For days he saw nothing. His best lenses, that magnified many hundred times, showed him only the dead ruins of what had once been good healthy lung or liver. “If there is a tubercle microbe, he is such a sneaky fellow that I won’t be able, perhaps, to see him in his native state. But I can try painting the tissue with a powerful dye--that may make this bug stand out....” Day after day, Koch set about staining the stuff from the dead workman brown and blue and violet and most of the colors of the rainbow. Carefully, dipping his hands in the germ-killing bichloride of mercury after almost every move--blackening and wrinkling them with it--he smeared the perilous material from the tubercles on thin clean bits of glass and kept these pieces of glass for hours in a strong blue dye.... Then one morning he took his specimens out of their bath of stain, and put them under his lens, and focussed his microscope and out of the gray mist a strange picture untangled itself. Lying among the shattered diseased lung cells were curious masses of little, infinitely thin bacilli--blue-colored rods--so slim that he could not guess their size, and they were less than a fifteen-thousandth of an inch long. “Ah! they are pretty,” he muttered. “They’re not straight like the anthrax bugs ... they have little bends and curves in them. Wait! here are whole bunches of them ... like cigarettes in a pack--Heh! here is one lone devil _inside_ a lung cell ... I wonder ... have I found him--that tubercle bug, already?” Koch went on, precisely, with that efficiency of his, to staining tubercles from every part of the workman’s body, and everywhere his blue dye showed up these same slender crooked bacilli--strange creatures unlike any he had seen in all the thousands of animals or men, diseased or healthy, into whose insides he had pried. And now, sorry things began to happen to his inoculated guinea-pigs and rabbits. The guinea-pigs began to huddle disconsolately in the corners of their cages; their sleek coats ruffled and their bouncing little bodies began to fall away until they were sad bags of bones. They were feverish, their cavortings stopped and they looked listlessly at their fine carrots and their fragrant meals of hay--and one by one they died. And as these unconscious martyrs died--for Koch’s mad curiosity and for suffering men--the little microbe hunter pinned them down on his post-mortem board and soaked their sick hair with bichloride of mercury and precisely and with breathless care cut them open with sterile knives. And inside these poor beasts Koch found the same kind of grayish-yellow sinister tubercles that had filled the body of the workman. Into the baths of blue stain on his eternal strips of glass Koch dipped them--and everywhere, in every one, he found the same terrible curved sticks that had jumped into his astounded gaze when he had stained the lung of the dead man.