306 OTHER GERM DISEASES 
modes of infection, but among animals the disease is usually 
acquired through the intestine or through skin abrasions. 
In the body of the infected animals the bacilli grow with great 
rapidity. An extremely small number of them inoculated into the 
body of a sheep may produce its death in about two days, and 
after death the whole body is found to be filled with the bacilli 
in incalculable numbers. The disease is marked by a high fever 
and much discomfort, and after death the most characteristic 
symptom is a greatly swollen spleen, whence the name splenic 
fever. The spleen is large, hard, and brittle, and contains enor- 
mous numbers of the bacilli The blood-vessels are also found to 
be full of them, and the capillaries may literally be crammed with 
bacteria. 
This bacillus is extremely virulent in its action upon susceptible 
animals, so virulent, indeed, that a single bacillus, inoculated 
under the skin, may be sufficient to cause the disease and death. 
In the less susceptible animals it requires a larger dose to produce 
similar results. The lesser susceptibility of such animals as the 
dog, the horse, the bird, etc., renders them practically immune 
against spontaneous infection, and the disease occurs among them 
only as the result of artificial experiments. In man the disease is 
of rare occurrence, being practically confined to people dealing in 
or handling hides or wool, and is acquired by them either through 
abrasions in the skin, when it produces malignant pustule, or by 
breathing the spores into the lungs, when it is called wool-sorier’s 
disease. 
Preventive Inoculation.—Although anthrax is an extremely 
fatal disease to animals and has, in the past, caused heavy losses 
to agriculturists, it is a source of less loss to-day than in former 
years, since it can be fairly well controlled by preventive inocula- 
tion. We have noticed in the last chapter that Pasteur demon- 
strated the important principle of preventive inoculation by his 
experiments upon anthrax; the discovery has been of great 
practical value. Cattle can be protected from anthrax by in- 
