"Liver," says Moeller. "Mixed with some other viscera. The first part that a wild animal usually eats in its kill is the liver and stomach, the GI tract." Organs in general are among the most nutritionally giving foods on Earth. A serving of lamb spleen has almost as much vitamin C as a tangerine. Beef lung has 50 percent more. Stomachs are especially valuable because of what's inside them. The predator benefits from the nutrients of the plants and grains in the guts of its prey. "Animals have evolved to survive," Rawson says. They like what's best for them. People blanch to see "fish meal" or "meat meal" on a pet-food ingredient panel, but meal--which variously includes organs, heads, skin, and bones--most closely resembles the diet of dogs and cats in the wild. Muscle meat is a grand source of protein, but comparatively little else. Animals"