Nervous system.—In this part of the organism we are especially interested in the structure of the brain. Bastian justly remarks, with reference to the brain of apes, that this family possesses many cerebral characteristics in common, by which their close connection with each other may be verified. Distinct stages of development have been observed, which, however, cannot be classified in a consecutive series. Starting from the brains of lemurs, which do not greatly differ from those of rodents, we can advance by means of very distinct transition forms to the more highly developed cerebral hemispheres of the large anthropoid apes, the chimpanzee, the gorilla, and orang-utan.80

Very opposite views prevail among anatomists with regard to the question which species of anthropoids possesses the most highly developed brain. Some regard the chimpanzee’s brain as the simplest, and that of the orang as the most highly developed. In all these apes the lateral halves of the cerebrum, always divided from each other by a deep longitudinal fissure, overlap the cerebellum as far as a minute posterior segment. In this respect I find the brain of the gorilla a little behind the other anthropoids. Up to this time, I have only observed the projection of the cerebellum through the cerebrum in the case of an orang81 (see also Fig. 56). Retzius asserts that the cerebellum of Lapps is incompletely covered, while the covering is generally complete in the case of Slav and Tartar races. In German and Latin races the cerebrum overlaps the cerebellum. In Mongolian, Indian, and Negro races the covering appears to be generally imperfect.

While the ground form of the gorilla brain approximates to a long oval, and in this respect resembles the human brain, the brain of chimpanzees and orangs is of a round-oval form. This is especially the case with the chimpanzee (Fig. 57). In my opinion, the gorilla brain is distinguished from that of the chimpanzee, but not from that of the orang, by its very complex convolutions (Fig. 56).

In the gorilla, chimpanzee, and orang, the island of Reil in the fissure of Sylvius is generally—at least, according to my experience—overlapped by the operculum, although there are instances in which this is not the case. In these three anthropoids, as Bastian justly observes, the fissure of Sylvius is much less horizontal than in man, and occupies a position more like that which it takes in the black sea-cat monkey, the wanderers, and other macacas. In the gorilla its direction is more horizontal than in the two other species of anthropoids. The central fissure, termed fissure of Rolando, is very marked, especially in the chimpanzee (Fig. 57 R); but it may also be easily traced in other species of anthropoids (Fig. 58, II., 56, R). The so-called simian fissure between the parietal and occipital lobes of the cerebrum (Meynart’s elongated external occipital fissure), presented in Fig. 58 s c, is very marked in the chimpanzee (Fig. 57, d). The frontal lobes of the gorilla brain are high, while those of the chimpanzee are short and low. It is said that those of the orang, which are high and short, terminate in a beak-shaped curvature, but this is not invariably the case.

In the anthropoids we have been considering, and also in several of the lower species of apes, there are three other fissures of less importance in addition to those we have mentioned, namely, the fissure parallel to the fissure of Sylvius, and placed behind it, the corpus callosum fissure, placed immediately above the corpus callosum on the inner side of the hemisphere of the cerebrum, and the calcarine fissure (Fissura calcarina) (Fig. 60). The latter ends near the point of junction of the inner and lower surfaces of the posterior division of the hemisphere. The upper temporal convolution, termed by several anatomists Gyrus supramarginalis, is said by Gratiolet to be absent in anthropoids; but Rolleston, Bastian, and myself have all found it well developed82 (Fig. 56, orang, and Fig. 58, gorilla).

Bischoff asserts that the third frontal convolution (Broca’s convolution) is very slightly developed in the chimpanzee, orang, and gibbon. “Its great development in men,” Gewährsmann writes, “constitutes one of the most marked distinctions between the brains of apes and of men.”83 In most of the other species of apes this convolution is altogether absent, but Pansch is justified in the assertion that it is fully developed in anthropoids. I cannot wholly agree with Pansch in his analysis; but I must accept his statement on this point (see the orang, Fig. 59). Gratiolet remarks that the so-called annectant gyri (plis de passage) which serve as a covering or operculum for the posterior lobes in apes, are only superficially apparent in man. In the chimpanzee the upper of those convolutions is absent, while it is large in the orang, and likewise large and undulated in man. In the orang the second annectant gyrus is covered, but this covering is absent in man.84

In considering the inner structure of the brain of these animals, we are first struck by the shortness of the corpus callosum. The soft and thick anterior commissure of the third cerebral ventricle and the thin posterior commissure have also been justly noted. In the lateral ventricles more of the characteristics described in the human brain are absent. The four eminences resemble those of man; nor does the fourth cerebral ventricle present any remarkable differences of form. Neither does the base or lower surface of the brain display any important deviation from the human type. The transverse section of the nerves at their intersection appears to me, however, to be somewhat more oval than is the case in man.

