410 BACTERIOLOGY. 



tetanus. In their studies upon the blood of animals 

 subjected to these experiments it was found that it was 

 not only possible to render animals immune from this 

 disease, but that the serum of the blood of these im- 

 munified animals affords immunity when injected into 

 the peritoneal cavity of other animals that had not been 

 so protected ; and moreover, that this serum possesses 

 curative powers over the disease after it has, in some 

 cases, been in progress for a time. They found, further, 

 that the serum of animals that had been rendered im- 

 mune to tetanus, when brought in contact with the 

 poison of tetanus, completely destroj'ed its poisonous 

 properties, and that the serum from animals or from 

 human beings that do not possess immunity to this 

 disease has no such power. 



Another hypothesis in explanation of the immunity- 

 acquired by the tissues of the animal organism is that 

 advanced by Buchner,' 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 them- 

 selves 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 are subjected to injections of the poison- 

 ous products of growth of certain virulent bacteria, 

 they respond to this treatment by more or less pro- 



1 Buchner : Elne neue Theorie Uber Erzielung von Immunitst gegen In- 

 fektlonskrankheiten. Munich, 1883. 



