PEESISTENCE OE PTTTKEF A CTI VE AND INFECTIVE OEGANISMS. 
185 
{ Guildford neutral a little more turbid than Guildford acid : 
difference small. 
Old Heathfield neutral more turbid than the acid in- 
fusion ; the former with scum, the latter none, 
f Guildford neutral distinctly more 4 turbid than Guildford 
J acid; the former with scum, the latter free from scum. 
4th group. 60 minutes. jj ea thfield neutral somewhat more turbid and scummy 
than the acid liquid : difference not great. 
Here I take it to be absolutely certain that the germs which resisted sterilization were 
contained in the liquid. The maximum period of boiling was 60 minutes. 
On the 22nd of February four groups of bulbs were charged as above described with 
the same two infusions, and the periods of boiling prolonged as follows : — 
1st group 90 minutes. 
2nd „ 120 „ 
3rd „ 180 „ 
4th „ 240 „ 
As in the last case, neutral and acid infusions of each kind of hay were operated on. 
This was the result; — On the evening of the 23rd, that is to say, 24 hours after their 
preparation, every one of these bulbs disclosed to the practised eye that organisms existed 
within it. At 2 p.M. on the 24th they all swarmed with life. The old Heathfield bulbs, 
both acid and neutral, were turbid and covered with scum, the very weakly-acid infusions 
being indistinguishable in appearance from the neutral ones. In the case of the Guildford 
infusion, however, the scum on the neutral infusions was richer and heavier than that 
on the acid ones. 
Four hours mark the limit to which the boiling was carried in these experiments. 
On the 27th of February the periods of boiling were still further prolonged. Four 
groups of bulbs charged with infusions of the same two kinds of hay, both acid and 
neutral, were on that day boiled for the following times : — 
1st group 300 minutes. 
2nd „ 360 „ 
3rd „ 420 „ 
4th „ 480 „ 
I had previously boiled infusions of old Heathfield, old London, and old Colchester 
hay for 5 hours, and found them afterwards permanently barren. In the present instance, 
also, all the bulbs boiled for 5 hours, 6 hours, and 7 hours were completely sterilized. 
They remained ever afterwards perfectly brilliant. This, with one exception, was also 
the deportment of the group of bulbs boiled for 8 hours. The exception was a neu- 
tralized bulb of Guildford infusion, which became turbid and covered with scum. 
Considering the severity with which the bulb had been treated prior to charging, and 
considering the mode of charging it, I do not think that the life developed could have 
