Experiments on the lower animals prove that the skull is easily moulded by trifling causes. Darwin found that he could produce long, or short, or non-symmetrical skulls in rabbits by training.[2] The shape also bears a relation to stature. As a general rule short men have short or rounded heads, tall men have long heads. The longest skulled nation in Europe are the Norwegians, who are also the tallest; the roundest are the Auvergnats, who, of all the European whites, are the shortest.
Nevertheless, employed cautiously, in large averages, and with a careful regard for all the other ethnic elements, the measurements of the skull are extremely useful as accessory data of comparison.
Some craniologists have run up these measurements to more than a hundred; but those worth mentioning in this connection are but few. There is, first, the proportion which the length of the head has to its breadth. This makes the distinction between long, medium and broad skulls, “dolicho-cephalic,” “meso-cephalic,” and “brachy-cephalic.” In the medium skull the transverse bears to the longitudinal diameter the proportion of about 80:100. The proportion 75:100 would make quite a long skull, and 85:100 quite a broad skull, the extreme variations not exceeding 70:100-90:100. (Figs. 1 and 2.)
Figs. 1 and 2.—Long and Short Skulls.
The Asiatic race or typical Mongolians are generally brachy-cephalic, the Eskimos and African negroes dolicho-cephalic; while the whites of Europe and American Indians present great diversity.
The lengthening of the skull may be anteriorly or posteriorly, and this is probably more significant of brain power than its width. In the black race the lengthening is occipital, that is at the rear, indicating a preponderance of the lower mental powers.
Fig. 3.—Lines of Sutures in the Skull.
The height of the skull is another measurement which is much respected by craniologists; but they are far from agreed as to the points from which the lines shall be drawn, so that it is difficult to compare their results.[3] The “sutures,” or lines of union between the several bones of the skull, present indications of great value. In the lower races they are much simpler than in the higher, and they become obliterated earlier in life; the bones of the skull thus uniting into a compact mass and preventing further expansion of the cavity occupied by the brain.[4] (Fig. 3.) Occasionally small separated bones are found in these sutures, more frequently in some races than in others. One of these, toward the back of the head, occurs so constantly in certain American tribes that it has been named the “Inca bone.”[5]