
EX AMINATION OF PASTEUR’S DOCTRINES 117 
tative changes that would take place in otherwise 
similar slightly alkaline or acid organic infusions, 
even at ordinary temperatures and with more or less 
free exposure to the air. Thus, to quote one of the 
experiments made by myself many years ago,! 
‘“Having prepared a pretty strong infusion of 
mutton, about an ounce and a half was put, after 
filtration, into each of two similar flasks. One 
portion of the infusion was allowed to remain 
neutral, while to the other three drops of strong 
acetic acid were added, so as to make the whole 
yield a faintly acid reaction to test paper. The two 
flasks were then exposed side by side to a tempera- 
ture of 75° to 80° F. during the day. In twenty- 
four hours the neutral solution was clouded and 
more or less opaque, while the portion which was 
acid appeared perfectly unchanged. It was as clear 
as ever; and so it continued even to the end of 
forty-eight hours, although by this time the neutral 
solution was quite opaque and muddy-looking, with 
a pellicle on its surface, and also some flocculent 
deposit at the bottom of the flask.” This fluid, 
on examination, was found to be swarming with 
Bacteria of different kinds. 
Other experiments of a like kind, with different 
neutral or slightly alkaline infusions, have also shown 
that the addition of a few drops of acid causes the 
fluid, after a given time, to contain a notably 
smaller number of organisms than an equal bulk of 
the unaltered solution ; and, conversely, having an 
acid infusion whose productiveness is known, the 
1 “ ThesBeginnings of Life,” vol. i. p. 387. 
