THE URINARY ORGANS. 



325 



glomerulus into the hollow capsule. Between the inner wall cov- 

 ering the surface of the glomerulus (glomerular epithelium) and the 

 outer wall (Bowman's capsule) there remains a cleft-like space 

 which communicates with the lumen of the corresponding urinifer- 

 ous tubule. In the adult the glomerular epithelium is very flat, 

 with nuclei projecting slightly into the open space of the Malpig- 

 hian corpuscle. The epithelium of the outer wall is somewhat 

 higher, but still of the squamous type. The capsule of Bowman 

 communicates with the proximal convoluted tubule by means of a 

 short and narrow neck. Its epithelium passes over gradually into 



Column of Ber- 

 tini. 



Medullary --' 

 rays. 



Malpighjan 

 pyramid. 



Lobule of adi- 

 pose tissue. 



Blood-vessel. _. 



/ . - Papilla. 



Fig. 261, Median longitudinal section of adult human kidney ; nine-tenths natural 

 size. In the peripheral portion the limits between its renal lobes are no longer recogniz- 

 able. 



the cubical epithelium of the neck, which, in turn, merges into that 

 of the proximal convoluted tubule. 



The proximal convoluted portion is from 40 n to 70 /* in diameter 

 and is lined by a single layer of irregular columnar cells, the 

 boundaries of which are made out with difficulty. The structure 

 of these cells has been studied in recent years by a number of in- 

 vestigators, among whom may be mentioned Disse, whose account 



