204 URINARY SEDIMENTS. 



They may be colored yellow by adding a solution of iodin. 

 In shape they are usually long and narrow. Besides these 

 narrow hyaline casts, which probably are formed in the 

 smaller tubules, there is sometimes found a broader vari- 

 ety. (Plate III, 17.) These have an indented edge and, 

 in consequence of being more highly refractive, can be 

 seen more easily than the narrow ones. They are called 

 waxy . casts. They often give the amyloid reaction, a 

 brown color with iodin, turning blue to violet upon 

 acidifying with sulphuric acid. They are doubtless formed 

 in the renal pyramids. The narrow casts dissolve readily 

 in acetic acid, but the waxy casts remain in it for some 

 time. Hyaline casts not infrequently have anatomical ele- 

 ments blood- and pus- corpuscles, epithelium, etc. 

 clinging to the surface or included within the mass. 



The origin of the hyaline casts seems to be due to 

 the coagulable elements of the blood. It is doubtful if 

 they are ever present in urine which has not been albu- 

 minous. Their presence, consequently, is indicative of 

 the existence of albuminuria. They may be the best evi- 

 dence of such a condition as interstitial nephritis, where 

 the amount of albumin is small. 



Whatever variety of cast may be present in urine, it 

 shows, without any doubt, that there is a pathological con- 

 dition of the kidney and that the accompanying albumin 

 is of renal origin. 



Besides these cylindrical casts there sometimes appear 

 in the urine the so-called cylindroids. These are flat or 

 ribbon-shaped, rather than cylindrical. They are usually 

 about the diameter of casts, but longer, and resemble in 

 their transparency and solubility the hyaline casts, their 

 composition being probably the same. They are found in 

 nephritis and congestion of the kidneys, also in cystitis. 



