_Lesions._ In the early stages the mucosa of the pelvis is congested, red, and sometimes, with calculus, hæmorrhagic. Later it becomes thickened by exudate, which fills also the submucous tissue. In some instances the pelvis is distended by an impacted calculus, in others the obstruction of the ureter by an impacted calculus or a swelling has led to overdistension of the pelvis, and ammoniacal fermentation of its contents. Coincident inflammatory lesions of the kidney, ureter, or bladder are common. _Prognosis_ is not hopeful. Where it has resulted as a descending infection from the kidney, the severity of the primary lesion renders the case a grave one, while if it has been an ascending inflammation from the bladder it is no less so. _Treatment._ Diluent (watery) diuretics are especially indicated. Pure water may be given _ad libitum_. To this may be added if necessary moderate doses of bicarbonate of soda or potash with such non-irritating antiseptics as salicylic acid, salicylate of soda, sulphite of soda, sulphide of calcium, quinia or chamomile. Trasbot even recommends small doses of vegetable astringents, balsam of Tolu, or Peru or of Copiaba, or oil of turpentine or tar water. Apart from simple water, the diuretic agents may be used with greater freedom if the solid parts of the kidney are little or not at all involved and if the urine contains no casts of the uriniferous tubes. Benefit may also be obtained from fomentations, or cupping of the loins, and even from the application of mustard and counter-irritants. If the active symptoms subside the continued use of tonics would be indicated, especially quinia, and also of the balsams with the view at once of antisepsis and toning up of the mucous membrane. In case of calculus of the pelvis surgical extraction is virtually the only resort, though a very desperate one. Its increase may be retarded or prevented by antisepsis, a liberal use of water, and the exhibition of piperazin or some of the essential oils. CHRONIC NEPHRITIS.