An ovarian cyst is more manifestly attached to the pelvis, and its history will disclose the fact of its having arisen from below. A gravid uterus should also, when small, be manifestly connected with the pelvis, and when larger be accompanied by the usual symptoms of pregnancy. The same may be said of extra-uterine pregnancy, which may be mentioned as among the conditions possibly giving rise to difficulties in diagnosis. The most efficient aid to diagnosis, when it is of importance that such should be accurately made, is the aspirator-needle, which will procure a fluid more or less characteristic of the tumor into which it is thrust. In hydro-nephrosis the contents are a somewhat dilute urine, with perhaps mucus; in a solid tumor, blood, with pieces of tissue recognizable by the microscope; in a cystic tumor, fluid which is perhaps somewhat urinous, but much more changed than in simple hydro-nephrosis, and perhaps containing solid-looking bodies with concentric and radiating striation; in hydatid cysts, hooks and fragments of scolices; in ovarian cysts, the various contents, fluid and semi-fluid, but not urinous, generally found therein. With all these means, however, cases will occasionally arise in which expert diagnosticians may be lead astray, and the difficulties become considerably greater when the dilated pelvis is that of a displaced or unusually-placed kidney. Such cases have been subjected to operation under the impression that an ovarian cyst was present. The medical TREATMENT of hydro-nephrosis is nil. In many cases nothing is demanded by the immediate necessities of the case, and atrophy, if it be probable that only one kidney is involved, may be allowed to take place without interference. It is possible that in some instances manipulation of the tumor might relieve the obstruction and allow the tumor to subside when a slight twist or angle in the ureter is the cause. The fact of an occasional spontaneous subsidence of such a tumor shows that something of this kind has taken place. {60} The surgical treatment of affections of the lower urinary passages, as both a prophylactic and therapeutic measure, has already been spoken of under the head of Pyelitis. It would, however, be only in a minority of cases of pure hydro-nephrosis that the seat of obstruction could be efficiently reached by surgery. Puncture and aspiration of the sac may very properly be resorted to, and may prove of value--in the first place, as a more or less temporary relief; and secondly, as a means of re-establishing the flow through the natural passages by the relief of pressure and consequent opening of the valvular fold, which has occasionally been observed at the junction of the ureter with the pelvis.