The experimental evidence of the protective character of formolized botulinum toxoids A, B and C is demonstrable. Five-tenths per cent of formalin added to potent botulinum toxins A and B containing 10,000 guinea pig lethal doses per cubic centimeter detoxified the toxins at 37°C. in varying periods of time. Larger amounts of formalin seemed undesirable, while 0.3 per cent of formalin failed to kill the Cl. botulinum spores A and B, but did detoxify weak toxins containing 4000 guinea pig lethal doses per cubic centimeter and kill type C spores.Potent toxoids protected a majority of guinea pigs, yet guinea pigs of 300 grams weight or slightly over more consistently withstood lethal amounts of unaltered toxin than pigs weighing less than 300 grams. In evaluating the antigenic value of botulinum toxoids in guinea pigs at least 3 of 4 pigs injected with appropriate doses of potent toxoid should survive lethal amounts of toxin. Three units administered subcutaneously to guinea pigs of 300 grams weight should also prove innocuous. Protective amounts of toxoid have been injected into fowls and horses without ill effects, suggesting that there is a desirable range of safety in this antigen in studying its immunizing value in the field.The value of combined toxoids in one, two or three doses administered at weekly intervals against a single or a combined homologous toxin is suggested, but its effect in natural outbreaks of botulism in animals under farm conditions receiving contaminated rations remains to be established. The experimental evidence suggests that it may protect against lethal amounts of the toxin.
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