CHAPTER III.

THE EXTERNAL AND ANATOMICAL STRUCTURE OF ANTHROPOID APES, COMPARED WITH THE HUMAN STRUCTURE.

In order to complete as far as possible the description which we propose to give of the general natural history of these remarkable animals, it is necessary to examine their anatomical structure. Yet it is not so much our aim to give a detailed and exhaustive description of their anatomy, as to glance rapidly at those peculiarities of their inner structure which catch the eye. It seems to me expedient in this case to follow the method of systematic and descriptive anatomy, and to take the several natural organs in succession. This method, which has long prevailed for studying the structure of the human body, should also be our guide in our researches in comparative anatomy. Our readers need scarcely be told that the anatomy of anthropoids is only a small branch of the comparative anatomy of vertebrate animals in general.

I begin by considering the bony structure of anthropoids, and, in particular, of the gorilla. And it will be well to note the important differences between the structure of the skull of a young and aged male, and of a young and aged female gorilla.

[Illustration: Fig. 15.--Skull of an aged male gorilla in profile.]

The skull of the aged male animal is large and heavy. Its average weight is one and a quarter kilogrammes. The longitudinal diameter, from the alveolar point of the upper jaw to the occipital point, may be as much as 294 mm. The overhanging orbits are high in front, and flattened off behind, and their upper edges unite to form a ridge in the middle of the face. To these the back parts of the orbits are attached, in shape like a truncated cone, round and prominent in front, and narrowing into bony capsules in the direction of the brain-pan. They open directly in front, and the aperture is generally in the form of a regular square. The edges are seldom so blunted off as to present a figure somewhat approaching to a circle (comp. Figs. 15, 16). The frontal bone, which in the young of both sexes is high, broad, and arched, becomes depressed in the centre in the aged male. The temporal ridges, thickened to a hem, pass over this to the coronal crest.

[Illustration: Fig. 16.--Front view of the skull of an aged male gorilla.]

This crest is highly characteristic. It begins in the region of the frontal bone, and, rising abruptly, unites itself with the transverse occipital crest. It is of varying height,[12] but is rarely altogether absent in an adult male animal. On the top of this coronal crest we may see the two well-developed bony ridges which almost touch each other, and which indicate the upper limits of the temporal muscles on either side. In young animals these ridges tend downwards over the sides of the head, below the vertex of the skull. Their position and direction vary with the growth of the skull, and correspond with that of the coronal crest. The transverse occipital crest is of considerable height in the case of aged and vigorous animals, and is frequently somewhat concave in front, and convex at the back. The fore surface of this crest is formed of the two parietal bones, the hinder surface of the squamose portion of the occipital bone. The lambdoidal suture is on the top of this occipital crest, and in this case, as in that of other mammals, including man, it unites the parietal bones with those of the occiput. The point of union between the coronal and occipital crests divides the latter into two symmetrical lateral halves, curving outwards and downwards. The high, wide squamose portion of the occipital bone is somewhat flattened behind, or more rarely arched, while it is abrupt at its base and in some degree in front. Six curved lines, three on either side, opposite each other, sometimes mark the limits of the attachments of the cervical muscles on the head. The mastoid process of the temporal bone is present, but Brühl could find no trace of a styloid process on the skulls of gorillas and chimpanzees.

The squamous portion of the temporal bone is often connected with the frontal bone by the process termed Virchow’s frontal process of the temporal bone. The nasal bones are high, very narrow in their upper part, and widening below. When they are united in the centre of the nasal bridge, a sloping, keel-shaped projection may often be observed. The inferior turbinated bones of the nasal cavity are remarkable for their size. In the skulls of young animals the inter-maxillary bones, which are in all anthropoids early united with those of the same region, stand up high and peaked between the nasal bones and those of the upper jaw.

The crowns or prominent external surfaces of the enormous canine teeth project in the centre of the face on either side like pillars, just below the nostrils, and extend above and below the row of teeth in the two upper jaws (see Fig. 16). In this way the crowns of the canine teeth form a retreating triangular space, of which the base-line of the equilateral triangle corresponds with the row of teeth. The chin part of the lower jaw, in a front view, also takes the form of an equilateral triangle. In the latter case the base-line is covered by that section of the row of teeth containing the incisor teeth. The sides of the triangle are covered by the converging canine teeth (see again Fig. 17). The incisor teeth, enclosed between the latter, in that part of the lower jaw already described, are retreating. The rami of the lower jaw are high and very wide. The angle of the lower jaw is obtuse (Fig. 15). The front or coronoid process and the back or condyloid process of the ramus of this bone are separated from each other by a deep, hollow cleft. The condyloid process projects abruptly above, but is less marked behind.

When we consider the internal form of the skull of an aged male gorilla, the first thing that strikes us is the marked development of the frontal sinuses, and especially their width in the region of the nasal portion of the frontal bone. We next observe the wings of the sphenoid bone, and that these large concave apophyses are provided with spaces only slightly separated from each other. These sinuses are not only plainly connected with each other, but with the sphenoidal sinuses. There is a broad sinus in the malar bone, provided with vestibules, and this has a deep communication with the maxillary sinus, or antrum of Highmore, embedded in the body of the upper maxillary bone. There are, finally, sinuses at the point of junction between the coronal and occipital crests.

The maxillary region of the cranium of the young male gorilla is already somewhat prognathous, and the keel-shaped elevation of the bridge of the nose is also very apparent, but the development of these parts is not nearly so advanced as in the aged male. The whole contour of the cranium is oval, and without the high crests so characteristic of the aged male animal. It is well known that the Swedish anatomist and anthropologist Anders Retzius has classified the skulls of different races of men as long-headed (_dolichocephali_) and short-headed (_brachycephali_). In the former class, the length is considerably greater than the height; while in the latter, the difference is either slight or non-existent. The skulls of the _dolichocephali_ are long and oval; those of the _brachycephali_ are short, round, or square. In addition to this division, which is of great value in the rapid and superficial, yet sound classification of racial skulls, Retzius has constituted another. He has characterized skulls of which the profile is straight, or nearly straight, as _orthognathous_ (_rechtzähnige_); and those of which the maxillary region is very prominent, as _prognathous_ (_schiefzähnige_). These orthognathous and prognathous skulls may be either dolichocephalic or brachycephalic.[13]

In applying this classification by Retzius to anthropoids, the gorillas and chimpanzees have been characterized as dolichocephalic and prognathous, the orang-utans and the gibbons as brachycephalic and prognathous. Several scientific men have sought to establish the noteworthy distinction that dolichocephalic anthropoids are found in Africa, and brachycephalic anthropoids in Asia. This distinctive characteristic is held to agree with the geographical and ethnological conditions of the continents in question.[14] Virchow remarks in a later work that the skull of a gorilla becomes longer with every year of life, but that this is not so much due to the cranium as such, as to its bony outworks, such as the strongly developed supra-orbital arches, the enlargement of the frontal sinuses, etc. Measurements rather tend to show that the young gorilla is brachycephalic, but that this characteristic diminishes with increasing age, at any rate, if the external excrescences are taken into account. But it is quite otherwise when the furthest point of measurement is taken from the frontal arch, not from the nasal prominence. In such a case the increase of the brachycephalic condition is established.[15]

In the skulls of such young males as those here mentioned, the temporal ridges, which in aged animals are in close proximity in the region of the developed bony crests, have already in some cases begun to approach each other, but they are still far apart. In young specimens we can distinguish, on each side of the parietal bones, two temporal ridges, opposite each other, and taking a nearly parallel course. The upper ridge, which loses itself on the external surface of the mastoid process, which is already developed, corresponds to the junction of the fascia of the cranial muscles (_Galea aponeurotica musculi epicranii_) with the fascia enclosing the large temporal muscles. The lower ridge, which is gradually merged in the upper edge of the zygomatic process of the temporal bone, forms the demarcation of the fleshy origin of the temporal muscle. This corresponds to the spot at which the two layers of the temporal fascia unite. In a very young male these temporal ridges can be only faintly traced; they become more strongly marked as his growth advances, and as they approximate more closely to each other on the vertex of the cranium. I have examined a skull of which the sutures were still open, and could already trace the development of the coronal crest in two divisions, separated from each other by a longitudinal furrow. The upper edges of these divisions corresponded to the two temporal ridges, which were in close proximity to each other. If the animal had not died at this stage of its development, it is probable that, with advancing growth, the two divisions of the crest would have been welded into one structure. Such a condition only characterizes a transitory stage of development, repeated in each individual.

In the centre of the vertex of the cranium, where the longitudinal crest of which we have so often spoken is subsequently developed, we may often observe on the sagittal suture of the cranium of a young male a longitudinal swelling, which increases very gradually. In the region of the two upper semicircular curved lines (_lineæ semicirculares s. nuchæ supremæ_), on the squamous occipital portion, or between these and the two central cervical lines, a transverse swelling is early developed; this swelling sometimes extends to the lambdoidal suture, or, at any rate, to its neighbourhood. This bony excrescence, of which the anatomical term is _Torus occipitalis transversus_, corresponds to the first layer of the transverse occipital crest so characteristic of the old male gorilla (see Fig. 15).

In several skulls of young gorillas, in the region of the coronal suture, a small, insulated, intermediate bone may be observed (Virchow’s _os epiptericum_) between the squamous portion of the temporal bone and the greater wing of the sphenoid, with which it is sometimes completely welded. In this case there is, above the _os epiptericum_, a direct connection between the temporal and frontal bones by means of the frontal process (Virchow’s _processus frontalis squamæ temporalis_), which is not rare in anthropoids.[16] This process often owes its origin to the _os epiptericum_, which is in its early stages attached to the temporal bone. I shall have to refer again to this frontal process.

The orbits are more rounded in young than in aged skulls; in the latter they are always angular, although the angles, especially the upper and external angles, may be more or less blunted. Virchow remarks that in the skull of a very young gorilla the height of the orbit exceeds its width, and that at that age the skull is therefore high. In the aged male gorilla the height of the orbit, according to the several measurements I have taken, varies between 39 to 52 mm., and the width between 37 to 45 mm.

[Illustration: Fig. 17.--Skeleton of an aged male gorilla.[17]]

The rest of the skeleton of the aged male gorilla corresponds in its powerful and massive form with the general structure of the body, which is remarkable for its height and strength (see Fig. 16). In the skeleton of the trunk there are seven cervical, thirteen dorsal, and four lumbar vertebræ, thirteen ribs, and, even in aged animals, a sternum composed of several pieces of bone. The cervical vertebræ display long spinous processes, which are most strongly developed between the fourth and seventh vertebræ. The extremities of this colossal structure, combined with the elevation of the occipital region, present a convex outline when seen from behind. This structure provides the point of insertion and support for the powerful cushion of cervical muscles. The dorsal vertebræ, which increase in height, width, and depth as they stand lower on the column, taper, and are keel-shaped at their junction with the cervical vertebræ. The central parts of the widely arched ribs, which are thirteen or sometimes fourteen in number, are very thick and powerful in the aged male. Only seven pairs of ribs are attached by the costal cartilages to the sternum, and two other costal cartilages are in proximity with them. The other cartilages are only rudimentary, and the terminations in the muscular system of the belly are free. There are, indeed, variations from the type here established, and from ten to eleven ribs are sometimes attached to the sternum by thread-like strips of ligament or cartilage.

The formation of the pelvic girdle in this animal is of special interest. The chief parts of this portion of the skeleton--that is, the hip, pelvic, or innominate bones--are high, tapering in their lower part, and broad and flat above, where they terminate in the crest of the ilium, which describes a quarter of a circle. There is, for the most part, only one small superior iliac spine, and the ischii are somewhat turned outwards, and furnished with broad, rounded tuberosities, and for the most part with only a single large sacro-sciatic notch. The horizontal rami of the pubes are narrow, while the descending rami are wide. The os sacrum is narrow, and shaped like a protracted cone, turning abruptly outwards, and resembling the basal joint of a true tail. The coccyx appears to be the rudiment of a genuine tail.

The bones of the shoulder-girdle present interesting peculiarities. The clavicles are long and slender, with a leaf-shaped, flattened end articulating with the scapula, and a thickened end articulating with the sternum. The scapula is a very large triangular bone, resembling the human scapula in its general form, and the supra- and infra-spinous fossæ are not strongly marked. The long and powerful humerus has its head inclined at an angle of sixty degrees towards the axis of the shoulder. Frequently, but not invariably, the lower, flattened extremity of the humerus is pierced on one or both sides above its rounded eminence, and this is termed by Darwin the intercondyloid foramen.

The radius has a powerful head, and a shaft considerably curved outwards, while it is, on the other hand, curved backwards and inwards at the elbow. The bones of the carpus, metacarpus, and phalanges are remarkably long, broad, and deep. The development of the femur corresponds to that of the whole skeleton. Its middle piece or shaft is curved in front and flattened behind. The shaft of the tibia is generally rounded off, but is sometimes rather laterally compressed.

The os calcis of the foot is slender, curved outwards in the centre and inwards behind the astragalus. The head, with its cuneiform extremity, is of a transverse oval shape, turned inwards. The scaphoid bone, which is generally in connection with this projection, takes the same direction towards the inner side of the foot. This peculiar contortion causes the tarsus of the gorilla to appear almost as if it had been subjected to a deviation or fracture of its longitudinal axis.

In young and adult males, as well as in young females, the structure of the bones is generally less massive than in aged males. In the female skeleton the strongly developed depressions and ridges, especially in the bones of the extremities, are absent. The head of the ulna is, for example, less deeply set in the case of a female, and its projections are smaller than in the male animal. In the female, also, the head of the radius is smaller, and the triangular shape of its shaft is less strongly marked. The pelvic bones of a female gorilla are wider, flatter, and less concave on their very projecting inner surface. They diverge more widely from each other, and this is also the case with the tuberosities of the ischium. The pubic arch is less depressed than in the male gorilla. Although the spinous processes of the vertebræ attain to some length and thickness, their development in the female is not so great as it is in the male sex.

The bony structure of the chimpanzee offers many points of resemblance to that of the gorilla, while it differs in certain particulars from the structure of other anthropoids. And first, the size of the skeleton is smaller than that of the gorilla, which is in agreement with the smaller relative size of the body of the chimpanzee.

[Illustration: Fig. 18.--Skull of an aged male chimpanzee.]

We must begin with a general view of the skull of the chimpanzee. In both sexes the frontal regions are smaller, while the coronal region is more rounded than in the gorilla. The high bony crests and prominent supra-orbital arches are wanting in the chimpanzee; the peculiar character of the bony ridges, projecting like tubes from the other parts of the skull, is less marked, and they belong more directly to the frontal region (see Fig. 18). The bony bridge of the nose is more concave in the chimpanzee; the jaw-bones are smaller and less compressed in the centre than they are in the gorilla.

When we undertake to describe the skull of the chimpanzee in detail, it becomes necessary to consider separately the skulls of aged and young males, and of aged and young females; for in this case also the distinctions of sex and age are very evident. On the skull of an aged male chimpanzee the temporal ridges are not much developed on the coronal arch. They meet on this arch from 60 to 90 mm. behind the orbits, and form only a small coronal crest. The transverse occipital crest is somewhat developed, and at its point of union with the coronal crest the temporal ridges divide to form its upper edges. This is the case not only with the Rio Quillu skull, from which Fig. 18 is taken, but with that of the so-called troglodyte Tschègo given by Duvernoy.[18] In some other specimens belonging to aged male animals the presence of a coronal crest cannot, however, be detected. In these the temporal ridges are very small, and more or less distant from each other. While the transverse occipital crest maintains an almost uniform height on the gorilla skull, like a detached ridge, it is only slightly elevated behind in those chimpanzee skulls in which the crest is partially developed. In the gorilla male this ridge divides the squamous occipital portion, which is sometimes bevelled, sometimes slightly convex; in the male chimpanzee this part is more decidedly arched, and takes the form of a half-oval. The mastoid processes are also present in the chimpanzee. The external occipital crest and the curved lines are generally apparent. The styloid processes are more plainly traced than in the gorilla. In the latter, as well as in the chimpanzee, there is a blunt, tubular process of the temporal bone, opposite to another bony process, issuing from the occipital bone. This has been observed by Virchow, and is termed by him the carotid process (_Processus caroticus_).

