83 



Rainey, Orel, and others furnish the exphmation. They not only 

 show that a colloid bodj*, like nmcus, albumen, pus, or blood, deter- 

 mined the i^recipitation or the ciystalline salts in tlie solution, but 

 they determined the precij)itation 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 speciallj^ 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 esx)ecially all those conditions which determine the i^resence 

 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 b}' the fact that these bodies are liable to carry bacte- 

 ria into the passages and thus determine decomj)ositiou, and they are 

 further liable to irritate the mucous membrane and become enveloped 

 in ji coating of mucus, x)us, and perhaps blood. 



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

 nmgnesian limestones, the same districts in which they suffer from 

 goiter, may be similarly explained. The unknown poison whicli jiro- 

 duces goiter iDresumabl}^ 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 accord- 

 ing to the place where they are found, renal (kidney), uretral (ureter), 

 vesical (bladder), urethral (urethra), n^xid preputial (sheath or prepuce). 

 They have been otherwise named according to their most abundant 

 chemical constituent, carhonate of lime, oxalate of lime, and phosp)hate 

 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 kidne}^ may have two or three sliort branch-like pro- 

 longations, while those in the bladder are round, oval, or slightly flat- 

 tened upon each other. Calculi containing oxalate of lime, on the 

 other hand, have a rough, open, cr3'stalline 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 b}' their 

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

 deep brown, the shades depending mainlj^ on the amount of the color- 

 ing matter of blood, bile, or urine Avhich they may contain. 



Bcnal Calculi. — These may consist of minute, almost microscoijic, 

 deposits in the urinifei-ous tubes in the substance of tlie kidney, but 



