TUBERCULIN REACTION 627 



False negative reactions are much more likely to occur, and the various 

 conditions that may be responsible for these should be well understood 

 and remembered. 



1. In the final stage of tuberculosis, especially in miliary tuberculosis 

 and in tuberculous cachexia, as in the third stage of pulmonary tubercu- 

 losis, the tuberculin reaction may be negative, or be attained only after 

 the injection of very large doses. There is a lessened cutaneous re- 

 activity (cachectic reaction), marked by the appearance of colorless or 

 pinkish spots, instead of an intense papillary eruption. Koch and Ehr- 

 lich have explained this by assuming that the tissues had become too 

 thoroughly saturated with tuberculin produced at the infected area to 

 respond to further artificial additions. This condition may be regarded 

 as analogous to a state of anti-anaphylaxis in which we may consider 

 the free and sessile receptors united with the tubercle protein or the 

 cells loaded with the antigen, with depression of cellular activity. 



2. In the first stage of infection. At this period the antibody has not 

 been formed in sufficient amounts, different authors obtaining such 

 findings in nurslings. 



3. In small, completely healed lesions, especially in those showing 

 nothing but scar tissue, as in the apex of a lung. In these the antibody 

 and cellular hypersensitiveness have disappeared, and while the lesion 

 may have been tuberculous, one cannot tell anatomically, in a given 

 instance, whether or not hypersensitiveness should have been present. 



4. During continued treatment with tuberculin, when the reaction 

 may be negative owing to a condition of anti-anaphylaxis. 



5. During measles. As von Pirquet and Preisich have demonstrated, 

 the cutaneous reactivity disappears during the first days after the erup- 

 tion, reappearing after about a week. Greuner showed that the "Stich- 

 reaktion" which occurs after large doses of tuberculin did not disappear 

 entirely, indicating that in measles there is a lessened activity, rather 

 than a total disappearance. 



6. Finally, according to von Pirquet, there are a few cases in which 

 we have a minimal reactivity and to which none of the former explana- 

 tions can be applied. Some cases of active tuberculosis may show only 

 a slight hypersensitiveness, although they are not cachectic. 



Of course, it can readily be understood that the use of weak or an 

 otherwise unsatisfactory solution of tuberculin and an improper dosage 

 and technic will greatly influence the results. Likewise errors in inter- 

 preting what constitutes a positive tuberculin reaction are to be guarded 

 against. This applies especially to veterinary practice. For example, 

 cattle brought from the fields and confined in a stall for the purpose of 