The orbits of the chimpanzee are generally more rounded, with a distinctly circular rim, while the nasal bones are as long and narrow as in the gorilla. The region of the jaws is very prognathous; the external nasal openings are rounder and smaller than in the gorilla. The crowns of the canine teeth project in the same pillar-shaped form (Fig. 18). The triangular space enclosed by these and by the row of teeth in the upper jaw is often very wide and projecting, even more so than in the gorilla. But whereas in the latter the canine teeth are shaped almost like a three-sided pyramid, in the chimpanzee they are more rounded and conical. In the general structure of the teeth of both species there are certain differences of which we shall speak presently.

The brain-pan of a young male chimpanzee is still more arched than it is in aged animals. The temporal ridges are still far apart. The transverse occipital crest displays near the mastoid process well-defined wing-shaped indentations. In the skulls of very young males the transverse occipital swelling of which we have spoken (_Torus occipitalis transversus_) is already developed. The orbits are distinctly detached from the skull; the bridge of the nose is depressed; the crowns of the canine teeth are, in conformity with the still slight development of the teeth themselves, less marked, and the triangular space enclosed by the teeth is less convex than in older animals.

The skull of the adult chimpanzee is, in its coronal and occipital parts, more uniformly arched, narrower, and more elongated than in aged males. The transverse occipital ridge usually develops itself in the region of the upper curved lines, or in the bony parts enclosed between these and the central lines. The nasal and upper maxillary region is depressed. That section of the upper jaw which contains the incisor and canine teeth is small. In the skulls of all chimpanzees, of whatever sex or age, the body of the lower jaw is comparatively small, with two low but wide rami, of which the coronoid and condyloid processes are divided from each other by a comparatively wide cleft. The rami of the chimpanzee’s lower jaw are still more abruptly retreating than is usually the case in the gorilla.

The skull of a very young female gorilla is shaped almost like a half-sphere. The orbits are scarcely detached from the forehead; the want of elevation of the orbital arch, and the slighter prognathism of the jaw, is marked by the deep depression between it and the nose and forehead (Fig. 20).

The cancellous texture of the bones of the chimpanzee’s skull admits of a whole system of cavities communicating with each other, which are of the nature of the so-called sinuses present in the frontal, sphenoid, ethmoid, and maxillary bones of the human skull. In the chimpanzee, however, the sinuses are more extensive than in man, or even than in the gorilla. The large cavities of the forehead communicate with those of the nose and jaws. The sphenoidal sinuses and ethmoidal cells are large and deep. The greater wings of the sphenoid bone and its pterygoid processes are provided with considerable cavities. The mastoid cells of the temporal bones are in connection with the cells of the greater wings and pterygoid processes of the sphenoid bone, and also extend through the squamous portions and zygomatic processes of the temporal bones, losing themselves in their upper part in the smaller cells of cancellous bone which are found between the outer and inner walls of the skull. These are of more uniform shape and size.

[Illustration: Fig. 19.--Skull of a very young female chimpanzee.]

The skeleton of the chimpanzee, in accordance with the smaller size of the species, is relatively of a slenderer build than that of the gorilla. The spinous processes of the seven cervical vertebræ are more slightly developed, and have undivided extremities. The transverse processes of the fifth and sixth cervical vertebræ are almost of the same shape as cervical ribs. There are thirteen dorsal vertebræ, somewhat laterally compressed: this compression is greater than in man and in the gorilla. The four lumbar vertebræ of the chimpanzee are furnished with long, thin, riblike transverse processes. The so-called mammillary processes of the final vertebra are strongly developed in the male. The intervertebral foramina are small, as they are also in the gorilla and orang-utan. The thirteen ribs of the chimpanzee remind us of the human structure. The collar-bone is slightly curved, as in the gorilla. There is a marked difference between the sexes in the structure of the scapula which is broad and three-sided in the male, small and leaf-shaped in the female.

[Illustration:

Fig. 20.--Skeleton of the forearm and hand of the Central African bam-chimpanzee. _a_, Ulna. _b_, Radius. _c_, Scaphoid bone. _d_, Semi-lunar bone. _e_, Cuneiform bone. _f_, Pisiform bone. _g_, Trapezium. _h_, Os magnum. _j_, Trapezoid. _k_, Unciform bone. _l_, Phalanges of thumb. _m_, Metacarpal bones. _n_, Phalanges. ]

The humeri have slender shafts, with well-developed condyles and ridges. The bones of the forearm are much curved, so that the interval between them is, as in the gorilla, somewhat wide. From the wrist to the final phalanges the hand is more slender than in the gorilla.

The pelvis in this species of ape has high, narrow ilia, spreading in their upper parts, and projecting forwards, so as to form the cavity of the abdomen, and, especially in the male sex, the anterior spines of the ilium are more strongly developed than in the gorilla and orang-utan. The ischiatic tuberosities are of a spreading form, and diverge considerably from each other. The pubic arch is deeply hollowed, but the point of juncture is elevated. As in the gorilla, the os sacrum resembles the basis of a tail, but it is less developed and less conical in form.

In the chimpanzee, as well as in other anthropoids, the coccyx gives altogether the impression of a laterally compressed and rudimentary tail. This is especially the case in young animals, in which the coccyx always appears to be very narrow and prolonged. In older animals this part gradually widens, yet without losing its resemblance to a rudimentary tail.

The head of the femur resembles a section of a sphere, of which the upper part is sometimes wanting. Its shaft, which is curved in front, is much slenderer in the female than the male. The patella is oval. In the tibia the narrow shaft is laterally compressed, and bent inwards. The bones on the inner side of the foot take a backward direction, while those on the outer side, attached to the fibula, turn outwards.

In the ankle-joint the head of the astragalus is much arched, and turned inwards. The scaphoid bone is thick and deeply hollowed. The metatarsal bones and phalanges have a considerable upward convexity (Fig. 21).

[Illustration: Fig. 21.--Skeleton of foot of the Central African bam-chimpanzee. _a_, Astragalus. _b_, Os calcis. _c_, Scaphoid bone. _d_, _e_, _f_, Cuneiform bones. _g_, Cuboid bone. _h_, First metatarsal bone. _j_, Second to fifth metatarsal bones. _k_, Phalanges.]

The skeleton of the orang has also its special characteristics. We have already remarked, in describing the external form of the heads of these animals, that the skull is high and projecting, and retreating in its hinder part. In the old male orang this part of the bony structure is of smaller size than in the old male gorilla. The arch of the cranium is shorter and rounder than in that animal and in the chimpanzee. The central longitudinal crest of the vertex is present, but in accordance with the more spherical shape of the coronal part of the cranium, this crest is more arched above than in the gorilla, in which it slopes gently upward to the transverse occipital crest, which rises high and peaked from the back of the head. This latter crest is indeed developed in the orang, but it is not so high, and is more retreating. In consequence of this formation, the upper posterior part of the gorilla-skull appears in profile to be much more abrupt and peaked than that of the orang. In the latter, also, the orbital arches are not so high and abrupt, and not so much detached from the rest of the skull. In the orang the squamous occipital portion declines abruptly in front and below, yet it is generally more arched than in the gorilla. The orbits of the orang, which are sometimes rounded, sometimes more square, are divided from each other by a narrow partition. The space between them and the anterior nares is not so great as in the gorilla. While in the last-named animal the space between the root of the nose and the teeth of the upper jaw-bone is convex, in the chimpanzee it is generally vertical, and in the orang it is depressed (Fig. 22). The maxillary parts, furnished with strong canine teeth, are very prognathous, yet hardly to the same extent as in the chimpanzee. The body of the lower jaw is high, and its rami are high and wide. The bony crests of which we have spoken are absent in the female. The coronal part and the squamous occipital parts are arched; the upper jaw is smaller, and the lower jaw is also less massive, than in the male animal. In very young animals the predominance of the strongly arched cranium over the countenance is apparent, and the increase of size in the latter occurs gradually (Fig. 23).

[Illustration: Fig. 22.--Skull of middle-aged female orang.]

The anterior nares are narrow at the top, and wide at their base. They are more decidedly pear-shaped (_Apertura pyriformis_) than those of the gorilla and chimpanzee. In the latter animals these apertures are generally wider and more uniformly rounded. Bischoff justly observes that the bony part below the orbits, which in the gorilla is wide above, tapering away in the lower part of the face, is narrower and more vertical in the orang. The nasal bones of the orang are high and of moderate width. Brühl mentions the styloid process of the orang’s skull, which is, however, somewhat abortive when we compare it with that of the human skull. It has its origin in a tolerably deep groove. On the other hand, Brühl, as we have already observed, can find no trace of the styloid process in the skulls of the gorilla and the chimpanzee![19]

[Illustration:

Fig. 23.--Skeleton of young orang-utan. _a_, Sternum. _b_, Radius. _c_, Ulna. _d_, Tibia. _e_, Metacarpus. _f_, Phalanges. _g_, Great toe. _h_, Fibula. _j_, Hip-bones. _k_, Coccyx. _l_, Vertebral column. _m_, Scapula. _n_, Femur. ]

There are many large-celled bony cavities in the orang’s skull. These may be observed in the greater wings and pterygoid processes of the sphenoid bone, in the mastoid and squamous parts of the temporal bones, in the lachrymal bones, in the body, and in the condyles of the occipital bone, and in the zygomatic arch. The larger fore-cells on the squamous part of the temporal bones are connected by a wide aperture with the sinuses of the greater wings and pterygoid processes of the sphenoid bone. A sinus which may be observed on the greater wing generally communicates by a large round hole with the temporal cells. There is generally, but not always, a communication between the sinuses of the greater wing and pterygoid process and the nasal cavity. These cavities sometimes communicate with each other through a wide aperture at the base of the nose. The squamous part of the temporal bones has a cellular sinus, which communicates with the cells of the mastoid process, in its lower part with the tympanum, and in its fore-part with the ossicles of the lower wall of the tympanum. The maxillary sinuses are in connection with the cells of the lachrymal bone. There is nothing in the orang’s skull corresponding to the Vidian canal of the sphenoid bone, but it may be traced in the gorilla and the chimpanzee.

The vertebral column of the orang has not the same colossal spinous processes which distinguish that of the gorilla. It differs also in many other, though less striking, particulars both from the gorilla and the chimpanzee. In the orang there are generally twelve dorsal vertebræ, tapering in their lower parts; while their long, thick, transverse processes, which are full of knots, take an upward direction. The upper articular processes of the four lumbar vertebræ present short and rather insignificant mammillary processes. The sternum of the young orang is generally formed of one large upper bone, with six smaller bones below. In older animals the body of the sternum appears to consist of a tier of three bones connected together. The ribs resemble those of the human skeleton, the clavicle is long and straight, and the scapula also resembles that of a man in form. The flat pelvic bones of the orang also turn outwards; the ischiatic bones are short, with spatula-shaped tuberosities; the pubic arch is high, and the obturator foramen is narrow and oval. The sacrum and coccyx do not resemble a rudimentary tail so much as in the case of the anthropoids we have already described. We are reminded of the human structure in the humerus, of which the shaft is much curved behind, and on its outer side. The ulna is very slender, and provided with a protracted, jagged styloid process. The neck of the radius is tapering, while its shaft is arched like that of the ulna, and the anterior border and oblique line are sharp. The wrist, metacarpus, and fingers are long and narrow.

The femur of the orang is remarkable for its large head, shaped like a section of a sphere, and its slender shaft. The latter is less bent than in the gorilla. The patella, which, in my opinion, should be classed among the so-called sesamoid bones, is in this case of an irregular form. The shank and foot-bones are remarkably slender. The scaphoid is tapering; the head of the astragalus does not turn inward so much as in the gorilla. The hinder surfaces of the metatarsal bones and of the phalanges turn decidedly outwards.

We have now to consider the bony structure of gibbons, in which there are many specific variations which our space will not allow us to consider in detail, but a slight sketch of their organic system must be given. The brain-pan of this animal’s skull is of an oval shape, without the crests so characteristic of other anthropoids, and even in the aged males of this species their development is so slight as to be scarcely perceptible. The occipital bone of male animals is, indeed, generally rounded, and the whole occipital portion is somewhat compressed in a downward direction, while the coronal region is at the same time flattened. The cranium gradually widens behind, so that, when seen from above, its form is somewhat pear-shaped. In aged males the orbits project from the low, retreating frontal bone, and are surrounded by a bony, circular rim.

The face is not very prognathous, and the short wide nasal-bones form a wide, depressed partition between the orbits. The edges of the jaw-bones describe a parabolic curve and are considerably elongated. The palate is consequently long and narrow. The rami of the lower jaw are wide and low, and their coronoid processes are only slightly developed. In aged males the teeth, and especially the canine teeth, are long and projecting; yet, comparatively speaking, they never attain to the great development of those of other anthropoids.

The number of vertebræ seems to be subject to considerable variation even in the same species, and various estimates are given by different naturalists. Müller, for example, has said that in several species (_Hylobates syndactylus_, _H. leuciscus_, _H. variagatus_, and _H. concolor_) there are thirteen dorsal, five lumbar, six sacral, and four coccygeal vertebræ. Cuvier counted in the siamang, thirteen dorsal, five lumbar, four sacral, and three coccygeal vertebræ. In _Hylobates agilis_ I counted thirteen dorsal, six lumbar, five sacral, and four coccygeal vertebræ. _Hylobates syndactylus_ has long coccygeal bones, and an elongated os sacrum, which gives the impression of serving for the application of a short tail, or, indeed, of being in itself a rudimentary tail. In other respects the cervical, dorsal, and lumbar vertebræ differ little in structure from those of man.

The ribs on the sternum, which widens abruptly outwards, are strongly arched. The lowest of these project, owing to the width of the shaft. In the sternum there is a want of proportion between the smallness of its body and the size and width of its extremity. The ensiform appendix of this bone is long and wide, and spatula-shaped at its lower extremity. In the shoulder-girdle the clavicles are very slender, and much arched. The scapulæ, on the other hand, are high and narrow, spatula-shaped, and provided with a steeply projecting acromion process, a strongly developed coracoid process, and deep glenoid cavities. The upper limbs are, in conformity with the general structure of these apes, very slender; the shafts of the bones of the upper and forearm are elongated, with small extremities. The condyles are small, especially those of the elbow. The bones of the wrist, the metacarpus, and the fingers are also long and slender.

In the pelvis we note that the ilia are narrow below, and expand in the form of a spatula above, and that their position is almost vertical. Their inner surfaces are only slightly concave, and are directed somewhat forwards. The ischiatic bones are low, with wide, flattened, rugged tuberosities, and rounded _foramina obturatoria_. The ischiatic rami project forwards in an almost horizontal direction. There are large prominences on the pubic arch of the siamang.

The leg-bones are much shorter than those of the arm. The heads of the femurs stand out plainly from their short necks and large trochanters, as segments of perfect spheres. In this case, as in that of other anthropoids, the third trochanter (_trochanteres tertii_), often so apparent in the human femur, is barely indicated. The shank-bones are arched. The tibia is often laterally compressed, so that its transverse section forms a scalene triangle. The malleoli are compressed from before backwards. The elongated heel-bones appear to be laterally compressed. The canal between the astragalus and the os calcis (_Sinus tarsi_) is very wide. The metatarsal bones and phalanges have large bases, long slender shafts, and heads projecting on the under side. Even the final phalanges are long and slender.

[Illustration: Fig. 24.--The Zulu king, Ketchwayo, in fighting array, with two of his men.]

We shall now find it profitable to compare the external characters of anthropoids with those of man. We are sometimes disposed to see the true likenesses of anthropoid apes in dark-skinned, naked savages. These savages are often insufficiently fed, the skin is wrinkled, the face, even at an early age, is deeply furrowed, and their general appearance is neglected. The dark silhouette of such people stands out so distinctly against a clear background, their habit of life is so rude, their attitudes impress us so disagreeably, that we are involuntarily led to make such a comparison. This tendency unfortunately gives a wide field for exaggeration among dilettanti naturalists, and such as are zealous to establish a preconceived theory. A conscientious inquirer must, however, be cautious, and avoid too great generalization in such comparisons. For instance, much has been said of the pithecoid structure of all African negroes, yet this only applies to some peculiarly hideous races, in a state of physical degradation. There are many negro tribes in different parts of Africa which are remarkable for their well-formed bodies, and for a not ignoble bearing. The warlike demeanour of the natives of Ashanti, Dahomey, and Ibos is well known. Although the Hausanese are flat-nosed and thick-lipped, yet when armed and dressed in uniform, as we see in the photographs of Captain Glover’s force, their military bearing is very apparent. The tribes of Schilluk, Nuehr, Bari, Niam-Niam, and A-Bantu present examples of distinguished warriors, however rude and savage. Dabulamanzi, commander of the Zulus at the butcheries of Isandlhwana and Ulundi, and his chiefs, give me, in a photograph in my possession, the impression of gallant warriors, however uncivilized. In all these cases it is difficult to establish the resemblance to anthropoid apes (see also Fig. 24).

