YEAST 419 



Uons upon which they depend. I will try to point out to you 

 now what has happened in consequence of endeavouring 

 to apply this process of " analysis," as we call it, this teazing 

 out of an apparently simple fact into all the little facts of 

 which it is made up, to the ascertained facts relating to the 

 barm or the yeast ; secondly, what has come of the attempt 

 to ascertain distinctly what is the nature of the products 

 which are produced by fermentation ; then what has come 

 of the attempt to understand the relation between the yeast 

 and the products ; and lastly, what very curious side issues 

 if I may so call them have branched out in the course of 

 this inquiry, which has now occupied somewhere about 

 two centuries. 



The first thing was to make out precisely and clearly what 

 was the nature of this substance, this apparently mere scum 

 and mud that we call yeast. And that was first commenced 

 seriously by a wonderful old Dutchman of the name of 

 Leeuwenhoek, who lived some two hundred years ago, and 

 who was the first person to invent thoroughly trustworthy 

 microscopes of high powers. Now, Leeuwenhoek went 

 to work upon this yeast mud, and by applying to it high 

 powers of the microscope, he discovered that it was no mere 

 mud such as you might at first suppose, but that it was a 

 substance made up of an enormous multitude of minute 

 grains, each of which had just as definite a form as if it were 

 a grain of corn, although it was vastly smaller, the largest 

 of these not being more than the two-thousandth of an inch 

 in diameter ; while, as you know, a grain of corn is a large 

 thing, and the very smallest of these particles were not more 

 than the seven-thousandth of an inch in diameter. Leeu- 

 wenhoek saw that this muddy stuff was in reality a liquid, in 

 which there were floating this immense number of definitely 

 shaped particles, all aggregated in heaps and lumps and some 

 of them separate. That discovery remained, so to speak, 

 dormant for fully a century, and then the question was taken 

 up by a French discoverer, who, paying great attention and 

 having the advantage of better instruments than Leeuwen- 

 hoek had, watched these things and made the astounding 

 discovery that they were bodies which were constantly being 

 reproduced and growing ; that when one of these rounded 

 bodies was once formed and had grown to its full size, it 

 immediately began to give off a little bud from one side, 

 and then that bud grew out until it had attained the full 

 size of the first, and that, in this way, the yeast particle was 



