INFECTIONS OF THE DIGESTIVE TRACT 19 



point. It also appears doubtful whether there are heat- 

 resisting substances formed by B. coli which are of value 

 in checking surface growths made under the conditions 

 already mentioned. It was found that there was no 

 difference in the surface growth of B. coli if the agar me- 

 dium containing twenty-four-hour cultures of B. coli was 

 heated for thirty minutes at 90 C. or 100 C. Of course 

 in this experiment it was necessary to exclude the factor 

 of an exhausted medium previous to making the surface 

 cultures, since in the presence of such an exhausted 

 medium organisms would naturally not grow upon the 

 surface. These various experiments speak against 

 any specific inhibitory substances. It would, indeed, 

 be a remarkable and apparently contradictory phenom- 

 enon if organisms should form substances in the course 

 of their growth which are more injurious to themselves 

 and their own species than to foreign ones. Yet this 

 view is apparently assumed by Conradi to be correct. 

 In order to explain the dominance of the colon bacilli 

 in the intestine he has had to make the assumption that 

 these organisms have given rise to substances against 

 which they have become immunized a complex 

 assumption. It is also singular that the autotoxines 

 of Conradi should act in an inhibitory manner without 

 causing actual death, if it be true, as claimed, that these 

 autotoxines are inhibitory in an even higher degree than 

 carbonic acid. Conradi and Kurpjuweit, in spite of this 

 fact, attribute the bactericidal action of fresh faeces to 

 these inhibitory substances. It is difficult to under- 

 stand how, if these supposed restraining substances are 



