ON THE MAMMALIAN NERVOUS SYSTEM. 



329 



any electrical change in the cord, i.e., the pyramidal tract, really belonging to the 

 lower limb, when other parts of the cortex were excited. As will be now shown, our 

 instrument gave no indications of such diffused effects, but in this relation we must 

 draw attention to the animals used (Cat and Monkey). 



Considering that the minute differentiation of efferent motor function in the cortex 

 of the Cat is relatively insignificant compared to that in the Monkey, we employed 

 the former animal for the preliminary investigation of the accuracy of the general 

 position which is involved in our first statements. But we also found in the Cat that, 

 while with a given strength of excitation, stimulation of the lower limb cortical area 

 gave the definite result of a movement of two divisions in the electrometer (the con- 

 nection of the cord, &c., being as stated before), the excitation of the occipital lobe 

 and the temporo-sphenoidal lobe respectively gave no result at all. Upon this point 

 it may be remarked that in some instances we were able in the Cat even to differen- 

 tiate, as we easily could do in the Monkey, between the upper limb and the lower 

 limb areas. That is to say, that if the dorsal cord were observed, we got a well- 

 marked effect by exciting the lower limb focus (as indicated by FERRIER), whereas 

 excitation of the fore limb focus produced no visible change in the cord's state, as 

 evidenced by the electrometer. 



Thus the following facts were noted in the Cat (126). 



CORD led off at Lower Dorsal Region. 



. Turning now to the Monkey, we carried this mode .of investigation still further by 

 the employment of minimal stimuli. The following general result was obtained. The 

 dorsal cord being observed, the greatest effect was produced when the excitation was 

 applied to the centre of the lower limb area, i.e., just at the hallux focus,* and this 

 effect diminished as the electrodes were removed from that point towards the mesial 

 surface of the hemisphere or downwards over the convex surface towards the superior 

 frontal sulcus. (See Plate 32.) It was interesting to observe that opposite this sulcus, 



MDCOCXOI. E. 



* BEEVOR and HORSLET, ' Phil. Trans.,' 1890, &c. 



2 u 



