HEAD OF THE FffiTUS. 135 



— Cuvier's method consists iu dividing the skull vertically, and 

 establishinf a comparison between the area of the cranium and 

 that of the face. In a well-formed Caucasian he finds the area 

 of the cranium, quadruple that of the face. In the Mongolian 

 variety, he found the area of the face had increased over this 

 proportion one-tenth, in the Negro, one-fifth ; in monkeys, one- 

 half. Tiedemann has adopted a plan of measuring the capacities 

 of different crania, by filling them with seeds from the occipital 

 foramen, and subsequently measuring their contents. This 

 method as well as some others, has been employed for the same 

 purpose by Prof. S. G. Morton of this city, in the preparation of 

 his elegant and interesting work on Crania Americana, and the 

 results have been so carefully detailed by him, as to leave hence- 

 forth little to be wished upon a subject which has excited much 

 attention among physiologists. The whole capacity of the 

 cranium is found on an average, greater in the Caucasian variety 

 of the human race, than in any other. 



The Head of the Fcetus. 



In the foetus, those bones, which form the vault of the cra- 

 nium, originally consist of one plate only ; which is composed 

 of radiant fibres. 



At birth, the os fronds consists of two pieces, which join each 

 other in the middle of the forehead. 



The parietal bones are each in a single piece ; but they are 

 incomplete at their edges and their angles. 



The temporal bones have no appearance of mastoid or styloid 

 processes. Instead of a meatus auditorius externus, there is a 

 bony ring in which the membrana tympani is fixed. The 

 squamous and petrous portions, and this ring, are originally 

 formed separate ; but at the period of birth they often adhere to 

 each other. 



The OS occipitis is composed of four pieces: the first and 

 largest, extends from the beginning or angle of the lambdoidal 

 suture to the upper edge of the great occipital foramen. Each 

 side of the foramen, and the condyle on it, is formed by a 

 distinct piece. The front part is formed by the cuneiforn': 



