By violent and protracted retching, a person will sometimes become jaundiced; the stomach, diaphragm, and abdominal muscles, are, under such repeated efforts, apt to be rendered, to an eminent degree, irritable; so that at each effort of the former to discharge its contents, the latter will frequently be thrown into strong spasmodic contractions, and the liver together with the gall bladder will be suddenly caught, and, as it were, squeezed in a powerful press; in consequence of which the bile will regurgitate, and be carried into the _Venæ cavæ_; for Haller has shewn with what facility a subtle injection, when thrown into the hepatic duct, will escape by the hepatic veins; and upon which Dr. Saunders observes, “I know this to be a fact, for I have ascertained by experiment, that water injected in the same direction, will return by the veins in a full stream, though very little force be used.” When a jaundice is thus produced it will gradually disappear without the aid of any medicine; the kidneys are the principal means by which all unnecessary bodies are extracted from the circulating mass, a portion of bile will therefore under such circumstances be eliminated in every discharge of urine. The different emetics employed in practice are derived from the vegetable and mineral kingdoms, some of which appear to produce their effects by an immediate impression upon the nerves of the stomach, while others require to be absorbed into the circulation before they display their energies. _Ipecacuanha_ would seem to act primarily on the stomach, but _Tartarized Antimony_ has been found, by experiment, to occasion vomiting, when injected into the veins of an animal; while the other mineral emetics, _viz._ the preparations of _Copper_ and _Zinc_, undoubtedly operate on the stomach, and without inducing much nausea. CATHARTICS: Medicines which quicken or increase the evacuation from the intestines, or which, when given in a certain dose, occasion purging. These remedies, from a general difference in their modes of operation, have been classed under two divisions—LAXATIVES and PURGATIVES. The former operate so mildly that they merely evacuate the contents of the intestines, without occasioning any general excitement in the body, or even stimulating the exhalant vessels of the canal; the latter produce a considerable influx of fluids from these vessels, and extend their stimulant effect to the system in general; and where these effects are very violent, the purgative is further distinguished by the epithet DRASTIC. Laxatives then may be said to empty the bowels simply, and to carry off extraneous matter, which is out of the course of the circulation; but purgatives, as they occasion a constitutional effect, may be made subservient to very important purposes. The effects of a purgative may depend upon three different modes of operation; viz.