172 



HUMAN EMBRYOLOGY AND MORPHOLOGY. 



kind. The cephalic index is used to express the shape of the head. 

 It states the proportion that the breadth bears to the length of the 

 skull (Figs. 138 and 139). The length or long diameter of the 

 skull is measured from the glabella to the inion (external occipital 

 protuberance) ; the breadth or widest diameter is measured 



Fig 138. 



60-75% 



80-90% 



Fig. 138. — Diagram of a Long-head (Dolichocephalic). 

 Fig. 139. — Diagram of a Short-head (Brachycephalie). 



between the widest points' — the parietal eminences. If the length 

 of a skull is 100 mm. and the breadth 75, the cephalic index of 

 that skull is 75, i.e. the breadth is 75°/ of the length. Human 

 races, on an average, are either Dolichocephalic (long-headed), the 

 breadth being 75°/ or less of the length; Brachycephalie, in 

 which the breadth is 80°/ o or more of length; or Meso-cephalic, 

 in which the breadth is between 75°/ D and 80°/ o of the length. 



The English people have an average index of 75, the South 

 Germans 83, but it must be remembered the individuals vary 

 widely. It will be seen that the topography of the brain, worked 

 out by German surgeons, cannot be applied to the longer English 

 heads without modification. 



The Facial Angle is the angle at which the face projects from 

 the base of the skull (Fig. 140). The skull consists in man, as 

 in all mammals, of two parts — the facial part, which carries the 

 teeth and is developed according to their size, and the brain 

 capsule, which depends on the size of the brain. The smaller the 



