[8] A drug known as the iodid of potash (or soda) is widely used in the treatment of syphilis, and especially of the late forms of the disease, such as gummas and gummatous sores. It has a peculiar effect on gummatous tissue, causing it to melt away, so to speak, and greatly hastening the healing process. So remarkable is this effect that it gives the impression that iodids are really curing the syphilis itself. It has been shown, however, that iodids have no effect on the germs of syphilis, and therefore on the cause of the disease, although they can promote the healing of the sores in the late stages. For this reason iodids must always be used in connection with mercury or salvarsan if the disease itself is to be influenced. It is occasionally difficult to get patients to understand this after they have once taken "drops," as the medicine is often called. Otherwise the use of iodids in syphilis is of medical rather than general interest. Chapter VIII The Treatment of Syphilis (Continued) SALVARSAN +The Discovery of Salvarsan ("606").+--Salvarsan, or "606," is a chemical compound used in the modern treatment of syphilis. It was announced to the world by Paul Ehrlich, its brilliant discoverer, in December, 1910. Ehrlich and his Japanese co-worker, Hata, had some years before been impressed with the remarkable effect certain dyes had on the parasites infesting certain animals and which resemble the germs that cause the African sleeping sickness in man. When one of these dyes was dissolved and injected into the blood of the sick animal, the dye promptly picked out and killed all the parasites, but did not kill the animal. Dyes are very complex chemical substances and certain of them seem to have an affinity for germs. It occurred to Ehrlich that if a substance could be devised which was poisonous for the germ and not for the patient it might be possible to prepare a specific for a given disease, acting as quinin does in malaria. By combining a poison with a dye it might be made to pick out the germs and leave the body unharmed. [Illustration: PAUL EHRLICH [1854-1915] (From "Year Book of Skin and Venereal Diseases," 1916, vol. ix. "Practical Medicine Series," Year Book Publishers, Chicago.)]