Vl] EX-JUT! IH< iital Kr'nli in-f n-f/tirt/ftt;/ Function 161 



A. THE EXPERIMENTAL EVIDENCE. 



On reviewing the experimental researches aiming at the exact localisation of the auditory 

 function one is tin-ceil to the conclusion that information which has been gained in this 

 manner is not wholly reliable: for while some observers have stated with full confidence 

 that certain operative procedures are followed by definite phenomena, others claiming to 

 have performed identical operations have stated with an equal degree of assurance that the 

 results are entirely negative: and in the face of so much that is contradictory and discrepant, 

 it is not to be wondered at that the results of experiments dealing with the auditory sense 

 in the lower animals are viewed with suspicion. 



Munk is again to be credited with the first positive experimental results. Bilateral 

 extirpation of the temporal lobes in his dogs was followed by complete "cortical deafness." 

 and at the same time the functions of taste, smell, and sight were preserved intact. 

 Furthermore, removal of a circular piece 1'2 cm. in diameter from the middle of his primary 

 area produced changes which Munk called "mind-deafness" (Seelentaubheit); in this con- 

 dition the hearing of the animal was intact, but it was unable to put an interpretation 

 on special sounds which it heard: for instance, it was irresponsive to calls from its master, 

 and in other ways gave evidence of this particular form of deafness; but the change was 

 not permanent, passing off in about five weeks' time. 



Luciam and Tamburini, Seppilli, and Goltz's recorded experiments agree approximately 

 with those of Munk. 



Ferrier produced strong evidence to the effect that the centre for auditory perception 

 is situated in the superior temporal gyrus, for in the case of the monkey not only did 

 electrical irritation of the superior temporal gyrus cause sudden movements of the ear, 

 head, and eyes, such as are indicative of perception of sound in the opposite ear, but 

 destruction of this gyrus on both sides caused total deafness. 



Unfortunately the operations which in the hands of Ferrier yielded such positive results, 

 proved negative when repeated by Schafer. Schafer experimented on no less than six 

 monkeys, more or less completely destroying the superior temporal gyrus on both sides, 

 and yet in not a single instance was hearing permanently affected. 



Now discrepant results like those just mentioned are extremely difficult to understand. 

 To my mind the only way of explaining Professor Schafer's negative results is by sup- 

 posing that his ablation of the superior temporal gyrus was not quite so complete as he 

 imagined and that he left behind part of the transverse temporal gyri of Heschl. In 

 regard to these gyri, I have already indicated that in the cases of the human being and 

 the anthropoid ape they possess a special structure, and that they are the parts which 

 the auditory fibres first strike on their way outwards, and I shall have occasion to mention 

 presently that they probably stand in relation to the auditory function in the same way 

 as the calcarine region does to the visual, and are accordingly of prime importance as a 

 centre for the primary reception of auditory stimuli. Reasoning by analogy, it is extremely 

 probable that these transverse gyri are represented in the lower forms of apes upon which 

 Schafer operated, and if their anatomical disposition is anything like that seen in the 

 anthropoid species one can readily imagine how difficult it would be to include them in 

 an extirpation of the first temporal gyrus : for apart from the truth that they lie deeply, 



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