Prof. M. E. Jaffa, of the University of California, has experimented at length on diets of fruits and nuts. Two women and three children comprised a family and had lived on fruit for seven years. They ate twice a day. Breakfast, 10.30 a.m. This meal consisted of nuts and fruit. Dinner, 5 p.m. At this meal they ate no nuts, but in addition to fruit, olive oil and honey. They used almonds, Brazil nuts, pine nuts, and walnuts. The fruits were fresh and dried. Among them were apples, apricots, bananas, figs, grapes, olives, oranges, peaches, pears, plums, and raisins. Now and then some celery and tomatoes were used. The tomato may now be classed as a fruit, as developed by improvement from a vegetable. All enjoyed their meals and discussed them generally every day. The children were always active, romping, and playing. The results of the tests showed a small amount of proteids and energy, much below the figures heretofore considered necessary for a man doing moderate muscular work. The results were about the same as those obtained from experiments made on vegetarians.

Jaffa thinks his subjects on fruit and nut diet were undernourished. The two grown persons in the family, on the other hand, claimed that they had lived on the diet seven years, and were in better health and more capable of work than ever before. The three children appeared healthy and vigorous and were free from sickness usual among children. The cost per day for each person varied from eighteen to forty-six cents. Continuation of experiments showed Jaffa that while a fruit diet in many cases gave a man enough to live on and to work on, yet in the majority of cases exclusive fruit and nut diets fell far below the tentative standards.

Let us look at fruit as food from an economic stand-point and reckon in fuel values. A pound of potatoes will give 325; a pound of wheat flour, 1640; a pound of cornmeal, 1655; a pound of oatmeal, 1860; a pound of milk, 325; a pound of fat beef (hind quarter), 1135; a pound of oysters, 35; a pound of apples, 225; a pound of apricots, 225; a pound of blackberries, 245; a pound of grapes, 320; a pound of pears, 235; a pound of plums, 370; a pound of raspberries, 255; a pound of strawberries, 155. Average of fruits, 256. As to vegetables, a pound of beets, 170; cabbage, 140; carrots, 170; lettuce, 85; onions, 210; parsnips, 285; green peas, 200; pumpkin, 60; rutabaga turnips, 135; squash, 125; tomatoes, 105. Average of vegetables, 153. The tables show that fruit costs about ten times as much as flour, corn meal, and such articles; taking into consideration their food values; therefore there must be found other considerations than that of food value for eating fruits.

No one but a fanatic will claim that fruit alone will furnish a complete diet for man. Yet at the same time it does form a healthy and really an essential part of a complete diet, and it is coming more and more into use in all parts of the world; it is becoming more and more a staple product in our markets, and is becoming better and cheaper all the time, and is thus offering to mankind an economic advantage over the mere spontaneous productions of the ground enjoyed by his ancestors.

Fruits have long been a great part of the diet of the older races, and of the semicivilized and savage tribes. The latter, especially of the tropics and temperate latitudes, live on fruits, fish, and starchy vegetables, and these people are usually healthy, strong, and vigorous, and were more so until their more civilized and enlightened brothers introduced among them the various seductive poisons of a higher civilization. As a rule, with fruit we take much bulk that is not nutritious, and this very bulk is useful, because it prevents us eating too much of the stronger articles of diet. Given fruit as the first course at breakfast, and we will not be so apt to overload our stomachs with buckwheat cakes and sausages, and the fruit taken will in many ways help us to get comfortably rid of the greater burden, the sugars and acids of the fruit being the factors here. The aroma of the fruits is pleasing to the senses, and thus aids secretion in various forms, especially of the digestive juices. Taking this view of the matter, fruit is better taken with the meal, and before the meal rather than after. During the meal especially we crave condiments or something to cater to our taste and bring out a proper secretion of the digestive juices and ferments, and to accomplish this we eat cranberry with our turkey, currant jelly with our roast mutton, capers with our boiled mutton, roast apple with our goose, and apple sauce with our roast pork. A good scientific reason for eating these fruits is that the fats of the meats with which they are eaten are, as a rule, neutral fats; that is to say, they have not sufficient acid in them to cause the alkaline bile and pancreatic fluid to emulsify these fats, and the fruit acids here make up the deficiency in nature. We also use vinegar to dress our salads, because it dissolves the cellulose of the raw vegetable of the salad. The oil in the salad also makes the vinegar more acceptable to the stomach. What a teacher nature is, anyhow!

