THE COMPOSITION OF THE URINE 1083 



for leaving the body. The remainder exists in the urine as mono- 

 and disodium hydrogen phosphate, the amount of each varying with 

 the reaction of this medium. If neutral or alkaline, a deposit of 

 earthy phosphates results- which may immediately be cleared up by the 

 addition of acid. This condition generally arises after a copious vege- 

 table diet, when a large amount of disodium hydrogen phosphate is 

 produced. Quite similarly, an abundant ingestion of protein sub- 

 stances, gives rise to an acid urine, owing to the formation of sulphuric 

 and other acids. In the latter case, there is a greater formation of phos- 

 phoric acid and production of monosodium hydrogen phosphate. 



On standing, the urine assumes an alkaline reaction, owing to the 

 conversion of the urea by the micro-organisms into ammonium car- 

 bonate. Under these circumstances, a creamy white precipitate is 

 formed which consists of triple phosphate or ammonium-magnesium 

 phosphate, and stellar phosphate or calcium phosphate. It should be 

 remembered, however, that even normal human urine contains a 

 small quantity of ammonia, i.e., from 0.6 to 0.8 grm. in a day. 

 This amount may serve as an index of the excess of acids over bases 

 which are to be excreted. While it is possible to vary this amount arti- 

 ficially, for example, by the administration of mineral acids, any 

 increase during the normal ingestion of food invariably signifies that 

 abnormal acid substances are formed in the body. This is the case in 

 diabetes mellitus, a disease in the course of which the fatty acids 

 accumulate in consequence of their diminished oxidation. This accu- 

 mulation must necessarily lead to a rise in the ammonia content of the 

 urine. 



THE ORGANIC CONSTITUENTS OF URINE 



Urea or Carbamide. — ^The greatest amount of the organic material 

 in urine is made up of nitrogenous bodies which are derived from the 

 proteins of the food. We have seen that the substances are broken 

 up in the intestinal canal into their amino-acids which after their 

 absorption are either converted into the proteins of the tissues or are 

 diamidized. In the latter case, the principal portion of the carbon, 

 oxygen, and hydrogen is oxidized to form CO2 and water, whereas the 

 smaller portion is combined with nitrogen to form urea, ammonia, 

 uric acid, and other bodies. This same fate awaits the tissue-proteins 

 which are constantly broken down 'and replaced by new material. It 

 has also been pointed out above that by far the largest amount of the 

 nitrogen of the food is excreted in the urine, and that only a small 

 portion of it enters the feces or is lost in the sweat. Consequently, 

 the total nitrogen content of the urine gives in a fair way the total 

 amount of nitrogen ingested, because under ordinary conditions, the 

 body is in nitrogen-equilibrium and its N-ingo equals its N-outgo. 

 This relationship, however, does not hold true when the body is grow- 

 ing and needs nitrogenous material for the construction of its cells. It 

 may also be disturbed for a time for other reasons. Thus, a reduc- 



