Chapter III (4)

The gastrocnemius, which is easily separable into two heads, and the peroneal muscles have not the same relative width in anthropoids and man, since in the former case the calf of the lower limb is small, and it lacks the pleasing roundness which characterizes this part of the human structure. These muscles, especially in the orang and gibbon, appear to take a lateral direction. The Tendo Achillis is present, but it has not the prominent development in height and width which we observe in man. The long extensor, flexor, and tibial muscles are in all cases fully developed. The peroneus tertius, as it is termed, although it should only be regarded as a part of the extensor longus digitorum, is absent in anthropoids.[74] I myself am not disposed, with Huxley, Bischoff, and others, to regard this muscle as an abductor. Brühl perceived in a chimpanzee a fourth rudimentary peroneal muscle (_Musculus peroneus intermedius_), extending between the peroneus and the little toe, a muscle sometimes found in man, and which I have myself only observed in one adult chimpanzee. In the gorilla and the chimpanzee the extensor longus digitorum passes through a remarkably strong transverse ligament, formed of fibrous cartilage, which covers the tarsus. It acts upon the four outer toes (Fig. 55). Brühl has described the characteristic contraction and extension of the tendons of the long and short extensors of the toes in the chimpanzee, but I have myself found some difficulty in producing this action. In Fig. 55 I have endeavoured to represent this condition in the most natural way. The extensor proprius pollicis is in all cases developed. The extensor brevis digitorum produces a large, oblique belly for the great toe (Fig. 55). In the gorilla there is for the great toe an abductor, a bicipital flexor, an adductor, and an opponens (comp. Fig. 54).

From the extensor brevis digitorum the belly for the great toe rises with a certain independence. On the right foot of a chimpanzee I observed a fifth belly of this muscle, going to the little toe (Fig. 55). As my illustration is taken from this specimen, I have represented the foot with, or in spite of, this interesting anomaly, which, as we know, sometimes occurs in man.

Fig. 54.--Muscular system of the human foot. 1, Tibialis anticus
and extensor proprius pollicis. 2, Extensor longus digitorum.
3, Tendon of peroneus tertius. 4, 5, Peroneus longus and
peroneus brevis. 4′, 5′, Tendons of the same. 6, 7, Tendons of
the extensor longus and extensor brevis digitorum.
]

The flexor brevis digitorum displays perforated tendons, belonging to the second and third toes. The flexor longus digitorum displays perforated tendons for the fourth and fifth toes. The flexor longus pollicis divides into two tendons, one of which goes into the toe itself, while the other is connected with the flexor longus digitorum, and displays perforated tendons for the third and fourth toes, while the perforated tendons of the second and fifth toes have their origin in the other flexor.

Fig. 55.--Muscles on the upper side of chimpanzee’s foot. 1.
Tibialis anticus muscle. 2, Extensor proprius pollicis. 3,
Extensor communis digitorum. 4, 5, Peroneus brevis and peroneus
longus. 6, Tendon Achilles. 7, Extensor brevis digitorum. 8,
Slip of the same for great toe. 9, First dorsal inter-osseous
muscle. 10, Adductor pollicis. 11, Abductor minimi digiti.
]

In the gorilla the lumbricales muscles of the foot are powerful. The first inter-osseous muscle is likewise well developed and bicipital. There is a short flexor and an abductor for the little toe. I have not yet been able to assure myself of the existence of an opponens for that toe. In the chimpanzee the muscular system of the great and little toe does not essentially differ from that which we have described in the gorilla. The flexor brevis digitorum forms the perforated tendons of the second and third toes. The flexor longus digitorum provides the fourth and fifth toes with perforated, and the second and fifth toes with perforating, tendons, while those which belong to the third and fourth toes have their origin in the flexor longus pollicis. As in the gorilla, the latter muscle produces a fibrous investment for the tendons of the flexor longus digitorum. In the orang there is an abductor of the great toe, a very slightly developed opponens, a short bicipital flexor, and an adductor. One of the long flexors of the toes appears to represent the flexor longus pollicis in man. It provides the second and fifth toes with perforating tendons, while those of the third and fourth toes have their origin in the other flexor longus digitorum. There is no long flexor tendon on the great toe. The perforated tendons in this case generally belong to the short flexor muscle. In addition to the perforated tendons of the fourth toe, there is the long flexor already described.

