750 



THE URINARY TRACT. 



last three writers have regarded the endothelia, as I have described them, 

 as epithelia. 



Whenever we find a cast within a tubule, especially in transverse sections 

 of the tubule, we almost invariably see a wreath of irregularly spindle-shaped, 

 partly nucleated bodies, which I am sure are nothing but the lining endothelia 

 of the structureless membrane. Alfred Meyer * gives illustrations of these 



wreaths, which evidently are drawn 

 with the greatest accuracy; but he 

 does not realize at all their character 

 or significance, for he suggests that 

 they are constructed either of rem- 

 nants of the former epithelia, of 

 which a large portion has been de- 

 stroyed in the formation of the cast, 

 or that they may be newly formed 

 epithelia. In both these views he 

 is mistaken. The epithelia are cer- 

 tainly gone, entering, in a consider- 

 ably swollen condition, the mass of 

 the cast, and what is behind the cast 

 is not newly formed epithelia, but 

 ' merely the endothelial investment 

 of the structureless layer, consider- 

 ably increased in size. (See Fig. 

 339.) 



Not infrequently we see widened 

 urinary tubules as a rule, of the 

 convoluted variety entirely desti- 

 tute of epithelia ; or we see such tu- 

 bules containing a cast broader in 

 its diameter than the caliber of the 

 tubule would be if the epithelial 

 layer were present. The latter feat- 

 ure is explicable by the fact that 

 casts may be carried into tubules far 



FIG. 339. CONVOLUTED TUBULE FROM 

 A HUMAN KIDNEY AFFECTED WITH 

 ACUTE CROUPOUS NEPHRITIS. OB- 

 LIQUE SECTION. 



C, hyaline cast ; S, swollen and disinte- 

 grated epithelia participating in the formation 

 ol the cast ; E, wreath of endothelia ; J, inter- 

 stitial connective tissue. Magnified 1200 diam- 

 eters. 



distant from the place of their ori- 

 gin into tubules, besides, which 

 have been previously deprived of 



their epithelia. There is no cogent necessity whatever for the conclusion that 

 casts may form in tubules after these have lost their epithelia. In neither of 

 these instances shall we ever miss the endothelial investment, although this is 

 often found in a mutilated or imperfectly developed condition. 



The results of my researches may be summed up in the following state- 

 ments : 



1. The rods discovered by Heidenhain in some varieties of the tubuli uriniferi 

 are part and parcel of a reticulum present within every epithelium. 



2. The reticulum, including its elongated, rod-like formations, is the living mat- 

 ter proper. 



'' " Uutersuchungen iiber acute Nierenentzunduug." 

 *u Wien," 1877. 



'Sit/uugsb. d. Akad. d. Wissensch. 



