“The confusion and uncertainty,” wrote Tyndall to Pasteur, “have finally become such that, six months ago, I thought that it would be rendering a service to Science, at the same time as justice to yourself, if the question were subjected to a fresh investigation.
“Putting into practice an idea which I had entertained six years ago—the details of which are set out in the article in the British Medical Journal which I had the pleasure to send you—I went over a large portion of the ground on which Dr. Bastian had taken up his stand, and refuted, I think, many of the fallacies which had misled the public.
“The change which has taken place since then in the tone of the English medical journals is quite remarkable, and I am disposed to think that the general confidence of the public in the accuracy of Dr. Bastian’s experiments has been considerably shaken.
“In taking up these investigations, I have had the opportunity of refreshing my memory about your labours; they have reawakened in me all the admiration which I felt for them when I first read of them. I intend to continue these investigations until I have dispersed all the doubts which may have arisen as to the indisputable accuracy of your conclusions.”
And Tyndall added a paragraph for which Pasteur modestly substituted asterisks in communicating this letter to the Academy.
“For the first time in the history of Science we have the right to cherish the sure and certain hope that, as regards epidemic diseases, medicine will soon be delivered from quackery and placed on a real scientific basis. When that day arrives, Humanity, in my opinion, will know how to recognize that it is to you that will be due the largest share of her gratitude.”
Tyndall was indeed qualified to sign this passport to immortality. But in the meanwhile a struggle was necessary, and Pasteur did not wish to leave the burden of the discussion even on such shoulders as Tyndall’s! Moreover he was interested in his opponent.
“Dr. Bastian,” writes M. Duclaux, “had some tenacity, a fertile mind, and the love, if not the gift, of the experimental method.” The discussion was destined to last for months. In general (according to J. B. Dumas’ calculation) “at the end of ten years, judgment on a great thing is usually formed; it is by then an accomplished fact, an idea adopted by Science or irrevocably repudiated.” Pasteur, on the morrow of the Milan Congress, might feel that it had been so for the adoption of his system of cellular seeding, but such was not the case in this question of spontaneous generation. The quarrel had started again at the Academy of Sciences and at the Academy of Medicine; it was now being revived in England, and Bastian proposed to come himself and experiment in the laboratory of the Ecole Normale.
“For nearly twenty years,” said Pasteur, “I have pursued, without finding it, a proof of life existing without an anterior and similar life. The consequences of such a discovery would be incalculable; natural science in general, and medicine and philosophy in particular, would receive therefrom an impulse which cannot be foreseen. Therefore, whenever I hear that this discovery has been made, I hasten to verify the assertions of my fortunate rival. It is true that I hasten towards him with some degree of mistrust, so many times have I experienced that, in the difficult art of experimenting, the very cleverest stagger at every step, and that the interpretation of facts is no less perilous.”
Dr. Bastian operated on acid urine, boiled and neutralized by a solution of potash heated to a temperature of 120° C. If, after the flask of urine had cooled down, it was heated to a temperature of 50° C. in order to facilitate the development of germs, the liquid in ten hours’ time swarmed with bacteria. “Those facts prove spontaneous generation,” said Dr. Bastian.