Subcutaneous Tubereuliu Test. 579 



to Storch the simultaneous admiDistration of an antipyretic (e. g., 30.0 gni. acetauilid) 

 will prevent a thermal reaction. 



A positive tj^pical reaction to tuberculin indicates the 

 presence of tuberculosis with a great degree of certaint}^, even 

 in the initial stages of the disease. If the evidence revealed 

 at a post-mortem examination does not confirm the diagnosis 

 it is more than probable that the lesions were so minute, or 

 restricted to so small an area that they escaped detection. In 

 some instances the morbid process is actually limited to a single 

 focus as large as a pea in a lymph gland, or possibly to a diffuse 

 swelling of some lymph glands (lymphoid stage, see p. 532) or 

 a spotted reddening of their tissues (Hottinger). (Bang, in 

 the abundant material at his disposal, found three cases only 

 where reacting animals showed no lesions of tuberculosis on 

 post-mortem examination.) 



In the past the lymph glands, which are not infrequently the sole seat of 

 the tuberculous process, received little attention and thus we have an explanation 

 of the many apparent mistakes in diagnosis. Even in those cases where post-mortem 

 examination of i-eacting animals revealed the presence of some other disease instead 

 of tuberculosis (actinomycosis, botryomyeosis, abscesses in internal organs, ver- 

 minous bronchitis, distomatosis, caseated echinococcus cysts, etc.) it would be difficult 

 to eliminate the possibility that tuberculosis did not exist simultaneously in some 

 organ of the body. In this connection the fact should be noted that nearly all 

 animals upon which observations were made, or which served as a basis for statistics 

 on this subject, where slaughtered for meat and that minute examinations of all 

 organs, bones and joints were out of the questions for economic reasons. 



The absence of a tuberculin reaction does not have the 

 same decisive diagnostic value because some animals with ad- 

 vanced disease and suffering from disorders of nutrition will 

 not react, at least not during the usual period of observation. 

 This fact, however, is of little practical importance because 

 cases of this kind can be detected by their clinical s^nnptoms 

 or they will at least be suspected. In some of these cases post- 

 mortem examination has revealed calcified foci in which living 

 bacilli could not be found. 



It is possible that in many of the eases referred to reactions actually occurred 

 but were not observed during the usual period of observation (12th to 21st hour 

 after injection). In experimental tuberculosis of cattle and goats the reaction may 

 set in as early as the 2d to 5th hour and reach its maximum at the 6th to flth hour 

 (Arloing). In cattle that have previously received injections of tuberculin 

 the reaction may pass over sooner than normally and in advanced disease it may 

 set in very late. With these possibilities in mind a careful clinical examination 

 should be made in all cases where the least suspicion may exist of the possible 

 presence of the disease (chronic cough, barrenness, intestinal, uterine or udder 

 affection, etc.). 



How important, aside from the use of active tuberculin, a correct interpretation 

 of the reaction and the experience of the observer or veterinarian really is shown 

 by the results of tuberculin tests in Bavaria (1895-1899) according to which errors 

 in positive diagnosis fell from 13.5% to 2.6% in four years and those of negative 

 diagnosis from 11.1% to 5.7%. 



According to Bang tuberculosis may be recognized in 96% of all cases sub- 

 jected to careful and accurate tuberculin test. Malm gives as his estimate under 

 'the same conditions 2% of failures in recognizing the disease. According to 

 Jensen's compilations, of 468 tuberculous animals 90.8% reacted, 4.9% failed to 

 react and 4.3% gave doubtful reactions; of 290 non-tuberculous animals 14.5% 

 reacted, 81.7% did not react and 3.8% gave doubttul reactions. According to 



