43 4 THEHISTORYOFBIOLOGY 



of the retort was melted together and after some days there was found in the 

 fluid an abundant vegetation of micro-organisms. Their origin was thus 

 proved; these creatures had existed in atmospheric dust in a dried state. On 

 the other hand, a saccharine solution boiled in a retort the neck of which 

 was melted together in the course of boiling could be preserved for any 

 length of time without changing. Pouchet tried by various means to dis- 

 credit these experiments; he tried to prove that the organisms cannot stand 

 being dried, that they do not exist scattered in the air as Pasteur declares, 

 that milk becomes sour in spite of being boiled. Space forbids our following 

 this dispute in all its phases — how both parties collected air on high 

 mountains with a view to proving their arguments on that evidence; how 

 Pasteur found that certain organisms can endure heating up to the boiling 

 point of water without perishing (which explains how it is that boiled 

 milk turns sour); how he thought out a whole series of ingenious apparatus 

 to prove his statement that the fermenting organisms always originate in 

 the outer air and that the boiling of the experimental fluids and the heating 

 of the air which comes into contact with them, infallibly exclude the exist- 

 ence of organic life in them. The two antagonists were allowed to carry out 

 their experiments before the French Academy of Science, and Pasteur at once 

 succeeded in convincing some of its foremost members — Milne-Edwards 

 and Claude Bernard, and the chemist Chevreul. Pouchet likewise had his 

 supporters, and especially among the scientifically educated and half-educated 

 public he gained many adherents who regarded spontaneous generation as a 

 "philosophical necessity," indispensable for a natural-scientific explanation 

 of the origin of life, which Pasteur, faithful Catholic as he was, naturally felt 

 himself compelled to explain dogmatically. Thus argument opposed argu- 

 ment, and party faced party. In these circumstances the solution of the prob- 

 lem would never have become possible had not Pasteur been able to put his 

 ideas into practice on a large scale. During the succeeding years he invented 

 his well-known methods of preserving milk by "Pasteurizing" — that is, 

 by heating — of improving the manufacture of wine and beer by controlling 

 the conditions of fermentation, of securing immunity from the silk-worm 

 disease and chicken cholera by eliminating the micro-organisms that produce 

 them. These discoveries, however, belong to the next period, as also the de- 

 velopment and perfecting of bacteriology and fermentation research achieved 

 by other investigators — Koch, Hansen, and many others. Finally Pasteur's 

 views on the origin of the micro-organisms received splendid practical con- 

 firmation as a result of the development of modern medicine: antiseptics and 

 aseptics in surgery, disinfection, and the treatment of infectious disease. 

 Owing to these facts, which found fresh confirmation daily, spontaneous 

 generation has entirely ceased to exist as a possibility to be reckoned with in 

 modern biology, nor does it come into serious question when we have to 



