142 BACTERIA 



aureus, it increases more luxuriantly (symbiosis). It is probable 

 that the cocci, in some way, alter the blood of the culture media. 



Vitality. It is easily killed by light, heat and drying. Lives 

 but a day in distilled water, and from eight to twenty-four hours in 

 dried sputum. 



Habitat. Never outside the body; always a strict parasite. It 

 is found in the mucous membranes of the upper respiratory tract, 

 and in the mucous secretions. 



Pathogenesis. If pure cultures are placed on the mucous sur- 

 faces of monkeys, influenza results. Pure cultures injected into the 

 peritoneum of guinea pigs cause fatal peritonitis. In man, it causes 

 various affections of the upper respiratory tract bronchitis, pneu- 



FIG. 44. Pest Bacilli from spleen of rat. (Kolle and Wassermann.) 



monia, both croupous and catarrhal. Also conjunctivitis. It elab- 

 orates a powerful toxin, which produces strongly depressing effects 

 on certain organs, especially nervous tissues. It is an important 

 factor in abscess production in the middle ear, and elsewhere, and 

 complicates many pneumonia cases, seriously interfering with 

 recovery in young children, and the aged. Associated with the 

 pneumococcus, its toxic effect is increased. It has been found in the 

 blood. 



