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what a very curious phrase that is； if you come to think of it。 The
old alchemists talked of the finest essence of anything as if it had
the same sort of relation to the thing itself as a man's spirit is
supposed to have to his body； and so they spoke of this fine essence of
the fermented liquid as being the spirit of the liquid。 Thus came
about that extraordinary ambiguity of language； in virtue of which you
apply precisely the same substantive name to the soul of man and to a
glass of gin！ And then there is still yet one other most curious piece
of nomenclature connected with this matter； and that is the word
〃alcohol〃 itself； which is now so familiar to everybody。 Alcohol
originally meant a very fine powder。 The women of the Arabs and other
Eastern people are in the habit of tinging their eyelashes with a very
fine black powder which is made of antimony； and they call that
〃kohol；〃 and the 〃al〃 is simply the article put in front of it； so as to
say 〃the kohol。〃 And up to the 17th century in this country the word
alcohol was employed to signify any very fine powder； you find it in
Robert Boyle's works that he uses 〃alcohol〃 for a very fine subtle
powder。 But then this name of anything very fine and very subtle came
to be specially connected with the fine and subtle spirit obtained from
the fermentation of sugar； and I believe that the first person who
fairly fixed it as the proper name of what we now commonly call spirits
of wine； was the great French chemist Lavoisier； so comparatively recent
is the use of the word alcohol in this specialised sense。
So much by way of general introduction to the subject on which I have to
speak to…night。 What I have hitherto stated is simply what we may call
common knowledge； which everybody may acquaint himself with。 And you
know that what we call scientific knowledge is not any kind of
conjuration； as people sometimes suppose； but it is simply the
application of the same principles of common sense that we apply to
common knowledge； carried out； if I may so speak； to knowledge which is
uncommon。 And all that we know now of this substance； yeast； and all
the very strange issues to which that knowledge has led us； have simply
come out of the inveterate habit； and a very fortunate habit for the
human race it is； which scientific men have of not being content until
they have routed out all the different chains and connections of
apparently simple phenomena； until they have taken them to pieces and
understood the conditions upon which they depend。 I will try to point
out to you now what has happened in consequence of endeavouring to
apply this process of 〃analysis；〃 as we call it； this teazing out of an
apparently simple fact into all the little facts of which it is made up；
to the ascertained facts relating to the barm or the yeast； secondly；
what has come of the attempt to ascertain distinctly what is the nature
of the products which are produced by fermentation； then what has come
of the attempt to understand the relation between the yeast and the
products； and lastly； what very curious side issues if I may so call
themhave branched out in the course of this inquiry； which has now
occupied somewhere about two centuries。
The first thing was to make out precisely and clearly what was the
nature of this substance； this apparently mere scum and mud that we
call yeast。 And that was first commenced seriously by a wonderful old
Dutchman of the name of Leeuwenhoek； who lived some two hundred years
ago； and who was the first person to invent thoroughly trustworthy
microscopes of high powers。 Now； Leeuwenhoek went to work upon this
yeast mud； and by applying to it high powers of the microscope； he
discovered 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 conclusionvery creditable to his sagacity； and which has been
confirmed by every observation and reasoning sincethat 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 namewhich I may use without
thinking of it； and which I will therefore give younamely； 〃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 thesethat 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 yeastthat 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 investigationby the help of one's
eye and by the help of the microscopehas 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 directlythat 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
bladde