Yeast | Page 6

that it was no mere mud such as you might
at first suppose, but that it was a substance made up of an enormous
multitude of minute grains, each of which had just as definite a form as
if it were a grain of corn, although it was vastly smaller, the largest of
these not being more than the two-thousandth of an inch in diameter;
while, as you know, a grain of corn is a large thing, and the very
smallest of these particles were not more than the seven-thousandth of
an inch in diameter. Leeuwenhoek saw that this muddy stuff was in
reality a liquid, in which there were floating this immense number of
definitely shaped particles, all aggregated in heaps and lumps and some
of them separate. That discovery remained, so to speak, dormant for
fully a century, and then the question was taken up by a French
discoverer, who, paying great attention and having the advantage of
better instruments than Leeuwenhoek had, watched these things and
made the astounding discovery that they were bodies which were
constantly being reproduced and growing; than when one of these
rounded bodies was once formed and had grown to its full size, it
immediately began to give off a little bud from one side, and then that
bud grew out until it had attained the full size of the first, and that, in
this way, the yeast particle was undergoing a process of multiplication
by budding, just as effectual and just as complete as the process of
multiplication of a plant by budding; and thus this Frenchman,
Cagniard de la Tour, arrived at the conclusion--very creditable to his
sagacity, and which has been confirmed by every observation and
reasoning since--that this apparently muddy refuse was neither more
nor less than a mass of plants, of minute living plants, growing and
multiplying in the sugary fluid in which the yeast is formed. And from
that time forth we have known this substance which forms the scum
and the lees as the yeast plant; and it has received a scientific

name--which I may use without thinking of it, and which I will
therefore give you--namely, "Torula." Well, this was a capital
discovery. The next thing to do was to make out how this torula was
related to the other plants. I won't weary you with the whole course of
investigation, but I may sum up its results, and they are these--that the
torula is a particular kind of a fungus, a particular state rather, of a
fungus or mould. There are many moulds which under certain
conditions give rise to this torula condition, to a substance which is not
distinguishable from yeast, and which has the same properties as
yeast--that is to say, which is able to decompose sugar in the curious
way that we shall consider by-and-by. So that the yeast plant is a plant
belonging to a group of the Fungi, multiplying and growing and living
in this very remarkable manner in the sugary fluid which is, so to speak,
the nidus or home of the yeast.
That, in a few words, is, as far as investigation--by the help of one's eye
and by the help of the microscope--has taken us. But now there is an
observer whose methods of observation are more refined than those of
men who use their eye, even though it be aided by the microscope; a
man who sees indirectly further than we can see directly--that is, the
chemist; and the chemist took up this question, and his discovery was
not less remarkable than that of the microscopist. The chemist
discovered that 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