584 TEXT-BOOK OF PHYSIOLOGY 



human brain, though it is probable that their locations do not in all respects 

 coincide with those characteristic of the monkey or even the ape brain. In 

 the following diagrams (Figs. 250 and 251), the sensor and motor areas are 

 at least provisionally located, in accordance with recent observations. They 

 are represented as limited or bounded by a serrated line to indicate, as 

 suggested by Mills, that they are not sharply delimited, but that they inter- 

 fuse or interdigitate with surrounding regions. 



In the following paragraphs these areas are considered in the order oj 

 their development and physiologic activities. 



The Sensor Areas. The sensor areas occupy regions corresponding in 

 a general way with those of the monkey brain. 



i\The Cutaneous Area. The area of cutaneous or tactile sensibility has been 

 assigned to the post-central convolution on the lateral aspect, and to a 

 portion of the super-frontal convolution and the lower half of the para- 



CONCRLTE CONCEPT 



FIG. 250. THE AREAS AND CENTERS OF THE LATERAL ASPECT OF THE HUMAN HEMICEREBRUM. 



(C. K. Mills.) 



central lobule on the mesial aspect of the hemicerebrum. It has been 

 stated by Flechsig, who bases his statements on the results of embryo- 

 logic investigations as to the course, time of myelinization and termina- 

 tion of certain afferent tracts, that the cutaneous area must also be 

 assigned though perhaps in less degree to the pre-central convolution 

 as well. 



Clinic observations and post-mortem findings, together with the results 

 of more recent experimental investigations make it extremely probable that 

 the cutaneous area is confined entirely to the regions posterior to the central 

 fissure or fissure of Rolando. Dr. Charles K. Mills, whose skill in interpret- 

 ing the phenomena of the diseases of the brain is well known, states in this 

 connection, that "innumerable cases have been reported of lesions of the 

 motor (the pre-central convolution) without the slightest impairment of sen- 

 sibility." In many instances portions of the motor cortex of the human 

 brain have been excised by necessary surgical procedures. In these cases 



