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  Section: Anatomy of Vertebrate Animals » The Classification and Organization of the Mammalia
 
 
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The Anthropidae

 
     
 

c. The Anthropidae are represented by the single genus and species, Man, and they are distinguished from the Simiadae, and especially the Anthropomorpha, by the following characters:

In progression on the ground, the erect posture is the easiest, and no assistance is given by the arms, which are shorter than the legs. After birth, the proportions of the body alter in consequence of the legs growing faster than the rest of the body. In consequence, the middle point of the height of the body-which, at birth, is situated about the umbilicus- becomes gradually lower, until, in the adult male, it is as low as the symphysis pubis.

In the manus, the pollex is strong and long, reaching to the middle of the basal phalanx of the index digit. In the pes, the tarsus takes up half the length of the foot; the calcaneal process is long, and expanded posteriorly. The hallux has half the length of the foot, and is nearly as long as the second digit; and its mobility in adduction and abduction is slight, compared with that of the hallux of the other Primates.

Hair is more abundant upon the crown of the head; and, usually, in the axillae, the pubic region, and the front part of the thorax, than elsewhere.

In the new-born infant the whole dorso-lumbar region of the spine is concave forward, and the vertebro-sacral angulation is slight; but, in the adult, the spinal column is concave forward in the thoracic, and convex forward in the lumbar region, mainly in consequence of the disposition of the elastic ligaments which connect the faces and the arches of the vertebrae. There is a strongly-marked vertebro-sacral angulation. Normally, there are twelve dorsal, five lumbar, five sacral, and four coccygeal vertebrae, and the transverse processes of the last lumbar vertebra are not expanded or directly connected with the ilia; but, in these respects, variations occur.

The spinous processes of the middle cervical vertebrae are much shorter than the seventh, and are usually bifurcated. The breadth of the sacrum is greater than its length. In the skull, the occipital condyles lie within the middle fifth of the base, and the occipital foramen looks downward, and either a little forward or but slightly backward. Neither sagittal nor lambdoidal crests are developed, but the mastoid processes are distinct, and generally conspicuous. The supraorbital ridges are never so largely developed as in some of the Anthropomorpha.
The orbits and the jaws are relatively smaller, and situated less in front of, and more below, the fore-part of the brain-case. A spina nasalis anterior is almost always present; (The only human skull in which I have heen able to find no trace of the existence of the anterior nasal spine, is that of an Australian, which, some years ago, I presented to the Museum of the Royal College of Surgeons.) and, in the profile view of the face, the nasal bones project more beyond the level of the ascending process of the maxilla than they do in any Ape. The palate is broader and its contour more arched than in any of the Anthropomorpha. Its posterior margin is ordinarily produced in the middle hne into a spina nasalis posterior, and the palato-maxillary suture is directed transversely.

The distance between the zygomata is either less than the greatest transverse diameter of the calvaria, or exceeds it but little. The malar is deeper than the squamosal portion of the zygoma, and the upper edge of the zygoma is but little curved.

The post-glenoidal process of the squamosal is small, while the auditory foramen is vertically elongated, its anterior wall being more or less flattened.

The interorbital space occupies about one-fourth of the interval between the outer walls of the orbits.

The planes of the orbital surfaces of the ethmoid bonea (ossa plana) are nearly parallel with one another.

The symphysis of the lower jaw has a mental prominence. The length of the cerebral cavity is more than twice that of the basi-cranial axis.

After birth, no trace of the premaxillo-maxillary suture remains upon the face, though it may persist in the palate.

The nasal suture usually persists, and the direction of the fronto-nasal suture is nearly transverse.

The cranio-facial angle(See p. 420 for the e xplanation of this term.) does not exceed 120°, and in the higher races of mankind does not go much beyond 90°.

The supra-orbital plates of the frontal bones project but little into the frontal region of the brain-case, and they are almost horizontal, instead of being strongly inclined upward and outward, as they are in the Anthropomorpha. The cribriform plate is long and wide, and the crista galli is usually prominent. The capacity of the brain-case of a healthy adult is invariably more than forty cubic inches, and may rise to more than a hundred cubic inches.

The scapula is broad in proportion to its length, and its spine cuts its vertebral edge nearly at right angles. The ilia are very broad; their inner faces present a well-marked concavity, and their crests an S-shaped curvature. A line drawn from the centre of the articular surface of the sacrum to the centre of the acetabulum makes nearly a right angle with the chord of the arc offered by the anterior face of the sacrum. In all the Anthropomorpha this angle is much more open.

