Nature's Logic Beef And Beef Lung: an all-natural, USDA Prime Midwest beef treat, great for recreational chewing and dental hygiene -- made without chemically synthesized vitamins, minerals, or trace nutrients. Nature's Logic Beef And Beef Lung: an all-natural, USDA Prime Midwest beef treat, great for recreational chewing and dental hygiene -- made without chemically synthesized vitamins, minerals, or trace nutrients. Natlog treat for dogs. Treat type: Chews. Available flavors: Beef Lung. Available sizes: 1lb.