How many times do we naturally breathe in a minute?
What are some of the effects of breathing impure air?
How is the oxygen carried by the blood?
What is animal heat?
What is the temperature of the body?
These questions were all answered fairly well by the class, but the answers contained only so many bits of isolated information, and the pupils did not understand the subject after they had recited upon it. Another teacher asked the following questions:
Why must the body have air to breathe?
Of what use is oxygen in the body?
Where does this oxidization, or burning up of worn-out cells, take place?
But how is the oxygen carried to every part of the body and brought into contact with the tissues?