428 THE SKIN. 



with external objects ; but, like tlie rest of the surface of 

 the skin, are covered by one or more layers of epithelium, 

 forming the cuticle or epidermis. The papillae adhere 

 very intimately to the cuticle, which is thickest in the 

 spaces between them, but tolerably level on its outer 

 surface : hence, when stripped off from the cutis, as after 

 maceration, its internal surface presents a series of pits 

 and elevations corresponding to the papillae and their 

 interspaces, of which it thus forms a kind of mould. 

 Besides affording by its impermeability a check to undue 

 evaporation from the skin, and providing the sensitive 

 cutis with a protecting investment, the cuticle is of service 

 in relation to the sense of touch. For, by being thickest 

 in the spaces between the papillae, and only thinly spread 

 over the summits of these processes, it may serve to sub- 

 divide the sentient surface of the skin into a number of 

 isolated points, each of which is capable of receiving a 

 distinct impression from an external body. By covering 

 the papillae it renders the sensation produced by external 

 bodies more obtuse, and in this manner also is subservient 

 to touch : for unless the very sensitive papillae were thus 

 defended, the contact of substances would give rise to 

 pain, instead of the ordinary impressions of touch. This 

 is shown in the extreme sensitiveness and loss of tactile 

 power in a part of the skin when deprived of its epidermis. 

 If the cuticle is very thick, however, as on the heel, touch 

 becomes imperfect, or is lost, through the inability of the 

 tactile papillae to receive impressions through the dense 

 and horny layer covering them. 



Sudoriparous Glands. In the middle of each of the 

 transverse furrows between the papillae, and irregularly 

 scattered between the bases of the papillae in those parts 

 of the surface of the body in which there are no furrows 

 between them, are the orifices of ducts of the sudoriparous 

 or sweat glands, by which it is probable that a large portion 

 of the aqueous and gaseous materials excreted by the skin 



