Toxin-antitoxin mixture, as now made in accordance with the technic of Park1and his assistants, has proved itself remarkably free of the protein element from the clinical as well as the laboratory standpoint. A five year clinical study has proved satisfactorily the inability of toxin-antitoxin to sensitize individuals to horse protein; this conclusion is based on the following premises: A group of individuals coming to the asthma clinic of the Germantown Hospital was tested, as a routine, for susceptibility to horse protein. At the same time, a test was made on this group with toxin-antitoxin without dilution, the scratch method as well as the intracutaneous test being employed. No individuals, even those susceptible to the usual test for horse protein, gave any reaction whatever to toxin-antitoxin. One hundred were so tested, and of these 2 per cent reacted to the horse protein (H. B. W.). None of these showed