82 



These are the chief mineral constitvients of the urine which form 

 ingredients in tlio liorse's calculi, for though iron and manganese are 

 usually present it is only in minute quantities. 



The excess of mineral matters in a specimen of urine unquestion- 

 ably contributes to tlie formation of calculi, just as a solution of such 

 matters out of the body is increasingly disposed to throw them down in 

 the form of crj'stals as it becomes more concentrated and approaches 

 nearer to the condition of saturation. Hence, in considering tlie 

 causes of calculi we can not ignore the factor of an excessive ration, 

 rich in mineral matters and in carbonaceous matters (the source of 

 carbonates and much of the oxalates), nor can we overlook the con- 

 centration of the urine that comes from dry food and privation of 

 v>^ater, or from the existence of fever which causes suspension of the 

 secretion of water. In these cases, at least the usual amount of solids 

 arc thrown off by the kidneys, and as the water is diminished there 

 is danger of its approaching the point of supersaturation, when the 

 dissolved solids must necessarily be thrown down. Hence, calculi 

 are more common 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 iDerspiration (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 dr}^ feeding is even more conducive to them in 

 summer v,dien the condition is aggravated by the abundant loss of 

 water by the skin. 



In the same way the extreme hardness of the vv^ater 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 Avater must be again 

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

 urine they disiiose 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 auxiliary 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 a 

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

 men, pus, hyaline casts of the urTniferous 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- 

 ually of a high density, and having tlie mineral constituents in excess, 

 without the formation of stone or gi-avel; and again one with dilute 

 urine of low specific gravity will have a calculus. 



