260 THE AMERICAN MONTHLY [Sept. 



blood-corpuscles (fig. 7). They are soluble in acetic 

 acid. (2) Epithelial casts, made up of columnar epithe- 

 lium or of round cells (fig. 8). (3) Hyaline casts are made 

 up of a translucent, homogeneous, slightly refractive, 

 and often barely visible, flexible, proteid material (fig. 

 9). They are unaffected by acetic acid. (4) Waxy casts, 

 are made up of very refractive and brittle proteid matter. 

 As a rule they are longer than the others, somewhat re- 

 sembling a segment of the tape worm. They are so of- 

 ten found broken after leaving the kidney, that in the 

 microscopic field they are seen in short fragments, 

 notched and bearing upon their surface white and red 

 blood corpuscles, fatty globules, arranged separately or 

 in confluent masses, either a coating of urates or dotted 

 with crystals of various kinds, and fungi. (5) Granular 

 casts are dark opaque bodies composed of granular ma- 

 terial and covered with granular cells. They differ much 

 in character and no positive diagnosis can be formed upon 

 them alone. They may be of all shades, from pale yel- 

 low to reddish brown. They are usually seen in frag- 

 ments of various lengths and widths with well defined 

 borders, but the bodies are variously tapered and bent 

 (fig. 10), they are sometimes coated with pus cells, fatty 

 globules and crystals. (6) Fatty casts are highly re- 

 fracting bodies made up of epithelial, hyaline, waxy or 

 granular casts, filled with fatty globules. 



Urea. — This is the most abundant and most important 

 of the organic constituents of urine. To determine the 

 presence of urea, take an inch of a small thread of cotton, 

 dip one end into the urine and place it with its hanging 

 drop at the center of a slide, then cover with a thin glass 

 leaving half of the thread free. Upon this free end let 

 fall a minute drop of nitric acid and place the slide un- 

 der the microscope. The formation of the plate crystals 

 will afford an interesting field. 



Among other interesting things which urine may con- 



