165 
taining the same kind of medium. After sterilization in the autoclay, 
the sac and flask are inoculated with the different cultures to be studied. 
The sac prevents the bacteria from mingling but, being permeable, permits 
the diffusible products of metabolism to distribute themselves uniformly 
throughout the liquid medium. By taking samples from both tube and 
flask and plating, it becomes a rather simple matter to determine whether 
the life or the growth of either organism is affected by the manufactured 
products or wastes of the other. 
The experiments were run in series. Hach series consisted of five 
flasks. Four of these contained B. typhosus in the sac and one of the 
cultures of B. fluorescens in the flask. The fifth was used as a control and 
contained only B. typhosus. Four of these series were run simultaneously. 
The temperature was 37 degrees Centigrade. The experiments ran through 
a period of twelve weeks. 
Of the strains of B. fluorescens used, cultures No. 29 and No. 469 im- 
parted a very deep color to the medium after growing for twenty-four 
hours; No. 31 and No. 502 imparted very little color. 
The next table shows a certain correlation between the elimination 
of B. typhosus by B. fluorescens cultures secreting a deep colored pigment 
as compared with those cultures secreting very little pigment. 
TABLE IT. 
After twenty-four hours incubation. 
Flask-containing B. fluorescens. Sac containing B. typhosus. 
No. 29 Growth. 
No. 469 Growth. 
No. 502 Growth. 
No. 3 Growth. 
After forty-eight hours incubation. 
No. 29 No growth. 
No. 469 No growth. 
No. 502 Growth. 
No. 31 Growth. 
After seventy-two hours incubation. 
No. 29 No growth. 
No. 469 No growth. 
No. 502 Growth. 
No. 31 Growth. 
