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injecting them with weakened microbes." Pasteur assured them that: "The general principles have been found and one cannot refuse to believe that the future is rich with the greatest hopes."

"We are all animated with a superior passion, the passion for progress and for truth!" he shouted—but unhappily he said no word about those numerous occasions when his vaccine had killed sheep instead of protecting them.

At this meeting Robert Koch sat blinking at Pasteur behind his gold-rimmed spectacles and smiling under his weedy beard at such an unscientific inspirational address. Pasteur seemed to feel something hanging over him, and he challenged Koch to argue with him publicly—knowing that Koch was a much better microbe hunter than an argufier. "I will content myself with replying to Mr. Pasteur's address in a written paper, in the near future," said Koch—who coughed, and sat down.

In a little while this reply appeared. It was dreadful. In this serio-comic answer Dr. Koch began by remarking that he had obtained some of this precious so-called anthrax vaccine from the agent of Mr. Pasteur.

Did Mr. Pasteur say that his first vaccine would kill mice, but not guinea-pigs? Dr. Koch had tested it, and it wouldn’t even kill mice. But some queer samples of it killed sheep!

Did Mr. Pasteur maintain that his second vaccine killed guinea-pigs but not rabbits? Dr. Koch had carefully tested this one too, and found that it often killed rabbits very promptly—and sometimes sheep, poor beasts! which Mr. Pasteur claimed it would guard from death.

Did Mr. Pasteur really believe that his vaccines were really pure cultivations containing nothing but anthrax microbes? Dr. Koch had studied them carefully and found them to be veritable menageries of hideous scum-forming bacilli and strange cocci and other foreign creatures that had no business there.

Finally, was Mr. Pasteur really burning so with a passion for truth? Then why hadn't he told of the bad results as well