BACTERIA. 65 



Recently a methodical pure cultivation of certain lactic 

 acid bacteria has been introduced into practice, the principles 

 being the same as those carried out by Hansen in the case of 

 alcoholic ferments in breweries, the object being to attain a 

 more rational acidification of the cream employed for making 

 butter. Wcigmann, Storch, and Qvist have isolated a series of 

 lactic acid bacteria which, when employed for the acidification 

 of the cream, have imparted to the butter a more or less 

 pure sour taste, and also a more or less aromatic odour, whilst 

 the durability of the butter likewise varies with the different 

 species. 



Storch particularly mentions one species which, in experi- 

 ments on the acidification of cream for the use of dairies, not 

 only gives it a pure and mild slightly sour taste, but also 

 imparts a markedly pure aroma both to the cream and to the 

 butter made from it. In gelatine this species forms very 

 small colonies of a pure white colour and with a smooth 

 border. In milk and whey it occurs as plump, oval, or 

 spherical bacteria, which form flexible chains. It bears 

 some resemblance to Pasteur's " ferment lactique." At 

 28 C. it develops a marked fermentative activity. 



Qvist has cultivated another species, which has been 

 employed with still greater success in practice. It occurs 

 both as micrococcus and in other forms, according to the 

 different nutrient media in which it is cultivated. In 

 gelatine it forms small, circular, slowly-growing colonies of 

 a whitish-yellow colour. In puncture-cultivations spherical 

 colonies arise throughout the puncture-channel, and in streak- 

 cultures this organism forms a continuous streak with wavy 

 borders. It was prepared from a sample of butter of remark- 

 able aroma and durability. 



On the other hand, several species of bacteria have been 

 discovered in recent years, which cause diseases in milk. 

 Thus Schmidt-Mulheim found a micrococcus which occurs in 

 the form of moniliform chains, and causes the milk to become 

 viscous; another species, discovered by Ratz, possesses the 



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