CHAPTER XXV 



HOW 

 LIFE BEGAN 



Louis Pasteur. 



His flask of nutritive fluid. 



What was one of the ancient ideas of the origin of life? How and 

 by whom was the theory of spontaneous generation disproved? How 

 do some scientists of to-day explain the origin of life ? 



The ancient idea of the origin of life. At the time of Aristotle, 

 and for many centuries following the work of this Greek teacher 

 and philosopher, there was a theory, supported by scientific men, 

 concerning the origin of life, and known as spontaneous generation. 

 According to this theory, living things rose spontaneously from 

 non-living materials. Bees were supposed to come from the dead 

 bodies of young bulls ; young rats could be made to appear in a 

 box containing soiled rags and wheat grains ; horsehairs in water 

 would turn to worms ; and mice and other animals came from the 

 mud of the river Nile. Dew was supposed to give rise to insects, 

 and rain would bring frogs. Instead of investigating whether 

 this was the way life originated, people speculated that it must be 

 true and scorned anyone who doubted it. The unbelievers were 

 told to go to the Nile and see the fields swarming with mice begot 

 from the mud which was deposited when the Nile overflowed its 

 banks. 



Experimental evidence. Francesco Redi, an Italian physician, 

 (1629-1694), was one of the first persons to conduct a series of 

 experiments to test, scientifically, the theory of spontaneous 



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