58 SPECIFICITY OF RICKETTSIA PROWAZEKI 



typhus) and during a further observation period of eighteen 

 days its temperature remained normal. 



Result: Guinea-pig 19, inoculated with rickettsia-infected 

 louse W 239, developed typhus apparently after an incubation 

 period of four days. The presence of typhus was proved by 

 histological examination and by subinoculations and immunity 

 tests upon three other guinea-pigs. 



Conclusion: Rickettsia-infected louse W 239 contained the 

 virus of typhus. 



Record of Guinea-pig 21, inoculated May 15th with 

 rickettsia-free louse W 240 



Guinea-pig 21 's temperature did not exceed normal limits 

 between May 15th and June 22d, a period of thirty-eight days. 

 It died June 26, following an inoculation of blood on June 22d 

 as an immunity test. The autopsy was negative. There was no 

 histological control. 



Result: Guinea-pig 21 did not develop a period of tempera- 

 ture consistent with typhus, and probably did not have typhus. 



Conclusion: Rickettsia-free louse W 240 probably did not 

 contain the virus of typhus. 



Record of Guinea-pig 22, inoculated May 15th with 

 rickettsia-infected louse W 241 



Guinea-pig 22's temperature rose on May 19th and remained 

 high (103. 5F. to 105F.), with occasional remissions of one 

 to several days until June 15th, when it remained normal until 

 June 27th, when it rose to 104 F. On June 22d it had received 

 5 c.c. of blood as an immunity test. It died July 1st and the 

 autopsy showed active pseudo-tuberculosis. 



Result: Guinea-pig 22 probably developed typhus, though 

 the course was modified by a pseudo-tuberculosis infection 

 which was probably previously latent. 



Conclusion: Louse W 241 probably contained the virus of 

 typhus. 



