rescue it if possible, and convey it to a place of safety; but I cannot vouch for this, as such an incident has never come within my own experience.

One of the most remarkable of all the social habits of the chimpanzee, is the kanjo, as it is called in the native tongue. The word does not mean "dance" in the sense of saltatory gyrations, but implies more the idea of "carnival." It is believed that more than one family takes part in these festivities.

Here and there in the jungle is found a small spot of sonorous earth. It is irregular in shape, but is about two feet across. The surface is of clay, and is artificial. It is superimposed upon a kind of peat bed, which, being very porous, acts as a resonance cavity, and intensifies the sound. This constitutes a kind of drum. It yields rather a dead sound, but of considerable volume.

This queer drum is made by chimpanzees, who secure the clay along the bank of some stream in the vicinity. They carry it by hand, and deposit it while in a plastic state, spread it over the place selected, and let it dry. I have, in my possession, a part of one that I brought home with me from the Nkami forest. It shows the finger-prints of the apes, which were impressed in it while the mud was yet soft.

After the drum is quite dry, the chimpanzees assemble by night in great numbers, and the carnival begins. One or two will beat violently on this dry clay, while others jump up and down in a wild and grotesque manner. Some of them utter long, rolling sounds, as if trying to sing. When one tires of beating the drum, another relieves him, and the festivities continue in this fashion for hours.

I know of nothing like this in the social economy of any other animal, but what it signifies, or what its origin was, is quite beyond my knowledge. It appears probable that they do not indulge in this kanjo in all parts of their domain, nor do they occur at regular intervals.

The chimpanzee is averse to solitude. He is fond of the society of man, and is easily domesticated. If allowed to go at liberty, he is well-disposed, and is strongly attached to man, but if confined, he becomes vicious and ill-tempered. All animals, including man, have the same tendency.

Mentally the chimpanzee occupies a high plane within his own sphere of life, but within those limits the faculties of the mind are not called into frequent exercise, and therefore they are not so active as they are in man.

It is difficult to compare the mental status of the ape to that of man, because there is no common basis upon which the two rest. Their modes of life are so unlike, as to afford no common unit of measure. Their faculties are developed along different lines. The two have but few problems in common to solve. While the scope of the human mind is vastly wider than that of the ape, it does not follow that it can act with more precision in all things. There are, perhaps, instances in which the mind of the ape excels that of man, by reason of its adaptation to certain conditions. It is not a safe and infallible guide to measure all things by the standard of man's opinion of himself. It is quite true that, by such a unit of measure, the comparison is much in favour of the man, but the conclusion is neither just nor adequate.

It is a problem of great interest, however, to compare them in this manner, and the result would indicate that a fair specimen of the ape is in about the same mental horizon as a child of one year old. But if the operation were reversed, and man were placed under the natural conditions of the ape, the comparison would be much less in his favour. There is no common mental unit between them.

The chimpanzee exercises the faculty of reason with a fair degree of precision, on problems that concern his own comfort or safety. He is quick to interpret motives, to discern intents, and is a rare judge of character. He is inquisitive, but not so imitative as monkeys are. He is more observant of the relations of cause and effect, and in his actions he is controlled by more definite motives. He is docile, and quickly learns anything that lies within the range of his own mental plane.

The opinion has long prevailed that these apes subsist upon a vegetable diet, but such is not in anywise the case. In this respect their habits are the same as those of man, except that the latter has learned to cook his food, while the former eats his raw.

Their natural tastes are much diversified, and they are not all equally fond of the same articles of food. Most of them are partial to the wild mango, which grows in abundance in certain localities in the forest, and is often available when other kinds of food are scarce. It thus becomes, as it were, a staple article of food. There are many kinds of nuts to be found in their domain, but the oil palm nut appears to be a favourite. They also eat the kola nut, when it is to be had. Several kinds of small fruits and berries also form a part of their diet. They eat the stalks of some plants, the tender buds of others, and the tendrils of certain vines, the names of which I do not know. Most of the fruits and plants that are relished by them are either acidulous or bitter in taste, and they are not especially fond of sweet fruits, if they can get those having the flavours mentioned. They eat bananas, pine-apples, and other sweet fruits, but not from choice. Most of them appear to prefer a lime to an orange, a plantain to a banana, or a kola nut to a sweet mango, but in captivity they acquire a taste for sweet foods of all kinds.

In addition to these articles they devour birds, lizards, and small rodents. They rob the birds of their eggs and their young. They make havoc on many kinds of large insects. Those that I have owned were fond of cooked meats and salt fish, either raw or cooked.