There has recently been an attempt to recognize a pithecoid character, or atavism, in microcephalic men, the smallness of whose heads is allied with a greater or less degree of idiocy. A pithecoid structure of the brain has also been traced in several individuals who are not microcephalous, but subject to pathological affections. We will first consider those who belong to the latter category. Krause examined the brain of an ape-like boy aged seven years and a half, which, as the author remarks, approximated in structure to the pithecoid type, although without displaying microcephalic characteristics. The two cerebral hemispheres were wanting in symmetry; they diverged from each other in the region where the parieto-occipital fissure occurs on the left cerebral hemisphere, and they formed an edge which curved outward and backward so that the cerebellum remained uncovered. On the lower surface of the frontal lobes there was a strongly marked ethmoidal prominence. Neither of the fissures of Sylvius were closed, the left less so than the right; the operculum was only slightly developed; and the island of Reil and its fissures were almost uncovered. This formation is almost the same as that of the brain of anthropoids. The two central fissures of Rolando were close together, or less deeply impressed on the edge of the hemispheres than is normally the case, and forming no joint angle. Large and deeply marked pre-central fissures seemed to represent the central fissures. The intra-parietal fissures, diverging outwardly further than in man, received the parieto-occipital fissure, a structure in conformity with the typical brain of apes. The transverse occipital fissure became in this case a deep fissure like the simian fissure, crossing the occipital lobes, and almost completely dividing them from the parietal lobes. The so-called Fissura calcarina, to which we have referred above, had its origin on the upper surface of the occipital lobe, then joined the parieto-occipital fissure, and went directly into the hippocampal fissure (Fissura hippocampi) on its right side. This abnormal structure is also in conformity with the typical brain of apes. The first occipital convolution is divided from the upper parietal lobes by the parieto-occipital fissure. Gratiolet asserts that this formation occurs in many species of apes. The upper temporal convolution was remarkably reduced on both sides, possessing only an average width of 5 mm. This characteristic reminded Krause of the brain of the chimpanzee. In that animal the upper temporal convolution is always reduced. Krause therefore asks whether some human brains may not possess the typical structure of apes without being microcephalic. The brain we have described scarcely differed from the normal weight; it possessed all the convolutions and fissures, and indeed, the convolutions were perhaps more numerous than in the normal structure, yet it was different in every respect, and approximated in its whole structure to the simian rather than to the human type. Krause adds that if the brain had been placed before him without any intimation of its origin, he should have been quite justified in concluding that it belonged to an anthropoid ape, which stood somewhat nearer to man than the chimpanzee.

It is an unquestionable fact that some human beings, whether children or adults, who are endowed with a defective bodily structure, and who are affected with more or less pronounced physical incapacity and mental weakness, by their appearance, ungainly tricks, and helpless and aimless motions, impress us in the most forcible way with their resemblance to apes. Different degrees of idiocy affect individuals of limited intellect, and remind us of an absolutely brutish condition. Krause describes the “ape-like” boy of seven and a half years old, whom he had examined, as cheerful and inclined to play and dance, but as passionate when he was teased. The child was very supple, fond of climbing, and with great strength in his arms and hands, of which the latter had a horny appearance, reminding him of the hands of a chimpanzee. He could sit on the ground with his legs wide apart. His gait was uncertain, and he was apt to tumble, falling with his knees bent forward and his legs doubled under him; he was fond of hopping, and at such times looked still more like an ape. The great toes of both feet were at an angle to the foot, and thus gave the impression of a prehensile foot. At first Krause supposed that this deviation was produced by the child’s endeavour to supply a broader basis of support for his uncertain gait; but he subsequently changed his opinion, since he did not find the same peculiarity in other children of diseased brain, as, for instance, in those suffering from water on the brain. The boy could say very little, only papa and mamma, and it was long before he could pronounce these words in two syllables; for the most part, he only uttered a sound resembling a grunt. He imitated the barking of a dog, with the sound of rolling r’s. He often stamped his feet and clapped his hands together, making a grunting noise as Krause had observed in the case of gorillas and chimpanzees. The boy was smaller than other children of his age, and had weak eyes; his head was sore, and his forehead narrow. His imitative tendency was strongly marked, and his whole nature and all his movements strikingly resembled those of apes. He had been much neglected by his parents.85

