The results of exploratory puncture have been before alluded to. If a piece can be brought away large enough to be examined microscopically, it may settle the diagnosis, not only as to a malignant growth, but also as to its kind. The distinction between carcinoma and sarcoma cannot always be made during life, nor indeed, without a microscopical examination, after death. It is of importance chiefly with reference to prognosis after operation for removal of the organ. A more rapid growth, a greater tendency to invade other organs, and a more marked cachexia would speak in favor of carcinoma, while a tumor gradually attaining a very large size, and not spreading beyond the kidney and its immediate envelopes, is more likely to be a sarcoma. There is no TREATMENT known to be of value in cancer or sarcoma of the kidney, except so far as it may diminish pain or regulate the secretions. Surgically, removal of the diseased organ is the only expedient to be thought of. Although nephrectomy has been shown to be a perfectly practicable operation, and one that is usually well borne when the other kidney is sound, it has not proved very successful with malignant growths, even as a temporary expedient. This is partly at least to be accounted for by the difficulties lying in the way of diagnosis in the earlier stages, and the reluctance with which so serious an operation would naturally be resorted to until hopes based either on the uncertainties of diagnosis or mistaken reliance on medical treatment have been given up. Cases, however, have been reported where patients have recovered from the operation, and the disease has not returned for some months. When an operation has been resorted to, the tumor has usually become too large to be extracted through the loin, and laparotomy has been the course {63} pursued. According to Billroth,[22] out of 33 operations for tumors of the kidney, 13 have been cured. [Footnote 22: _Mittheil. der Aerzte in Nieder Oesterreich_, Bd. x. p. 161 _et seq._] Cysts. Three kinds of cysts are met with in the kidney besides those connected with the growth of parasites. Kidneys congenitally affected with cystic degeneration contain a large number of sacs lined with a vascular membrane, among the partitions of which are found the remains of secreting structure. Both kidneys are equally affected, and are enlarged and more or less lobulated. They are occasionally so large as to constitute an obstacle to labor, and various operative procedures, even evisceration, have been required to accomplish the delivery of the foetus affected. The cysts are filled with fluid of various degrees of darkness of color from almost perfect limpidity to almost black. The fluid in the smaller cysts, at least, contains some of the urinary solids. The slighter degrees of this affection do not render a child necessarily non-viable, but with the larger some accident is likely to happen.