CASTS. 203 



they indicate inflammation of the kidney. When the cells 

 are degenerated, the indications are that the condition is 

 chronic or has existed for some time. 



Blood-casts consist of coagulated blood often contain- 

 ing so many red corpuscles that they are dark and non- 

 transparent. They may be formed whenever haemorrhage 

 occurs in the urinary tubules, and are the best evidence of 

 this. They are quite rare, and may be obscured under the 

 microscope by the free blood-corpuscles. 



Casts of pus are also very rare, but pus-corpuscles 

 are not infrequently seen in other varieties of casts. 



By the decomposition and metamorphosis of epithe- 

 lium, blood- or pus- cells in casts, the so-called granular 

 casts have their origin. They vary greatly in size, shape, 

 color, and in fineness of granulation. (Plate III, 15.) 

 The finely granular cannot be easily seen except with a 

 high power of the microscope, although the coarsely granu- 

 lar may be observed with a low degree of magnification. 

 They often contain unaltered epithelium, leucocytes, and 

 fat-globules. Granular casts indicate degeneration or a 

 long-continued pathological condition of the kidney. 



Occasionally casts of fat-globules are observed. They 

 result from farther metamorphosis of the granular casts. 

 (Plate III, 18, a.) 



In diseases of the kidney, like interstitial suppurative 

 nephritis, where bacteria are abundant, casts composed of 

 these organisms are often seen. They resemble granular 

 casts, but are not destroyed by mineral acids and caustic 

 alkalies, as are the granular casts. High powers of the 

 microscope should be used in their examination. 



Hyaline casts are almost transparent or at most show 

 only a very fine granulation. On account of their great 

 transparency they are extremely difficult to perceive. 



