URINE. 



355 



is very important because of the fact that they generally indicate 

 some kidney disorder; if albumin accompanies the casts the indica- 

 tion is much accentuated. Casts have been classified according to 

 their microscopical characteristics as follows: (a) Hyaline, (b) 

 granular, (c) epithelial, (d) blood, (e) fatty, (/) waxy, (g) pus. 

 (a) Hyaline Casts. These are composed of a basic material 

 which is transparent, homogeneous and very light in color (Fig. 

 107, p. 354). In fact, chiefly because of these physical properties, 



FIG. 108. 



GRANULAR CASTS. (After Peyer.) 



they are the most difficult form of renal casts to detect under the 

 microscope. Frequently such casts are impregnated with deposits 

 of various forms, such as erythrocytes, epithelial cells, fat globules, 

 etc., thus rendering the form of the cast more plainly visible. 

 Staining is often resorted to in order to render the shape and char- 

 acter of the cast more easily determined. Ordinary iodine solution 

 (I in KI) may be used in this connection ; many of the aniline dyes 

 are also in common use for this purpose, e. g., gentian-violet, Bis- 

 marck-brown, methylene-blue, fuchsin and eosin. Generally, but 

 not always, albumin is present in urine containing hyaline casts. 

 Hyaline casts are common to all kidney disorders, but occur par- 

 ticularly in the earliest and recovering stages of parenchymatous 

 nephritis and in interstitial nephritis. 



