The giving of mercury by injections is a very powerful method of using the drug for the cure of syphilis. It reduces the inconvenience of effective treatment to a minimum and has all the other advantages of secrecy and convenience. It keeps the patient, moreover, in close touch with his physician and under careful observation. Injections by some methods are given daily, by others once or twice a week. The main disadvantage is the discomfort which follows each injection for a few hours. For any one who has one of the serious complications of syphilis, injections may be a life and death necessity. Mercurial injections are a difficult form of treatment and should be given only by experts and physicians who are thoroughly familiar with their use. Like every important drug in medicine, mercury is a poison if it is abused. Its earliest effect is on the mouth and teeth, and for that reason the physician, in treating syphilis by vigorous methods, has his patients give special attention to the care of their mouths and teeth and of their digestions as well. Mercury also affects the kidneys and the blood, if not properly given, and for that reason the person who is taking it must be under the care and observation of a physician from time to time. Only the ignorant undertake to treat themselves for syphilis, though how many of these there are can be inferred from the amount of patent medicine and quack treatment there is in these fields. Properly given, mercury has no harmful effects, and there is no ground whatever for the notion some people have, that mercury will do them more harm than a syphilitic infection. Improperly used, either as too much or too little, it is capable of doing great harm, not only directly, but indirectly, by making it impossible later for the patient to take enough to cure the disease. The extent to which some overconfident persons fail in their efforts to treat and cure themselves explains the necessity for such a warning.