CHAP, ii.] THE BRAIN. 1089 



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 pheno- 

 mena 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 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 temporal convolution, the 

 lesion has usually invaded other parts as well, and the deafness 

 has been associated with other symptoms, 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 sensations are felt, it may be even as 

 usual, the perception or psychical 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 

 animals, on the one hand destruction of the part of the cortex 

 probably 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 ( 618) 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 

 later bodies bearing towards hearing a relation somewhat like 

 that borne towards sight by the anterior 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. 



69: 



