THE DIPHTHERIA TOXIN SKIN REACTION

The great advantages gained by a prompt recognition of individual susceptibility or immunity to diphtheria are beyond dispute. The principles underlying the methods by means of which this information is gained have long been known. The actual technic of these methods has been repeatedly changed and simplified. Romer injected intradermally into a guinea-pig a definite minute amount of diphtheria toxin mixed with a definite amount of the serum which was to be tested for antitoxin. If the tested serum did not contain an amount of antitoxin sufficient to neutralize the amount of toxin injected, necrosis occurred. This method was far too complicated for ordinary clinical purposes. In 1909, Schick published a more practical technic. One fiftieth of the minimal lethal dose (for a 250 gm. guinea-pig) of diphtheria toxin diluted in normal saline solution is injected intradermally into the patient's forearm. This method requires accurate measuring of the toxin and