CHAPTER XV. 

 RESPIRATION OR BREATHING. 



1. The Use of Respiration is to renew the air in the 

 lungs. This is necessary because the blood, as it flows 

 through the lungs, is all the time taking something 

 from the air within them, and giving something to it. 

 If this air were not passed out, and fresh air taken in its 

 stead, it would soon have nothing left of what the blood 

 wants. It would also become so loaded with the waste 

 matter the blood gives off to it, that it could take no 

 more of it, and so the blood would not be purified. 

 Suffocation is death from want of fresh air in the lungs. 



2. What the Blood Takes from the Air. Blood gets 

 nourishment for the body from the alimentary canal. 

 But we have learned (Chap. VIII.) that in order that 

 foods may give us power and keep us warm, they must 

 be oxidized, and, clearly, they cannot be oxidized unless 

 oxygen is supplied. The blood, into which the digested 

 foods are taken, as it flows through the lungs absorbs 

 this necessary oxygen. 



3. What the Blood Gives to the Air. The blood in its 

 passage through the lungs gives off to the air, heat, 



1. What is the use of respiration? Why is it necessary? What is 

 suffocation ? 



2. Where does blood get nourishment for the body ? Why is 

 oxygen necessary as well as food ? Where does the blood get 

 oxygen ? 



3. What does blood give to the air as it passes through the lungs ? 



