CHAPTER XI. — MODE OF LIFE OF THE BACTERIA. 483 



from the intestinal canal in cases of anthrax arising from natural causes, that is, not 

 artificially produced. But to understand the life-history of the Bacillus and with it the 

 aetiology of the disease, we must first enquire how the spores find their way into the 

 intestinal canal. It cannot be directly from a diseased or lately deceased animal, 

 because the Bacillus forms its spores neither in the living creature nor inside the 

 unopened carcase \ But it is evident from what has been said on page 466, that the 

 Bacillus may not only germinate and vegetate luxuriantly outside the body of 

 the animal, but that the formation of spores takes place there almost exclusively, or 

 at least, as is proved by every culture-experiment, in the greatest abundance, if there 

 is a proper supply of oxygen and a temperature of 2o°-25°C. A sufficient further 

 supply of nutrient substances must also be presupposed, and experiment has shown 

 that these are found in abundance in every variety of dead organic bodies, and 

 not only in substances of animal origin, such as the solid and fluid parts of animals 

 themselves that have died of anthrax, or the bloody excreta of those that are ill of the 

 disease, but also in vegetable bodies in which the reactions are not too acid, such 

 as potatos, beetroot or crushed seeds, &c. It is evident from this, that the Bacillus 

 is not only able to live as a saprophyte, but that it must adopt that mode of life in 

 order to arrive at a section of its existence of the greatest importance morpho- 

 logically and biologically, namely that in which it forms its spores. It appears 

 further that it can and does readily find the necessary conditions for its vegetation 

 as a saprophyte on the surface of a moist pasture-ground, when it has once found its 

 way there, and can maintain itself there from year to year by means of its spores 

 and of the rods which dry up or are frozen in unfavourable vegetative periods; 

 it is not necessary that the place should be visited by animals. We may readily 

 conceive, how graminivorous animals liable to infection may take in the spores of the 

 Bacillus with their food in such places and become infected, for the Bacillus has the 

 capacity of parasitism. In the case of cattle that feed in herds, if one falls sick others 

 quickly take the infection and the disease becomes epidemic, because the number of 

 Bacilli on the ground is increased by the addition of those in the bloody excreta of 

 the sick animals, the pasture being thereby rendered more dangerous for the herds, 

 and because stinging flies and the like may directly inoculate one animal with the 

 Bacilli contained in the blood of another. 



It is obvious that under these conditions an animal is in greater danger of 

 infection if it has wounded surfaces whether of the skin or of the mucous membrane 

 of the mouth and digestive canal. 



Our experience with the domestic animals has taught us that anthrax is endemic 

 in certain localities, and breaks out there spontaneously, at first attacking single 

 animals, apparently without direct infection from others but usually starting from 

 the intestine, and afterwards spreading to other individuals. It is not easy to 

 explain why separate districts should thus be the favoured home of anthrax, and why 

 an organism which seems to be so capable of dissemination should not be found 

 everywhere and be everywhere alike capable of producing disease. The reason may 

 be, as Koch supposes, that the dangerous localities are wet and liable to be flooded, 

 and that the Bacillus grows more abundantly on wet ground than on dry, and is also 



1 See Koch, Mittheil. d. Reichsgesundheitsamts, I, pp. 60, 147. 



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