418 YEAST 



of wine." Now what a very curious phrase that is, if you 

 come to think of it. The old alchemists talked of the finest 

 essence of anything as if it had the same sort of relation to 

 the thing itself as a man's spirit is supposed to have to his 

 body ; and so they spoke of this fine essence of the fermented 

 liquid as being the spirit of the liquid. Thus came about 

 that extraordinary ambiguity of language, in virtue of which 

 you apply precisely the same substantive name to the soul 

 of man and to a glass of gin I And then there is still yet one 

 other most curious piece of nomenclature connected with 

 this matter, and that is the word " alcohol " itself, which 

 is now so familiar to everybody. Alcohol originally meant 

 a very fine powder. The women of the Arabs and other 

 Eastern people are in the habit of tinging their eyelashes 

 with a very fine black powder which is made of antimony, 

 and they call that " kohol ; " and the " al " is simply the 

 article put in front of it, so as to say " the kohol." And 

 up to the 17th century in this country the word alcohol was 

 employed to signify any very fine powder ; you find in 

 Robert Boyle's works that he uses " alcohol " for a very fine 

 subtle powder. But then this name of anything very fine and 

 very subtle came to be specially connected with the fine 

 and subtle spirit obtained from the fermentation of sugar ; 

 and I believe that the first person who fairly fixed it as the 

 proper name of what we now commonly call spirits of wine, 

 was the great French chemist Lavoisier, so comparatively 

 recent is the use of the word alcohol in this specialised 

 sense. 



So much by way of general introduction to the subject 

 on which I have to speak to-night. What I have hitherto 

 stated is simply what we may call common knowledge, 

 which everybody may acquaint himself with. And you 

 know that what we call scientific knowledge is not any kind of 

 conjuration, as people sometimes suppose, but it is simply 

 the application of the same principles of common sense that 

 we apply to common knowledge, carried out, if I may so 

 speak, to knowledge which is uncommon. And all that we 

 know now of this substance, yeast, and all the very strange 

 issues to which that knowledge has led us, have simply come 

 out of the inveterate habit, and a very fortunate habit for the 

 human race it is, which scientific men have of not being 

 content until they have routed out all the different chains 

 and connections of apparently simple phenomenn, until 

 they have taken them to pieces and understood the condi- 



