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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXII. 



anterior cavities; and the differences are in most cases very decided. 

 Individually, the cases where the left fossa is not the longer are in 

 nearly all the series comparatively infrequent, namel}^: 



Length of postero-super lor fossa on the two sides in human adults. 



Skulls. 



Adults: 



Whites, males — 



Dolichocephals 



Mesocephals 



Brachycephals 



Whites, females — 



Dolichocephals 



Mesocephals 



Brachycephals 



Indians, males — 



Dolichocephals 



Brachycephals 



Negroes- 

 Males, dolichocephals 



Females, dolicho-and mesocephals 



Right pos- 

 tero-superior 

 fossa longer 

 (per cent of 



cases). 



Fossse equal 



(percent of 



cases). 



Left pos- 



tero-superior 



fossa longer 



(percent of 



cases). 



The left fossa is shown to be the longer in from 50 to 90 per cent 

 of the cases in the various series, or in over 72 per cent, or nearly 

 three-fourths of the crania, if we take all the 130 skulls together. The 

 middle fossas, it was seen, showed in 41 per cent, and the anterior 

 cavities in 63.5 per cent, an excess in the length on the right side. 



Among the human young and the anthropoid apes, and in other 

 mammals, the conditions were as follows: 



Length of postero-super ior fossa on the two sides in human fetuses, etc. 



Skulls. 



40 human fetuses and young . . . 



13 anthropoid apes 



7 monkeys and other mammals 



In the human young there is a much larger percentage than in adults 

 of postero-superior fossse of equal length, showing again, as wnth the 

 middle and anterior cavities, that the inequalities are often of later 

 development. In the present case this seems to be true particularl}^ of 

 the excess of length on the left side. In the anthropoid apes the con- 

 ditions are not much different from those in human adults, which 

 indicates that the predominance of excess of length in the left postero- 

 superior fossa, and of that portion of the cerebrum which enters into 

 it, is an ancient feature which has not been acquired and has scarcel}^ 

 been modified in man. Among monkeys and lower mammals there 

 seems to be less regularity in the unevenness of the postero-superior 



