SPONTANEOUS FERMENTATION OF SWEET FRUITS 19 



fermentation might be defined as a decomposition of organic substances by the 

 agency of fungi. 



The researches of the past fifteen years (1880-1895) have, however, neces- 

 sitated considerable modifiations of the words italicised. The study of the 

 bacteria of the nodules of leguminous plants has taught us that their main func- 

 tion consists in bringing about the combination of free atmospheric nitrogen : 

 hence their action is not a decomposing (analytical) one, but is synthetic or 

 constructive, so that in respect of these organisms our definition will have to 

 include the word " transformation." The adjective " organic " may still remain, 

 since the microbes in question require organic nutriment in addition to the free 

 nitrogen. 



We shall, however, find ourselves constrained to reject this latter term when 

 we come to the study of nitrification, and make the acquaintance of another group 

 of microbes able to dispense with organic nutriment, and indeed thriving and 

 acting most effectively only when surrounded by inorganic substances exclusively. 

 Consequently we arrive at the following final and conclusive definition : Fermen- 

 tation is a decomposition or transformation of substances of various kinds 

 brought about by the vital activity of fungi. 



20. The So-called Spontaneous Fermentation of Sweet Fruits. 



The point of the preceding definition lies in the concluding words, which 

 restrict the term fermentation to such decompositions or transformations as 

 are produced by the vital activity of fungi. It is, however, not impossible for 

 similar decompositions to be effected in other ways, especially by the aid of other 

 vegetable cells differing from fungi. An example of such a reaction, resembling 

 fermentation but not induced by fungi, is afforded by the so-called spontaneous 

 fermentation of fruit. 



The first reliable data with regard to this phenomenon were collected by 

 LECHARTIEB and BELLAMY (I.) in 1869, all previous observations having to be 

 disregarded because they do not show that the activity of yeast-cells was pre- 

 cluded. Starting with the notes made in 1821 by their compatriot BERARD (I.), 

 these French investigators succeeded in establishing the fact that sweet fruits, 

 e.g. cherries, when kept in an uninjured condition and free from yeast in an 

 atmosphere of carbon dioxide, consume a portion of their sugar content, gaseous 

 carbon dioxide being evolved in the process and alcohol formed. The presence 

 of this latter substance in the cells of the fruit substance can be proved by 

 distillation, as much as one per cent, by weight having been detected in this 

 way. 



PASTEUR (IV. and V.) also studied this phenomenon, which he employed as 

 one of the main buttresses of his previously formed theory asserting fermentation 

 to be a universal phenomenon, not dependent on certain organisms, but occur- 

 ring in every living vegetable cell debarred from a supply of oxygen. This 

 spontaneous fermentation appeared to form a striking proof of the correctness of 

 this theory, but the hopes thereby raised proved vain, since Pasteur was himself 

 the one to discover that alcohol (though in merely minute quantities) is also 

 formed in fruits when they are exposed to the air. 



21. Decompositions Effected by Light and Air. 



To the chemist who is obliged to store in the dark and in properly stoppered 

 receptacles various inorganic reagents and normal solutions which he desires to 

 maintain in an unaltered condition it will not be surprising to learn that sterile 



