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hunter than Leeuwenhoek, certainly he was just as much of a self-made scientist. Koch was poor, he had his nose on the grindstone of a medical practice, all the science he knew was what a common medical course had taught him—and from this, God knows, he had learned nothing whatever about the art of doing experiments; he had no apparatus but Emmy's birthday present, that beloved microscope—everything else he had to invent and fashion out of bits of wood and strings and sealing wax. Worst of all, when he came into the living room from his mice and microscope to tell Frau Koch about the new strange things he had discovered, this good lady wrinkled up her nose and told him:

"But, Robert, you smell so!"

Then he hit upon a sure way to give mice the fatal disease of anthrax. He hadn't a convenient syringe with which to shoot the poisonous blood into them, but after sundry cursings and the ruin of a number of perfectly good mice, he took slivers of wood, cleaned them carefully, heated them in an oven to kill any chance ordinary microbes that might be sticking to them. These slivers he dipped into drops of blood from sheep dead of anthrax, blood filled with the mysterious, motionless threads and rods, and then—heaven knows how he managed to hold his wiggling mouse—he made a little cut with a clean knife at the root of the tail of the mouse, and into this cut he delicately slid the blood-soaked splinter. He dropped this mouse into a separate cage and washed his hands and went off in a kind of conscientious wool-gathering way to see what was wrong with a sick baby. . . . "Will that beast, that mouse die of anthrax. . . . Your child will be able to go back to school next week, Frau Schmidt. . . . I hope I didn't get any of that anthrax blood into that cut on my finger. . . ." Such was Koch's life.

And next morning Koch came into his home-made laboratory—to find the mouse on its back, stiff, its formerly sleek fur standing on end and its whiteness of yesterday turned into a leaden blue, its legs sticking up in the air. He heated his