118 THE EVOLUTION OF LIFE 
number of organisms found in equal bulks under 
similar conditions can almost always be very 
notably increased in either one of them by the 
mere addition of a few drops of liquor potasse, 
so as to render that portion neutral or slightly 
alkaline. 
Such facts may, of course, be interpreted as an 
indication that slight alkalinity or neutrality of the 
fluids is more favourable than their acidity for the 
occurrence of fermentative changes. Then, again, 
it would seem quite possible that the difference 
between acid and neutral solutions, as regards the 
number of organisms to be found in them when they 
have been simply exposed for a few days to ordinary 
atmospheric temperatures, might be exaggerated 
after such fluids had been subjected to the tempera- 
ture at which water boils. It seems quite pos- 
sible, that is, that high temperatures such as that of 
100 C. might be more destructive to organic matter 
when contained in acid infusions than when it exists 
in neutral or slightly alkaline infusions. And other 
comparative experiments which I have elsewhere 
recorded! show that this is so, and that the 
differences in the amount of fermentative changes 
to be seen at ordinary atmospheric temperatures are 
very distinctly exaggerated when other portions 
of the same neutral and acid fluids have been 
previously boiled. 
Now let us look at Pasteur’s experiences with 
acid and with neutral solutions, and at the degree 
1 “The Beginnings of Life,” vol. i. pp. 394-97. 

