(18.) _Distinctions between the Sheep and Goat._--Though a comparison of the most common domesticated breeds of sheep and goats, tends to confirm the broad distinctions drawn between them, yet these differences almost entirely disappear, when we attempt to define the characteristics of those races, which still exist in a wild state in various parts of both Continents, where it is so far impossible to determine the precise division to which they belong, that Cuvier holds them unworthy of a generic separation. Sheep and goats, in fact, agree in so many points as regards structure, form, stature, and habit, that were it not that sheep, according to that naturalist, have "their horns directed backwards, returning more or less forwards in a spiral manner, with a generally convex line of profile, and no beard," while the goats have "their horns directed upwards and backwards, their chins generally decorated with a long beard, and their line of profile almost always concave," there would hardly exist a difference worth the noting. Some writers place great reliance on the differences indicated by the different coverings of the animals, ascribing wool to the sheep, and hair to the goat, forgetting that most of the wild sheep, and some of the domesticated races, are covered with hair, while some goats, as those of Thibet and Angora, are remarkable for the fineness of their wool. Even supposing these distinctions to hold good, we have still to combat the fact, that _sheep and goats produce mongrels capable of reproduction_, a consideration sufficient of itself to prove, that the sheep and goat can never be made to form the types of separate genera.[2] [2] For further information on this subject, see that excellent paper on the Natural History of the Sheep and Goat, by James Wilson, Esq. in No. IX. of the Quarterly Journal of Agriculture. (19.) _Horns of Sheep._--As the Chevrotains or Musks are distinguished, with the Camels, from other animals of this order by the absence of horns, so are sheep, oxen, goats, and antelopes, distinguished from the rest of the horned genera of the order, by the persistence of their frontal prolongations. The horn is an elastic sheath of _agglutinated hairs_, which appears within the first twelve months, though sometimes present at birth, and increases by layers, one being added every year, so that the age of a ram may be known by the number of rings. The ewes have commonly no horns, but only a protuberance in place of them. The horn is supported by, and serves to cover, a highly vascular prolongation of the frontal bone, and it is at its root, where large vessels, and nervous filaments are entering, that blows occasion so great agony to the animal, apart from the damage which the other bones sustain by the infliction of violence on so powerful a level.