Chap. XVII] 



URINARY SYSTEM 



335 



COMPOSITION OF URINE 



The composition of urine is very complex; even in health it 

 varies, depending on the quantity and kind of food eaten, etc. 

 The chief constituents are as follows : — 



Urine 



Water, 



95 per cent 



Solids, 

 5 per cent 



Organic, 

 about 3.7 



Inorganic, 

 about 1.3 



Urea (2 per cent of total solids). 



Uric acid. 



Creatinin. 



Hippuric acid. 



Other substances. 



Sodium chloride. 



Sulphates. 



Phosphates. 



Potassium. 



Ammonimn. 



Magnesiimi. 



Calcium. 



Other substances 



, Salts of 



Urea. — Urea constitutes about one-half of the solid constitu- 

 ents of the urine, and represents the chief end product resulting 

 from the metabolism of the proteins of the food and tissues. The 

 result of the oxidation of protein material exists in the blood until 

 the blood reaches the liver. Under the action of the liver cells 

 this material (ammonium carbamate) is converted into urea and 

 remains in the circulation until the blood reaches the kidneys. 

 To eliminate urea is the special work of the kidneys, and if for any 

 reason they fail to execute their work, the accumulation of urea 

 in the system leads to a condition of poisoning. 



Normally an adult voids about one ounce (30 gm.) in twenty- 

 four hours, but the quantity is increased by a diet rich in proteins, 

 strenuous exercise, fever, and some diseases. A small amount 

 of protein food, excessive vomiting, free perspiration, and diseases 

 that interfere with elimination will decrease the amount of urea 

 voided. 



Uric acid. — Uric acid is thought to represent the end products 

 resulting from the oxidation of the tissues, and next to urea is the 

 medium by which nitrogen is eliminated from the body. Uric 

 acid combines with potassium and sodium to form urates, and is 

 found in the form of urates in the urine. In gout the excretion of 