The Papuans, especially on the Australian continent, are generally classed with the African negroes in such comparisons. We admit that a horde of Australian blacks, degraded by hunger and fatigue, emaciated and dirty, may, as they roam through the shadeless woods, the steppes and thick scrub of their native country, present a strange and brute-like appearance. And if the foreign intruder takes a coarse pleasure in giving drink to these savages, their immodest gestures may afford a revolting impression of their bestial nature. Yet the habits even of these dark-skinned savages are altogether different under more favourable conditions. Although of small stature, they are not badly proportioned, and their manners and bearing are capable of improvement, so that they can act as native police, messengers, etc. This was the case also with the natives of Queensland, Australia, whom I saw in the Zoological Gardens, Berlin, throwing the boomerang. Even in these tamed savages, however, we must note the projecting orbits, the deep depression between the forehead and nose, and the flatness of the latter organ. There are aged, wrinkled bushmen, negroes, Papuans, Malays, Japanese, and Mongols of inland Asia whose countenances are altogether pithecoid. And such a cast of face may even be found in Europe.

Some years ago, Mr. Bond, a land-surveyor in British India, asserted that he had found the missing link between man and apes in the mountainous district of the Western Ghauts. And indeed, the race he describes seems to have a strong resemblance to apes. “The forehead is low and retreating. The lower part of the face projects like the muzzle of an ape; the legs are short and bent outwards. The trunk and arms are comparatively long. The hands and fingers are contracted so that the latter cannot be freely extended; a thick skin covers the hollow of the hand and the fingers, especially their tips; the nails are small and imperfect; the feet are broad, and covered both on their backs and soles with a thick skin. This tribe seems to worship nature. They have no fixed dwellings; they live chiefly on roots and honey, and exchange the latter, together with wax and other productions of their forests, for tobacco, clothes, and rice.”[20]

Nothing more, so far as I am aware, has been published concerning this race. The description given above leaves much to be desired. The assertion respecting the contracted fingers is obscure, and such a condition is directly opposed to any resemblance with the flexible hand of apes.

[Illustration:

Fig. 25. Aidanill, hairless Australian.

Fig. 26. The same in profile. ]

Let us turn from a tribe of which the existence is still dubious, to consider the portraits we subjoin of a man and woman, aborigines of Queensland, in a district watered by the Ballone. These are Aidanill, the brother, and Dewan, the sister, members of a hairless family. The indefatigable Miklucho-Maclay went to Gulnarber, 140 miles from Tulba, in order to examine them, and took the photographs from which our illustrations are taken.[21]

A likeness to the chimpanzee, when deprived of its hair, may be traced in the keel or roof-shaped form of the skull; in the prominence of the supra-orbital arches; in the deep depression between the forehead and nose, of which only the centre of the bridge has a slight vertical elevation; in the broad, flattened nostrils, bounded by deep furrows; in the wide, fleshy mouth, and the large, laterally projecting ears. Gratiolet and Alix give such a head in their treatise on _Troglodytes Aubryi_ (Figs. 25, 26, 27). When we add to this the dark brown skin, the deeply furrowed countenance, and the dark brown eyes, as they are described by Miklucho-Maclay, the external resemblance between many of the Australian aborigines and apes becomes more marked.

[Illustration: Fig. 27.--Dewan, Aidanill’s sister.]

Projecting ears are common among men of different races, and I have observed them in Europeans who are otherwise well formed. Even in this latter case the effect is ape-like. Much has been said of the resemblance which may often be observed between the human ear and that of apes. It is admitted that hardly any part of the organism varies so much in its characteristics as the external ear. This is the case with anthropoids, and almost more frequently with men. Individuals of all nations are found with defective development of this or that characteristic helix, angle tragus, notch concha, and fossa, with lobules imperfectly formed or altogether absent. I have frequently observed such misshapen ears, which vary from the perfect type, and bear a certain resemblance to the ear of apes, among the hard-featured peasantry of Germany, Switzerland, France, Italy, and Poland, who cannot be said to count beauty as part of their inheritance. In Africa I found this defective formation more common among the Maltese, Greeks, and Turks who were living in the country, than among the fellaheen, Berbers, and negroes. The latter have been unjustly charged with the possession of “hideous ape-like ears,” whereas, among the African races, these organs are, in the majority of cases, of a pleasing form. With respect to the Australian blacks, and to the Malay, Mongolian, and Indian races, I cannot rely on my personal observation. According to my very limited experience, there is much individual variation among these races, and ears of the hideous, ape-like formation might be sought for with success. The specific resemblance to apes can, indeed, only be ascertained by one who is accurately acquainted with the organism of these animals. These and similar ideas are often expressed by the unlearned, who do not really understand the characteristics in question.

Darwin speaks of the anthropoid form of the ear in the chimpanzee and orang.[22] “The ears of the chimpanzee and orang are curiously like those of man, and I am assured by the keepers in the Zoological Gardens that these animals never move or erect them, so that they are in an equally rudimentary condition, as far as that function is concerned, as man. Why these animals, as well as the progenitors of man, should have lost the power of erecting their ears, we cannot say. It may be, though I am not quite satisfied with this view, that owing to their arboreal habits and great strength they were but little exposed to danger, and so during a lengthened period moved their ears but little, and thus gradually lost the power of moving them. This would be a parallel case with that of those large and heavy birds, which from inhabiting oceanic islands have not been exposed to the attacks of beasts of prey, and have consequently lost the power of using their wings for flight.

“The celebrated sculptor, Mr. Woolner, informs me of one little peculiarity in the external ear which he has often observed both in men and women, and of which he perceived the full signification. His attention was first called to the subject whilst at work on his figure of Puck, to which he had given pointed ears. He was thus led to examine the ears of various monkeys, and subsequently more carefully those of man. The peculiarity consists in a little blunt point, projecting from the inwardly folded margin, or helix. These points not only project inwards, but often a little outwards, so that they are visible when the head is viewed from directly in front or behind. They are variable in size and somewhat in position, standing either a little higher or lower; and they sometimes occur on one ear and not on the other. Now the meaning of these projections is not, I think, doubtful; but it may be thought that they offer too trifling a character to be worth notice. This thought, however, is as false as it is natural. Every character, however slight, must be the result of some definite cause; and if it occurs in many individuals deserves consideration. The helix obviously consists of the extreme margin of the ear folded inwards; and this folding appears to be in some manner connected with the whole external ear being permanently pressed backwards. In many monkeys, which do not stand high in the order, as baboons and some species of macacus, the upper portion of the ear is slightly pointed, and the margin is not at all folded inwards; but if the margin were to be thus folded, a slight point would necessarily project inwards and probably a little outwards. This could actually be observed in a specimen of the _Ateles beelzebuth_ in the Zoological Gardens; and we may safely conclude that it is a similar structure--a vestige of formerly pointed ears--which occasionally reappears in man.”

[Illustration: Fig. 28.--Human ear.]

I subjoin an illustration of the human ear, in which the pointed tip mentioned by Darwin may be easily discovered. This point may also be perceived in the ears of anthropoids, and especially in those of the orang-utan. Meyer has attempted to show that this Darwinian pointed tip is only due to the abortive development of part of the helix, and in this case we should not regard the occurrence as an ape-like pointing of the helix, but rather as its partial interruption owing to the pathological condition of that organ.[23] In a later edition of his work, Darwin admits, in reply to Meyer, that this explanation may apply to many cases in which there are several very small points, or when the whole of the helix is sinuate. In one case, photographed by Darwin, the prominence was so large that, if we were to assume with Meyer that the ear would have been normal if the cartilage had been uniformly developed along the whole extent of the helix, the latter must have occupied a third part of the ear. Two cases were mentioned to Darwin in which the upper edge of the ear had no inner fold, and was so pointed that it was very like that of an ordinary mammal. The ear of the fœtus of an orang given in Darwin’s illustration appears to be pointed, although in the adult animal that organ is very like the human ear. The Darwinian tip may also be seen in the fœtus of an orang described and illustrated by Salvatore Trinchese in the _Annali del Museo civico di Storia Naturale di Genova_ (1870). The tip of the helix is pointed in very young individuals of the gibbon species, especially in _Hylobates Lar_. Among the lower apes the pointed ear is very common (see Fig. 29).

[Illustration: Fig. 29.--Magot (_Innuus ecaudatus_).]

The eyelids of anthropoids greatly resemble those of man in their structure. In adult gorillas and chimpanzees there is always a semilunar fold (_plica semilunaris_) corresponding to the _membrana nictitans_, or third eyelid of birds. In man there exists, instead of this, only a rudimentary apparatus, the _caruncula lachrymalis_. In some individuals it attains to a considerable size, as I have observed in the fellaheen, Berbers, Shillook, and other tribes. On the other hand, the conversion of the caruncula into a true, although only rudimentary, _plica semilunaris_ has not been observed by me in the human eye. Miklucho-Maclay describes the caruncula in Melanesians (the Papuans of New Guinea), in the Orang-Sakay (of the Malay peninsula), and in the Mikronesians (of the island of Japan and of the Palau archipelago), as two or three times as wide as that of the average European.[24]

The eye of the young male gorilla which was kept alive in the Berlin Aquarium from 1876–77 was carefully examined by me in June, 1877. I found that the sclerotic membrane of the eyeball was whitish, surrounded by a dark brown ring. A second darker ring, sharply defined, surrounded the cornea. The iris was of a yellowish brown. The sclerotic membrane, however, gradually deepens in colour so as to give the effect of a uniform dark brown. The iris retains a light brown colour for a longer period, but it darkens with age. In an aged animal there is no brightness in the eye, except from reflected light. In the chimpanzee the iris is light brown, verging on yellow; and this is also the case in the orang.

The expressionless, indifferent look of anthropoids has often been observed, and undoubtedly chimpanzees and orangs generally gaze placidly before them. I have, however, observed an animated expression in the eyes of the former species, and W. L. Martin has also observed a flash and brightening of their eyes. I shall never forget the expression of malicious anger in the eyes of the female animal Mafuca, at Dresden, as soon as she was teased. The expression of the eyes of the gorilla in the Berlin Aquarium also changed frequently, especially when he was about to perform some mischievous trick, or when he was provoked to anger. The expression of this animal was very human, but necessarily it could only recall the darkly coloured eyes of negroes and other black races. In 1876 there were two very young orangs in the Berlin Aquarium, one hairy and the other hairless. These animals clung together in a close embrace. If they were separated, their eyes became bright and restless, and they again sought to embrace each other while uttering plaintive cries. On tickling one of the animals under the chin, it made a most absurd grimace, and its eyes brightened, as Martin has observed in similar cases. The eyes of the gibbons which I have observed had a thoroughly mild and placid expression, rarely animated by any fire.

The instance we have mentioned of hairless Australians is the more remarkable since these aborigines are for the most part distinguished for their luxuriant growth of hair. The Australian blacks and the Ainos of Yedo are, as a rule, perhaps the most hairy races in the world. It is known, however, that in all countries and climates exceptional cases are found of individuals whose bodies are wholly or partially covered with hair, and these conditions sometimes affect whole families. Interesting historical and morphological researches respecting these hairy men have recently been made by von Siebold, Ecker, Virchow, Bartels, and Ornstein. In many of these cases we are presented with decidedly brute-like phenomena. The Mexican woman Julia Pastrana displays the strongest resemblance to apes. Other hairy men remind us at the first glance of some of the canine species. In all races the women are less hairy than the men. Darwin states that in the females of some species of apes the under side of the body is less hairy than in the males, and this is also the case with anthropoids, especially with the chimpanzee.

The beard is, as we know, common to man and apes. Among apes it is more strongly developed in the male than in the female, and this is also the case in the human species. Darwin points out that the growth of the beard both of men and apes occurs at the period of their sexual maturity, and also that there is a remarkable parallel between men and apes in its colour. For when the human beard varies in colour from the hair of the head, which is frequently the case, it is, without exception, of a lighter, and generally of a reddish hue. Darwin observed this in England, and Hooker found no exception to the rule in Russia. J. Scott carefully observed the numerous races which are to be found in Calcutta, as in other parts of India, namely, the two Sikh races, the Bhoteas, Hindus, Burmese, and Chinese. Although most of these races have very little hair on the face, Scott found that in all cases without exception, in which there was any difference in colour between the hair of the head and the beard, the latter was of a lighter shade. In apes the colour of the beard often differs widely from that of the hair of the head, and in such cases it is always of a lighter shade, often white, sometimes yellow or reddish.

[Illustration: Fig. 30.--Capucin ape (_Cebus capucinus_).]

“It is well known,” says Darwin, “that the hair on our arms tends to converge from above and below to a point at the elbow. This curious arrangement, so unlike that in most of the lower mammals, is common to the gorilla, chimpanzee, orang, some species of Hylobates, and even to some few American monkeys. But in _Hylobates agilis_ the hair on the forearm is directed downwards or towards the wrist in the ordinary manner; and in _Hylobates lar_ it is nearly erect, with only a very slight forward inclination; so that in this latter species it is in a transitional state. It can hardly be doubted that with most mammals the thickness of the hair and its direction on the back is adapted to throw off the rain; even the transverse hairs on the forelegs of a dog may serve for this end when he is coiled up asleep. Mr. Wallace remarks that the convergence of the hair towards the elbow on the arms of the orang (whose habits he has so carefully studied) serves to throw off the rain, when, as is the custom of this animal, the arms are bent, with the hands clasped round a branch or over its own head. We should, however, bear in mind that the attitude of an animal may perhaps be in part determined by the direction of the hair; and not the direction of the hair by the attitude. If the above explanation is correct in the case of the orang, the hair on our forearms offers a curious record of our former state; for no one supposes that it is now of any use in throwing off the rain, nor in our present erect condition is it properly directed for this purpose.”[25]

Darwin also remarks that it is erroneous to deny that apes have eyebrows. In fact, long bristly eyebrows are present in all anthropoids--not growing thickly together like those of men, but scattered among the shorter and thicker growth of hair which clothes the parts above the orbits; nor do they maintain any definite direction. In the white-handed gibbon, these eyebrows are remarkable for their length and stiffness. A growth of hair corresponding to eyebrows may, indeed, be observed above the upper eyelids of all mammals, including seals and pachydermata. On the upper lip of gorillas, chimpanzees, and orangs we may also observe a number of somewhat longer, stiff, and bristly hairs which stand apart from the otherwise short hairs on the lips, and give the impression of a cat’s “whiskers.” In _Hylobates albimanus_ I observed that these _vibrissæ_ attain to a considerable length (Fig. 10).

The external form of the trunk of anthropoids, taken as a whole, does not greatly differ from that of man. We have not, indeed, the well-formed human torso, with its graceful lines; and the formation of the posteriors, together with a want of expansion about the hips, displeases us in its departure from the human type (see Figs. 1 and 6). We shall not be disposed to compare the torso of the Apollo Belvedere, or of the Olympian Hermes with that of a gorilla or chimpanzee. Yet the torso of a powerful male gorilla, from which the hair has been removed, may be favourably compared with that of one of the large-bellied, lean-armed weaklings who are everywhere to be found as living caricatures of the human species.

