164 



The above table shows that the secretions of B. fluorescens in the flask 

 penetrate the collodion sac containing the typhoid culture. There takes 

 place, then, not merely an inhibitory action, but an actual bactericidal one. 

 The secretions have to be of a certain concentration before this action 

 takes place. It is found that the above is not true for the cultures show- 

 ing slight chroruogenesis. 



In the next experiment. />'. fluorescens was planted and allowed to grow 

 before B. typhosus was introduced into the sac. The following table shows 

 the results obtained. 



Table III. 



After growing B fluorescens for twenty-four hours, inoculating the sac 

 with B. typhosus, and again incnbatin.it for twenty-four hours: 



B. fiuoresceihs. B. typhosus growth. 

 No. 29 Absent. 



No. 469 Absent. 



No. 502 Present. 



No. 31 Present. 



After growing B. fluoresce))* for forty-eight hours, inoculating the 

 sac with B. typhosus, and again incubating for twenty-four hours : 



B. fluoresce)!*. B. typhosus growth. 

 No. 29 Absent. 



No. 469 Absent. 



No. 502 Present. 



No. 31 Present. 



This table shows that once the toxic substances are produced in suf- 

 ficient quantities and time enough is given for them to penetrate the sac, 

 the typhoid organisms will not grow. 



In the next experiments the fluorescens organisms were grown for 

 ten days, then filtered and the filtrate sterilized for ten minutes at a 

 pressure of fifteen pounds in the autoclav. The sterilized filtrate was then 

 inoculated with B. typhosus and at the end of twenty-four hours samples 

 were plated with plain agar and incubated. 



The results are shown in the following table : 



