6oo THE POPULAR SCIENCE MONTHLY. 



This anatomical arrangement seems to indicate that the peripheral 

 substance, and not the central mass, is the point of motor stimulation 

 and the seat of sensitive impressions. It is everywhere admitted that 

 the brain is the organ of thought and will ; but for a long time it was 

 believed that the central mass was the important portion, and the con- 

 volutions were disregarded. Hippocrates thought they were only a 

 gland. Malpighi and Vieussens thought the same. Ruysch, from 

 their vascularity, considered them as a simple sanguineus network, and 

 Boerhaave and Haller adopted this conclusion. Vic d'Azyr was the 

 first to examine their structure ; then came Baillarger, Ehrenberg, Pur- 

 kinje, Meynert, Luys, Betz, and Charcot, who revealed their precise 

 anatomy. As to their physiology. Gall taught that intelligence is a 

 function of the convolutions ; Desmoulins added that the degree of 

 intelligence is in proportion to their number and depth ; and Broca, 

 taking the ideas and facts of Dax and Bouillaud, announced the first 

 discovered localization that of articulate language in the third left 

 frontal convolution. 



In 1870 two German scientists, Fritsch and Hitzig, passed a cur- 

 rent of electricity across the head and behind the ears of a living 

 subject, which caused movements of the eyes. They referred these 

 movements to stimulation of the gray matter of the convolutions, and 

 set about the verification of their hypothesis. From their experiments 

 they drew the three following fundamental propositions : 1. There 

 are in the head convolutions that may be excited by electricity, and 

 this excitation is followed by the production of determinate move- 

 ments depending upon the point excited ; other parts being excited 

 "without producing movements. 2. The points, which under stimula- 

 tion induce action in such and such muscular groups, occupy a very 

 limited portion of the cerebral surface. 3. The extirpation of such a 

 point of the surface, known to be a center of distinct movements, 

 paralyzes these movements. 



The theory of cerebral localization assumes as proved that there is 

 in the brain a peripheral portion devoted to the production of move- 

 ments a motor region ; and another where stimulation is not followed 

 by movements a non-motor region. It further assumes that the 

 motor region may be subdivided into a certain number of small tracts, 

 definitely circumscribed, each of which presides over the movements 

 of a certain muscular group and this group alone. Ferrier, stalling 

 with these conclusions, proceeded with the research, and seems to have 

 established that the convolutions, in man as well as in the lower ani- 

 mals, may be separated into three regions : the anterior, devoted to 

 intellectual functions ; the middle portion, charged with the motor 

 innervation of the body ; and a sensitive region where are received the 

 impressions made upon the sense-organs by the external world. To 

 show how Ferrier reaches and justifies these conclusions is the object 

 of this article. 



