Glomerulus 



Absorbing 

 capillaries 



Urinary 

 tubule 



L 



Bowman's 

 capsule 



Convoluted 

 tubule 



THE REMOVAL OF WASTES BY THE KIDNEYS 



Each tubule starts from on enlarged double-walled capsule. Blood from the artery 

 flows first through the capillaries of the glomerulus, out of which waste material dif- 

 fuses by osmosis. These fluids continue through the tubule, which is very long and 

 very much tangled. The blood continuing past the glomerulus runs through a sec- 

 ond set of capillaries, which are closely enmeshed with the tubules. At this stage 

 much of the water, sugar, and salts that had diffused into the capsule becomes re- 

 absorbed into the blood 



urine. And sometimes growth is so rapid during adolescence that the 

 albumin content rises. But if albumin is constantly present in the urine, it 

 indicates that the kidneys are in a diseased condition. 



The sugar content of the urine is temporarily increased by eating large 

 quantities of sugar. Whenever the sugar content of the blood rises above 

 180 milligrams per cubic centimeter, sugar overflows into the urine. But 

 when sugar continues to overflow from the body through the urine, a 

 diseased condition is indicated. An excess of sugar in the urine is one of 

 the symptoms of diabetes. 



Since the activities of the body are not carried on at an even rate, there 

 is sometimes a draft upon reserves — the glycogen in the liver, for example. 

 And sometimes wastes may be produced faster than they are removed by 

 the excretory organs. In extreme cases, failure of excretion may be fatal: 

 an accumulation of uric acid in the blood acts as poison. 



221 



