Our researches concerning the septic vibrio had not so far been convincing, and it was to fill up this gap that we resumed our experiments.  To this end, we attempted the cultivation of the septic vibrio from an animal dead of septicemia.  It is worth noting that all of our first experiments failed, despite the variety of culture media we employed—­urine, beer yeast water, meat water, etc.  Our culture media were not sterile, but we found—­most commonly—­a microscopic organism showing no relationship to the septic vibrio, and presenting the form, common enough elsewhere, of chains of extremely minute spherical granules possessed of no virulence whatever. [Footnote:  It is quite possible that Pasteur was here dealing with certain septicemic streptococci that are now know to lose their virulence with extreme rapidity under artificial cultivation.—­Translator.] This was an impurity, introduced, unknown to us, at the same time as the septic vibrio; and the germ undoubtedly passed from the intestines—­always inflamed and distended in septicemic animals—­ into the abdominal fluids from which we took our original cultures of the septic vibrio.  If this explanation of the contamination of our cultures was correct, we ought to find a pure culture of the septic vibrio in the heart’s blood of an animal recently dead of septicemia.  This was what happened, but a new difficulty presented itself; all our cultures remained sterile.  Furthermore this sterility was accompanied by loss in the culture media of (the original) virulence.

It occurred to us that the septic vibrio might be an obligatory anaerobe and that the sterility of our inoculated culture fluids might be due to the destruction of the septic vibrio by the atmospheric oxygen dissolved in the fluids.  The Academy may remember that I have previously demonstrated facts of this nature in regard to the vibrio of butyric fermentation, which not only lives without air but is killed by the air.

It was necessary therefore to attempt to cultivate the septic vibrio either in a vacuum or in the presence of inert gases—­such as carbonic acid.

Results justified our attempt; the septic vibrio grew easily in a complete vacuum, and no less easily in the presence of pure carbonic acid.

These results have a necessary corollary.  If a fluid containing septic vibrios be exposed to pure air, the vibrios should be killed and all virulence should disappear.  This is actually the case.  If some drops of septic serum be spread horizontally in a tube and in a very thin layer, the fluid will become absolutely harmless in less than half a day, even if at first it was so virulent as to produce death upon the inoculation of the smallest portion of a drop.

Furthermore all the vibrios, which crowded the liquid as motile threads, are destroyed and disappear.  After the action of the air, only fine amorphous granules can be found, unfit for culture as well as for the transmission of any disease whatever.  It might be said that the air burned the vibrios.