98 DISEASES OF THE HORSE. 



tion of mucus or pus, become direct causes of calculi. Foreign bodies 

 of all kinds in the bladder or kidney have long been known as deter- 

 mining causes of calculi and as forming the central nucleus. This is 

 now explained by the fact that these bodies are liable to carry bacte- 

 ria into the passages and thus determine decomposition, and they are 

 further liable to irritate the mucous membrane and become enveloped 

 in a coating of mucus, pus, and perhaps blood. 



The fact that horses appear to suffer from calculi, especially on the 

 magnesian limestones, the same districts in which they suffer from 

 goiter, may be similarly explained. The unknown poison which pro- 

 duces goiter presumably leads to such changes in the blood and urine 

 as will furnish the colloid necessary for precipitation of the urinary 

 salts in the form of calculi. 



CLASSIFICATION OF URINARY CALCULI. 



These have been named according to the place where they are 

 found, renal (kidney), uretral (ureter), vesical (bladder), urethral 

 (urethra), and preputial (sheath, or prepuce). They have been 

 otherwise named according to their most abundant chemical constit- 

 uent, carl)onate of lime^ oxalate of lime^ and phosphate of lime calculi. 

 The stones formed of carbonates or phosphates are usually smooth 

 on the surface, though they may be molded into the shape of the 

 cavity in which they have been formed ; thus those in the pelvis of 

 the kidney may have two or three short branchlike prolongations, 

 while those in the bladder are round, oval, or slightly flattened upon 

 each other. Calculi containing oxalate of lime, on the other hand, 

 have a rough, open, crystalline surface, which has gained for them 

 the name of mulberry calculi, from a supposed resemblance to that 

 fruit. These are usually covered with more or less mucus or blood, 

 produced by the irritation of the mucous membrane by their rough 

 surfaces. The color of calculi varies from white to yellow and deep 

 brown, the shades depending mainly on the amount of the coloring 

 matter of blood, bile, or urine which they may contain. 



Renal calculi. — These may consist of minute, almost microscopic, 

 deposits in the uriniferous tubes in the substance of the kidney, but 

 more commonly they are large masses and lodged in the pelvis. The 

 larger calculi, sometimes weighing 12 to 24 ounces, are molded in the 

 pelvis of the kidney into a cylindroid mass, with irregular rounded 

 swellings at intervals. Some have a deep brown, rough, crystalline 

 surface of oxalate of lime, while others have a smooth, pearly white 

 aspect from carbonate of lime. A smaller calculus, which has been 

 called coralline, is also cylindroid, with a number of brown, rough, 

 crystalline oxalate of lime branches and whitish depressions of car- 

 bonate. These vary in size from 15 grains to nearly 2 ounces. Less 

 frequently are found masses of very hard, brownish white, rounded. 



