While fruits technically include all those plant products which bear or contain the seed, we shall include in our dietetic class of fruits only the pulpy fruits. From a dietetic standpoint, the most practical classification of fruits is into three groups - namely, acid, bland, and sweet. We include under the acid fruits those which require the addition of sugar to make them palatable. Under sweet fruits Ave include those that naturally contain so much sugar that no more is required to be added, either in the preservation or in their use in the menu. Under the bland fruits, which is much the longest list, are included those varieties which are neither distinctly acid nor distinctly sweet. The most typical and widely used acid fruits are the citrous group, comprising lemons, limes, grape fruit, oranges, etc. Those typical of the sweet fruits are figs and dates, while the most typical bland fruits are pears, grapes, blackberries, blueberries, melons, and bananas. This classification of fruits is valuable because it is based upon their dietetic use.

Group A. Acid Fruits

Physiologically, acid fruits are valuable for the acids and organic salts which they contain. These are citrates, malates, or tartrates of potassium, sodium, magnesium, and calcium. In the juice of the citrous fruits, for example, we have citrates of these minerals; in apples, pears, peaches, and apricots, malic acid and malates; while in grapes tartaric acid and the tartrates predominate. When these fruit juices are taken into the digestive canal, they are readily absorbed and carried with the absorbed food to the liver, where the acids and the acid elements of the organic salts are oxidized, releasing the potassium, sodium, magnesium, etc., which are changed to carbonates at once and thus increase the alkalinity of the blood. Furthermore, these alkalies are soon eliminated by way of the kidneys. This accounts for the diuretic effect of the acid fruits.

At first thought, the idea of acid fruit juice causing the blood to become more alkaline seems paradoxical, but the fact remains and has been amply demonstrated, and when explained as above, seems most reasonable.

The acid fruits comprise the following varieties: lemons, limes, grape fruit, oranges, cranberries, gooseberries, whortleberries, pineapples, currants, and rhubarb. As explained above, under green vegetables, while rhubarb is not a fruit, it is used in the menu as such. It might be remarked in passing that while the tomato is really a fruit, it is used in the menu as a vegetable, and we will classify it dietetically as such. The acid fruits are wholesome in a general way, because of their influence particularly on the action of the kidneys, all of them stimulating that action. The citrous fruits possess this quality in the strongest degree, and are indicated for free use whenever it is desired to produce free elimination from the kidneys and skin. Rhubarb possesses the quality also of a laxative, as set forth above. While sweet oranges may be eaten without addition of sugar, the acidity of most of the fruits of this group is so intense as to require the addition of considerable sugar to make them palatable. However, such addition does not in any way detract from the value of the acid and organic salts. All of the fruits possess pulp, seeds, and skin. The seeds and skin are usually removed in the preparation of the fruit for eating. However, in the case of strawberries, raspberries, blackberries, blueberries, bananas, figs particularly, the seeds are small and surrounded by pulp and are usually taken with the pulp. While they pass through the alimentary canal undigested, they are usually not only harmless but in most cases positively advantageous, because of the mechanical stimulus which they exert upon the peristaltic action of the walls of the intestines.

Group B. Bland Fruits

Under this head we group a large number of fruits whose acidity is usually not so great as to require the addition of sugar to make them palatable, and yet whose sugar content is not great enough to justify their classification as sweet fruits. Naturally, there will be found in this group some fruits which present varieties sufficiently acid to justify their classification under acid fruits, and other varieties which are so sweet as to justify their classification under the sweet fruits. For example, cherries exist in acid, bland, and sweet varieties; the same with apples, plums, and strawberries; perhaps, also, with apricots and peaches. On the other hand, pears, grapes, raspberries, blackberries, blueberries, mulberries, melons, and bananas, when thoroughly ripe, are so sweet as to need no further addition to make them edible. However, even this group does not contain enough sugar to make these fruits important sources of sugar in the diet, so that we hardly eat them for nourishment, but resort to them because of their appetizing flavors.