22 CONDITIONS ESSENTIAL TO NUTRITION. 



The peculiar object of organic chemistry * is to 

 discover the chemical conditions essential to the life 

 and perfect development of animals and vegetables, 

 and generally to investigate all those processes of 

 organic nature which are due to the operation of 

 chemical laws. Now, the continued existence of all 

 living beings is dependent on the reception by them 

 of certain substances, which are applied to the nu- 

 trition of their frame. An inquiry, therefore, into 

 the conditions on which the life and growth of living 

 beings depend, involves the study of those substan- 

 ces which serve them as nutriment, as well as the 

 investigation of the sources whence these substances 

 are derived, and the changes which they undergo in 

 the process of assimilation. 



A beautiful connexion subsists between the or- 

 ganic and inorganic kingdoms of nature. Inorganic 

 matter affords food to plants, and they, on the other 

 hand, yield the means of subsistence to animals. 

 The conditions necessary for animal and vegetable 

 nutrition are essentially different. An animal re- 

 quires for its development, and for the sustenance 

 of its vital functions, a certain class of substances 

 which can only be generated by organic beings pos- 

 sessed of life. Although many animals are entirely 

 carnivorous, yet their primary nutriment must be 

 derived from plants ; for the animals upon which 

 they subsist receive their nourishment from vegeta- 

 ble matter. But plants find new nutritive material 

 only in inorganic substances. Hence one great end 

 of vegetable life is to generate matter adapted for 

 the nutrition of animals out of inorganic substances, 

 which are not fitted for this purpose. Now the pur- 



* Every vegetable and animal constitutes a machine of greater or 

 less complexity, composed of a variety of parts dependent on each 

 other, and acting all of them to produce a certain end. Vegetables and 

 animals, on this account, are called organized beings ; and the chemi- 

 cal history of those compounds which are of animal or vegetable origin, 

 or of organic substances, is called organic chemistry. See Thomson's 

 Chemistry of Organic Bodies, and Webster's Manual of Chemistry, 3d 

 edit., p. 362. 



