CULTURAL CHARACTERS. 



405 



ing embedded gas bubbles. It is the rule to find gas bubbles 

 lying in the fluid between the potato and the walls of the tube. 

 The medium never becomes discoloured. Bouillon is heavily 

 clouded, and occasionally gas bubbles are seen on top. The 

 precipitated growth is semi-flocculent, white, and diffuses on 

 agitation. In litmus milk there occurs the 

 most characteristic reaction. At the end of 

 twenty-four hours the reaction is strongly' 

 acid, the casein is found to be coagulated 

 firmly, but at the same time is more or less 

 completely riddled by cavities caused by gas 

 formation (Fig. 137). The resulting whey is 

 usually quite clear; occasionally it may be 

 turbid and yellow. Viscidity is present on 

 rare occasions. Now and again a layer of 

 gas bubbles may cover the surface of the fluid. 

 There is a strong odour of butyric acid pres- 

 ent. Gelatin may be slowly liquefied by 

 some races of the bacillus, or may merely 

 undergo a softening without any definite 

 liquefying ; this latter seems to be more 

 common. Gas formation may occur, due 

 to presence of muscle sugar in the meat 

 extract. On solidified blood scrum along the 

 line of inoculation is found a rich cream- 

 coloured, elevated, glossy growth, which 

 at the end of a week seems to exercise a 

 feeble peptonising power, denoted by a 

 small furrow forming in the medium upon 

 which the growth rests, but this never goes on to liquefaction. 



Lactose, saccharose, and mannite are actively fermented, 

 with accompanying gas formation ; so is dextrose-free bouillon 

 and ascitic fluid, and from these facts Welch is of the opinion 

 that the bacillus is capable of forming gas from proteid material 

 alone. 



Significance. Its presence in the tissues during life is to be 

 looked upon as serious in most cases and deserving of prompt 

 attention, surgical or otherwise. Post mortem, in the absence of 

 any possible external point of entry, its existence is a matter of 

 no importance, as, like the colon bacillus, it is capable of wan- 



FlG. 137. B. aerog- 

 enes capsulatus. A 24- 

 hour-old milk culture, 

 showing typical coagula- 

 tion of the casein. Natu- 

 ral size. 



