STUDIES ON THE RELATION OF TETANUS BACILLI IN THE DIGESTIVE TRACT TO TETANUS ANTITOXIN IN THE BLOOD

1. The sera of twenty-six individuals who carried tetanus bacilli in their digestive tracts all contained appreciable amounts of antitoxin. 2. The sera of thirty individuals in whose stools no tetanus-like organisms were found were, with two exceptions, free from tetanus antitoxin. 3. Although we have been unable to measure accurately the antitoxin content of these human carriers of tetanus bacilli, 0.1 cc. of serum neutralizes 10 or more M.L.D. of toxin and it is evident that they have acquired an active immunity due to the bacilli in the intestinal tract. 4. These results definitely prove that tetanus bacilli grow in the intestinal tract of man. 5. Many of the individuals who have no tetanus bacilli in their intestinal tracts and whose serum is free from antitoxin show agglutinins to tetanus bacilli. It is probable that they have been carriers of the bacilli in the past and that the agglutinins have persisted longer than the antitoxins. It seems likely, therefore, that these individuals are potentially immune to tetanus. 6. If tetanus bacilli can be established in the digestive tract of man we have a means of immunization which might be useful in armies or in regions where tetanus infections are common, though we do not recommend this method of immunization at present.