The teeth are all made for snatching and tearing, but not for masticating, the Crocodile swallowing its prey entire when possible; and when the animal is too large to be eaten entire, the reptile tears it to pieces, and swallows the fragments without attempting to masticate them. In order to enable it to open its mouth under water, the back of its throat is furnished with a very simple but beautiful contrivance, whereby the water is received on a membranous valve and, in proportion to its pressure, closes the orifice of the throat. As the Crocodiles mostly seize their prey in their open jaws and hold it under water until drowned, it is evident that without such a structure as has been described the Crocodile would be as likely to drown itself as its prey. But the throat-valve enables it to keep its mouth open while the water is effectually prevented from running down its throat, and the nostrils, placed at the end of the snout, enable it to breathe at its ease, while the unfortunate animal which it has captured is being drowned beneath the surface of the water. This position of the nostrils serves another purpose, and enables the Crocodile to breathe while the whole of its body is under the water, and only an inch or two of the very end of the snout is above the surface. As, moreover, the Crocodile, as is the case with most reptiles, is able to exist for a considerable time without breathing, it only needs to protrude its nostrils for a few moments, and can then sink entirely beneath the water. In this way the reptile is able to conceal itself in case it should suspect danger; and as, in such instances, it dives under the herbage of the river, and merely thrusts its nose into the air among the reeds and rushes, it is evident that, in spite of its enormous size, it baffles the observation of almost every foe. Among reptiles, the mailed Crocodiles may be mentioned as most formidable foes to man. Vast in bulk, yet grovelling with the belly on the earth; clad in bony plates with sharp ridges; green eyes with a peculiar fiery stare, gleaming out from below projecting orbits; lips altogether wanting, displaying the long rows of interlocking teeth even when the mouth is closed, so that, even when quiet, the monster seems to be grinning with rage,--it is no wonder that the Crocodile should be, in all the countries which it inhabits, viewed with dread.