Studies were made on the relation of volume of inoculum to the infectivity for chick embryos of influenza virus B (Lee strain). With volumes of 0.001 to 1.024 ml, the relation between log concentration of viral nitrogen per ml of the inoculum giving the 50 per cent response and the log volume of the inoculum was linear and the slope essentially unity. Thus, independent of volume, the introduction of the same quantity of virus was required to induce infection. Since the inoculum was injected into the chorio-allantoic fluid of average constant volume, the final relation was interpreted to be a dependence of infectivity on the concentration of virus in the chorio-allantoic fluid.

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This work was aided by the Dorothy Beard Research Fund and by a grant to Duke University from Lederle Laboratories, Inc., Pearl River, N. Y.

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