CHAPTER IX. Human in Miniature

HUMAN IN MINIATURE

THE BRAIN OF THE CHIMPANZEE

The chimpanzee has a well-established reputation for many sterling qualities. He is a comedian of no mean talent, and often as a buoyant fun maker earns a large salary. He is also famous as an acrobat.

Depending upon his species, the chimpanzee varies in height from four feet to four feet five inches. As a class these apes are spread out over more territory than any of the other great anthropoids. They live in West and Central Equatorial Africa ranging from Gambia in the north as far south as Angola. In colour they are black with thick hair over the entire body, except the brow and face. In some species the scalp is bare, as in the bald-headed chimpanzee. All varieties are powerful but lightly built animals. They possess great strength and agility. In spite of his relatively short stature, the chimpanzee is a dangerous enemy even for the strongest man. His head is flattened in the region of the forehead, which has a thick bony ridge above the eyes. The ridge of the nose is flat. The mouth is large and the lips thick. The ears are especially large and project upward almost as high as the vertex of the head. The lower jaw protrudes considerably. The teeth in general are large and formidable, the canines in particular being prominent. The skin over the face is usually dark, but in some species it is lighter than surrounding areas. This is particularly true in the region of the mouth and nose. The body is short and the abdomen pendulous. The legs are shorter than the arms. The foot is short with a great toe that is thick and opposable. The other toes are united by a web near the base. The arms are long, with finger tips reaching a considerable distance below the knees when the animal stands erect. The hands are broad, the thumb is short, and the fingers webbed near their bases, as in the case of the toes. As is true of the other great anthropoids, the chimpanzee has no tail. The female bears one young at a time, which she carries when passing through the forest and along the ground in the manner characteristic of other apes.

Intelligence of the Chimpanzee

Concerning the habits of the chimpanzee in its native state little is known. Fortunately, many of these animals have been captured when young. Some of them have become noted circus performers, or famous moving-picture actors. A number of them have been studied from the standpoint of their behaviour and psychology. One of the best records of the chimpanzee comes to us as an echo of the Great War. It furnishes another instance of German thoroughness and scientific enterprise.

Some years ago the Prussian Academy of Science established at Teneriffe in the Canary Islands a special station equipped for the study of the great manlike apes. It was here that Professor Köhler found himself during the Great War and here he remained interned with nine chimpanzees for two years. During this time he lived with these animals largely shut off from the rest of the world by the naval blockade. The report of his experience and studies is given in a delightful narrative published both in English and German called The Mentality of Apes. The following descriptions of the chimpanzee are taken from Professor Köhler’s book. In this work his chief purpose was to test the intelligence of the larger manlike apes. To this end it was necessary to devise certain methods which he called “roundabout tests” because they complicated ordinary situations in such a way as to require intelligence on the part of the animal for their solution.

Early in the study one of the most quick-witted chimpanzees in the collection was given the following problem: From the roof of the animals’ playground a basket of bananas was suspended by means of a string passed through an iron ring. The end of this string was tied in a noose and placed over the limb of an old tree at a height of nine feet from the ground. When all was ready, the chimpanzee called “Sultan” was sent out into the playground. He, of course, was familiar with this basket and associated it with feeding time. On entering the enclosure Sultan saw the basket at once and then began to manifest signs of agitation because, contrary to custom, he was all alone in the open. He began at once to show his feelings in true chimpanzee style. Jumping about he expressed his extreme disapproval at being alone by making a thundering noise with his feet against the wall of the ape house. It seemed as if he were calling upon the other chimpanzees to come out and join him. He even tried to get in communication with the other animals by climbing up and looking in at their windows. But all of this was to no avail. Presently he appeared to take a renewed interest in the bananas. He looked up at the basket, and having sized up the situation made for the tree, climbed quickly to the noose, pulled the string until the basket bumped against the roof, released the string, pulled it a second time even more vigorously, until a banana fell to the ground. Sultan then left the tree, but soon ascended once more, now to pull violently upon the string until it broke and the entire basket fell. Immediately he scampered down, took the basket, and went off in a corner to eat the fruit. Thus Sultan, in a comparatively brief time, solved this roundabout problem by obtaining the objective in spite of the obstacles put in his way.

