The idea, that medicines have a kind of natural relation to disease, assumes sometimes a more definite shape than either of those to which I have alluded. Some suppose that almost all, if not all, diseases have their specific remedies and antidotes. It is often said by those who have this idea, that there are medicines in the plants that grow in any country, which can cure every disease that prevails in that country, if they could only be found. Indians and “Indian doctors” are supposed to know of many of these specifics. The newspapers announce too occasionally the discovery of specifics for the most formidable of diseases, consumption, cancers, hydrophobia, locked jaw, &c., &c. These announcements are accompanied sometimes with statements of cures of the most positive character. No doubt the statements are correct in one respect—the patients recovered. So were the wounds healed when the ointments were applied to the instruments that made them. In some way these specifics after a while lose their reputation. There is a constant succession of them, all equally infallible for the time, but the period of their infallibility is short. Their reputation is built upon the “_post hoc, propter hoc_” mode of reasoning, and therefore does not stand the test of any continued experience. In order that this subject may be fairly understood by my readers, they should know what we mean by a specific remedy. A specific remedy for a disease is one which will cure that disease under all ordinary circumstances—that is, when there are no circumstances in the case, apart from the disease, which tend to prevent the cure. Many doubt the existence of any specifics at all. If there be any, they are certainly very few in number. Sulphur and some mercurial preparations, as remedies for Psora (itch), and some other cutaneous diseases, have as strong a claim to be considered specifics as any medicines that can be mentioned. Iodine has been said to be a specific for scrofula, but it by no means holds good its claim. Though tuberculous consumption is a disease of a very definite and specific form, no specific remedy has been as yet discovered for it, and probably none will ever be, though Dr. Rush and others have indulged the pleasing hope that some plant may yet be found that will arrest the ravages of this disease. I would remark in this connection, that there is one specific preventive. I refer to vaccination as a preventive of small-pox. But this fact stands entirely _alone_—there is no other fact like it.