THE STORY OF THE LUNGS, SKIN AND KIDNEYS 95 



the kidneys is the purest blood in the body, but of 

 course it soon mixes with the general venous stream 

 from the body at large, passing back to the lungs 

 by the vena cava (Fig. 28) for purification. There 

 is thus a perpetual flow of blood through the 

 kidney, and although it is pure blood which enters 

 by the artery, such blood nevertheless contains 



Fig. 28. THE KIDNEYS IN POSITION. 



(1 and 2) kidneys, (3) vena cava, (4) aorta, (5, 5) 



ureters leading to bladder. 



certain of those products which, resulting from 

 the breakdown in the body of the nitrogenous foods, 

 are destined to be removed from the blood 

 by the organs we are considering. The structure 

 of the kidney is somewhat of a complicated nature. 

 The essential feature of the organ consists in the 

 presence of a large number of little bodies, each 

 containing a ball or network of fine capillaries which 



