188 
PROFESSOR TYNDALL ON THE DEPORTMENT AND VITAL 
It behoves those engaged in the industry of preserved meat and vegetables to keep 
clear of the old-hay contamination. Probably they from time to time have encountered 
difficulties and disappointments which they could not explain, but which may be solved 
by reference to the results here set forth. But above all the practical question arises : — 
May not the surgeon have to fight sometimes against enemies like those here described \ 
The particular germs with which I have been so long contending cause, as we have seen, 
both fish and flesh to putrify. How would they behave in the wards of an hospital 1 
Can they cause wounds to putrify ? and if so, would they succumb to the disinfectants 
usually applied ? These are questions the weighty import of which will be best under- 
stood by the enlightened follower of the antiseptic system, and which he will know how 
to answer for himself. 
§ 20. Bemarlcs on Acid , Neutral , and Alkaline Infusions. 
In the foregoing section reference was made to the comparative deportment of acid 
and neutral infusions. There can be no doubt of the fact that, for the nutrition and 
multiplication of Bacteria , acid infusions are less suitable than neutral or slightly alka- 
line ones. In acid infusions exposure to the common air sometimes copiously develops 
Penicillium, while it fails to develop Bacteria. It is also true that exposure for 
a certain time to a certain temperature may in many cases prevent the appearance of 
life in an acid infusion, and fail to prevent it in a neutral or slightly alkaline one. 
In the present inquiry this has been frequently found to be the case. I have many 
closed chambers, for example, to which the process of “ discontinuous heating,” to be 
subsequently described, has been applied ; and with them it has proved a common expe- 
rience that an amount of heating which has rendered acid infusions of hay permanently 
barren has failed to sterilize the corresponding neutral infusions. Moreover, in the cases 
just recorded, where single bulbs escaped sterilization though exposed for five, six, and 
eight hours to the boiling temperature, it was always a neutral bulb that kindled into life. 
To these instances another may be added here. On the 22nd of March an infusion of 
the wiry Guildford hay already referred to was divided into two parts, one of which was 
neutralized and the other left acid. Five pipette-bulbs were filled with the one infusion 
and five with the other. After hermetic sealing they were all completely submerged in 
water and boiled for six hours. Every one of the acid bulbs was sterilized by this process, 
while in two days three of the five neutral ones became turbid and covered with scum. 
The best thought that I have been able to bestow upon this subject does not induce 
me to lean towards the explanation suggested by M. Pasteur, namely, that the germs 
escape the destructive action of the heat because they are not wetted by the alkaline or 
neutral liquid. From the comparative action of alkalized and acidulated water upon 
hay, I should be inclined to infer that the wetting of its germs by the former would be 
more prompt than by the latter. The question, I think, is not one of wetting, but of 
relative nutritive power. Two B act eria-ger ms of equal vital vigour dropping from the 
atmosphere, the one into a neutral or slightly alkaline, the other into an acid infusion, 
