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death; a second had no definite opinion that I know of; the third, Castellani, thought at first that the wee villain back of the sleeping death was a streptococcus—like the microbe that causes sore throats.

That was way off the truth, but Castellani had the merit of working with his hands, trying this, trying that, devising ingenious ways of looking at the juices of those darkies. And so one day—by one of those unpredictable stumbles that lie at the bottom of so many discoveries—Castellani happened on one of those nasty little old friends of David Bruce, a trypanosome. From inside the backbone of a deadly drowsy black man Castellani had got fluid—to look for streptococcus. He put that fluid into a centrifuge—that works like a cream separator—to try to whirl possible microbes down to the bottom of the tube in the hope to find streptococcus. Down the barrel of his microscope Castellani squinted at a drop of the gray stuff from the bottom of the fluid and saw—

A trypanosome, and this beast was very much the same type of wiggler David Bruce had fished out of the blood of horses dying of nagana. Castellani kept squinting, found more trypanosomes, in the spinal juices and even in the blood of a half a dozen doomed darkies. . . .

That was the beginning, for if Castellani had not seen them, told Bruce about them, they might never have been found.

Meanwhile the smolder of the sleeping death broke into a flare that threatened English power in Africa. And the Royal Society sent the veteran David Bruce down there, with the trained searcher Nabarro, with Staff-Sergeant Gibbons, who could do anything from building roads to fixing a microscope. Then of course Mrs. Bruce was along; she had the title of Assistant—but Bruce paid her fare.

They came down to Uganda, met Castellani. He told Bruce about the streptococcus—and the trypanosomes. Back to the laboratory went these two; microscopes were unpacked, set up; doomed darkies carried in. Heavy needles were jabbed