o give a sketch of what is doing in the one great province of biology,
with some portions of which my ordinary occupations render me familiar.
But I shall endeavour to put before you the history of the rise and
progress of a single biological doctrine; and I shall try to give some
notion of the fruits, both intellectual and practical, which we owe,
directly or indirectly, to the working out, by seven generations of
patient and laborious investigators, of the thought which arose, more
than two centuries ago, in the mind of a sagacious and observant Italian
naturalist.

It is a matter of everyday experience that it is difficult to prevent
many articles of food from becoming covered with mould; that fruit, sound
enough to all appearance, often contains grubs at the core; that meat,
left to itself in the air, is apt to putrefy and swarm with maggots. Even
ordinary water, if allowed to stand in an open vessel, sooner or later
becomes turbid and full of living matter.

The philosophers of antiquity, interrogated as to the cause of these
phenomena, were provided with a ready and a plausible answer. It did not
enter their minds even to doubt that these low forms of life were
generated in the matters in which they made their appearance. Lucretius,
who had drunk deeper of the scientific spirit than any poet of ancient or
modern times except Goethe, intends to speak as a philosopher, rather
than as a poet, when he writes that "with good reason the earth has
gotten the name of mother, since all things are produced out of the
earth. And many living creatures, even now, spring out of the earth,
taking form by the rains and the heat of the sun."[1] The axiom of
ancient science, "that the corruption of one thing is the birth of
another," had its popular embodiment in the notion that a seed dies
before the young plant springs from it; a belief so widespread and so
fixed, that Saint Paul appeals to it in one of the most splendid
outbursts of his fervid eloquence:--

"Thou fool, that which thou sowest is not quickened, except it die."[2]

[Footnote 1: It is thus that Mr. Munro renders

"Linquitur, ut merito maternum nomen adepta
Terra sit, e terra quoniam sunt cuncta creata.
Multaque nunc etiam exsistant animalia terris
Imbribus et calido solis concreta vapore."

_De Rerum Natura_, lib. v. 793-796.

But would not the meaning of the last line be better rendered "Developed
in rain-water and in the warm vapours raised by the sun"?]