370 On the Excitation of the Brain-surface. [June 11, 



nearly horizontal incision made with a thin-bladed knife, and the instru- 

 ment is at once withdrawn, without dislocation of the severed part, and 

 the excitation of the active spots thereupon repeated, the result is the 

 same as when the surface of the uninjured organ is acted upon. 



If a similar incision is made in a parallel plane, but at a lower level, 

 this is not the case ; but on removing the flap and applying the electrodes 

 to the cut surface, it is found that there are on it active spots, which, as 

 regards the effect of excitation, have the same properties as the active 

 spots previously observed on the natural surface, and that the latter have 

 the same topographical relation to each other as the former. 



3. In a brain hardened in alcohol a needle plunged vertically, i. e. at 

 right angles to the surface, from the active spot for retraction of the 

 opposite ear, reaches the posterior part of the corpus striatum at a 

 depth of from 10 to 12 millims. If a horizontal incision is made in 

 the living brain, at this depth, and is met by two others, of which one is 

 directed antero-posteriorly and the other transversely, and the part 

 comprised within the incisions removed, a surface of brain is exposed in 

 the deepest part of the wound which corresponds to the outer and upper 

 part of the corpus striatum*. If now the electrodes are applied to this sur- 

 face, the movements (1), (2), (3) are produced in the same way as before, 

 but more distinctly ; the active spots are quite as strictly localized, and 

 their relations to each other are the same as at the surface the spot for 

 the movement of the extremities being in front, that for the closure of 

 the eye and retraction of the upper lip being to the outside, and that for 

 the ear behind. 



From these facts it appears that the superficial convolutions do not 

 contain organs which are essential to the production of the combinations of 

 muscular movements now in question. They further make it probable 

 that the doctrine hitherto accepted by physiologists, that the centres for 

 such movements are to be found in the masses of grey matter which lie in 

 the floor and outer wall of each lateral ventricle, is true. 



* In case it should be necessary to repeat this experiment, it will be found best (after 

 having noted the effects of exciting the surface at the several active spots and ascer- 

 tained the degree of excitation required for the production of the corresponding move- 

 ments) to proceed to remove the part of the brain containing them, so as to expose the 

 outer aspect of the anterior part of the corpus striatum at once; and then, as soon as 

 haemorrhage has ceased, to investigate the relative positions of the active spots on the 

 surface so exposed. [Since the above paper was communicated, I have ascertained that 

 at the lowest part of this surface there is a spot, of which excitation induces opening of 

 the mouth and alternate protrusion and retraction of the tongue a group of move- 

 ments which Dr. Ferrier has localized on the under surface of the brain, in front of the 

 Sylvian fissure. J. B. S., June 3, 1874.] 



