180 



ELEMENTARY PHYSIOLOGY 



LBSS. 



hack upon itself and runs up again into the cortex. The 

 loop thus formed is known as the loop of Henle,' and 

 tlic two parts of which it is formed are called the 

 descending limb and the ascending limb of the 

 loop (Fig. 54, IIL IV.). 



Reaching the cortex once more the tubule becomes 

 zigzag and then again convoluted, after which it 



Fig. 53. — Circulation in the Kidney. 



ai, small branch of renal artory reiving off the br.mch va, which enters 

 glonicniluR, issues as vc, and tlion breaks \ip into capillaries, which after 

 aurrovnidiug the tubule find their way by v into ri, branch of the renal 

 vein ; )/i, capillaries around tubules in parts of the cortical substance 

 where there are no glomeruli. 



passes into a straight part or collecting tubule, 

 which, leaving the cortex finally for the medulla and unit- 

 ing with other similar collecting tubules, forms the dis- 

 charging tubule which finally opens near the summit of 

 a pyramid (Fig. 54, V.-IX.). 



Each tubule is lined tliroughout by cells, the epithelium, 

 and the cells differ in their characters in the several 



1 Who first described it. 



