+Misconceptions Concerning Mercury.+--The use of mercury in syphilis is nearly as old, in Europe at least, as the disease itself. The drug was in common use in the fifteenth century for other conditions, and was promptly tried in the new and terrible disease as it spread over Europe, with remarkable results. But doses in the old days were anything but homeopathic, and overdoses of mercury did so much damage that for a time the drug fell into undeserved disfavor. Many of the superstitions and popular notions about mercury originated at this period in its history. It was supposed to make the bones "rot" and the teeth fall out, an idea which one patient in every ten still entertains and offers as an objection when told he must take mercury. Insufficiently treated syphilis is, of course, what makes the bones "rot," and not the mercury used in treating the disease. Mercury apparently has no effect on the bones whatever. The influence of the drug on the teeth is more direct and refers to the symptoms caused by overdoses. No physician who knows his business ever gives mercury at the present time to the point where the teeth are in any danger of falling out. +The Action of Mercury.+--The action of mercury on syphilis is not entirely clear. The probabilities are that the drug, carried to all parts of the body by the blood, helps to build up the body's resistance and stimulates it to produce substances which kill the germs. In addition, of course, it kills the germs by its own poisonous qualities. Its action is somewhat slow, and it is even possible for syphilitic sores containing the germs to appear, especially in the mouth and throat and about the genitals, while the person is taking mercury. Just as quinin must be used in malaria for some time after all signs of chill and fever have disappeared, to kill off all germs lurking in out-of-the-way corners of the body, or especially resistant to the drug, so it is necessary to continue the use of mercury long after it has disposed of all the obvious signs of the disease, like the eruption, headaches, and other symptoms, in order to prevent a relapse. No matter in what form it is used, the action of mercury on syphilis is one of the marvels of medicine. It can clear up the most terrific eruption with scarcely a scar, and transform a bed-ridden patient into a seemingly healthy man or woman, able to work, in the course of a few weeks or months. Symptoms often vanish before it like snow in a thaw. This naturally makes a decided impression, and often an unfavorable one, on the patient. It is only too easy to think that a disease which vanishes under the magic influence of a few pills is a trifle, and that outwardly cured means the same thing as inwardly cured. Mercury therefore carries its disadvantages with its advantages, and by its marvelous but transient effect only too often gives the patient a false idea of his progress toward cure.