62 University of California PiiUicutions in Anatomy L^'oi- 2 



though still containing numerous thalamic fibers, occupies the greater 

 part of the convexities of both the postcentral and the precentral 

 convolutions and the nearby portions of both lips of the central sulcus 

 which do not belong to the "focal zone." A third zone occupying the 

 ' ' periphery ' ' of the common somatic sensory region of the hemisphere, 

 belonging partly to the frontal lobe and partly to the parietal lobe, 

 receives only a small number of scattered thalamo-cortical fibers. 

 But, as was said above, the transition from one zone to its neighbor is 

 a fairly gradual one. 



As to the numerical distribution of somato-sensory afferent fibers 

 to various portions or segments of both the precentral and postcentral 

 convolutions corresponding with the individual "centres" for detailed 

 or special motor acts in the precentral cortex, or to definite repre- 

 sentations of a conscious sensory function, that is, to the so-called 

 sensory "centres" of the postcentral region, there has been found 

 scarcely any appreciable difference. If there are any differences, the 

 intermediate segments of the postcentral region between the anterior 

 extremity of the postcentral-parietal sulcus and the sulcus centralis 

 receive a little more numerous thalamo-cortical fibers, while the most 

 ventral (opercular) segments of the same region are perhaps a little 

 less abundantly supplied, which also can be noticed in the accompany- 

 ing illustrations. The first mentioned segments would correspond to 

 the somato-sensory representation of the hand and of the fingers in 

 the monkey's brain (Vogt, 1919, fig. 125) and very probably also in 

 the human brain (Foerster, 1927) ; the opercular region would repre- 

 sent the tongue, the face, the neck in the monkey (Vogt), and, as 

 might be added, probably also the entire inner surface of the mouth, 

 nose, and throat (Foerster). Surely in no one of my experiments 

 is the afferent somato-sensory^ fiber supply of the opercular segments 

 of both central convolutions as abundant as might be expected ; and, 

 as a matter of fact, the somatic sensory region of the hemisphere 

 as delimited here barely reaches the Sylvian fissure. (This result 

 might be the consequence of the location of the lesion ; here, of course, 

 Experiments I, II, and V-a must be considered more than Experi- 

 ment III.) Of the most dorsal segment of the postcentral-parietal 

 convolution (that is, of the superior parietal gyrus), it is only the 

 convexity which receives a considerable number of thalamic fibers; 

 whereas, the posterior slope of that convolution hidden in the parietal 

 sulcus, and the cortex covering the inner face of the hemisphere, cor- 

 responding with the caudal portion of the paracentral lobule and with 



