EARLY DISCOVERIES. 19 



In 1680 the Dutch professor Leuwenhoeck began the 

 examination of yeast under the microscope, and found it to 

 consist of minute ovoid or globular particles. But the imper- 

 fection of the instruments of his time prevented the discovery, 

 which seemed so near, of the nature of these particles. Ex- 

 periments of various kinds were instituted by many persons, a 

 few of which may be mentioned : A bladder was filled with a 

 solution of sugar and suspended in another solution of sugar, 

 to which yeast had been added. While fermentation went 

 regularly on in the fluid in the containing vessel, the fluid in 

 the bladder did not partake in the fermentation. A vessel was 

 divided into two compartments by a partition of filtering 

 paper, a solution of sugar placed in each and yeast added to 

 one. Fermentation went on promptly in the compartment to 

 which the yeast was added, but the other remained free from 

 fermentation. Many other experiments are also recorded, all 

 tending to show that fermentation is something different from 

 ordinary chemical action. But the men of the time seemed 

 unable to understand the significance of their experiments, 

 which, to us, prove conclusively that the substance causing 

 fermentation is participate and not soluble, otherwise it would 

 pass through the filters and produce its results. 



In 1787 Fabroni affirmed that " the matter which decom- 

 poses sugar is a vegeto-animal substance; it resides in par- 

 ticular utricles in grapes, as well as in corn. When grapes 

 are crushed this glutinous matter is mixed with the sugar. 

 Directly the two substances come in contact, effervescence and 

 fermentation commence." 



Astier, in 1813, asserted that "the matter of ferment, 

 recognized by Fabroni as an animal substance, was alive and 

 derived its nourishment from the sugar, whence resulted the 

 rupture of the equilibrium between the elements of this body. 

 By this theory," said he, "it is easily explained that all the 



