6 4 



ELEMENTARY PHYSIOLOGY 



ence in the front of the throat which is sometimes called Adam's 

 apple. It is the larynx or voice-box, so called because it contains 

 the vocal cords by the vibration of which the voice is produced. 

 The trachea, including the larynx, is composed of rings of cartilage 

 or gristle, connected by means of sofa fibrous tissue; and this will 

 account for the irregularity or roughness experienced by pressing 

 the fingers down the front of the throat. 



The opening leading from the pharynx into the larynx is called 

 the glottis. It is surmounted by a cartilaginous lid called the 

 epiglottis (Gr. epi, upon) which opens and shuts like the lid of a 

 box. During breathing, speaking, &c., the glottis is open, the epi- 

 glottis being in the position shown 

 in fig. 75; but during the act of 

 swallowing, just at the moment when 

 food or drink is passing the top of 

 the larynx, the glottis is closed, thus 

 preventing any solid or liquid matter 

 from entering the trachea. 



We may now trace the course 

 taken by air during the act of inspi- 

 ration. If the mouth is closed, 

 the air inspired passes through the 

 nostrils and then along the lower 

 part of the nasal cavities. It next 

 enters the pharynx by means of two 

 openings called the posterior nares 

 or posterior nostrils, one of which 

 leads from each nasal cavity. The 

 air then passes down the pharynx, 

 through the glottis, to the larynx 

 and trachea, and thence into the 

 lungs. 



If the mouth is open during 

 ordinary breathing, some of the air 

 still passes through the nose, taking 

 That which enters the mouth takes 



Fig. 76. Section of the Face 

 and Neck, 



Showing the direction taken by the air 

 during breathing, &c. 



the course just described, 

 a shorter course, passing direct from the mouth into the pharynx ; 

 and then, joining the former current, goes with it through the 

 glottis, the larynx, and the trachea. 



The pharynx has seven passages communicating with it. Five 

 of these have already been mentioned. They are 



(a) The passages (posterior nares), leading from the nasal 

 cavities. 



(3) One communicating with the mouth. 



(f) The oesophagus. 



(a) The larynx. 



