8J PHILOSOPHY OF ZOOLOGY. 



rent, or true skin. It lies immediately underneath the cttf 

 tide and mucous web. It is usually destitute of colour. It 

 consistsin some animals, as quadrupeds, of solid fibres, which 

 cross one another in every possible direction, and form a sub- 

 stance capable of considerable extensibility and elasticity. In 

 the cetacea, the fibres are arranged vertically, and exhibit an 

 appearance not unlike a section of the sessile boleti. In 

 fishes, it is more uniform in its texture; and in some cases 

 appears a homogeneous gelatinous membrane. It is more 

 obviously organized, than- the two members by which it is 

 covered. Bloodvessels and nerves penetrate its substance, 

 and may be observed forming a very delicate net-work on 

 its surface. 



The peripheral surface of this layer, is in close contact with 

 the mucous web, from which it is with difficulty detached. 

 When viewed separately, it presents numerous inequalities, 

 which give to the cuticle the appearance of angular com- 

 partments on the back of the human hand, and cur- 

 ved ridges on the palms. When this surface is more minutely 

 examined, k appears covered with numerous tubercles, va- 

 rying in shape and size according to the species or the func- 

 tions of the different parts. By macerating the corium for 

 some days in water, the structure of these tubercles may be 

 perceived. Each consists of a pencil of fibres, united at 

 their base. When the central fibres are longest, the tuber- 

 cle is conical ; when of equal lengths, the summit is flat. 



This portion of the corium has been characterised by a 

 particular name. It is called Corpus papillare, and villaus 

 surface of the skin. It is most obvious in those parts 

 which possess, in the greatest perfection, the sense of touch. 

 It is generally supposed, that the nervous filaments, con- 

 nected with that faculty, terminate in these tubercles. They 

 are depressed when not in action, but become erect on the 

 application of any stimulant- 



