54 ESSAYS 0\ BACTERIOLOGY. 



tagonizing agents. If, then, it shall be found that 

 the harmful and the helpful agents are different, and 

 the latter can be separately obtained, we may be able 

 to use them successfully even in diseases, such as tu- 

 berculosis, which, under ordinary conditions, show 

 little or no tendency to self-limitation or immunitj'. 

 Such an effort has been made with the tuberculin of 

 Koch. 



Third, It has long been observed that the presence 

 of certain diseases in the body seemed to exclude, or 

 oppose, the entrance of others, and it is now known 

 that there is an antagonism between certain bacteria. 

 Such antagonism may be shown, not only on the cul- 

 ture-plate, but in the body. Thus, rabbits inoculated 

 with the intensely virulent anthrax may be saved from 

 ■death.- by introducing, shortly before or after such 

 inoculation, the micrococcus prodigiosus. Here is an 

 example of cure of a malignant disease: If cowpox 

 is not simply modified smallpox, vaccination may bo 

 said to be an example of immunity afforded through 

 such antagonism. In" both examples the beneficial 

 agent is practically harmless. It is by no means im- 

 possible that here may be found a clue to siiccess with 

 our efforts. 



In conclusion, let us sum up the whole matter and 

 see where we stand to-day, and what grounds we have 

 for entertaining a hopeful prospect. It will be no- 

 ticed, as we review the questions under discussion and 

 study the various plans suggested by bacteriological 



