tfERMENTAflON. 93' 



t can only bring about the detachment of the molecules or 

 )ricks of a substance when the motion of the molecules of 

 hat substance is started or extended by the action of a 

 lertain degree of heat ; thus fermentation will not take place 

 mless the material to be fermented is kept at a temperature 

 )f from io° to 40°. This increased temperature acts, pro- 

 )ably, in two ways : first, by increasing the motion of the 

 nolecules as above stated, and secondly, by enabling the 

 )rotoplasm to act more energetically, by increasing the rate 

 md extent of molecular motion within the organism itself. 

 The determining motion, according to Bunge, " might pro- 

 ved from the vital functions of the cell. But it is likewise 

 :onceivable that certain substances occur in the cell, and 

 hat these substances act in a similar manner to the catalytic 

 )odies in the examples adduced above." Heat and moisture 

 ire both necessary factors in all processes of fermentation, 

 mt neither of these alone can give rise to it. 



Pasteur, who was really the first to understand this sub- 

 ect so far as to be able to throw light upon it for others, 

 ooked upon " fermentation, properly so called, as a chemical 

 )henomenon, co-relative with physiological actions of a pecu- 

 iar nature," the elements in which the peculiar physiological 

 ctions were manifested being spoken of as ferments which 

 vere not dead albuminoid matter, as held by Liebig and his 

 chool, but actually living organisms " of a peculiar nature 

 a this sense, that they have the property of exercising all 

 he functions of their life, not excepting ' vegetative multi- 

 ilication,' without necessarily employing the oxygen of the 

 tmospheric air ; " and he thus generalizes his results : 

 ' Guided by all these facts, I have been gradually led to 

 Dok upon fermentation as a necessary consequence or mani- 

 sstation of life when that life takes place without the direct 

 ombustion due to free oxygen." This opened up exceed- 

 Digly wide and important questions : Was it possible that 

 11 living plant-cells might have the power of inducing ' 

 jrmentation in a more or less marked degree? and did 

 easts differ from other living cells only in the fact that 

 hey had more marked powers of acting on certain carbo- 

 lydrates, and of exciting alcoholic fermentation ? Experi- 

 lents on fruit, on barley, on leaves, all went to prove that the 

 lementary cells of plants possessed within themselves this 

 lower of inducing fermentation of sugar that was already 



