INTRODUCTION. 19

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About 1668, Francesco Redi seems to have been the
first to doubt that the maggots familiar in putrid meat
arose de novo: " Watching meat in its passage from
freshness to decay, prior to the appearance of maggots,
he invariably observed flies buzzing around the meat and
frequently alighting on it. The maggots, he thought,
might be the half-developed progeny of these flies.
Placing fresh meat in a jar covered with paper, he found
that although the meat putrefied in the ordinary way,
it never bred maggots, while meat in open jars soon
swarmed with these organisms. For the paper he sub-
stituted fine wire gauze, through which the odor of the
meat could rise. Over it the flies buzzed, and on it they
laid their eggs, but the meshes being too small to per-
mit the eggs to fall through, no maggots generated in
the meat; they were, on the contrary, hatched on the
gauze. By a series of such experiments Redi destroyed.
the belief in the spontaneous generation of maggots in
meat, and with it many related beliefs."

It was not long before Leeuwenhoek, Vallismeri,
Swammerdan, and others, following the trend of Redi's
work, contributed additional facts in favor of his view,
and it may safely be asserted that ever since the time
of this eminent man the tide of scientific opinion has
turned more and more strongly against the idea that
life is spontaneously generated.

About this time (1675) one whose name has been
already mentioned, Anthony van Leeuwenhoek, and WT!IO
is justly called the u Father of microscopy," came into
prominence. An optician by trade, Leeuwenhoek devoted
much time to the perfection of the compound micro-
scope, which was just coming into use. The science of
optics, however, was not sufficiently developed to enable
him to overcome the errors of refraction, and after the
loss of much time he turned to the simple lens, using- it
in so careful and remarkable a manner as to be able
to record his observations in one hundred and twelve
contributions to the Philosophical Transactions. Leeu-