8 THE DEATH-POINT OF 
not become more numerous, however long the slide is 
kept. Facts of the same kind are observable if a 
turnip-infusion containing living Bacterza is experi- 
mented with; and the phenomena are in no way differ- 
ent if a solution of ammonic tartrate and sodic 
phosphate (containing Bacteria) be employed instead 
of one of these vegetable infusions. The multiplica- 
tion of the Bacteria beneath the covering-glass, when 
it occurs, is soon rendered obvious, even to the naked 
eye, by the increasing cloudiness of the film.” 
The facts just cited concerning the behaviour of thin 
films of turbid infusions which had been heated to 
different temperatures gave me the clue as to the 
proper direction of future work. It would seem that 
when mounted in the manner described, such thin 
films of infusion continue capable of supporting and 
favouring the multiplication of any already existing 
Bacteria and Vibriones, although under such con- 
ditions no new birth of living particles appears to take 
place even in these fluids. The question then arose as 
to whether, by subjecting larger quantities of the same 
infusions to any particular sets of conditions, we could 
ensure that they also should continue to manifest the 
same properties ; because if so, it would be almost as 
easy to determine the death-point of Bacteria and 
Vibriones when exposed to heat in these infusions, as 
it had been to determine it for the saline solutions 
already mentioned. 