The tuberosities of the ischia are hardly everted. The symphysis pubis is comparatively short, and the sub-pubic arch well marked. The width of the whole pelvis, from one iliac crest to the other, is greater than its height, which is the reverse of what obtains in the Apes. The transverse diameter of the brim is usually not exceeded by the antero-posterior diameter, though the contrary proportion occasionally obtains. The female pelvis is more spacious, and has a wider sub-pubic arch than the male.

The proximal articular surface of the astragalus looks almost directly upward, and hardly at all inward, when the sole is flat upon the ground; and the lateral facets are more nearly at right angles to this surface than in any Ape. The inner and outer malleoli are stronger and more downwardly produced. The calcaneal process is thick, strong, enlarged at its hinder end, and not incurved inferiorly, but produced into two tuberosities on which the heel rests. The form and disposition of the astragalar, navicular, and calcaneo-cuboid articulations are such that the distal moiety of the tarsus is capable of only a slight rotatory motion upon the proximal portion.

The distal articular surface of the ento-cuneiform bone is very nearly flat, though it has a slight convexity from side to side, and is irregularly concavo-convex, from above downward. The comparatively slight mobility of the metatarsal bone of the hallux arises partly from this circumstance, partly from the fact that the proximal articular surfaces of the four outer metatarsal bones are not perpendicular to the axis of those bones, but are obliquely truncated, from the tibial side, backward, to the fibular side. Hence the four outer metatarsal bones, instead of diverging widely from the hallux as they would do if their axis were perpendicular to the distal facets of the meso- and ento-cuneiform and cuboid bones, take a direction more nearly parallel with the metatarsal of the hallux, and the base of the second metatarsal, as it were, blocks the latter, in adduction. The hallux thus loses most of its prehensile functions; but, in exchange, it plays an important part in supporting the weight of the body, which, in the erect position, falls on three parts of the pes; namely, the heel, the outer edge, and the integumentary pad which stretches beneath the metatarso-phalangeal articulations, from the hallux to the fifth digit.

In the infant, the sole naturally turns inward, and the digits (especially the hallux) retain much of their mobility.

The only muscles which exist in Man, but have not yet been found in any Ape, are the extensor primi internodi pollicis and the peronaeus tertius.

The only pecuharities in the origin of muscles which ordinarily obtain in Man, and have not yet been found in the Apes, are—the complete separation of the flexor pollicis longus from the flexor digitorum perforans; the presence of a tibial, as well as of a fibular, origin of the soleus; the origin of all four heads oi the flexor brevis digitoruim pedis from the calcaneum; the origin of the fibula interosseus of the second digit of the pes from the middle metatarsal, on the dorsal side of the tibial interosseus of the middle digit. The result of the last-mentioned arrangement is that the second digit of the pes has two "dorsal" interossei, like the third digit of the manus. In the Apes the interossei of the second digit are generally arranged in the same way in both manus and pes.

The tendons of the flexor hallucis longus and flexor digitorum perforans are usually more closely connected in the sole of the foot in Man, than in the Anthropomorpha. But it is to be noted that all the apparently distinctive peculiarities of the myology of the Anthropomorpha are to be met with, occasionally, as varieties in Man.

In the brain of Man, the only distinctive features, apart from its absolute size (55 to 115 cubic inches), are the filling up of the occipito-temporal fissure; the greater complexity and less symmetry of the other sulci and gyri; the less excavation of the orbital face of the frontal lobe; and the larger size of the cerebral hemispheres, as compared with the cerebellum and the cerebral nerves.

There is no diastema, though the summits of the canines project, slightly, beyond the level of the other teeth. The premolars have not more than two roots, and the anterior edge of the crown of the anterior lower premolar is not prolonged and sharp. The permanent canine tooth emerges before the second molar.

The penis is devoid of a bone (though a prismatic cartilaginous body has occasionally been found in the centre of the gians), and its glans has a different shape from that of any of the Anthropomorpha. The vulva looks downward and forward, and the clitoris is comparatively small.

