Tuberculosis. 115 



raise healthy calves from diseased mothers, by what is 

 known as the Bang system, which will be described later. 



Infection of the herd. The most frequent way in 

 which the disease is introduced into a herd is by the 

 purchase of a tuberculous animal. The larger the 

 number of animals purchased, the more likely is the 

 disease to be introduced. The animal purchased may 

 appear healthy and may not at the moment be a source 

 of danger, but is certain in time to become a center 

 from which the disease will spread throughout the herd. 

 As was stated, pure-bred herds are often diseased. All 

 too often has a man introduced the disease into his herd 

 through his efforts to improve his stock by the purchase 

 of a pure-bred sire. 



The farmer should know the condition of every 

 animal he buys. He will use great precaution to avoid 

 buying an unsound horse, but the purchase of such an 

 animal is not to be compared so far as probable future 

 loss is concerned, to the purchase of a tuberculous cow, 

 for the trouble from which the horse suffers is not likely 

 to spread, while tuberculosis will surely infect others. 



Buy pure-bred animals from honest breeders whose 

 herds are "known to be free from tuberculosis and from 

 no others, even though they will guarantee the condition 

 of the animals. 



The feeding of creamery skim milk and of whey is 

 another- potent means of introducing the disease into the 

 herd. The patron of a creamery or cheese factory 

 carries to his calves and hogs a mixture of the milk of 

 all the other patrons. In case there are tuberculous cows 

 in any of the herds, the milk may contain tubercle 

 bacilli. The farmer can protect his herd from such in- 

 fection by the use of a farm separator, or by heating 



