THE URINARY TRACT. 



773 



atrophied portions we find districts where a considerable amount of connect- 

 ive tissue has developed, thus constituting a true hypertrophy, or liyperplasia. 

 This tissue surrounds the tubules, which in a majority of cases are entirely 

 without epithelia. The epithelia may have been carried away by simple des- 

 quamation, or have perished in the formation of casts. In many of the narrow 

 tubules, from which the epithelia have disappeared, we find a row of narrow 

 endothelia, detached in places from the connective-tissue wall. A kidney of 

 the above description may with as much propriety be called hypertrophied 

 as a lung or a glandular organ in a like condition. (See Fig. 351.) 



Concerning the formation of casts, ray observations convince me that the 

 epithelia lining the tubule, becoming saturated with the albuminous exudate, 

 swell, grow pale, and finally produce the mass called a tubular cast. In many 

 cases the cast has the appearance of having been constructed of a number of 

 hyaline or granular lumps resembling former epithelia. Around the cast, at 



FIG. 350. ATROPHY OF KIDNEY, AFTER CROUPOUS NEPHRITIS. 



O, indistinctly fibrous connective tissue ; J, cluster of medullary corpuscles, sprung from 

 former tubular epithelia ; T, tubule, deprived of its epithelia ; If, tubule, containing a granu- 

 lar cast. Magnified 600 diameters. 



its place of origin, we almost invariably see a wreath of endothelia lying 

 between it and the wall of the tube, indicating that after the formation of the 

 cast a reproduction of endothelia had taken place, or that they had -been 

 brought into view by the liquefaction of the hyaline, so-called basement-mem- 

 brane. The presence of this endothelial wreath seems to be satisfactory 

 proof that the cast was formed in the situation where we find it. If a cast 

 is seen not quite filling the caliber of the tubule which is still lined with 

 unchanged epithelia, the most reasonable presumption is that it has been 

 transported to it * present locality from a narrower part of the uriniferous 



