BACTERIAL PROTEINS 33 



of that bacterium. At first sight these state- 

 ments seem wholly irrational, but when we 

 study them we find that they are not only rea- 

 sonable but in accord with what might have 

 been reasonably predicted beforehand. The 

 guinea-pig is highly susceptible to infection 

 with the tubercle bacillus because the secretions 

 of its body cells have no destructive action on 

 that organism. This together with the fact that 

 the bacillus tuberculosis can feed upon certain 

 proteins in the guinea-pig's body are the essen- 

 tial factors in the susceptibility. The infecting 

 bacillus finds an abundance of suitable food and 

 meets with no resistance. On the other hand 

 the guinea-pig is highly immune to infection 

 with the bacillus prodigiosus because the ani- 

 mal's body cells supply secretions which are 

 immediately destructive to this organism and 

 the first of these bacilli finding their way into 

 the animal's body meet with immediate and 

 complete annihilation. But when the prodigio- 

 sus is grown in vitro and a sufficient amount of 

 its cellular substance, dead or alive, is thrown 

 into the abdominal cavity the same agency 

 which has given the animal immunity to infec- 

 tion now causes it to fall a victim to the protein 

 poison. These facts are of practical as well as 

 scientific interest because they undoubtedly 



