more than any other class of influences, prevent the attainment of long life.
As a rule, women need about nine-tenths of the nourishment requisite for men; boys of 16 about the same as women, and children of 10 years half the amount necessary for adults. Individual peculiarities, whether temporary or permanent, should be studied and conformed to with the utmost care.
Quantities at Different Meals.—The quantity of food taken into the stomach at different meals is a matter of great importance. Speaking generally, the morning meal should comprise one-third of the meat and two-sevenths of the starchy nutriment; dinner should include the remaining two-thirds of the meat and three-sevenths of the starchy materials; and the evening repast consist of the last two-sevenths of the saccharine and starchy matters.
Few adults and hardly any children and old people, can be careless about their diet without suffering severely later on, even if no ill effects are immediately experienced.
Mental anxiety or labour, as well as bodily exertion, should be avoided during, and for half an hour after, a full repast. Lighter meals may be advantageously followed by gentle exercise, such as walking or moderate work. Complete mastication of the food is vitally important to health and long life.
Exercise.—Exercise, in the strict signification of the word, means the performance of its function by any and every organ of the body. As generally used, however, it signifies the action of the muscles under control of the will.
The most important effect of exercise is felt by the lungs and the heart. The circulation of the blood is hurried much above the ordinary rate, and, as a consequence of this greater influx of blood to be oxygenated in the air-cells, the quantity of air inspired, and the amount of carbonic acid exhaled, are both largely increased. During active exertion, therefore, the free play of the lungs should not be impeded by tight-fitting clothes.
Muscular exertion very speedily increases the force and frequency of the heart's pulsations; to a moderate extent, this is very beneficial to the organ, but care must be taken that it is not overdone, even by the strongest. Persons suffering with "weak heart" should indulge in athletics only under medical advice.
Severe muscular exertion increases the flow of blood in the small blood-vessels of the skin, and causes a profuse discharge of perspiration, which may be even doubled or trebled in amount. During active exercise there is little danger of chill; but immediately afterwards, and also during the intervals of rest, the skin should be so warmly protected as to prevent the least coolness of the surface. For this purpose flannel is by far the best covering.
Moderate exercise causes the muscles employed to increase in size,
