PERSISTENCE OE PUTREE ACTIVE AND INFECTIVE ORGANISMS. 
159 
between its constituent molecules. It would be difficult to cause such a germ to imbibe 
the moisture necessary to produce the swelling and softening which precede its destruction 
in a liquid of high temperature. 
In my last paper I made some remarks upon this subject * ; and in relation to our 
present experiments, the influence of drying and hardening was brought home to me 
by the fact that in all the foregoing cases the infusions which five minutes’ boiling proved 
sufficient to sterilize were, without exception, derived from fresh hay mown in 1876, 
while the infusions which five minutes' boiling failed to sterilize were derived, without 
exception, from old hay mown either in 1 875 or some previous year. 
In the earlier experiments of the present inquiry this distinction between old and 
new hay came most clearly and definitely out. The result was subsequently blurred 
by circumstances which it required time and labour to unravel, and which will require 
patience on the reader’s part if he would follow them through all their monotonous 
obstructiveness. They will, however, throw far more light upon the real character of 
these inquiries, and do more to reconcile the discords to which they have given birth, 
than if every experiment had been a success unshaded by doubt. 
§ 7. Hay-infusions. Further experiments with Closed Chambers. 
With a view to probing to the uttermost this question of drying and hardening, on 
the 6th of October an extensive series of experiments with closed chambers was begun. 
Three different kinds of hay were employed: — 1st, Old hay, from Heathfield, Sussex ‘j’; 
2nd, new hay from Heathfield (both, it may be stated,- from a somewhat ungenerous 
soil); 3rd, new hay purchased in London, and artificially dried for some days upon a 
sand-bath. For these experiments eleven closed chambers were prepared, as I wished 
every result to be based as far as possible upon the testimony of two chambers. 
On the 6th of last October they were carefully charged with the infusions, the period 
of boiling afterwards being five minutes. 
Two chambers were devoted to the acid and two to the alkalized infusion of old hay. 
Two chambers were also devoted to the acid and two to the alkalized infusion of dried 
hay. Two chambers were finally devoted to the alkalized and one to the natural acid 
infusion of new Heathfield hay. 
Examined from day to day, differences were soon observed, not only between the 
different infusions, but also between different chambers containing the same infusion. 
Thus every tube of both the chambers containing the neutralized infusion of old hay 
became turbid, but the three tubes of the one chamber were loaded in four days with a 
fatty scum, while the tubes of the other chamber remained for ten days perfectly free 
from scum. The two chambers containing the acid infusion of old hay exhibited 
similar differences. Every tube in both of them became turbid ; but in one of them the 
* Phil. Trans, vol. clxvi. p. 60. 
t After the possible influence of hard drying and hardening had suggested itself, I purposely introduced old 
hay from various localities into the laboratory. 
2 A 2 
