162 Temporal Lobe and Audit or i/ Areas [CHAP. 



extending right to the floor of the hinder end of the Sylvian fissure, they are crossed by 

 a number of important Sylvian branches of the middle cerebral artery which the experi- 

 menter would probably be desirous of leaving uninjured: and, granted that these gyri possess 

 the importance suggested, it is obvious that if they were not entirely removed the animal 

 would still retain a certain amount of power of auditory perception. 



Unpractised in experimental physiology, needless to say I venture with diffidence on a 

 criticism of the results of such experienced observers as Ferrier and Schafer ; however, it does 

 seem that the explanation just offered is the only one which will reconcile such pronounced 

 discrepancies. As to Munk's suggestion that Schafer's animals reacted because the sounds 

 made to attract them were so loud that they were appreciated by the sense of feeling 

 and not that of hearing, we would merely say that we give Schafer credit for being too 

 experienced an investigator to be misled in this manner. 



Some more recently published experiments of Larionow's on dogs have elicited several 

 points of interest. In the first place, he combats Munk's statement, that each centre has 

 a crossed connection with the opposite ear only, and holds that each ear is related to both 

 cortical centres ; he finds further that slight lesions of the auditory cortex are followed 

 by a loss of appreciation of single tones without impairment of common hearing, and he 

 has produced movements of both ears by faradisation of the angular gyrus, as well as of 

 the temporal lobe. 



Larionow is the first to have tried a novel and ingenious method of determining 

 auditory localisation, that is by obtaining galvanometric measurements of the current in 

 the cortex of the temporal lobes during stimulation of the peripheral organs of hearing 

 with tuning-forks ; but though it appears that variations in reaction are exhibited by 

 different parts of the temporal lobe, an unpreventable diffusion of the current, apparently 

 along association tracts, defeats the accuracy of the method. 



Triwus has conducted experiments of a similar nature. 



Summing up the experimental evidence which has been adduced, we arrive at the 

 conclusion that, although it is difficult in the case of the lower animals to judge correctly 

 of the effects of operations on the responses made by the nervous system to auditory 

 stimuli, yet the balance of evidence is in favour of the assertion that removal of the 

 superior temporal convolutions abolishes the receptivity of auditory sensations. 



B. THE CLINICO-PATHOLOGICAL EVIDENCE. 



i 



A careful study of cases of softening, abscess and tumour affecting the temporal lobe, 

 is gradually enabling us to draw a close line round the area dominating the function of 

 hearing in the human brain ; and such cases have also shown us that lesions affecting 

 the temporal lobe may give rise, not only to complete deafness, but to groups of symptoms 

 of an extremely complex nature of which word-deafness (word-blindness), psychic deafness, 

 and amusia are examples. Analysing the published accounts of such cases for the purpose 

 of seeing how far they assist us in arriving at the exact topographical distribution of the 

 auditory function, we will first review the instances of total deafness. 



