Two forms of calculi have been found in the prostate in domestic animals: 1st, small, round, angular or branched bodies made up in concentric layers and formed of organic nitrogenous bodies: and 2nd, genuine calculi of calcium phosphate or ammonia magnesian phosphate. These may cause pressure on the parenchymatous tissue and atrophy, but in the lower animals they are seldom the direct cause of prominent morbid symptoms. They must, however, be recognized as one of the causes of chronic irritation that contribute to prostatic inflammation and hypertrophy.