CHAPTER VII.
THE BODY AND ITS COMPOSITION.
"The lamp of life" is a very old metaphor for the mysterious principle vitalizing nerve and muscle; but no comparison could be so apt.

The full-grown adult takes in each day, through lungs and mouth, about eight and a half pounds of dry food, water, and the air necessary for breathing purposes.

Through the pores of the skin, the lungs, kidneys, and lower intestines, there is a corresponding waste; and both supply and waste amount in a year to one and a half tons, or three thousand pounds.
The steadiness and clear shining of the flame of a lamp depend upon quality, as well as amount of the oil supplied, and, too, the texture of the wick; and so all human life and work are equally made or marred by the food which sustains life, as well as the nature of the constitution receiving that food.
Before the nature and quality of food can be considered, we must know the constituents of the body to be fed, and something of the process through which digestion and nutrition are accomplished.
I shall take for granted that you have a fairly plain idea of the stomach and its dependences.

Physiologies can always be had, and for minute details they must be referred to.

Bear in mind one or two main points: that all food passes from the mouth to the stomach, an irregularly-shaped pouch or bag with an opening into the duodenum, and from thence into the larger intestine.