1. The susceptibility of the Henzerling strain of R. burneti to phenol, formalin, ‘Lysol’, ‘Dettol’, ‘Cetavlon’, and ether was investigated.
2. Preliminary investigation of techniques showed that, with one passage, guinea-pigs, mice and fertile hens' eggs were of similar susceptibility to small numbers of viable organisms, but the greater feasibility of sub-passage from the eggs increased the sensitivity and made this the technique of choice.
3. Under the condition of testing, ‘Lysol’ was the most active disinfectant. Treatment of the rickettsial seed with 1% ‘Lysol’ at 37° C. was in fact the only effective method for destroying completely the infectivity in 3 hr.
4. Some living organisms survived contact for 3 hr. with each of the other chemicals in concentrations up to 1%. A rough quantitative comparison of these agents was made.
5. The failure of 1% phenol to destroy R. burneti raised the possibility of this organism surviving as a contaminant in vaccine lymph. This problem was investigated and is discussed.