iv] Postcentral or Sensor;/ Area 97 



the conclusion to be arrived at until a laborious examination and comparison of the sound and 

 diseased hemispheres have been made. Now the cases which I have subjected to examination are 

 two in number, one of amputation of the leg, and one of amputation of the hand (Cases 1 and 3 a, 

 Precentral Area), and the method followed was this. Corresponding portions of the postcentral 

 gvrus were taken from the right and left hemispheres, and serial sections of a thickness of 20 fj. cut 

 on a freezing microtome and stained tor nerve cells. In successive series of not less than 10 sections, 

 fields measuring 1 mm. in the horizontal direction were taken and the contained large pyramidal 

 cells counted, the enumeration was extended to both layers of large pyramidal elements, and 

 those cells only which showed a clear nucleus and nucleolus were included. Counts were 

 made in this way from three parts of the section, the Rolanclic wall, the free surface, and the 

 posterior wall. 



In both these cases the enumeration revealed a deficiency in one sectional situation only, 

 viz., on the wall of the Rolandic fissure of course in the hemisphere opposite to the amputation 

 the reduction in number affected both layers of large pyramidal cells, and the loss varied between 

 o() and 4.5 per cent. 



Concerning the distribution of this change it was interesting to find that it lay approximately 

 on the same horizontal level as the part in which the giant cells of the cortex exhibited 

 "reaction a distance." That is to say, in the case of amputation of the leg at the knee joint 

 the affected field embraced the hinder part of the paracentral lobule and about the upper sixth 

 of the postcentral gyrus, while in the case of amputation of the hand it involved, roughly 

 speaking, the lower third of the same gyrus. 



I should be going too far if I founded conclusions on these two cases alone, but in 

 combination with other evidence, and especially with the disclosures in cases of Tabes, they 

 must be considered worthy of record and favourable to my general thesis. In particular they 

 strengthen my statement that the cortical sensory areas for different parts of the body lie on 

 a level with the motor fields controlling muscles in corresponding parts. 



A DISCUSSION OF THE CLINICAL AND EXPERIMENTAL FINDINGS BEARING 

 ON THE FUNCTIONS OF THE POSTCENTRAL GYRUS. 



The extended reign of the doctrine of former experimenters to the effect that the two 

 central gyri share the same office has resulted in such an entanglement of the evidence available 

 tor the purpose of explaining the functions of one or the other of these gyri individually, that 

 it is quite impossible to unravel it and consider that pertaining to either separately and on its 

 own platform. 



Having already mentioned that numerous speculations have been made and advocated on the 

 question of the cortical localisation of sensation, I can now add that, roughly speaking, present- 

 day opinions are divided between two schools of observers ; the first of these, led by Munk, 

 Luciani and Seppilli, Bechterew, Dejerine, Long, . and Mott, maintain that the zone which 

 responds to electrical excitation is at the same time the seat of sensory functions, in other 

 words, that the two functions are commingled in the one area; the second school, headed by 

 von Monakow, Mills, Redlich, Charcot, and Pitres, and including Ferrier, Horsley, and Schafer, 

 argue that motion and sensation have distinct and separate representation. 



r 13 



