304 On the Sense of Feeling. 



and outer sides of the members, the parts most needing its defence. In 

 some animals, however, as the badger, tapir, &c. who throw themselves on 

 their backs at the approach of an enemy, this rule is reversed, and the 

 skin of the abdomen is thicker than that of the back. 



In man, an upright animal, there is but little difierence, the skin of the 

 back being, however, a little the thickest. 



The condition of the integument of the mammalia varies very consider- 

 ably with the habitudes and locality of the animal. 



As a general rule, the integument of the male animal is rougher and 

 thicker than that of the female. 



In the mammalia the cellular or subcutaneous tissue is filled commonly 

 with fat, the consistency of which varies with the habits of the animal. 

 In the ruminating animals it is of firm consistence, and is called * tallow.' 

 In the pig it is thicker and more homogeneous, and forms ' lard.' In the 

 cetacea, or whale tribe, where it bears the name of ' blubber,' it is an ex- 

 ceedingly viscid fluid, and escapes from a cut made through the skin, with- 

 out the aid of pressure. In these animals it renders the body specifically 

 lighter than the fluid they inhabit j and, by its non-conducting power, pre- 

 serves these warm-blooded giants of the deep from severe changes of tem- 

 perature. 



There is found in some of the lower classes, in the birds for instance, a 

 structure only fully developed in the mammalia. It is an universal muscle, 

 interposed between the integument and the body, the greater part of which 

 it covers. 



It is called the ' panniculus carnosus,' or ' fleshy pannicle,' and enables 

 the animal to corrugate his skin, and set up the hairs that lie over it ; and 

 thus to free himself from dirt or insects, without the aid of his extremities, 

 of which only the tail is usually sufficiently flexible for the purpose. A 

 muscle, in its action remotely analogous to this, covers the human scalp, 

 and enables some persons to set their hair on end at pleasure. 



Although the skin, usually, is only sufficient to cover the body, it is 

 occasionally formed into pouches or appendages of considerable size. 

 Thus it forms the dewlap of the buffalo and Cape bull, and the marsupial 

 appendage of the opossum and didelphous animals. 



With a few exceptions, the skin of the mammalia is covered over with a 

 filamentous structure, oi ' pdagel a general term, including wool, fur, &c. 

 Hence the mammalia have been called 'pilifers,' and the birds and fishes 

 'pennifers' and ' squammifers.' 



The colour of the pelage is usually some modification of white, black, 

 deep brown, or yellow. These colours are usually more brilliant on the 

 most exposed parts of the body. 



The colour is often variable : the young of some animals are marked by 

 spots that disappear in the adult ; and in cold climates many animals be- 

 come white or grey during the winter. 



