ADDRESS. IxXV 



tecnth 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 Eedi — a man of the widest knowledge and most versa- 

 tile abilities, distinguished alike as scholar, poet, physician, and natru'alist, — 

 who, just two hundred and two years ago, pubhshed his ' Esperienze intorno 

 alia Generazione degl' Insetti,' and gave to the world the idea, the growth of 

 which it is my purpose to trace. Eedi's book went through five editions in 

 twenty years ; and the extreme simplicity of his experiments, and the clear- 

 ness of his arguments, gained for his views, and for their consequences, 

 almost universal acceptance. 



Eedi did not trouble himself much with speculative considerations, but 

 attacked particular cases of what was supposed to be " spontaneous genera- 

 tion " 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 clead 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 cor- 

 ruption of the meat ; and that the cause of their formation must be a some- 

 thing 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 sohd 

 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 wonders how it 

 was that no one ever thought of them before. Simple as they are, however, 

 they are worthy of the most careful study, for every piece of experimental 

 work since done, in regard to this subject, has been shaped upon the model 

 furnished by the Italian philosopher. As the results of his experiments 

 were the same, however varied the nature of the materials he used, it is 

 not wonderful that there arose in Eedi's mind a presumption, that in all 

 such cases of the seeming production of life from dead matter, the real ex- 

 planation was the introduction of living germs from without into that dead 

 matter*. And thus the hypothesis that living matter always arises by the 



* " Pure contentandomi sempre in questa ed in ciascuna altra cosa, da ciascuno piu 

 savio, la dove io dii'ettuosamente parlassi, esser corretto ; non tacero, che per molte osser- 

 vazioni molti volti da me fatte, rvA sento inclinato a credere cbe la terra, da quelle prime 

 piante, e da quel primi animali in poi, che ella nei primi giorni del mondo produsse per 

 comandemento del sovrano ed omnipotente Fattore, non abbia mai piii prodotto da se 

 medesima ne erba ne albero, ne animale alciino perfetto o imperfetto cbe ei se fosse ; e 

 che tutto quello, che ne' tempi trapassati e nato e che era nascere in lei, o da lei veggiamo, 

 venga tutto dalla semenza reale e vera delle j)iante, e degli animali stessi, i quali col 

 mezzo del proprio seme la loro spezie conservano. E se bene tutto giorno scorghiamo 

 da' cadaveri degli animali, e da tutte quante le maniere dell' erbe, e de' fiori, e dei frutti im- 

 putriditi, e corrotti nascere vermi infiniti — 



Nonne vides qurecunque mora, fluidoquo calore 

 Corpora tabescunt in parra auimalia verti — 

 Io mi sento, dice, inclinato a credere cbe tutti quei vermi si generino dal seme 



/2 



