60 THE EVOLUTION OF LIFE 
putrefy after being heated to the boiling-point, and 
he inferred (so far legitimately enough) that no germ 
could (in such a fluid) sustain the temperature of 
100 C. He also found that one or two neutral or 
faintly alkaline fluids would putrefy after boiling, 
though they failed to do so if heated to 110° or even 
105° C. He thereupon straightway assumed that 
putrefaction could not come without germs, and 
therefore declared that germs heated in these non- 
acid fluids could survive a temperature of 100° C., 
though they succumbed to a slightly greater heat. 
Of course the inference was idle while the germ 
theory was in question; and some independent 
method of fixing the death-point remained to be 
discovered, if even it was to be fixed at all.” 
In 1871 I made the first attempt to ascertain the 
exact death-point of Bacteria, when heated in the 
nourishing neutral solution of ammonium tartrate and 
sodium phosphate. The details of the mode of 
experimentation have been given elsewhere.! It is 
only necessary to say here that specimens of this 
fluid, inoculated with a drop of a similar fluid 
swarming with Bacteria, were heated for about ten 
minutes to the following temperatures, 122° F., 131°, 
140°, 149, 153°, and.267., and the fluids in he: 
metically sealed vessels were subsequently main- 
tained at a temperature of about 90 F. 
The results were as follows :—The flasks whose 
contents had been heated to 122° and 131° re- 
spectively began to exhibit an opalescent tinge in 
1 “ Modes of Origin of Lowest Organisms,” 1871, pp. 51-56. 

