136 DISEASES OF CATTLE. 



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

 metallic brilliancy. They have a specific gi-avity of 2.301 and a com- 

 position almost identical with the second variety. 



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

 They have a specific gravity of 2.307, and contain as much as 92 per 

 cent of carbonate of lime with carbonate of magnesia and organic 

 matter. 



(5) Ammonio-rndgnesium calculi. — These are of a grayish color 

 and a very rough, crj^stalline surface, which proves very irritating to 

 the mucous membrane. They have a specific gravity of 1.109 to 

 1.637, and are composed chiefly of ammonio-magnesium phosphate, 

 oxalate of lime, and organic matter, with a little carbonate of lime 

 and magnesia. 



(6) Siliceous calculi. — These are clear, smooth, and hard, and usu- 

 ally spherical. They have a specific gravity of 1.265 to 1.376, 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 3.122, and there was 79 to 85 

 per cent of carbonate 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 {?nulberry calculi) (PI. 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 3.441, 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 crys- 

 tals, or they may accumulate in masses of fine spherical crystals 

 almost like dirty powdered chalk suspended in water. In the ox 

 this is especially common as a collection in the sheath, distending 

 that into a soft, doughy swelling. 



FORMS OF CALCULI IN DIFFERENT SITUATIONS. 



Apart from the rough crystalline surfaces of the calculi of oxalate 

 of lime and ammonio-magnesium phosphate, the general tendency is 

 to a smooth, round outline. At times, however, they show more or 

 less flattening w^ith rounded angular edges, caused by the contact 

 and mutual friction of two calculi. Sometimes two or more stones 

 lying together become united into one by a new external deposit, 

 and the resulting mass then shows rounded swellings on opposite 

 sides. The large calculi occupying the pelvis of the kidneys usually 

 show a central part having the outline of the main cavity of the 



