Diet for the very aged becomes mainly a question of invalid diet, and it must be remembered that much should be granted to the individual's choice and liking. All foods for the aged should be light and easily digested, and careful attention paid to proper cooking. A striking example of lost health recovered and life and activity prolonged to a great age, by strict temperance in food, is Cornaro, a Venetian nobleman of the sixteenth century, who lived over 100 years. He says:--"Our kind mother Nature, in order that old men may live to still greater age, has contrived matters so that they should be able to subsist on little, as I do, for large quantities of food cannot be digested by old and feeble stomachs. By always eating little, the stomach, not being much burdened, need not wait long to have an appetite. It is for this reason that dry bread relishes so well with me.... When one arrives at old age, he ought to divide that food of which he was accustomed to make but two meals into four, and as in his youth he made but two collations in a day, he should in his old age make four, provided he lessen the quantity as his years increase. And this is what I do, agreeably to my own experience; therefore my spirits, not oppressed by much food, but barely kept up, are always brisk, especially after eating, nor do I ever find myself the worse for writing immediately after meals, nor is my understanding ever clearer, or am I apt to be drowsy, the food I take being in too small a quantity to send up fumes to the brain. Oh, how advantageous it is for an old man to eat but little! Accordingly, I, who know it, eat but just enough to keep body and soul together." Digestion.--Digestion is the process whereby the food we eat is turned into material fit to be assimilated by the blood. It begins in the mouth by the mechanical grinding and crushing of the food, and the chemical conversion of the starchy part into sugar, in which form alone it can be assimilated. This conversion is carried out by the saliva. Hence the necessity for thorough mastication, even of sloppy foods that do not seem to require it, and for attention to the teeth in order that they may thoroughly chew. Alcohol and tobacco, as they spoil the saliva, are very unfavourable to digestion, and should always be avoided. Twenty minutes longer to chew one's dinner is worth a whole box of pills, and no one need expect good digestion who neglects thorough chewing and salivation of the food. This may, with advantage, be increased to an extent which most people would think quite absurd. It has been proved that when all food is chewed until completely reduced to a liquid, its nutritive qualities are so increased that about half as much will suffice. This is of immense importance in all cases of weak digestion, or indeed whenever an absence of vigorous health renders the economy of vital energy important. [Illustration: Digestive System.]