336 
J. W. CONNAWAY. 
in Northern cattle, which indicates that a more active condition 
of this organ and probably of the other organs mentioned is 
maintained throughout life. 
The above facts in regard to the pathology of the disease 
and the way in which immunity is maintained, shows the im¬ 
portance of keeping an animal well nourished and seeing that 
the eliminative organs are active. 
Age of Animal —The most suitable subjects for inoculation 
are young cattle from 8 to 12 months old, weighing from 500 
lbs. to 800 lbs. They are more easily cared for than younger 
or older cattle. Calves recently taken from the cow and not 
well accustomed to a grain and hay diet do not do well; 
they fall off in flesh and do riot regain condition as rapidly as 
older, well-weaned calves. These younger calves may, however, 
be safely inoculated if kept with the cow. In August of the 
present year (1899), thirteen sucking calves, from three to 
seven months old, were inoculated on a farm near the Missouri 
Station, and all except one of the smallest calves did well 
through the inoculation fever. This lot has not yet been ex¬ 
posed to tick infestation. Our experience with animals above 
12 months of age is limited. But the fact that in the natural 
disease older animals are more liable to die, leads to the con¬ 
clusion that aged bulls and cows can not be immunized as 
successfully as those of the ages mentioned. The two-year-old 
Waskoin bulls gave good reaction from inoculation, and were 
sent south in excellent condition. Both, however, had a relapse 
in the South, and were very sick for a few days, but recovered 
and have done good service. 
Source of Blood for Inoculation .—Blood from two sources 
has been used ; namely, from naturally immune Southern 
cattle, and from Northern cattle made immune by artificial tick 
infestation, and blood inoculation. It is probable that the 
method by which an animal has been made immune can make 
no difference in the quality of the blood, since the same end is 
attained—a permanent infection. Recent observations, how¬ 
ever, have shown that the blood of different supply animals 