The neck of anthropoids is generally short and thick. In the gorilla that part of the body has a great backward convexity, owing, as we have said, to the great development of the spinous processes of the cervical vertebræ, and of the muscles attached to them. A short, thick throat, and considerable development of the neck, a bull-neck, as it is called, is also not unfrequent in man. This peculiarity is sometimes supposed to be one of the national characteristics of the African blacks. Burmeister says that “the negro’s thick neck is the more striking, since it is generally allied with a short throat. In measuring negroes from the crown of the head to the shoulder I found the interval to be from nine and a quarter to nine and three-quarter inches. In Europeans of normal height, this interval is seldom less than ten inches, and it is more commonly eleven inches in women, and twelve in men. The shortness of the neck, as well as the relatively small size of the brain-pan, and the large size of the face may the more readily be taken as an approximation to the simian type, since all apes are short-necked, and the relative distance of these animals is somewhat further from the negro than that of the negro from the European. This shortness of the neck in the negro explains his greater carrying power, and his preference for carrying burdens on his head, which is much more fatiguing to the European on account of his longer and weaker neck.”[26]

Burmeister’s assumption on this subject is, however, much too general. It does not apply to many of the negro races--at any rate, not to those of the Upper Nile valley. A long, thin neck is the characteristic of the Funje, Shillooks, Denkas, Baris, and other large tribes of those regions. Among these people the interval between the top of the head and the shoulder is from ten to eleven, and even from eleven to twelve inches (240 to 260 mm., and 260 to 286 mm.). Burmeister has been thinking exclusively of the Brazilian blacks. Yet I am unable to trace the typical short neck, either in the well-known portraits of slaves by Maurice Rugendas,[27] or in the collection of photographs of Brazilian negroes which is in my possession. This characteristic is also absent, even in many portraits of West African and Mozambique blacks, tribes from which the slave population of Brazil has been chiefly drawn. Many Mongolians, Malays, Papuans, and Polynesians have short, thick necks, but this characteristic is more rare among the American aborigines and among Europeans. If we are to recognize an approximation to the simian type in this formation, it is one common to several nations, and it is not confined only, nor even chiefly, to the negro races.

The remarkable elongation of the upper limbs of anthropoid apes cannot be compared with the length of the corresponding limbs in men. For although among negroes and the members of other primitive peoples we may occasionally observe unusually long arms, yet these are individual peculiarities which are also found among Europeans, and cannot be counted among racial characteristics.

[Illustration: Fig. 31.--Hand of a very aged male gorilla.]

The hand of the orang and the gibbon is too long and narrow to be directly compared with the human hand. The chimpanzee and the gorilla, especially the latter, have hands more like those of man. In the case of an adult male gorilla the first glance at this member reminds us of the knotty fist of a black dock labourer or lighterman, like those who, at Rio de Janeiro, Bahia, or La Guayra, lift the heavy bags of coffee and place them on their heads or on their herculean shoulders. Much has been said of the enlargement of the connective skin between the bases of the fingers of a negro hand, and of the pointed extremities of the fingers. Van der Hoeven, in his well-known treatise, _De Natuurlijke Geschiedenis van den Negerstam_, has described and drawn the hand of an Ashanti boy, formed in this manner. Hence there is a disposition to recognize in this peculiarity an important characteristic of the negro race. As in the hand of the gorilla, the connective web between the bases of the fingers is also extensive, and the ungual phalanges taper at their extremities, there is also an inclination to ascribe an expressly anthropoid character to the negro hand. Yet this structure of the fingers is by no means universal among the negroes. An enlargement of the connective web is not indeed uncommon, but its extent varies considerably. Nor is it wanting in the fingers of other races. An attentive observer will be able to trace it in the labouring population of country districts in Europe. I have myself frequently observed this characteristic in Canton Wallis, and in the Lombard and Genoese provinces, through which I travelled on foot in 1869 and 1871, when I devoted special attention to this point. In Fig. 32 I give a negro hand of a type which seems to be common among the blacks in the inland districts of North-eastern Africa. It can hardly be denied that the form of this hand, which is certainly not flattered, possesses the characteristics of a thoroughly human organization.

[Illustration: Fig. 32.--Hand of a Hammegh from Roseres, on the Blue Nile.]

With respect to other primitive peoples besides negroes, we have not at present sufficient information, and we ought therefore to beware of premature generalization. The thin shanks, with imperfectly developed calves, found among many primitive races, and especially among the African and Australian blacks, are often and not unjustly adduced as an instance of their ape-like formation. In fact, the general uncomeliness of these parts in the races in question is one of their significant characteristics.

[Illustration: Fig. 33.--Satan’s ape (_Pithecia Satanas_). Shows the formation and mode of using the feet in apes of the New World.]

The anthropoid foot resembles in structure those of other apes, including those of the New World, and as a rule it differs from the human foot in the flexibility of the great toes. It has, however, been justly observed that many individuals of different races have been able to use the great toe almost as if it were a thumb. Such persons may be found everywhere. Men who have been born without arms, or who have been deprived of them during life, have been able to use their feet like hands, as some compensation for this privation. The most surprising instance of our time has occurred in the violinist without arms, whose performances are heard in various continental capitals. Another, mentioned by Bär, was able to write with his feet. But even people who have the full use of their upper limbs can often grasp with the great toe as if it were a thumb, so as to pick up small objects from the ground, or draw them towards them. Constant practice in such feats produces a certain dexterity. Negroes, Malays, Polynesians, and Indians make use of their outstretched great toes in climbing with as skilful a gripe as our schoolboys and sailors are also able to do in gymnastics, or in climbing up the masts. Among such people the distinction between the foot of man and apes is less marked, since, even when at rest, the great toe is apt to be somewhat detached from the others. This may be seen in A. Buchta’s excellent photographs of individuals of the Central African tribe, the Makraka. Haeckel justly observes that there is no marked physiological distinction between the hand and foot which can be established on a scientific basis. In order to make such a distinction it is necessary to consider their morphological characteristics.[28]

[Illustration:

Fig. 34.--Human skull. _a_, Nasal bone. _b_, Upper jaw. _c_, Lower jaw. _d_, Occipital bone. _e_, Temporal bone. _f_, Parietal bone. _g_, Frontal bone. _h_, Malar bone. ]

_Structure of the skeleton._--In comparing the skulls of anthropoids with those of men, we should, in the case of the gorilla, chimpanzee, and orang-utan, content ourselves with young specimens rather than with the skulls of adults. In aged apes of these species, the colossal development of the bony crests of the skull, as well as that of the jaws, the prominence of the orbital rim, and the flattening of the occipital bone, present distinctions of such a searching character that we are greatly hindered in the pursuit of the comparative method. But during the process of development the anthropoid skeleton admits of a direct comparison with that of man. In a young animal the rounded skull suggests a parallel between it and the human head. It must be admitted that we find, especially in primitive peoples, many human skulls which in their whole plastic form differ little from the skulls of young gorillas, chimpanzees, and orangs. Even in the way the occipital bone is rounded off, young anthropoids and men are often found in a similar stage of development. The squamous occipital portion in a young negro, Papuan and Malay, is indeed often flatter and more bevelled than it is in a young gorilla or chimpanzee.

We must not, however, assume that the two individuals brought into comparison are of precisely the same age, since such a point cannot easily be ascertained, even when subjects for examination are afforded by one of our larger museums. Savages are seldom able to give their precise age, and the attempt to do so often relies on insufficient data. The direct examination of the skull will afford some information on this point; but the conditions of growth in anthropoids are not so well known as to admit of an accurate estimate. We have to rely on the state of the teeth, on the stage at which the development of the bony crests has arrived, etc., in order to form an approximate estimate of the age of the skull.

On the squamous occipital portion the arrangement of the curved lines which are the boundaries to the attachments of the cervical muscles, is common to men, to anthropoids, and to other apes. Only indications of these lines are to be found in the lower order of mammals. In the human skull there is sometimes a formation belonging to the squamous occipital portion which has a distinctly pithecoid or ape-like character. This is the occipital swelling we have already described (_Torus occipitalis transversus_), which may be either enclosed by the two upper curved lines, or lie between these and the central curved lines, or may be altogether in the region of the latter. This swelling extends in a gradual manner above and below its bony support. Its edge may be more or less sharp, more or less like a crest in its development, wider or narrower, with or without a central eminence, but its appearance is always striking. In young male and female gorillas, orangs, and chimpanzees this formation represents the completely formed transverse occipital crests, which are found for the most part in aged male animals of these species. These swellings may also be observed on the skulls of adult men of all times and all nations. They are by no means rare in the skulls which are in ordinary use at the Berlin School of Anatomy, and they are remarkably common in many groups of skulls. They are frequent among the skulls, for the most part without their lower jaws, which the late Dr. Sachs disinterred in a Mohammedan burial-ground of the thirteenth century, near Cairo. These are the remains of Mohammedans of different ranks, but, for the most part, of the peasantry or fellaheen. Ecker was able to trace the sagittal crest in the skulls of Australian males, while it is absent in the females. Similar indications of the bony crest have been observed by me in the roof-shaped or scaphocephalic skulls of many negroes, but in these cases I am not aware whether there is a corresponding distinction of sex. It can hardly be denied that this bony prominence is a human characteristic.

Broca has given the term pterion to the H-shaped connection formed by the sutures between the parietal bone, the greater wing of the sphenoid bone, the squamous portion of the temporal bone, and the frontal bone. One of the most common disturbances in the symmetry of the connecting suture, as we have already briefly mentioned, arises from the insertion of a frontal process of the squamous portion of the temporal bone between the lower angle of the parietal bone, the fore-part of the frontal bone, and the greater wing of the sphenoid bone. This process of the temporal bone varies in size, and may occur on one or both sides. A similar formation is common among gorillas, chimpanzees, macacas, magots (_Inuus_), and baboons.[29] It is less frequent among orangs,[30] gibbons, marmosets, and American species (howlers, hooded apes, etc.).

Virchow and W. Gruber have agreed in representing this frontal process as theromorphological--that is, as a characteristic of the lower animals, and more especially of apes. Virchow has found this abnormal formation of the skull to be more common in some races than others. None of those in whom it occurs appear to belong to the Aryan races, and the existence of this process and stenocrotaphy, or temporal stenosis, seem to be due to a defective development of the greater wing of the sphenoid bone, and to the compression of the bones in its vicinity, by which the whole temporal region is contracted. This is a characteristic of the lower, but by no means of the lowest, races of men.

Stieda, Hyrtl, Gruber, and Calori have sought to controvert the fact that this temporal process is a characteristic of the lower races. Stieda asserts that it may occur exceptionally in all races of men.[31] He himself, aided by Anutschin, has ascertained the existence of this anomalous pterion on more than 10,000 human skulls, and he has also received information from others. He considers the frequency of this frontal process in man to be theromorphological, or indeed pithecoid. According to Anutschin, this anomalous condition is not equally common in all races. In the dark-skinned and woolly-haired races (Australians, Papuans, and negroes) the frontal process is most widely diffused; it is less frequent among Mongolians and Malays; and among Americans and white men its occurrence is from five to six times more uncommon than in the black races. Sometimes the frontal process occurs on the intercalary bone (_Ossa epipterica_), which is fused into the squamous portion of the temporal bone; and sometimes the process grows out of the squamous portion of the temporal bone. These imperfect processes or intercalary bones are not regarded by Anutschin as pithecoid, since they are more rare in apes than in men. Schlocker has sought to show that the frontal process of the squamous portion of the temporal bone, the less common temporal process of the frontal bone, and the temporal intercalary bone (_Ossa epipterica_) are of equal value from the genetic point of view.[32] This author regards the frontal process and the immediate connection of the frontal and squamous portion of the temporal bones, as theromorphological characteristics, but he does not believe the occurrence of this process to be restricted to the lower races.[33] This is also the opinion of Ten Kate. However this may be, the establishment of this theromorphological formation is important. Its immediate value as a contribution to the theory of the origin of species remains, as we shall presently see, even if we cannot trace it through intermediate and lower types.

In the great prominence of the supra-orbital ridges which has been observed in some pre-historic human skulls, a likeness to the corresponding feature in anthropoids has been traced. And indeed there is such a likeness, especially to the female chimpanzee, in the well-known Neanderthal skull, which is very dolichocephalic, with prominent supra-orbital arches, only divided from each other by a shallow depression. In the same skull the development of the supra-orbital ridges is related to that of the frontal sinuses. In this pre-historic specimen--which, by the kindness of Professor Schaafhauser, I was able to examine closely at the congress of anthropologists at Berlin in 1880--the forehead retreats in a marked manner towards the flattened region of the crown. De Quatrefages and Hamy say that the skull is both flattened and long (dolichoplatycephalic). The temporal ridges are not only very marked, but they approach each other in the region of the coronal arch (Fig. 35). This also occurs in the adult female chimpanzee, as well as in the young male gorilla, in the aged female orang, and in the gibbon.

[Illustration: Fig. 35.--The Neanderthal skull. A. In profile. B. A front view.]

It may here be observed that our men of science differ widely in opinion respecting the origin and ethnological significance of the Neanderthal skull, of which I will cite only a few instances. Pruner regards it as the skull of an idiot.[34] Virchow considers the specimen, and the similar one from Kailykke in the Copenhagen Museum, as an altogether individual formation,[35] a typical form modified by disease,[36] in other words, a pathological skull.[37] King regards the skull as one belonging to one of the primitive races.[38] Schaaffhauser has, indeed, endeavoured to make an artistic portrait of such a primitive man. Spengel holds that skulls which are “Neanderthaloid” in form are to be found chiefly in Europe.[39] If Huxley says decidedly that the Neanderthal skull can by no means be regarded as the remains of a human being which was a link between man and apes. At most this discovery only proves the existence of a man whose skull reverted in some respects to the simian type, just as a carrier or tumbler pigeon may sometimes display the plumage of their original ancestor, the rock-pigeon (_Columbia livia_). And although the Neanderthal skull is more like that of the ape than any other human skull with which we are acquainted, yet it is by no means so isolated as it at first appears, but is rather the ultimate expression of a series which may be gradually traced back from the highest and most fully developed type of human skulls. On the one side it approximates to the flattened Australian skulls, from which other Australian forms gradually lead to skulls which rather resemble the type afforded by the Engis skull. On the other side, it is still more closely allied with the skulls of certain ancient races which were either contemporaries or successors of those which dwelt in Denmark during the Stone Age, people whose kitchen middens have been discovered in that country.[40]

Huxley justly observes that some of the skulls drawn by Busk, and taken from the tumuli of Borrely, resemble the Neanderthal skull, especially in the abruptly retreating forehead. Some other European skulls may, within certain limits, be compared with the Neanderthal skull, as, for instance, those found at Brüx, Staengenaes, Olmo, Louth, Clichy, Bougon, Cro-Magnon, Grenelle, Furfooz, Engisheim, Cannstadt, and Toul. These all present interesting peculiarities of structure--strongly developed supra-orbital arches, a retreating forehead, a flattened crown, etc., although none of them are so remarkable in these particulars as the Neanderthal skull. It has not, however, yet been proved that this skull represents a definite racial type, and it seems more probable that it was simply an individual form.

The skulls of the Australian aborigines are, as Spengel justly observes, distinguished from the Neanderthal skull, and from others of like character, by their pronounced scaphocephalism. On the other hand, they have the prominent supra-orbital arches, the retreating forehead, the skull compressed in the temporal region, the prognathous countenance, relatively shorter than that of Europeans, and in all these respects the skulls of the Australians greatly resemble those of anthropoids. If, for instance, we turn to the illustration given by de Quatrefages and Hamy of a skull procured from Camp-in-Heaven, Arnhem’s Land, North Australia, and also Dr. Schadenburg’s negro skull, the most determined sceptic must be struck by their resemblance to the anthropoid skull.[41]

Similar characteristics to those which we have already mentioned as distinguishing the structure of the Australian skull, enable us to determine the anthropoid character of the skulls of many individuals belonging to the dark-skinned African races. These consist chiefly in the retreating forehead, the flatness and compression of the coronal arch, the pronounced prognathism, and the obtuse angles of the lower maxillary bones, which may be noted in so many negro skulls. On the other hand, the prominence of the supra-orbital arches is, as a rule, less marked in African races than in anthropoid species. There are specimens, however, as, for instance, the Congo skull given by de Quatrefages and Hamy,[42] which give an overwhelming impression of anthropoid characteristics. And we find the same to a surprising degree in the skulls of intelligent, warlike, and light-skinned races of Central and Western Africa, and as the Monbuttre, Haussaua, Bakale, Fan, etc. This character may be discovered in all races of men, and especially among the Papuans and some African negroes.

A mutual approximation of the temporal ridges in the coronal region may be observed in the skulls of various nations. This formation is most frequent in the long-headed negro and Papuan skulls. In these cases it is generally allied with the shortness of the interval between the sides of the skull, taken in its transverse diameter (stenocephalism).