In a gibbon’s great toe I observed an abductor, a short bicipital flexor, and a slightly developed opponens, to which a wide fan-shaped adductor is attached. The first dorsal inter-osseous muscle is, as in the same animal’s hand (Fig. 53), attached to the first phalanx of the second toe. The flexor longus digitorum provides the third and fourth toes with perforating tendons, and also gives off a tendon for the great toe. On the little toe there is a remarkably slender perforating tendon. While the first of the two long flexors represents the human flexor longus pollicis, the flexor longus digitorum is in this instance limited to the little toe. In the gibbon, as well as in the orang, the gorilla, and the chimpanzee, the two muscles are connected together by an aponeurosis. It may be here mentioned that in the human foot the flexor longus pollicis occasionally gives off a flexor for the second and even for the third toes. In the gibbon, as Bischoff justly observes, a muscle covers the flexor longus digitorum, which is still undivided, but already enlarged. From this muscle perforated tendons issue for the third and fourth toes. The second toe is provided with such a tendon from the flexor brevis digitorum. The muscle we have mentioned seems to represent the Quadratus plantæ, which is often developed in the other anthropoids, although only to a slight extent. With respect to the muscles of the small toe of the orang and gibbon, I need only say that in the latter species the opponens seems to be absent (Fig. 55).

It will be seen from the foregoing account that, in spite of several apparently important peculiarities, in spite of great and manifold variations which are established, even although our authorities do not always agree together, the muscular system of anthropoids is on the whole very like that of man. It displays, especially in the lower limbs, peculiarities of structure which render them capable of walking in an upright position, and others again which they have in common with the lower animals, but on the whole the anthropoid characteristics of the muscular system of these animals are predominant.

The digestive system of anthropoids likewise affords interesting points of comparison. The cavity of the mouth is, as we have seen, bordered by large and flexible lips. The mucous membrane of the mouth and the gums are flesh-coloured; they assume a darker colour in older animals, and are then sometimes marked with spots of a bluish or brownish grey. Ehlers describes, as a peculiarity in the mucous membrane of the mouths of the gorilla and chimpanzee, that there are what he calls buccal folds, which pass on both sides from the fore surface of the upper and lower jaw into the mucous membrane of the cheeks, and are of the height of the canine teeth.[75] I have myself only observed these folds in the gorilla, of which an illustration is given in Fig. 3, and not in any other specimen. I have observed scarcely any indications of these folds in other anthropoids, and then only of such a doubtful nature that I am not disposed to regard the circumstance as of any special significance. A small band on the upper and lower lips, sometimes only slightly developed, but always perceptible, is present in all anthropoids.

The tongue is small, and not provided at its base with several great concave follicles as in man; these are at least only faintly represented, and not easy to observe. Around them there rise pock-like, tufted warts, very close together, which in an aged gorilla are apt to become hard and horny. These are also prominent between the follicles of the tonsils. The circumvallate papillæ of the tongue are less numerous than in man, and often, especially in the chimpanzee, they take the form of a cross, or of the letter T, or in the gorilla of a V.

The uvula and palate present no special variation from the human type. On the hard palate there are a number of folds, or rather swellings, which extend laterally from the central suture of the palate, towards the row of teeth in the upper jaw; these are sometimes simple, sometimes complex, and vary in their details in individual cases. They are particularly marked in the adult chimpanzee, and are also very apparent in the gibbon, and they are arranged with a somewhat ornamental regularity. These inequalities are not altogether insignificant in the human palate, but this subject has not been much studied since Gegenbaur directed the attention of scientific men to them, and special light has been thrown upon it by Bischoff and Ehlers, as far as anthropoids are concerned.

