“But where do the tsetses of the plain _get_ the trypanosomes they stick into cows and horses? In those fly belts there are often no horses or cattle sick with nagana, for months. Surely the flies [he was wrong here] can’t stay infected for months--it must be they get them from the wild animals, the big game!” That was a possibility after his heart. Here was a chance to do something else than sit at a microscope. He forgot instantly about the more patient, subtle jobs that demanded to be done--teasing jobs, for a little man, jobs like tracing the life of the trypanosomes in the flies.... “The microbes must be in game!” and he buckled on his cartridge belt and loaded his guns. Into the thickets he went, and shot Burchell’s zebras; he brought down koodoos and slaughtered water-bucks. He slashed open the dead beasts and from their hot hearts sucked up syringes full of blood, and jogged back up the hill with them. He looked through his microscopes for trypanosomes in these bloods--but didn’t find them. But there was a streak of the dreamer in him. “They may be there, too few to see,” he muttered, and to prove they were there he shot great quantities of the blood from ten different animals into healthy dogs. So he discovered that the nagana microbes may lurk in game, waiting to be carried to gentler beasts by the tsetse. So it was Bruce made the first step towards the opening up of Africa. IV And Hely-Hutchinson saw how right he had been about David Bruce. “’Ware the tsetse fly,” he told his farmers, “kill the tsetse fly, clear the thickets in which it likes to breed--drive out, exterminate the antelope from which it sucks the trypanosomes.” So Bruce began ridding Africa of nagana.