Il4 THE DEATH-POINT OF BACTERIA 
view, it would be only reasonable to expect that the 
molecular movements of living ferments with a 
lowered vitality might not be more marked or 
energetic than those which many not-living organic 
substances are apt to undergo; and this being the 
case, we might expect that there would often be a 
great practical difficulty in ascertaining whether a 
ferment belonging to the arbitrary and artificial 
(though, in a sense, justifiable and natural) category 
of “living” things had or had not been in operation. 
It has, moreover, been most unmistakably proved 
that the limits of vital resistance to heat which 
Bacteria, Vibriones, and their supposed germs are 
capable of displaying are essentially the same in the 
three type fluids which I have employed—that is, ina 
weak saline fluid, in a neutral organic infusion, and in 
an acid organic infusion. No evidence exists really 
tending to show that these organisms or their germs 
are capable of withstanding the effects of heat better 
in one of such fluids than in another. We may 
therefore safely affirm that M. Pasteur never had any 
valid evidence in support of his conclusion that the 
germs of Bacteria and Vibriones can resist heat better 
in neutral or slightly alkaline solutions than in slightly 
acid mixtures. The experimental results which led 
him to arrive at such a conclusion were not logically 
capable of receiving any such interpretation, whilst 
