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into a fresh drop of the watery fluid of ox-eyes, or the instant he stuck them, on one of his thin slivers, into the root of a mouse's tail.

"These spores never form in an animal while he is still alive—they only appear after he has died, and then only when he is kept very warm," said Koch, and he proved this beautifully by clapping spleens into an ice chest—and in a few days this stuff, smeared on splinters, was no more dangerous than if he had shot so much beefsteak into his mice.

It was now the year 1876, and Koch was thirty-four years old, and at last he emerged out of the bush of Wollstein, to tell the world—stuttering a little—that it was at last proved that microbes were the cause of disease. Koch put on his best suit and his gold-rimmed spectacles and packed up his microscope, a few hanging-drops in their glass cells, swarming with murderous anthrax bacilli; and besides these things he bundled a cage into the train with him, a cage that bounced a little with several dozen healthy white mice. He took a train for Breslau to exhibit his anthrax microbes and the way they kill mice, and the weird way in which they turn into glassy spores—he wanted to demonstrate these things to old Professor Cohn, the botanist at the University, who had sometimes written him encouraging letters.

Professor Cohn, who had been amazed at the marvelous experiments about which the lonely Koch had written him, old Cohn snickered when he thought of how this greenhorn doctor—who had no idea, himself, of how original he was—would surprise the highbrows of the University. He sent out invitations to the most eminent medicoes of the school to come to the first night of Koch's show.

And they came. To hear the unscientific backwoodsman—they came. They came maybe out of friendliness to old Professor Cohn. But Koch didn't lecture—he was never much at