But alas! What is the chemistry of what this subtle 606 does to the still more subtle--and unknown--machine that is the human body? Nothing is known about it even now. Paul Ehrlich paid the penalty for his fault--which may be forgiven him seeing the blessings he has brought to men--his fault of not foreseeing that once in every so many thousands of bodies a magic bullet may shoot two ways. But then, the microbe hunters of the great line have always been gamblers: let us think of the good brave adventurer Paul Ehrlich was and the thousands he has saved. Let us remember him, trail-breaker who turned a corner for microbe hunters and started them looking for magic bullets. Already (though it is too soon to tell the whole story) certain obscure searchers, some of them old slaves of Paul Ehrlich, sweating in the great dye factories of Elberfeld, have hit upon a most fantastical drug. Its chemistry is kept a secret. It is called “Bayer 205.” It is a mild mysterious powder that cures the hitherto always fatal sleeping sickness of Rhodesia and Nyassaland. That was the ill, you remember, that the hard man, David Bruce, fought his last fight, in vain, to prevent. It does outlandish things to the cells and fluids of the human body--you would say they were fibs and fairy tales if you heard the queer things that drug can do! But what is best, it slaughters microbes! It kills them beautifully, precisely, with a completeness that must make Paul Ehrlich wriggle in his grave--and when it doesn’t kill microbes it _tames_ them. It is as sure as the sun following the dawn of to-morrow that there will be other microbe hunters to mold other magic bullets, surer, safer, bullets to wipe out for always the most malignant microbes of which this history has told. Let us remember Paul Ehrlich, who broke this trail.... This plain history would not be complete if I were not to make a confession, and that is this: that I love these microbe hunters, from old Antony Leeuwenhoek to Paul Ehrlich. Not especially for the discoveries they have made nor for the boons they have brought mankind. No. I love them for the men they are. I say they _are_, for in my memory every man jack of them lives and will survive until this brain must stop remembering. So I love Paul Ehrlich--he was a gay man who carried his medals about with him all mixed up in a box never knowing which ones to wear on what night. He was an impulsive man who has, on occasion, run out of his bedroom in his shirt tail to greet a fellow microbe hunter who came to call him out for an evening of wassail. And he was an owlish man! “You say a great work of the mind, a wonderful scientific achievement?” he repeated after a worshiper who told him that was what the discovery of 606 was. “My dear colleague,” said Paul Ehrlich, “for seven years of misfortune I had one moment of good luck!” END OF MICROBE HUNTERS INDEX