The changes in the proportions of the different parts of the body, at different periods of intra-and extra-uterine life, are very remarkable. In a foetus an inch and a half long, from the vertex to the heel, the head takes up from one-third to onefourth of the entire length. The arms and legs are of about the same length, and are shorter than the spine. The forearm is about as long as the upper arm, and the leg as the thigh. The manus and pes are very similar in size and form; and neither pollex, nor hallux, are so different from the other digits as at later periods. In a foetus rather more than five inches high, the head occupies a fourth of the entire height; the arms are longer than the spine by one-sixth of their whole length, and are a little longer than the legs. The forearm is about as long as the upper arm, and the thigh is a little longer than the leg. The manus and pes are about equal in length. In a foetus eight and a half inches high, the head measures less than a fourth of the whole height; the arms are longer than the spine by a fourth of their whole length, and they are longer than the legs. The extremities of the digits reach down to the knee when the body is erect.

At full term, the height of the head of the human foetus is rather less than a fourth that of the whole body, and the legs are longer than the arms. The arm is longer than the forearm and the thigh than the leg. The hands and the feet are still about equal in length.

Thus it would appear that, while the head grows more slowly than the rest of the body, throughout the period of gestation, after the embryo has attained more than two inches in length; the arms grow proportionally quicker than the body and legs, in the middle of gestation, when the proportions most nearly resemble those of the Anthropomorpha. In the latter part of the period of gestation the legs gain on the arms, and the proximal segments of the limbs on the distal ones. After birth these changes are continued. The adult has, on the average, three and a half times the height of the new-born child, and his arms are elongated in the same proportion. But the head is only twice as large, while the legs of the adult are five times as long as those of the child. At all ages after birth, the distance between the extremities of the digits of the outstretched arms is equal to the height in average Europeans.

Sexual differences, independent of the genitalia, are perceptible at birth; and the female infant is, as a rule, slightly smaller than the male. These differences become more marked at, and subsequent to, puberty; and are seen in the smaller stature of the female, the larger size of the head in proportion to the stature, the shorter thorax, the longer abdomen, and the shorter legs; so that the middle point of the stature of the female is nearer the umbilicus than in the male. The hips are wider in proportion to the shoulders, whence the femora are more oblique. The ridges and muscular processes of all the bones are less marked, and the frontal contour of the skull is more sharply angulated. When the peculiarities of the female sex are not connected with reproduction, they may be said to be infantile.

The different persistent modifications or "races" of mankind present a very considerable amount of variation in their anatomical characteristics. The color of the skin varies from a very pale reddish brown-of the so-called "white" races through all shades of yellow and red brovvns, to olive and chocolate, which may be so dark as to look black.

The hair differs much in its character, having sometimes a circular, sometimes an oval or flattened transverse section, and presenting all varieties, from extreme length and straightness to short, crisp wool.

The hair on the scalp is longer than that elsewhere; and it is very often, but not always, longer in the female. Hair upon the face and body is scanty in most races, and almost absent, except in the eyebrows, in some; but in others it becomes greatly developed over the lips, chin, and sides of the face, on the thorax, abdomen, and pubes, in the axillae, and sometimes, though more rarely, upon the rest of the body and limbs. When hair is developed upon the limbs the points of the hairs of the arm and forearm slope toward the elbow, and those of the leg and thigh away from the knee, as in the Anthropomorpha.

Enormous accumulations of fat take place upon the buttocks of the Bosjesmen, especially in the females; and the nymphae of these and some other Negroid tribes become greatly elongated.

It appears in some of the lower races, e. g., Negroes and Australians, the forearm and hand, and the foot and leg, are often longer in proportion than in Europeans. From not wearing shoes, the hallux is much more movable in these races, and the foot is commonly employed for prehension.

There is no proof of what is so commonly asserted, that the heel is longer, in proportion to the foot in Negroes.

The spines of the middle cervical vertebrae sometimes cease, more or less completely, to be bifurcated in the lower races. Thirteen pair of ribs are sometimes present, and occasionally there is a sixth lumbar vertebra. There may be one more sacral vertebra than the normal number; and a modification of the last lumbar, so that it resembles a sacral vertebra, and becomes connected with the ilia, seems to be more common in Australians and Bushmen than in other stocks.

In the lower races, the male pelvis is less in many of its dimensions, and seems to differ more from the female, especially in the tendency to equality of the transverse and anteroposterior diameters of the brim, and the narrowness of the intersciatic diameter, than in the higher races. This is particularly obvious among the Australians. The antero-posterior diameter of the brim of the pelvis is occasionally greater than the transverse, and this variety would seem to be commoner among the Bushwomen of South Africa than elsewhere.

