550 PATHOGENIC AEROBIC BACILLI 



dirty -white, moist layer. The cultures in media containing albumin 

 or gelatin have a putrefactive odor and acquire a strongly alkaline 

 reaction. A temperature of 20 to 24 C. is most favorable for the 

 growth of this bacillus. It is a facultative anaerobic and grows in 

 an atmosphere of hydrogen or of carbon dioxide, although not so 

 rapidly as in the presence of oxygen. The movements are often ex- 

 tremely active and difficult to follow under the microscope ; again 

 they may be quite deliberate, or the bacilli may remain motionless 

 for a time and again dart off in active motion. The long terminal 

 flagella may sometimes be discerned by means of a good objective 

 and careful manipulation of the light. 



Pathogenesis. Pathogenic for rabbits and for guinea-pigs when 

 injected into the circulation, into the cavity of the abdomen, or sub- 

 cutaneously in considerable quantity. Cultures in nutrient gelatin 

 are said by Cheyne to be more pathogenic (toxic) than those in bouil- 

 lon. When injected into the muscles of rabbits a much smaller 

 dose produces a fatal result than when injected subcutaneously. 

 In Cheyne's experiments, made in London (1886), one-tenth cubic 

 centimetre of a liquefied gelatin culture, injected into the dorsal 

 muscles, was invariably fatal in from twenty-four to thirty-six hours; 

 a dose of one-twentieth cubic centimetre, injected in the same way, 

 usually caused death; while one-fortieth cubic centimetre gave rise to 

 an extensive local abscess, and the animals died at the end of six or 

 eight weeks. Doses of less than one-five-hundredth cubic centimetre 

 produced no effect. Cheyne estimates that one cubic centimetre of a 

 culture in nutrient gelatin contains 4,500,000,000 bacilli, and, conse- 

 quently, that a smaller number than 9,000,000 produced no effect when 

 injected into the muscular tissue of rabbits. Injections into the sub- 

 cutaneous connective tissues of a dose twice as large as that which in- 

 variably proved fatal when injected into the muscles usually caused 

 an extensive abscess, but did not kill the animal ; and, after re- 

 covery from the effects of such an injection, the rabbit was found to 

 be immune against a similar dose injected into the muscles. Foa 

 and Bonome have succeeded in producing immunity against the 

 effects of virulent cultures of this bacillus by inoculating rabbits with 

 filtered cultures, and also by injecting beneath the skin of these ani- 

 mals a solution of neurin, which they believe to be the principal 

 toxic product present in the cultures. 



Proteus Vulgar is in Cholera Infantum. The extended re- 

 searches of Booker have led him to the conclusion that this bacillus 

 plays an important part in the production of the morbid symptoms 

 which characterize cholera infantum. Proteus vulgaris was found 

 in the alvine discharges in a considerable proportion of the cases ex- 

 amined, but was not found in the faeces of healthy infants. ' The 



