The bloods of three persons (G. M. F., A. E. G., and C. H.) who were infected in 1931-1932 (Find]ay 1932) have been avai lable for s tudy in order to de termine the dura t ion of immune bodies. I m m u n i t y tests were made by mixing 1 vo lume of the var ious dilutions of infected mouse blood in saline wi th 1 vo lume of i m m u n e serum. The mixtures were placed in the ice chest for two hours at 4 ~ C. and then inocula ted intraper i toneMly into groups of 4 mice, each mouse receiving 0.2 ml. of one di lut ion of the m i x t u r e : as a control, similar dilutions of infected mouse blood were mixed wi th normal rabbi t serum. The mice were observed for 10 days. The results are shown in Table I.