The teeth afford us important material for comparison. In the case of anthropoids the formula for the teeth of the slender-nosed or Old-World apes (_Catarrhina_) will generally apply: _i_ 2/2 _c_ 1/1 _p_ 2/2 _m_ 3/3. The following is the formula for the milk-teeth: _i_ 2/2 _c_ 1/1 _m_ 2/2. Magitot and Giglioli[76] have shown that the milk-teeth are cut in the same order as those of man--first, the lower; second, the upper incisor teeth; third, the front pre-molars; fourth, the back pre-molars; fifth, the canine teeth. According to the same authors, the permanent teeth are cut in the following order:--first, the first molar teeth; second, the lower, and then the upper incisor teeth; third, the pre-molars; fourth, the canine teeth; fifth, the second molar teeth; sixth, the third molar teeth. In the skull of a male gorilla, Giglioli found that the permanent canine teeth were cut almost simultaneously with the third molar teeth, and after the appearance of the second molar teeth. The cutting of the canine teeth appears to be a longer process than that of the other teeth.

In anthropoids the structure of the permanent teeth varies with the species, and even with the sex. In the gorilla the two upper central incisor teeth are wide, chisel-shaped, and much larger than the pair of lateral incisors. The four lower incisor teeth are of about the size of the upper lateral incisors, and, like these, are chisel-shaped, but not so wide. The powerful upper canine teeth of an aged male are curved in their lower part, both outwards and inwards. Their form is that of a three-sided, cuneiform pyramid. The anterior surface is rounded, and near its inner edge a deep furrow may be observed, extending from the neck of the tooth almost to its point. The outer and inner sides of the tooth meet in a sharp angle, somewhat convex in front, and level or slightly concave behind. The inner side is concave, and furnished, nearly in the centre, with a deep longitudinal farrow. The lower canine teeth of an aged male are shorter than the upper, curved on their upper and outer surface, and somewhat behind. Their form is also that of a three-sided pyramid, rounded in front. The longitudinal furrow which traverses their inner segment is much shorter than that on the upper tooth. The outer side is somewhat convex, and at the same time somewhat retreating, and is provided on its posterior segment with two longitudinal furrows, or more rarely with one, reaching from the neck to about the centre of the tooth. The inner side, like that of the upper teeth, is somewhat concave. The lower canine teeth project like pillars over the upper ones (Figs. 15, 16). The canine teeth of a young male gorilla are less sharp in their angles, although they already present the form of a three-sided pyramid. The canine teeth of the adult female gorilla are much smaller than those of the adult male, and are laterally more compressed. The three-sided pyramidal form is only slightly marked. The outer surface is convex and furnished with a scarcely apparent central longitudinal ridge. On the inner surface, or that which is turned to the cavity of the mouth, there are from two to three longitudinal furrows reaching from the neck to the centre of the tooth. The lower teeth are of a three-sided, pyramidal form, presenting an interior, posterior, and inner superficies.

The pre-molars of an aged male gorilla are wide, and are furnished with a large outer, and a smaller inner, cusp. The three four-cusped upper molars display a more regular and symmetrical arrangement of their cusps than is the case with the female, in which the position of the cusps is rather variable. Except for the difference of size, the relative conditions of these teeth are the same in male and female. The first pointed lower pre-molars are in the male of the form of a four-sided pyramid, convex on the anterior and outer surface, flat on the side directed to the cavity of the mouth, and marked with furrows on the posterior surface. The small second and lower pre-molars have two anterior and one posterior cusp. The last is generally worn away at an early age. Each molar tooth has two outer and two inner cusps, opposite to each other, and one posterior cusp. We cannot here fail to notice the likeness to the conditions of the human teeth, a likeness which is still more striking in the female.

