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,