796 SENSATIONS OF HEARING. [Boon in. 



nary cranial nerves, and we have no anatomical guidance as to 

 the fibres of either of the above two nerves making special con- 

 nections with any part of the cortex. Though sensations of 

 taste enter largely into the life of animals, and indeed of man 

 himself, we have no satisfactory indications which will enable 

 us to connect this special sense with any part of the cortex ; the 

 view indeed has been put forward that some part of the cortex 

 in the lower portion of the temporal lobe, not far from the centre 

 for smell, serves as a centre for taste ; but the arguments in 

 favour of this view are not, as yet at least, convincing. 



Sensations of Hearing. 



503. The cochlear division of the eighth or auditory 

 nerve may be assumed to be a nerve of the special sense of hear- 

 ing, and of that alone ; the vestibular division serves, as we have 

 seen, for other functions than those of hearing, 478, but as we 

 shall urge in dealing with the senses is not to be regarded as 

 wholly useless for the purposes of that sense. The cochlear 

 division may be traced into the bulb, and the vestibular division 

 into the lateral auditory nucleus (which perhaps may be regarded 

 as a continuation or segmental repetition forwards of the cuneate 

 nucleus or of part of that nucleus), and into the cerebellum, 

 the cerebellar continuation being probably the part of the nerve 

 which serves for coordinating functions. The connections of 

 the auditory nerve with the cerebral hemisphere belong to the 

 same category as those of other afferent cranial, and we may add 

 spinal nerves ; we have no very clear anatomical guide towards 

 any particular part of the cortex. 



When we turn to the empirical results furnished by experi- 

 ment and clinical observations, we find that these, though even 

 less definite and less accordant than in the case of the senses of 

 sight and smell, point to part of the first or superior temporal 

 (temporo-sphenoidal) convolution (Figs. 123, 134, 136) lying in 

 the temporal lobe just ventral to the Sylvian fissure, as being 

 specially concerned in hearing in some such way as the occipital 

 lobe is concerned in vision. 



Electrical stimulation of this region of the cortex gives rise 

 to 'pricking of the ears,' and other movements such as are 

 frequently connected with auditory sensations; but such phe- 

 nomena are in this instance perhaps to be depended upon even 

 less than in other similar instances. While some observers 

 maintain that this convolution, the operation including other 

 portions of the temporal lobe as well, may be removed from a 

 monkey without producing any certain signs of deafness, other 

 observers have found that removal of it on one side affected the 

 hearing of the ear on the opposite side, and removal on both 



