KEY:  1, percentage of nutrients; 2, fuel value of 1 pound in calories.  The unit of heat, called a calorie, or gramme-degree, is the amount of heat which is necessary to raise one gramme (15.43 grains) of water one degree centigrade (1.8 degrees Fahr.).  A, round beef; B, sirloin beef; C, rib beef; D, leg of mutton; E, spare rib of pork; F, salt pork; G, smoked ham; H, fresh codfish; I, oysters; J, milk; K, butter; L, cheese; M, eggs; N, wheat bread; O, corn meal; P, oatmeal; Q, dried beans; R, rice; S, potatoes; T, sugar.

This table, among other things, shows that the flesh of fish contains more water than that of warm-blooded animals.  It may also be seen that animal foods contain the most water; and vegetable foods, except potatoes, the most nutrients.  Proteids and fats exist only in small proportions in most vegetables, except beans and oatmeal.  Vegetable foods are rich in carbohydrates while meats contain none.  The fatter the meat the less the amount of water.  Thus very lean meat may be almost four-fifths water, and fat pork almost one-tenth water.

[Illustration:  Fig. 45.—­Graphic Chart of the Composition of Food Materials.  Composition of Food Materials.  Nutritive ingredients, refuse, and fuel value. ]

114.  Non-proteid Animal Foods.  Butter is one of the most digestible of animal fats, agreeable and delicate in flavor, and is on this account much used as a wholesome food.  Various substitutes have recently come into use.  These are all made from animal fat, chiefly that of beef, and are known as butterine, oleomargarine, and by other trade names.  These preparations, if properly made, are wholesome, and may be useful substitutes for butter, from which they differ but little in composition.

115.  Garden Vegetables.  Various green, fresh, and succulent vegetables form an essential part of our diet.  They are of importance not so much on account of their nutritious elements, which are usually small, as for the salts they supply, especially the salts of potash.  It is a well-known fact that the continued use of a diet from which fresh vegetables are excluded leads to a disease known as scurvy.  They are also used for the agreeable flavor possessed by many, and the pleasant variety and relish they give to the food.  The undigested residue left by all green vegetables affords a useful stimulus to intestinal contraction, and tends to promote the regular action of the bowels.

116.  Fruits.  A great variety of fruits, both fresh and dry, is used as food, or as luxuries.  They are of little nutritive value, containing, as they do, much water and only a small amount of proteid, but are of use chiefly for the sugar, vegetable acids, and salts they contain.

In moderate quantity, fruits are a useful addition to our regular diet.  They are cooling and refreshing, of agreeable flavor, and tend to prevent constipation.  Their flavor and juiciness serve to stimulate a weak appetite and to give variety to an otherwise heavy diet.  If eaten in excess, especially in an unripe or an overripe state, fruits may occasion a disturbance of the stomach and bowels, often of a severe form.