CHAPTER XII 

 URINE 



Constitution of Urine 



Total Quantity. — ^The average quantity passed by adults 

 in twenty-four hours is 1500 c.c. Of this the greater part 

 is secreted during the day. 



Physical Characteristics. — Urine has a clear yellow colour, 

 except after heavy meals, when it may be turbid, due to 

 calcium phosphate and carbonate. On standing, these 

 salts form a precipitate which redissolves on heating. 

 The average specific gravity is 1018, but it varies between 

 1002 and 1040, according to the volume of urine passed. 



Reaction. — Urine is normally acid to htmus. Its acidity 

 is greatest after a meat diet, owing to formation of sulphuric 

 and phosphoric acids. On a vegetable diet and during 

 secretion of the acid gastric juice it becomes alkahne. 

 The variabihty in the reaction of the urine is one of the 

 means whereby the reaction of the blood is kept constant. 

 \Yhen for any reason the Ph of the blood decreases {i. e. 

 the blood becomes more acid), the normal reaction is 

 restored partly by excretion of acid sodium phosphate. 



Urinary Pigments. 

 Urochrome. 

 Uroerythrine. 



Urobilinogen — derived from bile pigment. On stand- 

 ing it is converted into urobihn. 



Inorganic Constituents. 



Metals. — Sodium, potassium and traces of Ca, Mg 



and Fe. 



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