Prized by gourmets throughout the world, sweetbreads are the thymus glands of veal, young beef, lamb and pork. There are two glands — an elongated lobe in the throat and a larger, rounder gland near the heart. These glands are connected by a tube, which is often removed before sweetbreads are marketed. The heart sweetbread is considered the more delectable (and is therefore more expensive) of the two because of its delicate flavor and firmer, creamy-smooth texture. Sweetbreads from milk-fed veal or young calves are considered the best. Those from young lamb are quite good, but beef sweetbreads are tougher and pork sweetbreads (unless from a piglet) have a rather strong flavor. Veal, young calf and beef sweetbreads are available year-round in specialty meat markets, whereas those from lamb and pork must usually be special-ordered. Choose sweetbreads that are white (they become redder as the animal ages), plump and firm. They're very perishable and should be prepared within 24 hours of purchase. Before being cooked, sweetbreads must be soaked in several changes of acidulated water and their outer membrane removed. Some recipes call for the glands to be blanched to firm them, and refrigerated until ready for use. Sweetbreads can be prepared in a variety of ways including poaching, sautéing and braising. They are also sometimes used in pâtéS and souffléS.