Subcutaneous Tuberculin Test. 577 



the reaction or of the post-mortem findings, or possibly also 

 on mistakes in conducting the test. 



Tuberculin is therefore an extremely valuable diagnostic 

 agent, especially in the detection of latent tuberculosis. A 

 positive reaction to the tuberculin test is a certain indication 

 of the existence of tuberculosis while the absence of a positive 

 reaction justifies the exclusion of latent tuberculosis. 



In interpreting a tuberculin reaction the following prin- 

 ciples are safe to follow (according to the authors) : 



Animals over 6 months of age may be regarded as tuber- 

 culous, (a) if the_ highest temperature indicated in the course 

 of a typical reaction exceeds the highest recorded temperature 

 before the injection of tuberculin by 2.7° F. or more, or if the 

 rise was at least .9° F. and higher than 104° F. ; (b) if the tem- 

 perature is elevated 1.8 to 2.5 or exceeds 103.1 with symptoms 

 of an organic reaction. 



Calves under six months of age must show an increase 

 in temperature over 104.9° or 105° F. to indicate a positive 

 reaction. 



The animal may be considered free from tuberculosis if 

 the rise of temperature was not more than 2.7, and did not 

 exceed 103.1 and if the animal showed no organic reaction, pro- 

 vided that a systematic clinical examination revealed no evi- 

 dence upon which to base a suspicion of the disease. 



If the results of temperature records and clinical examina- 

 tions are interpreted according to the above principles they 

 will be found to agree with post-mortem findings in about 98% 

 of all cases, thus possible errors will hardly exceed 2%. > 



However, the rules variously laid down to be followed in the in- 

 terpretation of results of tuberculin tests are at present not as uniform 

 as might be desired. 



According to Nocard a reaction is to be considered as positive if 

 the highest temperature after injection exceeds the highest pre-injection 

 temperature by 2.7, while an increase of 1.5 to 2.5 indicates suspicion 

 only. In the latter case the animal should be re-tested after one month 

 and given an increased dose of tuberculin. 



According to Eber pre-injection temperatures not exceeding 103.1 

 followed . by post-injection temperatures of 104 or more, or at least 

 exceeding 103.1 and in all cases indicating a rise of at least 1.8 must 

 be regarded as positive reactions while post-injection temperatures lower 

 than 104 and exceeding 103.1, but not representing a rise of 0.9 to 1.8 

 must be regarded as pointing to suspicion of tuberculosis. 



According to Ostertag post-injection temperatures exceeding 103.1 

 and representing a rise of at least 0.9 above the highest pre-injection 

 temperature points to the existence of tuberculosis. In calves under 

 six months of age post-injection temperatures exceeding 104 and rep- 

 resenting a rise of at least 0.9 above the highest pre-injection temperature 

 indicate tuberculosis. 



According to the decision of the International Veterinary Congress 

 held in Budapest all cattle showing pre-injection temperatures not 

 exceeding 103.1 and post-inje'ction temperatures exceeding 104 must 



Vol. 1— 3T 



