WASTES GIVEN OFF BY THE BLOOD 



413 



artery vein. 





capillaries, which, in turn, unite to form a small vein as they 

 leave the little sac. Each of these sacs contains a number of 

 blood vessels, the glomerulus 

 (glSmer 'dolus). 



Wastes given off by the 

 blood in the kidney. In the 

 glomeruli the blood loses by 

 osmosis, through the very thin 

 walls of the capillaries, first, a 

 considerable amount of water 

 (amounting to nearly three 

 pints daily) ; second, a nitrog- 

 enous waste material known 

 as urea; third, salts and other 

 waste organic substances. 

 These waste products pass 



topalvif 

 of kidn^ 



Each kidney is composed of a large number 



mtO tne pelVIS 01 tne Kidney of long tubules. The blood flows through the 



flnH thrrmo-h Hiif»t<? nrptpr* glomeruli (mass of blood capillaries) and then 



ana tnrOUgU aUCIS, Ureters, through the capiUaries surrounding the tubules, 



into the bladder. Wastes from the blood pass through the walls 



_,. . . of the blood-vessels (glomeruli) into the tubules, 



The Waste products from which lead to the bladder. 



the kidney, together with the 



water containing them, are known as urine. Urine normally con- 

 sists of about 96 per cent water and 4 per cent dissolved solids. 

 The total amount of nitrogenous waste leaving the body each day, 

 by means of the kidneys, is about twenty grams. After the blood 

 has gone through the glomeruli of the kidneys it is purer than in 

 any other place in the body, because it has lost much of its nitrog- 

 enous waste in them and before going to them it gave up a large 

 part of its carbon dioxide in the lungs. So dependent is the body 

 upon the excretion of its poisonous material that in cases where 

 the kidneys do not do their work properly, death may ensue 

 within a few hours. Since the blood which passes through the 

 kidneys is being continually depleted of water, one should drink 

 plenty of water to make good this loss. 



Diet plays a very important part in the care of the kidneys. If 

 we' overbalance our diet with too much protein food, we throw 

 increased work on these organs. The nitrogen in proteins cannot 



