80 MICROBES, FERMENTS, AND MOULDS. 
spores may be produced (Fig. 46). It is rather 
difficult 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 the 
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 
