TOUCH. 341 



organs to their respective purposes multiply upon 

 us in such profusion, that we are apt to overlook 

 individual instances, unless they are especially 

 brought to our notice. How often have we wit- 

 nessed and profited by the rapid renewal of the 

 cuticle, when by any accident it has been de- 

 stroyed, without adverting to the nature of the pro- 

 cess which it implies; or reflected that different 

 sets of glands, with all their varied apparatus of 

 ducts, blood-vessels and absorbents must, on all 

 these occasions, supply the materials, out of which 

 the new cuticle is to be formed, must effect their 

 combination in the requisite proportions, and must 

 deposit them in the precise situations in which they 

 are wanted ! 



Different animals present remarkable differences 

 in the thickness and texture of the cuticle, accord- 

 ing to the element they are destined to inhabit, 

 and the situations in which they are most frequently 

 placed. Provision is in many cases made for pre- 

 serving the cuticle from the injury it would receive 

 from the long continued action of the air or water; 

 for it is apt to become rigid, and to peel off, from 

 exposure to a very dry atmosphere; and the con- 

 stant action of water, on the contrary, renders it too 

 soft and spongy. In order to guard against both 

 these evils, the skin has been furnished, in various 

 parts of its surface, with a secreting apparatus, 

 which pours out unctuous or mucilaginous fluids ; 

 the oily secretions being more particularly em- 

 ployed as a defence against the action of the air, 

 and the mucilaginous fluids as a protection against 

 that of water. 



The conditions on which the perfection of the 



