DEGLUTITION. 



55 



The benefit to digestion as a whole of a large secretion of sa- 

 liva, brought about by persistent chewing, has been assumed by 

 some to be much greater than it really is, and there has existed, 

 and indeed may still exist, a school of faddists who, by deliber- 

 ately chewing far beyond the necessary time, imagine themselves 

 to thrive better on less food than those who occupy their time 

 with other more profitable pursuits. 



Deglutition or Swallowing. After being masticated the food 

 is rolled up by the tongue acting against the palate into a bolus, 

 and this, after being lubricated by saliva, is moved, by elevation 



Fig. 4. The changes which take place in the position of the root of the 

 tongue, the soft palate, the epiglottis and the larynx during the second stage 

 of swallowing. The thick dotted line indicates the position during swal- 

 lowing. 



of the front of the tongue, towards the back of the mouth. This 

 constitutes the first stage of swallowing, and is, so far, a volun- 

 tary act. About this time a slight inspiratory contraction of the 

 diaphragm occurs the so-called respiration of swallowing and 

 the mylohyoid (the muscles of the floor of the mouth) quickly 

 contracts with the consequence that the bolus passes between the 



