70 MICRO-ORGANISMS AND FERMENTATION. 



are also found amongst the pigment-forming bacteria, which, 

 in addition to the production of pigments, can convert so 

 much sugar of milk into lactic acid that the caseine of milk 

 coagulates; to these belong, according to HUEPPE, the famous 

 blood -portent (Micrococcus prodigiosus) and, according to 

 KRAUSE, a pathogenic form, the micrococcus of osteomyelitis. 



DELBRUECK states that ZOPF has obtained a lactic acid 

 bacterium by preparing a mash from 200 grams of dry malt 

 and 1000 grams of water, and keeping it for some time 

 at 50 C. The material was then sown in a solution of 

 milk-sugar, on the surface of which the organism formed a 

 film. The filaments consist at first of small rods, later of 

 both rods and cocci. 



PETERS found a bacterium in leaven, which produces a 

 typical lactic acid fermentation. In plate-cultures it forms 

 circular colonies with concentric stratification. The rods have 

 a rapid sinuous motion. In a neutral solution of sugar in 

 yeast- water at 30 C., this species forms a slimy film after 

 some time, the rods having developed into long filaments. 

 Spore-formation has not been observed. 



The so-called Pediococcus acidi lactici, examined by LINDNER, 

 gives a strong acid reaction when cultivated in a neutral 

 malt-extract solution at 41 C. Both in a solution of this 

 kind and in a hay-decoction, which have not been steril- 

 ised, this bacterium develops so vigorously that, according to 

 LINDNER, all other organisms are suppressed. It has been 

 proved chemically that the acid, which is abundantly pro- 

 duced, consists for the most part of lactic acid. When a 

 malt mash or malt-rye mash is maintained at 41 C., the 

 Pediococcus develops vigorously, and the rod-shaped lactic acid 

 bacteria are suppressed. In a neutral malt-extract solution, 

 the Pediococcus is killed after five minutes' exposure to 62 C. 

 In gelatine it does not thrive well ; it is only in puncture- 

 cultivations in neutral malt-extract gelatine, that very vigor- 

 ous white colonies are formed below the surface. This species 

 appears, on the whole, to thrive better when the air is excluded. 



The Saccharobacillus Pastorianus described by VAN LAER, 

 which occurs in the form of rods of different lengths, produces 

 a characteristic disease (" tourne ") in beer, which manifests 



