A STUDY OF THE BOAS-OPPLER BACILLUS ' 441 



ferments maltose; and variety C which ferments maltose, but 

 does not clot milk. Strains F, P and S of our series belong 

 to variety A of Rahe and the strain from mfant feces belongs to 

 variety B. 



The presence of lacto-bacilli throughout the digestive tract 

 has some bearing on the hypothesis of Metchnikof that life 

 can be prolonged by estabUshing bulgarian bacilli permanently 

 in the digestive tube. Rahe (1915) studied the problem of 

 implanting B. hulgaricus in the alimentary tract and came 

 to the conclusion that it cannot be adapted to the human lower 

 intestine and that in monkeys the B. hulgaricus is capable only 

 of an apparently limited survival in the upper intestine. The 

 author further claims that B. hulgaricus can be readily distin- 

 guished from intestinal aciduric bacteria by its lack of ability 

 to ferment maltose. 



With these facts before us it seems clear that there is no 

 support for the theory that lactic acid in statu nascendi is of 

 value in suppressing intestinal putrefaction. The chief differ- 

 ence between the lacto-bacilli normally present in the alimentary 

 tract and typical B. hulgaricus is the smaller amount of lactic 

 acid produced by the former. However, the actual quantity 

 produced is about 1.5 per cent, an amount which is greater than 

 can be assumed actually to exist in the digestive tube. If we 

 consider further that earher findings of B. hulgaricus in feces, 

 even after ingestion of bulgarian milk, were not entirely trust- 

 worthy on account of imperfect technic and that no attempt was 

 made to distinguish between the high-acid and low-acid types, 

 it becomes evident that the existence of an appreciable quan- 

 tity of lactic acid in the digestive tract as a result of bacterial 

 action is at least questionable. There can be no reasonable 

 doubt about the actual formation of lactic acid by bacteria m 

 the digestive tract, but the acid is promptly decomposed and 

 utilized by the system. 



The question naturally presents itself whether the types A 

 and B of White and Avery are pennanent or the result of en- 

 vironmental conditions and changeable. Type A is represented 

 chiefly by typical B. hulgaricus. It forms about twice as much 