The Chimpanzee’s Use of Implements

Many experiments were made to see how much the chimpanzees make use of implements, but in the main these experiments were not necessary. The chimpanzee, as if by nature, handles many objects in his immediate surroundings in a variety of ways. His powerful hands serve in a most natural manner as a useful link between him and the world of things outside. His feet, although far more than a second pair of hands, may be used in emergencies when the human feet would be quite useless. The jaws and teeth are also serviceable, and are employed as among many African tribes and other primitive people. The handling of everyday objects by the chimpanzee comes almost entirely in the nature of play. Sometimes under the pressure of need it appears that new knowledge acquired from using objects at play will be put to still better use in gaining some desired objective. In the main, however, what the chimpanzee may use in this way is without the slightest idea of immediate gain and serves only to increase the joy of living. Thus jumping with the aid of a stick or pole, invented by one of the brightest chimpanzees, was imitated by all the others as a means of entertainment. Later it was put to more practical use for obtaining food which was suspended above them and out of reach. In order to get this food it was necessary to resort to some means of lifting their body toward the desired goal. In the end the jumping with a stick in play was converted to a sort of pole vaulting by means of which the chimpanzees all acquired a thoroughly businesslike method for getting such food as was out of reach over their heads. These chimps also used straws and twigs as we use spoons. At first this was more or less in play during mealtime, especially after their first thirst had been quenched. Then they liked to amuse themselves by dipping the water up with a straw and sucking the straw. Once some red wine was poured into the drinking water which they shared in common. At the first taste of this new mixture they all paused for a moment and looked at each other; then one of the chimpanzees began to spoon up this wonderful drink with a straw, and all the others immediately followed his example. In learning to use twigs and straws for spoons there was no possibility of imitation. None of the chimpanzees had a chance of seeing a human being use a knife or spoon while eating. The twig or stick was also employed quite deftly in other ways, adding to its usefulness as a table utensil some of the properties of a weapon for the chase. In the summer time a species of ant infests the part of the Canary Islands where these great apes were housed. These ants passed in a wide stream, moving along over the beams, around a wire netting which encircled the playground. The chimpanzee has a great liking for acid fruit, which he prefers to all others. It is no doubt for this reason that he relishes the formic acid in the ants. Usually upon seeing the ants the chimpanzee simply rolled his tongue along a beam over which they were crawling and thus gathered them in to himself. If the wire netting came between him and this coveted delicacy, such a method of capture would not suffice. In consequence, all of the chimpanzees soon learned to use sticks and straws, which they thrust through the wire netting and held in this position until covered by ants. The straws were then withdrawn, and the insects promptly licked off and devoured. This method of capture proved most satisfactory and entertaining. Their attention was entirely absorbed in the process of overcoming the obstacle between them and the delicate morsels which they craved.

Strong Human Resemblances

If a mouse, a lizard, or some small crawling animal entered the playground, the chimpanzees at once became greatly excited. They manifested all of the hunting interest apparent in the human species under like circumstances. There was also evidence of fear and timidity on these occasions, not, however, confined to the female alone. Even the bolder chimpanzees that evinced the greatest hunting interest did not give chase with any creditable show of courage. They manifested caution and hesitation throughout the entire performance. Nearly every movement on the part of the poor quarry was followed by nervous gestures of the chimps. The largest ones hesitated to make a capture by a sudden snatch with the naked hand. It was amusing and almost laughable to see these powerful apes stretch out their hands with the evident intention of catching the prey, with fingers all pointed in anticipation, then suddenly, on the slightest movement of the mouse or lizard, quickly withdraw the hand again. A firm grasp upon one of these little wriggling animals appeared almost as impossible for the chimpanzees as for many people. Despite the great excitement which the presence of invaders occasioned, the little animals would often escape because the chimpanzees lacked that last degree of daring necessary to make a successful capture. Presently they learned to use sticks upon the small intruders of their domain. With these weapons, if the victim did not escape, they would at length dispatch it. This they did in no spirit of cruelty but rather in sheer excitement of the chase.

