520 URINE. 



3.2 per cent, of urea ; a healthy man secretes 22-36 

 grrns. of urea in twenty-four hours. 



When fresh urine is mixed with an acid, the uric 

 acid falls after a time, sometimes immediately, as a 

 brownish or reddish powder. Its amount is about 0.1 

 per cent. 



Human urine contains, further, creatine (about 0.1 

 per cent.), frequently succinic acid, traces of hippuric 

 acid and of ammonium oxalurate, occasionally xan- 

 thine and several other organic substances of undeter 

 mined nature, which are obtained as an extractive 

 mass in the analysis. 



It contains about 2 per cent, of inorganic salts, 

 potassium and sodium chlorides, potassium and sodium 

 sulphates, acid sodium phosphate, calcium and mag 

 nesium phosphates, further, a small quantity of silicic 

 acid and iron. The salts of the alkaline earths can be 

 precipitated from it by means of ammonia. 



Urine may, further, contain various foreign sub 

 stances, which are brought into the body in a soluble 

 condition, and extracted from the- blood by the kid 

 neys. A number of salts, for example, saltpetre, potas 

 sium ferrocyanide, etc., pass unchanged from the 

 stomach into the urine ; also organic acids, tartaric, 

 oxalic acids, etc. Their salts with the alkaline 

 metals, however, are decomposed during digestion, and 

 they are found in the urine in the form of alkaline 

 carbonates, imparting an alkaline reaction to the 

 urine. Further, several organic coloring principles, 

 volatile oils, resins, etc., pass unchanged into the urine, 

 imparting to it color and odor. Benzoic acid, oil of 

 bitter almonds, cinnamic acid and quinic acid, are 

 found in the urine, transformed into hippuric acid. 



In diseases the character of the urine is changed in 

 various ways. Occasionally it becomes neutral or even 

 alkaline, and is then turbid from the separation of cal 

 cium phosphate, and microscopical crystals of mag 

 nesium ammonio-phosphate, and calcium oxalate. Or 

 it becomes too concentrated, and on cooling deposits 

 ray or reddish sediments, consisting of alkaline urates. 

 n fevers this sediment is of a brick-color or rosy-red, 



