Usually cooks don’t welcome large amounts of toughening connective tissue in meat. But taken on their own, animal skin, cartilage, and bones are valuable exactly because they’re mostly connective tissue and therefore full of collagen (skin also provides flavorful fat). Connective tissue has two uses. First, in long-cooked stocks, soups, and stews, it dissolves out of bones or skin to provide large quantities of gelatin and a substantial body. And second, it can be turned into a delicious dish itself, with either a succulent gelatinous texture or a crisp, crunchy one, depending on the cut and the cooking method. Long moist cooking gives tender veal ears, cheeks, and muzzle for tête de veau, or Chinese beef tendon or fatty pork skin. A briefer cooking produces crunchy or chewy cartilaginous pig’s ears, snouts, and tails; and rapid frying gives crisp pork rinds.