GENERAL CONSIDERATIONS.
Physiology teaches that life can only be maintained in the living organism by a constant equilibrium between its waste and repair. Nutrition is a term by which we describe this double movement of renewal of the molecular structure of the body, and in this general sense only, that nutrition is synonymous with the maintenance of the organism in a stable condition, is it employed here.
This condition of equilibrium is maintained by a regular and constant supply of food.
A food may be defined to be a substance which, after introduction into the body, supplies material for the renewal of its tissues or sustains some of its vital processes. Foods vary greatly in their properties as restorative or constructive agencies, some containing but few essential properties, while others combine almost all of the elements required. As some foods contribute elements for tissue restoration, others are specially concerned in the calorifacient activities of the organism,[948] while others are marked in their tendency to take part, almost exclusively, in special chemical processes.[949]
The various articles used as foods contain nutritive elements combined with innutritious substances. They have been variously classified, but are conveniently divided into
| I. Organic foods, | { | a. Nitrogenous (C.H.O.N.). |
| b. Non-nitrogenous (C.H.O.), | { | Oleaginous Carbohydrates. |
| II. Inorganic foods, | { | a. Water, H2O. b. Saline substances. |
Nitrogen enters largely into the composition of the body, and hence must be abundantly supplied and in combination.
Of the non-nitrogenous elements the most important are fat, sugar, and starch.
The inorganic principles are essential to the process of nutrition. Water, constituting 87 per cent of the bulk of the body, is demanded in constant supply; while the saline substances are necessary for the perfect performance of many of its chemical processes.
It is apparent that no single element can alone carry on the nutrition of the body, and hence variety in the supply of food, as well as sufficiency in its quantity, is essential to normal nutrition. Nor are these the only factors in this complex problem. Proper preparation of food, its supply at necessary temperatures,[950] and other requirements enter into the question of normal or sufficient alimentation.[951]
Alimentation is sufficient when it is so regulated that all the functions of the body are performed in a complete and regular manner. Insufficient alimentation induces a series of phenomena and a result which have been designated “inanition,” or “starvation.”
The exact amount of aliment required by each individual can only be stated in a general way. In the circumstances in which he is placed, the supply must be of such character and quantity as shall be proportionate to the constructive and reparative needs of his body. It is possible, however, to state a mean for the various ages and occupations of life.
Physiologists generally agree that in ordinary conditions of exercise the following represents the amounts of the several food elements necessary for the adult individual daily:
| Albuminous substances | 120 | gms. | = | 4 | oz. |
| Fatty substances | 60 | ” | = | 2 | ” |
| Carbohydrates | 360 | ” | = | 12 | ” |
Taking the fatty matters as the unit, the daily allowance would bear the following proportions:
Fats, 1; albuminoids, 2; carbohydrates, 6.
These quantities and especially the fats and carbohydrates, in conditions of hard muscular labor, must be increased; and the proportion would then stand:
Fats, 1; albuminoids, 1.7; carbohydrates, 7.
The division of this amount of food elements into proper portions during twenty-four hours is important. This must be regulated by the habits and other circumstances of the individual.[952]
The occurrence of death solely from privation of food is comparatively rare; yet it is sufficiently frequent to be considered as one of the causes of violent death and to demand investigation, since circumstances may be such as to constitute a homicide from criminal neglect or a suicide from intentional abstinence from food.
“Starvation,” or “inanition,” may be considered as being acute or chronic according as the requisite food has been suddenly and completely or gradually withheld.