390 BACTERIA PATHOGENIC TO MAN 



in summer, and is characterized by a peculiar emphysematous swelling 

 of the subcutaneous tissues and muscles, especially over the quarters. 



Morphology. Bacilli having rounded ends, from 0.5/^ to 0.6/> broad 

 and from 3f* to 5/^ long; mostly isolated; also occurring in pairs, joined 

 end-to-end, but never growing out into long filaments, as the anthrax 

 bacilli in culture and the bacilli of malignant oedema in the bodies 

 of animals are frequently seen to do. In the hanging drop the bacilli 

 are observed to be actively motile, and in stained preparations flagella 

 may be demonstrated surrounding the periphery. The spores are 

 elliptical in shape, usually thicker than the bacilli, lying near the middle 

 of the rods, but rather toward one extremity. This gives to the bacilli 

 containing spores a somewhat spindle shape. 



Stains with the ordinary aniline dyes, but not with Gram's method, 

 or only with difficulty and after long treatment or intense colors. 



FIG. 119 



jf V ' -\ 



. I ' ' \ ,. 



' ..-v, *H 



.1,1 // / 



1 ' '} ! u 



/ v ^ 



Bacilli of symptomatic anthrax, showing spores. (After Zettnow.) 



Biology. Like the bacillus of malignant oedema, this is a strict 

 anaerobe, and cannot be cultivated in an atmosphere in which oxygen 

 is present. It grows best under hydrogen, and does not grow under 

 carbonic acid. This bacillus develops at the room temperature in 

 the usual culture media, in the absence of oxygen, but it grows best 

 in those to which 1.5 to 2 per cent, of glucose or 5 per cent, of glycerin 

 has been added. 



GROWTH ON AGAR. The colonies on agar are somewhat more com- 

 pact than those of malignant oedema, but they also send out projec- 

 tions very often. In agar-stick cultures, in the incubator, growth occurs 

 after a day or two also some distance below the surface, and is accom- 

 panied by the production of gas and a peculiar disagreeable acid odor. 



Pathogenesis. The bacillus of symptomatic anthrax is pathogenic 

 for cattle (which are immune against malignant oedema), sheep, goats, 

 guinea-pigs, and mice; horses, asses, and white rats, when inoculated 

 with a culture of this bacillus, present only a limited reaction; and 

 rabbits, swine, dogs, cats, chickens, ducks, and pigeons are, as a rule, 



