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--