A very important point in diagnosis, especially when the question of operative procedure arises, is that of the soundness of the other kidney. Accidental circumstances will sometimes permit this to be determined; as, for instance, when one ureter is suddenly blocked by a calculus, and at the same time the urine, which has previously been found purulent, bloody, and containing renal cells and casts, becomes clear and normal until the obstruction is removed and the abnormal ingredients reappear. Cases of exstrophied bladder, where of course it is possible easily to separate the urine of the two kidneys, may be, from their rarity, practically left out of the account. Various proposals for obtaining the separate urine of the two kidneys have been made. A small catheter has been passed into the female ureter through the dilated urethra. In the female also a finger in the vagina may succeed in temporarily blocking one ureter, while the secretion of the other alone is filling the bladder, a catheter with a bent portion at the end being used for making counter-pressure from the inside. It would probably remain doubtful in most cases how successful this manoeuvre had been in completely stopping the flow of urine, although experiments upon the dead body have been made by Polk,[18] who proposes the method, with entire success. The male bladder offers greater difficulties, which are at present insurmountable. A point opposite the lower end of the ureter can, it is true, be reached with some difficulty in the rectum, and it is possible that a catheter might be so adjusted as to make counter-pressure to the finger in this position, but there could be no certainty that the occlusion was complete. [Footnote 18: _New York Med. Journ._, Feb. 17, 1883.] The whole hand in the rectum, after Simon's method, would enable the object to be accomplished with more certainty, but this procedure has risks of its own. A staff with flattened extremity, as suggested by Weir,[19] may more conveniently, though with somewhat less certainty, be used for pressing from within the rectum on the ureter where it passes over the brim of the pelvis. A compressorium consisting of an empty and folded bag, to be introduced into the bladder and there expanded by the introduction of metallic mercury, has been described and used, with the result of partly checking the flow of urine.[20] The proposition to pinch up the extremity of one ureter in the bladder by means of the lithotrite is still {51} more open to the objection of great uncertainty, and would, to say the least, demand very special skill to obtain even a chance of success. [Footnote 19: _Ibid._, Dec. 27, 1884.] [Footnote 20: See Weir's article, just quoted.]