Alternate layers of bread and cheese in well buttered 9 inch square baking dish. Begin with bread and end with cheese. Sprinkle tuna over all. In small saucepan, cook onion and celery in butter until vegetables are tender. Remove from heat. Blend with milk, eggs and salt. Pour mixture over tuna in baking dish. Bake at 350 until puffy and lightly browned. Makes 4-6 servings.