Willis (1) studied the passage of tubercle bacilli from the skin to the regional lymph nodes of normal and previously infected guinea pigs and found that their spread was greatly retarded in the reinfected animals. He demonstrated the presence or absence of tubercle bacilli by simultaneous excision of the skin and lymph nodes and inoculation into other guinea pigs. Freund (2) later found a similar delay in the dissemination of living tubercle bacilli in guinea pigs previously injected with killed tubercle bacilli. He used cultural methods for the estimation of the number of tubercle bacilli in the tissues. His observations were recently confirmed by Saenz (3).

The question arises whether the retardation of spread of tubercle bacilli in the immunized animals is due to the local destruction of the organisms or to fixation at the site of injection. In the experiments of Freund and of Saenz, the skin at the site of injection was not examined.

1

This study has been aided by grants from the international Health Division of the Rockefeller Foundation, the John and Mary R. Markle Foundation and the Ophthalmological Foundation.

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