86 



THE KIDNEYS, BY C. LUDWIG. 



remains narrowed is not in all instances the same. It fre- 

 quently preserves its smaller diameter throughout the descend- * 

 ing limb of the loop, but just as often assumes a wider diameter 



Fig. 139. 



JQfl 



Fig. 139. Diagrammatic representation of the course of a urinary 

 tubule from the human kidney, p, Papillary layer or region ; g, mar- 

 ginal layer of the medulla ; r, cortex ; i, capsule of the glomerulus, 

 which is continuous by its neck with the tortuous portion of the canal (n). 

 This becomes attenuated at the contiguous borders of the medullary 

 and cortical portions of the kidney, and forms the descending limb of 

 the loop (in), then constitutes Henle's loop (/i), and continues as the 

 ascending limb of the loop (iv). This passes into the intermediary 

 portion (v), which, by an externally convex arch, enters the apex of 

 the collecting tubule (vi). This last unites with others in the same 

 medullary ray (vn) to form a principal tubule (vm), and this last with 

 other tubules to form a papillary duct (ix). 



