dge 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 them--have
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 t