76 University of California Publications in Anatomy [^'ol. 2 



external face. In its posterior portion the somato-sensorj^ cortex even 

 overlaps for a short distance areas 23 and 24 of Brodmann. It is 

 fairly safe to accept the caudal boundaries of the somatic sensorj^ 

 cortex in the parietal lobe determined here as closely approaching the 

 existing limits of that cortex. The same certainty does not exist with 

 reg:ard to the anterior boundary ; and the possibility cannot be excluded 

 that a portion of the thalamo-cortical radiation springing' from the 

 anterior thalamic segment might spread more orally over the frontal 

 lobe. This particular question must be investigated by special experi- 

 ments. At any rate, the extent of the somatic sensory cortex as found 

 in these investigations must be recognized as the ' ' minimal ' ' somatic 

 sensory' region of the hemisphere. 



5. COETICAL TEEMINATIONS OF THE SOMATO-SENSORY AFFERENT 



FIBERS 



A feature common to all intracortical terminations of afferent fibers 

 both in the precentral and in the postcentral cortex is: a somewhat 

 irregular course seldom corresponding with the regularly arranged 

 vertical ' ' radiated bundles, ' ' the latter being the entering and outgoing 

 association, callosal, and efferent fibers. For the most part the exogen- 

 ous afferent fibers have an oblique ascending course through the lower 

 strata of the cortex toward both stripes of Baillarger. In the 

 voluminous precentral cortex the degenerated afferent fibers usually 

 have, for long stretches, a somewhat straighter course and ascend 

 directly from the subcortical white substance, cutting at sharp angles 

 the actual ' ' radiated bundles. ' ' In the thinner postcentral cortex the 

 exogenous afferent fibers ascend more gradually toward the stripes of 

 Baillarger, many fibers exhibiting here a horizontal direction, more or 

 less parallel with the cortical layers. Everywhere the afferent fibers 

 reach the lower stripe of Baillarger with many fine fiber segments 

 penetrating into the lamina interstriata and reach the upper stripe 

 of Baillarger. Both stripes of Baillarger, especially in the cortex of 

 the bottom of the sulcus centralis, are filled with countless fine, aiid a 

 few somewhat coarser, blackened particles and detritus of the disin- 

 tegrated myelin and with short segments of degenerated fibers. This 

 is considerably less pronounced or entirely absent in the cortex cover- 

 ing the convexities of both the precentral and postcentral convolutions. 

 A few delicate and fairly long horizontal degenerated fibers were also 

 seen in the region of the stripes of Baillarger itself. In the upper 



