416 THE PNEUMOBACILLUS 



SECTION I. EXPERIMENTAL INOCULATION. 



Mice and guinea-pigs are very susceptible to the inoculation of virulent 

 strains of the pneumobacillus (vide infra). Rabbits are distinctly more 

 immune. 



Mice. If a few drops of a culture be inoculated sub-cutaneously into a 

 mouse they lead to the formation of an abscess containing creamy, ropy pus ; 

 the bacillus then becomes generalized and the animal dies in 1-3 days. Post 

 mortem, the spleen is enlarged and the bacillus can be isolated from the blood 

 and internal organs. Intra-pulmonary inoculation results in the formation 

 of foci of broncho-pneumonia and terminates in death. 



Guinea-pigs. Sub-cutaneous inoculation of a small dose of culture leads 

 to the formation of an abscess at the site of inoculation. Doses of 1 c.c. of 

 a broth culture prove fatal : an abscess forms at the site of inoculation and 

 death supervenes more or less rapidly with lesions of broncho-pneumonia 

 and generalization of the bacillus. 



Rabbits. A dose of several c.c. of a broth culture injected into the marginal 

 vein of the ear of a rabbit leads to the death of the animal in a few days. 

 The bacillus may be found in the blood and internal organs : lesions of 

 hsemorrhagic septicaemia are sometimes present. Sub-cutaneous inoculation 

 is followed by a less severe disease. 



Ch. Nicolle and Hebert by abrading the mucous membrane of the vulva 

 of a rabbit and infecting the abraded area produced a swelling of the labia 

 majora which was accompanied by a white discharge rich in pneumobacilli. 



Pigeons. Pigeons are only slightly susceptible. The inoculation of very 

 virulent strains into the peritoneum is however fatal. 



SECTION II. MORPHOLOGY. 

 1. Microscopical appearance. 



The pneumobacillus is a rather broad, rod-shaped organism of which the 

 length does not exceed on an average 1-2/x. Sometimes however in cultures, 

 ^ besides the cocco-bacillary forms, other long and 



even filamentous bacilli may be seen. The bacilli 

 \ are often arranged in pairs : they are non-motile 



and never form spores. 



In pus, sputum and blood, the pneumobacillus 

 has a distinct capsule. The capsule is less dis- 

 tinct, but can nevertheless be demonstrated, in 

 artificial cultures on solid media (Grimbert, 

 Nicolle and Hebert). 



Staining reactions. The pneumobacillus is 

 easily stained by the basic aniline dyes. It is 

 gram-negative. The capsules may be stained 

 Vti^thpd described in the chapter dealing 

 thionin. x iooo.) with the pneumococcus. 



2. Cultural characteristics. 



Conditions of growth. The pneumobacillus is a facultative anaerobe and 

 grows on all the ordinary media, which should be slightly acid for preference. 

 Cultures can be obtained above 15 C. ; the optimum temperature is about 

 37 C. 



Characters of growth on the ordinary media. Broth. After incubating 



