PHYSIOLOGY. 29 



veral sensations referred to touch ; but it is not necessary to be 

 done here. 



From certain sensations referred to touch, it appears, that not 

 only the extremities (XXIX. 3.), but that every part of the 

 nervous system (XXVIII.) is sentient with respect to certain 

 impressions. 



" When mankind found that they could not generalize touch, 

 they brought it under the general notion of feeling, and thereby 

 united a great variety of sensations ; but there is no connexion 

 between the sensations, e. g. of hardness or asperity, and of cold 

 and heat ; and we cannot refer those to any one part of the body. 

 It is true, that the prominent nervous papillae are the pe- 

 culiar means of perceiving the roughness or smoothness of 

 bodies; but it is only in this respect that we can say there is an 

 organ of touch. The general sense of impulse, the action of a 

 sharp pointed body may take place upon the end of a nerve in 

 the skin, but we may also apply it to any internal part where 

 there are no papillae so modified, for it will give a sensation ap- 

 plied in any part of the course of a nerve. In short, of almost 

 all parts of the body, external or internal, there are few that are 

 not sensible to the impression of a sharp-pointed body ; it is the 

 same I think with respect to heat and cold, the organ of which 

 we can conceive to be placed in the skin no further than as it 

 is external, for if any other part is laid bare, it is also affected 

 by heat and cold. We cannot say, therefore, that touch is oc- 

 casioned by any particular qualities of bodies ; these are prodi- 

 giously diversified, so that there is no foundation for making a 

 genus under the title of touch, any farther than as it comes un- 

 der the title of feeling or perception. I say that mankind have 

 referred to the head of touch every sensation that does not ma- 

 nifestly belong to the other four. It is particularly curious to 

 observe, with regard to the other four, that while they are the 

 organs of peculiar sensations, they are also the organs of touch, 

 as in the stricter view they are organs fit for receiving mechan- 

 ical action ; as when the eye is pained, or the ear is uneasy with 

 the intensity of light or sound ; or when the nose is affected 

 with pungent odours, or the tongue with acrid tastes. I con- 

 sider these as modes of touch ; and we shall find that not only 

 a variety of sensations of impression, but, among the rest, many 



