DIFFERENTIAL CHARACTERS FORM OF SKULL. 



091 



taken at 100, the transverse diameter varies from 98 or 99 to 02. The num- 

 ber expressing the proportion of the transverse to the longitudinal diameter 

 of the brain-case is termed the cephalic index. Those people who possess 

 crania with a cephalic index of 80 and above are called brachycephali ; 

 those with a lower index are dolichocephali. 1 



834. Among the rudest tribes of Men, hunters and savage inhabitants of 

 forests, dependent for their supply of food on the accidental produce of the 

 soil, or on the chase among whom are the most degraded of the African 

 nations, and the Australian savages a form of head is prevalent, which is 

 most aptly distinguished by the term prognathous, indicating a prolongation, 

 or forsvard extension of the jaws (Fig. 371). This character is most strongly 

 marked in the Negroes of the Gold Coast, whose skulls are usually so formed 

 as to give the idea of lateral compression. The temporal muscles have a 

 great extent, rising high on the parietal bones; the cheek-bones project for- 

 ward, and not outward ; the upper jaw is lengthened and projects forwards, 

 giving a similar projection to the alveolar ridge and to the teeth ; and the 

 lower jaw has somewhat of the same oblique projection, so that the upper 

 and lower incisor teeth are set at an obtuse angle to each other, instead of 

 being nearly in parallel planes, as in the European. From the shape of the 



FIG. 371. 



Profile and basal views of the Prognathous Skull of a Negro. 



upper jaw alone would result a marked diminution in the facial angle, meas- 

 ured according to the method of Camper; but this diminution is far from 

 being sufficient to approximate the Ethiopian races to the higher Apes, as 

 some have supposed it to be ( 24). Independently of the diminution of the 

 facial angle resulting from the projection of the upper jaw, it is quite certain 

 that in the typical prognathous skull there is a want of elevation of the fore- 

 head ; but it does not appear that there is a corresponding diminution in the 

 capacity of the cranial cavity, the retreating form of the forehead being partly 

 due to the general elongation of the skull in the antero-posterior direction. 

 Nor is it true, as stated by some, that the position of the foramen magnum in 

 the Negro is decidedly behind that which it holds in the European, in this 

 respect approaching that of the Apes ( 21); since, if due allowance be 

 made for the projection of the upper jaw, this aperture is found to have the 

 same position in the prognathous skull as in the oval one namely, exactly 

 behind the transverse line bisecting the autero-posterior diameter of the base 

 of the cranium. The prognathous skull is further remarkable for the large 

 development of the parts connected with the organs of sense, especially those 



1 Huxley, Anatomy of Vertebrated Animals, p. 495. 



