REPORT ON DISEASES OF DOMESTIC ANIMALS. 
235 
exclusion or control of these scourges. To carry out these objects 
Congress should be asked to appropriate a sum of money, to be 
expended, as may be seen to be best, in experiments, in investi¬ 
gations, and in the control of these epidemics and epizootics. 
PLAGUES AND PARASITES PECULIAR TO THE LOWER ANIMALS. 
In turning now to the communicable disorders of the lower 
animals to which man shows no susceptibility, we face a much 
more extended class. No less than thirteen different forms of 
contagia and thirty-four different parasites exist, any of which 
may induce a prevalence that rises to the dignity of a plague. 
Among the contagia given in our list the majority are probably 
indigenous to our soil, while four are certainly exotic. Of the 
latter but one (lung plague of cattle) is known to exist at present 
in the United States, but that one more imperatively demands 
instant and effective action than all our plagues of home birth. 
Arising in this country from contagia only and having an ex¬ 
cessive incubation period (one to three months), it can be spread 
with the greatest facility by animals that carry the seeds of the 
malady but have not yet developed the disease. Having a con 
stant tendency to the death of tissue and to the encystment of 
this as a mass (infecting material), which remains unchanged for 
many months in the chests of animals that are thought to have 
recovered, it is ever liable to be spread by the apparently conva¬ 
lescent. Add to this that this contagion, if once carried to our 
Western and Southern stock-ratfges, could never be eradicated, but 
must remain as a permanent incubus and scourge as it has on the 
steppes of Russia, the open lands of Australia, and the unfenced 
ranges of Southern Africa, and we see reason why a prompt 
attention should be given to its speedy extermination. If more 
is wanted to enforce this, it is the calculation (based on the Euro¬ 
pean losses from this plague and the steady increase of our own 
herds of cattle) that this pestilence, left to itself and extended to 
our Western stock-ranges, will probably lay us under a tax of 
$130,000,000 per annum. But the flesh of animals attacked 
with this plague has never been shown to be injurious to man, 
and thus the question of its extinction is an exclusively pecuniary 
