78 SECRETION. 



tion and less after vegetable food. Herbivora have alkaline urine, 

 while carnivora have strongly acid urine ; but the herbivorous ani- 

 mal during fasting has acid urine, because it is then living from its 

 own tissues and is for the time a carnivore. After excretion, how- 

 ever, the urine soon becomes more acid (probably because of the 

 presence of some fermentation), and at this time uric acid and 

 urates may precipitate. Upon further exposure it is attacked by 

 micro-organisms, and the urea is changed to ammonium carbonate, 

 the reaction becoming alkaline, and there is a precipitation of triple 

 phosphates and alkaline urates. In the body these conditions do 

 not occur in conditions of health. 



What is the chemical composition of urine ? 



The urine is an excrementitious fluid, and may be considered as 

 a watery solution of the excrementitious products of the retrograde 

 metamorphosis of nitrogenous bodies, resulting from the processes 

 of life and action. Chemically, it is a solution of urea and urates 

 with a small percentage of organic salts. 



Table of the Chemical Composition of the Urine. 



Water 967 



Solids, crystallizable nitrogenous bodies : 



Urea 14 



Uric acid, free (trace), 

 Uric acid in form of alkaline urates, 



Hippuric acid and hippurates, \- . 11 



Pigments, extractives, and mucus. 

 All in small and constant amounts. 

 Salts : 



Inorganic 



Chlorides of sodium and potassium, 

 Sulphates and phosphates of sodium and potas- 

 sium, 



Phosphates of magnesium and calcium, 



Silicates (trace), 

 Organic 



Lactates, acetates, and formates, which only 



appear occasionally, 

 Sugar (occasionally), a trace, 

 Gases, nitrogen, and carbonic acid. 



1000 



8 



