The horns, then, are but an excrescence, a part foreign to the body of the stag, and only esteemed as an animal substance because it grows from him; it is in reality a vegetable production, since it retains all the marks of that vegetable from which it derives its origin, and resembles the branch of a tree in the manner it grows, expands, hardens, dries, and separates; for it falls off spontaneously, after having acquired its full degree of solidity, like a ripe fruit from the branch. The very name given to this production in the French language[E] is a proof that it has been considered as a species of wood, and not as a horn, a bone, a tusk, a tooth, &c. In addition to these arguments, we may add a fact recorded by Aristotle, Theophrastus, and Pliny, who all assert that ivy has been seen to grow round the horns of stags while they were in a tender state. If this be true and it would be easy to make the experiment, it would still more fully establish the analogy between the wood of the stag and that of trees. The horns and tusks of other animals are not only of a substance different from the branches of a stag, but also in their growth, texture, and form, both exterior and interior, there is nothing which bears any analogy to wood: these and the nails, claws, hair, feathers, scales, &c. grow, it is true, by a kind of vegetation, but a vegetation widely different from that of trees. The horns of oxen, goats, antelopes, &c. are hollow within, whereas those of the stag are entirely solid; the substance of the former is the same with that of nails, claws, scales, &c. but the horns of the stag resemble wood more than any other substance. All these hollow horns are covered on the inside by a _periosteum_, and contain in their cavities a bone which serves to support them; they never fall off but continue to increase during the life of the animal, and will assist in determining its age, by the number of annual rings. Instead of growing like those of the stag, from the upper extremity, they grow like nails, feathers, and hair from the lower extremity. Thus it is also with the tusks of the elephant, sea-cow, boar, and all other animals; they are hollow within, and grow only from the lower extremity. These horns or tusks have therefore no more resemblance than nails, hairs, or feathers, to the horns of the stag. [E] The French word is _bois_, a forest, a wood, likewise used for the substance, or branch of a tree