1058 ON CUTANEOUS SENSATIONS. [BOOK in. 



cold and heat in regions of the skin, not only free from touch 

 corpuscles but also free from any dermic terminal organs as yet 

 known, the " points " of the skin determined experimentally to 

 be points of cold and heat sensations, having been repeatedly 

 found when extirpated to be free from all such dermic organs, 

 we may, though with less certainty, still further infer that the 

 material exists somewhere in the epidermis. We may add that 

 sensations of temperature may be felt in the cornea, from which 

 all dermic terminal organs seem certainly to be absent. And 

 our knowledge that the nerve fibres end as fine fibrillse between 

 and among the cells of the Malpighian layer brings us to the 

 final conclusion that the material of which we are speaking is 

 to be sought for either in the fine nerve fibrillse themselves, or, 

 as seems more likely, in some or other of the cells of the Mal- 

 pighian layer specially connected with those fibrillae. 



Beyond this we cannot go ; and even admitting thus much, 

 it is difficult to understand how, if the change be one from a 

 higher to a lower temperature, the lower temperature, Avhatever 

 may have been the exact degree of the higher temperature, 

 should in giving rise to sensations of cold affect one set of fibres 

 only, or how the higher temperature should similarly affect 

 another set of fibres only ; but we must leave the matter here. 



The considerations which have just been brought forward in 

 relation to sensations of heat and cold, may also be applied to 

 sensations of pressure ; with regard to them also we are driven 

 to the conclusion that they take origin in the lower layer of the 

 epidermis through some condition brought about by the pres- 

 sure. We can appreciate pressure by the cornea, from which 

 as we have said dermic organs are absent. If the 4 points of 

 skin ' in various parts of the body, determined experimentally 

 to be points of pressure sensation, be extirpated and examined 

 it is found that dermic organs are not necessarily present; 

 indeed such points of pressure sensations do not differ essen- 

 tially in structure from points of heat or cold sensations, though 

 some slight difference in the manner of distribution of the 

 dermic nerve filaments has been described. 



We are thus brought to the conclusion that the so-called 

 touch corpuscles are in no way essential to touch. At the same 

 time their remarkable prominence in those parts of the skin in 

 which touch is most sensitive would seem to shew that, even if 

 not necessary, they are in some way adjuvant to pressure sensa- 

 tions. But what that aid may be is at present a mere matter 

 of speculation ; and we are perhaps still more in the dark as to 

 functions of the end-bulbs and of the Pacinian bodies. 



