Page 74 - Ethel D. Hume - Bešam ili Paster: Izgubljeno poglavlje u istoriji biologije

THE SOLUBLE FERMENT 7i

without the juice it secretes, so yeast could not change
sugar without a soluble ferment secreted by its cells.
On p. 70 of Les Microzymas, Professor Bechamp com-
mences an account of some of the experiments he under-
took in this connection. Here may be found the description
of an experiment with thoroughly washed and dried beer-
yeast, which was mixed with a little more than its weight
of cane-sugar and the mixture carefully creosoted, the
whole becoming soft and by degrees completely fluid.
Bechamp provides a full explanation of the action. He
shows that the yeast cell is like a closed vesicle, or a con-
tainer enclosing a content, and that it is limited in space by
a membranous envelope. In the dried state, in which he
made use of it for his experiment, it yet contained more
than 70 per cent of water, no more perceptible to touch
than the amount, on an average 80 per cent of the body-
weight, contained in the human body. He explains how
the living yeast, in its natural state, on contact with water,
allows nothing of its content to escape except excretory
products, but, in contact with the sugar, it is, as it were,
irritated and the enveloping membrane permits the escape
of water with certain other materials held in solution, and
it is this fluid that liquefies the mixture of yeast and sugar.
The escape of the fluid Bechamp shows to be due to the
physical process osmosis, by which a solution passes through
a permeable membrane. Thus having obtained his liquid
product he diluted it with water and left it to filter.
Meanwhile, Bechamp performed another experiment;
namely, he dissolved a small piece of cane-sugar in water
and found that no change was produced when this was
heated with alkaline copper tartrate. He then took
another small piece of sugar and heated it to boiling point
with very dilute hydrochloric acid; he neutralised the
acid with caustic potash and made the solution alkaline,
he then added his copper reagent and heated it, where-
upon reduction took place, a precipitate being produced
which was at first yellow and then red. By means of the
acid the sugar had been inverted, that is to say, trans-