As briefly stated by Weil,1 a guinea-pig, by virtue of a single injection of alien protein, becomes hypersensitive toward that protein, but by frequent repetition of the same injection, becomes immune. An immunized guinea-pig, on the other hand, possesses a serum which, when injected even in minute amounts into a normal guinea-pig, renders the latter highly hypersensitive to the specific antigen in question.
Up to 1913, according to reviews of preceding literature,2 two more or less acceptable explanations of the phenomena of anaphylaxis had been advanced. The first of these hypotheses, the "cellular theory," was advanced by Ehrlich. This supposes that the cells of the body respond to the stimulus of foreign protein by the production of specific immune substances. If large quantities of these substances are produced and are thrown off by the cells into the circulation immunity occurs toward that specific protein. After a single injection