62 USES OF THE URINE, 



most highly nitrogenised constituent, urea, as in the 

 normal condition. (Marchaud. Erdmaun's Journal 

 fur praktische Chemie, XIV. p. 495.) 



Differences in the quantity of urea secreted in 

 these and similar experiments are explained by the 

 condition of the animal in regard to the amount 

 of the natural motions permitted. Every motion 

 increases the amount of organised tissue which 

 undergoes metamorphosis. Thus, after a walk, the 

 secretion of urine in man is invariably increased. 



The urine of the mammalia, of birds, and of 

 amphibia, contains uric acid or urea ; and the ex- 

 crements of the mollusca, and of insects, as of can- 

 tharides and of the butterfly of the silkworm, con- 

 tain urate of ammonia. This constant occurrence of 

 one or two nitrogenised compounds in the excre- 

 tions of animals, while so great a difference exists 

 in their food, clearly proves that these compounds 

 proceed from one and the same source. 



As little doubt can be entertained in regard to 

 the function of the bile in the vital process. When 

 we consider, that the acetate of potash, given in 

 enema, or simply as a bath for the feet, renders the 

 urine strongly alkaline (Rehberger in Tiedemann's 

 Zeitschrift fiir Physiologie, II. 149), and that the 

 change which the acetic acid here undergoes cannot 

 be conceived without the addition of oxygen, it is 

 obvious, that the soluble constituents of the bile, 

 prone to change in a high degree as we know them 

 to be, and which, as already stated, cannot be em- 



