FERMENTATION 189 



The bacillus is 1 p to !! p long by about 0-3 p to 0-4 IJL 

 broad, generally occurring in pairs and in strings of four 

 elements. (See also p. 108). It converts milk sugar 

 into lactic acid. Fermentation ceases after a certain 

 amount of lactic acid has been formed, but will recom- 

 mence if the liquid be neutralised with calcium carbonate. 

 Fermentation will also recommence if the milk is still 

 further left to itself, for moulds neutralise acid. 



The MassoJ bacillus (B. Bulgaricus), sometimes in con- 

 junction with Streptococcus lebenis* and a yeast, is used 

 for the production of ' Bulgarian Soured Milk,' for use in 

 diseases arising from auto-intestinal intoxication due to 

 noxious bacterial growth. When acclimatised in the 

 bowel this organism hinders multiplication of other 

 organisms, and, ipso facto, the circulation of their meta- 

 bolic products. It is of prime importance that the milk 

 used should be sterile before inoculation with the Massol 

 culture, and many makers remove more or less of the fat 

 to produce a better-looking product. Only quick-growing 

 strains should be used for the purpose, such as will curdle 

 milk in ten hours. Cultures of the organism are also 

 administered per os in the form of tablets or bonbons. 

 Some preparations are useless. 



Young organisms are Gram-positive; older ones maybe 

 Gram-negative, or only partially retain the stain. Growth 

 is difficult on most media, but good in milk, Cohendy's 

 milk-serum medium, and on milk peptone agar. Growth 

 is said to be best at 105 to 108 F. Currie says the 

 bacilli of B. Bulgaricus type in human faeces and human 

 saliva are identical. Some strains produce small amounts 

 of succinic acid, which may account for the presence of 

 this acid in Cheddar cheese. 



B. bifidus (Teisser) and B. acidophilus (Moro) (see 

 p. 92) are other lactose-fermenters that grow in acid 

 media. 



Saccharobacillus Pastorianus is the cause of the ' turn 

 ing ' of beer, producing lactic acid. 



B. butyricus is an aerobic, short or long thin rod, with 

 rounded ends, which forms spores, but seldom threads. 

 It is actively motile, and rapidly liquefies gelatin, with 

 formation of a pellicle. It coagulates and decomposes 



* Sewerin considers S. Ifbenis to be identical with B Bulgaricus , 

 but his view is not generally accepted. 



