gO THE EVOLUTION OF LIFE 
respects complied with Schwann’s conditions ; while 
Dr Child! also showed that organisms were to be 
met with when either oxygen or nitrogen was sub- 
stituted for atmospheric air in similar experiments. 
It was stated by Spallanzani that while organ- 
isms were procurable from hermetically sealed flasks 
in which the air was somewhat rarefied, they were 
not to be met with when the rarefaction was ex- 
treme, or where a vacuum existed. Pouchet also 
rejected, as preposterous, the notion that organisms 
could be expected to occur under such conditions ;? 
and both he, as well as Pasteur, whenever desiring 
to make comparative trials with the air of different 
localities, boiled the fluids and sealed the necks of 
the flasks during ebullition—never supposing that 
any fermentative changes could occur in the fluids 
contained in these airless flasks.’ 
In the spring of 1870, however, after a few 
tentative trials, I definitely adopted this mode of 
experimentation, and soon had reason to:think that 
some infusions were rather more prone to undergo 
change in these retorts, from which almost all the 
air had been expelled, than when they were con- 
tained in flasks full of air, prepared after the manner 
of Needham and Spallanzani. 
It occurred to me, at that time, that putrefactive or 
fermentative changes might not always be initiated 

1“ Kissays on Physiological Subjects,” 2nd ed., 1869, p. 114. 
2 “ Nouvelles Experiences,” 1884, p. 12, note, and p. 156. 
3 Such flasks were carried away by them to the Alps or Pyrenees, 
in order that the necks of the flasks might be broken in the localities 
chosen, the influence of whose air they wished to test. After being 
resealed the flasks were kept for future observation of their contents. 
