In snails the horns are fleshy, and are thus adapted for the purpose of feeling the way, which is also the case with the cerastes;[175] some reptiles, again, have only one horn, though the snail has always two, suited for protruding and withdrawing. The barbarous nations of the north drink from the horns of the urus,[176] a pair of which will hold a couple of urnæ:[177] other tribes, again, point their spears with them. With us they are cut into laminæ, upon which they become transparent; indeed, the rays of a light placed within them may be seen to a much greater distance than without. They are used also for various appliances of luxury, either coloured or varnished, or else for those kinds of paintings which are known as “cestrota,”[178] or horn-pictures. The horns of all animals are hollow within, it being only at the tip that they are solid: the only exception is the stag, the horn of which is solid throughout, and is cast every year. When the hoofs of oxen are worn to the quick, the husbandmen have a method of curing them, by anointing the horns of the animal with grease. The substance of the horns is so ductile, that even while upon the body of the living animal, they can be bent by being steeped in boiling wax, and if they are split down when they are first shooting, they may be twisted different ways, and so appear to be four in number upon one head. In females the horns are generally thinner than in the males, as is the case, also, with most kinds of wool-bearing animals. No individuals, however, among sheep, or hinds, nor yet any that have the feet divided into toes, or that have solid hoofs, are furnished with horns; with the sole exception of the Indian ass,[179] which is armed with a single horn. To the beasts that are cloven-footed Nature has granted two horns, but to those that have fore-teeth in the upper jaw, she has given none. Those persons who entertain the notion that the substance of these teeth is expended in the formation of the horns, are easily to be refuted, if we only consider the case of the hind, which has no more teeth than the male, and yet is without horns altogether. In the stag the horn is only imbedded in the skin, but in the other[180] animals it adheres to the bone. CHAP. 46.—THE HEADS OF ANIMALS. THOSE WHICH HAVE NONE. The head of the fish is very large in proportion to the rest of the body, probably, to facilitate its diving under water. Animals of the oyster and the sponge kind have no head, which is the case, also, with most of the other kinds, whose only sense is that of touch. Some, again, have the head blended with the body, the crab, for instance. CHAP. 47.—THE HAIR.