92 ANTHRAX 
stand how anthrax has been brought to this country and why it 
occasionally appears here and there over a large part of the continent. 
Many outbreaks, as well as isolated cases, illustrating this common 
method of dissemination are on record. 
The period of incubation is very short. In inoculated animals it 
ranges from 1 to 5 days. 
Channels of infection. Three common modes of infection are 
recognized for anthrax, namely: through the digestive tract, by the 
skin and by the lungs. In cattle the infection seems to be largely 
through the alimentary canal; in horses and sheep by the skin or 
digestive tract; in men through wounds of the skin and the respira- 
tory tract. Although these are the usual methods there are many 
exceptions with each species. 
Infection through the alimentary canal. This is the more common 
mode of infection in cattle. The resulting disease has been designated 
by various names, among which are “intestinal anthrax,” “fodder 
anthrax,” ‘“‘spontaneous anthrax,” “internal anthrax,’ “anthrax 
fever,” and anthrax without external manifestations. In these cases 
the infecting organisms, either the spores or the vegetating bacteria 
themselves, are taken into the body with food or drinking water. 
M’Fadyean has shown that infected food-stuffs are often responsible 
for the infection. It is stated that the infection takes place in most 
cases in the small intestine, the mucosa of which, it is stated, need not 
necessarily be injured. It is highly probable that the gastric juice 
destroys most of the bacteria while the free spores are not injuriously 
affected by it. In the infected districts, the spores exist at or upon 
the surface of the soil and possibly on the blades of grass, from which 
they are easily taken up by grazing animals. In lands thus infected, 
the specific organism has been introduced at some previous time either 
by the burying of anthrax animals in these fields, by the use of infected 
tannery or slaughter house refuse as fertilizers, by flooding from 
infected streams, or by the bringing of the organism in the droppings 
of birds or other small animals which have fed upon anthrax carcasses. 
It is reported that the spores will find their way to the surface even 
when the dead animals have been buried at a considerable depth. 
There has been some controversy in the writings of Pasteur, Koch and 
Bollinger concerning the method by which the spores reach the sur- 
face. Pasteur supposed that they were brought by earth worms from 
the buried carcasses. Koch believed this impossible because of the 
