If Hunter had carried this reasoning a little further, he might have asked,--Why should there not be a Free Martin, or hermaphrodite, produced in the case of twins, when they are both apparently males, or both apparently females? Had he done this, he would not, probably, have made the following observation: "I need hardly observe, that if a cow has twins, and they are both bull-calves, they are in every respect perfect bulls; or if they are both cow-calves, they are perfect cows." What is this but saying that a bull-calf is a bull-calf, and a cow-calf is a cow-calf? For a Free Martin, or hermaphrodite, is not, in any case, either a bull or a cow. There does not appear to be anything known of the peculiar circumstances under which, what is termed a Free Martin is produced. [Illustration: Skull of Domestic Ox.] The most general observation that can be made on the subject appears to be, that cows sometimes produce calves, which, by reason of their imperfectly developed generative system, are incapable of procreating. THE SHORT-NOSED OX. [Illustration: Skull of short-nosed Ox of the Pampas.] The common Ox, originally taken over to America by the early Spanish settlers, now runs wild in immense herds on the Pampas, where it is hunted and slain for its hide. Some idea may be formed of the immensity of these herds, from the circumstance that nearly a million of hides are annually exported from Buenos Ayres and Monte Video to Europe. Some of the herds in these wild regions have undergone a most singular modification of the cranium, consisting in a shortening of the nasal bones, together with the superior and inferior maxillaries. There is a skull of this variety in the Museum of the College of Surgeons, of which the above is a sketch. ON THE UTILITY OF THE OX TRIBE TO MANKIND. How eminently serviceable to man these animals are, is shown in the following table, in which are set forth the most important uses to which their various parts are applied: SKIN.--The skin has been of great use in all ages. The ancient Britons constructed their boats with osiers, and covered them with the hides of bulls; and these boats were sufficiently strong to serve for short coasting voyages. Similar vessels are still in use on the Irish lakes, and in Wales on the rivers Dee and Severn. In Ireland they are called _curach_, in England _coracles_, from the British _cwrwgl_, a word signifying a boat of that structure. Boots, shoes, harness, &c. for horses, and various kinds of travelling trunks are made from hides when tanned. The skin of the calf is extensively used in the binding of books, and the thinnest of the calf skins are manufactured into vellum. The skin of the Cape Buffalo is made into shields and targets, and is so hard that a musket ball will scarcely penetrate it.