DE. W. EOBEETS ON BIOGENESIS. 
473 
cotton-wool, and had been kept in a warm place for several months. The liquids in 
them were perfectly transparent, and showed no signs of germination. The contents of 
these bulbs seemed especially favourable for testing the possibility of germs surviving a 
boiling heat. These bulbs, sixteen in number, were divided into three sets. 
The first set (six bulbs) were treated thus : — The plugs were withdrawn and the 
bulbs were exposed in the vertical position for six hours to the contact of unfiltered air ; 
they were then replugged and boiled briskly over the flame for five minutes. Of these, 
three germinated within four days, and three remained permanently barren. 
The second set (six bulbs) were also unplugged, and a little ordinary water (from one 
to sixty drops) was introduced into the bulbs ; they were then replugged and boiled for 
five minutes. Four of these germinated and two remained barren. 
The third set, consisting of four bulbs, were unplugged, and a few drops of an alka- 
lized hay-infusion turbid from Bacteria were added to each ; these were then replugged 
and boiled for five minutes. All of these germinated. 
Lastly, the five barren bulbs of the first and second sets, after remaining barren for a 
month, were unplugged again and infected with alkalized hay-infusion turbid with 
Bacteria. They were then replugged and boiled for five minutes. All germinated in 
four days. 
These experiments prove directly and positively that there exist in ordinary air and 
water particles which, in certain liquids, are capable of preserving their germinal 
activity after exposure to a boiling heat for five minutes. They also prove that certain 
types of Bacteria , or their germs, are capable of surviving a similar heat. 
If these experiments are regarded in conjunction with those published by Dr. Bastian* 
and F. Cohn "j*, it would seem that the vital resistance to heat of Bacteria and their 
germs varies greatly according to the nature of the liquid in which they subsist, and 
probably also according to the species or type of Bacteria. It does not seem unrea- 
sonable to suppose that different races of Bacteria , or different phases of their develop- 
ment, are capable of offering very different degrees of resistance to the destructive 
influences of heatj. 
B. We have seen that unneutralized hay-infusion is sterilized by exposure to a boil- 
ing heat for five minutes ; but if the infusion be slightly alkalized by ammonia or potash, 
it germinates after exposure to the same heat for more than an hour. How does the 
* Proc. Eoy. Soc., March 20, 1873 (vol. xxi. p. 224). 
t Beitrage zur Biologie d. Pflanzen, 2 te8 Heft, p. 217. 
J I may refer again on this point to the paper of Dallinger and Drysdale already cited. These observers 
found that while adult cercomonads were killed at a temperature of 60° C. their spores survived a heat 
of 127° C. 
T. Pace (Maandhlad v. Natuur-Wettenschappen, May 1873) found that Bacteria in turnip -infusion with 
cheese retained their normal appearances and movements after being heated in closed tubes up to 160° C . ; 
but as their subsequent power of growing and multiplying was not tested, these experiments must he regarded 
as inconclusive. The same objection lies against the experiments of the late Dr. Crace-Calvert (Proc. Eoy. Soc. 
1871, vol. xix. p. 468). 
MDCCCLXXIV. 3 R 
