If we apply these methods to the study of the cephalic index, we see that generally the crania of Negroes, Melanesians, Eskimo, Ainus, Berbers, the races of Northern Europe, etc., are dolichocephalic, while those of the Turkish peoples, the Malays, certain Slavs, Tyrolese, etc., are brachycephalic; that the dolichocephalic predominate in Great Britain, while the brachycephalic are in a majority in France, etc. (See p. [75], and [Appendix II].)
The relation of the height to the breadth or to the length of the skull gives likewise an idea of its general form. It is thus that we recognise low skulls (platycephalic), medium (orthocephalic or metriocephalic), or high (hypsicephalic).
In order more correctly to describe the different peculiarities of the cranium, and to be able to refer the measurements to fixed co-ordinates, it is desirable to place the skull, when being studied, on a horizontal plane. Unfortunately, anthropologists are far from being agreed as to this initial plane. In France, in England, and in many other countries, that adopted is the alveolocondylean plane of Broca (Fig. [13], L K), which passes through the condyles and the alveolar border of the upper jaw; it is nearly parallel to the horizontal plane passing through the visual axes of the two eyes in the living subject; whilst in Germany the plane still in favour is one passing through the inferior border of the orbit and the centre or top of the contour of the auditory meatus[60] (Fig. [13], N M). The skull once conveniently placed in position according to a horizontal plane, the different views of it are the following: seen from above (norma verticalis of Blumenbach, Figs. [10] and [11]), from below (norma basilaris), from the side or in profile (norma lateralis, Fig. [13]), from the full face (norma facialis, Fig. [12]), or from behind (norma occipitalis).
In regard to the face, different measurements express its general form; thus the relation of the bi-zigomatic length (Fig. [12], I G) to the total height of the bony structure of the head (Fig. [12], K L), or to its partial height from the glabella to the alveolar border of the upper jaw-bone (Fig. [12], F H), serves to separate skulls into brachy-or dolicho-facial, or, as they are also called, chamæprosopes and leptoprosopes. Other characters, such as the excessive development of the supraciliary ridges (Fig. [13], A), also give a special physiognomy to the bony structure of the face.
FIG. 12.—Skull of ancient Egyptian exhumed at Thebes,
with principal craniometrical lines.
But the parts that deserve particular attention are the orbits and the nasal skeleton. The orbital orifice represents a quadrilateral figure more or less irregular, more or less angular or rounded, the length and breadth of which can be measured. According to Broca,[61] the breadth is measured from the point called dacrion (Fig. [12], X) (situated at the intersection of the fronto-lachrymal suture and the crista lachrymalis) to the most distant point of the opposite edge of the orbit (Fig. [12], Y); the height (Fig. [12], T Z) is also measured perpendicularly to the preceding line. The relation of this height to the breadth = 100, or the orbital index, expresses in figures the form of the more or less shallow quadrilateral of the orbit. What are called average orbits, or mesosemes, are those whose index varies from 83 (Broca), or from 84 (Flower), to 89; shallow orbits, or microsemes, those which have the index lower than 83 or 84; finally, higher or large orbits, megasemes, those which have their index from 90 and upwards. The annexed table gives the orbital indices of the principal populations of the globe.