Thus Antimony, Mercury, Acids, Alkalies, Sulphur, the Salts, etc., are Hæmatics primarily. The various volatile oils and resins are more or less Stimulants. So also Alcohol and Ether, as well as Camphor and others, are found among Narcotics. Colchicum, Digitalis, Creosote, and Ipecacuanha, are Sedatives. Many Eliminatives are certainly known to pass into the blood, because they are subsequently found in the secretions, as will be presently seen. Secondly, these medicines cannot remain in the blood, but must sooner or later leave it. If they remained, they could not pass through the glandular cells. But if they pass out, they must inevitably be excreted by them. All those medicines must be secreted which have nothing in the natural blood corresponding to them. This is the case with most Eliminatives, and with all medicines except the Restorative Hæmatics. And those Restoratives which act as Eliminatives, such as Acids and Alkalies, do so because they are introduced in so large a quantity that they cannot possibly remain in healthy blood. Thus all these medicines pass out through the glands. Thirdly, we find that in so doing they tend to pass out by some particular glands rather than by others. In order to show this we may consider first the chief tendencies of the great groups of Eliminative medicines; and secondly, I shall endeavour, when considering the six orders, to show that many of the medicines included in them have actually been found in the secretions of the glands towards which they tend. The first consideration will clear the way for the second. What we have to ascertain is, that the principle of selective secretion is generally applicable to Eliminative remedies. The most important of the substances which are used to increase secretion may be divided chemically under the following six heads, of all of which it has been proved that they are capable of absorption. (Prop. II.) 1. Insoluble mineral substances. 2. Soluble minerals,--_i.e._ Acids, Alkalies, and Salts. 3. Ammonia and volatile oils. 4. Fixed acrid oils. 5. Resins and neutral acrid principles. 6. Soluble vegetable principles. 1. _Insoluble mineral substances._--The chief of these are Mercurials (Blue Pill and Calomel,) Iodine, and Sulphur. They are all more or less changed during the process of absorption, as they have to be reduced to a soluble condition. They stimulate secretion generally; but Mercury particularly tends to the liver, bowels, salivary glands, and skin; Iodine, to the kidneys, and to the salivary and mucous glands; Sulphur, to the skin.