Bile in the blood is always dangerous, although its toxicity is much smaller than has been supposed. Of all the bile thrown out into the duodenum, we are only able to account for about one-half. Its coloring matter and biliary salts are metamorphosed. Yet in certain morbid conditions bile, as such, may be reabsorbed in the liver along the margin of the hepatic cells. In these cases, if the kidneys remain permeable, auto-intoxication is simply threatened; if they have ceased to be permeable, actual auto-intoxication is the result. _Putrefaction of intestinal contents_ affords another source of auto-intoxication. This comes both from imperfect metamorphosis of food and from bacterial infection. Here the conditions are most favorable. Nitrogenous substances become peptonized, and peptones form the best culture media for microbes. Water is present in sufficient quantities, and a constant temperature of 37° C. is maintained. The digestive tube is always open, and invaded at frequent intervals. By such mechanism are formed those products whose effects are revealed in the so-called _putrid fever of Gaspard_. Brieger has shown that alkaloids are developed during the act of peptonization. Fecal matter contains also _excretin_, whose toxicity has been amply proved, and several other alkaloidal substances, soluble in various media, varying in toxicity. The potassium and ammonium salts contribute largely to the toxicity of feces; bile also, but in lesser degree. It has been shown that the aqueous extract of putrid matter is very toxic, while that of fecal matter is otherwise. The most serious features of the conditions grouped under the heading of _Bright’s disease_ are their _so-called uremic_ features. These happen at the period when retention of toxic products is peculiarly harmful. As long as the urine is ample in amount and density--_i. e._, containing enough toxic materials in solution--there is no danger of intoxication. But when it no longer eliminates in twenty-four hours what it should, then we see the chronic and paroxysmal nervous accidents, the edemas, fluctuations of temperature, etc. Oliguria with urine of increasing density and general edema of the tissues may be noticed, although the other secretions continue natural and the tongue moist. As long as the normal amount of solids is eliminated, this form of “uremia” may be due to mere accumulation of water and may not be serious. _Ordinarily, uremic patients are those whose urine has lost its toxicity._ Usually on the day in which so-called uremic accidents happen the urine quite ceases to be toxic and is scarcely more so than distilled water. Urea alone is not to be held guilty for this condition. In order to kill a man with urea it would require the quantity which he makes in sixteen days. Nevertheless, it may become harmful after undergoing transformation into ammonium carbonate or other substances.