The Inheritance of Resistance to SALMONELLA AERTRYCKE in Various Strains of Mice.

Disease resistance in animals is a field in which there has been relatively little investigation from the genetic point of view. With the development of more precise methods for laboratory control of diseases and of heredity, more critical experiments from the genetic standpoint are demanded of the animal pathologist. The experiments reported in this paper were planned to investigate the factors involved in reaction differences among various laboratory strains of mice when subjected to a controlled infection with a specific bacterial disease. Selection for resistance was the major object of the investigation using the survival of progeny as a criterion for the breeding in successive generations. Although this study was concerned exclusively with reactions inherent in mice, precedent for the general plan of investigation was drawn directly from experiments on rats conducted in the Genetics Laboratory by IRWIN (1928, 1929) and on poultry by LAMBERT and KNOX (1928). The increased resistance among rats to the Danysz bacillus observed by IRWIN over three generations of selection was attributed to complex genetic factors some of which apparently were partially dominant in inheritance. LAMBERT and KNOX, using the reaction in chicks as a basis for selection, also suggested that multiple genetic factors, in part, determine resistance to fowl typhoid. ROBERTS and CARD (1926), likewise working with chicks, showed that resistance to bacillary while diarrhea was definitely influenced by heredity. Preceding this, FRATEUR (1924) had proposed a single factor for determining resistance to avian diphtheria. Among highly inbred lines of guinea pigs, WRIGHT and LEWIS (1921) noted appreciable differences in reaction to tuberculosis. In reports dealing with bacterial infections of mice, various authors have observed individual as well as strain and stock differences in resistance. TYZZER (1917) and HAGEDOORN-LABRAND and HAGEDOORN (1920) observed that during laboratory epidemics the Japanese waltzing mouse stocks were much less resistant to infections than were other mouse stocks. PRITCHETT (1926) reported distinct differences of reaction between inbred