110 BACTERIOLOGICAL EXAMINATION OF WATER. 



but brown and granular in transmitted light. The agar is 

 not liquefied, and the bacilli do not form spores. On the 

 surface of agar anaerobic plates, after twenty-four to forty-eight 

 hours incubation the colonies are circular, flat, moist, grey 

 and translucent. " Examined under a low power, each colony 

 is a little thicker and less transparent in the middle part, 

 thinned out and more transparent in the marginal portion. 

 At the same time the colony is distinctly granular, the granules 

 being placed closer and denser in the middle part, and less 

 close in the marginal part." Spores are not formed in these 

 colonies. In glucose-gelatine the bacillus produces gas arid 

 causes liquefaction of the medium. When spores are planted 

 in grape-sugar gelatine, which is then heated to 80 C. for ten 

 to fifteen minutes, and then cooled, sealed, and incubated at 

 22 C., fine, dot-like colonies appear in the lower part of the 

 tube, which after forty-eight hours form spherical liquefied 

 masses of gelatine. If bacilli, free from spores, are planted in 

 sugar-gelatine, the colonies appear non-liquefying, or liquefy 

 very late and slowly. When tested as to its staining 

 reactions, the bacillus is found to be stained by the ordinary 

 basic aniline dyes, and also by Gram's method. 



The above description gives the chief characteristics of the 

 typical B. enteritidis sporogenes ; but Klein found sometimes 

 that the spores from subcutaneous exudation, serum and 

 gelatine cultures, when placed in milk and heated to 80 C. for 

 ten to fifteen minutes, produced no change at all in the milk for 

 the first two days. About the third or fourth day, however, the 

 milk began to clear under the unchanged layer of cream. By 

 the end of a week or ten days the milk culture showed on the 

 top a layer of unaltered cream, below which the medium 

 consisted in the main of a clear or slightly turbid pale yellow 

 watery fluid ; at the bottom of the tube there was a white mass 

 of caseine. The whey from this milk culture was found to be 

 offensive, alkaline in reaction, and to contain bacilli and spores 

 which had no pathogenic action. Such an atypical milk culture 

 was at first considered to be produced by B. enteriditis 

 sporogenes which had lost its virulence. But further experi- 

 ments showed that the appearances produced in the atypical 

 milk culture were caused by a new bacillus, called by Klein the 



