PROBLEM 212 



243 



extra deep breath. Place your hand on your chest and take a deep 

 breath. What happens to the ribs? 



Conclusion. Does taking in air (inspiration) require greater 

 effort than sending it out (expiration) ? Explain. 



Problem 211 : To stiidy the part the ribs play in respira- 

 tion. (Modified from Eddy's General Physiology.} 



Method. Using some strips of heavy cardboard and four 

 paper fasteners, construct a model as shown in the left-hand 

 figure. The largest strip of 

 cardboard represents the back- 

 bone. Parallel to it. is the 

 breastbone or sternum. The 

 cross pieces are two of the 

 ribs. 



Observations. What hap- 

 pens to the distance between 

 the backbone and the sternum 

 of our model when the mus- 

 cles raise the ribs to a hori- 

 zontal position as shown in 

 the -right-hand figure? 



Conclusion. -- What hap- 

 pens to the capacity of the chest cavity when the ribs are 

 raised ? 



Problem 212 : What is the function of the diaphragm ? 



Materials. Small bell jar with opening at top for rubber cork 

 containing one opening, Y tube, balloons, and rubber sheet 

 arranged as shown on page 333, Civic Biology. 



Method. The glass tube represents the trachea ; the branches, 

 the bronchial tubes; the balloons, the lungs; the rubber sheet, 

 the diaphragm ; and the walls of the chest cavity are repre- 

 sented by the sides of the glass bell jar. 



Observations. Lower the diaphragm by pulling the rubber 

 sheet downward. What is the effect on the air capacity of the 

 jar when the rubber is pulled down? 



