SPONTANEOUS GENERATION. 477 



so that, were I not otherwise informed, I should have found the con- 

 clusion of Mathiole a natural one, namely, that tadpoles are generated 

 in lake-mud by the vivifying action of the sun. 



The checks which experience alone can furnish being absent, the 

 spontaneous generation of creatures quite as high as the frog in the 

 scale of being was assumed for ages to be a fact. Here, as elsewhere, 

 the dominant mind of Aristotle stamped its notions on the world at 

 large. For nearly twenty centuries after him men found no difficulty 

 in believing in cases of spontaneous generation which would now be 

 rejected as monstrous by the most fanatical supporter of the doc- 

 trine. Shell-fish of all kinds were considered to be without parental 

 origin. Eels were supposed to spring spontaneously from the fat ooze 

 of the Nile. Caterpillars were the spontaneous products of the 

 leaves on which they fed, while winged insects, serpents, rats, and 

 mice, were all thought capable of being generated without sexual 

 intervention. 



The most copious source of this life without an ancestry was putre- 

 fying flesh, and, lacking the checks imposed by fuller investigation, 

 the conclusion that flesh possesses and exerts this generative power is 

 a natural one. I well remember when a child of ten or twelve seeing 

 a joint of imperfectly salted beef cut into, and coils of maggots laid 

 bare within the mass. Without a moment's hesitation I jumped to the 

 conclusion that these maggots had been spontaneously generated in 

 the meat. I had no knowledge which could qualify or oppose this 

 conclusion, and for the time it was irresistible. The childhood of the 

 individual typifies that of the race, and the belief here enunciated was 

 that of the world for nearly two thousand years. 



To the examination of this very point the celebrated Francesco 

 Redi, physician to the Grand-dukes Ferdinand II. and Cosmo III. of 

 Tuscany, and a member of the Academy del Cimento, addressed him- 

 self in 1668. He had seen the maggots of putrefying flesh, and re- 

 flected on their possible origin. But he was not content with mere 

 reflection, nor with the theoretic guess-work which his predecessors 

 had founded upon their imperfect observations. Watching meat dur- 

 ing its passage from freshness to decay, prior to the appearance of 

 maggots he invariably observed flies buzzing round the meat and fre- 

 quently alighting on it. The maggots, he thought, might be the half- 

 developed progeny of these flies. 



The inductive guess precedes experiment, by which, however, it 

 must be finally tested. Redi knew this, and acted accordingly. 

 Placing fresh meat in a jar and covering the mouth with paper, he 

 found that though the meat putrefied in the ordinary way, it never 

 bred maggots, while the same meat placed in open jars soon swarmed 

 with these organisms. For the paper cover he then substituted fine 

 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 



