But nothing stopped him; neither Balard’s public advice, his pupils’ letters, even J. B. Dumas’ imploring looks. He could not keep himself from replying. Sometimes he regretted his somewhat sharp language, though--in his own words--he never associated it with feelings of hostility towards his contradictors as long as he believed in their good faith; what he wanted was that truth should have the last word. “What _you_ lack, M. Frémy, is familiarity with a microscope, and you, M. Trécul, are not accustomed to laboratories!” “M. Frémy is always trying to displace the question,” said Pasteur, ten months after M. Balard’s appeal. Whilst M. Frémy disputed, discussed, and filled the Académie with his objections, M. Trécul, whose life was somewhat misanthropical and whose usually sad and distrustful face was seen nowhere but at the Institute, insisted slowly, in a mournful voice, on certain transformations of divers cells or spores from one into the other. Pasteur declared that those ideas of transformation were erroneous; but--and there lay the interest of the debate--there was one of those transformations that Pasteur himself had once believed possible: that of the _mycoderma vini_, or wine flower, into an alcoholic ferment under certain conditions of existence. A modification in the life of the mycoderma when submerged had led him to believe in a transformation of the mycoderma cells into yeast cells. It was on this question, which had been left in suspense, that the debate with Trécul came to an end, leaving to the witnesses of it a most vivid memory of Pasteur’s personality--inflexible when he held his proofs, full of scruples and reserve when seeking those proofs, and accepting no personal praise if scientific truth was not recognized and honoured before everything else. On November 11 Pasteur said: “Four months ago doubts suddenly appeared in my mind as to the truth of the fact in question, and which M. Trécul still looks upon as indisputable.... In order to disperse those doubts I have instituted the most numerous and varied experiments and I have not succeeded through those four months in satisfying myself by irrefragable proofs; I still have my doubts. Let this example show to M. Trécul how difficult it is to conclude definitely in such delicate studies.”