Hurriedly Pasteur and Roux and Chamberland set out to confirm the first chance observation they had made. They let virulent chicken cholera microbes grow old in their bottles of broth; they inoculated these enfeebled bugs into dozens of healthy chickens--which promptly got sick, but as quickly recovered. Then triumphantly, a few days later, they watched these birds--these _vaccinated_ chickens--tolerate murderous injections of millions of microbes, enough to kill a dozen new birds who were not immune. So it was that Pasteur, ingeniously, turned microbes against themselves. He tamed them first, and then he strangely used them for wonderful protective weapons against the assaults of their own kind. And now Pasteur, with his characteristic impetuousness--after all it was only chickens he had learned to guard from death so far--became more arrogant than ever with the old-fashioned doctors who talked Latin words and wrote shot-gun prescriptions. He went to a meeting of the Academy of Medicine and with complaisance told the doctors how his chicken vaccinations were a great advance on the immortal smallpox discovery of Jenner: “In this case I have demonstrated a thing that Jenner never could do in smallpox--and that is, that the microbe that kills is the same one that guards the animal from death!” The old-fashioned blue-coated doctors were peeved at Pasteur’s appointing himself a god superior to the great Jenner; Doctor Jules Guérin, the famous surgeon, became particularly sarcastic about Pasteur making so much of mere fussings with chickens--and the fight was on. Pasteur, in a fury got up and shouted remarks about the utter nonsensicality of one of Guérin’s pet operations, and there occurred a most scandalous scene--it embarrasses me to have to tell about it--a strange shambles in which Guérin, who was past eighty, rose from his seat and was about to fall on the sixty-year-old Pasteur. The old man aimed a wallop at Pasteur, but frantic friends jumped in and prevented the impending fisticuffs of these two men who thought they could settle the truth by kicks and blows and mayhem. Next day the ancient Guérin sent his seconds to Pasteur with a challenge to a duel, but Pasteur, evidently, did not care to risk dying that way and he sent Guérin’s friends to the Secretary of the Academy with this message: “I am ready, having no right to act otherwise, to modify whatever the editors may consider as going beyond the rights of criticism and legitimate defense.” And so Pasteur once more proved himself to be a human being--if not what is commonly called a man--by backing out of the fight.