320 LOUIS PASTEUR 



more than i per cent, of the total weight of the plums. 

 What better proof than these facts could we have of the 

 existence of a considerable chemical action in the interior 

 of fruit, an action which derives the heat necessary for 

 its manifestation from the decomposition of the sugar 

 present in the cells? Moreover, and this circumstance is 

 especially worthy of our attention, in all these experi- 

 ments we found that there was a liberation of heat, of 

 which the fruits and other organs were the seat, as soon 

 as they were plunged in the carbonic acid gas. This heat 

 is so considerable that it may at times be detected by the 

 hand, if the two sides of the bell, one of which is in con- 

 tact with the objects, are touched alternately. It also 

 makes itself evident in the formation of little drops on 

 those parts of the bell which are less directly exposed 

 to the influence of the heat resulting from the decomposi- 

 tion of the sugar of the cells. 8 



In short, fermentation is a very general phenomenon. 

 It is life without air, or life without free oxygen, or, more 

 generally still, it is the result of a chemical process ac- 

 complished on a fermentable substance capable of pro- 

 ducing heat by its decomposition, in which process the 

 entire heat used up is derived from a part of the heat 

 that the decomposition of the fermentable substance sets 

 free. The class of fermentations properly so called, is, 

 however, restricted by the small number of substances 

 capable of decomposing with the production of heat, and 

 at the same time of serving for the nourishment of lower 

 forms of life, when deprived of the presence and action 

 of air. This, again, is a consequence of our theory, which 

 is well worthy of notice. 



* In these studies of plants living immersed in carbonic acid gas, we have 

 come across a fact which corroborates those which we have already given 

 in reference to the facility with which lactic and viscous ferments, and, 

 generally speaking, those which we have termed the disease ferments of 

 beer, develop when deprived of air, and which shows, consequently, how 

 very marked their aerobian character is. If we immerse beet-roots or tur- 

 nips in carbonic acid gas, we produce well-defined fermentations in those 

 roots. Their whole surface readily permits the escape of the highly acid 

 liquids, and they become filled with lactic, viscous, and other ferments. 

 This shows us the great danger which may result from the use of pits, in 

 which the beet-roots are preserved, when the air is not renewed, and that 

 the original oxygen is expelled by the vital processes of fungi or other 

 deoxidizing chemical actions. We have directed the attention of the manu- 

 facturers of beet-root sugar to this point. 



