THE URINAEY TEACT. 761 



face must pass through the walls of the vessels, through the connective tissue 

 intervening between vessels and epithelium, and finally through the epithelia 

 themselves, it is evident that every superficial exudation, before becoming 

 free, must have been an interstitial and a parenchymatous one. The fluid 

 coming from the blood, is taken up by the living epithelia, and may lead to 

 changes such as were described by E. Wagner, but also to the destruction of 

 the epithelia. After the union of the granules of living matter is broken, the 

 granules themselves are imbedded in the coagulating exudate, or are converted 

 into an albuminate no longer viable. This change may occur in the epithelia 

 as well as in the connective tissue after dissolution of the basis-substance. 

 There is nothing to hinder the supposition that with the exudate formed ele- 

 ments of the blood emigrate, and, after being entirely or partially changed, 

 lie imbedded in the now coagulated mass. It is evident that epithelia alone 

 cannot produce a croup-membrane, but require the presence of an exudate 

 from the blood, and the essential constituent of the croup-membrane, under 

 all circumstances, is the coagulable albuminoid body from the blood. 



If we apply to the renal tissue the experience gained in other mucous 

 membranes, it follows that the characteristic features of a croupous nephritis, 

 in Traube's sense, consists in the presence of casts. I mean the products 

 known as hyaline and granular casts to which epithelia from the tubules may 

 adhere. The waxy, shining casts maybe formations which have undergone sec- 

 ondary changes. These bodies were seen for the first time in 1842 by Henle, 

 and declared to befibrine. This view was shaken by Rovida,* who stated that 

 the colorless and yellow casts could neither be fibrine, nor gelatine, chondrine, 

 mucine, hyaline, or other colloid substance. Rovida admits, however, that 

 casts possess certain properties of the proteinates which permit their being 

 regarded as derivations of an albuminous substance. According to Axel Key 

 and Ottom. Bayer the casts have arisen from a degeneration of the tubular 

 epithelium and a coalescence of epithelia thus degenerated ; both investigators 

 are cognizant of the fact that in tubules which are obstructed by a cast the 

 epithelial lining is present nearly every time and remains intact for a long 

 while. It will scarcely be necessary to go into particulars regarding the secre- 

 tion theory, since after what has been said the exudation from the blood must 

 under all circumstances pass through the epithelia. 



C. Bartels t declares that clinical experience compels him to adhere to the 

 older view concerning the origin of certain forms of casts namely, that 

 casts are produced by the coagulation of an albuminous substance. This 

 supposition is based on the experience that the presence of casts in the urine 

 depends upon the admixture of albumen with this secretion, since, firstly, such 

 casts are found in the urine in conditions accompanied by albuminuria ; and 

 secondly, in the great majority of cases, coincidently with the albumen, casts 

 also appear in the urine. Barters views agree with my experience, both 

 clinical and microscopical. I have not seen casts in urine, that was free from 

 albumen, but I have quite frequently examined albuminous urine in which 

 casts were not demonstrable. The more abundant the albumen in the urine 

 was, the more certainly could I expect to discover casts, and wherever I had 

 an opportunity to examine kidneys post-mortem which had excreted urine 

 rich in albumen during the life of the patient, and where there had been 

 symptoms of an acute inflammation of the kidney, every time I encountered 



" Ueber das Wesen der Harncylimler. Moleschott's Untersuclumgen," XI. Band. 

 t Ziemssen's " Handbuchder spec. Pathol. und Therap." 



