71 



formations soluble in acetic acid. They are of variable size and 

 generally difficult to detect on account of their apparently struc- 

 tureless character. At times a slight granulation may be seen 

 imbedded in or adhering to their matrix and occasionally acci- 

 dental attachments of pus or fat globules in small numbers. 



Epithelial casts have a hyaline matrix more or less concealed 

 by epithelial cells. The presence of these casts is indicative of an 

 acute process. 



Blood casts con- 



sist of the hyaline 

 matrix with blood 

 corpuscles imbed- 

 ded in or adhering 

 to the matrix. Pus 

 easts are rare, 

 but when present 

 the pus corpuscles 

 adhere to the mat- 

 rix. Blood casts 

 are indicative of a 

 hemorrhage into 

 the tubules and of 

 an acute hemor- 

 rhagic process. Hy- 

 aline and epitheli- 

 al casts are usual- 

 ly associated with them. 



Fig. 26. a. Fatty casts, b. and c. Blood 

 casts, d. Free fatty Molecules. (Roberts). 



Granular casts usually 

 have well defined boundaries 

 with granular matter im- 

 bedded in or adhering to the 

 matrix. They may be finely 

 or coarsely granular, the lat- 

 ter having a more serious 

 significance. Granular casts 

 are due to a disintegration of 

 FIG. 27. Fatty Casts and Fat Droplets, ^j^^ ^^^^^ epithelium. Their 



degree of refraction is changeable; sometimes they appear yel- 

 lowish, at other times colorless. 



Fatty casts have a hyaline matrix containing a number of 



