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of my paper on the diseases of beer to renew this discussion. 

 How is it they did not understand that my process for the 

 fabrication of inalterable beer could not exist if beer wort in 

 contact with air could present all the transformations of which 

 they speak? And that work on beer, entirely founded as it 

 is on the discovery and knowledge of some microscopic beings, 

 has it not followed my studies on vinegar, on the mycoderma 

 aceti and on the new process of acetification which I have in- 

 vented? Has not that work been followed by my studies on 

 the causes of wine diseases and the means of preventing them, 

 still founded on the discovery and knowledge of non-spontane- 

 ous microscopic beings? Have not these last researches been 

 followed by the discovery of means to prevent the silkworm 

 disease, equally deducted from the study of non-spontaneous 

 microscopic beings? 



' ' Are not all the researches I have pursued for seventeen 

 years, at the cost of many efforts, the product of the same 

 ideas, the same principles, pushed by incessant toil into con- 

 sequences ever new? The best proof that an observer is in 

 the right track lies in the uninterrupted fruitfulness of his 

 work." 



This fruitfulness was evidenced, not only by Pasteur's per- 

 sonal labours, but by those he inspired and encouraged. Thus, 

 in that same period, M. Gayon, a former student of the Ecole 

 Normale, whom he had chosen as curator, started on some 

 researches on the alteration of eggs. He stated that when 

 an egg is stale, rotten, this is due to the presence and multi- 

 plication of infinitesimally small beings ; the germs of those 

 organisms and the organisms themselves come from the ovi- 

 duct of the hen and penetrate even into the points where the 

 shell membrane and the albumen are formed. " The result 

 is," concluded M. Gayon, "that, during the formation of 

 those various elements, the egg may or may not, according 

 to circumstances, gather up organisms or germs of organisms, 

 and consequently bear within itself, as soon as it is laid, the 

 cause of ulterior alterations. It will be seen at the same 

 time that the number of eggs susceptible of alteration may 

 vary from one hen to another, as well as between the eggs of 

 one hen, for the organisms to be observed on the oviduct rise 

 to variable heights." 



If the organisms which alter the eggs and cause them to 

 rot "were formed," said Pasteur, "by the spontaneous self- 



