102 PHILOSOPHY OF ZOOLOGY. 



peculiar secretions, and the purposes which these serve in 

 the animal economy. One class of these secretions performs 

 the office of lubricating the skin ; another of regulating the 

 temperature of the body ; and a third of carrying off the 

 superfluous carbon. 



As the skin forms the external covering of the body, it is 

 therefore exposed to the decomposing influence of the at- 

 mosphere or the waters. Were no remedy provided, its 

 texture would soon be destroyed; by desiccation in the 

 one case, and maceration in the other. But, for the pre- 

 vention of these effects, the skin is liberally supplied with 

 vessels, which secrete upon its surface, fluids,' varying in 

 their nature, according to the wasting agents which act 

 upon it. They may, however, be divided into two kinds ; 

 the unctuous and the viscous ; on the nature of which, we 

 shall offer a few observations. 



1. Unctuous Secretions. These are confined to animals 

 which have warm blood and the cells of the cellular web 

 filled with fat, as mammalia and birds. 



An oily matter is secreted from the whole skin of mam- 

 malia, in a manner not very satisfactorily determined. It 

 coats, likewise, the hairs, and serves to prevent the air from 

 drying these parts too much, or the water from wetting them. 

 It keeps the skin of the whale so soft and smooth as to ap- 

 pear like oiled silk ; and the seal, and other aquatic mam- 

 malia, emerge from the water with their fur as dry as if 

 they had been executing their movements on land. 



In some cases, the glands which secrete an unctuous 

 matter, are numerous in particular places, and their open- 

 ings become obvious to the eye, as in the human nose, and 

 below the under lip, from which the greasy matter may be 

 squeezed, like little worms. These glands are likewise nu- 

 merous in the arm-pits; and, in many quadrupeds, they 

 occur in little ha-s nenr the anus. In bird- they unite, 



