From these constantly menacing sources of intoxication man escapes by virtue of his intestinal, cutaneous, pulmonary, and renal emunctories. For instance, the usefulness of the perspiration is shown by the odor which it assumes under the influence of certain disorders. Among hypochondriacs and the inactive fatty acids are eliminated by the skin. Hence the odors of hospital wards, asylums, prisons, etc. So, too, in the case of many who suffer from deep-seated, indolent ulcers, the odor of the skin is suggestive of the presence of pus. During twenty-four hours there is eliminated from the lungs 1100 grams of carbon dioxide, water, etc., which sometimes contain ammonia and various volatile fatty acids; all of which will explain fetor of breath when it is the result of incomplete nutrition and destruction of food. Of the _organs of elimination_, the most important is the _kidney_, which does not reabsorb a part of its own products, as does the intestine. The kidneys eliminate fluids and solids, not gases. The most important of the toxic principles contained in the urine are: 1. _Urea_, which plays an important and useful role in the economy, since it possesses the property of forcing the renal barrier and removing along with itself the water in which it is dissolved and other toxic matters. Urea is toxic, but only in the sense that any other substance, even water, may be--_i. e._, it is toxic only in large doses, less than sugar, and no more than the most inoffensive salts. This is contrary to generally received views, but is established by the researches of Bouchard. 2. A _narcotic_ substance, and 3. A _sialagogue_ substance, whose composition is unknown; 4, 5. Two substances having the property of causing _convulsions_, one having the power of _contracting the pupils_. The composition of both is unknown. 6. A substance which _produces heat_ by diminishing heat production--possibly a coloring matter. That coloring matters are absorbed by charcoal and that urine thus decolorized is rendered less toxic are no proof that the coloring matters themselves are responsible for this toxic action. There is no doubt that numerous alkaloidal bodies possessing a high molecular weight are precipitated by means of carbon or charcoal, and to these bodies may be attributed a portion of that toxic action previously considered as due to coloring matters. 7. _Potassium salts_, which are really convulsing agencies, are the most toxic perhaps of any of the poisons contained in the urine. Chloride of potassium, for instance, is toxic at 18 Gm. for every kilo of animal.