10 NUTRITION AND REPRODUCTION 



mined by a force of attraction (combination), which 

 acts between the smallest particles of matter, and is 

 manifested only when these are in actual contact, or at 

 infinitely small distances. 



To this peculiar kind of attraction we may of course 

 apply different names ; but the chemist calls it affinity. 



The cause of the state of motion is to be found in a 

 series of changes, which the food undergoes in the or- 

 ganism, and these are the results of processes of de- 

 composition, to which either the food itself, or the 

 structures formed from it, or parts of organs, are sub- 

 jected. 



The distinguishing character of vegetable life is a 

 continued passage of matter from the state of motion to 

 that of static equilibrium. While a plant lives, we 

 cannot perceive any cessation in its growth ; no part of 

 an organ in the plant diminishes in size. If decompo- 

 sition occur, it is the result of assimilation. A plant 

 produces within itself no cause of motion ; no part of 

 its structure, from any influence residing in its organism, 

 loses its state of vitality, and is converted into unorgan- 

 ized, amorphous compounds ; in a word, no waste 

 occurs in vegetables. Waste, in the animal body, is a 

 change in the state or in the composition of some of 

 its parts, and consequently is the result of chemical 

 actions. 



The influence of poisons and of remedial agents on 

 the living animal body evidently shows, that the chemical 

 decompositions and combinations in the body, which 

 manifest themselves in the phenomena of vitality, may 



