THE INTRADERMAL TUBERCULIN TEST. 
321 
the community he soon gets familiar with the infected herds 
and has the history of many animals which he tests to aid him in 
drawing conclusions. Without such history more errors are 
’bound to occur. 
Right here I would like to explode the fallacy of the yearly 
testing of dairy herds for tuberculosis. It seems that when the 
matter of testing dairy cattle was first discussed it popped into 
somebody’s head to test these cattle every year, and this theory 
has been blindly followed. We find in our state work that if an 
open case of tuberculosis is found in a herd, even though the 
diseased animal is promptly removed and the premises disin¬ 
fected, one or more additional animals are liable to develop 
tuberculosis within the next few weeks. There is exposure on 
the day of the test, and shortly before it, which, theoretically, 
would cause other animals to develop tuberculosis. Our ob¬ 
servation for the past twelve years shows this theory to be ab¬ 
solutely correct in many cases. We had a fine example of re¬ 
sults of an annual retest in the State Hospital herd at Farming- 
ton, Mo. In 1908 two cows reacted and were removed from 
the herd with reasonable promptness. The people in charge 
were instructed to disinfect. There is no doubt but what some 
of the other animals were probably infected upon or soon before 
the day of the test was made and did not show any reaction. 
At any rate, the test in 1909 showed five animals diseased. These 
five were shipped out a little more promptly. The test in 1910 
showed eleven of the best cows in the herd to be diseased. This 
was about what you will get with the annual tuberculin test when 
you are handling diseased herds. The results will not always be 
as bad as this, but will be in many cases. In order to clean up a 
herd in which an open case of tuberculosis is found, a retest must 
be made every sixty days, until no reactions are found and then 
again at the end of a year. Nothing short of this will be certain 
of results, so that with an annual retest of dairy herds you are 
likely to find almost as many tuberculous cattle each succeeding 
year as were found in the beginning. In the meantime the 
people who are seeking protection from tuberculous milk and 
