PROTOCOLS OF EXPERIMENTS 63 



has been maintained up to the present time, and on several 

 occasions guinea-pigs of this louse Box xvm strain have been 

 studied histologically, and have shown the. characteristic 

 lesions of typhus in the brains. 



Result: Guinea-pig 23, inoculated with rickettsia-infected 

 louse W 224, developed typhus after an incubation period of 

 eleven days. The infection was proved by histological exam- 

 ination and subinoculations, the strain having been carried up 

 to the present time. 



Conclusion: Rickettsia-infected louse W 224 contained the 

 virus of typhus. 



Record of Guinea-pig 16, inoculated with viscera from 

 rickettsia-free louse W 225 



The temperatures following inoculation on May 15th re- 

 mained normal. On June 22d, after an observation period of 

 thirty-eight days, this guinea-pig 16 was inoculated intra- 

 peritoneally with 5 c.c. of blood from patient 799 (eighth day 

 of typhus). 



The subsequent temperatures were as follows: 



F. F. 



June 22 No record July 5 105.8 



23 103.1 " 6 No record 



24 No record 7 105.3 



25 102.2 tf 8 104.9 



26 No record " 9 No record 



27 102.4 10 103.6 



28 No record " 11 104.1 



29 102.2 12 102.9 



30 102.4 13 102.6 



Juy 1 104.3 14 102.4 



2 No record " 15 No record 



3 103.9 u 16 102.4 



4 104.9 " 17 102.1 



July 19th; killed. The autopsy was wholly negative except 

 for fibrous adhesions in the abdominal cavity. 



Result: Rickettsia-free louse W 225 did not transmit typhus 

 to guinea-pig 16, during an observation period of thirty-eight 

 days. When inoculated with blood from a typhus patient, this 



