A bellow from Bruce: “I’ve got one!” The rest crowd round, squint in turn, exclaim as they watch the writhing trypanosome poke his exploring whip about in the gray field of the lens. Then they go back to their places--to shout discovery in their turn. So it went, from breakfast till the swift dusk of evening. In every single sample of spinal fluid from each one of his more than forty sleeping-sickness patients, Bruce and his companions found those trypanosomes. “But they may be in healthy people’s spines too!” said Bruce. Bruce knew that if he found them in healthy negroes, all this excitement would be only a wild-goose chase--he must prove they were to be found only in folks with sleeping sickness. But to get fluid out of healthy people’s spines? Folks dopey from the sleeping death didn’t mind it so much--but to jab one of those big needles into the back of healthy wide-awake colored people, who had no wish to be martyrs to science.... Can you blame them? It is no picnic having such a spear stuck into your spine. Then Bruce hit on a crafty scheme. He went to the hospital, where there was a fine array of patients with all kinds of diseases--but no sleeping sickness--and then, flimflamming them into thinking the operation would do them good, this liar in the holy cause of microbe hunting jabbed his needles into the smalls of the backs of negroes with broken legs and with headaches, into youngsters who had just been circumcised, and into their brothers or sisters who were suffering from yaws, or the itch; from all of them he got spinal fluid. And it was a great success. Not one of these folks--who had no sleeping sickness--harbored a single trypanosome in the fluid of their spines. Maybe the operation did do them some good--but no matter, they had served their purpose. The trypanosome, Castellani and Bruce now knew, was the cause of sleeping sickness! Now--and this is rare in the dreamers who find fundamental facts in science--Bruce was a fiend for practical applications, not poetically like Pasteur, for Bruce wasn’t given to such lofty soarings, nor was he practical in the dangerous manner of the strange genius I tell of in the last chapter of this story; but the moment he turned to the study of a new plague, Bruce’s gray eyes would dart round, he would begin asking himself questions: What is the natural home of the virus of this disease?--How does it get from sick to healthy?--What is its fountain and origin?--Is there anything _peculiar_ in the way this sleeping sickness has spread? That was the way he went at it now. He had discovered the trypanosome that was the cause. There were a thousand pretty little researches to tempt the scholar in him, but he brushed all these aside. Old crafty hand at searching that he was, he fished round in his memories, and came to nagana, and screwed up his eyes: “Is there anything peculiar about the way sleeping sickness is _located_ in this country?” He pondered.