Abstract
A large number of guinea pigs were given skin tests with the filtrate of a scarlatinal streptococcus, and no reaction was observed. It was found that the animals could be sensitized in various ways so that they would then give positive reactions to the filtrate.
One group of guinea pigs was sensitized by subcutaneous injections with the filtrate; a second group was sensitized with living culture injected subcutaneously; a third group was sensitized with killed cultures subcutaneously; and a fourth group was sensitized with killed culture intracutaneously injected.
The pigs receiving the living culture were not tested until the abscesses had healed; the remaining pigs were tested on the seventh to the eleventh days after the last injection. Skin tests were made repeatedly after that time to determine the period of time that the pigs remained sensitive.
Tests made a month after the last injection showed the reaction at its peak, although some of the pigs showed good positive reactions as early as the seventh day.
The pigs showing these positive reactions to the filtrate were also given an intracutaneous injection of neutralized toxin (equal parts of filtrate and antitoxin incubated for one hour), and the tests were negative. Here we have an acquired skin reaction with filtrate that is neutralizable.
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