240 



HOW LIFE BEGAN 



generation. He had noticed that flies were usually seen about 

 meat, and thought that there might be some connection between 



flies and the mag- 

 gots which were 

 .supposed to rise 

 spontaneously 

 from the meat. 

 As a result of 

 this observation, 

 he put some meat 

 in three different 

 jars. One of 

 these jars was 

 left uncovered, 



Using this simple experiment, Redi started a discussion which ended 

 with the overthrow of the belief of spontaneous generation. 



one was covered with parchment, and the third was covered with 

 a fine gauze. In the first jar, the meat spoiled; maggots and, 

 later, flies appeared in the mass. In the parchment-covered jar, the 

 meat putrefied, but no maggots appeared. In the gauze-covered 

 jar, the meat putrefied, and flies laid eggs upon the gauze. These 

 eggs produced maggots which later developed into flies. Therefore, 

 Redi concluded that maggots of flies could not have originated 

 from decayed meat alone, but from fertile eggs laid there by other 

 flies that were attracted by the odor. NO eggs were found near 

 the second jar as the parchment kept the odor from escaping. 

 Redi decided that life must come from preexisting life. He per- 

 formed other experiments and concluded that in cases when life 

 seemed to have been produced from dead matter there had always 

 been the introduction of material from living organisms. 



Leeuwenhoek's contribution. After Redi's experiments, the 

 question of the origin of life was again discussed. Many people 

 were willing to accept the explanation that the living things they 

 could see, such as rats and frogs, must originate from other living 

 things. In 1687, Leeuwenhoek perfected the microscope and dis- 



