PASTEUR, KOCH, AND OTHERS 279 



taneous generation. To approach this question from the 

 experimental side was to do a great service to science. 



The experiments of Redi were simple and homely. He 

 exposed meat in wide-mouthed flasks, some of which were left 

 uncovered, some covered with paper, and others with a fine 

 Neapolitan veil. The meat in all these vessels became 

 spoiled, and flies, being attracted by the smell of decaying 

 meat, laid eggs in that which was exposed, and there came 

 from it a large crop of maggots. The meat in the covered 

 flasks also decayed in a similar manner, without the appear- 

 ance of maggots within it; and in those vessels covered by 

 veiling the flies laid their eggs upon the netting. There they 

 hatched, and the maggots, instead of appearing in the meat, 

 appeared on the surface of the covering. From this Redi con- 

 cluded that maggots arise in decaying meat from the hatching 

 of the eggs of insects, but inasmuch as these animals had been 

 supposed to arise spontaneously within the decaying meat, the 

 experiment took the ground from under that hypothesis. 



He made other observations on the generation of insects, 

 but with acute scientific analysis never allowed his conclusions 

 to run ahead of his observations. He suggested, however, 

 the probability that all cases of the supposed production of life 

 from dead matter were due to the introduction of living germs 

 from without. The good work begun by Redi was confirmed 

 and extended by Swammerdam (1637-1681) and Yallisnicri 

 (1661-1730), until the notion of the spontaneous origin of u in- 

 forms of life visible to the unaided eye was banished from 

 the minds of scientific men. 



Redi (Fig. 89) was an Italian physician living in Arentino, 

 distinguished alike for his attainments in literature and for 

 his achievements in natural science. He was medical adviser 

 to two of the grand dukes of Tuscany, and a member of the 

 Academy of Crusca. Poetry as well as other literary com- 

 positions shared his time with scientific occupation-. His 



