DISEASES OF THE HOESE. 97 



those suffering from a watery diarrhea. On the whole, calculi are 

 most commonly found in winter, because the horses are then on dry 

 feeding, but such dry feeding is even more conducive to them in 

 summer when the condition is aggravated by the abundant loss of 

 water b}^ the skin. 



In the same way the extreme hardness of the water in certain dis- 

 tricts must be looked upon as contributing to the concentration of the 

 urine and correspondingly to the production of stone. The carbonates^ 

 sulphates, etc., of lime and magnesia taken in the water must be again 

 thrown out, and just in proportion as these add to the solids of the 

 urine they dispose it to precipitate its least soluble constituents. Thus, 

 the horse is very obnoxious to calculi on certain limestone soils, as 

 over the calcareous formations of central and western New York, 

 Pennsylvania, and Ohio, in America; of Norfolk, Suffolk, Derbj^shire, 

 Shropshire, and Gloucestershire, in England; of Poitou and Landcs, 

 in France; and Munich, in Bavaria. 



But the saturation of the urine from an}^ or all of these conditions 

 can only be looked on as an auxiliar}^ cause, and not as in itself an 

 efficient one, except on the rarest occasions. For a more direct and 

 immediate cause we must look to the organic matter which forms n 

 large proportion of all urinary calculi. This consists of mucus, albu- 

 men, pus, hyaline casts of the uriniferous tubes, epithelial cells, blood, 

 etc., mainly agents that belong to the class of colloid or noncrystalline 

 bodies. A horse may live for months and years with the urine habit- 

 uallj" of a high density and having the mineral constituents in excess 

 without the formation of stone, or gravel; and again one with dilute 

 urine of low specific gravity will have a calculus. 



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

 show that a colloid bod}^, like mucus, albumen, pus, or blood, deter- 

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

 the}^ 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 decomj^osition 

 is specialh" 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 bacte- 

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

 14384—03 7 