In the chimpanzee, also, the upper central incisor teeth are broadly chisel-shaped, while the upper and lower lateral incisors are smaller. In the male there is often a considerable gap between these and the canine teeth. The latter present the form of a three-sided pyramid, of which the anterior edge is blunt and tends outwards, while the posterior angle is sharp, scooped out in its upper third, and terminating at the base of the crown in a posterior cusp. The pre-molars have an external and an inner cusp; the molars have two external and two inner cusps, connected with each other by their enamel. The lower canine teeth of these animals are likewise of the shape of a three-sided pyramid, of which the anterior angle is very blunt, while the inner and posterior angles are sharply cut. The anterior surface is not grooved like the upper canine teeth. The lateral angle is much rounded. The back teeth plainly display the posterior fifth cusp, which may also be observed in man. In the orang-utan the characteristics of the upper incisors are such as we have described in the case of other anthropoids. The upper canine teeth are shaped like a three-sided pyramid, and are furnished with a longitudinal furrow on the anterior side. A similar furrow is found on the posterior superficies of the lower canine teeth. The back teeth display no special characteristics when compared with those of other anthropoids.

The canine teeth of these anthropoids are much worn down by age on their posterior surface. Deep transverse grooves of varying size characterize the teeth of anthropoids, owing to the unequal distribution of the coating of enamel. These are developed with their advancing growth. In addition to these incised furrows, longitudinal marks, with raised edges, also appear, and especially on the anterior surface of the incisor teeth.

In the gibbon the anterior surface of the incisor teeth is smooth; in this animal the upper central incisor teeth are the largest, while the lower central incisors are the smallest. The long and strong upper canine teeth, which are laterally compressed, display a sharp posterior angle, and an anterior and inner longitudinal furrow.

It has sometimes been said that the grooves found on the external contour of the back teeth of anthropoids, extending to their roots, constitute a not unimportant distinction between their structure and that of the human teeth, in which the grooves do not extend to the roots. But the corresponding human teeth do sometimes exhibit very deep and extensive furrows. I cannot, therefore, ascribe any peculiar significance to this assumed distinction. The development of the canine teeth, like those of beasts of prey, seems to me much more important. A supernumerary back tooth may sometimes be observed both in man and in anthropoids, including also the gibbon.[77]

The stomach and intestines of these animals present only a few striking differences from the same organs in man. The length of the intestines varies in man as well as in anthropoids. I have only observed the _valvulæ conniventes_ to be somewhat clearly developed in the gorilla and the orang. The cæcum of these apes is long, broad, placed with the power of free movement in the peritoneum, and furnished, especially in the case of the orang, with a large, very long, and spirally coiled vermiform appendix.

The liver is divided into two principal lobes, but in the orang this division is not very clearly marked. I have not myself observed a subdivision of these lobes, occurring on their edges, which is mentioned by Bolau and Auzoux in the case of the gorilla. Bischoff notices in the gorilla the absence of the H-shaped arrangement of the fissures on the under surface of the liver, so noticeable in man; and the same remark applies to other species of anthropoids. Moreover, the fissures on this part of the liver are not incised on the substance with the same uniform depth. The gall-bladder of the gorilla and the orang is not remarkable for its size; in the chimpanzee I found that this organ is large and twisted, and it is also large in the gibbon.

The spleen is elongated in the gorilla, chimpanzee, and gibbon, shorter and wider in the orang. On its left contour it is uniformly bevelled off. There is nothing in the pancreas which calls for remark.

The larynx of anthropoids possesses on the whole a structure resembling that of man. This is especially the case at the entrance to that organ. The anterior and specially vocal portion of the glottis is short, about as long as the respiratory portion. In the chimpanzee there is a deep cavity in the body of the hyoid bone. In the gorilla, chimpanzee, and orang the throat-pouches or air-sacs correspond to Morgagni’s sacs. These are the thin-skinned elastic sacs, closely united with their surroundings by connective tissue. The right laryngeal sac appears to be of larger diameter than the left. According to Duvernoy’s and Ehlers’ accurate account only the upper portion of this organ occurs in the gorilla. In that animal, and in the orang, a lower projection is displayed, extending behind the sterno-mastoid as far as the shoulder, and another extending to the pectoralis major muscle. In the chimpanzee only the posterior segment is developed. It has been asserted that in several cases there is found a single, irregular laryngeal sac, communicating with the two Morgagni sacs, but I agree with Ehlers in thinking this improbable. In such instances it seems likely that, owing to the great want of symmetry in this organ, one of the sacs has been overlooked. In an aged orang the throat-pouches, fastened together by connective tissue, and covered by the external skin of the throat, hang down slackly and heavily over the middle of the breast (see Fig. 9). According to Sandifort, the siamang is the only one of the gibbons which displays a single throat-pouch; while Broca asserts that it has two detached sacs, placed close to the larynx.[78] The halves of the thyroid cartilage are generally connected with each other by an intermediate piece.

