28 
MANUAL OF NATURE) STUDY. 
improper soil or improper air or poisoned water. 
That plants grown in one soil and atmosphere will 
develop into stronger plants than if grown in an¬ 
other. Let the pupils give instances. Since the 
plant which grows in the garden or the timber 
which makes 'the frame work of the house must 
have just the right kind of food and drink, so 
must the bone of the growing boy have pure blood 
in order to make strong bone in manhood. Alco¬ 
hol and tobacco poison the blood and therefore 
dwarf the growth of bone. 
Breathing . — a . Organs. b. Process of. c . 
Purposes, d. Position of body in. e . Bad effects of 
improper position of body, breathing impure air, 
improper breathing. 
Lhssons. 
1. Begin this subject by a breathing exercise 
by the whole school. Require the children to take 
a full breath, by standing erect and closing the 
mouth. What change is made in form of chest 
and abdomen while taking a full inspiration? 
During expiration? What muscles are used most 
in breathing? Could these muscles act freely if 
tightly bandaged? Why do we breathe? That 
which receives the air in inspiration is called the 
lungs. These lungs surround the heart, which is 
the blood pump. 
