Part 1 — SUMMARY OF PART I
Reading edition
The body is an organization of different kinds of cells; it grows through the growth and reproduction of these cells; and its life as a whole is maintained by providing such conditions as will enable the cells to keep alive. Of chief importance in the work of the body is a nutrient fluid which supplies the cells with food and oxygen and relieves them of waste. A moving portion of this fluid, called the blood, serves as a transporting agent, while another portion, called the lymph, passes the materials between the blood and the cells. Through their effects upon the blood and the lymph, the organs of circulation, respiration, digestion, and excretion minister in different ways to the cells, and aid in the maintenance of life. By their combined action two distinct movements are kept up in the body, as follows:
1. An inward movement which carries materials from the outside of the body toward the cells.
2. An outward movement which carries materials from the cells to the outside of the body.
Passing inward are the oxygen and food materials in a condition to unite with each other and thereby change their potential into kinetic energy. Passing outward are the oxygen and the elements that formed the food materials after having united at the cells and liberated their energy.
As a final and all-important result, there is kept up a continuous series of chemical changes in the cells. These liberate the energy, provide special substances needed by the cells, and preserve the life of the body (Fig. 92).
In the chapters which follow, we are to consider the problem of adjusting the body to and of bringing it into proper relations with its surroundings.
[pg 216]