Professor Köhler took great pains to observe the rapidity with which the chimpanzees adjusted themselves when confronted by new conditions for the first time in their lives. One of the most striking tests of this kind was their introduction to the electric current. It was decided to observe how the chimpanzees would act when they made the acquaintance of this entirely new circumstance. For this purpose one wire from an electric induction coil was attached to a metal basket filled with bananas and suspended from the roof. The other wire from the battery was made fast to a metal netting upon the ground beneath the basket. In a short time all of the chimpanzees became intensely interested in the fruit above their heads. They were particularly eager to reach the bananas. To do so it was necessary for them to stand upon the wire netting on the ground. At first one chimpanzee approached cautiously. Having taken up his position with both feet upon the wire netting, he reached slowly up to the metal basket. This of course immediately made a connection which delivered an electric current through his hand. The reaction of the chimpanzee was astonishingly human. Immediately upon touching the basket he felt the shock of the current and with a cry of dismay bounded off in great surprise. His curiosity, however, was not yet satisfied. He still had a hungry longing for the bananas. Everything about the situation looked thoroughly familiar and innocent to him. He could see no reason why the basket on this occasion should treat him so rudely or why he experienced such an unpleasant sensation in trying to get his food as he had done a hundred times before. Appetite and curiosity finally got the upper hand, and stealing up cautiously he made a second attempt. This time he was less hasty in grasping the basket and spent several moments in hesitating attempts to touch it, drawing his hand back now and again. At length, with a sudden grasp, he reached for the goal, only to receive another shock. In apparent indignation he hopped away in much the same manner as might any human being who had inadvertently touched a hot stove. Nothing would do, however, but that all of the chimpanzees in turn should follow the example of their leader and try to get the bananas away from this strange thing that seemed to be outwitting them. One after another they made their futile attempts until it became a pathetic sight to see them sitting around in a mournful ring, sometimes looking at their hands, sometimes shaking them resentfully, and always gazing wistfully at the inaccessible delicacies. Most of the chimpanzees during this test reacted in a manner which might easily be called human. It was rather impressive to observe that all of their reactions under these conditions were actual counterparts of human behaviour.

Chimpanzee Sports and Nest Making

In handling other objects the chimpanzees showed a strong tendency to develop new habits. After a time they did not confine themselves alone to thrusting and hitting with sticks. They soon began to throw them around. In moments when they were greatly pleased (and chimpanzees have a joyful, buoyant nature) they showed their delight in a new way, especially when very good food was being provided. On such occasions one of them would seize another and shake him violently out of sheer pleasure and approval. Under such provocation a large chimpanzee developed the habit of taking a stick and flinging it forcefully at some comrade in his vicinity. This frequently happened in play also. One female, a remarkable athlete called “Chica,” developed the amusing pastime of stealing up behind her companions as they sat quietly at rest, and from fairly close quarters hurling a stick at them. Immediately she would scurry off, apparently much delighted by the discomfort that she had caused. From throwing sticks it was but a short step to throwing handfuls of sand at one another, and finally stones of varied size and weight. At first their aim was poor, but soon throwing stones became a ruling passion among them, and some of them became dangerously expert, especially the wily Chica. She practised so continuously that she soon acquired great skill and an excellent aim. From this pastime she appeared to derive much satisfaction, whether hurling stones at her fellow apes or at her human associates. Both ape and man acquired such a genuine respect for her ability in this regard that whenever they found her in this mood they quickly retired to safety and permitted the expert marksman to find her amusement on less sensitive targets. All of these hurling activities, which were in the nature of play, might for a few moments determine an exciting stone battle. But the sharpshooting Chica was so obviously superior that the fray was certain to be short lived.

Almost all of the chimpanzees made nests for themselves, even from the earliest infancy onward. In these operations, as might be expected, the full-grown chimpanzee made the best beds. It may not be altogether clear why the adult female was the best chambermaid of all. Her efforts in bed making did in fact show a precision in tidiness that was unequalled by any of the others. Usually in the evening, as the strenuous play of the day subsided, all of the apes began to gather heaps of straw. In the centre of each heap a chimpanzee would sit quietly and begin to twist the ends of the straw together. This work continued all around the edge until a natural nest, not unlike that of the stork, was formed. The younger animals in their nest making were less exact. They seldom made so neat a turning down of the outer edges, but on some occasions, when they apparently took more pains with their handiwork, their movements during the preparation of the nest were exactly like those of the older females. Nests were often made during the day in pure fun, and many different materials, such as string, grass, branches, rags, ropes, and even wire, were collected for this purpose. It was quite evident that in their nest-making activities the younger chimpanzees imitated the actions of the older ones.

