98 BUREAU OF AT^^IMAL INDUSTRY. 



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 tho}' suffer from 

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

 duces goiter presumabl}^ 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 wdiere they arc found, 

 Q'cnal (kidney), 'v.retral (ureter), vesical (bladder), urethral (urethra), 

 and preputial (sheath, or prepuce). The}^ have been otherwise named 

 according to their most abundant chemical constituent^ carhonate of 

 Ihne, oxalate of lime, and phosjj/tate of lime mlculi. 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 branch-like 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 mucus 

 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 

 contiiin. 



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

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

 more commonly the}^ 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 irregulai' 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, rovigh, 

 crystalline oxalate of lime l)ranches and whitish depressions of carbon- 

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

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

 pea-like calculi. These arc smoother, but on the surface crystals of 

 oxalate of lime may be detected with a lens. Some renal calculi are 

 formed of more distinct laj^ers, more loosel}' adhei'cnt to each other, 

 and contain an excess of mucus, but no oxalate of lime. Finally, a 

 loose aggregation of small masses, forming a very friable calculus, is 



