Nearly a year had been wasted. But who can blame those natural enemies of David Bruce, the High Authorities, for keeping him from research? They looked at him; they secretly trembled at his burliness and his mustaches and his air of the Berserker. This fellow was born for a soldier! But they were so busy, or forgot, and presently Hely-Hutchinson did his dirty work again, and in September, 1895, Bruce and his wife got back to Ubombo, to try to untangle the knot of how nagana gets from a sick animal to a healthy one. And here Bruce followed, for the first time, Theobald Smith around that corner.... Like Theobald Smith, Bruce was a man to respect and to test folk-hunches and superstitions. He respected the beliefs of folks, himself he had no fancy super-scientific thoughts and never talked big words--yes, he respected such hunches--but he must test them! “It is the tsetse flies cause nagana,” said some experienced Europeans. “Flies bite domestic animals and put some kind of poison in them.” “Nagana is caused by big game,” said the wise Zulu chiefs and medicine men. “The discharges of the buffalo, the quagga, and waterbuck, the koodoo--these contaminate the grass and the watering places--so it is horses and cattle are hit by the nagana.” “But why do we always fail to get our horses safe through the fly country--why is nagana called the fly disease?” asked the Europeans. “Why, it’s easy to get animals through the fly belt so long as you don’t let them eat or drink!” answered the Zulus. Bruce listened, and then proceeded to try out both ideas. He took good healthy horses, and tied heavy canvas bags round their noses so they couldn’t eat nor drink; he led them down the hill to the pleasant-looking midday hell in the mimosa thickets; here he kept them for hours. While he watched to see they didn’t slip their nose bags, swarms of pretty brown and gold tsetses buzzed around them--flopped on to the kicking horses and in twenty seconds swelled themselves up into bright balloons of blood.... The world seemed made of tsetse flies, and Bruce waved his arms. “They were enough to drive one mad!” he told me, thirty years afterward I can see him, talking to those pests in the language of a dock-foreman, to the wonder of his Zulus. Day after day this procession of Bruce, the Zulus, and the experimental horses went down into the thorns, and each afternoon, as the sun went down behind Ubombo, Bruce and his migrating experiment grunted and sweated back up the hill. Then, in a little more than fifteen days, to the delight of Bruce and his wife, the first of those horses who had served as a fly-restaurant turned up seedy in the morning and hung his head. And in the blood of this horse appeared the vanguard of the microscopic army of finned wee devils--that tussled so intelligently with the red blood cells....