408 ALFRED H. RAHE 



workers to provide a suitable medium for the cultivation of these 

 bacteria. 



In 1914 Rahe was able to show that these organisms would 

 develop with a very satisfactory degree of luxuriance in unneu- 

 tralized meat-peptone-broth containing a suitable carbohy- 

 drate. We have carried various strains of aciduric organisms 

 for years in this broth. Although the writer has in subsequent 

 communications tried to place sufficient emphasis on this fact, 

 the fallacy still persists that these bacteria are not readily grown 

 on the "usual" laboratory media. 



Once the difficulty attending the cultivation of the aciduric 

 bacteria was removed, an examination of the cultural charac- 

 teristics of a number of strains brought to light several signifi- 

 cant differences between the members of this group. It became 

 evident that the Bulgarian bacillus could not utilize maltose 

 (some strains could not ferment sucrose) and in this respect 

 differed from the great majority of aciduric bacilli found in the 

 human intestine and elsewhere. The latter could be conven- 

 iently grouped according to whether they clotted milk or 

 failed to do so. The failure of B. bulgaricus to ferment maltose 

 made it possible for the writer (1915) to demonstrate that this 

 organism apparently does not exist as an intestinal inhabitant 

 in human beings. The examination of hundreds of strains of 

 aciduric bacilli from human feces that did not embody purposely 

 ingested B. bulgaricus has failed to reveal a single organism of 

 that type. 



Rogers and Davis (1912) quote Hastings (1908), Hastings 

 and Hammer (1909) and Heinemann and Hefferan (1909) as 

 having shown that the Bulgarian bacillus is "widely distributed 

 and may be isolated from almost any sample of milk." Most 

 of these authors admit the difficulty of cultivating aciduric 

 bacteria in glucose broth, and this is true if the "natural" acidity 

 of the broth is interfered with. The unneutralized broth men- 

 tioned above overcomes this difficulty, probably owing to its 

 unaltered amino acids or other growth-promoting substances, 

 such as were described for the meningococcus by Lloyd (1917). 

 In the present investigation organisms corresponding to the 



