VITAL METAMORPHOSES. 153 



the products formed by the action of acids on choleic 

 acid does not entitle us to draw any conclusion as to 

 the form in which its elements are united together. 



62. If the problem to be solved by organic chemistry 

 be this, namely, to explain the changes which the food 

 undergoes in the animal body ; then it is the business 

 of this science to ascertain what elements must be 

 added, what elements must be separated, in order to 

 effect, or, in general, to render possible, the conversion 

 of a given compound into a second or a third ; but we 

 cannot expect from it the synthetic proof of the accuracy 

 of the views entertained, because every thing in the 

 organism goes on under the influence of the vital force, 

 an immaterial agency, which the chemist cannot employ 



at will. 



The study of the phenomena which accompany the 

 metamorphoses of the food in the organism, the dis- 

 covery of the share which the atmosphere or the ele- 

 ments of water take in these changes, lead at once to 

 the conditions which must be united in order to the 

 production of a secretion or of an organized part. 



63. The presence of free muriatic acid in the stom- 

 ach, and that of soda in- the blood, prove beyond all 

 doubt the necessity of common salt for the organic pro- 

 cesses ; but the quantities of soda required by animals 

 of different classes, to support the vital processes, are 

 singularly unequal. 



If we suppose, that a given amount of blood, con- 

 sidered as a compound of soda, passes, in the body of 

 a carnivorous animal, in consequence of the change of 



