174 OSTEOLOGY. 
Obelion.—A point over the sagittal suture, on a line with the parietal foramina. 
Lambda.—The meeting-point of the sagittal and lambdoid sutures. 
Pterion.—The region of the antero-lateral fontanelle where the angles of the frontal, 
parietal, squamous temporal, and alisphenoid lie in relation to one another. As a 
rule, the sutures are arranged like the letter H, the parietal and alisphenoid separating 
the frontal from the squamous temporal. In other cases the form of the suture is like 
an X; whilst ina third variety the frontal and squamous temporal articulate with 
each other, thus separating the alisphenoid from the parietal. 
Asterion is the region of the postero-lateral fontanelle where the lambdoid, parieto-mastoid, 
and occipito-mastoid sutures meet. 
Stephanion.—The point where the coronal suture crosses the temporal crest. 
Dacryon.—The point where the vertical lachrymo-maxillary suture meets the fronto-nasal 
suture at the inner angle of the orbit. 
Jugal Point.—Corresponds to the angle between the vertical border and the margin of the 
zygomatic process of the malar bone. 
Gonion.—The outer side of the angle of the inferior maxilla. 
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 state 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 
Length — = Vertical index. 
Skulls are classified in accordance with the relations of length and height as follows :— 
Tapeinocephalic index below 72. Chamecephalic 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 basinasal length and the distance between the basion and the 
opisthion, we have a record of the vertico-mesial circumference of the cranium. This may further 
be divided by measuring the lengths of the frontal, parietal, and occipital portions of the 
superior longitudinal are. 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 breath. 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— 
Ophryomental length x 100 
Bizygomatic width 
=Total facial index. 
More usually, however, owing to the loss of the lower jaw, 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 bizygomatie width, thus— 
Ophryo-alveolar length x 100 
Bizygomatic width 
= Superior facial index. 
The terms dolichofacial or leptoprosope and brachyfacial or chameprosope have heen 
employed to express the differences thus recorded, 
