230 THE LIFE OF PASTEUR 



A few months later, on November 17, 1873, he read to the 

 Academy a paper containing further developments of his prin- 

 ciples. " In order that beer should become altered and become 

 sour, putrid, slimy, ' ropy,' acid or lactic, it is necessary that 

 foreign organisms should develop within it, and those or- 

 ganisms only appear and multiply when those germs are 

 already extant in the liquid mass." It is possible to oppose 

 the introduction of those germs ; Pasteur drew on the black- 

 board the diagram of an apparatus which only communicated 

 with the outer air by means of tubes fulfilling the office of 

 the sinuous necks of the glass vessels he had used for his 

 experiments on so-called spontaneous generation. He entered 

 into every detail, demonstrating that as long as pure yeast 

 alone had been sown, the security was absolute. " That which 

 has been put forward on the subject of a possible transforma- 

 tion of yeast into bacteria, vibriones, mycoderma aceti and 

 vulgar mucors, or vice versa, is mistaken." 



He wrote in a private letter on the subject : " These simple 

 and clear results have cost me many sleepless nights before 

 presenting themselves before me in the precise form I have 

 now given them." 



But his own conviction had not yet penetrated the minds 

 of his adversaries, and M. Trecul was still supporting his 

 hypothesis of transformations, the so-called proofs of which, 

 according to Pasteur, rested on a basis of confused facts tainted 

 with involuntary errors due to imperfect experiments. 



In December, 1873, at a sitting of the Academy, he pre- 

 sented M. Tre"cul with a few little flagons, in which he had 

 sown some pure seed of penicillium glaucum, begging him to 

 accept them and to observe them at his leisure, assuring him 

 that it would be impossible to find a trace of any transformation 

 of the spores into yeast cells. 



"When M. Tre"cul has finished the little task which I am 

 soliciting of his devotion to the knowledge of truth," con- 

 tinued Pasteur, "I shall give him the elements of a similar 

 work on the mycoderma vini] in other words, I shall bring to 

 M. Trecul some absolutely pure mycoderma vini with which 

 he can reproduce his former experiments and recognize the 

 exactness of the facts which I have lately announced." 



Pasteur concluded thus : ' ' The Academy will allow me to 

 make one last remark. It must be owned that my contra- 

 dictors have been peculiarly unlucky in taking the occasion 



