752 INFECTION AND IMMUNITY. 



it is necessary that the secondary organisms be 

 living; when killed or when the filtrates of bouil- 

 lon cultures are used, the "pertussis bacilli" are 

 not stimulated to growth. 



Pathogen- Inoculation of pure cultures on the mucous 

 membrane of the upper respiratory passages in 

 various animals, including the monkey, does not 

 produce a pertussis-like infection. The organisms 

 have, however, a low degree of virulence for ani- 

 mals, particularly the guinea-pig. Davis found 

 that three blood-agar cultures injected intraperi- 

 toneally killed guinea-pigs in 24 hours or less. 

 The virulence of the organism is augmented wher 

 mixed with certain other bacteria. By injecting it, 

 mixed with a non-pathogenic staphylococcus, its 

 virulence, after six passages, was so increased that 

 one blood-agar culture killed guinea-pigs in 24 

 hours (Davis). In this respect, also, it resembles 

 the influenza bacillus. 



significance. Inoculated in the throat of an adult, who pre- 

 sumedly had never had whooping cough, a distinct 

 febrile reaction, lasting two or three days, devel- 

 oped after an incubation period of two days 

 (Davis). Headache and pharyngitis were accom- 

 paniments of the reaction and the pharyngitis 

 continued for at least four weeks. There was lit- 

 tle cough, and it was concluded that the micro- 

 organism had not produced whooping cough, 

 although it had shown toxic and infec- 

 tious properties. The bacillus proliferated enor- 

 mously in the pharynx and nose and was still to 

 be cultivated after four weeks. Such an organism 

 may well be an important factor in whooping 

 cough, even though it is not the essential cause. 

 Davis is inclined to regard its relation to whoop- 



