VARIOUS FORMS OF THE SKULL. 79 



of the female is from 80 to 90 cubic inches. As contrasting with this more 

 developed condition may be mentioned the cranial capacity of the Australian, 

 which averages from 70 to SO cubic inches, and not mifrequently falls as low as 

 (jo cubic inches. (See on this subject the fui-fcher details under Size of the Brain.) 



Measurement and Classification of Differences. — The estimation of differ- 

 ences in the form and size of skulls by a simple and accui-ate method is not easily 

 accomplished, and their suitable arrangement and nomenclature is still more 

 difficult. 



The method proi^osed by Camper, in vrhich the degi-ee of projection of the face 

 as compared with the craniiun is measui'ed by the '" facial angle," fonned by the 

 meeting of a line descending from the most 

 projecting part of the forehead in front of 



the upper incisor teeth with another carried Fig. 66. 



backwards from the anterior nasal spine at 

 the level of the external auditory meatus, 

 fails to take cognizance of the size of the 

 cranium and many important features of 

 difference, and is subject to various source 

 of fallacy from partial variations which ("« ■ 

 not affect the whole character of the skull. 



The "occipital" angle of Daubentou, 

 which varies with the direction of the plane 

 of the foramen magTium of the occipital 

 bone, is mainly an indication of the attitude 

 of the head in relation to the vertebral 

 column. In man this plane looks dowTi- 

 wards and forwards, in the anthropoid apes 

 downwards and backwards, aud in most Fig. 66. — Prognathous Skull of a 

 quadrupeds nearly directly backwards, so Native Australian (Carpenter). ^ 



as in them to biing the basicranial and the 

 vertebral axis almost into the same line. 



The method of Blumenbach hj the " norma vei-ticalis," or perpendicular view 

 from above, when combined with measurements, gives important infonnation as 

 to the size and fomi of the cranium, and the extent to which the zygomatic 

 arches and jaws project beyond or are concealed by the cranial walls, and when 

 combined with the lateral and front views of the head, as in the estimations of 

 Pritchard. may give sufficiently clear views of the form of the cranium and face, 

 their more or less oval fonn, and the degree of orthognathism or prognathism. 



The more recent classification of skulls by Retzius, in which cranial form and 

 facial relation are both taken into account, is at once simple and comijrehensive. 

 In this system all those skidls in which the transverse diameter of the cranium 

 bears to the longitudinal the proportion of SO per cent, or above it are ranked as 

 Brachycephalic, wide or short skulls, and those in which the proportion is lower 

 than 80 per cent, are placed in the Dolichocephalic group, narrow or long skulls ; 

 and under each of these primary clivisions is established a subordinate one 

 founded on the relation of the face to the cranium, under the names of the 

 orthognathous and prognathous forms. Thus, the usual British skull and that 

 of the natives of Western Europe belong to the orthognathous dolichocephalic 

 type ; the African negro and Australian to the iirognathous dolichocephalic ; the 

 Sclavonic nations are examples of the orthognathous brachycephalic, and the 

 Mongolians of the prognathous brachycephalic type. 



For an approximate determination of the form and size of skulls it may be 

 sufficient to ascertain the principal dimensions by external measurements in the 

 horizontal, transverse and vertical diameters of the cranium, and in the vertical 

 and transverse diameters of the face, and to measui'e the capacity of the cranium 

 by means of suitable material introduced into its cavity : and it will add greatly 

 to the value of these measurements if other dimensions ai'e ascertained by mea- 

 surements Ijetween different fixed points of the skull. 



But for the full description of all the varieties which occur, and the minuter 

 appreciation of the relations of the several parts, a more elaborate system of 

 measurement must be can'ied out. Considerable attention has in recent times 



