Like the crocodile, but smaller even than the ichneumon, is the scincus, which is also produced in the Nile, and the flesh of which is the most effectual antidote against poisons. But so great a pest was the crocodile to prove, that Nature was not content with giving it one enemy only; the dolphins, therefore, which enter the Nile, have the back armed with a spine,[101] which is edged like a knife, as if for this very purpose; and although these animals are much inferior in strength, they contrive to destroy the crocodile by artifice, which on the other hand attempts to drive them from their prey, and would reign alone in its river as its peculiar domain. For all animals have an especial instinct in this respect, and are able to know not only what is for their own advantage, but also what is to the disadvantage of their enemies; they fully understand the use of their own weapons, they know their opportunity, and the weak parts of those with which they have to contend. The skin of the belly of the crocodile is soft and thin; aware of this, the dolphins plunge into the water, as if in great alarm, and diving beneath its belly, tear it open with their spines. There is a race of men also, who are peculiarly hostile to the crocodile; they are known as the Tentyritæ, from an island in the Nile which they inhabit. These men are of small stature, but of wonderful presence of mind, though for this particular object only. The crocodile is a terrible animal to those who fly from it, while at the same time it will fly from those who pursue it; these, however, are the only people who dare to attack it. They even swim in the river after it, and mount its back like so many horsemen; and just as the animal turns up its head for the purpose of biting them, they insert a club into its mouth, holding which at each end, with the two hands, it acts like a bit, and by these means they drive the captured animal on shore. They also terrify the crocodile so much even by their voice alone, as to force it to disgorge the bodies which it has lately swallowed, for the purpose of burial. This island, therefore, is the only place near which the crocodile never swims; for it is repelled by the odor of this race of men. The sight of the animal is said to be dull when it is in the water, but, when out of the water, piercing in the extreme; it always passes the four winter months in a cave, without taking food. Some persons say, that this is the only animal that continues to increase in size as long as it lives; it is very long-lived.