LOUIS PASTEUR 137 



stantly kept from contact with air and other unsterile 

 substances, no organisms will develop within this nutri- 

 tive liquid no matter how lung the experiment is con- 

 tinued. There was recently exhibited in the United 

 States (1922), a flask of beef broth which it is claimed, 

 correctly no doubt, that Pasteur prepared over fifty 

 years ago. The beef broth is still fresh-looking and 

 clear, never having had the stopper removed from the 

 glass flask in which the broth has been constantly kept. 

 Small living things, like the larger ones which we readily 

 see, come only from other living things of their own 

 kind. The process of treating wines as recommended 

 by Pasteur, known as pasteurization, has since been 

 applied to milk in all civilized countries. 



With previously gained facts in mind, Pasteur pro- 

 ceeded to separate single living yeast plants under his 

 microscope, and then to grow pure cultures from these 

 organisms thus separated. He not only found that 

 they grew as pure culture, but that each kind of small 

 organism produced its own peculiar kind of fermenta- 

 tive products in the nutritive liquids. He thus taught 

 the brewers and wine manufacturers how to separate, 

 grow, and use the particular kinds of living microscopic 

 organisms which produce the kinds of wine and beer 

 that they desired. 



We are not keenly interested in the fact that such dis- 

 coveries taught people how to save the alcoholic in- 

 dustries of France and Germany. What interests us 

 most is that he isolated the microscopic organisms, 

 grew them in pure cultures, and proved that micro- 

 scopic living things, like the larger ones we readily see, 



