germs by vaccination until it is able to fight the living ones and destroy them before they get a foothold. The diseases for which we have specific methods of treatment are few in number, and each has associated with it the name of a particular drug. Quinin kills the germ of malaria, sodium salicylate cures inflammatory rheumatism, and mercury cures syphilis. To mercury in the case of syphilis must now be added salvarsan or arsenobenzol ("606"), the substance devised by Ehrlich in 1910, which will be considered in the next chapter. The action of a specific is, of course, not infallible, but the failures are exceptional, so that one feels in attacking one of these diseases with its specific remedy as a man called upon to resist a savage beast would feel if he were armed with a powerful rifle instead of a stick. The situation in syphilis, for which there is a specific, as compared with tuberculosis, for which there is no specific, is incomparably in favor of the former. If we had as powerful weapons against tuberculosis as we have against syphilis, the disease would now be a rarity instead of the disastrous plague it is. Comparing the situation in two diseases for which we have specifics, such as syphilis and malaria, malaria has lost most of its seriousness as a problem in any part of the world, while syphilis is rampant everywhere. Malaria has, of course, been extinguished not only through the efficiency of quinin, but also through preventive measures directed at mosquitos, which are the carriers of the disease from person to person. But allowing for this, if it becomes possible to apply mercury and salvarsan as thoroughly to the prevention and treatment of syphilis as quinin can be applied to malaria, syphilis will soon be a rarity over the larger part of the civilized world. To bring the specific remedies for syphilis and the patient together constitutes, then, one of the greatest problems which confronts us in the control of the disease at the present day. MERCURY +Mercury in the Treatment of Syphilis.+--Mercury is, of course, familiar to every one, and there is nothing peculiar about the mercury used in the treatment of syphilis. The fluid metallic mercury itself may be used in the form of salves, in which the mercury is mixed with fatty substances and rubbed into the skin. Mercury can be vaporized and the vapor inhaled, and probably the efficiency of mercury when rubbed into the skin depends to no small extent on the inhalation of the vapor which is driven off by the warmth of the body. Mercury in the form of chemical salts or compounds with other substances can be given as pills or as liquid medicine. Similarly, the metal itself or some of its compounds can be injected in oil with a hypodermic needle into the muscles, and the drug absorbed in this way.