58 THE EVOLUTION OF LIFE 
the two fluids is speedily shown. The latter, as we 
have seen, remains clear, while the turnip infusion 
almost invariably becomes turbid in the course of 
two or three days, owing to the presence and mul- 
tiplication of myriads of Bacteria. 
Now, all the experimental work to be detailed in 
this volume has been undertaken in order to throw 
light upon the cause of this different behaviour of 
the turnip infusion, and other fluids which behave in 
a similar manner. It is clear that both are xourzsh- 
eng fluids, since we find that Bacteria are capable of 
growing and multiplying in each of them. What 
we want to know is, whether the turnip infusion, and 
other fluids that behave in a similar manner, are also. 
generating fluids—that 1s, fluids capable, after they 
have been boiled, of giving birth to specks of living 
matter which speedily take the form of Bacteria or 
Torule. So far we have found no evidence showing 
that any living thing could survive even momentary 
exposure to the influence of boiling water, so that 
the problem is a most legitimate one. 
The latter possibility, however, is one which has 
been utterly repudiated both by Pasteur and by 
Tyndall, as we have seen (p. 33, zote). In his 
celebrated memoir published in 1862, one of 
Pasteur’s principal objects was to determine whether 
fermentation could or could not take place without 
the intervention of living organisms which he, at 
that time, held (in opposition to many other chemists) 
to be the only true ferments. In Chapters iv. and v. 
of his memoir he records experiments in which he 
inoculated fluids with dust filtered from the atmos- 