Fruits contain much water, and the general make-up is finished with sugars, starches, the gelatinous substance called pectin, acids, and cellulose, the cellular tissue, compound of carbon, hydrogen, and oxygen. When fresh they are markedly antiscorbutic and appetizing. Pectin is a carbohydrate, and the quince contains a large amount of it, making it especially good for jelly. The acids of fruits are the citric, the tartaric, especially in the grape, and the malic, which exists largely in the apple particularly.

The organic acids are in union with alkalies, and these form salts, and these salts are split up in the system and leave the alkalies free, which usually combine and form carbonates or phosphates with acids found in the body. Again, this is a fact of great importance both practically and scientifically.

Why do we give lemon juice and expect benefit, in rheumatic fever for instance, when the blood is so acid already that the profuse perspirations change litmus blue to red almost by their fumes before contact? We can answer, in giving lemon juice in such cases, or any other fruit juice, we do not give it as an acid to increase the already over-acid condition of the blood. We give it, paradoxical as it may appear, as an alkali, to increase the alkalinity of the blood, bringing this about by the citric acid of the lemon, being combined with salts, and these salts splitting up and reappearing as carbonates and phosphates, and these reducing the acidity of the blood, and thus aiding the return to health of the rheumatic condition. Even if the citric acid of the lemon is free, it meets salts in the system, and does the same good in a more direct way. This matter is all important. Thus acid fruits are not an acid diet, and do not by their acidity slow or check normal digestion.

Such fruits as figs and prunes are useful mechanically to free the slow bowels, as by their seeds and skins they encourage peristalsis, etc., and hence relieve constipation and its kindred ills. They are thus most useful fruits in more ways than one.

Some fruits contain a little fat and waxy matter, as the olive, but, as a rule, sugars and starches predominate, with a very little nitrogen in the shape of vegetable albumin. Their aroma and flavor are given by various essential oils and compound ethers inherent in them and generated in the ripening of the fruit. The mango steen of Borneo and the durian of Java are said to hold these above all others and to be the most luscious of all fruits. The cultivation of sour fruits, whether in a temperate or a hot climate, reduces the acid in them and improves their aroma and flavor.

There is one thing always to remember in eating fruit of any and all kinds, - they are invariably an inviting host for all pathogenic and other germs, and should never be eaten until the outer skin has been removed or until they have been thoroughly washed and cleansed. The boy's green-apple bellyache comes as often from the pathogenic germs that go down with his apples as from any indigestible properties pertaining to the fruit he has eaten. A good anecdote is told of the great Pasteur, who, above all other men, probably knew of the risks we run from taking in pathogenic germs with our food. Pasteur was dining, and among other things cherries were served with the fruit Pasteur was very careful to thoroughly wash his cherries before eating them, and delivered quite a lecture on pathogenic germs and their dangers, to those about the table, among whom were several children. The dinner finished, Pasteur, wanting water, in the absent-minded way often attributed to great men, quaffed off the water in which he had washed his cherries, and the children chaffed him in great glee. Here were two object-lessons in nature study, one on absent-mindedness, and one on pathogenic germs.

Fruits are usually classified as stone fruits, pomes, or the fleshy fruits, like the apple or pear, berries, capsules, or covered fruits, and the pepos, or melon family. Some, like the banana and the date, will support life for a long time, on account of the great amount of sugar in them; others, like the pear and the apple, are helps in the general diet; and others again have less nutritive value than these, but have their uses as appetizers and digesters, as the papaw and the pineapple.

Thompson sums up the uses of fruits in the animal economy as follows: