178 ACTION OF NITROGENIZED PRODUCTS. 



very minute doses, is as unreasonable as it would be to 

 judge of the sharpness of a razor by its weight. 



93. It would serve no purpose to give these con- 

 siderations a greater extension at present. However 

 hypothetical they may appear, they only deserve atten- 

 tion in so far as they point out the way which chemistry 

 pursues, and which she ought not to quit, if she would 

 really be of service to physiology and pathology. The 

 combinations of the chemist relate to the change of 

 matter, forwards and backwards, to the conversion of 

 food into the various tissues and secretions, and to their 

 metamorphosis into lifeless compounds ; his investigations 

 ought to tell us what has taken place and what can take 

 place in the body. It is singular that we find medicinal 

 agencies all dependent on certain matters, which differ 

 in composition ; and if, by the introduction of a sub- 

 stance, certain abnormal conditions are rendered normal, 

 it will be impossible to reject the opinion, that this phe- 

 nomenon depends on a change in the composition of the 

 constituents of the diseased organism, a change in which 

 the elements of the remedy take a share ; a share simi- 

 lar to that which the vegetable elements of food have 

 taken in the formation of fat, of membranes, of the 

 saliva, of the seminal fluid, &c. Their carbon, hydro- 

 gen, or nitrogen, or whatever else belongs to their com- 

 position, are derived from the vegetable organism ; and, 

 after all, the action and effects of quinine, morphia, 

 and the vegetable poisons in general, are no hypotheses. 



94. Thus, as we may say, in a certain sense, of 

 caffeine, or theine and asparagine, &c., as well as of 



