4 BULLETIN 584, U. S. DEPAETMENT OF AGRICULTURE. 
the cost must be considered. An army of thousands of employees 
would be required, millions of dollars would be needed for the reim- 
bursement of owners, and the interference with the hog industry of 
the country would be so great that any such campaign for the eradi- 
cation of hog cholera instead of proving a boon might come to be 
regarded by the hog raisers of the country as a calamity. 
With the above ideas in mind, the United States Bureau of Animal 
Industry has given much study to the development of some practical 
working plan for controlling losses from hog cholera. With this 
object in view, laboratory researches and field experiments have been 
continuously prosecuted for a number of years. 
THE SERUM METHOD OF CONTROL. 
As early as 1904 the Bureau of Animal Industry announced the 
discovery of a serum which would protect hogs against cholera. 
Work was continued, and in 1908 representatives of the various 
States were made acquainted with the methods of producing this 
serum, with the hope that its widespread application might serve to 
accomplish what it seemed unwise to undertake through methods of 
rigid quarantine and slaughter. This anti-hog-cholera serum grad- 
ually came into general use, and the original statements as to its 
efficaciousness were thoroughly substantiated by successful use in 
practice. 
The development of this serum afforded a new weapon for attack- 
ing hog cholera and gave rise to the hope that it might be employed 
at least to reduce losses and perhaps ultimately to eradicate the 
disease. 
In 1908 a plan for the employment of serum in control work was 
suggested by one of the writers (Melvin) in an article in the Twenty- 
fifth Annual Eeport of the Bureau of Animal Industry. This plan 
embodied the following features : 
1. Division of a State into districts. 
2. An adequate supply of serum. 
3. Prompt notification of outbreaks. 
4. Quarantine and disinfection of infected premises. 
5. Prompt treatment of infected herds with serum. 
6. Immunization of neighboring herds by inoculation with serum 
and virus (simultaneous inoculation). 
This plan seemed to possess many advantages over the method of 
quarantine and slaughter. If properly carried out. a large propor- 
tion of each infected herd should be saved and become exceptionally 
valuable on account of the immunity which would be established. 
The business of the farmer would not be seriously interfered with, 
