222 CEREBRAL LOCALIZATION 



however, whether the precentral or motor cortex 

 takes any share in appreciating cutaneous sensation. 

 If so, it is quite secondar}/ to the part played by the 

 postcentral convolution. 



It is very difficult to be sure to what extent 

 animals feel after the removal of small parts of 

 either the postcentral or precentral convolutions, 

 and very diverse views have been expressed ; it is 

 quite certain that a small lesion does not induce com- 

 plete aneesthesia. It is probably wiser to put faith 

 principally in the human evidence on such a subject. 

 It is abundantly proved that lesions involving the 

 ascending parietal convolution almost always cause 

 a certain degree of interference with sensation, never 

 amounting to a complete hemianaesthesia, which, 

 indeed, occurs only in hysteria, or very transitorily 

 after an apoplectic stroke. Bergmark quotes thirty- 

 three cases of lesions of this gyrus with sensory 

 symptoms but no paralysis. 



Gushing excited the postcentral convolution in 

 two conscious patients who had previously been 

 trephined, by unipolar faradic stimulation. He 

 found that the brain itself was devoid of any sort 

 of feeling, but that sensations of stroking, tingling, 

 or warmth were produced, referred to the hand of 

 the opposite side. The sensation was quite well 

 defined and localized ; one area corresponded to the 

 index finger, and another to the back of the hand. 

 When the electrode was applied in front of the fissure 

 of Rolando instead of behind, the fingers or hand 

 moved, but there was no sensation. An incision in 

 the postcentral convolution was quite painless, and 



