160 Temporal Lobe and Auditory Areas [CHAP. 



REMARKS ON THE TEMPORAL CORTEX IN THE ANTHROPOID BRAIN. (Plate II.) 



It is remarkable how closely the distribution of these areas in the brains of the higher 

 ape resembles that found in the human being ; indeed, it was while examining this region 

 in the brain of the orang that my attention was first directed to the existence of the 

 extraordinary fibre-wealth of the cortex at the hinder end of the Sylvian fissure, and it 

 was this discovery which led me to make a thorough investigation of the same region in the 

 human brain. 



Concerning the naked eye appearance of the anthropoid brain I have satisfied myself 

 that in the orang and chimpanzee elevations exist on the Sylvian side of the first temporal 

 convolution which are homologous with the transverse temporal gyri of the human brain. 

 These gyri may not stand out so prominently as they do in the human brain, but they 

 can be readily distinguished, supporting the hinder end of the superior temporal gyrus after 

 the fashion of buttresses, and lying at a distinctly higher level than the more anteriorly 

 placed insula proper. Further, microscopic examination absolutely settles the homology, for in 

 the case of the anthropoid brain the area of cortex characterised by the possession of a 

 special wealth of fibres of large calibre, is confined in an exactly homologous manner to the 

 above-mentioned transverse gyri, and is again practically entirely submerged in the hinder 

 half of the Sylvian fissure, only just peeping out on to the surface at the posterior extremity. 



Also the external field of cortex, alluded to as possessing an intermediate type of 

 arrangement, is in its main extent again confined to the first temporal gyrus; but anteriorly 

 it seems to extend slightly further forwards than it does in the human brain, and posteriorly 

 it tends to ascend on to the opercular part of the supramarginal gyrus lying immediately 

 above the posterior extremity of the Sylvian fissure. 



I can conclude by saying that these fields are more readily differentiated and mapped 

 out in the anthropoid than in the human brain, not only because the brain is smaller, 

 but because there is less confusion of the gyral arrangement in the posterior corners of 

 the Sylvian fissure, making the part difficult to examine in serial section. 



FUNCTIONS OF THE TEMPORAL LOBE. 



It has been proved beyond doubt that auditory impulses are first received as crude 

 sensations and then converted into conscious perceptions in some part of the temporal 

 lobe, and it also appears that the part principally concerned in this process is the first 

 or superior temporal gyrus ; but as yet, no worker, whether in the domain of experimental 

 physiology, pathology, or anatomy, has succeeded in assigning sharp limits to the auditory 

 area ; nor have successful efforts been made to divide the auditory, like the visual field, 

 into two distinct territories, one adapted for the primary reception of crude sensations, the 

 other for the further elaboration and transmutation of these impulses into conscious psychic 

 perceptions. 



For the purpose of ascertaining whether previous results can be correlated with the 

 facts of histology set forth in this research, we will next take a general survey of the 

 literature on the subject and consider it under three headings, (1) the experimental, (2) the 

 clinico-pathological, and (3) the embryological and anatomical. 