In an adult female chimpanzee, the parietal bones often rise abruptly towards the sagittal suture, and in its vicinity there arises a longitudinal bony prominence, of which the sides pass gradually into the external surface of the parietal bones. The sagittal suture sometimes remains intact, and is sometimes included by this process. This produces a modified development of the so-called keel-shaped skull (_scaphocephalus_). Such a formation may be often observed in negroes and Papuans, and more rarely in the skulls of other races. The occurrence of a divided malar bone in human skulls, especially in those of the Ainos and Japanese, has been considered to be theromorphic, since it is occasionally observed in the skulls of apes.[43] I have myself, in a very few instances, found obscure traces of such a formation among anthropoids.

In 1863 Boucher de Perthes found at Abbeville half of a human lower jaw deposited in a black layer of clay and sand mixed with iron, and lying on the chalk. As far as we can judge from illustrations which are for the most part imperfect, there was nothing remarkable about it except its abruptly retreating ramus (Fig. 36), but the specimen aroused great attention at the time, and it was assigned by many intelligent observers to the primitive men of the diluvial period. Unfortunately it was afterwards proved to be a gigantic imposture.[44]

[Illustration: Fig. 36.--Lower jaw of Moulin-Quignon.]

[Illustration: Fig. 37.--Naulette lower jaw.]

[Illustration: Fig. 38.]

This is not the case with the lower jaws of Naulette, Aurignac, and Arcy, which are undoubtedly genuine and of great antiquity. The Naulette jaw is, indeed, very imperfect, yet we can trace the construction of the symphysis of the chin, which provokes comparison with the lower jaws of many anthropoids, especially those of the gorilla and chimpanzee (Fig. 37). The resemblance consists chiefly in the uprightness of the anterior surface, and especially of the body of the maxillary bone. In anthropoids this surface of the bone retreats from the row of teeth backwards and downwards to the lower edge of the body of the maxillary bone (Fig. 38); and in the Naulette specimen, as well as in the lower jaws of some modern Papuan skulls (of New Hebrides and elsewhere), there is a certain approximation to the simian type. A fossil ape (_Dryopithecus Fontanii_) has been found in the Middle Miocene of Saint-Gaudens, assumed to be one of the higher anthropoids, and in this case the jaw is only slightly retreating. Gaudry considers that the _Dryopithecus_ was about the size of a man. The incisor teeth were small. The cusps of the back molar teeth were less rounded than in Europeans, and more like those of Australians. It has been surmised, although the fact cannot be established, that the last molar teeth were only cut after the canine teeth, as is the case with the human wisdom teeth. Gaudry gives the illustration of the lower jaw of a Tasmanian, from eleven to twelve years old, together with that of _Dryopithecus Fontanii_. In the human jaw the first molar tooth is larger than in the _Dryopithecus_, while the canine tooth and the pre-molars are much weaker. This distinction is important, since the smaller size of the front teeth is connected with the slight projection of the face, which is always a sign of human superiority. Although the canine tooth of the _Dryopithecus_ is broken, we can see that it must have been considerably higher than the other teeth, and indeed the canine teeth of the male animal must have been very powerful. There is also a slight prominence in the teeth of this ape, which is absent in those of men. _Mesopithecus_, from the Miocene of Pikermi, Attica, was an ape less closely resembling the anthropoids. In the structure of the head it resembles the slender ape (_Semnopithecus_), and in the structure of the limbs it is like a macaca (_Macacus_). Gaudry believes that Sansan’s _Pliopithecus_ was related to the gibbon. An ape of the size of the orang-utan, which belongs to the slender apes (_Semnopithecus sub-himalayanus_),[45] was found by Baker and Durand in the Miocene of the Sewalik mountains.

In the comparative study of the human organization, and that of anthropoid apes, it is important to examine sections, and especially longitudinal sections, of characteristic skulls.[46] Virchow has caused drawings to be made, from specimens in the Berlin Museum, of a gorilla, a chimpanzee, an orang-utan, and an Australian woman. The gorilla’s skull, when compared with the Australian’s, is so narrow that it looks as if compression had been applied to it; and yet the Australian skull is extremely small in comparison with that of men in general, since its cubic space is only 1150 ccm. In the gorilla[47]--at least in the old male, from which the drawing is taken--the immense size of the frontal sinuses, and the swellings which cover them, together with the strongly developed jaw, increase the impression of size. But, as Virchow observes, “all which adds to the size of the skull is bestial, and not human.” It is much the same in the orang-utan. Only in the chimpanzee the cubic space of the skull may be somewhat more favourably compared with that of the human skull. It approaches in size to that of a microcephalic native of the Rhein-Pfalz (of which an illustration is also given), which ranks a good deal below the Australian skull, and approximates more closely to the simian type. The internal space of the skulls of an adult female gorilla or orang may also be more favourably compared with those of men.

[Illustration: Fig. 39.--Sagittal section through the skull of a bam-chimpanzee.]

We have already mentioned the presence of extensive sinuses and cells in the skulls of anthropoids, exceeding those of human skulls, and this is apparent in the accompanying illustration of a longitudinal section of the skull of a chimpanzee carried through its centre (Fig. 39). The length of this skull between the nasal partition and the most prominent part of the occipital bone is 128 mm.; that of the internal space is 108 mm. 10 mm. of this difference is due to the depth of the frontal sinuses, and the rest is owing to the thickness of the bony part of the skull. In an aged male gorilla, the first measurement is 153 mm., the second 115 mm. In another aged gorilla the measurements were respectively 183 mm. and 117 mm. In a still more aged male orang they were respectively 140 mm. and 114 mm. The comparative thinness of the centre of the squamous occipital portion is to be noted in the aged gorilla male. In the adult chimpanzee the large cells of the squamous portion of the temporal bone extend into this bone, and indeed without interruption into the parietal bone adjoining it. For such investigations the thin and light bones of individuals which have lived a wild life are more suitable than the heavy and fat specimens which have died after prolonged confinement.

Zuckerkandl has observed that among Europeans the orbital part of the nose, or that part which is between the orbits, is longer than the infra-orbital or lower part. In anthropoids the infra-orbital portion is considerably the longest, although only in adult animals. There are stages in the period of development in which these animals display the characteristics of an adult European, or indeed of a child. The proportions of the skulls of Malays take a middle place between those of Europeans and of apes. The growth of the infra-orbital part of the nose in the Malay does not equal that of apes, but in many cases it differs essentially from that of Europeans. Zuckerkandl makes a skilful attempt to establish this statement by statistics.

The same inquirer makes some interesting remarks on the comparative height and width of the orbits. He observes that the skulls of adult apes and men differ more in these respects than the young specimens of these organisms. The orbits both of a child and an adult, especially in the case of a European, are much more like those of a young ape than of an aged animal of the same species. In the chimpanzee and the orang-utan the proportions are the same as in men; that is, the width of the orbit exceeds its height. In man, this seems to arise from the exceptionally strong development of the supra-orbital ridge. It is most probable that in very young anthropoids the width of the orbit exceeds its height.[48] Zuckerkandl goes on to say that in anthropoids the height of the orbits is greater than their width, and that this difference increases with age. But this is not absolutely correct, for even in aged animals the proportions vary, and the height and width of the orbits sometimes, although rarely, remains the same.

In comparing the vertebral column in men and anthropoids, Rosenberg has sought to show in the embryo, that the first sacral vertebra assumes the form of a lumbar vertebra, and that in a later stage of development it is enclosed by the ilia, and anchylosed with the sacrum. The same author has proposed a theory of the homologous or genetic equivalents of the vertebræ, which we must now consider. According to this theory, as Welcker has observed,[49] the twentieth vertebra of an animal A is homologous to the twentieth vertebra of an animal B, the thirtieth vertebra of one animal to the thirtieth of another, although in one case it may be a lumbar vertebra, in another a pelvic vertebra, and in a third a coccygeal vertebra. The dorso-lumbar vertebræ of the lower apes have, in the case of men, their descendants, undergone a threefold metamorphosis, and, after their modification into sacral vertebræ, have assumed their fourth form as coccygeal vertebræ.

Froriep, a follower of Rosenberg, remarks that the lumbo-sacral vertebræ, _i.e._ those constituents of the vertebral column which form the transition from the lumbar to the sacral vertebræ, are invested with fresh interest by Rosenberg’s hypothesis. According to their position in the vertebral column, they are to be regarded as lumbar vertebræ, introduced too early or too late into the structure of the sacrum. If the twenty-fourth vertebra is assimilated with the sacrum, so as to form an upper promontory or outwork, this variety offers a point of transition to a future formation (?) in which this vertebra normally becomes the first sacral vertebra, and the column will now display twenty-three free vertebræ. If, again, this transition occurs in the twenty-fifth vertebra of the series, which thus becomes the chief sacral vertebra, this is, in Rosenberg’s opinion, a characteristic survival of the racial development, an atavism.[50]

According to Welcker’s theory, the chief sacral vertebra in one animal corresponds to the same sacral vertebra in another animal, whatever their number may be. The cervical vertebræ of one animal, which may be five, seven, or even eleven in number, correspond to the cervical vertebræ of another animal. The vertebral column of one animal corresponds to the vertebral column of another, taken as a whole, but not to two-thirds or three-fourths of that column. In accordance with the requirements of a given animal, that part of the bone which belongs to the sections of the breast and loins is more or less abundant, and the vertebræ are homologous in accordance with their region, and not with their number.

Holl has asserted that one vertebra is in close connection with the ilium, joined with it throughout its extent, and that this vertebra at the same time always appears to support the pelvis. This vertebra is, in normal cases, the first sacral vertebra, and the twenty-fifth of the series. It may be termed, as Welcker suggests, _vertebra fulcralis_. Such a main support is found, according to Holl, in every vertebral column, however anomalous its other conditions may be, and the only irregularity consists in its number in the series. This bone serves as a natural starting-point in our division of the vertebral column. The _vertebra fulcralis_ must always be regarded as the first sacral vertebra. It begins the series of sacral vertebra, and, on account of its subsequently important position, it must be regarded as primary. Holl finds that it is followed by four lower vertebræ, which are afterwards included with it in the sacrum. When in its primary condition the _vertebra fulcralis_ is twenty-fifth in the series, the twenty-fifth to the twenty-ninth vertebræ are included in the sacrum. When the _fulcralis_ is the twenty-sixth vertebra, the sacrum includes the thirtieth. Hence it follows that the sacrum is, from the first stages of its development, a formation which begins with the twenty-fifth or twenty-sixth vertebra, and includes four other vertebræ. Holl considers that the lumbo-sacral form of the last lumbar vertebra, which stands between the lumbar and sacral vertebræ, does not indicate a gradual transition into a sacral vertebra, but rather an arrest in its development.[51]

When we examine a human sacrum we see that its first vertebra, the twenty-fifth of the series, is formed like the lumbar vertebræ in its upper part, setting aside those portions of it which form part of the lateral masses of the sacrum. These lateral masses, which serve as a support to the ilia, owe most of their substance to the first sacral vertebra. Thus, since it has to support the whole weight of the pre-sacral vertebræ, it is in fact a true _vertebra fulcralis_.

Holl justly says that there are few instances in which the human _os sacrum_ consists of less than five vertebræ, and in no case are there less than four. In such a case the first sacral vertebra defines the pre- and post-sacral segment of the vertebral column.

In anthropoids the lower segment of the lumbar vertebral column is deeply sunk between the high, wide, and flattened ilia, which converge closely towards the vertebral column. In man these bones are not so much higher than the base of the sacrum, and their crests diverge more widely from the vertebral column. In the large apes the lateral masses of the sacrum are comparatively deeply set below their anchylosis with the pelvic bones. In an aged male gorilla, for instance, the transverse processes of the two lower lumbar vertebræ often extend to the hinder borders of the ilia, although the second of the lower lumbar vertebræ is somewhat higher than the top of the crest of the ilium. This is still more remarkably the case in an old male chimpanzee, in which the lowest lumbar vertebra seems to be wedged in between the two ilia. In a young male chimpanzee, and in the adult female, both the lower lumbar vertebræ are almost compressed between the upper segments of the ilia. In the orang the lowest lumbar vertebra is placed between the ilia. Out of the five sacral vertebræ the first and second are articulated with these bones.

In the gorilla the highest sacral vertebra, the twenty-fifth of the series, is the _fulcralis_. In this animal the first to the third sacral vertebræ form part of the connection with the crests of the ilia. In the chimpanzee the twenty-fifth is also the _vertebra fulcralis_, and from the first to the third are likewise connected with the ilia, but the third only to a limited extent; and in young males and in old females the connection is generally confined to the first and second sacral vertebræ. In the orang-utan the twenty-fourth vertebra is generally the _fulcralis_.

In the gibbon the twenty-fifth vertebra is usually the _fulcralis_. In the siamang I found that the fifth of the five lumbar vertebræ was between the ilia. Out of the five sacral vertebræ the first and second were articulated with the said pelvic bones. In _Hylobates agilis_ the fifth and sixth of the six lumbar vertebræ were between the ilia, and the first and second of the five sacral bones were articulated with these.

In the vertebral columns of the gorilla, the chimpanzee, and the orang we may observe an inconsiderable forward projection between the penultimate cervical and the second and third dorsal vertebræ. In the region below the second lumbar vertebra a similar forward projection may sometimes be observed. The so-called promontory at the entrance of the pelvis, that is, in the region developed between the lumbar and sacral vertebræ, which is remarkable in man, is only faintly apparent in anthropoids. The vertebral column is arched behind, since there is a dorsal curvature (see Figs. 17 and 23).

Aeby observes that the bodies of the vertebræ are tapering in the gorilla, and this is, in fact, the case. In climbing, or when he goes on all fours, the dorsal curvature of an anthropoid maintains its position. This curvature is still more apparent when the animal, in climbing, withdraws his body from the tree, mast, or whatever it may be, and bends forward his head. A similar dorsal curvature of the vertebral column may be observed in men who stiffen their hands and feet to climb up a tree or mast. If an anthropoid holds himself so erect as to be able to place his hands behind his head, the dorsal curvature of his spine is necessarily straightened, and indeed it becomes rather a ventral curvature.

The bony pelvis of anthropoids, with its high, narrow, and projecting ilia, and the lowest lumbar vertebræ deeply embedded between them, together with the sacral and coccygeal vertebræ, which directly remind us of the vertebræ of a rudimentary tail, present the points of unlikeness with the human skeleton in this part of the skeleton of these animals in the strongest light (comp. Figs. 40 and 41).

The bony thorax of anthropoids is distinguished from the human thorax in normal cases by the abrupt way in which it widens outwards. The thorax of the gorilla, and the widely diverging pelvic bones, which enclose the belly and give it a tun-shaped form, contrast with the graceful moulding of the corresponding parts of the human form.

Certain peculiarities in the structure of the bones of the shoulder-girdle and of the extremities of anthropoids, in which they differ from corresponding parts in the human structure, have been already mentioned.

With reference to the humerus of the gorilla, Aeby asserts that the head of the bone forms a cycloid, placed transversely, while in man its shape is that of the segment of a sphere. But I have pointed out in my treatise on the gorilla that there is a not inconsiderable variation in the form of the head of the humerus in these animals, and it is sometimes cycloidal or vertically-cycloidal, sometimes a segment of a true sphere. In the chimpanzee, orang, and gibbon this part of the humerus is always a segment of a sphere, while in man its form is not equally invariable. Aeby further observes that the transverse-cycloidal form of the head of the humerus in the gorilla justifies the inference that this animal, in the use of its fore-limbs, is accustomed to turn them transversely on their axis. But the direct observation of a living anthropoid, as well as the examination of its dead body, make it clear that the action of the ball and socket is remarkably free, and this theoretical surmise is contradicted by the perfection of the natural mechanism.

[Illustration:

Fig. 40.--Human skeleton.--_a_, Parietal bone. _b_, Frontal bone. _c_, Cervical vertebræ. _d_, Sternum. _e_, Lumbar vertebra. _f_, Ulna. _g_, Radius. _h_, Carpus. _i_, Metacarpus. _k_, Phalanges. _l_, Tibia. _m_, Fibula. _n_, Tarsus. _o_, Metatarsal bones. _p_, Phalanges. _q_, Patella. _r_, Femur. _s_, Os innominatum. _t_, Humerus. _u_, Clavicle. ]

[Illustration: Fig. 41.--Skeleton of an aged male gorilla.]

The excessive curvature of the forearm which we notice in the gorilla and the chimpanzee in their natural condition is rare in man, and when it does occur it must be regarded as an abnormal and pathological phenomenon.

