This he was satisfied was among the most virulent of substances known to toxicology.  A puncture of the skin was sure to be fatal unless some remedy, of whose existence he held no suspicion, was instantly obtainable.

He had set down his rifle white examining the weapon, but quickly caught it up again, still retaining the javelin in his right band.  He had been startled by the sound of the terrific threshing among the trees on his right.

He supposed that his friend was coming back, but, glancing toward the point where he expected him to appear, he was amazed to see the third native, who whisked off before Long could draw a bead on him, step from the wood not twenty paces away.  His back was toward the Professor, and, strangely enough, he did not observe the white man—­an oversight that never could have occurred, but for the tumult in the undergrowth which held his attention.

Grimcke had hardly caught sight of him, when the other native came flying to view, so astonishing his waiting comrade that he stood a moment irresolute after the white pursuer burst into sight.

Brief as was this pause, it gave the Professor time for some exceedingly fine work.  He uttered a shout which caused the native to turn his affrighted gaze behind him, just in time to observe the white man with javelin raised and apparently in the very act of launching it at him.

The savage knew what a prick from that frightful thing meant, and with a howling shriek he ducked his head as though he had caught its whizz through the air, and shot among the trees with as much celerity as his companion had shown in coming from them.

Neither of the explorers wished to slay the natives, no matter how savage, unless compelled to do so in actual self-defence.  Long had recovered from his first burst of fury, and, though the Professor could have sunk the javelin in the naked body, he withheld it, not unwilling that his assailant, now that he had started to flee, should escape.

The one who had so foolishly come back to the river side was left in the worst possible situation, for both his enemies stood between him and the sheltering forest and he was defenceless.  He was at their mercy, and such people as those natives neither gave nor expected quarter, when engaged in their savage warfare.

The fellow acted like a bewildered animal.  The white strangers were standing a few paces apart, so as to form the two angles of a triangle, while he made the third.  The nearest point to the forest way midway between Grimcke and Long, as was apparent to the savage, who was fairly cornered.

Had the Xingu behind him been as placid as farther above or below the rapids, he would not have hesitated to plunge into its waters, trusting to his skill in swimming; but, to dive into the raging current would have been as certain destruction as for a man to undertake to swim unaided through the whirlpool below Niagara.