DISEASES OF THE UEINABY OKGANS. 157 



Rainey, Ord, and others furnish the explanation. They not only 

 show that a colloid body, like mucus, albumen, pus, or blood, deter- 

 mined the precipitation or the crystalline salts in the solution, but 

 they determined the precipitation in the form of globules, or spheres, 

 capable of developing by further deposits into calculi. Heat intensi- 

 fies this action of the colloids, and a colloid in a state of decomposition 

 is specially active. The presence, therefore, of developing fungi and 

 bacteria must be looked upon as active factors in causing calculi. 



In looking, therefore, for the immediate causes of calculi we must 

 consider especially all those conditions which determine the presence 

 of albumen, blood, and excess of mucus, pus, etc., in the urine. Thus 

 diseases of distant organs leading to albuminuria, diseases of the kid- 

 neys and urinary passages causing the escape of blood or the forma- 

 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 bac- 

 teria into the passages and thus determine decomposition, and they 

 are further liable to irritate the mucous membrane and become envel- 

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



The fact that horses, especially on the magnesian limestones, the 

 same districts in which they suffer from goiter, appear to suffer from 

 calculi 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 UKINART CALCULI. 



These have been named according to the place where they are 

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

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

 otherwise named according to their most abundant chemical constit- 

 uent, carbonate of lime, oxalate of lime, and phosphate of lime cal- 

 culi. The ^ones 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 



