TUBERCULOSIS. 417 



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 w411 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 purpose 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 desired.^ 

 From average temperatures, 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, reach- 

 ing the normal again by the twenty-eighth hour. 



As a result of this method an accurate diagnosis may be estab- 

 lished in more than 97 per cent of the cases tested. The relatively 

 few failures in diagnoses are included among two classes of cattle. 

 The first class contains those that are tuberculous, but which do 

 not react either because of the slight effect of an ordinary-sized 

 dose of tuberculin on an advanced case of the disease w^th so much 

 natural tuberculin already in the system, or on account of a recent 

 previous test with tuberculin which produces a tolerance to this 

 material, lasting for about six weeks. The second class includes 



iThe ophthalmic-tuberculin test and the intradermal-tuberculin test, as their names 

 imply, consist in the application of the tuberculin to the eye and to the deep layer of the 

 skin of the animal to be tested. These methods will not be discussed at present, as they 

 are still in the experimental stage. 



33071°— IG 27 



