332 Veterinary Medicine. 



The calculi containing an excess of ammonio-magnesian phos- 

 phate tend to assume a crystalline or coralline form which causes 

 them to be specially irritating to the mucosa. When broken they 

 show a radiated structure from the centre to the circumference in 

 addition to the concentric rings. These are usually of a yellowish 

 brown or a gray color and have a specific gravity of 1694 to 1706. 



Calculi in which the common phosphate of lime abounds are 

 likely to be smooth on the surface and on section show the con- 

 centric rings more distinctly and the radiating lines less so. The 

 brownish calculi of this variety are much more compact, and 

 harder than the crystalline or mulberry caculi, and have a 

 higher specific gravity — (1823). 



Bluish calculi with a smooth glistening surface and lower spe- 

 cific gravity — 1681 — , have been found of small size and in great 

 numbers in the colon (1000 in the colon, Gurlt). 



In some calculi there is a large admixture of alimentary mat- 

 ters, and a low specific gravity (1605 to 1674). These were des- 

 ignated aspseudo calculi, by Fiirstenberg. 



In still other cases a calculous looking mass, when broken into, 

 is found to be composed of a mass of dried alimentary matter 

 enclosed in a thin layer of lime salts. These have a low specific 

 gravity (1446 to 1566) and have been named concretions by Fiirs- 

 tenberg. 



Causes. As a large proportion of the calculus is phosphate of 

 lime or ammonio-magnesian phosphate, we must look for the 

 source of these in the food and then at the conditions which de- 

 termine their precipitation. 



The percentage of ash and of phosphoric acid in the common 

 foods of horses may be seen in the following table : 



As,h p Os in PO s inthe 



the Ash. entire food. 



Per cent. Per cent. Per cent. 



Wheat bran 7.3 50 3.65 



Wheat grain 3.0 46.38 1. 3914 



Oats grain 2.50 26.5 0.6625 



Barley grain 3.10 39.9 1.2276 



Bean grain 3.10 31.6 0.9864 



Pea grain .2.75 34.8 0.957 



Tare grain 3.00 36.2 1.086 



Indian corn grain 1.5 



Rye grain 1.6 39.9 1.0384 



