The Inheritance of Susceptibility to Yellow Fever Encephalitis in Mice.

HE importance of host resistance as a factor in determining the T incidence of infectious disease has been emphasized in recent studies. The methods developed in the study of genetics have provided a practical means of investigating the problems of host resistance and from the accumulated data there can be no doubt of the existence of heritable factors which affect the response of the individual to infection. A bibliography of the more important contributions in this field is given in a review of the subject by HILL (1934). The experiments to be reported here give evidence of the presence of such factors influencing the incidence of a virus disease, yellow fever. The susceptibility of mice to the virus of yellow fever was demonstrated by THEILER (1930). SAWYER and LLOYD (1931) tested the suitability of mice as test animals in the study of yellow fever immunity and found that different strains of mice varied in susceptibility to this virus, ranging from 100 percent to 50 percent mortality with standard dosage of virus. This information was not only of practical value in the work on yellow fever immunity, but also indicated the operation of genetic factors in yellow fever resistance. On this basis the following investigation was undertaken.