Next in importance to horse hides is the pig skin, which produces a wonderfully tough leather. The pig skin leather industry is chiefly confined to Scotland and Germany, the reason being that the skins are left on the carcases in the other parts of the world. On the average, a pig skin is worth about 6s., yet it is seldom removed from the carcase. One reason is the great difficulty of flaying the animal; it appears to be almost impossible by present methods to remove the skin without cutting away a large quantity of fat, and the value of the skin compared to the loss of weight of the meat offers very little inducement to remove the skin, in addition to which, the custom of leaving the rind on bacon and pork effectually prevents any attempt at present to increase the supply of pig skins. This is a great loss to the leather trade, for the pig skin is particularly suitable for saddles and various kinds of strong leather goods. Imitation pig-skin leather is made from hides, shoulders, bellies, or persians, but real pig skin is distinguished from the imitation by its peculiarly marked grain, formed of groups of three small holes which penetrate well into the skin and form part of the sheaths of the pig's bristles. Among other skins useful for leather are those of the wallaby, kangaroo, dog, lizard, crocodile, alligator, ichneumon, frog (Japanese), deer, antelope, and chamois, while it is said that even rabbit skins have been pressed into service in Germany, though they cannot have much value owing to their small size and thin substance. Dog-skin leather wears well, mainly on account of the large amount of natural grease present in the skin, but the supplies are naturally small. The hides of the walrus, elephant, rhinoceros, hippopotamus, and other wild animals are also tanned in small quantities, walrus leather being well adapted for knife and sword polishing. The mammals also contribute their quota to the supply of raw material of the leather trade, the seal perhaps, being the most important. This refers to the hairy seal hunted off the North American coast. The raw skins are shipped chiefly from Newfoundland, where the industry of seal fishing is well organised and provides employment for about 6,000 men. The seal caught in the North Atlantic Ocean is hairy and quite distinct from the fur seal captured in the Arctic Ocean off Alaska. The skin of the hair seal is only suitable for making into leather, but there is a layer of fat underneath it which furnishes a valuable raw material for the manufacture of oils and soap. The skins are salted and shipped to America and England. They are easily distinguished from other kinds of commercial hides and skins by the oily appearance of the flesh side.