The orang-utan always displays a ninth carpal bone, corresponding to de Blainville’s _os intermedium_ and Gegenbaur’s _os centrale carpi_. In a very young animal I found that this small bone was furnished with a peculiar point of ossification. The bony structure of the wrist is developed in the following succession:--First, the _os magnum_ and unciform bones; second, the scaphoid bone; third, the trapezium; fourth, the semi-lunar bone; fifth, the cuneiform bone; sixth, _os centrale carpi_; seventh, the trapezoid bone. The pisiform bone and the sesamoid bone, between the trapezium and the scaphoid bone, of which we shall speak presently in their relation to the muscular system, are at first simply cartilaginous.

Up to this time my search for this ninth carpal bone in the gorilla and the chimpanzee has been fruitless, since its occurrence is only exceptional. In the gibbon it is plainly inserted between the scaphoid, semi-lunar, trapezoid, and _os magnum_. Gegenbaur considers the _os centrale_ to be a true constituent of the wrist, dating from an earlier condition, but he has nothing to suggest as to its subsequent survival. Rosenberg has lately given an incontestable proof of the presence of this bone in the human embryo. It is generally absorbed again, but sometimes it persists, and may be found in an adult as a well-formed ninth carpal bone. Cases of the persistence of the _os centrale_ in man have been chiefly collected and published by the diligence of the Russian anatomist, Gruber. It is now suggested that there may also be indications of _os centrale_ in the carpus of embryos of the gorilla and chimpanzee, but up to this time materials for such researches have been wanting.

I cannot accept the theory that _os centrale carpi_ is merely a detached portion of the scaphoid bone. In a very young chimpanzee this bone is undoubtedly superficially indented with two transverse furrows, but the three segments display only one uniform development of bone. The distinct formation of _os centrale_, and its occasional appearance in man, testify that it has an independent existence. Rosenberg holds that this bone is not merely the _os centrale_ of mammals, but that it is homologous with the two _ossa centralia_ of the fossil _Enaliosauria_. It has become abortive in proportion to the reduction in size which has taken place.[52] There would be no great difficulty in tracing back this bone to remote types of vertebrate animals, even as far as the _Urodela_ (Wiedersheim) of Eastern Asia.[53] The persistence of this bone in man must be regarded as a reversion, not as an arrest, of development.

[Illustration:

Fig. 42.--Skeleton of human hand, back view. _a_, Scaphoid bone. _b_, Semi-lunar bone. _c_, Cuneiform bone. _d_, Pisiform bone. _e_, Trapezium. _f_, Trapezoid bone. _g_, Os magnum. _h_, Unciform bone. _l-l′_, Metacarpal bones. _m-m′_ and _nn_, Phalanges. ]

On the femur of several mammals, especially in the horse, ass, rhinoceros, and tapir, and more slightly indicated in the carnivora and other families, there is, in addition to the two great and small trochanters, a third, termed by Waldeyer _trochanter tertius_.[54] Such a formation, low, blunt, and generally placed at the top of the outer ridge of the superior bifurcation of the _linea aspera_, may be observed in human skeletons of all races, but is either absent in anthropoids or only faintly indicated. Virchow justly regards its presence as theromorphic, but not as a characteristic of savage or lower races.[55]

The human tibia displays in some instances a compression or lateral flattening of its shaft or centre-piece, so that its transverse diameter is quite out of proportion to its depth. Such a tibia is termed sword-bladed, or platycnemic. Bones of this form have been chiefly discovered in ancient deposits, as, for instance, at Gibraltar, at Perthi-Chwareu, in Wiltshire, in Lozère, at Clichy, at Saint-Suzanne (Sarthe), and especially at Cro-Magnon (Fig. 43), Janischwek, etc.

A similar formation has also been observed among men belonging to cultured races, both of ancient and modern times. Virchow, for example, discovered such bones in Transcaucasia (of the third and fourth century of the Christian era) and at Hanai-Tepe in Troas. All the large schools of anatomy in Europe contain specimens of tibiæ, which are to some extent platycnemic. These are also observed in the skeletons of primitive peoples of our time, as for example in the Negritos, Kanakas, and other African races. While some scientific men regard these bones as the result of an unhealthy condition, and the effect of rachitis, others more justly ascribe them to a vigorous exercise of the muscles in a one-sided direction. The idea expressed by Busk and others, that the platycnemic tibiæ discovered in ancient sites of Europe have belonged to a degraded race diffused over the whole continent, is contradicted by the wide diffusion of this characteristic, even in modern times. And it is doubtful whether platycnemy is absolutely restricted to the lower races. At Janischewek, Virchow found an extremely platycnemic tibia, exhumed from a kujawish grave of the Stone Age, which belonged to a skull remarkable for its unusual beauty and size, so that, taken by itself, the impression which it gave to an anatomist was that of a highly organized race.[56]

[Illustration:

Fig. 43. Section through a platycnemic tibia from Cro-Magnon.

Fig. 44. Section through the tibia of a male gorilla.

Fig. 45. Section through the tibia of a male chimpanzee. ]

It is important to remark that platycnemy has been regarded as a pithecoid structure, and for this reason the attempt has been made to establish the degraded position of those peoples which are most remarkable for platycnemy. But, as Boyd-Dawkins has already observed, although the tibiæ of the gorilla and the chimpanzee are to some extent platycnemic, they are much less so than the platycnemic bones of the human skeleton. The tibia of a male gorilla in the College of Surgeons Museum has an index width of 68·1, that of a female of 65·0, while the index of the chimpanzee’s tibia is 61·1, which is about the average of the tibias of Perthichwareu. It is unnecessary to indicate the other marked distinctions between the tibiæ of men and apes; if platycnemy is to be regarded as genetic, it must be admitted that man has in this particular far exceeded apes.[57] Neither the gorilla, the chimpanzee, the orang-utan, nor even the baboon possesses a tibia which is flattened in its upper or middle part. In all these apes the middle of the bone is more or less rounded, almost as if it had been rounded by a turning-lathe. According to my experience, the degree of platycnemy in anthropoids is subject to certain variations. It appears to me to be least marked in the aged male gorilla (Fig. 41), and in the gibbon (_Hylobates agilis_, _syndactylus_), in which latter animal the transverse section of the tibia represents an almost equilateral triangle. The platycnemy was more marked in an almost adult female gorilla, still more decided in an aged male chimpanzee, which came from the river Kiulu, and again in an aged female chimpanzee. On the other hand, the centre of the shaft of the tibia in another aged male chimpanzee which came from Loango, was rounded, and not platycnemic. In the tibia of an adult orang-utan which I examined, the platycnemy was very marked. But I agree with Boyd-Dawkins in never having met with an anthropoid in which the platycnemy is so considerable as it is, for instance, in the Cro-Magnon tibia, and in another found at Troy.

[Illustration:

Fig. 46.--Skeleton of the human foot, seen from above. _a_, Astragalus. _b_, Os calcis. _c_, Scaphoid bone. _d_, _e_, _f_, Cuneiform bones. _g_, Cuboid bone. _h_, Metatarsal bones. _ii_, Phalanges. ]

If we give a cursory glance at the lower limbs of apes, we see that all the same characteristics are present in their tarsus that we find in the human tarsus. In each case there is an astragalus, an _os calcis_, a scaphoid bone, three cuneiform bones, and a cuboid bone. There are undoubtedly several peculiarities in which the tarsus differs from the corresponding part of the human foot. The first metatarsal bone is joined to the first cuneiform bone by an articular facet which extends from the back to the sole of the foot. This joint plays a part resembling that of the thumb of the human hand (see Figs. 20 and 46).

In Huxley’s opinion, the hinder limbs of the gorilla terminate in a true foot, with a very movable great toe. It is undoubtedly a prehensile foot, but in no sense a hand. It is a foot which does not differ from the human foot in any essential characteristics, but only in relative circumstances, in the degree of flexibility, and in the subordinate arrangements of its parts. Huxley adds that it must not be supposed that he wishes to undervalue differences which, however, he does not regard as fundamental. They are important enough of their kind, since in any case the structure of the foot is in close correlation with the other parts of the organism. Although it cannot be doubted that the increased division of labour in man, which relegates the function of support entirely to the legs and feet, is a significant advance in structure; yet, regarded as a whole from the anatomical point of view, the points of agreement between the human foot and that of the gorilla are much more striking and significant than their differences.

The differences in the foot of the orang are still greater; in the very long toes and short tarsus, the short great toe and the removal of the heel from the ground, in the great obliquity of the joints which connect the foot with the shank-bones, and in the absence of a long flexor muscle to move the great toe, the orang’s foot differs still more from that of the gorilla than the latter differs from the human foot. In some of the lower apes the hands and feet are still further removed from those of the gorilla than in the case of the orang. In the American apes the thumb can no longer be opposed; in the ateles it is reduced to a mere rudiment, covered with skin; in the sahius it is bent forwards and provided with a curved claw like the other fingers. In all these cases there is no doubt that the hand differs more from that of the gorilla than the gorilla’s hand differs from that of man.[58]

Flower remarks that the chief distinction between the foot of a man and an ape consists in the fact that the latter is transformed into a prehensile organ. The tarsal and metatarsal bones, and the phalanges are of the same number in both orders, and in the same relative position, only in the foot of the ape the facet for articulation of the first cuneiform bone with the great toe is saddle-shaped, and obliquely directed towards the inner or tibial side of the foot. Thus, the great toe is separated from the others, and so placed, that when it is bent, it is directed downwards towards the sole, and is opposed to the other toes, much more opposed to them than is the case with the thumb of the human hand.[59] Owen also speaks of the characteristic transformation of the great toe of an ape’s foot into a thumb, opposed to the other toes, and adapted for grasping.[60]

[Illustration: Fig. 47.--Coaita (_Ateles paniscus_).]

K. E. von Bär does not agree with Huxley in considering that there is less difference between man and the gorilla than that which exists between different species of apes. “There are,” Von Bär remarks, “differences of various kinds among apes. In some the thumb is only a stump; in others, as in the orang-utan, the fingers of the hinder extremities are so long and curved that they cannot be extended on flat ground; in many of the smaller apes this member is still more like a hand than in the larger species, and the fingers can be easily spread out on the ground. In this case the foot is of a much blunter form, and is more flexible, so that the sole, which is properly turned inward, can lie flat on the ground. The heavier the body of the animal, the more sharply cut the structure of the foot must be, so that it does not admit of the free movements which are possible in the hand. But all these are only modifications of a climbing foot, or prehensile member--that is, of a hand, not modifications of a foot resting firmly on the ground and supporting the whole weight of the body.

“It must not be forgotten that the structure of the skeleton is subject to mechanical laws, which may be traced through the whole series of the animal world. This is readily apparent when we turn to the human structure.

“The human foot rests for the greater part of its length on the ground, that is to say, with the heel and centre of the foot, which form together a firm arch. The tarsus consists of the astragalus, and also of the _os calcis_, which in man form a very prominent part, taking a backward and downward direction, and of five other bones. The metatarsus consists of five bones, on which the five toes are inserted. In man these metatarsal bones are considerably longer than the separate phalanges. Thus, the arch on which man is supported in an erect position extends from the heel to the extremities of the metatarsal bones. The several bones are slightly movable, but they are so firmly connected that they can diverge but little from each other, unless muscular power is exerted. In order to press the toes upon the ground, it is again necessary to exert the muscles. The arched instep has this advantage, that the foot can take a better hold of the slight inequalities of the ground. In a profile view of the skeleton of a human foot, the shortness of the toes, in comparison with the length of the arched instep, is very apparent. In any natural position, even when man is not walking or standing, the sole of the foot is not turned inwards, but downwards.... The toes of the gorilla take the form of a hand, since the great toe stands separate like a thumb, while the other toes are turned outwards. In the gorilla the tarsus is short, and the heel is bent inwards. The several bones of the human foot are undoubtedly present in the hind hand of a gorilla, but the organ is changed into a prehensile organ or hand. The conditions are the same as in the parts of the mouth in insects which in some cases form movable mandibles, while in others they are attenuated into a proboscis. When it is asserted that apes are not quadrumanous, it is as if we were to say that flies have no proboscis, but attenuated mandibles.”[61]

All apes, including anthropoids, occasionally make use of their hinder extremities in order to snatch at objects. They also grasp with them in climbing. On such occasions, when they wish to secure the fruit they have seized from the voracity of their fellows, they take it between the toes of one hinder extremity, in order to be able to get away more quickly by means of the other, and by the use of both hands.

From what we have said, it will be seen how difficult it is to reconcile the views of different observers with respect to the fitting term to be given to the hinder extremities of apes. Against those who uphold the designation of _hind hands_ we must oppose the anatomical structure, and also the fact that a true hand ought to possess the power of rotation in a degree which exists in the fore, but not in the hind, extremities of apes. On this account I have already adopted, as more suitable and equally distinctive, the term of _prehensile foot_ for this member.[62] I agree with Haeckel in rejecting the common designation of apes as four-handed or quadrumanous.

The bands or ligaments which connect the different parts of the anthropoid skeleton together, and convert the detached elements into a movable machinery, do not on the whole differ much from the same structure in man. A detailed account of these ligaments would, for several reasons, be out of place in this work, and I shall only mention a few special and more interesting distinctions. Such, for example, is the uncommon strength of the _ligamentum nuchæ_ in the gorilla, which is quite in harmony with the great development of the spinous processes of the upper cervical vertebræ, and with the flattening of the squamous occipital portion. Since the sacral vertebræ are deeply inserted between the high ilia, the ilio-lumbar ligaments (_ligamenta iliolumbalia_) and the sacro-iliac ligaments (_ligamenta iliosacralia_) are of considerable size. In agreement with the projection in a downward direction of the high, narrow ischial bones, the sacro-sciatic ligaments which extend between these and the sacrum are very long in the chimpanzee. Although in this case the ischial spine is only represented by a roughness of the bone, yet there is on either side between this and the sacrum a powerful lesser sacro-sciatic ligament (_ligamentum spinoso-sacrum_).

The well-known anatomist, J. F. Meckel, has asserted that the depression in the head of the femur (_fovea capitis_), which serves for the insertion of the round ligament (_ligamentum teres_), is absent in the chimpanzee and orang, and he adds that it is also absent in the gibbon. In a skeleton of a young chimpanzee which had not shed its milk-teeth, and of which the ligaments were also preserved, Welcker found a fully developed round ligament inserted almost in the centre of the head of the femur. This agrees in every particular with the same formation in man. On the other hand, no trace of a round ligament was to be found in the hip-joint of a young orang-utan. The cartilaginous envelope of the head of the femur was smooth throughout, without any indication of a place for inserting the ligament. Welcker again found no such depression in the femur of an aged male orang-utan, nor was there any trace of it in another aged male orang, designated as _Simia Morio_. Welcker believes that he has established the fact that the round ligament is wanting in the orang-utan, but that it is present in the gorilla, chimpanzee, and gibbon. The same naturalist remarks that, although we may certainly assume that the round ligament is absent wherever there is no depression in the head of the femur, yet the existence of such a depression in the acetabulum (_fovea acetabuli_) is not enough to prove that a round ligament was inserted in it. The innominate bones of an adult orang-utan were examined by Welcker, and displayed a small, but well-defined depression, as if destined for a receptacle for this ligament,[63] running from the cotyloid notch down to the bottom of the acetabulum, between the two horns of the semilunar-shaped articular cartilage.

In a subsequent paper, Welcker states that the absence of the round ligament in the orang-utan, and its presence in the chimpanzee, had been previously established by Camper and Owen.[64] In three specimens of orangs which he had obtained immediately after death, Owen found that the round ligament was imperfectly developed on both sides. The chimpanzee differs from the orang in possessing a depression on the head of the femur. In the gorilla, as Owen observes, this depression has almost the same depth and relative position as in man. At Welcker’s request, Professor Dippel ascertained the presence of the depression in the femur of a gorilla skeleton which is preserved in the natural history collection at Darmstadt. St. George Mivart saw the skeleton of an orang in which the femur was marked with a slight but plainly indicated depression, just where the round ligament is usually attached. Welcker thinks it probable that in some specimens of the gorilla the round ligament is only slightly developed, and that in others it is altogether wanting. On several femurs of gorillas, this naturalist observed only doubtful traces of the depression in question. Duvernoy found the round ligament fully developed in the gorilla and chimpanzee. Vrolik failed to find it in the orang-utan, but ascertained its presence in the chimpanzee. Gratiolet and Alix saw that it was fully developed in _Troglodytes Aubryi_.

