26 



INHIBITORY ACTION OF PARATYPHOID BACILLI 



sterile rubber stoppers, and thoroughly shaken by hand. They were 

 then centrifuged for about 30 minutes, at the end of which time the 

 supernatant fluid was clear to the unaided eye in transmitted light. 

 It was then transferred with sterile pipettes to sterile fermentation 

 tubes and inoculated with Bacillus coli, Calf 302. 



TABLE II. 



To determine whether the kaolin itself might add anything to the 

 medium to influence the result various controls were introduced as 

 shown in Table III. 



TABLE III. 

 Effect of Centrijuging and Clearing First Culture with Kaolin on Second Culture. 



Tube a shows that a complete clearing of the culture fluid from 

 paratyphoid bacilli restores gas production by Bacillus coli and is 

 equivalent to filtration. Tubes b, c, and d were to show whether 

 kaolin modified the fermentation. The larger amount of gas produced 

 in b indicates the presence of some favoring impurity on gas produc- 



