i 4 THEORIES OF FERMENTATION. 



longer required. With regard to the nature of this stimulating 

 action he was, however, unable to report more definitely. 



Among the observations which led Gay-Lussac to adopt this 

 view, mention may be made of one which appeared to him parti- 

 cularly conclusive, namely, the sterilisation of wine-must by sulphur- 

 ing. When wine-casks, before filling, are thoroughly sulphured 

 i.e. the internal air contained in them is heavily charged with 

 sulphur dioxide by burning sulphur in the casks the grape 

 juice thereafter introduced remains quiet and passive, without 

 fermenting. This circumstance is now unanimously ascribed to 

 the vitality of the yeast cells in the must being destroyed by the 

 sulphurous acid. Gay-Lussac, on the other hand, viewing the 

 matter differently from his standpoint, held the opinion that as 

 the sulphurous acid had a strong affinity for the oxygen, the two 

 combined, and as no oxygen was available for starting the fermen- 

 tation, the must necessarily remained inert. 



The experiments made by Schwann in 1838, and described in 

 13, refuted the opinion of Gay-Lussac, by demonstrating that 

 the role of exciting fermentation is set up by certain microscopic 

 living creatures which perform their functions in the absence of 

 oxygen. Subsequent research proved that the presence of this' 

 gas is altogether superfluous, so far as the progress of alcoholic 

 fermentation is concerned, although it is not without influence 

 thereon. PASTEUR (II.) in 1861 established it as a fact that this 

 progress is more satisfactorily effected when the fermenting liquid 

 is subjected to brisk aeration. 



12, Cagniard-Latour's Vitalistie Theory of 

 Fermentation. 



The French apothecary ASTIER (I. and II.) has generally been 

 credited with being the next individual, after Leeuwenhoeck, who 

 gave his attention to the nature of yeast. An examination of his 

 published works shows, however, that his investigations into fer- 

 mentation were conducted without the aid of the microscope, so 

 that he did not bring to light any actual facts concerning the 

 nature of yeast, but as was pointed out, though in vain, by 

 QUEVENNE (I.) as far back as 1838 based his assumptions on 

 hypotheses devoid of foundation. 



In the same way another Frenchman, viz., Desmazieres, the 

 reputed pioneer of the founders of the vitalistic theory of fermen- 

 tation, cannot permanently retain this title. Like Astier, he is 

 said to have recognised the part played by yeast in fermentation, 

 but, as a reference to his treatise, published in 1826 (in pages 42 

 to 67 of vol. x. of the Ann. des Sc. Nat.), will show, this assertion 

 is incorrect. In these observations Desmazieres viewed the matter 

 simply as a naturalist. His investigations of the fungoid growths 

 covering the surface of moist substrata were conducted from this 



