NO. 1521. 



MEASUREMENTS OF CRANIAL FOSSAE— HRDLICKA. 



183 



not develop in quite a large percentao-e of cases until in later, post- 

 natal life, very likely during the years of the most rapid growth of 

 the brain and the skull. However, even in view of these cases of later 

 development, it is impossible to regard the unevenness of the anterior 

 fossw, with a pronounced tendency to a moderate excess on the right 

 side, otherwise than as a principal hereditary character. 



As further data show, the predominance in length of the right 

 frontal fossa is already well marked in those anthropoid apes that stand 

 nearest to man; and it also occurs occasionally in monkeys and other 

 manniials. It is therefore a rather widely shared and ancient feature. 



The actual diliereiYfces in length of the cavities, while often small, 

 are in some cases very decided as shown in the following table. It may 

 be stated here that none of the small inequalities were included in tiie 

 lists unless clearl}" established b}^ the sharp-pointed, straight-branched 

 compass, measurements with which are free from error. 



Absolute diffirences in lem/th of the anterior fossiv; right fossa the longer in cases: 



Absolute differences in length of the anterior fosssc; left fossa the longer in cases: 



"1=4.5 mm.; 1=5.5 mm.; 1=7.5 mm. 



The inequalities are greater in favor of the right fossa; they are of 

 a smaller and restricted range in the young; they show a fair latitude 

 in the anthropoid apes, but are very small in the lower mammals 

 examined. 



Form of skull and race, it was found, are apparently not factors in 

 the development of the difierences in length of the two cavities, and 

 the same is probabl}^ true of sex. A reference to the detailed tables 

 will also show that among human and anthropoid ape adults there is 

 no regular correspondence between the variation in the relation to 

 each other of the two frontal fossse and the dimensions of the cranium. 



The next point of importance to be cleared is the relation of the 

 mean absolute length of the anterior foss^ to the size of the skull. 

 Are they not only absolutely but also relatively larger in skulls of great 

 size, and the opposite — or is the difference confined only to their abso- 



