CHAPTER V. 

 Fermentation. 



Fermentation : a Key to the Whole Position— Chemical Fermentations- 

 Illustrations— Organic Fermentations— Alcoholic Fermentation— Re- 

 sult of Activity of Living Protoplasm — Lactic and Butyric Fermenta- 

 tions — Cagniard Latour — Schwann— Reess— Hansen — Liebig's Theory 

 of Fermentation— High Beer— Low Beer — Method of obtaining Pure 

 Yeasts — Hansen's Classification of the Saccharoniyces — Spore Forma- 

 tion — Film Formation — Characters of Species of Saccharomyces — 

 Metschnikoff 's Monospora — Torulas. 



From what has preceded it will be evident that if any light 

 is to be thrown on the subject of the production of organic 

 poisons in the course of disease a careful study of the subject 

 of fermentation is a necessary preliminary ; for, taken in its 

 widest sense, fermentation includes all those processes in 

 which there is the formation of special ferments and of 

 special products as the result of the life-history of certain 

 vegetable organisms. It is quite as rational to speak of a 

 putrefactive as of an alcoholic fermentation, and we might 

 even go beyond this and speak of a colour fermentation or a 

 disease fermentation, as the organisms by which one or the 

 other is started, and the conditions under which they are 

 carried on, have many features in common, and, in fact, do 

 not differ more than do the causes and conditions that are 

 already known as associated with true alcoholic fermenta- 

 tions. 



Fermentation consists, essentially, in the breaking up of 

 chemical compounds, the molecules of which they are com- 

 posed being separated from one another for a brief period, 

 and then allowed to combine and form simpler and more 

 stable compounds. Owing to the setting free of such energy 

 as has been stored up in the highly complex fermentable 

 substance which is no longer required to maintain the 

 high level of combination, a certain proportion of this 

 energy is released in the form of heat, the temperature of 



