294 



RESPIRATION AND EXCRETION 



Front, 

 jyutmonaTy 



artery 



2. What effect when the ribs by their own elasticity return 

 to their original position ? 



3. In what two ways 

 do you now know the 

 chest cavity may be en- 

 larged ? 



4. How does air get 

 into the air cells of the 

 lungs ? 



c. Process of Respiration 

 in the Lungs 



Observations. 1. How 

 do air tubes end in the 

 lungs ? 



2. Why are these end- 

 ings so thin-walled? 



3: What does Figure 73 

 illustrate ? 



Conclusions. 1. Just 

 take place in the lungs ? 

 here? 



FIG. 73. Diagram to show respiration in 

 the lungs. 



how does the process of respiration 

 2. Just what changes take place 



d. Cell Respiration 



Observations. 1. What does Figure 74 illustrate? 



2. What wastes are formed when food is oxidized at the 

 cells? 



3. What desirable results when food is oxidized? 



Note. Observations 2 and 3 may be illustrated chemically 

 as follows : 



Starch + oxygen = carbon dioxide + water + heat + muscular energy. 1 

 C 6 Hi 5 + 6 O 2 = G C0 2 + o H 2 -f heat + muscular energy. 



1 Heat and muscular energy are both energy resulting from the oxidation 

 of what ? Where does the oxidation take place ? About 30% is muscular en- 

 ergy, the remaining 70 % is bodily heat. 



