270 THE SENSORIAL FUNCTIONS. 



nally 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 the proofs of design in the adaptation 

 of organs to their respective purposes multiply upon us in 

 such profusion, as we study in detail each department of the 

 animal economy, that we are apt to overlook individual in- 

 stances, unless they are particularly brought before our no- 

 tice. How often have we witnessed and profited by the 

 rapid renewal of the cuticle, when by any accident it has 

 been destroyed, without adverting to the nature of the pro- 

 cess which it implies; or reflected that the vessels of the 

 skin 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 deposite 

 them in the precise situations in which they are wanted ! 



Different animals present remarkable differences in the 

 thickness and texture of the cuticle, according to the element 

 they are destined to inhabit, and the situations in w T hich 

 they are most frequently placed. Provision is in many 

 cases made for preserving 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 ex- 

 posure to a very dry atmosphere; and the constant action of 

 water, on the contrary, renders it too soft and spongy. In 

 order to guard against both these effects, 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 employed 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 sense of 

 touch depends are, first, an abundant provision of soft pa- 

 pillae supplied with numerous nerves; secondly, a certain 

 degree of fineness in the cuticle; thirdly, a soft cushion of 

 cellular substance beneath the skin; fourthly, a hard resist- 

 ing basis, such as that which is provided in the nails of the 



