1. Collodion particles adsorb diphtheria or tetanus or botulinus toxins. These toxins are retained on the particles when washed but are at least in part released in the animal. 2. The adsorbed toxins are neutralized by adsorption of the corresponding antitoxins but are unaffected by other serums. 3. When collodion particles are treated first with tetanus antitoxin, then with diphtheria toxin, they are not toxic, but they become toxic when they are treated first with diphtheria antitoxin, then with the diphtheria toxin. Similarly when collodion particles are treated first with diphtheria antitoxin and then with tetanus toxin, they do not become toxic, but they become toxic when they are treated with tetanus antitoxin and tetanus toxin.