752 THE UEINAEY TRACT. 



nephritis, especially so the article on chronic nephritis, which is 

 based on researches extending over years. The secondary changes 

 of the kidney-tissue, embracing the formation of cysts, the fatty 

 and waxy degeneration, are cleared up in a satisfactory manner. 



Here I briefly wish to allude to the peculiar formations, termed 

 tubular casts, which are observed under the microscope in the 

 urine as well as in the tubules of the kidneys. They were first 

 described as occurring in both situations by Henle in 1842, who 

 considered them to be coagulated fibrine. Since that time the 

 views concerning their origin have greatly changed ; they were 

 considered as products of secretion of the epithelia of the 

 tubules, or as transformed epithelia, but the participation of the 

 blood in the formation of casts was neglected. N. A. J. Voor- 

 hoeve,* in an excellent article, gives the results of experiments 

 made for the purpose of tracing the origin of the casts in the 

 tubules. This author produced casts in rabbits' kidneys by 

 administration of cantharides and of neutral chromate of am- 

 monia, and by ligation of the ureters, and especially by a tempo- 

 rarily impeded circulation in the kidneys through compression 

 of the renal artery and the renal veins. He comes to the conclu- 

 sion that only the dark granular casts are due to a disintegration 

 of the tubular epithelia, while hyaline casts are caused by dis- 

 turbances in the vascular system, without the least participation 

 on the part of the epithelia, He claims having observed within 

 the tubule the epithelial wreath around each cast. Numerous 

 observations in inflamed kidneys led me to the conclusion that 

 the wreath of partly nucleated flat bodies around the casts are 

 not epithelia, but the grown-up endothelia, subjacent to the epi- 

 thelial cover, while the epithelia, being saturated with an exudate 

 from the neighboring blood-vessels, are transformed into the mass 

 composing the cast. How this conception has developed is shown 

 by the foregoing and the two following articles. A simple 

 hyperaemia of the kidneys cannot, as is generally believed, lead 

 to the formation of the casts, as they are always the products 

 of an inflammatory action, which is also well marked in the 

 surrounding connective tissue. Voorhoeve's experiments eluci- 

 date the probable source of nephritis in pregnancy, which in 

 all evidence is caused by a pressure on the renal vein of the 

 pregnant uterus, mostly in the right kidney. 



Nephritis, as every other disease, is marked by various degrees 



* " Ueber des Entstehen der sogeiiannten Fibrincy Under." Virchow's 

 Archiv, LXXX. Bd., 1880. 



