8 BULLETIN 147, U. S. DEPARTMENT OF AGRICULTURE. 



cow seemed to resist the effects of the ticks until toward the end of 

 the experiment, but finally failed rapidly in giving milk and died 

 within a week after the close of the experiment. 













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Fig. 1.— Cow No. 15, heavily infested with ticks over the entire body. This was one of the best cows in 

 the group, but she died of tick fever shortly after the close of the experiment. Photo taken Sept. 25, 

 1913. 



Cow 20 was infested almost as heavily as cow 15. She was a large 

 Jersey-like cow of lemon-yellow color. (Fig. 2.) Her milk failed 

 quite early in the experiment. She presented a dejected appearance 



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Fig. 2.— Cow No. 20, heavily infested on neck and shoulders. Photo taken Sept. 24, 1913. 



for some time but later recuperated and gained or held her weight 

 to the end. Externally there seemed to be no reason why ticks 

 developed so much more on her than on cow 14. 



