LARYNX TRACHEA. 



93 



The lungs are supplied with air through the larynx, trachea, 

 and bronchia. The larynx, the organ of the voice, of which 

 we shall speak later, is continuous below with the trachea. 

 This is a cylindrical tube flattened behind; it is composed 

 of a series of cartilaginous rings united by a fibrous membrane, 



Fig. 25. Section showing the ramifications of the bronchi in the lungs. 

 A. Trachea. B, C. Bronchi. D, D. Bronchial tubes. 



and lined with a mucous membrane; it is placed in the an- 

 terior portion of the neck, and passes vertically from above 

 downward. The rings of the trachea do not extend quite 

 round it; interrupted in their circuit towards the posterior 

 fourth of the tube, they are, properly speaking, only segments 

 of a circle. They number from sixteen to twenty, and pro- 

 duce a corresponding number of protuberances on the surface 

 of the trachea, which is thereby rendered rough and wavy to 

 the touch. It is from this circumstance that it derives its 



