the yeast plant being composed of a sort of bag, like a bladder, inside
which is a peculiar soft, semifluid material--the chemist found that
this outer bladder has the same composition as the substance of wood,
that material which is called "cellulose," and which consists of the
elements carbon and hydrogen and oxygen, without any nitrogen. But then
he also found (the first person to discover it was an Italian chemist,
named Fabroni, in the end of the last century) that this inner matter
which was contained in the bag, which constitutes the yeast plant, was a
substance containing the elements carbon and hydrogen and oxygen and
nitrogen; that it was what Fabroni called a vegeto-animal substance, and
that it had the peculiarities of what are commonly called "animal
products."

This again was an exceedingly remarkable discovery. It lay neglected
for a time, until it was subsequently taken up by the great chemists of
modern times, and they, with their delicate methods of analysis, have
finally decided that, in all essential respects, the substance which
forms the chief part of the contents of the yeast plant is identical
with the material which forms the chief part of our own muscles, which
forms the chief part of our own blood, which forms the chief part of
the white of the egg; that, in fact, although this little organism is
a plant, and nothing but a plant, yet that its active living contents
contain a substance which is called "protein," which is of the same
nature as the substance which forms the foundation of every animal
organism whatever.

Now we come next to the question of the analysis of the products, of
that which is produced during the process of fermentation. So far back
as the beginning of the 16th century, in the times of transition between
the old alchemy and the modern chemistry, there was a remarkable man,
Von Helmont, a Dutchman, who saw the difference between the air which
comes out of a vat where something is fermenting and common air. He was
the man who invented the term "gas," and he called this kind of gas "gas
silvestre"--so to speak gas that is wild, and lives in out of the way
places--having in his mind the identity of this particular kind of air
with that which is found in some caves and cellars. Then, the gradual
process of investigation going on, it was discovered that this
substance, then called "fixed air," was a poisonous gas, and it was
finally identified with that kind of gas which is