When I was a student at Berlin I had the opportunity of observing a similar being of twelve years old, in what was at that time the Weinbergswege, near the Rosenthaler Gate. This was a boy with a large head, a low retreating forehead, glazed eyes, a morose expression, a thin neck, prominent belly, crooked legs, large hands and feet. The boy was of a slouching appearance, and his gait was unsteady: saliva often dribbled from his wide mouth; and as he walked he held on to the furniture, walls, etc., and often he fell powerless on his side, and so remained in a crouching position. It seemed to give him peculiar pleasure to creep on his hands and knees, and at such times he would stamp with the closed fingers of one or the other hand upon the ground, as if in triumph. This habit, his gait, and the gurgling sound which was all that the boy could utter, constituted the points of his resemblance to apes. All the other conditions of life were those of a being whose mental and physical growth was arrested, and who, although not epileptic, was to a certain extent idiotic. I am ignorant what afterwards became of him.

In the course of a discussion on the instance adduced by Krause, Virchow asks whether the psychological conditions of such a brain are indeed simian. He is convinced that whoever has studied the microcephalic child Margaret Becker (of Bürgel, Hanau) will find that psychologically she had nothing in common with an ape. In her case all the positive faculties and qualities of the ape were wanting; the simian psychology was altogether absent, and there was only the psychology of an imperfectly developed and deficient young child. Every characteristic was human. Virchoff had the child in his room for hours together during a period of two months, and was constantly occupied about her, without observing anything in her nature which reminded him even remotely of the psychological conditions of apes. She was a degraded specimen of humanity, differing in no respect from the human type.86

I also examined Margaret Becker, as well as another microcephalic girl, who was in the Berlin Asylum in the years 1868 and 1869. With respect to the former and more animated being, I have nothing essential to add to the information published by Virchow. Ida X——, the other individual whom I examined at Berlin, was at the time of my researches aged thirteen years and five months. Her figure was slightly made and well proportioned, while her profile reminded me to a modified extent of that of the microcephalic Aztec, and also of the heads represented in ancient sculpture of Mayapan, Palenque, and Copan. I must not omit to say that Ida had light blue eyes and fair, glossy hair. She was altogether impassive; could only utter the syllables da-da; and once betrayed a slight sign of displeasure when the cold metal of the measuring-rod was placed against the inner side of her thigh, for the sake of obtaining the dimensions of the different parts of her body.

Virchow’s information respecting Esther Jacobwitz, of Waschahel, is also extremely interesting. She was a microcephalic girl of the age of fourteen, and a Hungarian Jew by race.87 Virchow remarks that, in his opinion, all Esther’s most striking characteristics presented the strongest contrast to those of apes, since only negative traits have hitherto been established, while all which characterizes the positive development of the psychical life of apes was absent in this case. The same remark applies to Ida X——. Virchow goes on to say that there was undoubtedly something brute-like in the defects in question, but that in order to reproduce the animal in its actual form and nature, so as to show that the microcephalic child was really theromorphic, the positive side of animal life must to some extent be presented to us, and this was absolutely wanting.

Virchow also had the opportunity of examining a pair of twin children, one of whom was quite normally developed, while the other (Karl R——) was microcephalic. This was a very significant case, since two individuals of the same birth were under consideration, so that the question could be asked with greater confidence—Is this atavism, or a morbid condition? From this point of view, it was of special interest to establish the fact that the microcephalic child had, in fact, displayed positive signs of a morbid condition.88

When I go through the accounts collected by C. Vogt of the lives of well-known microcephalic beings,89 I can find nothing which specifically reminds me of the actions and habits of apes, although we have an intimate acquaintance with their ways. These individuals give the general impression of human beings whose bodily and mental development has been arrested. According to Virchow’s experience, all the cerebral disturbances are concentrated in the cerebrum in these microcephalous cases. The anterior portions of the cerebrum are affected to the greatest, and the posterior to the least, extent. Those parts which are developed latest suffer the most, while those which are the first to be developed generally escape disturbance.90

