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same may happen when instead of Bacterium butyricus, other 

 microbes predominate in butter. In all processes of fer- 

 mentation, e.g.) fermentation of indigo, of wine, of cheese 

 &c., it should be seen that the proper microbe has full 

 play, and not another. These proper microbes can be 

 separately cultivated in sterilized bottles of broth, gelatine 

 &c., plugged with sterilized cotton wool. The desired 

 fermentation can be expedited by the addition of these 

 cultures. This is a subject of great economic importance, 

 and the wine manufacturers of Europe are indebted to 

 Pasteur for teaching them the secret of proper brewing of 

 win, s and beers. Substances in which microbes have grown 

 when they become dry and powdery get lifted up by currents 

 of air, and dust laden with spores of microbes thus gets 

 disseminated through air. If industrial fermentations, such 

 as fermentation of indigo, wine, butter, cheese etc., have to 

 depend upon the right kinds of microbes dropping into the 

 indigo or wine vat etc., uncertain results are inevitable. 

 Pure cultures of the right kinds of microbe should be added 

 to enhance the right kind of fermentation. 



1.295. Culture-media. Meat-broth, a mixture of gelatine 

 and agar-agar, boiled potato, milk, blood-serum, or decoction 

 of plants, is first sterilized at a temperature of 239F., for a 

 quarter of an hour and then used for cultivation of microbes. 

 Bacteria require for their nourishment albuminoid matter, 

 carbon (which they can derive from the culture-medium) and 

 ash constituents, i.e., K, Na, Ca, Mg, Fe, P, S, and Cl. 

 All these substances being naturally present in milk and 

 in blood-serum, in a soluble and readily assimilable condition, 

 they are excellent natural media for the growth of bacteria. 

 The culture-medium must not be too acid nor alkaline. 



1.296. Mounting of Bacteriological slides. When epi- 

 demic is feared, or the presence of pathogenic organisms 

 are suspected in milk, butter, blood, or any other fluid 

 or semifluid substance, microscopic examination of the sub- 



