402 HUMAN PHYSIOLOGY 



is excreted in organic compounds, such as glycero-phosphates ; 

 but so far these have not been fully investigated. 



IY. Chlorine-containing Bodies. 



Chloride of sodium is the chief salt of the urine. It is 

 entirely derived from the salt taken in the food, and its 

 amount varies with the amount ingested. From 10 to 15 

 grms. are usually excreted per diem in a person on normal 

 diet. 



In starvation, and still more in fever, the tissues of the 

 body have an extraordinary power of holding on to the 

 chlorine, and the chlorides may almost disappear from the 

 urine. 



Y. Bases of the Urine. 



Sodium, potassium, calcium, and magnesium occur in the 

 urine in amounts varying with the amounts taken in the 

 food. Generally speaking sodium is in excess of the others, 

 but on a flesh diet and in starvation it may fall below the 

 potassium. Calcium and magnesium are present in much 

 smaller quantities. 



YI. Pigments. 



A brown hygroscopic substance, which gives no bands in 

 the spectrum, may be extracted from urine. This has been 

 termed urochrome. By reducing this, another pigment, 

 urobilin, is produced, which gives definite bands, and which 

 is frequently present in the urine. It is probably identical 

 with the hydrobilirubin which has been prepared from the 

 bile pigments, and it contains C. H. O. and N. The pigment 

 which gives the pink colour to urates has been called uro- 

 erythrin, and its chemical nature is unknown. Haemato- 

 porphyrin (see p. 198) is normally present in small traces in 

 the urine, but in certain pathological states it is increased in 

 amount, and gives a brown colour to the urine. 



YII. Nucleo-proteid. 



A mucin-like substance derived from the urinary passages 

 is always present in small amounts, and forms a cloud when 

 the urine stands. 



