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 tiny particle of the demolished larva, oft-times not more than a speck of moisture.

Again, a minute bit of bark has been upturned by the scraping hand, and the direction of the break indicates the direction of the passage. Or some great limb, or the stem of the tree itself has been brushed by the hairy body, and a tiny shred of hair tells him by the direction from which it is wedged beneath the bark that he is on the right trail.

Nor does he need to check his speed to catch these seemingly faint records of the fleeing beast.

To Tarzan they stand out boldly against all the myriad other scars and bruises and signs upon the leafy way. But strongest of all is the scent, for Tarzan is pursuing up the wind, and his trained nostrils are as sensitive as a hound's.

There are those who believe that the lower orders are specially endowed by nature with better olfactory nerves than man, but it is merely a matter of development.

Man's survival does not hinge so greatly upon the perfection of his senses. His power to reason has relieved them of many of their duties, and so they have, to some extent, atrophied, as have the muscles which move the ears and scalp, merely from disuse.

The muscles are there, about your ears and beneath your scalp, and so are the nerves which transmit sensations to your brain, but they are [254]