He lived among scientific books and subscribed to every chemical journal in every language he could read, and in several he couldn’t read. Books littered his laboratory so that when visitors came and Ehrlich said: “I beg you, be seated!” there was no place for them to sit at all. Journals stuck out of the pockets of his overcoat--when he remembered to wear one--and the maid, bringing his coffee in the morning, fell over ever-growing mountains of books in his bedroom. Books, with the help of those expensive cigars, kept Paul Ehrlich poor. Mice built nests in the vast piles of books on the old sofa in his office. When he wasn’t painting the insides of his animals and the outside of himself with his dyes, he was peering in these books. And what was important inside of those books, was in the brain of Paul Ehrlich, ripening, changing itself into those outlandish ideas of his, waiting to be used. That was where Paul Ehrlich got his ideas--you would never accuse him of stealing the ideas of others!--and queer things happened to those ideas of others when they stewed in Ehrlich’s brain. So now, in 1901, at the beginning of his eight-year search for the magic bullet he read of the researches of Alphonse Laveran. Laveran was the man, you remember, who discovered the malaria microbe, and very lately Laveran had taken to fussing with trypanosomes. He had shot those finned devils, which do evil things to the hind-quarters of horses and give them a disease called the mal de Caderas, into mice. Laveran had watched those trypanosomes kill those mice, one hundred times out of one hundred. Then Laveran had injected arsenic under the skins of some of those suffering mice. That had helped them a little, and killed many of the trypanosomes that gnawed at them, but not one of these mice ever got really better; one hundred out of one hundred died and that was as far as Alphonse Laveran ever got. But reading this was enough to get Ehrlich started. “Ho! here is an excellent microbe to work with! It is large and easy to see. It is easy to grow in mice. It kills them with the most beautiful regularity! It _always_ kills mice! What could be a better microbe than this trypanosome to use to try to find a magic bullet to cure? Because, if I could find a dye that would save, completely save, just one mouse!” IV