THE DIGESTIVE SYSTEM. 



171 



also do their part in pushing the food along. As soon as 

 the food has passed over the epiglottis, the epiglottis rises 

 to its upright position, and the soft palate drops back to 

 its place, leaving the air passages again open. 



Breathing and Swallowing. It is to be observed that 

 the food tube and the air tube cross, and that the pharynx 

 is their crossing. As we are swallowing only a small 

 part of the time, the passageway naturally stands open to 

 the air ; and when we swallow, the parts are, by muscular 



Eustachian Tube 



- Soft Palate, Raised 



- Food 



.... Epiglottis. Down 



- Gullet, Open 



- Glottis, Closed 



Fig. 59. Diagram, showing the Positions of the Organs of the Mouth and 

 Throat during Swallowing. 



effort, temporarily adjusted for this work. There is a 

 spring switch (to borrow a term from the railway) which 

 keeps the track open for the air, which is all the time 

 passing ; but when the food comes along, the switch must 

 be held open for it until it has passed. 



Structure and Action of the Gullet. The gullet has 

 an outer muscular coat and an inner mucous coat. The 



