THE PROTECTION OF THE HERD 295 
culosts. ‘The former results practically always in the death of the 
animal, the latter may be temporary and insignificant. The for- 
mer certainly is, and the latter may or may not be, a source of 
danger to the herd. 
In the enthusiasm which followed this easy means of detection, 
it was claimed that it might be possible to eradicate tuberculosis 
completely from our herds, and some States started upon a sweep- 
ing plan of testing all cattle and slaughtering immediately all ani- 
mals that responded to the test. But this entirely too radical plan 
proved quite impracticable. Nevertheless, the use of tuberculin 
has become of great value to the farmer in his attempts to get rid of 
this disease among his cattle. 
The Preservation of a Healthy Herd.—lIf a farmer has a herd in 
which the disease has not appeared, it is of especial interest to him 
to keep his herd in this condition; for, once the disease has entered 
the herd, it is very difficult and expensive to stampit out. Tuber- 
culosis does not develop spontaneously in a herd of animals, but 
is always introduced from the outside. A farmer who can raise his 
own cattle and can properly protect them from contact with out- 
siders need have no tuberculosis among them. But to protect the 
herd requires some knowledge and great vigilance. To prevent 
the entrance of the disease into his herd from without, the farmer 
must exercise care in several directions. 
First: In buying stock he must be sure not to purchase in- 
fected animals. This is perhaps the greatest difficulty, for it is most 
commonly by purchase that the disease is introduced into a herd. 
There is only one way by which he may be sure that he is not 
purchasing infected cattle, and this is by a proper tuberculin test, 
under the guidance of a reliable veterinarian. The matter is made 
more difficult by the fact that after an animal has been tested and 
responded, she is for some time protected from a second test. A 
dishonest dealer, therefore, may inoculate his cows privately and 
then put upon the market all those that respond to the test, know- 
ing that for some time they will not again respond. One thing is 
