Chap, ii.] THE BRAIN". 797 



sides brought the animal into a condition in which, without 

 being perhaps absolutely deaf, it reacted towards sound in a 

 very imperfect manner indeed, very different from its normal 

 behaviour. The scanty clinical histories bearing on this 

 matter are not very decisive ; for though deafness has been 

 observed in connection with disease affecting the superior tem- 

 poral convolution, the lesion has usually invaded other parts 

 as well, and the deafness has been associated with other symp- 

 toms, notably aphasia. An auditory 'aura' has however at 

 times been observed in connection with disease of this region, 

 as also a peculiar psychical failure, known as ' word deafness,' 

 in which, though sounds are heard, that is to say auditory sen- 

 sations are felt, it may be even as usual, the perception or psy- 

 chical appreciation of the sounds is lacking, and a spoken word 

 is not recognized. 



Lastly, we may add that, though as we said the anatomical 

 leading is not definite, observers have found that, in new-born ani- 

 mals, on the one hand destruction of the part of the cortex prob- 

 ably corresponding to the region mentioned above, leads to 

 atrophy of the median corpus geniculatum, and, to some extent, 

 of the posterior corpus quadrigeminum ; and on the other hand 

 destruction of the internal ear leads to an atrophy of part of the 

 lateral fillet of the opposite crossed side which may be traced 

 to the posterior corpus quadrigeminum, and thence to the 

 median corpus geniculatum ; and section of the lateral fillet 

 on one side leads, among other results, to atrophy of the 

 striae acusticae and tuberculum acusticum of the crossed 

 side. This suggests that the path of auditory impulses is 

 along the cochlear nerve to the lateral fillet of the crossed side, 

 and so by the posterior corpus quadrigeminum and median 

 corpus geniculatum to the cortex of the temporal lobe of that 

 crossed side, the two latter bodies bearing towards hearing a 

 relation somewhat like that borne towards sight by the ante- 

 rior corpus quadrigeminum and lateral corpus geniculatum. 

 But the matter needs farther investigation. 



There remains the special sense of touch, but this we had 

 better consider in connection with sensations in general. 



