SPONTANEOUS GENERATION 91 



significant was the following: Pasteur placed infu- 

 sions of many different organic substances in glass 

 flasks whose neck was drawn out into a long curved 

 tube. After thorough boiling, the air which was 

 sucked in to take the place of the condensed steam 

 after the liquid gradually cooled, would deposit 



Fig. 7. Flask with Curved Neck Used for Keeping Boiled 

 Infusions Supplied with Air Free from Germs 



nearly all its floating matter along the sides of the 

 tube. Although supplied with air, the contents of 

 the flask were found to remain for a long time per- 

 fectly clear and free from decay. If now the flasks 

 were tilted so that some of their contents came in 

 contact with the walls of the tube, putrefaction 

 would invariably be set up. The material in the 

 flask was able to develop life. The only thing 

 lacking was not air but something which was caught 



