The term "fruit" in a strictly botanical sense includes a very wide range of vegetable articles - the reproductive product of trees, or other plants, such as grains, legumes, nuts, berries, apples, peaches, plums, etc. In this lesson, however, I will apply the popular meaning to the term. The common succulent or juicy fruits, including both tree fruits and berries, have many properties in common. The chemical composition of these typical fruits consists of from 80 to 85 per cent water, 5 to 15 per cent sugar, 1 to 5 per cent organic or fruit-acids, and small quantities of protein, cellulose, and the numerous salts, a portion of which may be combined with the fruit-acids. Some unripe fruits contain starch and various other carbohydrate substances, many of which are distasteful and unwholesome. On the other hand, when fruits become over-ripe, and decay sets in, the sugar is changed into carbon dioxid, alcohol, and acetic acid, and the fruit rapidly deteriorates in nutritive value and unwholesomeness. These changes, together with the loss of water, account for the sponginess and the tastelessness of cold storage and other long-kept fruits. All varieties of fruit are best when they have been allowed to ripen naturally on the trees, but modern commercial conditions demand that fruits for shipping purposes be picked slightly immature, and allowed to ripen in transit to the markets.

General composition of fruit.

Dietetic value of fruits.

The fruit-acids are composed of carbon, hydrogen, and oxygen, and are burned in the body the same as sugar, or fats. The actual energy-producing content of fruit is not large, and depends almost entirely upon the sugar content. The nutrient elements of fruit consist of fruit-sugar, combinations of salts, organic acids, and various flavoring or aromatic substances. These same salts, acids, etc., purchased at the drug store, and administered separately, would be of no particular value, and might produce harmful results, but in the various combinations of fruits they have very important places in the diet.

Fruit as an aid to digestion.

One of the most important functions that fruit performs in the body is that of an artificial solvent, or an aid to digestion. To make food serve this purpose well would require some knowledge in regard to chemical harmonies, quantity, etc. To illustrate: If the stomach does not secrete a sufficient quantity of hydrochloric acid, fruit-acid should be taken at the close of the meal, provided, however, that the combinations of food consumed are in chemical harmony with the acids, and, if they are, it is important that the quantity of fruit-acid be approximately limited to the actual requirements, for if too much is taken, it is likely to cause premature fermentation and crystallization of the starch atom instead of dissolution.

The blood-crystal (crystallized starch atom), above referred to, is no doubt the secondary cause of all gouty and rheumatic conditions in the body. This explains why people of rheumatic tendency cannot take acid fruit. Fruit-acid of itself is not harmful to these conditions, but when it is taken in excess of the body requirements, or with starchy food, it is most likely to augment rheumatic conditions. People of rheumatic tendency, therefore, should confine the diet as nearly as possible to starchless foods, omitting acid fruits.

Effect of acid fruits.