Koch was spending his evenings fussing with his new microscope, he was beginning to find out just the right amount of light to shoot up into its lens with the reflecting mirror, he was learning just how needful it was to have his thin glass slides shining clean--those bits of glass on which he liked to put drops of blood from the carcasses of sheep and cows, that had died of anthrax.... Anthrax was a strange disease which was worrying farmers all over Europe, that here and there ruined some prosperous owner of a thousand sheep, that in another place sneaked in and killed the cow--the one support--of a poor widow. There was no rime or reason to the way this plague conducted its maraudings; one day a fat lamb in a flock might be frisking about, that evening this same lamb refused to eat, his head drooped a little--and the next morning the farmer would find him cold and stiff, his blood turned ghastly black. Then the same thing would happen to another lamb, and a sheep, four sheep, six sheep--there was no stopping it. And then the farmer himself, and a shepherd, and a woolsorter, and a dealer in hides might break out in horrible boils--or gasp out their last breaths in a swift pneumonia. Koch had started using his microscope with the more or less thorough aimlessness of old Leeuwenhoek; he examined everything under the sun, until he ran on to this blood of sheep and cattle dead of anthrax. Then he began to concentrate, to forget about making a call when he found a dead sheep in a field--he haunted butcher shops to find out about the farms where anthrax was killing the flocks. Koch hadn’t the leisure of Leeuwenhoek; he had to snatch moments for his peerings, between prescribing for some child that bawled with a bellyache and the pulling out of a villager’s aching tooth. In these interrupted hours he put drops of the blackened blood of a cow dead of anthrax between two thin pieces of glass, very clean shining bits of glass. He looked down the tube of his microscope and among the wee round drifting greenish globules of this blood he saw strange things that looked like little sticks. Sometimes these sticks were short, there might be only a few of them, floating, quivering a little, among the blood globules. But here were others, hooked together without joints--many of them ingeniously glued together till they appeared to him like long threads a thousand times thinner than the finest silk.