THE SPLIT PRODUCTS OF TUBERCLE BACILLUS 183 



There are those who, while admitting that animals can 

 be sensitized to tuberculoprotein, hold that the tuberculin 

 reaction is not an anaphylactic one. We think that it is, 

 and that the fact that tuberculin does not sensitize or does 

 so imperfectly does not contradict this. It is probable that 

 when tuberculin does sensitize at all it is due to the fact 

 that it contains traces of but little altered or unaltered 

 tuberculoprotein. The tuberculin reaction should be 

 regarded as a phenomenon resulting from a reinjection. 

 The animal is already sensitized by the disease. 



Koch in his early work pointed out two facts, which in 

 a way seemed to be contradictory, but which have been 

 found to be true. First, he showed that a tuberculous 

 animal behaves toward a second infection differently from 

 a normal animal, the former resisting the second infection 

 by forming an inflammatory area about the point of the 

 second inoculation, this leading to necrosis, and recovery 

 without extension of the infection. Second, Koch stated 

 that the injection of dead tubercle bacilli into tuberculous 

 guinea-pigs killed them within from six to forty-eight 

 hours, while like injections into normal guinea-pigs had 

 no such effect. These apparently contradictory statements 

 have not only been confirmed, but have been found not in 

 any way in conflict. The studies of Romer, Hamburger, 

 and others have shown that the following conditions must 

 prevail in order to fully demonstrate the first statement of 

 Koch: (a) The first injection must be a weak one, per- 

 mitting the disease to run a chronic course. (6) The time 

 interval between the first and second inoculations must 

 be relatively long, the resistance to the second infection 

 increasing with time, (c) The dose of the second injection 

 must not exceed a certain limit. What happens to the 

 bacilli of the second inoculation? Why should these fail 

 to develop, while those of the first inoculation continue to 

 grow? Kraus and Hofer 1 have found that tubercle bacilli 

 injected into the peritoneum of a tuberculous animal are 



1 Deutsch. med. Woch., 1912. 