Clowning and Masquerade

Objects of many kinds interested these apes. They seemed particularly fond of carrying quite a variety of rubbish about on the body in one way or another. Nearly every day some of the animals began walking around the playground with a piece of rope, a bit of rag, a blade of grass, or a twig upon the shoulders. Some of them if given a bit of metal chain would put it proudly around their necks like a necklace. Bushes and brambles were often carried in considerable quantities spread out over the entire back. In these actions they affected a manner that revealed tendencies familiar to human masquerading in grotesque or fantastic costumes. One of the chimpanzees contracted the habit of carrying around empty preserve cans by grasping the lid of the can between his teeth. All of this occupation was done as diversion or entertainment, from which the chimpanzees derived much visible pleasure. The clowning actions of these apes clearly held the attention of those not actively participating in the performances, and many of them, like little children, attempted to imitate the antics of the leader. When dressed up in these various ways the chimpanzees often displayed an almost impish self-important audacity, strutting about among their companions or advancing upon them in a menacing way. One of the older females, attired for play, would trot around in a circle with several of the smaller animals following closely at her heels. Sometimes the entire company playing in this fashion would march around in a circle, one behind the other. The largest animal would stamp its foot at each step, as though beating time for the parade. The other animals followed suit by an accentuation of the marching movements.

Manufacture and Building

Not only did the chimpanzees acquire many ways for employing objects which they encountered, but some of them actually went one step farther. They manifested a degree of ingenuity in constructing special implements for themselves. The results of this constructive industry, it must be admitted, were relatively simple. On the other hand, there can be no doubt that the chimpanzee does manufacture instruments, in a modest way, which help him to gain his ends. One of the most talented apes learned to fit a small piece of bamboo into the cavity at the end of a larger piece. In this way he built a long bamboo pole, which was especially useful for procuring food hung above his head and out of reach. All of the chimpanzees ultimately developed some degree of constructive or engineering ability. They actually became builders on a small scale. This ability grew out of their learning to use boxes in order to reach objects over their heads. Using one box led to the advantage of piling one box on top of another and thus constructing a tower. They were not all equally expert as builders. As might be expected, the more quick-witted and alert members of the group learned how to build first, and this they did entirely of their own initiative. After they had built a tower of this kind, the long bamboo stick came in handy as a means to bring the suspended banana to the ground. Here two modes of solving a problem were combined--that of building, and that of using the long pole. Building operations soon became a favourite pastime; yet in spite of the fact that they were given every opportunity they never developed an efficient labour organization. However helpful united efforts may have been toward their ultimate aim, the chimpanzees failed to realize the advantages of a mutual aid society. There was doubtless a reason for their lack of intelligence in developing higher efficiency in this respect. Almost invariably their building operations were dictated by a desire to obtain food that was out of their reach. Among the chimpanzees this goal was in no sense a mutual interest. It was a matter of the utmost selfish concern to each chimpanzee. So whatever advantage there might have been in a division of labour, there was never a thought of dividing the spoils. When the chimpanzees gravely assembled in the presence of a basket of food hung up over their heads, they gazed about for proper materials to use as tools in reaching the desired goal. One would bring a pole; another would drag up a box. These were put in position preparatory to constructing a tower. The building would then begin in earnest. When the first stages of construction were complete several of the animals at the same time would show great impatience to clamber up. Each one of them acted as if either he or she were the sole proprietor of the structure. Often, too, the box already in position would be snatched away by some competitive group in the building industry and dragged off to be used in the construction of a rival tower. This would usually result in a wrangle among the architects. In fact, the entire company of builders might come to blows over this infringement of property rights. After the subsidence of these Babel-like controversies the building would be resumed and the structure would continue to grow in height until it became an object of ever-increasing excitement to the assembled workers, each manifesting a keen desire to mount it. In consequence of this highly individualistic competition and due to their restless efforts, the tower would sometimes tumble over and the result of their labours be destroyed. Then it was necessary to begin all over again. Usually in this renewed effort only the more diligent and patient of the chimpanzees adhered to the original purpose. The others became interested in more trivial occupations. Eventually the tower was finished, and the more diligent as well as the more patient of the toilers quietly mounted to the summit of the structure and, either with or without the aid of the pole, obtained the coveted bananas. Sometimes, however, just when the diligent one was ready to reap the just reward of his efforts, some member of the group endowed with unusual athletic prowess rushed up stealthily and with great speed to the top of the tower and seized the prize before the rightful winner had time to protest or retaliate. In all of this building enterprise there is something so fundamentally human, so reminiscent of modern methods, that it seems inaccurate to class these reactions too rigidly in the category of ape behaviour.

