THE COMPOSITION OF THE URINE 1081 



The viscosity of urine is normally 1.2 as great as that of distilled water 

 at 37° C-. While blood freezes at -0.56° C, urine freezes at -°1.0 to 

 — 2.5° C. If very dilute, the freezing point may lie at 0.075° C, and if 

 very concentrated at — 5^ C. 



The reaction of the urine of man and the carnivora is acid to litmus 

 and phenolphthalein. This is due to the fact that neutral constitu- 

 ents of the food are eventually transformed into acid end-products, the 

 sulphur of the proteins giving rise to sulphuric acid, and the phosphorus 

 of lecithin to phosphoric acid. An ingestion of large quantities of 

 vegetables and fruits, however, will make it alkaline and ttirbid, owing 

 to the precipitation of earthy phosphates. In the herbivora, the urine 

 is alkaline, because their food embraces fruits and vegetables which 

 contain salts of dibasic or polybasic acids, such as acid potassium 

 malate, citrate, acetate and tartrate. The oxidation of these bodies 

 during metabolism gives rise to carbonates. Some of the carbonic 

 acid leaves the body through the lungs, whereas their bases are excreted 

 in the urine as alkaline carbonates. For this reason, the urine of these 

 animals frothes on addition of an acid. Furthermore, if these animals 

 are starved, their urine becomes acid, because they then live upon their 

 tissues and are converted, so to speak, into carnivorous animals. This 

 is also true of man, because the withholding of fruits and vegetables 

 removes all possibility of the urine becoming alkaline. In disease, 

 it is more generally acid, this change being due in most instances to the 

 restriction of the diet. With the increase in acidity, the excretion of 

 ammonia is usually augmented. 



The composition of the urine differs somewhat with the type of 

 food ingested and the quantity of water eliminated through this channel. 

 In general, however, it may be said to contain 60 grm. of solids, of 

 which 25 grm. are in the form of inorganic and 35 grm. in the form 

 of organic substances. Thus, an adult man on a mixed diet yields 

 about 1500 c.c. of urine in a day which shows the following compo- 

 sition:^ 



Inorganic substances Organic substances 



Sodium chlorid 15.0 grams Urea 30 . grams 



Sulphuric acid 2.5 grams Uric acid 0.7 grams 



Phosphoric acid 2.5 grams Creatinine 1.0 grams 



Potassium 3.3 grams Hippuric acid 0.7 grams 



Ammonia 0.7 gram Other constituents 2.6 grams 



Magnesia 0.5 gram 



Lime 0.3 gram 



Other constituents 0.2 gram 



THE INORGANIC CONSTITUENTS OF URINE 



Chlorid s. — The inorganic or mineral constituents of urine consist 

 principally of chlorids, phosphates, sulphates and carbonates of sodium, 

 potassium, ammonium, calcium, and magnesium. The total amount 

 1 Mosenthal, Arch. Int. Med., xvi, 1915, 733. 



