Biological Papers. I47 



farmer, consumer and the entire country, but it likewise 

 yields an immense profit to all. 



Tuberculosis seldom dies out spontaneously from a farm. 

 It is only by the act of man that such a thing occurs. If all 

 other present conditions remain the same and nothing is done 

 concerning tuberculosis, the present less than six per cent, 

 will soon become more than seven per cent., and then eight 

 per cent., and so on, for tuberculosis spreads from tuberculous 

 animals on one farm to the previously healthful animals on 

 another farm by two methods only. First, either at public 

 auction or private sale tuberculous animals are bought con- 

 sciously, or, more frequently, unconsciously, and placed in 

 previously healthful quarters and among previously healthful 

 animals, and with the very same disastrous results from the 

 association explained heretofore. Secondly, by the food prod- 

 ucts, especially milk of tuberculous cows on one or more farms 

 being taken to the local creamery and mixed with the entire 

 skim-milk product of the creamery. . Thus all the farmers 

 hauling back this skim-milk carry infection to their own hogs, 

 the majority of which were previously healthful. Thus new 

 source-centers are started, ^and just as a few years ago we 

 could probably say less than four per cent, of the farms had 

 tuberculous animals upon them, in a few more years we can- 

 not even say less than six per cent. Each of the present six 

 per cent, of farms will become more saturated with the dis- 

 ease. Thus the percentage of tuberculous animals on the 

 farms will increase above six per cent, and the per cent, of 

 farms will increase. 



Let me relate what we have suffered and lost in not adopt- 

 ing my plan June 30, 1906, seventeen months ago, when the 

 famous meat-inspection bill became a law. 



Since that time nearly, and probably, every farmer in the 

 country has marketed one or more hogs, several hundred thou- 

 sand of them being tuberculous. Had the hogs been tagged 

 we would to-day know where practically every tuberculous 

 animal in the country is now located. Conversely we would 

 know nearly every animal that was free from tuberculosis. 



Since that time, tuberculous animals that would be either 

 dead or under control to-day have been bought, are being 

 bought, and will be bought at private and public sales, and 

 have been taken to healthful farms and among healthy cattle. 



Since that time, tuberculous animals that would be either 