Emotions of the Chimpanzee

The chimpanzee, according to Professor Köhler, has a range of expression of emotion even greater than that of the average human being. The chimp shows his feelings by his entire body, not merely by his facial expressions. It is his custom to jump up and down both in joyful anticipation and in anger or annoyance. In extreme despair or disgust, which the animal shows on slight provocation, he has the habit of flinging himself upon his back, rolling wildly to and fro, swinging and waving his arms about his head in a frantic manner not, on the whole, very different from the way in which some non-European races manifest their disappointment and dejection. The chimpanzee is not known to weep, nor does he laugh in quite the human sense of the term. There is something approaching human laughter in his rhythmical gasping and grunting when he is tickled. While quietly watching objects that seem particularly pleasing (and his greatest delight comes from observing little children) the face of the chimpanzee, especially around the mouth, has an expression not unlike a human smile. When perplexed or in doubt, he has a way of scratching the surface of his body, especially the arms, breast, or upper portions of the thigh. It has not been stated that during these moments of perplexity he scratches the head, as is the common human custom. He conveys his meaning not only of emotional distaste but also of definite desires. The expression of his wishes is in large part shown by direct imitation of the actions desired. Thus, when one chimp wishes to be accompanied by another, he gives the latter a nudge and pulls him by the hand. If one chimpanzee wishes to receive bananas from another, he imitates the movement of snatching or grasping accompanied by pleading glances. The summoning of another chimpanzee from a considerable distance is often accompanied by a beckoning that is very human in character. Their many actions in all instances are characteristic enough to be understood by their comrades.

Surgical Interests

The chimpanzee is especially prone to pay close attention to the wounds or injuries received by his fellows. The motive of this attention may scarcely be called mutual aid. The removal of splinters from each other’s hands and feet is a favourite clinical operation. In this pursuit the chimpanzee employs methods usually in vogue among the human laity. Two finger nails are pressed on either side of the splinter, which is thus elevated until it may be caught and removed by the teeth. Professor Köhler himself, once having suffered from such an accident, ventured to allow one of the chimpanzees to remove the splinter from his hand. On perceiving the condition, the chimpanzee’s face at once assumed an expression of eager intensity, and his attention became concentrated in preparation for his surgical efforts. He seized the hand, examined the wound, forced out the splinter with two somewhat powerful squeezes of his finger nails, and then closely examined the hand to be satisfied that his work was well done.

Morals Among Chimpanzees

There is much of interest in the experiences of another distinguished observer, Dr. Charles F. Sonntag, formerly Prosector of the Zoölogical Society of London, who has called attention to the fact that the chimpanzee is said to be filthy in its habits. He observed that many of these animals in captivity do not manifest such traits, nor do they show any tendency toward immoral behaviour as has been claimed. It seems unfortunate even to imply that such a delinquency as immorality exists among chimpanzees or, for that matter, any of the lower mammals. But since the point has been raised, it may be well to recall that morals are of human making. They are designed to modify, to restrain, or to prevent the development of certain animal tendencies which are a human heritage from the great animal kingdom. If the chimpanzee in any of its actions tends to depart from the code of morality established by man in one part of the world or another, this can be no reproach to the ape, since man himself has not yet been completely successful in building up a system of restrictive laws to protect himself from the devastations of his own animal inheritance.

