74 



:*jth March, i! 



William H. Patterson, Esq., M.R.I.A., in the Chair. 



Professor Letts read a Paper on 

 FERMENTATION AND KINDRED PHENOMENA. 



The subject which I have chosen for this lecture is one I may 

 say of extraordinary interest and importance, not only in a purely 

 scientific sense (though it has opened up several new fields of 

 research), but equally if not more so from a practical point of 

 view, as it deals with a wide range of subjects of much practical 

 importance, and involves questions of the greatest moment to the 

 whole human race. Among the latter there is a great deal that 

 bears directly upon the causes, nature, and prevention of disease, 

 and I feel that I may be charged with presumption for discussing 

 this branch of the subject, which belongs more particularly to 

 medicine and surgery ; but my excuse must be that it is also 

 very intimately connected with chemistry — in fact, its medical 

 and chemical aspects are linked by the closest bonds, and I do 

 not see how they can be discussed apart. 



Let me first direct your attention to ordinary fermentation — 

 the change which occurs in the manufacture of all spirituous 

 beverages, such as wine, beer, whisky, &c. 



Fermentation has been known from the earliest times. The 

 art of wine making was attributed by the Egyptians to Osiris, 

 by the Greeks to Bacchus, whilst as every one knows the 

 Israelitish tradition assigns its discovery to Noah. 



I suppose every one is aware how wine is made : that the 

 grapes are crushed and the juice exposed to the air, when after 

 some time a frothing occurs, and spirit gradually makes its 



