CHAP. IL] THE BRAIN. 1091 



abnormal circumstances acute sensations of 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 ' general 

 sensibility.' It may therefore be debated whether 'pain' is a 

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

 sensation 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 sensations 

 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. 



679. The fairly convincing evidence that the occipital 

 cortex has special relations with vision, and the less clear evidence 

 that other regions have special relations with smell and hearing, 

 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 anatomical leading ; 

 and we have seen how uncertain is the evidence where such an 

 anatomical leading fails, as in hearing and taste. In the case of 

 sensations of the body at large, the anatomical leading similarly 

 fails. Moreover any attempt to push the analogy of sight raises 

 the following question. If there were two optic nerves on each 

 side of the head, would there be two cortical areas, one for each 

 nerve, in each hemisphere, or one visual area only ? And again, 

 if the optic nerve were the instrument for some sense in addition 

 to that of sight, would there be two cortical areas, one for each 

 sensation, or one area only serving as the cortical station so to 

 speak of the whole nerve ? If we push the analogy of sight it 

 is open for us, since we cannot give a definite answer to the above 

 question, to suppose either that there is one area for touch, 

 another area for temperature, and so on, each for the whole body, 

 or that there is an area for sensations of all kinds for each afferent 

 nerve, or, that there is an intricate arrangement which supplies 

 all the combinations of the two which are required for the life of 

 the individual. Of the three hypotheses the latter is the more 

 probable ; but if so, it is by its very nature almost insusceptible 

 of experimental proof, especially when we bear in mind what we 

 have already said touching the difficulty of judging the sensa- 

 tions of animals. If the judgment of visual sensations is difficult, 

 how much more difficult must be the judgment of sensations of 

 touch and temperature ? Indeed, sensations of pain are the only 

 sensations of which we can form a quantitative judgment in 

 animals; and our method of judging even these, namely, by 

 studying the movements or other effects indirectly produced, 

 is a most imperfect one. 



We can learn therefore almost absolutely nothing in this 