Professor Köhler, from his long studies of the chimpanzees, concluded that these apes manifest intelligent behaviour of a general kind familiar in human beings. Not all of their intelligent acts are similar to human acts, but by means of well-chosen tests the character of intelligent conduct can always be traced in the chimpanzee. These apes differ among themselves just as much as people do, in their mentality and intelligence. Some of them may be mentally deficient, just as there are mentally deficient human beings. One remark of Professor Köhler’s is a keen social criticism with a wide application to life in general. He maintains that the tests designed for the chimpanzee serve two purposes: First, they determine the intelligence of the apes; and, second, they test the intelligence of the examiner. This is eminently true in all intellectual contacts between human beings. It is a fact that the chimpanzees stand out among all other animals in their form, in their actions, and in their understanding. In these respects they come much closer to the human standard than any other ape, with the possible exception of the gorilla. All of these observations agree well with the theory of evolution, and in particular with the close relations existing between the growth of intelligence and the development of the brain.

Many other chimpanzees have been studied from time to time. The conclusions drawn from them have been closely similar to those already cited. Romanes some years ago studied the trained chimpanzee, Sally, which was famous for her high degree of intelligence. Under training this animal acquired the ability to count. She could draw a number of straws to six or seven, and upon request would indicate with straws the exact number she had been instructed to show. This achievement, in combination with many other extraordinary performances, reveals certain striking likenesses to man, particularly as to the degree of the chimpanzee’s power to learn.

The Chimpanzee’s Social Traits

Others besides Professor Köhler are willing to give the chimpanzee credit for unusual good-fellowship. All admit that he is a most friendly creature. Often an affectionate attachment exists between him and his owner or keeper. He is never loath to indulge in his clowning performances to please and entertain his human friends. His actions on these occasions have doubtless been the models for the ludicrous mimicry of olden times now generally referred to as “aping.” In many of the army encampments in Africa, monkeys and apes have been the much-prized pets of the officers. It was not uncommon to find among these pets the highly sociable chimpanzee. Frequently the officers manifested much zeal and interest in training their charges and felt a real pride in exhibiting them. Sometimes on gala occasions these simian pets occupied places at the table beside their owners. They partook in most approved style both of food and of drink. Not a few of them have shown a distinctly human characteristic in their strong liking for intoxicating liquors. The chimpanzee has always had a decided penchant in this direction. At mess dinners and on other occasions he not only manifested a keen liking for good wines but took his share with the rest. Often he, like his human companions, rose to hilarious heights. Often, too, it was necessary to lead him off to bed in such a deplorable condition that he would appear next morning with a shaky hand on his brow and that sad expression which plainly told the consequences of festive revelry. One of these chimpanzees had a particular fondness for afternoon tea and would join the officers’ group at this time as a matter of course. His manners were altogether agreeable. He acquired all of the airs essential to such occasions even to certain banal chatterings.

In Prophecy of the Human Brain

If doubts should remain concerning the superior and almost manlike capacities of the chimpanzee, these may be soon put at rest by inspection of his brain. In this organ there are indications of the means by which the chimpanzee has acquired his new and extensive powers of learning, his greater understanding, his higher capacity for adjustments to life, and his many reactions which are so nearly human.

Every sense department in the superbrain has shown pronounced improvements. A survey of the chimpanzee’s brain shows it to be a mechanism better organized for the purposes of efficient output than that of other apes and monkeys. It is a larger brain. It also has a greater richness in grooves and convolutions showing that its capacity for developing brain power has been much increased. The groove of Sylvius has been tipped backward in consequence of expansions in the department of hearing and the department of body and contact senses. In the department of hearing (the temporal lobe) the convolutions are more complex than in any other lower apes or monkeys. In fact, the entire pattern of coil arrangement in this part of the superbrain is similar to that seen in man. It has, perhaps, a simpler design, but the essential features of the pattern may all be identified. In the department of sight the same principle of expansion has been at work. The convolutions in the occipital lobe have increased both in number and complexity of arrangement. There are more grooves and more convolutions in this region than we have yet encountered. Such also is the case in the department for body and contact senses (the parietal lobe), in which the grooves and convolutions manifest an arrangement identical to that of man. The lesser brain, lying as it does tucked away beneath the occipital pole of the superbrain, also shows marked increase in size, so that the subsidiary department essential to postures of the limbs and body, and also to balance, has kept pace with the superbrain. Appraised on the value of its great working departments, a brain like this reveals the manner in which progressive development has advanced.

