The survival of vaccine virus when incubated on the opposite side of a collodion membrane from a suspension of fresh minced rabbit kidney was not complete in these experiments, and passage in series was not successful. The degree of survival seemed somewhat greater if dead cells, killed by repeated freezing and thawing, were added to the virus during incubation, although the tissue was able to increase the intensity of the skin reactions. Extracts of dead kidney cells did not increase the degree of survival, as determined by the intensity of the skin reaction. No significant or constant increase in the intensity of the skin reactions resulted from the addition of cysteine hydrochloride to the virus in the dialyzing apparatus.

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