source of special information made use of has been enumerated. For the argumentative portion of the present essay the author is alone responsible. H. V. C. June, 1873. PART I THE MICROSCOPIC STRUCTURE OF URINARY CALCULI ABOUT one half the specimens examined were submitted to inspection very soon after their extraction, but I do not know that in them, the internal appearances were in any way different from those observed in calculi, which had been kept for months or years. Copious notes were made of every specimen, which I have preserved; nothing is here stated that has not been seen and carefully scrutinised; and on the other hand, no marked exception was met with to the general results, as now recorded. It was not practicable to add descriptions or figures of the several calculi examined, otherwise this demonstration of their structure would have been more complete; nor is it pretended to have nearly exhausted the subject; on the contrary, there are numerous points well meriting discussion which I have abstained from entering upon in a first essay; such are the probable bases of the uric acid salts, the combinations of the calcium phosphate, and the likely complex composition of some submorphous forms, here attributed to calcium oxalate. The polariscope was frequently employed, but as, on the whole, its indications were not, in my hands, of a decided character, no mention is made of them. The plan adopted was as follows:-Each calculus was divided on one side of the middle, the actual centre was then made out as far as possible, and fragments of the nucleus and of succeeding layers, were carefully examined under various optical powers, and with the aid of chemical reagents. Entire sections were made of a few typical specimens, and have been preserved, and especial attention was given to the nature of the nuclear portions or first-formed ingredients of the calculi, as a point of chiefest interest; for it is obviously desirable to ascertain in what form these concretions primarily appear, with a view to their early diagnosis, and to the possible prevention of their increase. After sufficient practice, it becomes apparent that the microscopic analysis of urinary calculi is not only valuable, but that it is even more delicate than the chemical method; by its aid will be seen still more clearly than before, that no single urinary deposit long occurs alone, and there will be gained a more accurate conception of the real structure of these hurtful concretions. Respecting the eighty specimens submitted to examination, the following brief details may be appended : Five of the whole number, or 6 per cent., were removed from the female bladder; 13, or 15 per cent., were urethral, or more rarely renal, calculi from males; 62, or 79 per cent., were vesical calculi extracted by lithotomy from male subjects, whose ages varied from two and a half years to sixty years, about one half, however, being under ten years of age, and but nine |