THE recent war has again shown that infections with Clostridium welchii are relatively common among battle casualties. According to Fisher and associates1 prophylactic administration of penicillin locally and intramuscularly gave satisfactory results in preventing gas bacillus infection (gas gangrene) in wounds in which it was considered most likely to develop, i. e., in dirty, lacerated wounds. In none of 4,000 consecutive battle casualties thus treated did gas bacillus infection develop. Langley and Winkelstein,2 in a study of 96 cases of gas bacillus infection of wounds at an evacuation hospital, concluded that penicillin in large doses was valuable when used in conjunction with surgical measures and antitoxin. Another war series, comprised of 33 cases of gas bacillus infection treated by local and parenteral administration of penicillin, was listed by Gledhill.3 The incidence of infection was reported to be 11 per thousand battle casualties. The use of penicillin prophylactically