TOUCH. 269 



touch. This structure is particularly conspicuous on those 

 parts of the skin which are more especially appropriated to 

 this sense, such as the tips of the fingers, the tongue, and 

 the lips: in other parts of the surface, which are endowed 

 with less sensibility, the papillae are scarcely visible, even 

 with the aid of the microscope. 



The surface of the corium is exquisitely sensible to all ir- 

 ritation?, whether proceeding from the contact of foreign 

 bodies, or from the impression of atmospheric air. This ex- 

 treme sensibility of the corium would be a source of con- 

 stant torment, were it not defended by the cuticle, which 

 is unprovided with either blood vessels or nerves, and is, 

 therefore, wholly insensible. For the same reason, also, it 

 is little liable to change, and is thus, in both respects, admi- 

 rably calculated to afford protection to the finely organized 

 corium. 



Although the cuticle exhibits no traces of vascularity, 

 is by no means to be regarded as a dead or inorganic sub- 

 stance, like the shells of the mollusca. That it is still part 

 of the living system is proved by the changes it frequently 

 undergoes, both in the natural and the diseased conditions of 

 the body. It is perpetually, though slowly, undergoing de- 

 cay and renovation; its external surface drying off in mi- 

 nute scales, and in some animals peeling off in large por- 

 tions. When any part of the human skin is scraped with a 

 knife, a gray dust is detached from it, which is found to con- 

 sist of minute scales. 



By repeated friction, or pressure of any part of the skin, 

 the cuticle soon acquires an increase of thickness and of 

 hardness; this is observable in the soles of the feet, and 

 palms of the hands, and in the fingers of those who make 

 much use of them in laborious work. But this greater thick- 

 ness in the parts designed by nature to suffer considerable 

 pressure, is not entirely the effect of education; for the cuti- 

 cle, which exists before birth, is found even then to be much 

 thicker on the soles of the feet, and palms of the hands, than 

 on other parts. This example of provident care in origi- 



zed 

 ub- 



