102 University of California Publications in Anatomy l^^^- 2 



well, segment alongside segment. The entire auditory radiation enters 

 the white matter of the superior temporal convolution, and only that 

 convolution. Here the auditory fibers occupy exclusively the upper 

 half of the white matter close to the cortex lining the floor of the 

 Sylvian fossa, leaving free the ventral third or half of the white matter 

 along the cortex of the superior temporal sulcus (as do the visual 

 fibers along the striate cortex; see Visual System). Some of the audi- 

 tory fibers penetrate through the ventral "spur" of the claustrum 

 and enter the capsula extrema to reach the cortex of the ventral wall 

 of the Sylvian fossa. The arrangement of the auditory fibers in the 

 white matter of the superior temporal convolution is remarkably regu- 

 lar, sectors of parallel fibers forming a thin fiber sheet. The entire 

 auditory radiation enters the cortex of the upper lip of the first tem- 

 poral convolution, in other words, the ventral wall of the Sylvian fossa. 

 Only a few fibers reach the convexity of the superior temporal con- 

 volution on the free face of the temporal lobe. Neither the ventral 

 wall of that convolution nor any other portion of the temporal cortex 

 (middle, inferior temporal convolution) receives fibers of the auditory 

 radiation, or any other afferent fibers from the subcortical nuclei. 



No portion of the auditory radiation has been found to cross to the 

 opposite hemisphere through the corpus callosum. (Compare Somatic 

 Sensory System and Visual System.) The semidecussation of the 

 central auditory path is achieved at lower levels of the neuraxis, prin- 

 cipally in the medula oblongata and in the pons. (See my papers, 

 1925 and 1927.) 



2. BOUXDAEIES OF THE AUDITORY PROJECTION CORTEX. INTERNAL 



ORGANIZATION, FUNCTION, AND DISTURBANCES OF THE 



AUDITORY RADIATION AND OF THE AUDITORY 



PROJECTION CORTEX 



According to the results here reported, the auditory projection cor- 

 tex (deeply shaded area a in figs. 10 and 24) is a fairly well delimited 

 portion of the temporal cortex, though its boundaries do not seem to 

 be as sharp as those of the visual cortex. In this respect the auditory 

 projection cortex resembles the somato-sensory cortex. The greater 

 portion of the auditory projection cortex is buried in the Sylvian 

 fossa, a small portion only emerging on the free face of the superior 

 temporal convolution. The greatest number of the auditory fibers 

 enter a small zone in the posterior corner of the Sylvian fossa, where 



