VI 



EXPERIMENTS TO PROVE THE SPECIFICITY OF 

 RICKETTSIA PROWAZEKI FOR TYPHUS 



THESE experiments were undertaken originally with two ob- 

 jects in view. The failure to infect all the lice with Rickettsia 

 prowazeki in boxes in which some became infected; in spite of 

 the fact that all had^qual opportunities to become infected to 

 the extent that they were equally well nurtured upon the same 

 patients made it necessary to ascertain if all or only a number of 

 the lice in such boxes acquired the virus of typhus. This was 

 the first object of these experiments. The second object was to 

 ascertain if the presence of rickettsia was essential for the 

 infectivity of the louse. 



1. METHODS 



Owing to the difficulty of feeding lice upon guinea-pigs, it 

 was decided to test their infectivity by injecting intraperi- 

 toneally into guinea-pigs emulsions of the viscera of the lice. 

 It was previously shown by Nicolle (1911, 1912), Ricketts and 

 Wilder (1910), da Rocha-Lima (1916 1 ) and others that monkeys 

 and guinea-pigs could be infected with typhus by this method; 

 da Rocha-Lima (1916 1 ) maintained with greater certainty than 

 by the injection of blood from typhus patients. Accordingly, 

 as time and guinea-pigs permitted, guinea-pigs were injected 

 with lice from a number of boxes selected at random before 

 examination for rickettsia. 



The lice were dissected with sterile instruments upon sterile 

 slides and the organs teased apart and suspended in sterile salt 

 solution. A sterile syringe was used for the injection of the ma- 

 terial from each louse. A portion of the material used for in- 

 oculation was spread upon a slide and stained with Giemsa's 

 stain for subsequent search for rickettsia. 



Forty-two guinea-pigs were inoculated (each with one louse) 

 from ten different boxes. The temperature of each guinea-pig 



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