26 C. U\ M. Poyntcr 



the brain of Chauncey Wright. Riidinger (1882) declared regard- 

 ing the lower races, that, until a great many more brains of the 

 so-called lower races had been studied, we could not say whether 

 an exposed insula w^as a characteristic of such brains. In view 

 of all the investigations so far made, it is safe to say that for the 

 individual a covered insula does not mean high mentality or race. 

 Symington's (1901) interpretation of the ditTerence between man 

 and the apes would furnish an explanation for all the indications 

 of low order of development that an exposed insula would seem 

 to imply. " The fronto-parietal operculum presses down and 

 backward, resulting in the depression of the fissura Sylvii — farther 

 to judge from the oblique direction of the fissure in apes the 

 condition is peculiar to man — due to the differentiated hand and 

 face centers. The greatest increase of cerebral surface is in the 

 association centers of Flechsig." Except for speech, there is rela- 

 tively no great increase in the motor demands of man over idiots 

 and apes. 



Sulcus Centralis: Contrary to the opinion of Gratiolet, Bischoff 

 and others the sulcus centralis should be considered the posterior 

 boundary of the lobus frontalis. As in the case of the fissura 

 Sylvii, I will not quote the various indices and measures, for the 

 divergence of methods makes a comparison impossible. 



Usually the sulcus centralis begins at a short distance above the 

 fissura Sylvii, but in a variable percentage of cases it is entirely 

 or partially confluent with the Sylvian fissure. Eberstaller be- 

 lieves that such a confluence is established through the sulcus 

 subcentralis anterior or posterior. 



The first report of a communication between the central and 

 Sylvian fissures was made by Turner (1866), while Parker 

 (1879) quotes Bischoff (1868) as saying that such a confluence 

 never occurs. IMikloucho-lMaclay (1884) reported confluence 

 twice on the right of the brains of three Australians, and ex- 

 pressed the opinion that the condition was not uncommon among 

 natives. Benedikt (1879) found in 19 per cent, of the cases 

 (criminals) examined, a shallow connection with the fissura 

 Sylvius. Giacomini found this connection twenty-one times in 

 336 hemispheres, Retzius in 23 per cent., Saporito in 5 per cent., 



370 



