TUBERCULOSIS 529 



This is largely due to the fact that the temperature of the hog is so 

 variable that it is almost impossible to draw conclusions from the 

 results obtained after injection of the tubercuhn. 



The Tuberculin Test. — This is a method for diagnosis of the 

 disease by means of using an extract of the tubercle bacillus which 

 is known as tuberculin. This tuberculin is a clear yellow or amber- 

 colored liquid, and is obtained by growing the germs of tuberculosis 

 on veal bouillon and afterward kilhng the germs by heat and filtering 

 them out through a porcelain filter. The clear liquid that is ob- 

 tained contains the poisonous substances formed by the germs, but 

 does not coritain any tuberculosis germs. Some stockmen have the 

 opinion that tuberculin contains the germs of the disease, and they 

 are afraid to have it used in their herds for fear of producing 

 tuberculosis in the animals injected. There is absolutely no danger 

 of producing the disease by the injection of tuberculin. It is 

 possible, however, to light up a latent case of tuberculosis as a result 

 of the stimulus given by the toxins contained in tubercuhn. 



In the manufacture of hog-cholera serum it is very important 

 that the hogs used for purposes of obtaining serum blood should be 

 free from this disease. This has given rise to a much more exten- 

 sive use of the tuberculin test in the hog in the past five years. 

 There are two principal methods of giving the test. One method is 

 to inject the tubercuhn beneath the skin, using about I c.c. In 

 making a test in this manner the temperature is taken at two-hour 

 intervals for six hours before the injection is given, and, commenc- 

 ing about eight to ten hours after, injection temperatures are 

 again taken at two-hour intervals for several hours. A rise in the 

 temperature of more than 2 degrees is regarded as indicating the 

 presence of tuberculosis. 



This method of handling the tuberculin test is a very unhandy 

 one, and in the case of the hog is hardly ever reliable. The hog is 

 an animal that is very easily excited by handling, and especially if 

 handled by strangers or by those who do not understand manage- 

 ment of swine. As a result, the temperature will quickly rise 1, 

 2, or even 3 degrees, and it is impossible to tell in these cases 

 whether the rise in temperature is due to excitement or whether it 

 is due to reaction to the tuberculin. 



Intradermal Method. — In recent years a more satisfactory man- 



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