Murine typhus rickettsiae injected intraperitoneally in mice of the dba strain caused a uniformly fatal rickettsial peritonitis if the animals were kept at a room temperature ranging from 65–73°F. or from 70–80°F. With an environmental temperature range of 85–98°F., a mortality of less than 25 per cent was observed.
By utilizing different strains of mice and controlling the environmental temperature, conditions may be created under which murine typhus will have any desired degree of mortality. Such conditions have obvious advantages for the evaluation of therapeutic measures in typhus infection.