CHAPTER III. 



PRECENTRAL OR MOTOR AREA. 



IN November 1901, Professors Sherrington and Griinbaum published their preliminary 

 account of some experiments conducted on all the known species of anthropoid apes, and 

 expressed the conviction that previously accepted views on the topographical distribution of the 

 motor area needed extensive modification. The results of these experiments may be briefly 

 stated as follows. Employing unipolar faradisation as the method of cortical excitation, it 

 was discovered that the responsive area was confined to the precentral convolution, and, to 

 a small coterminous portion of the paracentral lobule, on the mesial surface of the hemisphere. 

 The area included the whole length of the precentral convolution, extending over its free width 

 and continuously round into, and to the bottom of the fissure of Rolando. 



Obviously the most noteworthy and in fact the fundamental discrepancy between these 

 results, and those of others who have worked in the domain of experimental neurology, is the 

 reversal of the doctrine concerning the activity of the post-central gyrus, for neither did 

 stimulation even with relatively strong currents of the cortex of this gyrus excite movements, 

 nor was an ablation of the same convolution, or, I should say. parts thereof, followed by any 

 motor paralysis ; moreover, the application of the same method to members of lower ape 

 families was attended by precisely similar results. Another - difference, of less importance, is 

 that according to these experiments the excitable area in an anterior direction is much less 

 than the results of previous workers led us to suppose. 



A full and detailed account of these extremely important and valuable investigations will 

 appear shortly in the Transactions of the Royal Society, and therein will be found a conclusive 

 and almost incontrovertible array of supplementary evidence in support of the conviction expressed 

 in the preliminary communication. 



I have made special reference to this research of Professors Sherrington and Griinbaum, 

 because their results have a very important bearing on the histological studies which form the 

 groundwork of my observations on this area ; moreover, I am responsible for the addendum 

 embodied in their publication, which gives a short account of a histological examination of the 

 brains of some of the animals which they experimented upon. This histological investigation 

 I undertook with the object of ascertaining whether the cortex of the parts which responded 

 to electrical excitation could be differentiated from the " silent " parts, by the possession of 

 any distinctive histological structure ; and. leaving details for later reference, I may here mention 

 that no small measure of success attended the effort, for I think I was able to prove to Professor 

 Sherrington and Doctor Grunbaum's satisfaction, that it is just as possible to define the motor 

 area on the histological bench, as on the operating table. 



