Hydatids, though seldom met with in the human kidney, are not unfrequently found in that of the dog. All these are circumstances that have not received sufficient attention. CALCULOUS CONCRETIONS are of more frequent occurrence than is generally imagined, but they are not confined to the kidneys; there is scarcely a portion of the frame in which they have not been found, particularly in the brain, the glandular substance, and the coats of the intestines. I cannot say with Mr. Blaine that I have seen not less than 40 or 50 calculi in my museum; but I have seen too many fearful examples of the complaint. There has been usually great difficulty in the urinary evacuation; and at length one of the calculi enters the urethra, and so blocks up the flow of the urine that mortification ensues. M. Lautour relates a case of renal calculus in a dog. He had occasionally voided his urine with some difficulty, and had walked slowly and with evident pain. August 30, 1827, a sudden exacerbation came on, and the dog was dreadfully agitated. He barked and rolled himself on the ground almost every minute; be made frequent attempts to void his urine, which came from him drop by drop. When compelled to walk, his hind and fore legs seemed to mingle together, and his loins were bent into a perfect curve; his flanks were drawn in; he could scarcely be induced to eat; and he evidently suffered much in voiding his fæces. Mild and demulcent liquids were his only food. Warm baths and injections were applied almost unceasingly, and in eight days he seemed to have perfectly gained his health. In March, in the following year, the symptoms returned with greater intensity. His hind limbs were dragged after him; he rapidly lost flesh, and his howlings were fearful and continuous. The same mode of treatment was adopted without any good effect, and, his cries continuing, he was destroyed. The stomach and intestines were healthy. The bladder was enlarged from the thickness and induration of its parietes; the mucous membrane of it was covered with ecchymoses; the kidneys were three or four times their natural size; and the pelvis contained a calculus weighing 126 grains, composed of 58 grains of uric acid and 58 of ammonia, with 10 grains of phosphate of lime. Of the nature and causes of urinary calculi in the bladder we know very little. We only know that some solid body finds its way or is formed there, gradually increases in size, and at length partially or entirely occupies the bladder. Boerhaave has given a singular and undeniable proof of this. He introduced a small round pebble into the bladder of a dog. The wound perfectly healed. A few months afterwards the animal was killed, and there was found a calculus of considerable size, of which the pebble was the nucleus.