250 



STUDIES IN PHYSIOLOGY 



u'ri-na-ry bladder, whence it is discharged from the body 

 through a tube called the u-re'thra. 



Importance of the Kidneys. The kidneys are organs of 

 first importance in ridding the blood of its wastes. If they 

 stop work altogether, death occurs in twenty-four to forty- 

 eight hours. Fortunately 

 3 M 



vf at 



the skin can help to a 

 certain extent by excret- 

 ing an abnormal amount 

 of urea and salts. Under 

 ordinary conditions about 

 three pints of urine 

 should be given off by 

 the kidneys of an adult 

 in twenty-four hours. 

 This amount is lessened 

 if perspiration is exten- 

 sive. 



Blood Supply of the 

 Kidneys. As we might 

 expect from the impor- 

 tance of their function, 

 these organs have a gen- 

 erous supply of blood. 

 A large branch from the 

 abdominal aorta (re'nal 

 artery) enters the hilum 

 of each kidney, divides 



into smaller branches, and these finally reach the parts of 

 the tubule where the wastes are removed. The veins that 

 collect the blood from the two kidneys (renal veins) empty 

 into the inferior vena cava. The blood in these two veins 

 (as already stated on p. 148) is probably the purest in the 

 body; it comes to the kidneys almost immediately after 

 giving up its carbon dioxid in the lungs ; and before leaving 

 these excretory organs it loses its waste urea, salts, and water. 



FIG. 114. Diagram of the Circulation in 

 the Kidney. 



ai = small artery giving off a branch. 

 6 = parts of cortex supplied with spher- 

 ical swellings (glomeruli). 

 gl = spherical swellings (glomeruli) from 



which arises a twisted tubule. 

 va = branch of artery to spherical swell- 

 ing. 



ve = vein from spherical swelling. 

 v = veins from tubules. 



