24 DISEASES OF THE KIDNEY. 



cylinders should be distinguished from those so-called epithelial 

 tubes formed by separation of long pieces of the lining of the 

 straight tubes, and recognizable under the microscope as oblong 

 rolls of epithelial cells. Such casts appear in the less serious dis- 

 eases of the kidney ; hence their temporary presence warrants a 

 favorable prognosis unless gainsaid by other signs. The cylinders 

 proper belonging to the graver malady are solid plugs of exudation 

 which have filled portions of tubes. There are two typical forms of 

 them, with intermediate varieties : 1. Hyaline casts, which, though 

 well defined, are transparent as glass, and hence are apt to be over- 

 looked unless foreign matter adheres to them ; 2. Granular casts, 

 more or less closely studded by minute fat-globules. Hyaline casts 

 are probably formed by the exudation of a fibrogenous substance, 

 which becomes fibrin within the tubules. Some ascribe their ori- 

 gin to colloid metamorphosis of the epithelium. Another special 

 modification of the hyaline cast is the waxy cast, which proceeds 

 from the former, and is to be distinguished from it by its greater 

 consistence, its yellowish color, and its more distinct outline. By 

 many, granular casts are supposed to be the product of fatty meta- 

 morphosis of hyaline cylinders ; others regard them as the result of 

 croupous degeneration of the tubular epithelium. Other objects 

 are often found adhering to the casts, such as pus, white blood-cor- 

 puscles, blood-disks, degenerated epithelium, and clusters of fat- 

 globules, vestiges of broken-down cells ; likewise the various crys- 

 tals which are found in the urine. All the above-named objects 

 are also found free in the urine of Bright's disease. During an in- 

 flammatory relapse an exceptionally large number of casts will 

 appear in the urine ; otherwise they are not numerous, and some- 

 times can only be found after filtering the urine and examining 

 the dregs. Urinary casts are not a pathognomic sign of Bright's 

 disease, for they are found, as we shall see, in other renal affec- 

 tions ; nor can we positively determine the form or stage of the 

 disorder frem the character of the casts. Nevertheless, the discov- 

 ery of many casts, both hyaline and granular, with here and there 

 an adhering lymph-cell or granular epithelial cell, favors a diagno- 

 sis of an active progressive inflammation (a parenchymatous ne- 

 phritis) ; while, if the casts are few, small, and hyaline, or if they 

 are absent altogether, the urine being profuse, clear, and scant of 

 sediment, we may suppose the disease far advanced, and that the 

 kidney is shrunken (interstitial nephritis).] 



Dropsy is one of the most characteristic signs of Bright's disease, 

 excepting in a few rare instances, in which it has been absent through- 

 out the entire course of the malady. It generally begins as anasarca. 