The trachea of anthropoids generally includes from sixteen to eighteen cartilaginous rings, but in the siamang there are twenty-one. They ramify into branches which are, as a rule, wider on the right than on the left side.[79] There is a further lateral ramification on the right side, situated above the artery. Huxley and Ehlers hold that the lungs of a gorilla are cleft like those of the human organism, the right divided into three, and the left into two lobes. I have myself observed this type, and in one instance I found three lobes on the left. In the chimpanzee I saw that the right lung was divided into three, and the left into two lobes. Bischoff observed an instance of a chimpanzee which had four lobes on the right and two on the left side. In an orang dissected by me I found only one lobe on each side, with thin, slightly indented notches on the anterior edges of the right lobe, and two on the left, and there was at the same time a strongly marked indentation between the lobes. The lungs of a gibbon are described as having four lobes on the right, and only one or two on the left. I myself have examined a gibbon in which there were three lobes on the right, and two on the left. It appears that there are not unimportant individual variations of this structure in every species of anthropoids; and indeed, human lungs are by no means exempt from them.

The male sexual organs correspond on the whole with the form and arrangement of these organs in man. I must not omit to mention that the penis of the swine-snouted baboon, and of other dog-headed apes, is much more like the penis in man than is the case with anthropoids, with the exception of the gorilla. In the last-named animal the scrotum is short and tightly stretched. The right testicle is a little higher than the left, and is divided from it by a wide raphé. The internal female organs are also like those of the human organism, with only slight variations. Bischoff is correct in the assertion that the external lips of the pudendum and the mons veneris are almost wholly absent. Bolau, Ehlers, and Hermes have ascertained that there is a menstruation which occurs periodically, at any rate in the case of the chimpanzee, and the other species cannot be exempt from the process. At such times there is a blush and enlargement of the external parts, and a profusion of the external lips of the pudendum, which are at other times scarcely apparent. The nymphæ and the clitoris are of considerable size and importance. There is often an excessive enlargement and reddening of these parts, as well as of the posterior callosities in the chimpanzee, and also in the baboon and macaca, during the period of sexual excitement.

Fig. 56.--The brain of an orang, seen from the side (Vogt, from
Gratiolet). F, Frontal lobe. P, Parietal lobe. O, Occipital
lobe. R, Fissure of Rolando. S, Fissure of Sylvius. C,
Cerebellum.
]

_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]

Fig. 57.--Brain of the chimpanzee, seen from above. The upper
part of the right hemisphere is removed so as to lay bare
the lateral ventricle (Vogt, from Marshall). L, Longitudinal
fissure (other indications the same as in Fig. 56). _c s_, The
corpus striatum in anterior cornu of the ventricle. _c a_,
Hippocampus major in descending cornu. _h m_, Hippocampus minor
in posterior cornu.
]

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 orang[81] (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.

Fig. 58.--Brain of gorilla, side view (from Bolau and Pansch).
I., Frontal lobe. II., Fissure of Rolando. III., Parietal lobe.
IV., Temporal lobe. C, Cerebellum. _f s_, Fissure of Sylvius.
_s c_, External fissure parieto-occipital.
]

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).

Fig. 59.--Brain of orang, seen from above (Duncan, from a
specimen in the Museum of Royal College of Surgeons). F,
frontal lobe. O, Occipital lobe.
]

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.

Fig. 60.--Longitudinal section of a gorilla’s brain (Bola and
Pansch). _s.cm_, Colloso marginal fissure. _f, p_, Internal
parieto-occipital fissure. _f, c_, Calcarine fissure, the
posterior part of the hippocampal fissure.
]

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 developed[82] (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.