312 



MORPHOLOGY OF THE CEREBRAL CONVOLUTIONS. 



more tortuous than is usually the ease in the negro. In highly convoluted white 

 brains this fissure often becomes very tortuous and much broken, whilst in those of 

 less convolutional development it assumes a simple character, and, although inter- 

 rupted, can be readily distinguished as a whole, Plate XLIII, figs. 1 and 2. In 

 the Mongolian, so far as can be determined from a single specimen, Plate XLI, 

 figs. 3 and 4. it presents quite as tortuous and complicated an appearance as 

 found in the Caucasian. 



The brain of the negro, Plate XLII, fig. 1, illustrates another very interesting 

 fact in this connection. In this brain the interparietal fissure temiinates'directly 

 in the Sylvian at its upper extremity, so that in this brain the lobule du pit mar- 

 ginal (supra-marginal lobule) which Gratiolet asserted, and other writers have 

 repeated, was characteristic of the human brain as distinguished from the Simian 

 brain, is entirely absent on the surface, the slightest trace of its presence being 

 indicated by the very small fold, P 2 , which lies entirely concealed within the inter- 

 parietal fissure in its natural condition. I have slightly widened this fissure by 

 pushing aside its two borders in order to bring this concealed fold into view. This 



Fig. 13. 



Fig. 14. 



Man. 



Lemur. 



is a very interesting specimen, since it shows that we cannot make any absolute dis- 

 tinction between the simian and human brain. In the brain of the negro, Plate 

 XLI, fig. 1, this concealed fold has come to the surface, but exists as a simple small 

 quadrangular lobule, P 2 . In the brain of the mulatto, Plate XLIV, fig. 1, it will 

 be found well developed, assuming the character found in the white brain. In the 

 Chimpanzee, Plate XXXIX, fig. 4, P 2 , it is also well developed. Here, then, can 

 be traced a perfect series as regards the development of this supra-marginal lobule, 

 from the monkeys, through the Anthropomorpha, thence to the brain of the negro 

 by intermediate steps to the condition as found in the brain of the Caucasian race. 

 I believe that an attentive study of a large number of negro brains will clear up 

 many points in respect to the comparison of the human and anthropoid brains. I 

 have especially found such comparisons of the greatest value in unravelling the 

 complexities of convolutional configuration in the human occipital lobe. 



