18 PA THOGENIC BA CTERIA.

Three centuries later, in his disquisition upon the
Pythagorean philosophy, we find Ovid defending the
same doctrine:1

"By this sure experiment we know
That living creatures from corruption grow :
Hide in a hollow pit a slaughter'd steer,
Bees from his putrid bowels will appear,
Who, like their parents, haunt the fields and bring
Their honey-harvest home, and hope another spring
The warlike steed is multiplied, we find,
To wasps and hornets of the warrior kind.
Cut from, a crab his crooked claws, and hide
The rest in earth, a scorpion thence will glide,
And shoot his sting ; his tail in circles toss'd
Refers the limbs his backward father lost;
And worms that stretch on leaves their filmy loom
Crawl from their bags and butterflies become.
The slime begets the frog's loquacious race ;
Short of their feet at first, in little space,
With arms and legs endued, long1 leaps they take,
Raised on their hinder part, and swim the lake,
And waves repel; for nature gives their kind,
To that intent, a length of legs behind."

"Not only was the doctrine of spontaneous generation
-of life current among the ancients, but we find it persist-
ing through the Middle Ages, and descending to our own
generation to be an accidental but important factor in
the development of a new branch of science. In 1542,
in his treatise called De Subtilitate, we find Cardan as-
serting that water engenders fishes, and that many ani-
mals spring from fermentation. Van Helmorit gives
special instructions for the artificial production of mice,
and Kircher in his Mundus Subterraneus (chapter l ( De
Panspennia Return") describes and actually figures cer-
tain animals which were produced under his own eyes
by the transforming influence of water on fragments of
sterns from different plants.2

1 Ovid's Metamorphoses, translated by Mr. Dryden, published by Sir Samuel
Garth, London, 1794.

2 See Tyndall: Floating Matter in th? Air.