XXVIII.] 



KIDNEY. 



305 



tubule, which in turn is continued into the spiral tubule. After 

 this it narrows suddenly and runs into the medulla as the descend- 

 ing tubule of Henle, where it forms a narrow loop loop of Henle 

 and passes in the reverse direction towards the cortex as the ascend- 

 ing tubule of Henle. In the cortex it has a zigzag course irregular 

 tubule and again becomes wider and convoluted second or distal 

 convoluted tubule which leads into a straight tube junctional 

 tubule which joins a straight or collecting tubule. This passes 



Tabular View (after Schdfer) of tie Parts, Situation and Epithelium 

 of a Uriniferous Tubule. 



straight through the cortex and medulla, receiving other similar 

 tubes as it goes; and becoming wider, it opens as a discharging 

 tubule (duct of Bellini) en the apex of a Malpighian pyramid. The 

 tubes are lined throughout by a single layer of epithelium, which, 

 however, changes its characters in the different parts of the tube. 

 The Malpighian capsule is a globular expansion (200 /*.), composed of 

 a basement membrane lined by a single layer of squamous epi- 

 thelium. In the convoluted tubules, proximal and distal, the epithe- 



U 



