ON THE MOLECULAR ORIGIN OF INFUSORIA. 
63 
decoction of barley which had been boiling for six hours. A 
stopper was introduced into it below the liquid, and on taking 
it out the whole neck of the flask was immediately plunged into 
melting sealing-wax, and hermetically closed. In six days 
some yeast was observed in it, at a temperature of 18° cent. 
The following day the temperature was raised suddenly to 27°, 
when the flask burst, and then it was seen by the naked eye, 
and by the microscope, that it contained a notable quantity of 
yeast.^ Now, yeast is a plant, which was thus proved to have 
grown in an infusion that had long been boiling, and from which 
all atmospheric air had been expelled. 
As, therefore, neither calcined air, sulphuric acid, liquor 
potassse, gun-cotton, or a boiling temperature have failed to 
prevent the production of infusoria, or destroy the supposed 
germs in the air or infusion, I determined, in 1863, to try the 
effects of all these destructive agents, with the exception of the 
first, at once, and with the greatest possible care. The results 
of numerous experiments carried on in this manner and varied 
in many ways demonstrate that when nothing but air, exposed 
to and filtered through agents most destructive to animal and 
vegetable life, is brought into contact with organic liquids, in- 
fusoria are still produced. 
It is now admitted by M. Pasteur that the boiling tempera- 
ture, that is, 100° centigrade, does not prevent the growth of 
the supposed germs in the atmosphere; but instead of consider- 
ing this fact hostile to his theory, he concludes from it that the 
germs have the power of resisting that amount of heat, and of 
being most tenacious of life; but he says 130° centigrade 
always destroys their vitality. M. Pouchet, however, has shown 
that the air, and the organic matter when placed in boiling 
w^ater, will germinate after they have been exposed to a heat 
of even 150°, and he says it may be raised to 200° centigrade, 
and yet animalcules and fungi will develop themselves.f 
In the same manner, air and infusions exposed to intense 
cold still produce animalcules, but, according to Pasteur, not so 
readily. Twenty flasks containing boiled infusions, and from 
which the air was expelled, were opened by him with excessive 
precaution on the Mer de Glace at Montan vert on the Jura. 
Notwithstanding the purity and extreme coldness of the air 
infusoria appeared in five of his flasks. 
As an illustration of the manner in which the controversy on 
this subject has been carried on in the Imperial Academy of 
Sciences in Paris, I may give a short account of that portion of 
it referring to the Glacier experiments. MM. Pouchet, Jolly, 
and Musset opened eight similar flasks used by M. Pasteur at 
* Heterog(^nie,” p. 629. 
f Comptes-Reudiis,” tome 1. p. 1015. 
