182 
W. H. HARBAUGH. 
died within twenty-four hours. It was the youngest cow tha 
had the mild case. 
All of these cows were born and raised on the farm of Mr 
Grant, whose letter I have read to you. They were purchasec 
by Mr. F. and taken to his place early in the spring, and die 
well until attacked by this fever in the latter half of September 
There is one very important point on which I have not beer 
able to arrive at any conclusion whatever, and that is whethei 
or not an infected farm may in. course of time become a non' 
infected farm. 
' 
We know that Mr. Grant’s farm has ever been a non-infectec 
farm, although his cattle have ticks on them, and I know o 
farms where the disease occurs year after year when new cattk 
are placed on them, and the question that occurs to my mine 
If all cattle are kept off such a place for a certain numbei 
is 
of years, would that place become a safe place for cattle raisec 
on non-infected farms, or cattle from without the so-callec 
infected area ? 
At present I see no hope of success for preventive inocula¬ 
tion, although several experimenters thought they have reachec 
that point. 
Natural immunity is acquired by cattle born and raised or 
an infected farm. If I intended to embark in the raising o 
valuable cattle, I would begin with cattle raised on an infectec 
farm, and would buy an infected farm, and I would introduce 
more cattle from infected farms to keep my supply of infection 
as it were, and I would be certain that my place was an infectec 
place by placing on its pastures yearly, one or more cheap cows, 
from non-infected places as a test. Hence my breed of cattle 
would be insusceptible and healthy so far as this disease is con¬ 
cerned, and I would run no risk of such heavy losses as incurred 
by Col. A. These cattle would be safe to go to any infected 
farm in the South, and cattle of known immunity are needed, 
but of course they would carry destruction to non-infected 
places North or South of the line in the fever season. 
