INFECTIOUS DISEASES OF CATTLE. 425 



THE TUBERCULIN TEST. 



The tuberculin test, which is marveloiisly accurate in its indica- 

 tions, has been almost universally adopted for the detection of tuber- 

 culosis. Tuberculin is a drug prepared by sterilizing, filtering, and 

 concentrating the liquids in which the tubercle bacillus has been 

 allowed to vegetate. It contains the cooked products of the growth 

 of these bacilli, but not the bacilli themselves. Consequently, when 

 this substance is injected under the skin of an animal it is absolutely 

 unable to produce the disease, cause abortion, or otherwise injure the 

 animal. In case the injected animal is normal there is no more effect 

 upon the system than would be expected from the injection of sterile 

 water. However, if the animal is tuberculous, a decided rise of tem- 

 perature will follow the use of tuberculin. This substance, discov- 

 ered by Koch, has the effect, when injected into the tissues of a 

 tuberculous animal, of causing a decided rise of temperature, while it 

 has no such effect upon animals free from the disease. The value of 

 tuberculin for this purpfxse was tested during the years 1890 and 1891 

 by Guttman, Eoeckl and Schiitz. Bang and Salomonsen, Lydtin, 

 Johne and Siedamgrotzky, Nocard, and many others. It was at once 

 recognized as a most remarkable and accurate method of detecting 

 tuberculosis even in the early stages and when the disease had yet 

 made but little progress. 



The tuberculin test came into existence through the most careful 

 and thorough scientific experimentation. In practice it is applied by 

 first taking the temperature of the animal to be tested, at intervals 

 of about two hours, a sufficient number of times to establish the nor- 

 mal temperature of the body under the ordinary conditions of life. 

 The proper dose of tuberculin is then injected under the skin with a 

 hypodermic syringe between 8 and 10 p. m. on the day of taking the 

 preliminary temperatures. On the following day the temperatures 

 are taken every two hours, beginning at 6 a. m. and continuing until 

 20 hours following the injection, if the fullest information is de- 

 sired.^ From average tempe«ratures calculated by De Schweinitz 

 in 1896 of about 1,600 tests of tuberculous cows, it appears that in 

 general the rise of temperature begins from five and one-half to six 

 hours after the tuberculin is injected, reaches its greatest height from 

 the sixteenth to the twentieth hours, and then gradually declines, 

 reaching the normal again by the twenty-eighth hour. 



As a result of this method an accurate diagnosis may be established 

 in over 97 per cent of the cases tested. The relatively few failures 

 in diagnoses are included among two classes of cattle. The first class 



1 The oculo-tuberculin test nnd the cuto-tuberculin test, as their names imply, consist in 

 the application of the tuberculin to the eye and to the scarified skin of the animal to 

 he tested. These methods will not be discussed at present, as they are still in the 

 experimental stage. 



