108 OUR BODIES AND HOW WE LIVE 



and the liver secretes the bile. Sweat is an excretion thrown 

 off from the body by the sweat glands. 

 Excretion will be described in Chapter IX. 



153. How Food is swallowed. The food is now ready to 

 be swallowed. The soft, moist mass is carried backwards 

 by the tongue and the muscles of the mouth into the 

 funnel-shaped part above the gullet, called the pharynx. 

 The soft palate moves upwards and backwards, so as to 

 prevent the food from passing into the nose 1 (Fig. 69). 



Now, besides the opening from the pharynx into the 

 gullet, there is also one into the windpipe. To prevent 

 the food from getting into this opening and choking us, 

 the top of the windpipe is protected by a little lid, a kind 

 of trapdoor, called the epiglottis (Figs. 101 and 174). 



When we swallow, the tongue, raised and pushed back- 

 wards, shuts this little lid ; and thus a bridge is made, over 

 which the food passes downwards into and through the 

 gullet, and thence into the stomach. 



Sometimes, however, a morsel of food "goes the wrong 

 way," that is, is drawn into the opening of the windpipe, 

 or down into the air tubes, and then violent coughing 

 follows : by this means it may be brought up again. If the 

 substance is hard and large, like a boot button, an orange 

 seed, or a peanut, a person, especially a child, may be choked 

 to death. 



Experiment 32. Open the mouth wide ; press down the back of 

 the tongue gently with the handle of a teaspoon. With the aid of 

 strong sunlight and a hand mirror the epiglottis may be seen. 



1 After an attack of diphtheria the parts of the throat are sometimes 

 partially paralyzed. The soft palate is not able to shut off this passage into 

 the nose; as a result, milk and other food often come up through the nose. 



