202 URINARY SEDIMENTS. 



a matter of doubt. The condition of the cells, however, 

 may furnish information of the pathological changes which 

 have taken place. If they appear disintegrated or contain 

 fat-globules, their origin is from the locality of some de- 

 generative process, often of a chronic nature. 



Blood-corpuscles are not normal in urine. In freshly- 

 voided urine they may retain their normal shape, that of 

 a biconcave disk. (Plate III, 13, d.) In acid urine, espe- 

 cially where the specific gravity is high, they shrivel after 

 a time, the margins becoming irregular. In dilute urine 

 and where the reaction is alkaline the corpuscles swell, 

 and become biconvex or spherical. If there is much blood 

 the liquid is reddish, but a slight amount may escape de- 

 tection by the unaided eye. When it is present the albu- 

 min reactions can always be obtained. 



By urinary cast is meant an irregularly-cylindrical 

 mass, composed of various materials, which have been 

 formed in the tubules of the kidney, and hence are of 

 about the same size as the tubules. Opinions vary as to the 

 cause of their formation, but most casts appear to be due 

 to the coagulation of the serum which passes into the 

 renal vessels owing to some pathological condition. The 

 presence of anatomical elements such as epithelium, pus, 

 blood, and fat or their decomposition products in the 

 coagulated mass gives the different varieties of casts. 



Epithelial casts are not very common. They consist 

 of cylindrical-shaped masses of round epithelial cells which 

 are thrown off from the tubules by some pathological proc- 

 ess. The cells may appear normal or they may be more 

 or less decomposed and of a granular appearance, or they 

 may contain minute fat-globules. The cells sometimes 

 seem to compose the whole cast and sometimes to be scat- 

 tered over its surface. (Plate III, 16.) When present, 