In addition to these somewhat conflicting assertions, I have myself observed, in the gorilla innominate and femur bones examined by me, more or less distinct indications of the depression which receives the round ligament. The ligament itself has been preserved with the body of a gorilla. The same remark applies to the skeletons and bodies of chimpanzees. In the case of the skeleton of an orang, slight indications of a depression were observed on the head of the left femur, and these indications were absent in the femurs of other specimens. In a large orang-utan which died in the Berlin Aquarium, only short, filamentous tufts of streaky fibres were apparent in the right acetabulum, and these were intermingled singly or in groups with the cartilaginous cells, somewhat resembling the cartilaginous corpuscles of the synovial membrane. From these facts we may conclude that the round ligament is generally but not invariably present in the gorilla and chimpanzee, and that it is altogether absent in the orang-utan. In the gibbon it is present in the majority of cases. I have myself observed it in _Hylobates agilis_, _leuciscus_, and _syndactylus_. Owen asserts that the unsteady gait of the orang is partly due to the absence of this ligament, but the truth of this surmise is rendered doubtful by the fact that the ligament is not unfrequently absent in other anthropoids. Moreover, the gait of all these arboreal and climbing animals is extremely ungainly.

The muscular system of anthropoid apes is very interesting. I must necessarily refrain from giving a detailed account of it, and will only mention some points in connection with this organic system, and their relation to corresponding points in the muscular system of man. I rely partly on the researches of others, and partly on my own. The amount of material which has been collected up to this time is, unfortunately, too scanty to enable us to draw satisfactory conclusions in all cases. We are often unable to decide whether the conditions presented to us in the case of anthropoids are normal or exceptional. Nor are the statistics of muscular variations in the human subject by any means firmly established. My own labours in this direction are not yet concluded. The assertions on the subject which have been published to the world and accepted as authoritative have already been shown to be to some extent untrustworthy. Even the little which I am now able to produce may not altogether stand the test of subsequent research. Brühl justly remarks that in no department of anatomy more than in that which treats of the muscles, is it more essential that we should not decide whether a form is normal or exceptional until it has been repeatedly examined.[65]

[Illustration:

Fig. 48.--Muscles of the head and face of a European. 1, 1′, Occipito-frontalis. 2, 3, Orbicularis palpebrarum. 4, Pyramidalis nasi. 5, Levator labii superioris alæque nasi. 6, Compressor naris. 7, Levator labii superioris. 7′, Zygomaticus minor. 8, Levator anguli oris. 8′, Zygomaticus major. 9, Orbicularis oris. 9′, Levator menti. 9″, Depressor labii inferioris. 10, Depressor anguli oris. 11, Masseter. 12, 13, Risorius and the buccinator by which it is covered. 15, Trapezius. 16, Attrahens. 17, 19, Attollens. 20, Retrahens aurem. 21, Sterno-mastoid. 22, Splenius. A. Tendinous aponeurosis. C. Malar bone (the parotis is removed). F. Skin of neck. ]

The cranial muscles of anthropoids are formed like those of men, except in a few unimportant particulars (comp. Figs. 48 and 50). I have not observed in anthropoids the muscular fibres which in man branch out from the orbicular muscle of the eye, and overlap the cheeks and temples, and which are considerably developed in the head of a Monjalo negro which was dissected by me (Fig. 49, ~3~, ~3′~). In apes that portion of the orbicular muscle which covers the supra-orbital ridge is very marked. There is generally a considerable layer of muscle on the nose and upper lip. I have dissected it in detail in anthropoid and other apes, including those of America; _i.e._ the zygomatic muscles, the levator labii superioris, and the levator labii superioris alæque nasi. This has also been done by Duvernoy, Alix, and Gratiolet, in the case of anthropoids dissected by them, as well as by Macalister and Bischoff.

[Illustration:

Fig. 49.--Head-muscles of a Monjalese negro. 1, 2, Occipito-frontalis. 3, 3′, Orbicularis palpebrarum. 4, Pyramidalis nasi. 4′, Levator labii superioris. 6, Levator labii superioris alæque nasi. 6′, Compressor naris. 7′, Levator anguli oris. 8, 8′, Zygomatici major et minor. 9, Orbicularis oris. 9′, Levator menti. 9″, Depressor labii inferioris. 9‴, Depressor anguli oris. 11, Masseter. 13, Buccinator. 14, Platysma. 15, Trapezius. 17, 18, Attollens and attrahens aurem. 19, Embedded temporal muscle. 20, Retrahens aurem. 21, Sterno-mastoid. 22, Deeply set muscles of neck. A, Tendinous aponeurosis. C, Zygoma. E, Parotis. *, Stensonian duct. ]

Bischoff was only able to identify a wide zygomatic muscle in the orang with the small zygomatic in man. In the orang, the gibbon, and the baboon, as well as in _Innus sinicus_ and _Ateles_, I myself was quite able to trace a division into a large and small zygomatic. In the gorilla dissected by me the levator labii superioris alæque nasi was very wide (Fig. 50, ~6~). In the case of a gorilla, Ehlers dissected the small zygomatic muscle, together with the levator labii superioris alæque nasi, in the manner introduced by Henle as a single square muscle of the upper lip (_Musculus quadratus labii superioris_). In the gorilla I observed a levator alæque nasi, together with the already mentioned levator labii superioris; but I failed to find any separate levator labii superioris. The very wide cartilage of the nose is occupied by a considerable amount of muscular tissue. All these muscles are present in the orang, but they are of small size and separated into detached bundles. The pyramidalis nasi may be traced in every instance, especially in the gorilla (Fig. 50, ~4~) and in the orang. It is not so strongly developed in the chimpanzee and gibbon, but is not absent in these apes, nor in those which are not anthropoid, such as the baboon, and ateles, or climbing ape.

[Illustration:

Fig. 50.--Head-muscles of gorilla presented in Fig. 3. 1, 2, Occipito-frontalis. 3, 3′, Orbicularis palpebrarum. 4, Pyramidalis nasi. 5, Levator alæ nasi. 6, Levator labii superioris alæque nasi. 7, Zygomaticus minor. 7′, Levator anguli oris. 8, Zygomaticus major. 9, 9′, Orbicularis oris. 10, Risorius. 11, 16, Masseter. 1′, Buccinator. 12, Depressor anguli oris. 13, Buccinator. 14, Platysma. 15, Trapezius. 17, Temporal. 18, 19, 20, Attrahens, attollens, and retrahens aurem. 21, Lesser muscle of helix. A, Tendinous aponeurosis. B, Cartilage of nostril. C, Zygoma. D, External ear. *, Stensonian duct. ]

I myself follow the original division of the muscles into those which belong to the nostril and upper lip, in accordance with the principles of Duchenne, Darwin, Gamba,[66] and others, and I do so the more readily, since it is impossible not to perceive the manifold and lively mimetic action which takes place in this particular region of an ape’s head. The distinct action of the levator labii superioris alæque nasi, the dilation of the nostrils, the function of a strongly developed levator anguli oris, are especially characteristic of the gorilla; but they are also perceptible in the chimpanzee and gibbon. The orang’s face is the least mobile. I observed that in the gorilla the risorius was very long, branching slightly in the fore-part of the corner of the mouth, and behind into three distinct wide bundles. The lowest bundle covered the platysma myoides, but could not be regarded as part of the latter. In one chimpanzee I found that the risorius was slightly developed, and in other animals of that species I failed to trace it at all. Alix and Gratiolet represent the Aubry chimpanzee (Plate ix. Fig. 1, ~15~) with the risorius strongly developed. I have not observed this formation either in the orang or the gibbon, but it was apparent in one of the ateles (_Ateles leucophthalmos_). In this case the muscle covered the platysma myoides and Stenson’s duct, _i.e._ the duct leading out of the parotid gland (Fig. 50, *).

For some time I was disposed to regard the risorius of this ape as only a radiation of the platysma myoides, but my opinion upon this point is again shaken.

In the gorilla a faint depressor anguli oris and an equally faint depressor labii inferioris may be observed, the latter partly covered by the large and predominant orbicularis oris (Fig. 50). In the chimpanzee the two depressors are plainly apparent, and in the gibbon the one first named was at any rate developed. The platysma myoides, the depressors just mentioned, and the crescent-shaped orbiculares are in this animal in close connection with each other. Froriep’s suggestion becomes ever more probable, that these muscles of the lower lip owe their origin to the intersection of the opposite portions of the skin-muscles of the neck which overlap the face. The buccinator muscle in anthropoids resembles on the whole that of man, and in both cases is pierced by Stenson’s duct (Fig. 50). The form of the masseter muscle is common to both (see Fig. 50, ~11, 16~). In the external ear of anthropoids there is an attrahens, attollens, retrahens (Fig. 50). Compared with that of a white man, and still more with that of a negro (see Figs. 48, ~19~, and 49, ~17~), the attollens is only slightly developed. The muscles attached to the cartilages of the ear are extremely scanty or partially wanting, which is also sometimes the case with man. The muscles of the helix are most strongly marked in the gorilla (see, for example, Fig. 50, ~21~). Tiedemann, Bischoff’s brother-in-law, carefully observed two living chimpanzees in Philadelphia for six months without detecting any movement of the ears. My own observation confirms his assertion and the remarks of Darwin, which I have already quoted, to the effect that anthropoids are incapable of moving their ears. I know of no individual exceptions. This is the more remarkable since some men have retained the power of voluntarily moving their ears, and the same power is also found in some species of apes, such as the sea-cats, baboons, macacas, and magots.

It will not here be out of place to say something of the characteristics, previously mentioned, of the physiognomical expression of anthropoid apes. Thus, for example, when the gorilla is agitated, he can move the skin of his head and bristle the hair which covers this region. The chimpanzee can also move the skin of the head, but with no very apparent bristling of the hair. The large male orang, which was in the Berlin Aquarium in 1876, bristled his hair and the skin of his head when he was much enraged. It is known that in some instances man also possesses this power.

I have already spoken of the expression of the eyes of these animals. I will only add that when anthropoids of every species are in great pain or seriously ill, the expression of their eyes is often most affecting.

The forehead of these animals is frequently marked by transverse furrows, and especially, as Darwin justly observes, when they raise their eyebrows. The same great observer considers that the countenances of anthropoids are, in comparison with those of men, generally inexpressive, and indeed, chiefly in consequence of the fact that they do not wrinkle the forehead when they are excited. The wrinkling of the forehead, which is one of the most significant forms of expression in man, is due to the action of the corrugatores supercilii, by which the eyebrows are drawn down and closer to each other, so as to form vertical folds on the forehead. It has been asserted that the orang and chimpanzee possess these muscles, but they seem to be rarely exercised--at any rate, to any remarkable extent.[67] When Darwin brought a chimpanzee out of his dark chamber into bright sunshine, he only once observed a slight wrinkling of the forehead. When the same observer tickled the nose of a chimpanzee with a straw, its face was slightly wrinkled, and faint vertical furrows appeared between the eyebrows.[68] Darwin never observed any wrinkling of the forehead in an orang. I myself have observed a contraction of that region of the brows which is covered with bristly hairs, and a wrinkling of the skin which covers the bridge of the nose in the gorilla and the chimpanzee, and have illustrated this expression by a drawing.

Darwin goes on to say that when a young chimpanzee is tickled, to which, as in the case of children, their armpits are peculiarly sensitive, he generally utters a chuckling or laughing sound, although sometimes the laugh is silent. The corners of the mouth are then drawn back, and this sometimes causes the eyelids to be slightly wrinkled. This wrinkling, which is so characteristic of the human laugh, is still more apparent in some of the other apes. In the chimpanzee the teeth of the upper jaw are not exposed when he utters this laughing sound, and in this respect he differs from man. Darwin further observes that when the tickled young orang ceases to laugh, an expression passes over his face, which, according to Wallace, may be called a smile. Darwin has observed something similar in the chimpanzee.[69]

My own observation confirms what has been said of the chuckling of a tickled chimpanzee. When Dr. Hermes, the director of the Berlin Aquarium, played with the chimpanzee which was kept in that establishment, a contortion of the corner of the mouth, resembling a somewhat sardonic smile, at once appeared. No specimen displayed this smile with so much effect as the lively Augustus, who delighted visitors by his inexhaustible humour in 1879. The gorilla, of which an illustration is given in Fig. 3, also drew down the corner of his mouth when he was pleased, by means of the muscular system which we have just described.

When the gorilla is provoked, he displays both rows of teeth, and opens his mouth to utter sounds of fury, while making ready to fight. It is well known that anthropoids are able to pout and project their lips; and Darwin says that they do this, not only when they are slightly teased, and are sullen or disappointed, but also when anything occurs to make them uneasy.

I have often observed in chimpanzees a slight wrinkling of the region of the nasal cartilage, and even a vibration in a lateral and upward direction. In any case, the muscles which we have described as acting on the nose and upper lip are exercised.

The platysma myoides, which extends in man from the lower row of teeth to just below the clavicle, occupies about the same area in the gibbon and in other apes (Fig. 50). In the chimpanzee, however, this muscle extends as high as the zygomatic arch, or even higher. In the gorilla also I observed that this part extends comparatively high on the face. In chimpanzees, orangs, and gibbons the upper fibres of this muscle seem to form the risorius. In one case the platysma myoides sent forth a fasciculus, about 18 mm. in width, to the beginning of the lower temporal ridges. In the gorilla I saw that the uppermost fibres of the platysma myoides were partly covered by the risorius (Fig. 50, ~10~).

From the corresponding muscle in the orang the lower fibres tend far backward, and are in connection with the deltoid muscle covering a segment of the capsular ligament. This muscle wrinkles the skin of the neck, and helps to draw down the lower jaw. In cases in which it extends far in an upward direction, as in those we have cited, it affects the lateral extension of the middle and lower skin on the faces of these animals, as well as the grinning contortion of the corner of the mouth. It may also have to do with the grumbling sound issuing from the throat-pouch, which is uttered by the animal when agitated, as he rapidly opens and closes his mouth.

The strong sterno-cleido-mastoid muscle found in these animals, and especially in the orang and gibbon, can be divided without difficulty into a sternal and clavicular portion. The two portions diverge from each other in a downward direction. As Bischoff justly states, a muscle not hitherto observed in man may be traced in all four species of anthropoids, a muscle which extends from the external part of the clavicle to the transverse process of the first cervical vertebra. Bischoff has called it the musculus omocervicalis. It is found in other apes, although the site of its origin varies, sometimes occurring on the spine of the scapula. Our Munich anatomist differs from Huxley in regarding this muscle as “a brilliant proof of the relation of all apes with each other.” I give this assertion without further comment.

The muscles which extend between the head, sternum, and clavicle, together with the muscles of the acromion process of the scapula, make an external covering to the throat-pouch, which I shall describe presently. The pectoralis major of the gorilla, as well as that of man, divides into two portions, one attached to the clavicle, the other to the cartilages of the true ribs. The former is divided from the deltoid by a wide interval, filled with connective tissue and fat. But both portions of the pectoralis major are divided by a tolerably wide space, into which, in Bischoff’s opinion, the throat-pouch is inserted. This, however, I do not believe, since that organ would be compressed and strangulated between the two portions of muscle whenever they were exercised. It may, however, be supposed that room for an enlargement of the throat-pouch when the animal is bellowing is afforded by the existence of these spaces. Bischoff is right in the assertion that the clavicular portion of the pectoralis major is wanting in the orang-utan. The upper part of this muscle springs directly from the sternum. The lower sternal ribs give origin to the pectoralis minor. The chimpanzee and gibbon display clearly in this muscle the separation we have mentioned into a clavicular and a sternal portion.

The structure of the pectoralis minor in these apes is full of interest. In the gorilla it divides into an upper portion of firmer tissue, less easily separable into digitations, which arises from the third to the fifth ribs, and a lower portion, separable into three digitations, of which the upper segment laps considerably over the lower segment of the upper portion. In the chimpanzee an upper portion of less firm texture extends from the second to the fourth, and a lower with three digitations from the fourth to the seventh ribs. This second lower portion is sometimes absent. I have seen the upper portion attached to the coracoid process of the scapula, and the lower portion to the ridge of the greater tuberosity of the humerus. In the orang an upper portion, separable into three digitations, extends from the second to the fifth ribs, and is attached to the coracoid process. A lower portion, also separable into three digitations, extends from the fifth to the seventh ribs, and is also attached either to the greater tuberosity of the humerus or to its edge; this latter portion projects below over the pectoralis major. In the gibbon (_Hylobates albimanus_), the upper portion starts from the second, the lower from the third to the fifth ribs. It may here be remarked that the pectoralis minor is in man also sometimes separable into digitations, which may be connected both with the coracoid process and with the capsular ligament of the shoulder-joint. In anthropoids the tendon of insertion of this muscle is remarkably slender.

