292 



PLATE I. 



Human brain, M., aet. 41. Orthogonal tracings of the lateral and mesial surfaces (the former 

 somewhat tilted to show the convexity) of the left cerebral hemisphere, with a representation of 

 the extent of the various areas defined therein from an examination of cortical nerve fibres and 

 nerve cells. 



In a surface diagram it is impossible to give a true idea of the extent of many of these 

 fields, because cortex concealed within fissures cannot be indicated, and unfortunately the figures 

 are especially misleading in regard to some of the most important areas ; thus the floor, not 

 the lip, of the fissure of Rolando is the boundary between the precentral and postcentral fields, 

 and accordingly the concealed portion of these areas is almost equivalent to that exposed : the 

 same applies to the calcarine or visuo-sensor}- field, while that marked " audito-sensory " is almost 

 completely hidden in the Sylvian fissure. 



