CHAP, ii.] THE BRAIN. 799 



tion of the skin exceeds a certain limit of intensity, the sense 

 of louch or temperature is lost in, that is to say, is not appreci- 

 ated as separate from the sense of pain ; and under abnormal 

 circumstances acute sensations pf pain are started by changes 

 in parts, for example tendons, the condition of which under 

 normal circumstances we are not conscious of appreciating 

 through any distinct sensations, though it may be that these 

 parts do normally give rise to feeble impulses contributing to 

 4 general sensibility.' It may be debated whether * pain ' is a 

 phase of all sensations, or of general sensibility alone, or a sen- 

 sation sui generis. We shall have something further to say on 

 this matter when we treat of the senses ; meanwhile it will be 

 convenient for present purposes if we consider that the sensa- 

 tions we have to deal with just now are the sensations of touch 

 and of temperature, those of the muscular sense, and those of 

 general sensibility including those of pain. 



505. The fairly convincing evidence that the occipital 

 cortex has special relations with vision, and the less clear evi- 

 dence that other regions have special relations with smell and 

 healing, suggest that special parts of the cortex have special 

 relations with the sensations now under consideration. But in 

 the cases of the senses of sight and smell we had a distinct ana- 

 tomical leading ; and we have seen how uncertain is the evidence 

 where such an anatomical leading fails or is deficient, as in 

 healing and taste. In the case of sensations of the body at 

 large, the anatomical leading similarly fails us. Moreover, if 

 our judgment concerning the visual sensations of animals oper- 

 ated on is difficult, how much more difficult must be our judg- 

 ment concerning their sensations of touch and temperature, and 

 even of pain ? N 



As we have already urged ( 488, 489) observations made 

 on man himself whether in the cases where it has been possible 

 to stimulate the cortex by an electric current, or in respect to 

 the phenomena of disease, such as the aura of epileptic attacks 

 arid the like, shew most distinctly that the so-called motor region 

 of the cortex is closely associated with sensations, and that par- 

 ticular areas of this region are especially associated with sensa- 

 tions originating in particular parts of the body. We have 

 also seen that experiments on monkeys confirm this view ; the 

 removal of a motor area, that for instance of the hand, entails 

 not only loss of movement in the hand, but also loss or impair- 

 ment of sensation in the hand, lasting as long at least as the 

 loss or impairment of the movements ; moreover, so far as can 

 be learnt, all sensations are affected by the removal of the cortex, 

 those of pressure and temperature as well as those of the muscu- 

 lar sense and of pain. Similar results have also been obtained in 

 the dog. So that the evidence seems convincing that the parietal 

 region of the cortex, while it has special connections with volun- 



