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 20°-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 saprophyle, 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 ils 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. 
1i2 
