PATHOGENIC ANAEROBIC BACILLI. 495 



the cultures have a peculiar, acid, penetrating odor. Development 

 is most rapid at 36 to 38 C., but may occur at a temperature of 16 

 to 18 C. not lower than 14. Spores are quickly formed in cul- 

 tures kept in the incubating oven not so quickly at the room tem- 

 perature. These withstand a temperature of 80 C. maintained for 

 an hour, but are killed in five minutes by a temperature of 100 C. 

 (in steam). In the bodies of infected animals spores are not formed 

 until after the death of the animal, at the end of twenty-four to forty- 

 eight hours (Kitasato). 



The spores are destroyed by a five-per-cent solution of carbolic 

 acid in ten hours, and the bacilli, in the absence of spores, in five 

 minutes ; a 1 : 1,000 solution of mercuric chloride destroys the spores 

 in two hours (Kitasato). According to Kitasato, certain shining 

 bodies of irregular form, which stain readily with the aniline colors, 

 are to be seen in the rods as they are found in the bloody serum from 

 an animal recently dead ; but these are not spores, as some bacterio- 

 logists have supposed. 



Pathogenesis. Cattle, which are immune against malignant 

 oedema, are most subject to infection by the bacillus of symptomatic 

 anthrax, and the disease produced by this anaerobic bacillus prevails 

 almost entirely among them ; horses are not attacked spontaneously 

 i. e. , by accidental infection and when inoculated with a culture of 

 this bacillus present only a limited local reaction. Swine, dogs, rab- 

 bits, fowls, and pigeons have but slight susceptibility, but the re- 

 searches of Arloing, Cornevin, and Thomas, and of Roger show that 

 by the addition of a twenty -per-cent solution of lactic acid to a cul- 

 ture its virulence is greatly increased, and animals which have but 

 little susceptibility, like the rabbit or the mouse, succumb to such in- 

 jections ; similar results were obtained by Roger by the simultaneous 

 injection of sterilized or non-sterilized cultures of Bacillus prodigiosus 

 or of Proteus vulgaris. The guinea-pig is the most susceptible ani- 

 mal. When inoculated subcutaneously with a small quantity of a 

 pure culture, or with spores attached to a silk thread, it dies in from 

 twenty-four to thirty-six hours. At the autopsy a bloody serum is 

 found in the subcutaneous tissues in the vicinity of the point of in- 

 oculation, and the muscles present a dark-red or black appearance 

 similar to that in cattle affected with " black leg." The internal or- 

 gans present no notable pathological changes. Immediately after 

 death the bacilli are found only in the effused serum and the affected 

 tissues near the point of inoculation, but later they multiply in the 

 cadaver and are found throughout the body. According to Kitasato, 

 the cultures in solid media preserve their virulence for an indefinite 

 period, but cultures in a bouillon made from the flesh of guinea-pigs 

 soon lose their virulence. Cultures are readily attenuated by heat 



