138 :maixe agricultural experiment station. 



never been exposed to tuberculosis. In g^lting rid of tubercu- 

 losis, we have used no means but Avhat are at the command of 

 any stock owner. In the first place, we have not harbored dis- 

 eased cattle to serve as sources of contagion. As soon as their 

 condition has been discovered, they have been destroyed. Since 

 we have relied on the action of tuberculin, many animals that 

 were doing good work and were apparently well have been sacri- 

 ficed, but the autopsy has almost invariably justified the course 

 taken, and in pursuing this course, we have doubtless saved more 

 animals than we have destroyed. We have saved animals that 

 would have become diseased if infected animals had been allowed 

 to associate with them and infect their surroundings. The ani- 

 mals destroyed had been valuable, but the most skeptical in regard 

 to the danger of bovine tuberculosis would hesitate before paying 

 much for them with a full knowledge of their diseased condition. 

 No animals have ever been sold from the College herd for any 

 purpose that were even suspected of being diseased. 



Tuberculin is not infallible by any means. Animals infected 

 with tuberculosis in which the disease is dormant, making no 

 progress for the time being, usually fail to react under the 

 tuberculin test, and again, many animals that do react are so 

 slightly diseased that it is possible or even probable that they 

 might be safely kept for some time, but we know of no way by 

 wTiich these slightly diseased cattle can be distinguished from 

 those in which the disease is more advanced, so that they 

 would not be safe animals to keep. Again, the slightly diseased 

 animal may, nobody can tell how soon, become a dangerous ani- 

 mal to have in a herd. Our obser\-ation has been that when 

 cattle have tuberculosis in a sufficiently advanced stage so that 

 it can be detected by any other than the tuberculin test, their 

 days are usually numbered, they have already done their work 

 of spreading contagion, and it matters little whether they are 

 allowed to die from disease or are killed on the verge of the 

 grave. 



In addition to getting rid of diseased cattle to avoid infection, 

 we have endeavored to get rid of the disease products that the 

 cattle haA-e left in the barns. The only active cause in 

 the spread of tuberculosis is the tubercle bacillus. This germ 

 is given off through various channels from tuberculous cattle and 



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