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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
1T. H. Huxley, "Man's Place in Nature: III. On Some Fossil Remains of Man,” Collected Essays, vol. vii , p. 191.
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 civilisation is to improve the commissariat and cuisine, and as a result the jaws become smaller, and project less and less beyond the level of the forehead, that is, they become “ orthognathous.” 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. 1
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 civilised man, the jaw is relatively fully developed, and there is a tendency to reduction of the last molar tooth.
1 A. Nehring, “Menschenreste aus einem Sambaqui von Santos in Brasilien unter Vergleichung der Fossilreste des Pithecanthropus erectus, Dubois,” Ver. handl. Berliner anth. Gesellsch., 1695-6.
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 the lower jaw upon the upper may be likened to the beating of a hammer on an anvil. When the jaw muscles are powerful the lower jaw is brought with a considerable force against the upper jaw, and consequently the arches which connect the upper jaw with the cranium must be proportionately well developed. Conversely the weakening of the jaw muscles permits, for example, the outer rim of the orbit and the zygomatic arch to be of a more delicate construction.
The increase of the brain causes the forehead to be at the same time broader and higher. This fact was noted by the sculptors of ancient Greece, and they increased the vertical height of the forehead of some of their gods, so that, as in the case of Zeus, this human character was carried by them beyond human limits, when they wished to emphasise the benevolence and mental superiority of the Father of gods and men.
When at an indoor gathering we see a number of men with their hats off we notice that their heads vary in form. Some are small, others large; some have long heads, others have short ones; the head may be high or low, and the contours vary in diverse ways. These differences render the study of craniology peculiarly difficult, as it is almost impossible to describe most of them at the same time succinctly and intelligibly, and also because innumerable combinations of variable elements may occur in a collection of skulls from a single district.
Dr. D. G: Brinton, the well-known American anthropolo. gist, has been so impressed with the latter fact, that he despairs of the study of craniology throwing any certain light on the racial problems of anthropology. Undoubtedly an immense amount of tedious labour has been expended by enthusiastic students on the study and description of skulls, but often, one must confess, with very meagre results. There certainly is a wonderful fascination in skulls; and craniology, which to the outside observer appears to be about as uninteresting a subject as could well be conceived, has lured its votaries to more and more persistent and painstaking effort. The present writer, who once sat in the seat of the scornful, has also yielded to the charming of craniology.
A very strong argument in favour of craniology is the assistance that it should render to prehistoric archæology and to the history of peoples. We have documentary and legendary records of the shifting of populations, and our archæological museums are full of interesting records of the
past. It would be a matter of great importance if the skulls that are exhumed could also be brought in as evidence.
We are again face to face with the question that confronted us when considering the colour of the eyes and hair.
Can one particular head-form, or a restricted number of head-forms, be regarded as characteristic of a race or con| sanguineous group ? And are these characters sufficiently constant to be of scientific value ?