122 OUTLINES OF BACTEEIOLOGY 



causing an infection of the whole body, generally with fatal results. 

 The bacilli are found everywhere in the body of the infected subject. 

 The disease occurs as an epidemic among herbivora, and though not a 

 natural affection in man, may be passed over to him from animals 

 either directly or indirectly. A drop of blood taken from a cow which 

 has died of anthrax will show a number of non-motile large rods 

 (Fig. 75). The ends of the rods are somewhat rectangular, not gently 

 rounded off as are most bacterial rods. Each rod is about r2 /* in 

 width and about 6 /x in length, so that its size is above the average. 

 ^^ The cultures of this species on gela- 



^^^^^^ tine- and agar-plates, in stab-tubes, 



^^^■^^^^^^ etc., have such well-defined charac- 

 teristics, that, taken with its micro- 



FlQ. 76.— Bao. anthracis. -it • . i • • 



scopical characteristics, the species is 

 not diflBcult to identify. Unlike those which we have previously 

 dealt with, this species forms spores abundantly, hence their resistance 

 to heat and antiseptics is considerable, being much greater than that 

 of any of the othief pathogenic bacteria. 



This bacillus finds a ready host in cattle, sheep, guinea-pigs, mice 

 and white rats. On the contrary, flesh-eating animals (dogs, cats, etc.) 

 are practically immune, and the same can be said of birds and of 

 animals belonging to the same group as the frog. Man occupies an 

 intermediate position, so far as susceptibility to this disease is con- 

 cerned, between the highly susceptible and the highly immune 

 creatures. This disease usually appears among those who habitually 

 handle the skins or the carcases of animals. The spores of diseased 

 animals enter the human system through cuts or abrasions of the skin 

 or through the hair follicles, or perhaps by being inhaled, for highly 

 susceptible animals can be infected by being made to inhale the germs. 

 Once inside the body the microbe spreads everywhere, and its toxins 

 are secreted throughout the whole body. 



Now, with regard to the mode in which these bacteria are spread, 

 an animal suffering from anthrax sheds into the air by bloody excre- 

 tions from the bowels, mouth and nose a large number of microbes 

 belonging to Bac. anthracis. These will probably form spores if they 

 do not at once find a nutritive medium. In the spore condition they 

 can remain alive for years. If they come in contact with a favourable 

 medium the spores germinate, and in this way many millions more are 

 produced. As this microbe is not only parasitic on animals, but also 

 saprophytic on various organic matters in the soil, its chances of con- 

 tinued existence are very considerable. Naturally, also, the carcases 



