At last he muttered: “They’re here, these sticks and threads ... they are swarming in the body of this mouse, exactly as they were in the drop of dead sheep’s blood that I dipped the little sliver in yesterday.” Delighted, Koch knew that he had caused in the mouse, so cheap to buy, so easy to handle, the sickness of sheep and cows and men. Then for a month his life became a monotony of one dead mouse after another, as, day after day, he took a drop of the blood or the spleen of one dead beast, put it carefully on a clean splinter, and slid this sliver into a cut at the root of the tail of a new healthy mouse. Each time, next morning, Koch came into his laboratory to find the new animal had died, of anthrax, and each time in the blood of the dead beast his lens showed him myriads of those sticks and tangled threads--those motionless, twenty-five-thousandth-of-an-inch thick filaments that he could never discover in the blood of any healthy animal. “These threads _must_ be alive,” Koch pondered, “the sliver that I put into the mouse has a drop of blood on it and that drop holds only a few hundreds of those sticks--and these have grown into billions in the short twenty-four hours in which the beast became sick and died.... But, confound it, I must _see_ these rods grow--and I can’t look inside a live mouse!” How--shall--I--find--a--way--to--see--the--rods--grow--out--into--threads? This question pounded at him while he counted pulses and looked at his patients’ tongues. In the evenings he hurried through supper and growled good-night to Mrs. Koch and shut himself up in his little room that smelled of mice and disinfectant, and tried to find ways to grow his threads outside a mouse’s body. At this time Koch knew little or nothing about the yeast soups and flasks of Pasteur, and the experiments he fussed with had the crude originality of the first cave man trying to make fire.