Pasteur invited him to replace his boiled solution of potash by a fragment of solid potash, after heating it to 110° C., in order to avoid the bacteria germs which might be contained in the aqueous solution. This question of the germs of inferior organisms possibly contained in water was—during the course of that protracted discussion—studied by Pasteur with the assistance of M. Joubert, Professor of Physics at the Collège Rollin. Such germs were to be found even in the distilled water of laboratories; it was sufficient that the water should be poured in a thin stream through the air to become contaminated. Spring water, if slowly filtered through a solid mass of ground, alone contained no germs.
There was also the question of the urine and that of the recipient. The urine, collected by Dr. Bastian in a vase and placed into a retort, neither of which had been put through a flame, might contain spores of a bacillus called bacillus subtilis, which offer a great resistance to the action of heat. Those spores do not develop in notably acid liquids, but the liquid having been neutralized or rendered slightly alkaline by the potash, the development of germs took place. The thing therefore to be done was to collect the urine in a vase and introduce it into a retort both of which had been put through a flame. After that, no organisms were produced, as was stated in the thesis of M. Chamberland, then a curator at the laboratory, and who took an active part in these experiments.
A chapter might well have been written by a moralist “On the use of certain opponents”; for it was through that discussion with Bastian that it was discovered how it was that—at the time of the celebrated discussions on spontaneous generation—the heterogenists, Pouchet, Joly, and Musset, operating as Pasteur did, but in a different medium, obtained results apparently contradictory to Pasteur’s. If their flasks, filled with a decoction of hay, almost constantly showed germs, whilst Pasteur’s, full of yeast water, were always sterile, it was because the hay water contained spores of the bacillus subtilis. The spores remained inactive as long as the liquid was preserved from the contact of air, but as soon as oxygen re-entered the flask they were able to develop.
The custom of raising liquids to a temperature of 120° C. in order to sterilize them dates from that conflict with Bastian. “But,” writes M. Duclaux, “the heating to 120° of a flask half filled with liquid can sterilize the liquid part only, allowing life to persist in those regions which are not in contact with the liquid. In order to destroy everything, the dry walls must be heated to 180° C.”
A former pupil of the Ecole Normale, who had been a curator in Pasteur’s laboratory since October, 1876, Boutroux by name, who witnessed all these researches, wrote in his thesis: “The knowledge of these facts makes it possible to obtain absolutely pure neutral culture mediums, and, in consequence, to study as many generations as are required of one unmixed micro-organism, whenever pure seed has been procured.”
Pasteur has defined what he meant by putting tubes, cotton, vases, etc., through a flame. “In order to get rid of the microscopic germs which the dusts of air and of the water used for the washing of vessels deposit on every object, the best means is to place the vessels (their openings closed with pads of cotton wool) during half an hour in a gas stove, heating the air in which the articles stand to a temperature of about 150° C. to 200° C. The vessels, tubes, etc., are then ready for use. The cotton wool is enclosed in tubes or in blotting-paper.”
What Pasteur had recommended to surgeons, when he advised them to pass through a flame all the instruments they used, had become a current practice in the laboratory; the least pad of cotton wool used as a stopper was previously sterilized. Thus was an entirely new technique rising fully armed and ready to repel new attacks and ensure new victories.
If Pasteur was so anxious to drive Dr. Bastian to the wall, it was because he saw behind that so-called experiment on spontaneous generation a cause of perpetual conflict with physicians and surgeons. Some of them desired to repel purely and simply the whole theory of germs. Others, disposed to admit the results of Pasteur’s researches, as laboratory work, did not admit his experimental incursions on clinical ground. Pasteur therefore wrote to Dr. Bastian in the early part of July, 1877—
“Do you know why I desire so much to fight and conquer you? it is because you are one of the principal adepts of a medical doctrine which I believe to be fatal to progress in the art of healing—the doctrine of the spontaneity of all diseases.... That is an error which, I repeat it, is harmful to medical progress. From the prophylactic as well as from the therapeutic point of view, the fate of the physician and surgeon depends upon the adoption of the one or the other of these two doctrines.”