rv 



YEAST 121 



misceii ; hac, vero aqua, quam cere vis iam vocare licet, refriges- 

 cente, multos ex minimis particulis in cerevisiacoadunaii, et hoc 

 pacto efficere particulam sive globuliim, qiise sexta pars est 

 globuli faecis, et iterum sex ex hisce globulis conjungi." ^ 



Thus Leeuwenhoek discovered that yeast con- 

 sists of globules floating in a fluid ; but he thought 

 that they were merely the starchy particles of the 

 grain from which the wort was made, rearranged. 

 He discovered the fact that yeast had a definite 

 structure, but not the meaning of the fact. A 

 century and a half elapsed, and the investigation 

 of yeast was recommenced almost simultaneousl}? 

 by Cagniard de la Tour in France, and by Schwann 

 and Ktitzing in Germany. The French observer 

 was the first to publish his results ; and the sub- 

 ject received at his hands and at those of his 

 colleague, the botanist Turpin, full and satisfactory 

 investigation. 



The main conclusions at which they arrived are 

 these. The globular, or oval, corpuscles which 

 float so thickly in the yeast as to make it muddy, 

 though the largest are not more than one two- 

 thousandth of an inch in diameter, and the 

 smallest may measure less than one seven- 

 thousandth of an inch, are living organisms. They 

 multiply with great rapidity by giving off minute 

 buds, which soon attain the size of their parent, 

 and then either become detached or remain 

 united, forming the compound globules of which 

 ^ Leeuwenhoek, Arcana Naturce Detecta. Ed. Nov., 1721. 



