II. 



Tlll-;ui;||-> OF IT.HMKNTATloN. 



10. Stahl's Theory of Fermentation. 



VEK was the first to leave the juice of sweet fruit to itself in storage for 



a few days had tin- plea-un- of olerving a phenomenon hitherto unknown 



tin- incipient di -composition of the mass which we nowadays term alcoholic 



fermentation. This oln vation wa- made at so early a date that we have no 



.nd myth and tradition. The Greeks feted the deity Bacchus 



ine, and the Egyptians ascribed to Osiris the first iiitroduc- 



of brewing. 



Acquaintance with the nature of this phenomenon was, however, of an 



Mipei -licial character for a very long time. Even in the later Middle 



Ages the word fermentatio (fermentation) was employed as synonymous with 



diijeetlo (digestion), the latter word being also currently used to denote any form 



Miical reaction ; and the word "ferment" was applied to any body capable 



of producing such reaction. 



At an early date it would necessarily be noticed that the " must " when in a 



state of fermentation became covered with a froth, and that at the end of this 



operation a copious deposit, viz., yeast, was left at the bottom of the vessels. 



Fermentation was therefore looked upon as a process of purification, by which 



itially turbid and discoloured liquid was so improved and freed from dirt, 



that the j.'irilied alcohol exhibited its true properties. For this reason the 



deposit was described as the fceces vini or fceces cerevisice, i.e. the excrement of 



me or beer. This view was held by, e.</. llasilius Valentin US, a German 



monk and alchemi>t. who lived at Erfurt early in the fifteenth century. 



It wa> al>o noticed that this sediment was a powerful ferment, i.e. it was 

 capable of rapidly exciting a brisk fermentation in still nnferinented liquids, 

 such a- \\ine in'i.-t <>i beer-wort. This idea was adopted in other branches of 

 chemistry, 80 that any reaction was considered as elucidated when the body 

 acting as '* ferment" therein could be identified. Moreover, the " philosopher's 

 stone," the goal of the labours and aspirations of the alchemist.-, was nothing 

 but the much Bought for. but never discovered, universal ferment" for every 

 possible chemical process! 



Among ' pies of the alchemic school, one other, vi/., STAIN, (I.), 



deserves mention, because hi- riewa on tin- nature of fermentation were adopted 

 by Lii-big a hundred and forty years later. Staid extended the delinition of 

 fermentation to all ! -mpo>ition, his theory heini: expiv e.l /-t^ttim 



as folio u : i on ( ; ,nd also fermentation) is internal movement. A 



body undergoing such internal movement may ea>ily induce the value in any 

 r body, which, though still quiescent, is siiMeptible of Mich movement." 



11. Gay-Lussac's Opinion. 



_rue until the commencement of the nine- 

 teenth century, when (lay-Lussi , enunciated a new theory to a new 



