THE URINARY ORGANS. 



327 



surfaces of the cells constituting the epithelium of the proximal 

 convoluted portion present numerous projections which interlock 

 and give to a surface view an irregular fringe-like outline. In cross- 

 section the cells. appear to be striated from their bases upward to 

 the middle of the nucleus. Here, however, the striation is without 

 doubt due to the outlines of the irregular ridges. (Fig. 264.) 

 These structural relations have lately been confirmed in the case 

 of the guinea-pig, and also found to hold true for man (Landauer). 

 This striation is much coarser than that found in the basal portions 

 of the cells, but both are, under certain circumstances, seen together. 



Nuclei of en- 

 d o the 1 ial 

 cells of blood 

 capillaries. 



Fig. 263. Section of proximal convoluted tubules from man ; X S^o. 



The proximal convoluted portion of the uriniferous tubule, before 

 it terminates, passes over into a straighter portion, which gradu- 

 ally becomes smaller in diameter, and is situated in the medullary 

 rays. This portion of the uriniferous tubule, which is sometimes 

 designated as the spiral segment of Schachowa, or again as the end 

 segment of Argutinski, is lined by an epithelium which is similar 

 to that of the proximal convoluted portion, as above described. 

 The attenuated end of the spiral segment is continuous with the 

 descending limb of Henle's loop. 



The descending limb of Henle's loop, from g/j. to 1 5 // in diameter, 

 is narrow and possesses flattened epithelial cells, the centers of 



