146 



PROTEIN POISONS 



still exists in combination with other constituents of -the 

 bacterial cell. 



The question now arose as to whether the animals treated 

 with increasing doses of the residue had acquired any 

 immunity to infection with the living colon bacillus. To 

 ascertain this point, guinea-pigs were treated with this 

 portion and subsequently inoculated with the living germ 

 with the following results: 



TABLE XI 



Nos. 1, 2, 3, AND 4 RECEIVED A CULTURE, 1 c.c. OF A 12-nouR CULTURE 

 OF WHICH CAUSED DEATH IN UNTREATED PIGS WITHIN TWENTY- 

 FOUR HOURS. THE REST RECEIVED A CULTURE, \ c.c. OF WHICH 

 INVARIABLY PROVED FATAL TO UNTREATED ANIMALS. 



From the above table it will be seen that guinea-pigs 

 which have been treated with that portion of the colon 

 bacillus which is represented by the residue have acquired 

 an active immunity to at least eight times the fatal dose of 

 the living germ. The degree of immunity produced does 

 not depend so much upon the amount of residue which 

 has been injected as upon the number of treatments and 

 the interval of time over which they have been continued. 



