80 MICROBES, FERMENTS, AND MOULDS. 



spores may be produced (Fig. 46). It is rather 

 diflScult to perform the experiment with success ; the 

 ferment must be frequently washed with distilled 

 water, as it may otherwise putrefy, instead of fruc- 

 tifying (Schutzenberger). 



Let us briefly describe the process by which tlie 

 fermented liquor termed beer is obtained. The barley 

 which constitutes its essential principle does not 

 contain sugar ; but when it has germinated it contains 

 a substance termed diastase, under the influence of 

 which the starch of barley can be converted into 

 glucose. 



The barley, which has been moistened in order to 

 make it swell and germinate, is spread in a thin layer 

 on hurdles, at a temperature of about 15° : this opera- 

 tion is called malting. It is generally performed in 

 spring, in order to ensure the necessary warmth 

 and moisture, and March beer is considered the best. 

 When the sprout attains to two-thirds of the length 

 of the grain, germination is arrested by drying the 

 grains on a stove, and they are then ground to 

 powder and become malt. This malt is then steeped 

 in water at the temperature of 60° and by the 

 action of the diastase the starch becomes glucose. 

 This saccharine fluid or wort is boiled with hops, 

 which are now added, not only to give a bitter and 

 aromatic taste, but also to preserve it. This infusion 

 of malt and hops is concentrated and cooled, and beer- 

 yeast, the product of previous operations, is added in 



