BACTERIOLOGY OF WHOOPING-COUGH 21 



anatomical change visible, this latter result was attributed to the 

 toxic products surely a most doubtful conclusion. In rabbits, by 

 intravenous inoculation of living bacilli, dyspnea and marked weak- 

 ness were produced, which PfeifTer also attributes to toxins, because 

 the same result was produced with dead bacilli. Kolle and Delius 

 substantiated these results, and also showed that influenza bacilli 

 would develop in the peritoneal cavity of animals, especially guinea- 

 pigs. The exudate contained many bacilli, partly free and partly 

 in the cells. They were able to raise the virulence of the bacilli by 

 successive animal inoculations, and in nitrates of cultures obtained 

 a specific but very labile poison. Jacobson 1 increased the virulence 

 of the influenza organism by simultaneous injection with streptococci, 

 and Slatineano 2 raised the virulence by injecting lactic acid at first 

 and one-half hour later the influenza bacilli. 



Experiments on lower animals. The influenza-like bacilli isolated 

 from the whooping-cough patients in this series showed on the whole 

 a low degree of virulence for animals; however, some very definite 

 results were obtained. Guinea-pigs were found most satisfactory for 

 this purpose. White rats are susceptible, but less so than guinea-pigs; 

 rabbits, especially young ones, are also susceptible when inoculated 

 intraperitoneally. But few inoculations were made in these animals, 

 however. Two blood-agar cultures inoculated intraperitoneally into 

 guinea-pigs will rarely kill in 24 hours. Usually the animal is sick the 

 next day after inoculation, but will gradually recover. If the amount 

 is increased, death will usually occur in 24 hours or less, and from the 

 peritoneal cavity, pleural cavity, and heart's blood, the bacilli are 

 obtained in abundance. In the blood the bacilli are so numerous at 

 times that they may be found without great difficulty in smear. A 

 few drops, allowed to run over the surface of an agar slant, usually 

 shows an abundance of colonies in 24 hours. Blood removed from 

 the heart before death also shows the presence of bacilli, so that their 

 occurrence is not due to a postmortem invasion, but there seems to 

 be an actual multiplication of them in the living blood. 



When the animal dies in 24 hours or thereabouts after inoculation 

 into the peritoneal cavity, the peritoneal and pleural exudates are 

 clear, serous in character, and soon clot on standing. The bacilli 



1 Archiv de mid. exptr., 1901, 13, p. 425. 



Comp. rend, de la Soc. de Biol., 1901, 51, p. 850 



