402 
D. £. SALMON. 
positively that their cattle have had no opportunity to contract 
the plague in the ordinary way, and that, consequently, it has 
been carried through the air or has originated spontaneously. A 
careful investigation, however, generally discovers the infected 
grounds and the cattle which have caused them, and then every 
one is surprised that that had not been thought of before. 
I mention these facts to show the necessity of the greatest 
caution in accepting explanations of outbreaks as valid which 
apparently contradict the great mass of facts bearing on this or 
any other contagious disease. 
Turning now to the outbreak in Ohio investigated by Dr. 
Miller, we find that both lots of cattle were purchased in the 
St. Louis stock-yards, and that at least one lot was repre¬ 
sented to have been purchased in Southwestern Missouri. Lot 
JS T o. 1 may have been infected when purchased in St. Louis, or, 
what is equally probable, it may have been a mixed lot of ani¬ 
mals—one or more coming from an infected district, while the 
others were from farther North and susceptible to the disease. 
They could not have all been from an infected district, for in 
that case there would have been no deaths except during the first 
week after their arrival, when exhausted by the journey. If 
none were from the infected district, and the infectio 1 was con¬ 
tracted from grounds on which they had been yarded during the 
journey, then the pasture on which they (lied would not have 
been infected. There seems to be no data whatever for deciding 
this point. 
In regard to the second lot, the impression conveyed by the 
report is that they were infected by driving lot No. 1 along the 
road adjoining their pasture. Considering that the infection has 
never been positively known to have crossed a fence, I think a 
more satisfactory explanation is possible under the circumstances. 
This lot, like the other, being purchased in the St. Louis stock- 
yard, was very likely composed of some animals from an infected 
district, and others which were from uninfected localities and con¬ 
sequently susceptible. Indeed, if all had been susceptible we 
should have expected that a larger proportion would have con¬ 
tracted the disease. The fact that they did not sicken until after 
