viii PREFACE. 
to the temperature of 212° F., there is no longer 
room for doubt. The occurrence of ‘Spontaneous 
Generation’ must in this case be admitted as an 
established fact, or ‘Law of Nature,’ 
But the evidence now in our possession concerning 
the death-point of heated Living Matter all tends 
to show that it is killed at a temperature below 
that of boiling water, as will be seen by the facts 
recorded in the last essay of this volume. The 
two previous papers, moreover, contain the records 
of experiments proving that Bacteria and their 
germs are killed at 140° F.—these being the very 
organisms that most frequently make their appear- 
ance in the fluids within closed experimental vessels 
which have been previously heated to 212° F. 
In the present aspect of the question, therefore, 
these three papers contain all the evidence needed 
for the establishment of the occurrence of ‘Spon- 
taneous Generation.’ In the two parts of the first 
essay, however, I have endeavoured to show that 
the acknowledgment of this natural origin of Liv- 
ing Matter carries with it no contradictions, and is 
indeed in accordance with the present state of 
scientific knowledge. I have further striven to give, 
