Animalcules Living Without Free Oxygen
Comptes rendus de
l'Académie des sciences 52 (February 25, 1861): 344-47; Reprinted in
Oeuvres de Pasteur,
vol. 2, pp. 136-38.
Translation by A.S. Weber.
The variety of products
formed by the so-called lactic
fermentation are well known.
Lactic acid, a gum, mannite, butyric acid, alcohol, carbonic acid and
hydrogen appear simultaneously or successively in extremely variable and
quite unexpected proportions. I have slowly realized that the vegetable
ferment which transforms sugar into lactic acid is different from the one or
ones (because there are two of them) which determine the production of the
gummy material, and that these ferments do not produce lactic acid.
Moreover, I have also recognized that these various vegetable ferments, if
they are perfectly pure, can in no way give rise to butyric acid.
Therefore there must be
a specific butyric ferment. I have focussed my attention on this point for a
long time. The communication which I have the honor of addressing to the
Academy today precisely concerns the origin of butyric acid in the so-called
lactic acid fermentation. I will not enter here into all the details of this
research. I will first limit myself to announcing one of the conclusions of
my work: that is, the butyric
ferment is an infusorian.
I had been prepared not
to expect this result, to such a degree that for a long time I felt
compelled to prevent the appearance of these little animals, for fear that
they were not drawing nourishment from the vegetable ferment which I had
assumed to be the butyric ferment, the same vegetable ferment which I was
searching to discover in the liquid media that I was using. But unsuccessful
in uncovering the cause of the origin of the butyric acid, I was in the end
struck by the coincidence, that my analyses showed me to be inevitable,
between the acid and the infusoria, and conversely between the infusoria and
the production of the acid, a fact that I had previously attributed to the
favorable and suitable environment that the butyric acid provided to these
animalcules. Since then, a great number of experiments have convinced me
that the transformation of sugar, mannite, and lactic acid into butyric acid
is due exclusively to these infusoria, and that it is necessary to consider
them as the true butyric ferment.
The infusoria can be
described as follows: they are little cylindrical rods, rounded at the ends,
ordinarily straight, and either isolated or joined in chains of two, three,
four or sometimes even more divisions. On average, their size is 0.002 mm.
The length of one of the isolated divisions varies from 0.002 mm to 0.015 mm
to 0.02 mm. These infusoria propel themselves by gliding. During this
movement, their bodies stay rigid, or undergo light undulations. They
pirouette, balancing themselves where the anterior or posterior part of
their bodies vibrates rapidly. The undulations of their movements become
very evident as soon as their length reaches 0.015 mm. Often they are bent
back towards one of their extremities, sometimes to both. This peculiarity
is rare at the beginning of their lives.
They reproduce by
fissiparity [division]. The chains of divisions which some of their bodies
join into are evidently a result of this mode of reproduction. A single
infusorian which drags other bodies after itself sometimes rapidly shakes as
if to detach itself.
Although the bodies of
these vibrios have a cylindrical appearance, one might say that they are
often formed from a series of particles or very short, scarcely begun
divisions which are without doubt the rudimentary beginnings of these little
One can sow these
infusoria just like one would sow beer yeast. They multiply if the
environment is adapted to their nutrition. But it is essential to remark
here that one can sow them in a liquid containing only sugar, ammonia, and
phosphates; that is to say, crystalline and completely mineral substances,
and they reproduce themselves in correlation with the butyric fermentation,
which appears very evident. The weight formed from this process is notable,
although always small when compared to the total quantity of butyric acid
produced, just as in all ferments.
The existence of
infusoria possessing the character of ferments is already a fact which
certainly seems worthy of attention; but one unique peculiarity accompanies
this fact-these infusorian animalcules live and multiply without limit
without the necessity of providing them with the least quantity of air or
It would be tedious to
recount here how I absolutely excluded oxygen from the interiors and
surfaces of the liquid media where these infusoria live and swarm by the
millions, since I have carefully established this elsewhere. I will only add
that I did not want to present my findings to the Academy without calling
several of its members to witness, who appeared to acknowledge the rigor of
the experimental proofs which I placed before their eyes.
Not only do these
infusoria live without air, but the air kills them. If one passes a stream
of pure carbonic acid for an unspecified amount of time through the liquid
in which they live, their life and reproduction are in no way affected. If,
on the contrary, a stream of atmospheric air is substituted for the carbonic
acid under exactly the same conditions, in only one or two hours the
infusoria all die, and the butyric fermentation connected to their existence
is soon stopped.
Thus we arrive at this
1. The butyric ferment is an infusorian.
2. This infusorian lives without free oxygen
This is, I believe, the
first known example of animal ferments, and also of animals living without
free oxygen gas.
The comparison of the
way of life and properties of these animalcules with the way of life and
properties of the vegetable ferments who live equally without the aid of
free oxygen, is selfevident, along with the consequences that may be deduced
from it relating to the cause of fermentations. However, I would like to
reserve the ideas which these new facts suggest until I have submitted them
to the light of experiment.