According to Duvernoy, in the gorilla a fibrous, hood-like fascia covers the whole region of the occiput and neck. In adult males this fascia is 20 mm. in thickness. In a female dissected by me the rudiments of a similar hood-like cervical fascia were present. Duvernoy is justified in supposing that this is not yet developed in the young gorilla, and that a layer of connective tissue and fat is substituted for it. In a young gorilla I saw the trapezius divided into distinct bundles of flesh by layers of fat (Fig. 50, ~15~). The fascia corresponds to the great development of the trapezius, and the same characteristic development exists in other anthropoids. The adult male gorilla displays a powerful _ligamentum nuchæ_ in connection with the long spinous processes of the cervical vertebræ, as well as powerful inter-spinales muscles, spinales colli, and semi-spinales colli and dorsi. The great development of the spinous processes of the dorsal vertebræ of gorillas (Fig. 17), and also chimpanzees and orangs, involve the development of powerful semi-spinales, as well as of strong, fourfold spinales and inter-spinales muscles. The whole of the fleshy formation of the neck of an adult male gorilla which is covered by the trapezius is very voluminous, and especially the splenius capitis and colli, the long cervical muscle (_Musculus longissimus cervicis_), and the long head-muscle (_Musculus longissimus capitis_), which have also been regarded by me as parts of the long spinal extensor, and finally the oblique and vertical muscles at the back of the head. With Chappuy, I am disposed to regard the latter as modifications of the spinales and inter-spinales.

The levator anguli scapulæ is divided in anthropoids as in man. The subclavius is slender, except in the gorilla, and in the latter animal it sends a tendon obliquely to the coracoid process.

In all anthropoids the deltoid is strongly developed. In the gorilla it projects forwards and outwards in order to attach itself to the humerus, almost in its centre. Here it is separated from the brachialis anticus in a manner with which we are only imperfectly acquainted. It extends nearly as far in the gibbon and orang, while in the chimpanzee its attachment is higher up. Bischoff observes, and it was previously suggested by Vrolik, that in the chimpanzee the coraco-brachialis muscle possesses at its origin a moderately large second portion, which tends downwards over the lesser tuberosity of the humerus, and adheres to its edge. But I have seen both portions of the muscle in question attached to the coracoid process of the scapula in apes of this species. In the gorilla, orang, and gibbon the position of this muscle corresponds to that in man.

Chapman and Bischoff speak of a muscle common to all apes which starts from the tendinous attachment of the _latissimus dorsi_ on the edge of the lesser tuberosity of the humerus, and tends downwards on the inner side of the humerus, and to this muscle they give the name _latissimo-condyloideus_. Bischoff goes on to say that this muscle goes in some cases into the fascia which covers the biceps; and in others, as in the baboon, it is attached to the inner inter-muscular septum and to the internal condyle of the humerus. In the gibbon it only extends as far as the centre of the humerus, but in the orang it reaches to the condyle, where it is pierced by the ulnar nerve. Bischoff adds that this formation is wanting in man.

This structure is indeed remarkable in anthropoids. The muscle starts in a lateral direction from the insertion point of the _latissimus dorsi_. In the gorilla alone I observed that it started from the coracoid process of the scapula, together with the two portions of the pectoralis minor; it was connected for a space with the coraco-brachialis, and finally it was attached, in the upper part of the lower third of the humerus, to the inter-muscular septum which is found between the brachialis anticus and the triceps. In the chimpanzee, on the other hand, it has its origin in the _latissimus dorsi_, and divides into an anterior and posterior portion; the former is attached to the inner condyle of the humerus, while the latter is connected either with the middle or inner head of the triceps. In the orang the same division of this muscle may occur. In one of these animals I observed an anterior portion, very thin and semi-membranous, attached by an extremely slight tendon to the coracoid process of the shoulder-blade, while the hind portion issued from the _latissimus dorsi_. They were both in connection with the triceps and brachialis anticus. In other instances the muscle consisted only of the posterior portion, issuing from the _latissimus dorsi_. In the white-handed gibbon, the muscle issued from the region in which the tendons of the _latissimus dorsi_ and of the teres major are united, and was inserted into the fascia which is found between the bicipital and the brachialis anterior. This attachment may also occur in the centre of the shaft of the humerus. Chapman and Chudzinsky have observed anomalous instances of this formation in coloured races.[70]

It is well known that in man the biceps is inserted into the tuberosity of the radius by means of a flattened round tendon. This tendon, however, opposite the bend of the elbow, gives off a broad expansion, which passes into the fascia of the forearm, and is termed _Aponeurosis bicipitis_. In the gorilla this aponeurosis is carried on as strong fibrous bundles of the fascia of the forearm into the palmar fascia. In the gibbon the short head of the muscle does not always start from the lesser tuberosity of the humerus, nor from the tendon of the pectoralis major (Huxley), but sometimes from the edge of the lesser tuberosity, which is here connected with the _latissimus dorsi_, as well as with the sub-scapularis, the brachialis anticus, which is more to the side, and with the triceps. In the gibbon, as Bischoff justly observes, the supinator longus only reaches as far as the centre of the radius, instead of extending to the styloid process of that bone, as it does in other anthropoids, and in man.

The palmaris longus is wanting in the gorilla, but not in other anthropoids. The long flexor muscles of the fingers and the lumbricales resemble those of man (Figs. 51, 52). The flexor longus pollicis is absent in the gorilla. Duvernoy considers that it is replaced by a tendon of the long flexor of the fore-finger, but I have been unable to verify the existence of this tendon. The same muscle is also absent in the chimpanzee and the orang, but it may be traced in _Hylobates albimanus_. Chapman states that in the gorilla the pronator radii teres only sends forth one head,[71] but I have found it to be bicipital in animals of this species. The lower or hinder head issues, as in man, from the coronoid process of the ulna. Both in the gorilla and in the chimpanzee it extends far in a downwards direction on the radius (Fig. 52). The flexor carpi radialis starts in the chimpanzee with one head from the inner condyle of the humerus, and with the other from the radius. Bischoff describes the structure of the long abductor of the thumb in the orang, the baboon, the _pithecia_, and the _hapale_ as resembling that of man. But in the gorilla, the chimpanzee, and the macaca the tendon divides into two parts. Nor does one tendon belong, as in man, to a short extensor of the thumb, but the latter is wholly absent, and the division of the tendon only implies a continued division of the attachment to the trapezium, as well as to the metacarpal bones of the thumb. This division of the tendon also occurs in the gorilla, which likewise possesses a short extensor of the thumb. In this point, again, apes display a greater likeness to one another than to man.

[Illustration:

Fig. 51.--Palmar muscles of man. _a_, Ligaments of wrist, especially the anterior ligament. _c_, _c′_, Sheathing ligaments. _d_, _e_, _f_, Oblique fibres of the ligaments of the sheath of the flexor tendons. 1, 2, Tendons flexor sublimis, and of the flexor profundus muscles of the fingers. 3, The reciprocal perforation of these tendons. 4, Continuation of the tendons of the flexor profundus of the fingers. 5, Tendon of the flexor longus pollicis. 6, Abductor pollicis. 7, 8, 9, Flexor brevis, adductor, and opponens pollicis. 10, 11, 12, Flexor brevis, abductor, and opponens minimi digiti. 13, Lumbricales. 14, First dorsal inter-osseous muscle. ]

According to my own researches, the long abductor of the thumb in anthropoids forms a muscle not more considerable than one in proximity with it, of which the origin and more central direction recall the short extensor of the human thumb. In all four species I found that the abductor had two tendons, and was attached to the trapezium. The muscle in its vicinity is inserted above the base of the first metacarpal bone. I have not been able to discover an extra extensor of the thumb in the gorilla. The question now arises what we should think of the second muscle, which is found in these animals in the vicinity of the abductor. In my opinion, it may be confidently accepted as a short extensor of the thumb, since it always effects an extension of the metacarpal bone of that member, and in this act of extension it is supported by the long extensor which acts upon the phalanges. It must be remembered that the comparatively short thumbs of anthropoids have not to be employed in so many different ways as the human thumb, and that we cannot therefore be surprised that the development of the short extensor is less complete. A special extensor muscle of the index finger is either altogether absent in the gorilla or very slightly developed, while it is very apparent in _Hylobates albimanus_ (~6~, Fig. 53). In the chimpanzee this muscle sends a tendon to the middle finger. In the orang there is one extensor common to the four fingers. In the gibbon’s hand, this, as well as the other extensor and flexor muscles, is remarkable for its excessive slenderness. The manifold connections of the extensor tendons with each other are an interesting peculiarity (Fig. 53).

[Illustration:

Fig. 52.--Palmar muscles of gorilla. _a_, Anterior ligament. _b_, Remains of the skin of palm, here covered with a very sinewy skin. _c_, _f_, Oblique fibres of the ligaments of the sheath of the flexor tendons of fingers. 1, 2, Flexor tendons. 3, Spaces between the heads of the flexor brevis pollicis, whence in man the tendon of the flexor longus pollicis issues (comp. Fig. 51, ~5~). 4, 3, 3′, 5, Abductor, flexor brevis, abductor pollicis. 6, 7, 8, Opponens, flexor brevis, abductor, minimi digiti. 9, Dumbricales. 10, Supinator longus. 12, Flexor sublimis digitorum. 13, Flexor minimi digiti. 14, Flexor carpi ulnaris. ]

In the chimpanzee I observed a superficial flexor, common to the fingers, and enlarged in the region of the third and little fingers. A superficial flexor, belonging to the index finger, started from the inner condyle of the humerus, and from the back of the inter-muscular septum. The deep finger-flexor was attached to the four fingers. In the orang the first of these flexors forms a two-tendoned belly for the index finger, as well as one for the other three fingers. The deep flexor only displayed two bellies. In the gibbon, on the other hand, the superficial flexor displays four bellies.

[Illustration:

Fig. 53.--Muscular system of the back of a gibbon’s hand. 1, The extensor carpi radialis longior and brevior. 2, Abductor longus pollicis. 3, Extensor primi internodii pollicis. 4, Extensor secundi internodii pollicis. 5, Extensor communis digitorum. 6, Extensor indicis. 7, Extensor minimi digiti. 8, Extensor carpi ulnaris. 9, First dorsal inter-osseous muscle. 10, Continuation of the same to index finger. 11, 12, The other inter-osseous muscles of this region. A, The posterior annular ligament. ]

In the carpus of the chimpanzee there is, so far at least as my experience goes, a so-called sesamoid bone. It is in this instance in connection with the scaphoid and trapezium bones, just where the fibres of the anterior and posterior ligaments of the wrist pass into each other. In the chimpanzee the tendon of the long abductor muscle of the thumb sends some fibres into this sesamoid bone, while the other fibres of the tendon of this muscle, which divides into several strips, are inserted in the trapezium bone, and a few also in the base of the first metacarpal bone.

The short flexor muscle of the thumb, of which Bischoff has denied the existence, is certainly present in these animals. In the chimpanzee the lower fibres of the short abductor muscle of the thumb have their origin in the sesamoid bone. The middle fibres, of the same muscle issue from the strips of ligament attached to the sesamoid bone. On the other hand, the upper part of the muscle has its origin in the anterior annular ligament. In the orang, the lower fibres of the short abductor of the thumb likewise have their origin in the sesamoid bone, while the central fibres again start from the anterior annular ligament. The upper fibres are strong, and are inserted into the base of the first metacarpal bone. In a dissection of the orang the flexor longus pollicis sent a thin, tendinous expansion on to the bone. This sesamoid bone is also found in the gorilla, although Duvernoy and Rosenberg do not appear to be aware of its existence.[72]

In the palm of the gorilla’s hand there is a short abductor, a short bicipital flexor, an opponens, and an abductor of the thumb. The longer belly of the short flexor extending in a more radial direction, and in connection with the opponens, is only slightly developed. In the muscular system of a gorilla’s little finger we may observe an abductor, a short flexor, and an opponens. The palm of the chimpanzee displays a short abductor, an opponens, a short bicipital flexor, and an adductor of the thumb; also an abductor, a short flexor, and an opponens of the little finger. In the orang I observed a short abductor, a short flexor with two bellies, an opponens, and an adductor of the thumb. In addition to the short flexor of the thumb, Langer and Bischoff describe another short, independent muscle, representing the long flexor, and attached to the second phalanx, but I have not myself ascertained the existence of this muscle. The same anatomists mention an adductor between the third metacarpal bone and the first joint of the thumb, and another between the second metacarpal bone and the second joint of the thumb, passing on into the extensor tendon. I am myself convinced of the existence of a twofold adductor, but not of the fact that the tendon of one of the muscles (termed by Langer the second opponens) passes on into the extensor tendon. In the little finger of the orang there is an abductor, a short flexor, and an opponens. In the gibbon there is a short abductor, a faintly indicated opponens, a short bicipital flexor, and an adductor of the thumb. In _Hylobates albimanus_ this adductor divides into four or five portions, which are attached to the whole of the first metacarpal bone. In the little finger there is an abductor, a short flexor, and an opponens. In the same animal the first inter-osseous muscle is attached by one portion to the second metacarpal bone, by the other to the base of the second phalanx of the index finger (Fig. 53, ~9~, ~10~).

Bischoff has described the muscles which Halford terms _Contrahentes digitorum_ (contractors of the digits), which lie deep in the palm of the hands and feet of the chimpanzee and gibbon, the mandril, baboon, and other apes.[73] They rest upon the inter-osseous muscles, and are covered by the tendons of the long flexors of the digits, as well as by the lumbricales muscles. I have been unable to trace these _Musculi contrahentes_ in the gorilla. In a female chimpanzee I observed a _Musculus contrahens_ for the fourth, and another for the fifth finger, and the same for the fourth and fifth toes. In the orang I observed a _Musculus contrahens_ for the fourth, and one for the fifth fingers, and two faintly indicated _Contrahentes_ for the fourth and fifth toes. Similar muscles of the second, fourth, and fifth fingers, and of the fourth and fifth toes, may be observed in the white-handed gibbon.

In correspondence with the height of the pelvic bones, the gluteus maximus of these animals only displays a moderate width in comparison with its length. The tendon which attaches it to the femur extends low down, almost as far as the knee-joint. The gluteus medius and minimus are also long, in correspondence with this structure of the pelvis, although they are attached to the large trochanter, and to the posterior inter-trochanteric line. The climbing muscle (_Musculus scansorius_), which extends between the hip-bone and the condyles of the femur, was discovered by Troill in the chimpanzee, and by Bischoff in the orang, and is described by them as strongly made; it appears to be absent in the gorilla and the gibbon. The pyriformis generally forms portions of the neighbouring muscles. The tensor vaginæ femoris, which is strong and wide in most anthropoids, is either greatly reduced or altogether absent in the orang. The sartorius is not, as in man, attached to the inner surface of the tibia, just below the internal tuberosity, but it is inserted much lower down on this surface. In the gorilla it has a tricipital attachment, one to the deep fascia of the thigh, and two others to the internal border of the tibia. In the chimpanzee and the gibbon the muscle extends equally low down. In the orang it does not go so far, but the _gracilis_ and _semi-tendinosus_ are in the same relative position. The biceps of the femur is very apparent in the orang; its long head divides in two parts, of which the lower is inserted in the fibula, and is here united with the short head.

Bischoff at first denied the existence of the plantaris in the chimpanzee, and Brühl had previously done the same, but it is as normally present in that animal as in man, in whom also it is sometimes absent. I, however, as well as other observers, have failed to discover it in the gorilla, orang, and gibbon. The popliteus is developed in every instance. The tibio-fibular muscle (_Musculus peroneotibialis_), covered by the popliteus, of which the existence was ascertained by Gruber, has not been observed by me in any of the anthropoids, with the exception of the chimpanzee. But it was very apparent in a red sea-cat monkey (_Cercopithecus ruber_).

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.

[Illustration:

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.

[Illustration:

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.

[Illustration:

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]

[Illustration:

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.

[Illustration:

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).

[Illustration:

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.

[Illustration:

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.