SPONTANEOUS GENERATION 9 



were something after this order: An old piece of cloth and 

 some seed corn were to be placed in a jar, and after standing 

 the proper length of time would surely produce mice. Kir- 

 cher actually figures animals claimed to have been produced 

 under his own eye. 



During this period the theory of spontaneous generation 

 was universally accepted. In the seventeenth century 

 Alexander Ross, commenting on Sir Thomas Brown's doubt 

 as to whether mice were bred by putrefaction, says : " To 

 question this is to question reason, sense, and experience." 



Second Period. The first experiments which seriously 

 questioned this theory were those devised by Francisco Redi, 

 in 1668. Redi was a physician to the Grand Duke of Tuscany. 

 In watching meat pass from the fresh to the putrid state he 

 noticed that before the maggots appeared, which were com- 

 monly supposed to be the result of spontaneous generation, 

 flies could invariably be seen buzzing about the meat. The 

 idea occurred to him that these maggots might be the progeny 

 of the flies, and he put some meat in a jar and covered the 

 mouth of' the jar with a piece of paper, and found that although 

 the meat putrefied maggots did not appear. Later the paper 

 was replaced by gauze. Meat protected in this way would 

 putrefy, but would not develop maggots. The flies would 

 deposit their eggs on the gauze, which would not allow them 

 to reach the meat. This first serious blow to the theory of 

 spontaneous generation was followed by other conclusive 

 experiments by Swammerdam, Vallisnieri, and others, so 



