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Yeast by Thomas Henry Huxley
page 2 of 19 (10%)
bubbles make their appearance in it, and a sort of dirty-looking
yellowish foam or scum collects at the surface; while at the same time,
by degrees, a similar kind of matter, which we call the "lees," sinks
to the bottom.

The quantity of this dirty-looking stuff, that we call the scum and the
lees, goes on increasing until it reaches a certain amount, and then it
stops; and by the time it stops, you find the liquid in which this
matter has been formed has become altered in its quality. To begin
with it was a mere sweetish substance, having the flavour of whatever
might be the plant from which it was expressed, or having merely the
taste and the absence of smell of a solution of sugar; but by the time
that this change that I have been briefly describing to you is
accomplished the liquid has become completely altered, it has acquired a
peculiar smell, and, what is still more remarkable, it has gained the
property of intoxicating the person who drinks it. Nothing can be more
innocent than a solution of sugar; nothing can be less innocent, if
taken in excess, as you all know, than those fermented matters which are
produced from sugar. Well, again, if you notice that bubbling, or, as
it were, seething of the liquid, which has accompanied the whole of
this process, you will find that it is produced by the evolution of
little bubbles of air-like substance out of the liquid; and I dare say
you all know this air-like substance is not like common air; it is not
a substance which a man can breathe with impunity. You often hear of
accidents which take place in brewers' vats when men go in carelessly,
and get suffocated there without knowing that there was anything evil
awaiting them. And if you tried the experiment with this liquid I am
telling of while it was fermenting, you would find that any small
animal let down into the vessel would be similarly stifled; and you
would discover that a light lowered down into it would go out. Well,
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