NITROGENIZED COMPOUNDS. 169 



as a product of the vital process. On the other hand, 

 a non-azotized medicinal agent, in so far as its action 

 affects the secretions, must be capable of performing in 

 the animal body the same part as that which we have 

 ascribed, in the formation of the bile, to the non-azotized 

 elements of food. 



Thus, if we suppose that the elements of hippuric or 

 uric acids are derived from the substance of the organs 

 in which vitality resides ; that, as products of the trans- 

 formation of these organs, they lose the vital character, 

 without losing the capacity of undergoing changes under 

 the influence of the inspired oxygen, or of the appara- 

 tus of secretion ; we can hardly doubt that similar ni- 

 trogenized compounds, products of the vital process in 

 plants, when introduced into the animal body, may be 

 employed by the organism exactly in the same way as 

 the nitrogenized products of the metamorphosis of the 

 animal tissues themselves. If hippuric and uric acids, 

 or any of their elements, can take a share, for example, 

 in the formation and supply of bile, we must allow the 

 same power to other analogous nitrogenized compounds. 



We shall never, certainly, be able to discover how 

 men were led to the use of the hot infusion of the leaves 

 of a certain shrub (tea), or of a decoction of certain 

 roasted seeds (coffee). Some cause there must be, 

 which would explain how the practice has become a 

 necessary of life to whole nations. But it is surely 

 still more remarkable, that the beneficial effects of both 

 plants on the health must be ascribed to one and the 

 same substance, the presence of which in two vegeta- 

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