THE URINARY TRACT. 



749 



of a new formation of epithelia after the loss of the original epithelial invest- 

 ment. (See Fig. 338.) 



It may be admissible to assume that the enlarged endothelial layer serves 

 (at least to some extent) as a substitute for the lost epithelia. In tubules 

 whose epithelia, as in chronic catarrhal nephritis, are transformed into inflam- 

 matory or medullary corpuscles, the new formation of such structures also 

 starts from the endothelia. The 

 final result in this instance is 

 known to be the destruction of the 

 tubule and its replacement by 

 newly formed connective tissue 

 a condition which is known by 

 pathologists as cirrhosis of the kid- 

 ney. 



Still more plainly marked are 

 the endothelia in croupous (paren- 

 chymatous) nephritis. In fact, the 

 appearances seen in urinary tu- 

 bules, where casts have just form- 

 ed, could not be explained, unless 

 by the presence of endothelia. We 

 do not yet know what the mass 

 composing a cast really is. This 

 much, however, is certain, that 

 casts are proteinates and forma- 

 tions of an albuminous or fibrinous 

 exudate from the blood-vessels. 

 This exudate, before it reaches the 

 central caliber of the tubule, nec- 

 essarily must saturate the inter- 

 vening epithelia, whose structure 

 is completely destroyed by this 

 process. 



It is not my purpose to dwell 

 upon the origin of casts ; but, from 

 what I have seen, I cannot concur 

 with Oedmansson * in the opinion 

 that every cast should be regarded as a product of secretion furnished by the 

 epithelium. I am sure that the epithelia perish in the formation of the cast. 

 Neither can I agree with Charcot t in the opinion that some (granular) casts 

 are made up of broken-down epithelial cells, others (hyaline and some gran- 

 ular) of an albuminous substance, while epithelial casts are agglomerations 

 of epithelial cells more or less altered. Bartels + insists that, in every case in 

 which he has examined microscopically thin sections of diseased kidneys 

 whose tubules were blocked by the dark granular casts, the tubules invariably 

 exhibited an epithelial lining, reconciling this fact with his view by admitting 

 that the theory of Key and Bayer that the epithelium thus shed is rapidly 

 reproduced maybe correct. From my observations it is obvious that the 



* Bartels, von Ziemssen's " Cyclopaedia," vol. xv., pp. 84. 



t Charcot, " Bright's Disease." Millard's translation, New- York, 1878, pages 29 et seq~ 



t Bartels, op. cit., pp. 84-86. 



FIG. 338. CONVOLUTED TUBULE FROM 

 A HUMAN KIDNEY AFFECTED WITH 

 CHRONIC CATARRHAL (DESQUAMA^- 

 TIVE) NEPHRITIS. OBLIQUE SECTION. 



C, caliber, widened by loss of the epithelia : 

 E, endothelia, increased in size and number ; F, 

 interstitial iibrous connective tissue, with aug- 

 mented plastids. Magnified 1200 diameters. 



