lO BACTERIA, YEASTS, AND MOLDS 



suitable food, no matter how carefully all microorganisms 

 had been excluded from it. 



Scientists did not regard Appert's methods of canning food 

 as being scientific proof of their point, however. It was not 

 tfll about i860 that proof to suit the Needham school was 

 furnished. One of those who helped furnish this proof was 

 Pasteur, the founder of bacteriology, an undoubted genius, 

 and such a genius that authors never tire of writing about 

 him. We must give more than passing attention to his work, 

 of which his refutation of spontaneous generation was a very 

 small part. He accomplished this in a very simple and yet 

 conclusive manner. He made a glass flask with a long neck 

 drawn out into a long and crooked tube. The contents 

 of such a flask were exposed to the air, which could pass 

 into the flask without even having to pass through a filter. 

 Yet no microscopic particles, either living or dead, could be 

 blown through the long crooked neck, and any such object 

 falling into the end of it would surely lodge at the bottom 

 of one of the bends. Pasteur showed that, if the contents 

 of such a flask were heated hot enough, they could be kept 

 free from microorganisms for a long period; although, on 

 cooling, the contraction of the air in the flask must suck in 

 a good quantity of air from the outside. Some of these 

 flasks prepared by Pasteur are still preserved, and the con- 

 tents are still sterile after these many years. He also 

 showed that if the neck of a flask were broken off short 

 so that dust particles could settle into it, the contents 

 would become cloudy in a very few days and would show 

 the presence of microscopic organisms. After this demon- 

 stration by Pasteur no one was able to convince scientists 

 that spontaneous generation was possible. 



