Diet for the Lean.--To a large extent the preceding article will suggest what is suitable here, remembering, however, that regular exercise will be also necessary in order to enable the muscles to increase in size. Green vegetables and fruits should be largely used in addition to the carbonaceous foods, as their FOOD SALTS (_see_) are necessary to keep the blood in a condition to allow of proper assimilation. In the case of nervous and consumptive patients, the more digestible forms of fat, such as cream and butter, are to be recommended. Some thin people do not seem able to assimilate much fat. These cases will do better on a smaller quantity. Remember always that it is not what is eaten, but what is assimilated, that goes to increase the weight, therefore if any particular food is found, after a careful trial, to constantly disagree, it must be accepted that for that one at all events, it is not a suitable article of diet. Diet for Middle Age and the Aged.--In advancing years when less exercise is, as a rule, taken, a restriction in the amount of food consumed is highly desirable. The increasing corpulence, which often begins to show itself from 30 to 40, is far from being a healthy sign; indeed, is often the premonitory symptom of serious disease. It should be remembered that a lessening quantity of food is required from middle life on. This applies to all the elements of food. It is noticeable that a fat person seldom lives to old age, most octogenarians being thin and wiry, and almost all attribute their long life to increasing watchfulness over their health, and largely over what they eat. When a person is young and taking active exercise, a good deal of surplus food can be worked off, and if the excess be too great, a bilious attack tends to prevent any more being taken, for a time at least. But as we get on in life, the surplus food, if much is eaten, is deposited in various parts of the body as fatty or gouty accumulations. The liver becomes deranged, and loss of health and strength are at once apparent. It is then, as Sir Henry Thompson has well pointed out, that the fond but foolish wife often does her husband incalculable harm by her efforts to "keep up his system." She urges and tempts him to take more food, fetching him, between meals, cups of beef-tea, soup, or cocoa, when he really would be greatly the better of total abstinence from all food for several days. What we have said about appetite being the best guide applies to the old especially, and if they could but realize what a very small quantity of food is necessary, they would not be perturbed to find that their appetite guided them to eat very much less than at a younger age. Milk, which is the ideal food for the very young, is for that reason often undesirable for the old, and it is a great mistake for such to drink much of it with solid food.