284 OTHER GERM DISEASES. 
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-sorter'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 inoculation. 
We have noticed in the last chapter that Pasteur demonstrated 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 inoculation, and from 
the time that Pasteur pointed out the method, hundreds of thousands 
of animals have been thus inoculated and protected. But the 
protection is not found to be very lasting, and animals must be 
inoculated about once a year to be thoroughly safe from the disease. 
This, of course, reduces the value of the inoculation, and confines 
it to localities where, for special reasons, the disease is quite common. 
It also explains why the method is not so widely in use now as at 
first; but, nevertheless, large amounts of the inoculating material 
have been used in this country as well as elsewhere, and it is thought 
that immense losses have been prevented by this means since its 
discovery by Pasteur. 
OTHER GERM DISEASES AMONG ANIMALS. 
No other diseases among animals have acquired so much interest 
as tuberculosis and anthrax, although several others are known to 
be produced by microorganisms and are of considerable importance 
