PHENOMENA OF SUPERSENSITIVENESS 287 



subjects. The original explanation given by Koch of the 

 tuberculin reaction was that the essential constituent of tuber- 

 culin being toxic products of the tubercle bacillus, the action 

 of these was superadded to the toxins produced at the focus of 

 infection. The combined action of the toxins from these two 

 sources caused a rapid necrosis of the newly formed cells, and 

 opened the way for the dead tissue being rapidly cast off. This 

 explanation was, however, not generally accepted, for it was 

 found that other substances, such as albumoses, when injected 

 into animals suffering from local tuberculosis, gave rise to modified 

 effects of the same kind as those produced by tuberculin. This 

 dissatisfaction with regard to the original explanation is ac- 

 centuated by a consideration of the effects seen in the Calmette 

 and v. Pirquet tests, as these clearly indicate that the sensitive- 

 ness in a tubercular subject is not confined to tissues actually 

 affected with the tubercular process, but is also manifested in 

 parts of the body distant from the site of actual infection. 



Further, it has been found, first, that the injection of tuber- 

 culin directly into a tubercular focus does not produce the 

 tuberculin reaction (a fact which militates against the idea of 

 concentrations of toxins), and, secondly, that the injection of 

 living or dead tubercle bacilli into healthy animals produces 

 anaphylactic phenomena similar to those originated by foreign 

 albumins generally. At the present time, therefore, although 

 no full explanation can be given of the tuberculin reaction and 

 of similar reactions, it is likely that in tuberculosis a general 

 hypersensitivenesH is developed, and may be the underlying 

 phenomenon. These reactions must therefore be considered in 

 the light of what will be set forth on the subject of hypersen- 

 sitiveness in the chapter on Immunity. 



The Use of Old Tuberculin in the Diagnosis of Tuberculosis in Cattle. 

 111 cattle, tuberculosis may be present without giving rise to apparent 

 symptoms. It is thus important from the point of view of human 

 infection that an early diagnosis should be made. The method is 

 applied as follows : The animals are kept twenty-four hours in their 

 stalls, and the temperature is taken every three hours, from four hours 

 before the injection till twenty-four a'fter. The average temperature in 

 cattle is 102'2 F. ; 30 to 40 centigrammes of tuberculin are injected, and 

 if the animal be tubercular the temperature rises 2 or 3 F. in eight to 

 twelve hours, and continues elevated for ten to twelve hours. Bang, who 

 has worked most at the subject, lays down the principle that the more 

 nearly the temperature approaches 104 F. the more reason for suspicion 

 is there. He gives a record of 280 cases where the value of the method 

 was tested by subsequent post-mortem examination. He found that with 

 proper precautions the error was only 3'3 per cent. The method has 

 l>ti 11 largely practised in all parts of the world, and is of great value. 



