(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-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 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 usually 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 (mulberry calculi) ([Pl. 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 crystals, 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 with 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 pelvis and two or more projections that have been molded into the corresponding branches or channels which lead to corresponding lobes of the kidney. In winter and spring small concretions in the form of plates are often met with in the branches of the pelvis, having been formed and molded in the confined space between the projecting papilla and the surrounding cuplike branch of the pelvis. Finally, the pulplike deposits in the sheath and elsewhere are made up of globular masses, individually so small as to be often practically microscopic.
STONE IN THE KIDNEY (RENAL CALCULI).
[[Pl. XI], fig. 1.]
In an animal leading the quiet, uneventful life of the ox, stones of large size may be present in the kidney without producing any disorder appreciable to the people about him. In cattle fattened on dry feed in winter, on the magnesian limestone of New York, it is exceptional to find the substance of the kidney free from calculi about the size of a grain of wheat or less, and standing out as white objects in the general red of the cut surface of the organ. Similarly around the papillæ in the cuplike arms of the pelvis we find minute, flattened or more or less rounded, yellowish-white concretions. Even the large concretions may prove apparently harmless. I have a calculus several ounces in weight which filled the entire pelvis of the kidney, that was found by accident in a fat carcass while being dressed. In work oxen, however, such concretions may give rise to symptoms of kidney disease, such as stiffness of the loins, shown especially in the acts of rising or turning, weakness of the hind parts when set to pull a heavy load, an irritability of the kidneys, shown by the frequent passage of urine in small quantity, tenderness of the loins, shown when they are pinched or lightly struck, and it may be the passage of blood or minute gritty masses with the urine. If the attack is severe, what is called "renal colic" (kidney colic) may be shown by frequent uneasy shifting of the hind limbs, shaking or twisting of the tail, looking around at the flanks, and lying down and rising again at short intervals without apparent cause. The frequent passage of urine, the blood or gritty masses contained in it, and perhaps the hard, stony cylinders around the tufts of hair of the sheath, show that the source of the suffering is the urinary organs. In bad cases active inflammation of the kidneys may set in. (See "Nephritis," [p. 123].)