The organization for transacting the functions of hearing has been greatly improved, if we judge by the enlargement of the temporal lobe. Furthermore, it appears that certain sub-departments for handling these transactions have been established. They doubtless have to do with a better filing system for auditory impressions and especially for correlating the impressions of things heard with similar records of things seen. This method of cross reference produces a better understanding of all objects encountered in the surroundings. A practical illustration may assist in visualizing the manner in which such associations operate. If in their home life the chimpanzees are suddenly startled by the report of a gun, which they have never heard before, the entire family may be greatly perturbed by the harsh and unfamiliar sound. The sound alone might be startling and disagreeable, but the sound cross referenced by the sight of the hunter and gun comes to mean peril. Instances of this kind might be multiplied to show how essential to success in life this system of cross reference is. In fact, it is the amplification of this system that underlies our progress as individuals or as a race. The structural signs of this progress are to be found in the region of the brain that we have been discussing. We may recognize them in the increased number of convolutions which provide for better development of brain power. Equally pronounced are the advances that have taken place in the organization of body and contact senses. This department lies immediately above the Sylvian groove in the parietal lobe. It receives all communications transmitted from the outside world by the sense of touch and by the various movements of the body. The convolutions in this region indicate a highly organized department which we might expect in view of the remarkable performances of the chimpanzee. Walking a tight rope, eating his food with a certain degree of good manners, drilling to music, or driving an automobile, the chimpanzee clearly demonstrates how expert he has become in the use of his hands and feet. His cleverness depends upon his ability to sense the things he touches and to appreciate the finest grades of motion made by his arms and legs. In addition to this high degree of sensing in his hands, he has also acquired greater capacity for appreciating movements and postures of his entire body. Unless the chimpanzee had this expanded department for body and touch senses, it would be impossible for him to learn many of the performances which he does so skillfully. He also would be unable to apply this skill under the direction of his masters or according to the dictates of his own wishes. It is not difficult to understand, therefore, why all the great departments of the senses have increased so much in size in the chimpanzee. Obviously, by amplifying and refining the raw materials received as sense impressions, the output seen in the chimpanzee’s behaviour has been correspondingly amplified and extended. The significance of growth in the parietal, the occipital, and the temporal lobes in this light becomes clear.

One important detail in the superbrain of the chimpanzee we have not yet considered. It will be recalled that the central groove is one of the salient landmarks in the brain. Its outstanding importance arises from the fact that it is the boundary line of the frontal lobe. All of the territory lying in front of this groove represents the last acquired department of the superbrain, the one having the highest authority. It is here that all of the highest brain functions are located. Judgment and reason are included in this list. But to these should be added the ability to profit by experience in the better guidance of life, the upbuilding of personality, and the proper adjustment in all courses of action requiring initiative, insight, restraint, and self-control; and, finally, recognition of responsibility and appreciation of opportunity.

The frontal territory in the chimpanzee is more extensive than in the orang or any other of the lower apes. It shows an additional amount of convolution. The frontal coils for producing the brain power of this highest department have attained a development not far below that of man. The counterpart of each human convolution is present, the only difference being that each individual convolution in the chimpanzee is less complex than in man. These facts about the frontal lobe, which we must regard as the permanent headquarters of the chief executive of the superbrain, are in harmony with what Professor Köhler and other students of animal psychology have told us about the chimpanzee’s intelligence. Man’s frontal lobe is a highly complex facsimile of the chimpanzee’s, just as human intelligence is a more complex development of the higher mental powers.

These improvements in the superbrain are borne out by both the bridge and the pyramid. The bridge, recognized as a reliable index of intelligence, has the value of .400 in the chimpanzee, a rating much above the orang or any of the lower apes already considered. The pyramid also shows a corresponding increase, having a value of .172, and thus indicating a greater development in skilled acts and in the voluntary control over the actions of the body. These two structures show that the superbrain has, in fact, become a more efficient governor for the guidance of a larger, a more complex, and a more effective machine. Every detail in the brain of chimpanzee clearly demonstrates the marked advance that has been made in the steady upward climb. We are able to identify all of the chief features characteristic of the human brain.