CHAPTER III.

THE VALUE OF HEAD-FORM IN ANTHROPOLOGY

O much attention has been paid by anthropologists

to the shape of the head, and particularly to that of the skull, that the greater part of the literature of physical anthropology is taken up with minutely descriptive and statistical accounts of the contours and measurements of skulls.

It is obvious enough why the skull has been so minutely studied. Although most parts of the human skeleton exhibit distinctive traits by which they can be readily distinguished from the bones of other animals, the more characteristic human tendencies are, however, so to speak, focussed in the skull. For example, the bones of the legs and the pelvis have become modified owing to the assumption of the erect attitude; but the position of the large hole (the foramen magnum) in the base of the skull through which the spinal cord passes into the brain and the balancing of the head on the vertebral column attest to the same fact.

The acquisition of the erect attitude liberated the

hand from progression, and this gave it the chance to become the delicate and mobile mechanism that we now possess, and which is especially marked in the case of musicians, artists, and skilled workmen. The "handiness" of the hand relieved the jaws from much of the work that they were wont to do, and as a consequence the human jaw has a marked tendency to be reduced in size.

Thus two very characteristic human traits, the erect posture and the hand, have influenced the skull.

The other essentially human characteristics are mainly to be found in the head itself; of these the most important is the brain. The absolute and relative large size of the brain at once separates the brain of man from that of the higher apes. This character can be determined from an examination of the skull without any special anatomical knowledge.

It is convenient in considering the skull to distinguish between the cranium, or brain case, and the face the latter is composed of the organs of sight and hearing, with their protective casings, and the jaws.

The cranium and the face can, to a certain extent, be studied independently of each other, though there is always a distinct relation between them, and the one acts upon the other in various ways.

Among the lower races of men we find that the

jaws are usually of large size, and they often project far beyond the level of the forehead. A skull in this condition is called "prognathous," "a term which has been rendered," as Huxley points out, "with more force than elegance, by the Saxon equivalent -'snouty. An example of this prognathism is seen in the Negro's skull. (Fig. 8, No. 4.)

These great jaws are associated with large teeth and powerful muscles. The jaw or masseter muscles arise from the side walls of the skull, and are inserted in the lower jaw. The more powerful the muscles the higher they creep up the sides of the skull, their upward limit being marked by a curved line (the temporal crest), and the more they are likely to compress the skull, especially immediately behind the orbits. This lateral compression of the temporal region of the skull would naturally be most effective in quite young persons when the skull was still pliable. The feeding on coarse food and the absence or imperfection of cooking the food would give more work for the jaws, and consequently the muscles would become more powerful. One effect of civilization is to improve the commissariat and cuisine, and as a result the jaws become smaller, they project less and less beyond the level of the forehead, that is, they become "orthognathous."

* T. H. HUXLEY, "Man's Place in Nature: III. On some Fossil Remains of Man," Collected Essays, vol. vii., p. 191.

The teeth are reduced in size and number, and the masseter muscles having less work to do become smaller and less powerful, and consequently they exert less pressure on the side walls of the cranium, and so the skulls are not so narrow, especially in front.

That the jaw muscles do affect the skull has been shown by Nehring,* who, from his studies on skulls of both sexes and of various ages of anthropoid apes and of dogs of different breeds, is of the opinion that the occurrence of a constriction between the orbital and cerebral portions of the skull has direct relation to the strength of the facial musculature, and more especially of the jaw muscles. If the skull of a muscular Eskimo dog be compared with that of a pug or a Bolognese lap-dog, it will be found that this constriction is very marked in the Eskimo dog, the zygomatic arches of which are widely outstanding, and all the muscular attachments strongly developed ; but the constriction is scarcely noticeable in the pug, and is entirely wanting in the Bolognese lap-dog; the two latter exhibit feminine rounded forms of the corresponding parts of the skull, with a fullydeveloped musculature. In domesticated dogs, as in civilized man, the jaw is relatively fully developed,

* A. NEHRING, "Menschenreste aus einem Sambaqui von Santos in Brasilien, unter Vergleichung der Fossilreste des Pithecanthropus erectus, Dubois," Verhandl. Berliner anth. Gesellsch, 1895-6.

and there is a tendency to reduction of the last molar tooth.

It must not be overlooked that the decrease of the action of the jaw muscles is concomitant with rise in culture, that is to increased mental activity, which is usually associated with increase in the volume of the brain. We have already seen that the statistics collected in the anthropometric laboratory in the University of Cambridge, as worked out by Venn and by Galton, show that the period of the growth of the brain is prolonged in students as opposed to those of corresponding ages who cease to study.

It may be accepted as true in the main that the increase in the size of the brain, which is due to culture, is exhibited proportionately more in the breadth and height than in the length.

Thus culture may act in two ways on the skull, directly by enlarging the volume of the brain, and therefore increasing the size of the skull; and indirectly by causing a reduction of the jaw, which reacts again upon the skull. One is not surprised, then, to find that the higher races have, as a rule, a greater breadth in the anterior temporal region of the skull than the lower races.

The decrease in the size of the jaws and of the strength of their muscles induces a corresponding modification in the rest of the face. The action of