hesis that all living matter
has sprung from pre-existing living matter, came from a contemporary,
though a junior, of Harvey, a native of that country, fertile in men
great in all departments of human activity, which was to intellectual
Europe, in the sixteenth and seventeenth centuries, what Germany is in
the nineteenth. It was in Italy, and from Italian teachers, that Harvey
received the most important part of his scientific education. And it was
a student trained in the same schools, Francesco Redi--a man of the
widest knowledge and most versatile abilities, distinguished alike as
scholar, poet, physician, and naturalist--who, just two hundred and two
years ago, published his "Esperienze intorno alla Generazione degl'
Insetti," and gave to the world the idea, the growth of which it is my
purpose to trace. Redi's book went through five editions in twenty years;
and the extreme simplicity of his experiments, and the clearness of his
arguments, gained for his views, and for their consequences, almost
universal acceptance.

Redi did not trouble himself much with speculative considerations, but
attacked particular cases of what was supposed to be "spontaneous
generation" experimentally. Here are dead animals, or pieces of meat,
says he; I expose them to the air in hot weather, and in a few days they
swarm with maggots. You tell me that these are generated in the dead
flesh; but if I put similar bodies, while quite fresh, into a jar, and
tie some fine gauze over the top of the jar, not a maggot makes its
appearance, while the dead substances, nevertheless, putrefy just in the
same way as before. It is obvious, therefore, that the maggots are not
generated by the corruption of the meat; and that the cause of their
formation must be a something which is kept away by gauze. But gauze will
not keep away aeriform bodies, or fluids. This something must, therefore,
exist in the form of solid particles too big to get through the gauze.
Nor is one long left in doubt what these solid particles are; for the
blowflies, attracted by the odour of the meat, swarm round the vessel,
and, urged by a powerful but in this case misleading instinct, lay eggs
out of which maggots are immediately hatched, upon the gauze. The
conclusion, therefore, is unavoidable; the maggots are not generated by
the meat, but the eggs which give rise to them are brought through the
air by the flies.

These experiments seem almost childishly simple, and one wond