FERMENTATION. 257 



clear, filtered * must ' of the grape be so boiled as to 

 destroy such germs as it may have contracted from the 

 air or otherwise. In contact with germless air the 

 uncontaminated must never ferments. All the mate- 

 rials for spontaneous generation are there, but so long 

 as there is no seed sown, there is no life developed, and 

 no sign of that fermentation which is the concomitant 

 of life. Nor need you resort to a boiled liquid. The 

 grape is sealed by its own skin against contamination 

 from without. By an ingenious device Pasteur has ex- 

 tracted from the interior of the grape its pure juice, 

 and proved that in contact with pure air it never ac- 

 quires the power to ferment itself, nor to produce fer- 

 mentation in other liquids. 1 It is not, therefore, in the 

 interior of the grape that the origin of the life observed 

 in the vat is to be sought. 



What then is its true origin? This is Pasteur's 

 answer, which his well-proved accuracy renders worthy 

 of all confidence. At the time of the vintage micro- 

 scopic particles are observed adherent, both to the outer 

 surface of the grape and of the twigs which support the 

 grape. Brush these particles into a capsule of pure 

 water. It is rendered turbid by the dust. Examined 

 by a microscope, some of these minute particles are 

 seen to present the appearance of organised cells. 

 Instead of receiving them in water, let them be 

 brushed into the pure inert juice of the grape. Forty- 

 eight hours after this is done, our familiar Torula is 

 observed budding and sprouting, the growth of the 

 plant being accompanied by all the other signs of active 

 fermentation. What is the inference to be drawn from 



1 The liquids of the healthy animal body are also sealed from 

 external contamination. Pure blood, for example, drawn with due 

 precautions from the veins, will never ferment or putrefy in contact 

 with uure air. 



