1012] on Lord Lixter. 551 



papers to the French Academy * recognized that alcoholic fermenta- 

 tion was due to the presence of a living organism. He found that 

 grape-juice contained numerous globular bodies which he considered 

 to be of vegetable nature, and which reproduced themselves by bud- 

 ding. These were always present when fermentation occurred, and 

 in their absence fermentation did not take place. 



This microscopic " fungus," which he found in yeast, appeared to 

 l)e the essential agent in the production of fermentation, and he 

 attributed the resolution of sugar into alcohol and carbonic acid to 

 its influence. 



In the following year Schwann of Berlin f published the results of 

 an investigation into the causes of putrefaction, in the course of 

 which he also independently discovered the yeast plant. 



What was of equal importance, he demonstrated that a putrescible 

 fluid, such as a decoction of meat, could be freely and indefinitely 

 exposed to the action of pure air— air free from dust and organisms 

 — without putrefaction ensuing in it. 



Those views of Schwann that putrefaction is due to the action 

 of living organisms, and those of Cagniard-Latour showing that 

 fermentation is caused Ijy the yeast plant, did not, for more than 

 thirty years, yield the fruit which, viewed from present knowledge, 

 might have been expected from them. The bearing which these 

 discoveries might have had on other fields was hindered by the fact 

 that they were not generally known— the dissemination of scientific 

 knowledge being slower in those days — and also by the fact that 

 there were many who refused to accept the existence of organisms 

 as the cause of fermentation or putrefaction. They chose to believe, 

 with Baron Liebig, that chemical action was alone sufficient to cause 

 the changes which were seen in f ermentive and putrefying fluids, and 

 that the mere exposure to air was sufficient to produce the effect. 



Liebig held that the ferment was a nitrogenous substance under- 

 going putrefaction, and that it converted the oxygen of the air into 

 carbonic acid. 



The demonstration of Schwann, which showed that putrefaction 

 could be prevented as long as the putrescible body was exposed to 

 pure air only, was either unnoticed or was not believed. 



Cagniabd-Latour and Schwann's Observations 



CONFIRMED BY PaSTEUR, 1858. 



Pasteur, when in the University of Lille, had abundant oppor- 

 tunity of studying alcoholic fermentation, as alcohol was the staple 



* Annales de Chimie et de Physique, t. Ixviii. 2nd series, p. 206, 1838. 

 Comptes Rendus, t. iv. p. 905, 1837. 



t Poggendorf Annalen, xli. p. 184, 1837. 