Klebs, Schaaffhausen, and others have sought to show that the mothers of microcephalic children have suffered from severe pains of the uterus during pregnancy. All scientific men consider that spasms of the uterus distinctly affect the development of the brain of the offspring. Flesch thinks it possible that these spasms of the uterus may have something to do with the origin of microcephaly.91 But he also asks whether this morbid condition of the uterus may not have been produced by a previously diseased condition of the offspring. This observer is, moreover, still more inclined to make the influence of the father responsible for the occurrence of microcephaly. In view of the fact that there is much reason to suppose there has been a compression of the uterus, and in default of any better suggestion, Flesch feels justified in looking for a compression which has perhaps resulted from some growth on the ovary. Hence ensues a disturbance, probably inflammatory, of the organ of nutrition.92

Aeby also regards microcephaly, not as an expression of atavism, but as the result of a morbid degeneration. “Microcephalic subjects do not point back to the milestone which man left behind him in hoar antiquity, and it is not through them that the chasm between man and animals can be bridged over, nor even rendered less wide.”

Virchow’s researches led to the following conclusions, which we must here subjoin:—1. There is no species of apes which presents that precise configuration which is found in a microcephalic brain. 2. Psychology offers the strongest arguments against men-apes. 3. The instinctive side of psychical activity, which is almost wholly absent in microcephalic subjects, is very prominent in anthropoids as well as in other animals.93

In addition to these remarks, it may also be observed that among savage races the medicine-men, shamans, sorcerers, rain-doctors, etc., often assume ape-like attitudes in the contortions, leaps, dances, and other gestures which are inseparable from their trade. Owing to their state of excitement, in which they are not always mentally responsible for their acts, this imitation may be often partly or wholly unconscious. It is very common among the inspired Arabs termed Haschasch, who, sometimes as dervishes, sometimes as poets or beast-tamers, roam through the country and extend their wanderings from the interior of Africa to the latticed gates of Dolma Bakhtsche. To them belong also the dancing mendicant monks of Islam, who display their ape-like gesture in the market-places and streets of Bokhara, as well as in the other chief cities of Central Asia. In this case, indeed, many gestures are conventional, and even adopted as the means of stimulating the proposed effects, but at the same time they impress us with the idea that a man under such conditions of life and work involuntarily adopts the gestures of anthropoids. When we see a Zikr, an Islamite rite of worship, accompanied by obligatory howls and contortions of body, we are tempted to imagine ourselves in the midst of a troop of wild apes. And the illusion is still stronger if the performers in the Zikr are black fakirs, dressed as warriors.

The peripheral nervous system of anthropoids has not, up to this time, been analyzed with the completeness we could wish. As far as the observations of Vrolik, Gratiolet, and Alix go, together with my personal experience in this department, no marked distinction can be established between the structure of these organs in anthropoids and those of the nervous system in man.

H. von Ihering has studied the relation of the nervous lumbo-sacral plexus to the vertebral column of men and animals, and has come to the conclusion that there is the most complete agreement between men and animals with respect to the relations of the vertebral column to the peripheral nervous system. According to this author, man, from the anatomical point of view, stands so completely within the class of anthropoids, that the attempt to assign to him any other place in zoology is open to the charge of being biassed by considerations which have nothing to do with facts.94

The organs of the senses in anthropoids do not present any noteworthy points of difference from these organs in man. I have written, but not yet published, a treatise on the eyes of these animals, showing their general agreement with the conditions of the human eye. On the skin of the fingers and toes of anthropoids developed corpuscles may be detected which are connected with the sense of touch.

The vascular system of anthropoids has not up to this time been studied in any exhaustive manner. The heart strongly resembles that organ in man. In the gorilla, the chimpanzee, and the orang the great arterial branches have the same relative conditions as in the human organism. A common origin from one branch of the subclavian artery, and of the right and left carotid arteries, often occurs in the orang and with a certain constancy in the gibbon, so far as we can judge from the researches which have been made up to this time. But we know that this form of deviation from the common type is not altogether rare in man. Bischoff and others have justly maintained that the resemblance to man which is found in these animals in the arrangement of the heart and larger blood-vessels appears to be connected with their mode of life. For although their habits are arboreal, this very fact implies that they are for the most part in an upright position.

The division of the femoral arteries displays a somewhat interesting deviation from the normal human type. High up near the femoral arch an artery, accompanied by veins and a large nerve, diverges from the femoral artery, which extends, together with its accompanying parts, as far as the back of the foot. In the gorilla this branch pierces the sartorius.