194: DIGESTION. 



Protection of the Opening of the Larynx, and Uses of 

 the Epiglottis in Deglutition. The entrance of the smallest 

 quantity of solid or liquid foreign matter into the larynx 

 produces violent and distressing cough. This accident is of 

 not infrequent occurrence, especially when an act of inspira- 

 tion is inadvertently performed while solids or liquids are in 

 the pharynx. During inspiration, the glottis is widely opened, 

 and at that time only can a substance of any considerable size 

 find its way into the respiratory passages. Respiration is in- 

 terrupted, however, during each and every act of deglutition ; 

 and there can, therefore, be hardly any tendency at that time 

 to the entrance of foreign substances into the larynx. During 

 a regular act of swallowing, nothing can find its way into 

 the respiratory passages, so complete is the protection of the 

 larynx during the period when the food passes through the 

 pharynx into the oesophagus. 



The situation of the epiglottis has naturally led physiolo- 

 gists to attribute to it great importance in preventing the 

 entrance of particles of food and liquids into the larynx. It 

 will be remembered that this cartilaginous leaf-like process 

 is attached to the anterior portion of the larynx, and is 

 usually erect, lying against the base of the tongue. In the 

 movements of the tongue and larynx incident to deglutition, 

 the epiglottis is necessarily applied to the superior face of 

 the larynx so as to close the opening. Although, during deg- 

 lutition, the glottis is covered in this way, it is necessary to 

 study closely all the conditions which are involved, and ascer- 

 tain what is the actual value of each of the various means by 

 which entrance of foreign bodies into the air-passages is 

 prevented; for this protection is accomplished by several 

 distinct provisions. 



It is evident from the anatomy of the parts and the 

 necessary results of the contractions of the muscles of deglu- 

 tition, that while the food is passing through the pharynx, 

 the larynx, by its elevation, passes under the tongue as it 

 moves backward, and the soft base of this organ is, as it 



