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.