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work, well done, Koch took his tubes and put them in the oven—at the exact temperature of a guinea-pig's body.

Day after day Koch hurried in the morning to his incubating oven, and took out his tubes and held them close to his gold-rimmed glasses, and saw—nothing.

"Well, I have failed again," he mumbled—it was the fourteenth day after he had planted his consumptive stuff—"every other microbe I have ever grown multiplies into large colonies in a couple of days, but here, confound it—there is nothing, nothing . . ."

Any other man would have pitched these barren disappointing serum-tubes out, but at this stubbly-haired country doctor's shoulder his familiar demon whispered: "Wait—be patient, my master—you know that tubercle germs sometimes take months, years to kill men. Maybe too they grow very slowly in the serum tubes." So Koch did not pitch the tubes out, and on the morning of the fifteenth day he came back to his incubator—to find the velvety surface of the serum jelly covered with tiny glistening specks! Koch reached a trembling hand for his pocket lens, clapped it to his eye and peered at one tube after another, and through his lens these glistening specks swelled out into dry tiny scales. . . .

In a daze Koch pulled the cotton plug out of one of his tubes, mechanically he flamed its mouth in the sputtering blue fire of the Bunsen burner, with a platinum wire he picked off one of these little flaky colonies—they must be microbes—and not knowing how or what, he got them before his microscope. . . .

Then he knew that he had got to a warm inn on the stony road of his adventure—here they were, countless myriads of these same bacilli, these crooked rods that he had first spied in the lung of the dead workman. They were motionless but surely multiplying and alive—they were delicate and finicky about their food and feeble in size, but more savage than hordes of Huns and more murderous than ten thousand nests of rattlesnakes.