invaded the blood brings to the breach two kinds of defenders. One is the serum which neutralizes the bacterial poison and by coagulating forms a new skin or scab over the exposed flesh. The other is the phagocytes or white corpuscles, the free lances of our corporeal militia, which attack and kill the invading bacteria. The aim of the physician then is to aid these defenders as much as possible without interfering with them. Therefore the antiseptic he is seeking is one that will assist the serum in protecting and repairing the broken tissues and will kill the hostile bacteria without killing the friendly phagocytes. Carbolic acid, the most familiar of the coal-tar antiseptics, will destroy the bacteria when it is diluted with 250 parts of water, but unfortunately it puts a stop to the fighting activities of the phagocytes when it is only half that strength, or one to 500, so it cannot destroy the infection without hindering the healing. In this search for substances that would attack a specific disease germ one of the leading investigators was Prof. Paul Ehrlich, a German physician of the Hebrew race. He found that the aniline dyes were useful for staining slides under the microscope, for they would pick out particular cells and leave others uncolored and from this starting point he worked out organic and metallic compounds which would destroy the bacteria and parasites that cause some of the most dreadful of diseases. A year after the war broke out Professor Ehrlich died while working in his laboratory on how to heal with coal-tar compounds the wounds inflicted by explosives from the same source. One of the most valuable of the aniline antiseptics employed by Ehrlich is flavine or, if the reader prefers to call it by its full name, diaminomethylacridinium chloride. Flavine, as its name implies, is a yellow dye and will kill the germs causing ordinary abscesses when in solution as dilute as one part of the dye to 200,000 parts of water, but it does not interfere with the bactericidal action of the white blood corpuscles unless the solution is 400 times as strong as this, that is one part in 500. Unlike carbolic acid and other antiseptics it is said to stimulate the serum instead of impairing its activity. Another antiseptic of the coal-tar family which has recently been brought into use by Dr. Dakin of the Rockefeller Institute is that called by European physicians chloramine-T and by American physicians chlorazene and by chemists para-toluene-sodium-sulfo-chloramide.