STUDIES ON FERMENTATTOX, 59 



gooseberry must, previously rendered unalterable by boiling. 

 These tubes we closed again with all possible precautions, using 

 corks which had been passed through the flame of a spirit-lamp 

 and carried them to our laboratory, where we left them to 

 themselves. Some days afterwards we saw diverse fungoid 

 growths appear in most of the tubes, but not one of them then, 

 or subsequently^, presented the least appearance of fermentation. 

 The germs of yeast at that period of the year did not exist 

 either upon the woody part of the bunch, or upon the grapes. 

 In Chapter V. we shall return to observations on this subject. 



§ IV. — WoKT AND Must Exposed to Common Aik. 



If the principles which we have laid down possess all the 

 value that we attribute to them, if the cause of change in 

 natural or artificial organic liquids does not exist in those 

 liquids themselves, if change considered in itself depends upon 

 the nature and number of the particles of dust in various places, 

 if it is, besides, radically affected by the composition of the 

 liquids, it must necessarily follow that wort or must, whilst, 

 under certain circumstances of exposure to air, it remains 

 absolutely free from life and its results, will, under other 

 circumstances, give rise to a variety of organisms and their 

 corresponding fermentations. This is, in fact, the lesson which 

 direct proofs will teach us. Before entering upon these new 

 observations in detail, we must call the reader's attention to the 

 difficulty, as experience has shown, of interpreting correctly the 

 facts connected with the spontaneous impregnations of organic 

 liquids. 



Gay-Lussac crushed some grapes under a bell-jar filled with 

 mercury, after having washed them in hydrogen, to expel the 

 air adhering to the grapes and the sides of the jar. Having 

 waited for several weeks without detecting any signs of fermen- 

 tation, he introduced some bubbles of oxygen, and fermentation 

 showed itself the following day. Gay-Lussac concluded that 



