1874.] Brain-surface by Induced Currents. 369 



excitations of anatomically corresponding spots produce similar or corre- 

 sponding results. From these remarkable facts and from others similar 

 to them relating to other parts of the brain to which I do not now advert, 

 it was inferred that, at the surface of the hemispheres, certain " centres " 

 are to be found, of which it is the function to originate combined or even 

 purposive movements. 



To this inference objections have been recently raised by Dr. Dupuy, 

 based on the results of experiments made by him, in which he found that, 

 after the ablation of those parts of the hemispheres which contain the 

 supposed centres, movements, similar to those described by Dr. Eerrier, can 

 still be produced by electrical excitation of the cut surface. In com- 

 menting on these counter experiments, Dr. Terrier has since pointed out 

 that the effects described by Dr. Dupuy are entirely different from those 

 observed by himself, and, particularly, that the movements produced in his 

 experiments are of an uncertain character, affecting sometimes one, some- 

 times several groups of muscles. 



As it appeared to me that, although Dr. Dupuy has failed to prove that 

 the movements he described are of the same nature with those described 

 by Dr. Eerrier, the latter has not proved that they are different, I 

 thought it necessary to make a series of experiments for the purpose of 

 clearing up this uncertainty. With this view I determined to investigate 

 the most characteristic of the combined movements, so accurately described 

 by Dr. Eerrier as produced by excitation of particular spots on the anterior 

 part of either hemisphere, by comparing them with those produced by 

 excitation of deeper parts. The results of my experiments, in which cats 

 were employed, are as follows : 



1. By removing the integument, skull, and dura mater to an extent 

 corresponding to the anterior half of the right parietal bone and the 

 adjoining thin portion of the frontal bone, an area of the surface of the 

 brain is brought into view which comprises several spots by the excita- 

 tion of which the following characteristic movements can be produced: 

 (1) E/etraction of the left fore paw, with flexion of the carpus, accom- 

 panied "by similar movements of the left hind leg. (2) Closure of the 

 left eye and elevation of the left upper lip. (3) Retraction of the left 

 ear. (4) Rotation of the head to the left side. 



The active spots for these several movements are as follows : Eor (1), 

 a point immediately behind the outer end of the crucial sulcus ; for (2), 

 the surface about the outer end of a sulcus which lies immediately behind 

 (1) ; for (3), the surface behind the sulcus last mentioned ; for (4), a spot 

 about a centim. further back on the same convolution. Movements (1), 

 (2), and (3) can be produced in the cat with very great certainty, and the 

 active spots for them are well defined. Their limits and relations are 

 in exact accordance with the statements of Dr. Eerrier. 



2. If that part of the surface of the right hemisphere which comprises 

 the active spots above mentioned is severed from the deeper parts by a 



