INFECTION AND IMMUNITY. 431 



by Behring and his colleagues, in their successful efforts to 

 devise a cure for diphtheria in man has resulted in one of 

 the greatest triumphs of the day. It marks an epoch in 

 modern scientific medicine. The same principle has been 

 employed for obtaining curative agents against other 

 forms of infection, but as yet, unfortunately, with in- 

 different success. 



Another hypothesis in explanation of the immunity 

 acquired by the tissues of the animal organism is that 

 advanced by Buchner, 1 who suggests that in the primary 

 infection, from which the animal has recovered, there 

 has been produced a reactive change in the integral cells 

 of the body that enables them to protect themselves 

 against subsequent inroads of the same organism. 

 Though somewhat more vague at first glance than the 

 other theories in regard to this phenomenon, it is, never- 

 theless, in the light of subsequent research, most prob- 

 ably the correct explanation of the establishment of 

 immunity in many, if not all, cases. Experiments that 

 bear directly upon this idea have demonstrated that, if 

 animals be subjected to injections of the poisonous 

 products of growth of certain virulent bacteria, they 

 respond to this treatment by more or less pronounced 

 constitutional reactions, and that during this period, and 

 for a short time following, they possess protection 

 against the invasion of the virulent bacteria themselves. 

 This observation has, moreover, not been confined to 

 those cases in which injections of the products of growth 

 have been followed by inoculations with the bacteria by 

 which they were produced, but what is still more in- 

 teresting, and confirmatory of Buchner's view, it is 



1 Buchner : Eine neue Theorie iiber Erzieiung von Immunitat gegen In- 

 fektionskrankheiten. Munich, 1883. 



