THE LUNGS. 



Questions. 



Is the constant action of the heart necessary to our exist- 

 ence 1 ? 



What is the heart, and where is it placed 1 



What part of the heart is it we feel when it contracts 1 



How many cavities are there in it 1 



By what means is the hlood expelled from it 1 



Is our heart single or double ? 



For what purpose is the blood circulated through our bo- 

 dies 1 



Try to describe the course of the circulation. 



What produces the pulse, and how often does this beat at 

 different ages 1 



Do the veins pulsate 1 



What change does blood undergo when taken from the 

 body? 



Into how many parts does it divide itself? 



Can you name these ? 



LESSON XL 



THE LUNGS AND THEIR APPENDAGES 



-; RESPIRATION. 



ONE of the most important actions of our system 

 is breathing. This is so essential to life, that if it 

 be interrupted for a very short space of time, we 

 die from suffocation. Breathing consists of two 

 actions : inspiration, or drawing in the air ; and 

 expiration, or forcing out the air. 



The lungs are soft, spongy bodies, full of very 

 small hollows, called air-cells. The thorax, or 



