400 THE EXTERNAL CONFIGURATION 



(1.) Though the situation of the * primary ' Fissures 

 is subject to little variation in the two Hemispheres, 

 still in the more highly convoluted Brains many of the 

 separate Convolutions are apt to present differences in the 

 number and arrangement of their minor folds or indenta- 

 tions. Hence slight differences in the appearance of 

 corresponding Convolutions on the two sides of the brain 

 are occasionally to be met with; although in different 

 individuals the regions in which dissimilarity is most 

 marked are by no means necessarily the same, nor is 

 the greatest complexity always to be found on the same 

 Hemisphere in these different regions. 



Much more has yet to be learned in regard to these 

 points, but the broad conclusion is thoroughly warranted 

 that this asymmetrical development of the convolutions is 

 only a little more marked in the lower Human Kaces than 

 it is amongst the higher Apes, and that it becomes dis- 

 tinctly most marked in the more highly convoluted brains 

 pertaining to representatives of the higher or more 

 civilized Human Eaces. 



(2.) It has been noted by various anatomists that the 

 left Hemisphere is very frequently slightly longer than its 

 fellow, so that the tip of the left Occipital Lobe is apt to 

 project distinctly behind that of the right side. 



(3.) The writer noticed about fifteen years ago that a 

 distinct difference in the shape of the tips of the Occipi- 

 tal Lobes frequently exists* that of the left side being 

 generally tapering and rudely conical, whilst the right is 

 often rather flattened at the end and has at its inner border 

 a groove-like depression about Jth of an inch in diameter 

 (fig. 147). The direction of the groove from below up- 

 wards, is also inwards and forwards. 



* And subsequently called attention to it in " Trans, of Patholog. 

 Soc.," 1869, vol. xx. p. 4. 



