ON FERMENTATION-PRODUCING INFUSORIA. 457 
A special butyric ferment must therefore exist. On this point I 
have fixed for some time my undivided attention; and the present 
communication is devoted to this question, that is to say, to the origin 
of butyric acid in the so-called lactic fermentation. Without entering 
here into all the details of my experiments, I may state at once the 
following result, namely : that the butyric ferment consists of a species 
of infusoria. So far was I from expecting this result, that for some 
time I did my best to prevent the development of the infusoria, fearing 
that these minute creatures lived upon the supposed vegetable fer- 
ment which I thought gave rise to the butyric fermentation, and which 
I sought to discover in the liquid media employed in my researches. 
But failing to make out the origin of the butyric acid, I finished by 
being struck with the remarkable coincidence between the presence of 
this acid and the infusoria, the one always accompanying the other ; 
and since then, an extended series of experiments has convinced me 
that to these infusoria is exclusively due the transformation of sugar, 
mannite, and lactic acid, into butyric acid. We must therefore, con- 
sider these »ninute animals as the true butyric ferment. 
With regard to their description, it may be stated that they form 
small and usually straight cylindrical lines, rounded at the extremities, 
and either free, or united in chains of two, three, four, or even a larger 
number of individuals. The isolated forms are about 0°002 of a 
millimeter in breadth, and are from 0-002 to 0 05 or 0-02 in length. 
They move with a gliding (or jerking) motion, the body either remain- 
ing rigid, or exhibiting slight undulations. At times also, they turn 
upon themselves, and cause the extremities of their body to vibrate 
rapidly. The undulatory movements of the body become very evident 
when the length reaches 0-015 of a millimeter. One extremity is fre- 
quently curved, and occasionally both ends of the body exhibit a 
curvature, but curved forms are rare at the commencement of life. 
The reproduction is fissiparous ; and to this mode of generation the 
chain-like groupings are evidently due. In these chains, the last 
individual may frequently be observed in comparatively violent motion 
in its attempts to detach itself from the rest, 
Although, as I have said, the body of these Vibrionide is cylindri- 
cal in form, it often appears to be made up of a faintly-marked 
series of very short articulations. These undoubtedly represent the 
first stage in the development of the infusoria. 
