The Body Organization : Part 3

Physiology and Hygiene for Secondary Schools
by Francis M. Walters

(Page 5 of 25)

Food, shelter, air, clothing, water, and the means of protection are external to the body and form a part of its environment. In making the things about him contribute to his needs, man encounters a problem which taxes all his powers. Only by toil and hardship, "by the sweat of his brow," has he been able to wrest from his surroundings the means of his sustenance.

The Main Physiological Problems. - The study of the body is therefore seen to resolve itself naturally into the consideration of two main problems:

1. That of maintaining in the body a nutrient fluid for the cells.

2. That of bringing the body into such relations with its surroundings as will enable it to secure materials for the nutrient fluid and satisfy its other needs.

The first problem is internal and includes the so-called vital processes, known as digestion, circulation, respiration, and excretion. The second problem is external, as it were, and includes the work of the external organs - the organs of motion and of locomotion and the organs of special sense. These problems are closely related, since they are the two divisions of the one problem of maintaining life. Neither can be considered independently of the other. In the chapter following is taken up the first of these problems.

Summary. - The individual parts, or units, that form the body organization are known as cells. These consist of minute but definitely arranged portions of protoplasm and are held together by the intercellular material. They build up the body and carry on its different activities. The tissues are groups of like cells. By certain general activities the cells maintain their existence in the tissues and by the exercise of certain special activities they adapt the tissues to their purposes in the body. The body, as a cell organization, has its activities directed under normal conditions toward a single purpose - that of maintaining life. In the accomplishment of this purpose a nutrient fluid is provided for the cells and proper relations between the body and its surroundings are established.

Exercises. - 1. If a tissue be compared to a brick wall, to what do the separate bricks correspond? To what the mortar between the bricks?

2. Draw an outline of a typical cell, locating and naming the main divisions.

3. How do the cells enable the body to grow? Describe the process of cell-division.

4. How does the general work of cells differ from their special work? Define absorption, excretion, and assimilation as applied to the cells.

5. Compare the conditions surrounding a one-celled animal, living in water, to the conditions surrounding the cells in the body.

6. What is meant by the term "environment"? How does man's environment differ from that of a fish?

7. What is the necessity for a nutrient fluid in the body?

8. Why is the maintenance of life necessarily the chief aim of all the activities of the body?

9. State the two main problems in the study of the body.

Practical Work

Observations. - 1. Make some scrapings from the inside of the cheek with a dull knife and mix these with a little water on a glass slide. Place a cover-glass on the same and examine with a compound microscope. The large pale cells that can be seen in this way are a variety of epithelial cells.

2. Mount in water on a glass slide some thin slices of cartilage and examine first with a low and then with a high power of microscope. (Suitable slices may be cut, with a sharp razor, from the cartilage found at the end of the rib of a young animal.) Note the small groups of cells surrounded by, and imbedded in, the intercellular material.

3. Mount and examine with the microscope thin slices of elder pith, potato, and the stems of growing plants. Make drawings of the cells therefore observed.

4. Examine with the microscope a small piece of the freshly sloughed off epidermis of a frog's skin. Examine it first in its natural condition, and then after soaking for an hour or two in a solution of carmine. Make drawings.

5. Mount on a glass slide some of the scum found on stagnant water and examine it with a compound microscope. Note the variety and relative size of the different things moving about. The forms most frequently seen by such an examination are one-celled plants. Many of these have the power of motion.

6. Examine tissues of the body, such as nervous, muscular, and glandular tissues, which have been suitably prepared and mounted for microscopic study, using low and high powers of the microscope. Make drawings of the cells in the different tissues therefore observed.

D.C. Heath and Co. - Publishers
Original copyright 1909