88 University of California Puhlications in Anatomy [Vol. 2 



portion of the temporal cortex just mentioned can at present be 

 regarded as the actual "auditory projection cortex." That region 

 occupies, accordingly, the entire dorsal lip of the superior temporal 

 convolution buried in the Sylvian fossa, representing in fact the 

 ventral wall of that fossa. More orally, the auditory projection 

 cortex is limited to approximately the internal half of the upper lip 

 of the superior temporal convolution sunk in the Syhaan fossa. 

 Besides that, it would appear that a portion of the convexity of the 

 superior temporal convolution receives a certain number of auditory 

 fibers, at least the portion near the posterior corner of the Sylvian 

 fossa. Thus the auditory cortical projection area has its widest extent 

 in its caudal portion, decreasing toward its oral or rostral end, where 

 it covers only a narrow zone hidden entirely in the Sylvian fossa 

 (small, deeply shaded area ventrally to the Sylvian fissure F8 in 

 fig. 1 ; area a in figs. 2, 10, and 24, indicating more the longitudinal 

 extent of the auditory cortex than its extent over the free face of 

 the hemisphere). 



The possibility that the auditory projection cortex which receives 

 direct peripheral impulses, is somewhat wider than that delimited in 

 these investigations must be considered. The present delimitation of 

 the cortical projection center of hearing in the monkey depends on the 

 completeness of the degeneration of the auditory radiation which has 

 been caused by the experimental lesion. Considering the shape and 

 the location of the injury in Experiments I and II, it does not, on the 

 one hand, seem probable that any considerable portion of the radia- 

 tion was left unaltered, especially so in Experiment II (see figs. 50, 

 51), and on the other hand, that any other cortico-petal, e.g., callosal 

 fibers degenerated. At any rate the delimitation as given h.ere must 

 he regarded as a "minimal" possible extent of the auditory projection 

 cortex. Furthermore, the present experiments show the complete 

 absence of other afferent fibers from the between-brain to any other 

 portion of the convex face of the temporal lobe, a contention of some 

 investigators. 



Sections through the posterior portion of the auditory projection 

 region show the cortex of the upper lip of the superior temporal con- 

 volution containing in its lower layers a multitude of fine and medium- 

 sized degenerated afferent fibers approaching a fiber layer which cor- 

 responds well with the inner stripe of Baillarger of that cortical area 

 as delimited by Brodman (figs. 50, 51; see also Vogt, 1919, fi^. 59). 

 In this area the number of intracortical afferent fibers is the largest in 



