160 DISEASES OF CATTLE. 



specific gravity is 1760, water being 1000, and they coitain 74 per cent 

 of carbonate of lime with some carbonate of magnesia, organic matter, 

 and a trace of carbonate of iron. Yellowish-white, smooth, round cal- 

 culi of the same chemical composition are met with. 



(2) Pearly calculi. These are more frequent than the first named 

 variety. They are very hard and smooth on the surface, reflecting a 

 play of various colors after the fashion of a pearl. This peculiarity 

 appears to be caused by the thinness and semi-transparency of the 

 superposed layers. They have a specific gravity of 2109 to 2351, and 

 nearly the same chemical composition as the coralline variety. Golding 

 Bird found a specimen of this kind formed of carbonate of lime and 

 organic matter only. 



(3) Green calculi. Metalloid calculi. These are usually small and 

 numerous, as they are exceedingly common. They are of a very hard 

 consistency, and have a clear, polished, greenish surface of almost 

 metallic brilliancy. They have a specific gravity of 2301, and a compo- 

 sition almost identical with the second variety. 



(4) White calculi. Pure, white, smooth, lustrous calculi are rare. 

 They have a specific gravity of 2307, and contain as much as- 92 per 

 cent of carbonate of lime with carbonate of magnesia and organic 

 matter. 



(5) Ammonio-magnesium calculi. These are of a grayish color and a 

 very rough crystalline surface, which proves very irritating to the 

 mucous membrane. They have a specific gravity of 1109 to 1637, and 

 are composed chiefly of ammonio-magnesium phosphate, oxalate of 

 lime, and organic matter, with some little carbonate of lime and mag- 

 nesia. 



(6) Siliceous calculi. These are clear, smooth, and hard, and usually 

 spherical. They have a specific gravity of 1265 to 1376, and contain 

 57 per cent of silica with carbonates of iron and magnesia, organic 

 matter, and traces of iron. In other specimens of siliceous calculi there 

 was a specific gravity of 3122, and there was 79 to 85 per cent of car- 

 bonate of lime together with carbonate of magnesia, and iron, silica, 

 and organic matter. Others are almost exclusively made of silica. 



(7) Oxalate of lime calculi. Mulberry calculi (Plate xi, Fig. 2). These 

 are characterized by their extremely rough, angular surface, formed by 

 the octahedral crystals of oxalate of lime. Their specific gravity may 

 be 3441, and they contain oxalate of lime to the extent of 81 per cent, 

 together with carbonates of lime and magnesia and organic matter. 



(8) Gravel. Pultaceous deposits. Simple crystals may be met with 

 at any point from the kidneys to the external opening at the end of the 

 prepuce (sheath), and they may appear singly, as crystals, or they may 

 accumulate in masses of fine spherical crystals almost like dirty pow- 

 dered chalk suspended in water. In the ox this is especially common 

 as a collection in the sheath, distending that into a soft doughy swelling. 



