RESPIRATION 85 



keeping the thumb tightly in place. Test for oxygen. 

 How will you do it? Is it oxygen? How do you know? 



33. Respiration. The Necessity for Pure Air. 



Breathing consists of inhaling and exhaling. Breath- 

 ing is also called respiration. Do you know how many 

 breaths you take in a minute? How can you find out? 

 Do you always take the same number of breaths in a 

 minute? What makes you breathe faster sometimes? 

 Your heart beats faster when you breathe faster. A 

 grown person, or adult, breathes 18 times a minute, not 

 exercising, and his heart beats 72 times a minute, or four 

 times the number of breaths. Young persons breathe 

 faster and their hearts beat faster. Usually the heart 

 beats four times for each breath. 



We should breathe through our nose because it is a 

 sort of sieve which keeps the dust from passing on to the 

 lungs, and it also warms the air a little before it reaches 

 our lungs. If persons find trouble in breathing through 

 the nose they should consult a doctor. 



The amount of air which we ordinarily inhale and 

 exhale at each breath is 30 cubic inches. When we draw 

 a long breath, or "heave a sigh," the quantity of air 

 which we inhale or exhale is about 130 cubic inches. By 

 trying, we can exhale about 100 cubic inches more. Even 

 then there remains about 100 cubic inches which cannot 

 be exhaled. The amount of air which the lungs hold is 

 called their capacity. All persons do not have the same 

 lung capacity, but where the capacity is less than it 

 should be, it may be increased by breathing exercises and 

 the right kind of physical exercise. 



