PROCESSES OF NUTRITION. 11 



The functions subservient to nutrition may be 

 distinguished, according as the processes they 

 comprise relate to seven principal periods in the 

 natural order of their succession. The first 

 series of processes has for its objects the re- 

 ception of the materials from without, and their 

 preparation and gradual conversion into proper 

 nutriment, that is, into matter having the same 

 chemical properties with the substance of the 

 organs with which it is to be incorporated ; and 

 their purpose being to assimilate the food as 

 much as possible to the nature of the organic 

 body it is to nourish, all these functions have 

 been included under the term Assimilation. 



The second series of vital functions com- 

 prise those which are designed to convey the 

 nutritive fluids thus elaborated, to all the organs 

 that are to be nourished by them. In the more 

 developed systems of organization this purpose 

 is accomplished by means of canals, called vessels^ 

 through which the nutritive fluids move in a 

 kind of circuit : in this case the function is de- 

 nominated the Circulation. 



It is not enough that the nutritive juices are 

 assimilated ; another chemical process is still 

 required to perfect their animalization, and to 

 retain them in their proper chemical condition 

 for the purposes of the system. This third object 

 is accomplished by the function of Respiration. 



Fourthly, several chemical products which are 



