STONE, OR GRAVEL. 97 



the dissolved solids must necessarily be thrown down. Hence, calculi 

 are more conunon in stabled horses fed on dry grain and hay, in those 

 denied a sufficiency of water or that have water supplied irregularly, 

 in those subjected to profuse perspiration (as in summer), and in 

 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 by 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 carbon- 

 ates, 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, Derbyshire, 

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

 in France ; and Munich, in Bavaria. 



But the saturation of the urine from any or all of theSe conditions 

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

 efficient one, excej^t on the rarest occasions. For a more direct and 

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

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

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

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

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

 ually of a high density and having the mineral constituents in excess 

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

 urine of low specific gravity will have a calculus. 



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- 



H. Do<\ 7m, .50-2 7 



