PERSISTENCE OF PUTREFACTIVE AND INFECTIVE ORGANISMS. 
175 
confusion of mind still prevalent in relation to this subject that renders such a 
question necessary. Let me add that it suffices simply to wave a bunch of hay in the 
air of the shed to make it as infective as the laboratory air. Even the unprotected 
head of my assistant when his body was carefully covered sufficed in some cases to carry 
the infection. 
If any thing were needed to illustrate the extraordinary care necessary on the part of 
physicians and surgeons, both as regards the clothes they wear and the instruments they 
use, such illustrations are copiously furnished by the facts brought to light in this 
inquiry. 
§ 16. Preliminary Experiments on the Eesistance-limit of Germs to the temperature 
of Boiling Water. 
While continuing the conflict and experiencing the defeats recorded in the foregoing 
pages, a remark of Professor Lister’s sometimes occurred to me. To apply the anti- 
septic treatment with success, the surgeon must, he holds, be interpenetrated with the 
conviction that the germ- theory of putrefaction is true. He must not permit occasional 
failures to produce scepticism, but, on the contrary, must probe his failures, in the 
belief that his manipulation, and not the germ-theory, is at fault. This may look like 
operating under a prejudice ; but Professor Lister’s maxim is nevertheless consistent 
with sound philosophy and good sense ; and if I permitted a bias to influence me in 
this inquiry, it was one fairly founded on antecedent knowledge, which led me to 
conclude that the long line of failures above referred to would eventually be traced to 
my ignorance of the conditions whereby perfect freedom from contamination was to be 
secured. 
I laboured to discover these conditions, and to learn something more regarding the 
nature of the contamination — its origin, persistence, and manner of action. When 
these researches began, five minutes’ boiling, as I have frequently stated, sufficed to 
sterilize the most diversified infusions. Here we have frequently extended the time 
of boiling to ten and fifteen minutes, and, in some cases glanced at above, to immensely 
longer periods, without producing this result. I desired more exact knowledge as to 
the limit of endurance, and with this view, on the 22nd of December, had six bulbs 
charged with an infusion of cucumber, sp. gr. 1004. They were then plugged with 
cotton- wool, hermetically sealed, and subjected to the boiling temperature for 10 minutes. 
Six other bulbs, charged with the same infusion and treated in the same way, were boiled 
for 30 minutes. Finally eight bulbs, similarly charged, were boiled for 120 minutes. 
On the 23rd of December three of the first group of bulbs, three of the second, and 
five of the third, having their sealed ends filed off, were exposed to a tolerably constant 
temperature of about 90°Fahr. Not one of these twenty bulbs preserved itself free 
from life. On the 25th of December every one of them had given way to cloudiness 
and turbidity. 
There was, however, a marked difference between the sealed and the unsealed bulbs. 
2 c 2 
