Among the most poisonous substances in the urine are the _extractive_ and _coloring materials_. Normal urine loses one-half of its toxicity by decoloration; bile acts in the same way. _Urea_ alone represents about one-eighth of the total toxicity of urine. _Ammonia_ is toxic, but present in small amounts. The _coloring matters of the urine cause two-thirds of its toxicity_, the remainder of which is to be ascribed to its mineral salts, which it contains in the following proportion: A liter of urine ordinarily contains 44 Gm. of solid matter, of which 32 are organic, 12 mineral. Of the latter, potassium salts constitute 3 Gm., sodium salts 7.5 Gm., and other earthy salts constitute the remainder. In these conditions physicians have relied largely upon purgatives, hoping thereby to remove urea from the blood. But intestinal elimination has no elective affinity for it, and removes it only in its normal proportion with the balance of the blood. Purgatives, however, help, first, by dehydrating the tissues--_i. e._, removing water with toxic material in solution. But they should be followed by restoring to the tissues pure water. By bleeding more extractives are removed than by any other channel, except by the kidneys. A bleeding of 32 Gm. removes from the body as much toxic matter as would 280 Gm. of a liquid diarrhea or 100 liters of perspiration. This much may be removed by two leeches. It is especially in the _subacute nephritis of scarlatina_, etc., _that bleeding finds its greatest indication_. If the kidneys are chronically diseased, the utility of bleeding is doubtful. Between the arterial capillaries of the bowels, however, and the liver is found a mass of blood accumulated in the _portal_ vessels. This may be regarded as a reserve which can be thrown into the general circulation when needed, in order that thereby arterial tension may be augmented and the function of the kidney increased. _Cold injections_ into the bowels will often accomplish this, and serious _anuria frequently disappears after their use_. It is advisable, also, to make use of urea by subcutaneous administration, as the most powerful diuretic known, surface friction, caffeine, digitalis, etc., being far behind it in efficiency. In the form of intoxication noted in the eclampsia of puerperal patients _inhalations of chloroform_ are valuable. Potassium salts should, under these circumstances, _never_ be employed. An exposure of urine in compressed air will diminish its toxicity, on account of contact with the oxygen; the most toxic bacteria are those which grow without oxygen. Consequently patients inhaling this gas may overcome this kind of auto-intoxication.