All birds, however, have not eyelids: hence it is, that those which are viviparous have no nictation of the eye. The heavier kinds of birds shut the eye by means of the lower eyelid, and they wink by drawing forward a membrane which lies in the corner of the eye. Pigeons, and other birds of a similar nature, shut the two eyelids; but the quadrupeds which are oviparous, such, for instance, as the tortoise and the crocodile, have only the lower eyelid moveable, and never wink, in consequence of the hardness of the eye. The edge of the upper eyelid was by the ancients called “cilium,” from which comes our word “supercilia.[211]” If the eyelid happens to be severed by a wound it will not reunite,[212] which is the case also with some few other parts of the human body. CHAP. 58.—THE CHEEKS. Below the eyes are the cheeks, a feature which is found in man only. From the ancients they received the name of “genæ,” and by the laws of the Twelve Tables, women were forbidden to tear them.[213] The cheeks are the seat of bashfulness; it is on them more particularly that blushes are to be seen. CHAP. 59.—THE NOSTRILS. Within the cheeks is the mouth, which gives such strong indications of the feelings of joyousness and laughter; and above it, but in man only, is the nose, which modern notions have stamped as the exponent of sarcasm and ridicule.[214] In no other animal but man, is the nose thus prominent; birds, serpents, and fishes, have no nostrils, but apertures only for the purpose of smell. It is from the peculiarity of the nose that are derived the surnames of “Simus”[215] and “Silo.” Children born in the seventh month often have the ears and the nostrils imperforate. CHAP. 60.—THE MOUTH; THE LIPS; THE CHIN; AND THE JAW-BONE. It is from the “labia,” or lips, that the Brocchi[216] have received the surname of Labeo. All animals that are viviparous have a mouth that is either well-formed, or harshly defined, as the case may be. Instead of lips and mouth, the birds have a beak that is horny and sharp at the end. With birds that live by rapine, the beak is hooked inwards, but with those which gather and peck only, it is straight: those animals, again, which root up grass or puddle in the mud, have the muzzle broad, like swine. The beasts of burden employ the mouth in place of hands in gathering their food, while those which live by rapine and slaughter have it wider than the rest. No animal, with the exception of man, has either chin or cheek-bones. The crocodile is the only animal that has the upper jaw-bone[217] moveable; among the land quadrupeds it is the same as with other animals, except that they can move it obliquely. CHAP. 61.—THE TEETH; THE VARIOUS KINDS OF TEETH; IN WHAT ANIMALS THEY ARE NOT ON BOTH SIDES OF THE MOUTH: ANIMALS WHICH HAVE HOLLOW TEETH.