28. Nutrients. A large part of the grain consumed in burning, consists of nutrients, i. e., nutritious substances, which form the main bulk. Besides this there is a small amount of woody material (non-nutrient) contained chiefly in the hull. When this indigestible covering is removed in the process of milling, the meal or flour which is left, represents therefore the nutritive part of the grain free from nearly all that is useless for food. Plainly, then, it is upon the composition of this inner part that the value of the grain must principally depend; and here, as we shall see, the most important differences are to be found.