180 THE ENGINES OF THE HUMAN BODY 



When a bolus reaches the lower end of the oesophagus 

 it sets a touch-button mechanism into operation, with 

 the result that the spindle engines of the sphincter are 

 thrown out of action ; the doorway is then open for the 

 passage of the bolus. On its entrance, the sphincter 

 again passes into action and remains so until the next 

 bolus arrives. Here, then, is a small but wonderful 

 machine — one which will remain on duty constantly for 

 seventy years or more save for those brief respites it 

 obtains during meal-times. 



As we watch the arrival of the spoonfuls of the bismuth- 

 laden test meal at the doorway to the stomach, we may 

 see one bolus follow another so quickly that the first has 

 not gained admission when the second arrives ; presently 

 a queue forms filling up the lower part of the oesophagus. 

 As long as the accumulation lasts the doorway to the 

 stomach is kept open. Very rarely does the " touch- 

 button " mechanism which controls the cardiac sphincter 

 go out of order, but when it does there is a serious 

 delay and accumulation of traffic in the lower end of 

 the oesophagus. The " touch-button " mechanism works 

 best with well-formed soft boluses of food ; tabloids or 

 solid bodies, when they reach the doorway to the stomach, 

 may fail to give the password that causes it to open. 

 Hence such bodies may remain at the entrance to the 

 stomach and give rise to strange and indefinite forms 

 of pain which the sufferer may find difficult to locate. 

 In other cases such arrested bodies give rise to hiccough. 



