INFECTIONS OF THE DIGESTIVE TRACT 41 



for a small number of the Gram-positive bacilli seen 

 in the microscopical field. Moro, who first described 

 these bacteria under the title of B. acidophilus, supposed 

 that their presence explained fully the normal Gram- 

 positive bacillary field, but this proved to be an error. 



On subjecting the mixed bacterial flora to strict 

 anaerobic conditions, Tissier found he could regularly 

 cultivate from the nursling's faeces certain slender, Gram- 

 positive bacilli of moderate length and thickness which 

 not infrequently presented a bifurcated extremity and 

 to which he accordingly gave the name B. bifidus. 

 There can be no doubt that a large majority of the 

 bacteria seen in the microscopical fields may be classed 

 as B. bifidus. The bacteria belonging to the B. bifidus 

 group possess a varied morphology which it seems 

 desirable to notice here in view of the physiological 

 importance of these bacteria during infancy. The ap- 

 pearance of the organisms is somewhat different accord- 

 ing as we meet with them in the faeces or in culture 

 media. In the microscopical fields they are recognizable 

 under three chief forms: (1) a plain bacillary form, 1 



1 The individuals of this class are rods of varying dimensions 

 (length 3-5 /A ; breadth, 0.2-0.4;*). They are usually straight 

 or slightly bent with somewhat pointed or rounded ends. Oc- 

 casionally, owing to attenuation of one end and excessive develop- 

 ment of the other, they assume a comma form. There is nothing 

 characteristic about the arrangement of the bacilli in smears. 

 Although distinctly Gram-positive, they vary much in the degree 

 in which they retain the dye, both in material from the same in- 

 fant at different times, and in different individuals. The entire 

 bacterium is frequently not stained with even intensity, some parts 

 of the organism retaining the color well, while other portions give 

 it up. The result is the appearance which Escherich expressed 



