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microbes are tough. And among the tough lot of them there are super-hardy ones. These beasts, when a Jew and a Japanese come along to have at them with a bright-colored dye, lap up that dye. They like it! Or they retreat discreetly to some out-of-the-way place in a mouse's carcass. There they wait their time to multiply in swarms. . . .

So, for his first little success, Paul Ehrlich paid with a thousand disappointments. The trypanosome of David Bruce's nagana and the deadly trypanosome of human sleeping sickness laughed at that trypan red! They absolutely refused to be touched by it! Then, what worked so beautifully with mice, failed completely when they came to try it on white rats and guinea-pigs and dogs. It was a grinding work, to be tackled only by such an impatient persistent man as Ehrlich, for had he not saved one mouse?—What waste! He used thousands of animals! I used to think, in the arrogance of my faith in science: "What waste!" But no. Or call it waste if you like, remembering that nature gets her most sublime results—so often—by being lavishly wasteful. And then remember that Paul Ehrlich had learned one lesson: change an apparently useless dye, a little, and it turns from a merely pretty color into something of a cure. That was enough to drive forward this too confident man.

All the time the laboratory was growing. To the good people of Frankfort Paul Ehrlich was a savant who understood all mysteries, who probed all the riddles of nature, who forgot everything. And how the people of Frankfort loved him for being so forgetful! It was said that this Herr Professor Doktor Ehrlich had to write himself postal cards several days ahead to remind himself of festive events in his family. "What a human being!" they said. "What a deep thinker!" said the cabbies who drove him every morning to his Institute. "That must be a genius!" said the grind-organ musicians whom he tipped heavily once a week to play dance music in the garden by the laboratory. "My best ideas come when I hear gay music like that," said Paul Ehrlich, who detested all highbrow