secretion of those glands, because denying it an exit. By acting on the stomach and intestines, they are able to give them tone, to diminish their secretions when excessive, and thus to promote digestion. Having premised this general view of their action, we may now proceed to prove the Proposition in which it is stated, dividing it first into four minor propositions. _m. p. 1._--That they are medicines which pass into the blood. _m. p. 2._--That they have the power of causing the contraction of muscular fibre, living or dead. _m. p. 3._--That their operation is to diminish secretion, to repress hæmorrhage, and to give tone to the muscular system. _m. p. 4._--That these results are to be accounted for by their action on muscular fibre, to which they pass from the blood. These assertions are an extension of the major proposition, but their establishment is necessary to a correct understanding of the latter. Their proof is comparatively easy and simple. It is not supposed to be a certainty; but simply to amount to a strong probability, which is as much as we have a right to expect in such cases. Astringents constitute the third class of medicines which operate on the system after being introduced into the stomach. Their action is, however, of so simple a kind, that it may be exerted on the external surface in the same way as in the interior of the body. It will be seen by a reference to the table of medicines, that the class of Astringents is there divided into two orders. ASTRINGENTIA. Ord. 1. Astringentia Mineralia. Ord. 2. Astringentia Vegetabilia. The lists of these orders are given below. With regard to the first minor proposition, it has already been proved that most of these medicines pass into the blood. The minerals included in the first order have already been noticed as Hæmatic medicines. They are all soluble in water. They are absorbed in the stomach and intestines, and pass into the blood. Many of them pass on into the secretions. The astringent parts of the vegetables of the second order are also soluble. Tannic acid is the chief of them; it is simply an Astringent; it has been found in the blood, where it changes into Gallic acid, and in that form it passes into the secretion of urine.