286 OSTEOLOGY. 



Jugal Point. Corresponds to the angle between the vertical border and the margin of the 



temporal process of the zygomatic bone. 

 Supra-auricular Point. A point immediately above the middle of the orifice of the 



external acoustic meatus close to the edge of the posterior root of the zygoma. 

 G-onion. The lateral side of the angle of the mandible. 

 Pogonion. The most prominent point of the chin as represented on the mandible. 



The measurements of the length of the skull may be taken between a variety of points the 

 nasion, glabella, or ophryon in front, and the inion or maximum occipital point behind. Or the 

 maximum length alone may be taken without reference to any fixed points. In all cases it is 

 better to state precisely where the measurement is taken. The maximum breadth of the head is 

 very variable as regards its position ; it is advisable to note whether it occurs above or below the 

 parieto-squamosal suture. The inter-relation of these measurements as expressed by the cephalic 

 index has been already referred to. The width of the head may also be measured from one asterion 

 to the other, biasterionic width, or by taking the bistephanic diameter. 



The height of the cranium is usually ascertained by measuring the distance from the basion 

 to the bregma. The relation of the height to the length may be expressed by the height or 

 vertical index, thus 



Height x 100 _ ,. ... 



-T- = Vertical index. 

 Length 



Skulls are classified in accordance with the relations of length and height as follows : 



Tapeinocephalic index below 72. Chamsecephalic index up to 70. 



Metriocephalic index between 72 and 77. Orthocephalic index from 70-1 to 75. 



Akrocephalic index above 77 (Turner). Hypsicephalic index 75-1 and upwards 



(Kollmann, Ranke, and Virchow). 



The horizontal circumference of the cranium, which ranges from 450 mm. to 550 mm., is 

 measured around a plane cutting the glabella or ophryon anteriorly, and the maximum occipital 

 point posteriorly. The longitudinal arc is measured from the nasion in front to the opisthion 

 behind ; if to this be added the basi -nasal length and the distance between the basion and the 

 opisthion, we have a record of the vertico-median circumference of the cranium. This may further 

 be divided by measuring the lengths of the frontal, parietal, and occipital portions of the 

 superior longitudinal arc. In this way the relative proportions of these bones may be 

 expressed. 



The measurements of the skeleton of the face are more complex, but, on the whole, of greater 

 value than the measurements of the cranium. It is in the face that the characteristic features of 

 race are best observed, and it is here that osseous structure most accurately records the form and 

 proportions of the living. 



The form of the face varies, like that of the cranium, in the relative proportions of its length 

 and breadth. Generally speaking, a dolichocephalic cranium is associated with a long face, whilst 

 the brachycephalic type of head is correlated with a rounder and shorter face. This rule, how- 

 ever, is not universal, and there are many exceptions to it. 



The determination of the facial index varies according to whether the measurements are made 

 with or without the mandible in position. In the former case the length is measured from the 

 ophryon or nasion above to the mental tubercle below, and compared with the maximum 

 bizygomatic width. This is referred to as the total facial index, and is obtained by the 

 formula 



Ophryo-mental length x 100 . 

 - T^T- = Total facial index. 



Bizygomatic width 



More usually, however, owing to the loss of the mandible, the proportions of the face are 

 expressed by the superior facial index. This is determined by comparing the ophryo-alveolar or 

 naso-alveolar length with the bizygomatic width, thus 



Ophryo-alveolar length x 100 



* 4r- r- = Superior facial index. 



Bizygomatic width 



The terms dolichofacial or leptoprosope and brachyfacial or chamoeprosope have been 

 employed to express the differences thus recorded. 



Uniformity in these measurements, however, is far from complete since many anthropologists 

 compare the width with the length = 100. 



The proportion of the face-width to the width of the calvaria is roughly expressed by the use of 

 the terms cryptozygous and phsenozygous as applied to the skull. In the former case the 

 zygomatic arches are concealed, when the skull is viewed from above, by the overhanging and 

 projection of the sides of the cranial box ; in the latter instance, owing to the narrowness of the 

 calvaria, the zygomatic arches are clearly visible. 



The projection of the face, so characteristic of certain races (Negroes for example), may be 

 estimated on the living by measuring the angle formed by two straight lines, the one passing from 

 the middle of the external acoustic meatus to the lower margin of the septum of the nose ; the 

 other drawn from the most prominent part of the forehead above to touch the incisor teeth 

 below. The angle formed by the intersection of these two lines is called the facial angle 

 (Camper), and ranges from 62 to 85. The smaller angle is characteristic of a muzzle-like 



