Urinary Calculi (Stone, or Gravel).

These consist in some of the solids of the urine that have been precipitated from the urine in the form of crystals, which remain apart as a fine, powdery mass, or magma, or aggregate into calculi, or stones, of varying size. (See Pl. XI.) Their composition is therefore determined in different animals by the salts or other constituents found dissolved in the healthy urine, and by the additional constituents which may be thrown off in solution in the urine in disease. In this connection it is important to observe the following analysis of the horse's urine in health:

Water	918.5
Urea	13.4
Uric acid and urates	.1
Hippuric acid	26.4
Lactic acid and lactates	1.2
Mucus and organic matter	22.0
Sulphates (alkaline)	1.2
Phosphates (lime and soda)	.2
Chlorids (sodium)	1.0
Carbonates (potash, magnesia, lime)	16.0
	1000.0

Source: Diseases of the Horse