244 



RESPIRATION AND EXCRETION 



Conclusion. — 1. What makes the balloons expand? 



2. Write a statement comparing the action of the rubber sheet 

 with that of your own diaphragm. (Remember that the action 

 of ribs and diaphragm tends to make the chest cavity larger 

 during an inspiration.) 



3. Explain fully why the lungs expand. 



4. Explain the figure on page 331, Civic Biology, and make a 

 summary of all the changes both in the blood and in the lungs. 



Problem 213 : To find out what becomes of the oxygen in the 

 lungs. 



NOTE. — We know that the oxidation of food does not take place to any great 

 extent in the lungs, but in the cells of the body where work is done. (See Civic 

 Biology, pages 331 and 332.) 



Observations. — Tell what the figure on page 332, Civic Biol- 

 ogy, illustrates, and observe the wastes that are given off after 

 food in the cell is oxidized. 



Conclusion. — 1. What carries the oxygen to the cells and 

 where does it get to these carriers ? 



2. What did the oxygen do after it got near the cell that needed 

 it? 



3. What are the wastes formed when oxidation takes place? 



4. What is the purpose of oxidation ? 



Problem 214: To m,ake a study of ventilation. 

 Materials. — A grooved box 8 X 10 inches at base, 8 inches high, 

 with sliding glass door. Place on side and have 4 half-inch holes, 



two at top and two 

 at bottom, bored in 

 each end and fitted 

 with corks. 



Method. — Place 



three candles in the 



box as shown in the 



accompanying figure. 



use up the oxygen. 



Light the candles so as to 

 Observations. — With all 



the corks in place, how long (take 



exact time) do the candles burn? 



