BACTERIOLOGY. 



nization, however, a " specific " something is 

 added by the " specific " parasites. 



The existence of this essential difference 

 can be properly attested only by experiment. 

 Fowls which are, by nature, immune to teta- 

 nus do not possess in their blood any anti- 

 substance which destroys the tetanus toxin, 

 yet these animals show no symptoms of the 

 disease when they are injected with tetanus 

 culture, . Natural " specific " immunity seems 

 in their case to be connected with some general 

 property of the tissues, in contrast to artificial 

 immunity which is supposed to depend upon 

 the presence of specific anti-substances in the 

 blood. 



In the first place, we must ask, what are the 

 facts upon which we base our conception of the 

 protective power of the human and, in general, 

 of the animal organism ? 



As a matter of fact, the animal body ordi- 

 narily possesses the ability of ridding itself of 

 bacteria and their toxins. It is always to be 

 borne in mind in this discussion, that in certain 

 diseases the toxins, and in others the bacteria 

 themselves play the more prominent part. The 

 fact that the animal organism can cope with 

 living bacteria was observed in 1864, by M. 

 Traube and Gescheidlen. These investigators 

 introduced putrefactive bacteria into the blood, 



