66 ELEMENTARY PHYSIOLOGY 



QUESTIONS ON LESSON XI. 



1. Describe the structures which surround the cavities of the nose. 



2. In what way is the cavity of the nose separated from that of the brain ? 



3. Describe the structure of the palate. 



4. Give a brief description of the pharynx. What are the openings leading 



into it ? 



5. Describe the positions, and compare the structures of the trachea and of 



the a>sophagus, 



6. Describe the course taken by food and drink after leaving the mouth. 



7. What is the course taken by the air during ordinary breathing ( I ) When 



the mouth is closed, and (2) When the mouth is open ? 



8. Describe the position and use of the epiglottis. 



9. What do we mean when we say that a particle of food has ' gone the 



wrong way ' ? 



LESSON XII. 



THE ORGANS OF THE THORAX. 



THE thorax or chest contains 



The trachea and its branches. 

 The lungs. 



The heart and its great vessels. 

 The esophagus. 



The trachea or wind-pipe passes downward from the throat 

 into the thorax ; and in the upper part of this cavity it divides 

 into two branches called bronchi. One of these (the right 

 bronchus) leads into the right lung, and the other (the left 

 bronchus) into the left lung. These bronchi divide and sub- 

 divide in the substance of the lungs till their branches (bronchial 

 tubes) penetrate every part of those organs. 



The lungs or lights are two large spongy organs which occupy 

 the greater portion of the thorax. They are quite distinct from 

 each other, although at some parts their adjacent surfaces are in 

 contact. A large portion of the volume of the lungs is occupied 

 by the air-tubes (branches of the trachea) and the little air-cells in 

 which they terminate ; hence the extreme lightness of these organs. 

 To show this lightness a lung or a part of one may be floated on 

 water. The general character and appearance of these organs 

 may be learnt by examining the lights of a sheep or smaller 

 animal, but it must be remembered that during life the organs are 

 much larger, being inflated with air. 



The heart is a hollow muscular organ situated nearly in the 

 middle of the front and lower part of the chest, just above the 



