Anerobe Suggesting B. Pneumosintes 281 



is commonly if not always present in the oral cavities of human 

 beings. 



The anaerobe is very small, well under 0.5 micra long, by a 

 little less in width. (Measurements under a half micron are not 

 very accurate). It is smaller than B. prodigiosus, B. broncho- 

 septicus and B. influenza. Illustrations of B. pneumosintes, as 

 given by Olitsky and Gates in their earlier reports, indicate its 

 size. This coccoid bacillus is non-motile, gram negative, occurs 

 singly, often in pairs, and in irregular groups, depending on 

 the medium, and is strictly and persistently anaerobic. In Veillon 

 agar shakes, its colonies, never growing nearer than 1 cm. to 

 the surface, vary with the dilution used, and are remarkably 

 uniform in any given tube. The size varies from very tiny 

 colonies when crowded to large disks or compound disks when 

 widely isolated. The same variation in size is true of surface 

 colonies. They remain individual even when crowded, are raised, 

 with a clearer sharp border and of a greyish white color. It 

 is rather restricted in its test tube biological characters. In 

 Veillon agar (containing sugar) gas production may be, and 

 often is, absent. On occasions it may produce abundant gas. 

 The conditions favoring or interfering with the demonstration 

 of gas has not been determined, but it would appear to be in- 

 dependent of sugar content. The same is true in fluid media, 

 using our (W. L. H.) modification of the Hall anaerobic tube. 

 There is no indication of acid production. 



The gas production in cooked meat medium is constant and 

 abundant, and is the outstanding test tube biological feature. 

 The gas contains traces of hydrogen sulphide, but its analysis 

 is not completed. 



We have been able to pass this minute anaerobe through a 

 Mandler filter tested against B. pyocyaneus, but which allowed 

 B. prodigiosus to go through under 20 pounds pressure. We 

 are at present developing a method for more accurately testing 

 filters before using them for bacterial filtration, following the 

 method given by Bullock and Craw, and by Ferry. The work of 

 Ferry on the filtration of B. bronchisepticus is important in this 

 connection. 



We have further been able to isolate this same tiny anaerobe 

 from the mouth cavity of two normal rabbits. 



We consider this bacterium of importance for the following 

 reasons: (1) It may easily be confused with B. pneumosintes 