But it is in the skull that the different races of mankind present the most striking osteological differences. The proportions of the antero-posterior and the transverse dimensions of the brain-case vary extremely. Taking the antero-posterior diameter as 100, the transverse diameter varies from 98, or 99, to 62. The number which thus expresses the proportion of the transverse to the longitudinal diameter of the brain-case is called the cephalic index. Those people who possess crania with a cephalic index of 80 and above are called brachycephali; those with a lower index are dolichocephali. The brain-case also varies greatly in its relative height. The proportion of the length of the cerebral chamber to the basicranial axis (as 100) may rise to 270 in the higher, and sink to 230 in the lower races; and there are great diversities in the extent to which the cerebral cavity is rotated backward or forward upon this axis. The position and the aspect of the occipital foramen vary considerably, as does the plane of that part of the squama occipitis which lies above the superior semicircular ridge. The supra-ciliary ridges vary greatly in their development, and in the extension of the frontal sinuses into them. They are nearly or quite solid in many Australian skulls.

In the size, form, and disposition of the facial bones, the different races of mankind present great diversities. A line drawn from the anterior extremity of the premaxilla to the anterior extremity of the basicranial axis, may be taken to represent the facial axis, and the angle included between these two is the craniofacial angle. It varies with the extent to which the face lies in front of, or below, the anterior end of the cranium, from less than 90° to 120°. "When it is great, the face is prognathous; when it is small, the face is orthognathous. This is the fundamental condition of prognathism or orthognathism. A secondary condition is the form of the alveolar portion of the upper jaw, which, so far as it is vertical, tends toward orthognathism; but, so far as it is oblique and produced, tends to prognathism.

The arch formed by the teeth is, in the most orthognathous races, wide and evenly rounded; while, in the most prognathous, it is prolonged, and its sides are nearly parallel. The teeth themselves are much larger, the roots of the premolars and molars more distinct, and the hindermost molar not so small relatively to the others, in some of the lower races, notably the Australians.

The mental prominence may project beyond the line of the vertical alveolar margin of the mandible, in the higher races, or it may be almost obsolete, and the alveolar margin may be greatly inclined forward, in the lower.

The different races of mankind are divisible into two primary divisions; the Ulotrichi, with crisp or woolly hair, nnd the Leiotrichi, with smooth hair.

a. The color of the Ulotrichi varies from yellow-brown to the darkest hue known among men. The hair and eyes are normally dark, and, with only a few exceptions (among the Andaman Islanders), they are dolichocephali. The Negroes and Bushmen of ultra-Saharal Africa, and the Negritos of the Malay peninsula and archipelago, and of the Papuan Islands, are the members of this Negroid stock.

b. The Leiotrichi are divisible into-

1. The Australioid group, with dark skin, hair, and eyes, wavy black hair, and eminently long, prognathous skulls, with well-developed brow-ridges, who are found in Australia and in the Dekhan. The ancient Egyptians appear to me to have been a modification of this race.

2. The Mongoloid group, with, for the most part, yellow-ish- brown, or reddish-brown, skins and dark eyes, the hair being long, black, and straight. Their skulls range between the extremes of dolichocephaly and those of brachycephaly. These are the Mongol, Tibetan, Chinese, Polynesian, Esquimaux, and American races.

3. The Xanthochroic group, with pale skins, blue eyes, and abundant fair hair. Their skulls, like those of the Mongoloid group, range between the extremes of dolichocephaly and brachycephaly. The Slavonians, Teutons, Scandinavians, and the fair Celtic-speaking people are the chief representatives of this division; but they extend into North Africa and Western Asia.

4. The dark whites, or Melanochroi; pale-complexioned people, with dark hair and eyes, and generally long, but sometimes broad skulls. These are the Iberians and "black Celts" of Western Europe, and the dark-complexioned white people of the shores of the Mediterranean, Western Asia, and Persia. I am disposed to think that the Melanochroi are not a distinct group, but result from the mixture of Australioids and Xanthochroi.

Fossil remains of Men or implements of human manufacture have hitherto been found only in late Tertiary (Quaternary) deposits, and in caves, mingled with the remains of animals which lived during the glacial epoch.
 
     
 
 
     



     
 
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