CHAPTER VI 



DIGESTION OF FOOD: THE (ESOPHAGUS AND STOMACH 



Connecting the pharynx and the stomach cavities is a 

 tube about ten inches in length called the oesophagus. 

 This tube is lined throughout by an epithelium secreting 

 mucus, and for this reason it offers little resistance to the 

 swallowing of food. 



Swallowing. After food has been masticated and moist- 

 ened by the saliva it is rolled up by the tongue into a smooth, 

 moist mass. The tongue is then pushed up against the roof 

 of the mouth, first at its tip, and then moved backwards; 

 the food ball, being moist, slips along easily and is pushed 

 through the opening into the throat. Up to this point the 

 process of eating has been under one's control and could have 

 been stopped at any moment; but as soon as food goes into 

 the throat it passes beyond voluntary management. If one 

 should discover at this moment that the food contained 

 poison he could not refrain from swallowing it, for from this 

 point the action is involuntary, i.e. cannot be governed by 

 one's will power. 



"How can a man standing on his head drink water, or a 

 cow drink out of a brook when her head is so much lower 

 than her stomach?" This question is easily answered as 

 soon as we understand the action of the oesophagus. Two 

 coats of muscle are found in the wall of the tube; next to 

 the lining is a layer of muscle going around it, and outside 

 this is a layer running lengthwise. By the combined action 

 of these a " swallow," or bolus, of food is pushed downward, 

 the muscles in front of the food mass continually letting the 



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