The Abdomen 217 



acid diathesis. Calculi of oxalates (calcium and ammonium oxal- 

 ates) are believed to occur as a result of oxalic diathesis, and ox- 

 alic acid being a derivative of uric acid, the oxalic acid diathesis 

 is a secondary manifestation of the uric acid diathesis. They are 

 hard, variably shaped, but often mulberry-like, and brown or yel- 

 low. Calculi of cystin are also believed to be derivatives of 

 imperfect metabolism of nitrogenous substances. They are soft, 

 waxy, and brownish yellow. All these varieties are found pure or 

 mixed in aseptic acid urine, the local lesion necessary to their pro- 

 duction being inappreciable, but the principal role being played by 

 the uric acid diathesis. The calculi of alkaline urine are mostly 

 secondary to them. 



When the crystals form and persist as small gritty particles 

 the condition is termed "sand," "gravel," or sediment. If the 

 crystalline particles become agglutinated by renal or vesical mucus, 

 albumen, degenerated epithelium, or blood clots, the nucleus is 

 started, which grows by further accretion, until a "stone" or 

 calculus is formed. 



The other varieties, i. e., phosphates and carbonates (am- 

 monio-magnesium-phosphate, calcium phosphate, calcium carbonate) 

 occur in alkaline urine, and probably often secondary to the acid 

 deposits, a primary acid calculus becoming the seat of phosphatic 

 deposit through the development of alkaline urine as a result of 

 disease of the tract. It is probable that alkaline urine and the pre- 

 sence of products of local tissue degeneration may also result in 

 primary precipitation of phosphates and carbonates. Alkaline urine 

 results from fermentative changes incident to catarrhal inflamma- 

 tions. The latter condition is not uncommon in old dogs suffering 

 from hypertrophy of the prostate with consequent local debilitating 

 effect of stagnating urine. These calculi, with the exception of 

 those formed of triple phosphate, are hard, smooth, and white or 

 greyish, and attain considerable size. The triple phosphatic calculi 

 have rough jagged surfaces. 



All these substances may assist in the formation of a single 

 calculus. A uric acid nucleus may be surrounded by phosphates 

 in the presence of altered reaction of the urine. A return of acid 

 reaction is followed by another layer of uric or urate deposit, and 

 so on. 



The smaller breeds are more subject to urinary deposits than 



