The property of toxin-antitoxin mixtures to produce immunity in animals has long been known. One. of us (W. H. P.) published a series of successful results in 1903. Smith suggested the attempt to immunize children, but no one undertook it until 1912, when von Behring made the attempt.
In May, 1913, Behring published the results obtained in human beings. The combined substances were either neutral or slightly toxic to the guinea-pig. Individuals were injected with small doses (from 1/20 to 1/10 c.c.) which were repeated in from seven to ten days. The first injections were made subcutaneously or intramuscularly, while later the intracutaneous administration was favored, since the more distinct local reaction was believed to induce a greater efficiency of vaccination.
The results as reported from different observers have not been uniform and as a rule are not distinctly stated. Hahn reports antitoxin production in thirty-six out of forty treated;