Pasteur started for Arbois, taking with him seventy-three flasks; he opened twenty of them not very far from his father’s tannery, on the road to Dôle, along an old road, now a path which leads to the mount of the Bergère. The vine labourers who passed him wondered what this holiday tourist could be doing with all those little phials; no one suspected that he was penetrating one of nature’s greatest secrets. “What would you have?” merrily said his old friend, Jules Vercel; “it amuses him!” Of those twenty vessels, opened some distance away from any dwelling, eight yielded organized bodies.
Pasteur went on to Salins and climbed Mount Poupet, 850 metres above the sea-level. Out of twenty vessels opened, only five were altered. Pasteur would have liked to charter a balloon in order to prove that the higher you go the fewer germs you find, and that certain zones absolutely pure contain none at all. It was easier to go into the Alps.
He arrived at Chamonix on September 20, and engaged a guide to make the ascent of the Montanvert. The very next morning this novel sort of expedition started. A mule carried the case of thirty-three vessels, followed very closely by Pasteur, who watched over the precious burden and walked alongside of precipices supporting the case with one hand so that it should not be shaken.
When the first experiments were started an incident occurred. Pasteur has himself related this fact in his report to the Académie. “In order to close again the point of the flasks after taking in the air, I had taken with me an eolipyle spirit-lamp. The dazzling whiteness of the ice in the sunlight was such that it was impossible to distinguish the jet of burning alcohol, and as moreover that was slightly moved by the wind, it never remained on the broken glass long enough to hermetically seal my vessel. All the means I might have employed to make the flame visible and consequently directable would inevitably have given rise to causes of error by spreading strange dusts into the air. I was therefore obliged to bring back to the little inn of Montanvert, unsealed, the flasks which I had opened on the glacier.”
The inn was a sort of hut, letting in wind and rain. The thirteen open vessels were exposed to all the dusts in the room where Pasteur slept; nearly all of them presented alterations.
In the meanwhile the guide was sent to Chamonix where a tinker undertook to modify the lamp in view of the coming experiment.
The next morning, twenty flasks, which have remained celebrated in the world of scientific investigators, were brought to the Mer de Glace. Pasteur gathered the air with infinite precautions; he used to enjoy relating these details to those people who call everything easy. After tracing with a steel point a line on the glass, careful lest dusts should become a cause of error, he began by heating the neck and fine point of the bulb in the flame of the little spirit-lamp. Then raising the vessel above his head, he broke the point with steel nippers, the long ends of which had also been heated in order to burn the dusts which might be on their surface and which would have been driven into the vessel by the quick inrush of the air. Of those twenty flasks, closed again immediately, only one was altered. “If all the results are compared that I have obtained until now,” he wrote, on March 5, 1880, when relating this journey to the Académie, “it seems to me that it can be affirmed that the dusts suspended in atmospheric air are the exclusive origin, the necessary condition of life in infusions.”
And in an unnoticed little sentence, pointing already then to the goal he had in view, “What would be most desirable would be to push those studies far enough to prepare the road for a serious research into the origin of various diseases.” The action of those little beings, agents not only of fermentation but also of disorganization and putrefaction, already dawned upon him.
While Pasteur was going from the Observatoire cellars to the Mer de Glace, Pouchet was gathering air on the plains of Sicily, making experiments on Etna, and on the sea. He saw everywhere, he wrote, “air equally favourable to organic genesis, whether surcharged with detritus in the midst of our populous cities, or taken on the summit of a mountain, or on the sea, where it offers extreme purity. With a cubic decimetre of air, taken where you like, I affirm that you can ever produce legions of microzoa.”
And the heterogenists proclaimed in unison that “everywhere, strictly everywhere, air is constantly favourable to life.” Those who followed the debate nearly all leaned towards Pouchet. “I am afraid,” wrote a scientific journalist in La Presse (1860), “that the experiments you quote, M. Pasteur, will turn against you.... The world into which you wish to take us is really too fantastic....”