CALCULI. 



439 



" True intestinal calculi consist principally of a deposit of an ammonio- 

 magnesium phosphate (90 per cent, according to Fiirstenberg) with which are 

 found phosphate of Ume, phosphate of magnesia, silica, certain chlorides, and 

 traces of iron and organic matter (mucus, epitheliuni and alimentary sub- 

 stances). They are formed from the phosphate of magnesia of the bran, 

 which is rich in it. This phosphate of magnesia unites with the ammoniacal 

 compounds which exist in the contents of the bowels. These compounds are 

 derived from the atmosphere of the stable, and are introduced into the 

 digestive tube along with the drinking water. An insoluble basic-phosphate 

 is thus formed in the intestines. The starting-point of the precipitation is 

 generally a foreign body, such as a grain of sand or an oat, around which layers 

 of basic phosphate are continually deposited" {Friedbey^ger and Frohner). 

 The foregoing remarks on the formation of a calculus naturally suggest the 

 inference that the more loaded with ammonia the air of a stable is, the more 

 likely will calculi be formed in the intestines of horses living in such a stable. 

 Bearing on this subject, there are two facts which deserve notice. First : 

 Continental veterinary authorities are unanimous in saying that the feed- 

 ing of horses on bran is a fertile cause of calculi in the intestines of such 

 animals. Second : For the last thirty -five years I have fed horses on bran 

 combined with oats or other grain, and have known thousands of other horses 



Fig. 144. — Dust ball. 



similarly fed ; but have not met with a single ease of calculus from such 

 regimen, which was given, however, under good sanitary conditions. I there- 

 fore conclude that there is no danger of intestinal calculi from feeding horses on 

 bran, if the air of the stable is practically free from ammonia. 



There is some evidence to show that forage, which contains a 

 quantity of the hairs and husks of oats, or meal dust, is apt to 

 give rise to intestinal concretions, which are hardly ever found 

 among animals whose food is carefully looked after. 



An oat-hair concretion would appear to result chiefly from the 

 mechanical adherence of undigested particles of food to the moist 

 covering of a nucleus whose presence on the mucous membrane had 

 caused a certain amount of irritation. The formation of a mixed 

 calculus would probably be effected both by chemical and me- 

 chanical agencies. 



An unhealthy condition of the intestines is not seen as a rule at 

 2)ost-mortem examinations of horses affected with calculus, and, 

 therefore, it cannot be regarded as a cause of this complaint. 



