58 
Pasteur and his Work, 
in order to exist and multiply, and which he named cerobies ; and 
another which could live actively in the absence of free oxygen, 
possessing itself of this essential element by taking it from its 
combinations in the food supplied to it — this class he de- 
signated anairobies, and its discovery caused much astonishment.* 
Dumas, the celebrated chemist, said one day at the Academy 
of Sciences, in addressing Pasteur in reference to the last-named 
class : " In these infinitely small organisms you have discovered 
a third kingdom — the kingdom to which these organisms 
belong, which, with all the attributes of animal life, do not 
require air for their existence, and which find the heat that is 
necessary for them in the chemical decompositions they set up 
around them." 
The potency of the anaerobic class to act as ferments, it may 
be observed, depends upon their capacity to live without air, by 
breaking down pre-existing compounds, and forming new and 
simpler ones ; this done, they perish, and then the aerobic germs 
may, in their turn, live upon them, and convert their remains 
into other compounds. 
Carefully conducted experiments demonstrated that fluid or- 
ganic matters deprived of all microscopic germs, retained free 
•oxygen for any length of time, and remained unchanged ; but if 
living germs were allowed access to such matters when kept in 
closed vessels, in a few days there was no oxygen, but carbonic 
acid. So it was proved that, contrary to the notion previously 
entertained, oxygen has but little influence in promoting de- 
composition when germs are absent ; though when they are 
present it acts most powerfully. 
Putrefaction is simply fermentation, the sole agent in one as 
in the other being microscopic organisms, the fermentation of 
sugar being simply the putrefaction of sugar. It had long been 
known that fungi, or microscopic animalculae, were present in 
putrefying organic compounds ; but that they were the real agents 
in effecting putrefaction was not proved, and by such authorities 
as Liebig was even denied. Here, again, Pasteur showed that 
the destruction of animal and vegetable matter was a process 
of slow combustion, brought about by appropriation of oxygen 
from the air, through the instrumentality of the aerobies, which, 
in reality, have the faculty of consuming the oxygen, and are 
the powerful agents in restoring to the atmosphere and the soil 
the elements of things which have lived. Mildew, mould, and 
other cell-formations, two thousand of which would not measure 
a millimetre, carry on the great work of maintaining the equi- 
librium between life and death — they themselves dying and 
* I venture to expre.ss my idea that the bearing of this discovery upon the 
phenomena attending tlio production of sweet and sour ensilage respectively may 
be worthy ol' careful investigation. — Edit. 
