30 



INHIBITORY ACTION OF PARATYPHOID BACILLI 



Table VI gives the results of an experiment to clear up this question. 

 Hog-cholera bacilli were introduced into a number of lactose tubes 

 and kept different periods of time before Bacillus coli was introduced. 

 Cultures incubated 19 days before the second inoculation inhibited 

 gas production completely. Those incubated up to 6 days failed to 

 inhibit. The rest produced variable amounts of gas. 



The paratyphoid bacillus thus produces a condition in 2 to 4 days 

 which the hog-cholera bacillus brings about in 18 days. It is inter- 

 esting to note that this period roughly corresponds to the time 



TABLE VI. 



Efed of Age of Primary Culture on Inhibition of Gas Production. {Primary 

 Culture, Hog-Cholera Bacillus XII; Secondary Culture, B. coli, Calf 302.) 



* Primary culture grown with about \ of closed arm containing air. This was 

 tipped out when B. coli was inoculated. 



required by the hog-cholera bacillus to produce a translucency of milk 

 when used as a culture medium. This translucency proceeds parallel 

 with the increasing alkalinity of the medium. The different behavior 

 of the paratyphoid and the hog-cholera bacilli is thus quantitative 

 rather than qualitative, but the difference is such that at a certain 

 time the phenomenon may be used as a qualitative test. 



The gradual development of inhibition by the hog-cholera group 

 is paralleled by a gradual loss of inhibition by the paratyphoid bacil- 

 lus. This was demonstrated in the following manner. A culture 

 of the paratyphoid bacillus, Calf 297, grown in lactose bouillon in a 



