12 THE VITAL FUNCTIONS. 



wanted in different parts of the economy, are 

 required to be formed by a peculiar set of organs, 

 of which the intimate structure eludes observa- 

 tion ; although we may perceive that in many 

 instances, among the higher orders of beings, a 

 special apparatus of vessels, sometimes spread 

 over the surface of a membrane, at other times 

 collected into distinct masses, is provided for 

 that purpose. These specific organs are termed 

 glands; and the office performed by them, as 

 well as by the simpler forms of structure above 

 mentioned, is termed Secretion. 



Fifthly, similar processes of secretion are also 

 employed to carry off from the blood such animal 

 .products as may have been formed or introduced 

 into it, and may possess, or have acquired noxious 

 properties. The elimination of these materials, 

 which is the office of the excretoiies, constitutes 

 the function of Excretion. 



Sixthly, changes may take place in various 

 parts of the body, both solid and fluid, rendering 

 them unfit to remain in their present situation ; 

 and measures are taken for the removal of 

 these useless or noxious materials, by transferring 

 them to the general mass of circulating blood, 

 so as either to be again usefully employed, 

 or altogether discarded by excretion from the 

 system. This object is accomplished by a 

 peculiar set of vessels; and the function they 

 perform is termed Absorption. 



