QUESTIONS 
403 
the small puppy is turning into a full grown dog. During 
this period of change the boys and girls, the tree, and the 
puppy are all nourished by food and this makes it possible 
for them to grow. 
Maturity is the period when man ceases to grow taller, 
although he continues to eat food as he did during the period 
of youth. The living protoplasm in his body does not in¬ 
crease in amount. The same can be said of the tree, for 
it does not grow taller; and the puppy of last year has 
become a full grown dog. During this period of maturity, 
each living organism is able to repair its body as fast as the 
body wears out. The period of maturity varies with differ¬ 
ent things ; in some butterflies lasting but twenty-four hours, 
in man continuing for about twenty-five years. 
Old age in man begins when the body wastes faster than it 
is repaired, and in the tree when growth is over and decay 
begins. During this period of old age all living things use 
food as they did in youth and maturity, but it cannot build 
up the body as fast as it is worn out and death is the final 
result. Old age occurs at different ages in different individ¬ 
uals ; and the same is true of animals and plants. 
SUMMARY 
Man has the same life processes as the animals. He is able 
to live in all climates and localities on the earth. No plant 
or animal can do this. Civilized man has learned to control 
his surroundings. Animals and plants are controlled by their 
surroundings. Man like all other living things passes through 
periods of growth, known as youth, maturity, and old age. 
QUESTIONS 
What have you learned about plants and animals that will help you 
to understand how man lives? Where are the earliest records of man 
found? Why do men migrate? Why can man control his environ¬ 
ment? How do you understand the terms youth, maturity, and old 
age? 
