440 P. G. HEINEMANN AND E. E. ECKER 



branching forms resembling the letter Y were observed. In all 

 cases of material obtained from teeth the typical milk reaction 

 resulted after three transfers in litmus milk. On account of 

 the granular staining we assume that the lacto-bacilli from dis- 

 eased teeth belong to the low-acid type. 



This investigation confirms the results of previous work in- 

 dicating that the Boas-Oppler bacillus is a member of the group 

 of lacto-bacilli. Its cultural characteristics are in harmony with 

 the descriptions of the group given by various authors and it 

 appears established that members of the B. hulgaricus group 

 are present in saliva, diseased teeth, gastric juice and the in- 

 testinal contents. The source can undoubtedly be looked for 

 in certain foods, especially milk and milk products. 



The finding of lacto-bacilU in large numbers in carious teeth 

 is perhaps not conclusive evidence that they are actually the 

 cause of decay. Experimental evidence to prove this would 

 of course be difficult to obtain. However, since that kind of 

 decay of teeth is usually ascribed to the presence of relatively 

 large quantities of acid and since normal saliva is of an alkaline 

 reaction the assumption is not difficult to arrive at that lacto- 

 bacilli may be the cause. This is further supported by the 

 fact that Heinemann and Hefferan found large numbers of 

 lacto-bacilli in a sample of saliva of acid reaction. 



White and Avery (1909) have attempted to separate the 

 group of lacto-bacilli into two types as follows: Type A stains 

 homogeneously with Loffler's methylene blue and Neisser's 

 stain, produces 2.7 to 3.7 per cent lactic acid in milk and the 

 lactic acid formed is of the inactive variety. Type B, stained 

 with Loffler's methylene blue or Neisser's stain shows intensely 

 stained granules; the bacilh of type B produce 1.2 to 1.6 per cent 

 lactic acid in inilk and the lactic acid formed is always levo- 

 rotatory. According to this classification the strains examined 

 by us belong to type B. 



Rahe (1914) has classified aciduric bacteria according to their 

 ability to clot milk and produce acid from maltose. He dis- 

 tinguished three varieties, namely: Variety A which clots milk, 

 but has no action on maltose; variety B which clots milk and 



