90 University of California Puhlications in Anatomy [Vol. 2 



the entire temporal cortex, though it appears larger than the narrow 

 strip covering the transverse temporal convolution. (Compare follow- 

 ing paragraph.) Moreover, that region does not receive "diffuse," 

 but well arranged and regularly distributed afferent fibers. By far 

 the larger portion of the temporal lobe including a considerable por- 

 tion of the superior temporal convolution does not, in fact, stand in 

 direct connection with subcortical regions by means of the auditory or 

 any other afferent fibers. It is evident that in the monkey Brodmann's 

 and Mauss' area 22 can in no case in its totality, as is accepted at 

 present, but only partly be homologous with the areas 41, 42', and 52 

 of the human brain (fig. 7). Although the cytoarchitectural studies 

 were unable to distinguish in the monkey brain a special area cor- 

 responding to Heschl's transverse convolutions in man (TC of 

 Economo-Koskinas), there can be no doubt that such an area exists in 

 lower primates also. (Compare Economo-Koskinas, pp. 707, 708; 

 Beck, 1929, p. 413, and 1930, p. 253, and Niessl von Mayendorf, 1930.) 



The boundaries of the auditory projection cortex as determined by 

 the present experiments are all the more remarkable since in Experi- 

 ment II a greater part of the temporal lobe was severed from the rest 

 of the hemisphere and yet only the auditory radiation, which has been 

 described, degenerated. 



The deep position of the auditory projection cortex in the posterior 

 portion of the Sylvian fossa in the ]\Iacacus, rendering this furrow 

 comparable to the calcarine fissure and to the central sulcus, accounts 

 for the discrepancies observed in various physiological experiments. 

 The anatomical experimental method of investigation — demonstrating 

 as it clearly does the position and the extent of the terminal cortical 

 area of the central auditory path — that has been used in the present 

 experiments, can serve as a reliable basis for future physiological 

 studies. (See Chapter XX.) 



2. PROBABLE FUNCTIONAL SIGNIFICANCE OF THE POSTERIOR 

 SYLVIAN RECEPTIVE REGION 



There do not exist other dependable means, except physiological 

 experiments, of determining what special function can be attributed 

 to that region of the temporo-parietal cortex stretching from the imme- 

 diate neighborhood of the undoubted auditory projection cortex (small 

 deeply shaded area a) in an occipital direction as far as the posterior 

 end of the Sylvian sulcus (lightly sha<:led area x in figs. 2, 10, and 24). 



