INDEX, Cephalic, Cranial, etc. For some years anthropologists have taken special care in determining geometrically the forms and dimensions of the human cranium among the different races of mankind. The task is a diffi cult one because the human cranium is not a rectangular box. Various procedures have come into general use to determine the measure of the distances of the head, the skull, the facial cavities, and the brain capacity. Indexes are the terms used to define the relations existing between these linear distances and the follow ing are the principal. The Cephalic index is the relation which exists between the transverse diameter of the head and the anteroposterior diameter. The latter is taken from the middle and lower part of the frontal bone to the furthest part of the occiput. The transverse diameter is the greatest line at right angles to the anteroposterior. In practice it is as sumed that the length equals 100, and the width is represented as a percentage of this. The result is the index for which the formula is greatest width X 100 — cephalic index length This index is an important medium for classi fying skulls. A low index indicates a great length as compared with the width, giving an elongated or oval skull. A high index in dicates a rounded skull. A common classifica tion of skulls on the basis of this cephalic index is the following: Subdolicho cephalic Below 70 Dolicho cephalic 70 to Meaoticephalic 77.8 to 80.
Subbrachy cephalic 80 to 83.3 Brachy cephalic 83.3 to 85.
Hyperbrachy cephalic Above 85 It must be remembered that these divisions are arbitrary and vary slightly for the cephalic index, and even in different countries. As a general result of this classification we find that Eskimos, African negroes, Fuegians, Veddahs, Maoris, Fiji islanders, and certain peoples of northern Europe are dolichocephalic, while American Indians, Malays, Mongols, Lapps, Finns, Poles, Tyroleans are brachycephalic. British, French, Germans, Greeks, Japanese, Chinese are mesoticephalic. The cephalic index alone is insufficient for a proper classification of the skulls or heads of the different races.
Recourse is had therefore to other indices which taken in conjunction with the cephalic, will give the shape of the head. The frontal index is the relation between the least frontal diameter and the greatest cranial diameter. By contrast ing height with length a vertical index is ob tained according to which we get platycephals, or low skulls; metriocephalic, or moderate; and acrocephalic, or high skulls. The facial index is that resulting from a comparison of the length and width of the face The length is measured from the root of the nose to the tip of the chin, the forehead being part of the cranium and therefore excluded; the width is calculated by the projecting convexities of the zygomatic arches. High faces are those above and low faces those below 90. A nasal index is measured from its height and width, the latter calculated from the width of the nasal wings. According to the result a skull or head is leptorhine, or narrow below 48; mesorhine, or medium from 48 to 53; and platyrhine, or broad nosed, above 53. The orbital index is that resulting from the relation of the height and width of the orbit or pyramidal chamber which lodges the eye-ball. The width is calcu lated from the dacryon on the inner wall to the most distant point on the outer edge of the wall. The width being always greater than the height the formula for the orbital index is: height X 100 = orbital index width According to this index we have megaseme, or great orbits, above 89; mesoseme, from 84 to 89 and microseme,. below 84. Other indexes are the pelvic, the sacral, the dental and the pilastric obtained by measurement and compu tation similar to those described above. Methods differ widely according to the different .schools of anthropologists. Consult Broca, 'Instruc tions generales pour les recherches anthropolo (Paris 1879) • (Deniker, Races of Man) (London 1900) ; Bertillon and Chervin, thropologie trietrique) (Paris 1909) • Livt," (Milan 1900); Ranke, Mensch) (Leipzig 1911).