Observation. When the body has become emaciated from want of nutriment, either from famine or disease, there is an increased demand for food. This may be gratified with impunity until the individual has regained the usual size, but repletion should be avoided.
277. Food is required to repair the waste, or loss of substance that attends action. In every department of nature, waste, or loss of substance, attends and follows action. When an individual increases his exercise,—changes from light to severe labor,—or the inactive and sedentary undertake journeys for pleasure, the fluids of the system circulate with increased energy. The old and exhausted particles of matter are more rapidly removed through the action of the vessels of the skin, lungs, kidneys, and other organs, and their places are filled with new atoms, deposited by the small blood-vessels.
278. As the chyle supplies the blood with the newly vitalized particles of matter, there is, consequently, an increased demand for food. This want of the system induces, in general, a sensation of hunger or appetite, which may be regarded as an indication of the general state of the body. The sympathy that exists throughout the system accords to 131 the stomach the power of making known this state to the nervous system, and, if the functions of this faithful monitor have not been impaired by disease, abuse, or habit, the call is imperious, and should be regarded.
276. At what age is the appetite keen and the digestion vigorous? Why? What is said in regard to the quantity of food when the youth has attained his growth? What exception, as given in the observation? 277. Give another demand for food. What effect has increased exercise upon the system? 278. How are the new particles of matter supplied? What does this induce?
279. When exercise or labor is lessened, the quantity of food should be diminished. When a person who has been accustomed to active exercise, or even hard manual labor, suddenly changes to an employment that demands less activity, the waste attendant on action will be diminished in a corresponding degree; hence the quantity of food should be lessened in nearly the same proportion as the amount of exercise is diminished. If this principle be disregarded, the tone of the digestive organs will be impaired, and the health of the system enfeebled.
280. This remark is applicable to those students who have left laborious employments to attend school. Although the health is firm, and the appetite keen from habit, yet every pupil should practise some self-denial, and not eat as much as the appetite craves, the first week of the session. After some days, the real wants of the system will generally be manifested by a corresponding sensation of hunger.
Observation. It is a common observation that in academies and colleges, the older students from the country, who have been accustomed to hard manual labor, suffer more frequently from defective digestion and impaired health than the younger and feebler students from the larger towns and cities.
281. Food is essential in maintaining a proper temperature of the system. The heat of the system, at least in part, is produced in the minute vessels of the several organs, by the union of oxygen with carbon and hydrogen, which the food and drink contain. The amount of heat generated, is greatest 132 when it is most rapidly removed from the system, which occurs in cold weather. This is the cause of the system requiring more food in winter than summer.
279. Why should the quantity of food be diminished when the exercise is lessened? What effect if this principle be disregarded? 280. To what class is this remark applicable? What is often observed among students in academies and colleges? 281. State another demand for food. What is one source of heat in the body?
Observation. Persons that do not have food sufficient for the natural wants of the system, require more clothing than those who are well fed.