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surely—against the one disease of which the microbe in the vaccine is the cause.

But one of Pasteur's most charming traits was his characteristic of a scientific Phœnix, who rose triumphantly from the ashes of his own mistakes. When his imagination carried him into the clouds you find him presently landing on the ground with a bump—making clever experiments again, digging for good true hard facts. So it is not surprising to find him, with Roux and Chamberland, in 1881, discovering a very pretty way of taming vicious anthrax microbes and turning them into a vaccine. By this time the quest after vaccines had become so violent that Roux and Chamberland hardly had their Sundays off, and never went on vacations; they slept at the laboratory to be near their tubes and microscopes and microbes. And here, Pasteur directing them, they delicately weakened anthrax bacilli so that some killed guinea-pigs, but not rabbits, and others did mice to death, but were too weak to harm guinea-pigs. They shot the weaker and then the stronger microbes into sheep, who got a little sick but then recovered, and after that these sheep could stand, apparently, the assaults of vicious anthrax germs that were able to kill even a cow.

At once Pasteur told this new triumph to the Academy of Sciences—he had left off going to the Academy of Medicine after his brawl with Guérin—and he held out purple hopes to them that he would presently invent ingenious vaccines that would wipe out all diseases from mumps to malaria. "What is more easy," he shouted, "than to find in these successive viruses a vaccine capable of making sheep and cows and horses a little sick with anthrax without letting them perish—and so preserving them from subsequent maladies?" Some of Pasteur's colleagues thought he was a little cocksure about this, and they ventured to protest. Pasteur's veins stood out on his forehead, but he managed to keep his mouth shut until he and Roux were on the way home, when he burst out, speaking really of all people who failed to see the absolute truth of his idea: