Bruce and Mrs. Bruce came at last to Ubombo--it was a settlement on a high hill, looking east toward the Indian Ocean across sixty miles of plain, and the olive-green of the mimosa thickets of this plain was slashed with the vivid green of glades of grass. On the hill they set up their laboratory; it consisted of a couple of microscopes, a few glass slides, some knives and syringes and perhaps a few dozen test-tubes--smart young medical students of to-day would stick up their noses at such a kindergarten affair! Here they set to work, with sick horses and cattle brought up from the plain below--for Providence had so arranged it that beasts could live on the barren hill of Ubombo, absolutely safe from nagana, but just let a farmer lead them down into the juicy grass of that fertile plain, and the chances were ten to one they would die of nagana before they became fat on the grass. Bruce shaved the ears of the horses and jabbed them with a scalpel, a drop of blood welled out and Mrs. Bruce, dodging their kicks, touched off the drops onto thin glass slides. It was hot. Their sweat dimmed the lenses of their microscopes; they rejoiced in necks cramped from hours of looking; they joked about their red-rimmed eyes. They gave strange nicknames to their sick cows and horses, they learned to talk some Zulu. It was as if there were no Directors-General or superior officers in existence, and Bruce felt himself for the first time a free searcher. And very soon they made their first step ahead: in the blood of one of their horses, sick to death, Bruce spied a violent unwonted dancing among the faintly yellow, piled-up blood corpuscles; he slid his slide along the stage of his microscope, till he came to an open space in the jungle of blood cells.... [Illustration: (line drawing of trypanosomes)] There, suddenly, popped into view the cause of the commotion--a curious little beast (much bigger than any ordinary microbe though), a creature with a blunt rear-end and a long slim lashing whip with which he seemed to explore in front of him. A creature shaped like a panatella cigar, only it was flexible, almost tying itself in knots sometimes, and it had a transparent graceful fin running the length of its body. Another of the beasts swam into the open space under the lens, and another. What extraordinary creatures! They didn’t go stupidly along like common microbes--they acted like intelligent little dragons. Each one of them darted from one round red blood cell to another; he would worry at it, try to get inside it, tug at it and pull it, push it along ahead of him--then suddenly off he would go in a straight line and bury himself under a mass of the blood cells lining the shore of the open space....