248 



HITCHCOCK'S AXAT05IT 



hexagonal figure surrounding the bronchial tube, shows a 

 section of a lung;let, or lobule of the lung. 



433. The Pleura —Pleurisy.— Root of the Lungs.— The 

 lungs are immediately invested with a serous membrane called 

 the Pleura, which is also the inner lining membrane of the 

 walls of the chest : so that when the lungs are fully inflated, 

 these two surfaces arc brought in contact, and in the act of 

 respiration move slightly upon each other. And if any por- 

 tion of these membranes becomes inflamed, the disease results 

 which is known as Pleurisy. In the acute or early stage of 

 this disease, if a long breath be drawn, intense pain is felt at 

 the lower portion of the lung. This is owing to the friction 

 of these inflamed membranes one upon the other, and the 

 reason why the pain is severest in the lower part of the lung, 

 is that this part of the lung moves over the largest space in 

 breathing. The vessels for supplying blood, emptying it 

 and nourishing the lungs, as well as the air-vessels, nerves 

 and lymphatics, are all collected together in one bundle at 

 the inner side of these organs, and are collectively called the 

 Root of the Lungs. 



439. Tlie Air Passages, — The vessels which are especially 

 designed for the purpose of conveying air into the lungs are 

 the Larynx, from the Greek meaning a whistle, since sound 

 is made in it — the Trachea, meaning rough, as is its struc- 

 ture — tbe Bronchia, meaning the windpipe, (Pig. 250, p. 

 249), and the intercellular passages which terminate in the 

 air-cells. (Fig. 252, p. 250.) 



440. Til C Larynx. — The Larynx is a conical cartilaginous 

 tube from one to two inches in diameter, opening upwards into 

 the Pharynx, and terminating below in the Trachea. (See 

 Organs of V oice.) 



441. The Trachea. — The Trachea is a cartilaginous tube 



433. What are the lungs covered with, and what is the chest lined with? What is 

 Pleurisy? What is meant by the root of the lung? 4o9. Give the names of the dif- 

 ferent parts of the air-passages. 440. Describe the Larynx. 



