366 AGRICULTURAL BACTERIOLOGY. 



Second : He must prevent his cattle from associating with 

 strange cattle. If put out to pasture they must be kept by 

 themselves and guarded against chance contact with strangers. 

 Common watering troughs, in which miscellaneous cattle are 

 watered, must be shunned. 



Third : He must not feed his calves upon milk from other 

 herds. The way in which this is most commonly done is by 

 the use of skim milk returned from a creamery or a separating 

 station. From such a creamery the farmer does not get back 

 his own milk, but always milk from another source, and, 

 if there be a few cases of bovine tuberculosis of the udder in 

 the neighborhood, the bacilli from these animals will inevi- 

 tably soon be distributed, through the separating station, over 

 the whole region contributing to the station. This is not mere 

 theory but positively ascertained fact. To such milk is to be 

 attributed the large amount of tuberculosis among swine in 

 recent years, and it is a well-accepted fact that the mixed milk 

 from such separating stations is one of the most prolific 

 sources of distribution of tuberculosis among calves. The 

 only safe procedure is for the farmer either to bring up his 

 calves upon the milk from his own healthy herd, or to insist 

 that all milk fed to them shall be first subjected to the process 

 of pasteurization or boiling. So convinced have the agricul- 

 turists in Denmark become that this mixed milk is the cause 

 of a large amount of bovine tuberculosis, that there has been 

 passed a law forcing the pasteurization of all milk which is 

 thus brought to creameries for separation of the cream. The 

 farmer is thus protected from the tuberculosis of his neighbors' 

 herds. The farmer's herd cannot long be maintained in a 

 healthy condition if its calves are fed upon the uncooked 

 mixed milk which is returned from a creamery. The feeding 

 of such milk to hogs is nearly as injurious, for, apart from its 

 producing the disease among swine, it will almost inevitably 

 happen that, once on the farm and in the pig pen, the disease 

 will spread to the cow stall. 



