582 GASTRO-INTESTINAL BACTERIOLOGY 



forming types disappear for the most part and rather abruptly, and 

 the coccal forms and Gram-negative bacilli of the colon aerogenes type 

 diminish relatively, but never quite disappear. Simultaneously rather 

 long, thin bacilli, occurring singly, in pairs, or in groups with their 

 axes parallel, become strikingly prominent. These bacilli are fre- 

 quently slightly curved and occasionally their ends are somewhat 

 attenuated. Typically they are Gram-positive and stain uniformly, 

 but in many instances they exhibit a central Gram-positive granule 

 in an otherwise Gram-negative rod, presenting the "punctate" appear- 

 ance described by Escherich. 1 Occasionally the cytoplasm of these 

 organisms is collected into small, round or oval granules which stain 

 intensely; the remainder of the rod stains faintly or not at all. At 



FIG. 96. Bacillus bifidus. Sediment from lactose fermentation tube. X 1000. 



first sight these granules resemble chains of cocci. This somewhat 

 pleiomorphic organism is Bacillus bifidus, first observed by Escherich, 

 but isolated in pure culture and studied in detail by Tissier. 2 It is an 

 obligate anaerobe, 3 fermentative in character, which typically forms 

 considerable amounts of acid from lactose and other sugars, but no 

 gas. The organism received the name "bifidus" from its remarkable 

 property of developing well-defined bifid ends when it is grown in 

 artificial media; it does not ordinarily exhibit bifid ends in the intes- 

 tinal tract. Moro 4 and, independently, Finkelstein 5 have isolated and 

 described an organism very similar in morphology to Bacillus bifidus 



1 Loc. cit. 



2 Recherches sur la Flore Intestinale des Nourrissons, etc., These de Paris, 1900, p. 85. 



3 Noguchi (Jour. Exp. Med., 1910, xii, 182) appears to have shown that Bacillus bifidus, 

 under laboratory conditions, may become aerobic and form spores. 



4 Wien. klin. Wchnschr., 1900, xiii, 114. 



6 Deutsch. med. Wchnschr., 1900, xxii, 263. 



