THE URINARY TRACT. 



763 



tion coming from the blood, if taken up by the tissues in sufficient quantity, 

 and of a certain quality, leads to the swelling up and death of the living mat- 

 ter. The exudation, originally fluid, but coagulated soon after its passage 

 from the vessels, will contain the altered or lifeless part of the tissue. The 

 result of the coagulation is the formation of hyaline or, also, of granular casts 

 in the tubules, and of granular and yellowish hyaline plugs in the blood- 

 vessels and narrow tubules. The casts are products of an albuminous exuda- 

 tion from the blood-vessels, plus the swollen up and destroyed epithelia. 

 This view is supported by the appearance of the vascular loops within the 

 tufts ; here the vascular wall is converted into a homogeneous, shining mass, 



FIG. 344. ACUTE CROUPOUS NEPHRITIS. 



D, uriuiferous tubule, with detached epithelium ; L, tubule whose epithelium is converted 

 iuto indifferent elements; T, tubule holding; a hyaline cast, which probably was washed 

 down from some other part the epithelium in part desquamated; I, interstitial tissue, 

 broadened and crowded with inflammatory corpuscles. Magnified 500 diameters. 



which is deeply stained by carmine and exactly corresponds in appearance 

 with the casts. 



Under certain circumstances the epithelium of the tubules may partially 

 or totally disappear in the mass which we term tubular cast ; but there is 

 always a rapid reproduction starting from those lumps of living matter which 

 adhere to the tubular wall. On the inner coat of the membrana propria we 

 meet with all transitions from yellowish lumps up to the formation of flat 

 epithelia covering the cast. * 



* Later observations have led to the conclusion that the flat plastids, which are spindle- 

 shaped in edge- view, are no epithelia, but the entlothelia belonging to the so-called membrana 

 propria of the tubule. With tliis view the formation of a cast is satisfactorily explained. 

 ED. 



