26 president's address. 



sion of glucose into alcohol and carbonic acid gas, the so-called 

 alcoholic fermentation, will serve for this purpose. The ferment- 

 ation of sweet liquids has attracted some attention from every 

 generation of natuial philosophers. The slow accumulation of 

 real knowledge is illustrated by the fact that we have no record 

 of any observation, current in our descriptions of the process, 

 before the end of the seventeenth century. Until that date, it 

 was thought that the spirit of the liquid made its escape in the 

 heaving struggle of the bubbling liquid. Van Helmont identi- 

 fied the gas vinorum escaping from the fermenting liquid with 

 the gas sylvestre found in woods and caves or freed from marble 

 by acids. Becher observed that only sweet liquids underwent 

 this change. Leeuwenhoek, indeed, saw the countless myriads 

 of particles with his microscope, but did not connect their 

 presence with fermentation. Another century rolled by before 

 Lavoisier made use of the balance, and discovered that sugar is 

 split into approximately equal parts of alcohol and carbon 

 dioxide. Cagniard Latour, using a better microscope, noted in 

 1831 that the yeast particles multiplied by budding, and that 

 they were living plants. He suggested that the growth of these 

 plants occasioned fermentation. Theodore ISchwann came to 

 the conclusion that fermentation was brought about by the 

 entrance of living micro-organisms into the fermenting liquid. 

 Liebig denied the relation of the yeast-plants to the process of 

 fermentation. He drew a humorous picture of the yeast cell 

 equipped with its still and condenser, furnishing alcohol and 

 blowing off gas. He asked whether such scenes were really 

 visible through the microscope. Later he accepted the yeast- 

 cell as a living plant, but affirmed that its presence had nothing 

 to do with the occasioning of fermentation. Pasteur showed 

 that the sugar was split in the body of the yeast-plant, and 

 attributed this decomposition to the vital powers of the living 

 cell. Buchner demonstrated that an unorganised ferment could 

 be separated from crushed yeast-cells, and that this lifeless body 

 decomposed glucose into alcohol and carbon dioxide. It has 

 taken more than two hundred and fifty years to gain this infor- 

 mation. To those of you who know little of fermentation, our 



