450 
FRANK S. BILLINGS. 
as to become less susceptible to the virus of foot-and-mouth dis¬ 
ease. That a certain number who had previously had scarlet 
fever were attacked by the “ throat epidemic,” is not strange, for 
it sometimes happens that an individual will have two attacks of 
scarlet fever, with, in some instances, only a short interval of 
time between the attacks. On the other hand, it may be true 
that the twenty-four or more individuals who had had scarlatina, 
and escaped subsequently the sore-throat epidemic, were not sus¬ 
ceptible to the influence of the contagium which the infected milk 
contained. As is very well known, there are some persons who, 
though many times exposed to the poison of small-pox, measles, 
or scarlatina, remain unaffected by such exposure. In consider¬ 
ing the facts before us I think this truth should have its share of 
thoughtful attention. 
(To be continued.) 
THE NATURE OF THE AMERICAN SWINE PLAGUE 
IN REGARD TO ITS PREVENTIVE TREATMENT BY VETERINARY 
POLICE AND HYGIENIC METHODS. 
By Frank S. Billings, D.V.M. 
Director of the Experiment Station and Laboratory of the University of Ne¬ 
braska for the Study of Contagious and Infectious Animal Diseases. 
TRead before the Massachusetts Veterinary Association by its Secretary, Dr. L. 
H. Howard.] 
{Continued from page 414] 
Swine plague introduced or extended over the State by means 
of uncleansed and non-disinfected railroad cars or other con¬ 
veyances the property of common carriers. 
Cases of this kind are undoubtedly of common occurrence, 
though I have personal knowledge of but one, in which the disease 
first began along the line of a railroad and gradually extended 
from it. The cars were used at the time to convey rails and 
laborers, but had been used for swine previously, and their bot¬ 
toms were covered with the straw and refuse left by them, which 
was spread over the ground in unloading the cars. 
Could the authorities of the respective States be absolutely 
certain that swine purchased in other States were procured in 
