340 THE SENSORIAL FUNCTIONS. 



it is little liable to change, and is thus, in both 

 respects, admirably calculated to afford protection 

 to the finely organized corium. 



Although the cuticle exhibits no traces of vascu- 

 larity, it is by no means to be regarded as a dead 

 or inorganic substance, like the shells of the mol- 

 lusca. 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, under- 

 going decay and renovation ; its external surface 

 drying off in minute scales, and in some animals 

 peeling off in large portions. When any part of 

 the human skin is scraped with a knife, a grey dust 

 is detached from it, which is found to consist 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 thickness in 

 the parts designed by nature to suffer considerable 

 pressure, is not entirely the effect of education ; for 

 the cuticle, 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 originally adjusting 

 the structures of parts to the circumstances in 

 which they are to be placed at an after period, 

 would of itself, were it a solitary instance, be well 

 fitted to call forth our admiration. But as we 

 study each department of the animal economy in 

 detail, the proofs of design in the adaptation of 



