16 BULLETIN 147, U. S. DEPARTMENT OF AGRICULTURE. 
from loss on account of the ticks. These differences emphasize the 
good results of the use of arsenical dips, and above all, of the necessity 
for the complete eradication of ticks so that the remedy, which of 
itself temporarily reduces the flow of milk, will be unnecessary. 
SUMMARY AND CONCLUSIONS. 
The cattle tick has a decidedly injurious effect upon supposedly 
immune dairy cattle, the extent of the injury being largely dependent 
upon the degree of infestation. The effect is more pronounced upon 
the milk production than upon the body weights when a sufficient 
supply of food is given. 
At the beginning of the test the tick-free and tick-infested groups 
gave practically the same amounts of milk; at the close the tick- 
infested gave only 65.8 per cent as much as the tick-free. 
The tick-free group gained 6.1 per cent in body weight; the tick- 
infested gained 3.6 per cent. 
Spraying or dipping tick-free cattle in an arsenical solution causes 
a marked though temporary decrease in milk flow. In this experi- 
ment there was an average reduction of 6.1 per cent from the normal 
milk flow for a period of five days following each of the four applica- 
tions of the arsenical solution. 
Resistance of cattle to infestation by the tick is a variable quality. 
Of the 10 animals in the tick-infested group, 4 became grossly in- 
fested; 2 more so than the average, and the remaining 4 but lightly 
infested. 
The death of cow 15, due to excessive tick infestation, and various 
recurrences of fever in the other animals, emphasizes the extreme 
hazard of cattle being continuously subjected to these losses by the 
tick. Cow 15 was one of the best of the tick-infested group and rep- 
resented at least a 10 per cent loss from the capital invested in tick- 
infested cows. Furthermore, the losses observed in this experiment 
were sustained on rations sufficient to maintain body weights. It is 
thought that had there been but a scant supply of food, as sometimes 
occurs when cows are on pasture, the tick-infested cattle would have 
suffered earlier and probably to a greater degree than they did. The 
losses in this case were in spite of a good maintenance ration. It is 
probable that much of the spring losses in cattle now laid to starva- 
tion, due to lack of pasturage, is materially aided by blood depletion 
due to ticks, and that repeated dippings would save many cattle 
otherwise lost. 
These experiments are not extensive enough to furnish an exact 
measure of the amount of decrease in milk flow due to infestation, but 
they show that the losses are considerable and vary in immune cows 
largely in proportion to the extent of infestation, since in all cases 
