iv] Poxt<-<'iitrl or Scxxorji Area 79 



further, as it is fully and must ably dealt with by Professors Sherrington and Grunbaum suffice 

 ii tn say that I accept the' finding of these observers as correct. 



Assuming, therefore, that in the ape family and more particularly in that class in the 

 phylogenetic series which approaches most closely to the human being, the postcentral gyms 

 is devoid of motor function, \ve have next to consider whether a parallelism with man exists. 



While the evidence on this point is hardly conclusive, reasons are not wanting for believing 

 that it does. In the first place, the facts brought to light by histological research are, to 

 say the least of them, cogent, because it can be demonstrated with unequivocal certainty 

 that in both man and the anthropoid ape the postcentral gyrus possesses a remarkable simi- 

 larity of structure ; moreover, in both cases the structure of the convolution differs entirely 

 from that of the precentral. Next, in regard to the effects of electrical excitation of the 

 human brain, it is of course information under this heading which would prove most valuable 

 in obtaining a conviction concerning the above-mentioned parallelism, but unfortunately such 

 a short period has elapsed since the publication of Professors Sherrington and Grunbaum's 

 researches, that their discoveries have hardly become sufficiently well-known for surgeons to take 

 full advantage of them, and at the present moment I am not aware of any published account 

 giving the results of the application of the necessary special method of excitation to the 

 human brain; however, from private information received, I understand that two well-known 

 surgeons during the performance of operations on the brain have had occasion to put this 

 method to the test, and contrary to previous experience in the human subject, have found 

 the postcentral gyrus as inexcitable as it is in the ape. I am also led to believe that one 

 of these operations involved a partial ablation of the postcentral gyrus, and this procedure 

 was likewise unattended by any motor paralysis. Of ordinary clinical observations bearing on 

 this question I shall have occasion to write later, here I would merely mention that this is the 

 only case, so far as I know, in which the effects of a localised lesion in the postcentral gyrus 

 have been carefully studied, since the publication of Professors Sherrington and Grunbaum's work. 



From the foregoing it is plain that I am strongly impressed with the idea that as in 



the ape, so also in the human being, the postcentral gyrus is to be excluded from the 



motor area, and I am also satisfied that it only needs a few more observations on the human 

 brain firmly to establish the existence of this parallelism. 



Taking it for granted then that the postcentral gyrus plays no direct part in the control 

 of volitional m&vernent, the way is now cleared for a consideration of the function which 

 this field possibly subserves, and that a field equipped with such a distinctive fibre arrange- 

 ment and cell lamination does not stand related with some special and important function it 

 is impossible to believe. 



To simplify matters I might at the outset state that as a result of histological and 

 pathological studies coupled with a general consideration of the work of others, and parti- 

 cularly that of clinical observers, I have become impressed with the idea that it is in the 

 postcentral gyrus that we have to look for the centre, or arrival platform, for the reception 

 of sensory stimuli of the common order which have travelled up from peripheral parts; 

 consequently, the line of argument taken in the following pages will be directed to the 

 question of the cortical localisation of " common sensation." 



Now it must be patent to all who are interested in questions of cerebral localisation, 

 that on account of the prevailing diversity of opinion, and the remarkable paucity of definite 



