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 study 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 diaiphragm by pulling the rubber 

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

 jar when the rubber is pulled down? 



