680 ANNUAL REPORT OF THE Off. Doc. 



Those are the oldest cases and they seem to be protected against 

 it. One of the objects of this experiment is to determine the length 

 of time the animal is protected. The work that we are doing is 

 along several lines. We have a number of tubercular cows and 

 the calves are being vaccinated and grow up with the cow; the 

 calf cats from the same place and drinks from the same watering 

 place and the purpose is to determine whether, under these very 

 strong exposures to the surrounding conditions, the calves can be 

 cured. These calves are perfect specimens of animal life and are in 

 good shape and smooth and slick. 



A Member: What age were they vaccinated? 



UK. PEARSON: They were vaccinated at two or three weeks 

 of age. One calf was vaccinated a day after it was born. Other 

 experiments consist in vaccinating cattle that are yearlings and 

 some that are two years old. We have a herd of thirty and twenty 

 of those are vaccinated and ten not vaccinated and they are placed 

 alternately in the stalls and thus the healthy animals are exposed 

 to those which are affected in the worst form. After a period of 

 thirty months the entire lot of thirty will be killed. From the 

 results, so far as they have been attained, there appears to be good 

 reasons to expect that the disease will be prevented in these vac- 

 cinated animals. 



MR. STOUT: Have you any knowledge of the experiments made 

 by Dr. Ravenel in transmitting tuberculosis from the animal to 

 the human system. I read in a paper not long ago about an experi- 

 ment made by Dr. Koch. 



DR. PEARSON: I do not know all about his work, because it 

 is done in connection with my own. The Koch theory you mention 

 was announced in London in 1902. At that time Koch stated he 

 believed there was very little danger in the transmission of tubercu- 

 losis from cattle to man and he based his conclusion upon this fact, 

 that he had tried to transmit the tuberculosis of man to cattle. 

 He had inoculated it on cattle and found that cattle resisted it 

 and he concluded that if cattle resisted it from human beings that 

 human beings could resist taking it from cattle. Therefore, the 

 conclusion was that human beings could resist bovine tuberculosis. 

 In Germany the Board of Health appointed a commission to sustain 

 Koch's position. Koch was an officer of that department and that 

 commission has recently reported and, among other things, it re- 

 ports this, which is extremely interesting, that under the auspices of 

 this commission the tubercular bacilli were taken from sixteen 

 children and their virus was inoculalod on cattle and four of 

 those cases the germs of the tubercular of children produced 



