782 
M. R. TRUMBOWER. 
were attacked with Texas fever, and one died with all the 
symptoms of the disease in its most acute form. 
“ Another experiment was made to test the virulence of 
ticks which have developed on horses. Young ticks, the 
progeny of those which had previously conveyed Texas 
fever to cattle, were placed on two horses; in one case they 
failed to develop properly and none reached maturity, but 
from the other a sufficient number of large ticks were ob¬ 
tained to make the desired test. Neither of the horses ex¬ 
perimented with showed any signs of ill health. The progeny 
of these ticks obtained from the horse in the usual way on 
susceptible cattle yielded negative results. I do not, how¬ 
ever, regard this test as conclusive, as the ticks used had been 
kept over winter in the laborator}^ and may in this way have 
lost their virulence. 
“ The results of these experiments were the same as those 
obtained by Smith and Kilborne. Profs. Mayo and Francis 
have also experimented in a similar way and reached the 
same conclusions. It was further shown by the Bureau ex¬ 
periments that the cattle from the infected regions lost their 
power of infecting northern pastures when all the ticks had 
been carefully removed from their bodies. If we accept this 
last experiment as conclusive, it is obvious that we must re¬ 
gard the cattle tick as the exclusive agent by which the virus 
of Texas fever is conveyed to northern pastures. 
“When cattle from southern Texas fever regions are 
shipped for long distances north and set up disease in northern 
stock, it would appear from all the evidence at hand that this 
is really the case—that the tick is the exclusive intermediate 
carrier of the virus. Our experience with Texas fever in 
the South, however, does not support the statement,"one time 
advanced, of ‘ no ticks, no Texas fever.’ Northern cattle 
imported into central and southern Arkansas frequently die 
from this disease. Sometimes I have found ticks on their 
bodies in enormous numbers; sometimes very few have been 
* found, and in other cases, none at all, even with the most 
careful search. In Arkansas limited outbreaks of Texas fever 
are common every year among native cattle in many of the 
