1. A method for the production of tetanus by the injection of a fixed number of spores is described together with the tests made in selecting animals for experimental work.
2. Guinea pigs fed a single serological type of tetanus bacilli will, after 6 months, show considerable amounts of antitoxin in their sera and will manifest immunity to the type fed. To other types they are just as susceptible as are controls.
3. Animals fed several types are immunized to each of these types. It is pointed out in the discussion that the digestive tract of man may carry several types and that he probably reacts in a manner resembling the guinea pig carriers.
4. Guinea pigs that carry tetanus bacilli and have antitoxin in their sera show little if any resistance to tetanus toxin.
5. As there is no relation between the amount of antitoxin in the blood and immunity to tetanus we believe that other bodies, specific for type, must occur and make for the immunity observed.