762 



THE CEREBRAL CORTEX. 



that not only the whole cortical area of the temporal lobe, but probably 

 also the cornu ammonis, forms an integral portion of the auditory 

 sphere." With bilateral extirpation (in dogs) " at first the auditory 

 troubles may amount to absolute deafness, but soon pass into a condition 

 of obtuseness of hearing." In five monkeys the superior temporal gyrus 

 was destroyed or removed on both sides by Sanger Brown and myself, 

 and in one both temporal lobes were completely removed. In the last 

 case there was produced for a time a condition of idiocy, due probably 

 to the extent of the lesion, but in none of the cases was hearing 

 abolished ; whether it was impaired it is quite impossible to say, since 

 even normal monkeys will frequently take no notice of noises. 1 At any 

 rate these experiments, as well as those of Luciani, afford conclusive 



evidence that in animals the 

 function of auditory percep- 

 tion is not entirely confined 

 to the temporal lobe, although 

 it has not been experiment- 

 ally determined into what 

 other portions of the cortex 

 it extends. That its focal 

 point is to be found in the 

 superior temporal gyrus, arid 

 especially the upper part of 

 that gyrus and the gyrus 

 transversus anterior (which is 

 concealed within the fissure 

 of Sylvius, and is very early 

 in making its appearance in 

 man, Heschl), is probable, 

 partly from the result of 

 electrical excitation and 

 partly from the observations 

 of Flechsig (see below) on 

 the time of myelination of 

 the fibres ; and also as the 

 result of clinical and patho- 

 logical evidence in man; in 

 whom cerebral lesions pro- 

 ductive of disturbances of 

 auditory perception are gen- 

 erally found closely associ- 

 ated with the neighbourhood of the superior temporal gyrus. 2 



It has been shown by v. Monakow 3 that the cortex of the temporal lobe, and 

 especially of the first gyrus, is directly united with the mesial geniculate body, 

 which again is connected directly with the inferior corpus quadrigeminuin, and 



1 Since the publication of our experiments, Ferrier has given an account of a monkey on 

 which he had performed the same operation, namely, removal of the superior temporal gyrus 

 on both sides. Although he found that for a few days it appeared to take no notice of 

 sounds, yet after a time (two or three weeks) it showed recovery of the sense of hearing, 

 and even showed appreciation of the meaning of certain sounds, which it responded to by 

 characteristic cries. It is therefore impossible to suppose that audition is localised to this 

 gyrus in monkeys. 



2 Ferrier, " Croonian Lectures," 1890, p. 80. 



3 Arch.f. Psychiat., Berlin, Bd. xxvii. S. 428. 



Flu. 348. Diagrams of brain of a monkey, show- 

 ing complete removal of the superior temporal 

 gyrus on both sides. Even when this was effected 

 the animal retained a delicate sense of hearing. 



