DEGLUTITION. 203 



down the pharynx by the sides of the epiglottis ; and in that 

 case, liquids would almost certainly pass around the borders 

 in quantity sufficient to moisten the mucous membrane be- 

 low. It must be remembered, however, that the sensibility 

 of the air-passages is very unequal in different persons, and 

 that it may be considerably modified by education of the 

 parts. This should make us hesitate to accept the view 

 that, in gargling, the larynx receives a quantity of li- 

 quid, and that an alimentary bolus may be tolerated in the 

 trachea for many minutes without coughing. Though this 

 may be true in the person of Dr. Krishaber, common experi- 

 ence shows that it is not generally the case. 1 



To sum up the mechanism by which the opening of the 

 larynx is protected during the deglutition of solids and 

 liquids, we have only to carefully follow the articles as they 

 pass over the inclined plane formed by the back of the 

 tongue and the anterior and inferior part of the pharynx. 

 As the food is making this passage in obedience to the con- 

 traction of the muscles which carry the tongue backward, draw 

 up the larynx, and constrict the pharynx, the soft base of the 

 tongue and the upper part of the larynx are applied to each 

 other, with the epiglottis, which is now inclined backward, 

 between them ; at the same time, the glottis is closed, in part 

 by the action of the constrictor muscles attached to the sides 

 of the thyroid cartilages, and in part by the action of its in- 

 trinsic muscles. If the food be tolerably consistent and 



1 The note of M. H. Guinier mentions experiments on deglutition observed by 

 auto-laryngoscopy in which, by performing the act of swallowing slowly and imper- 

 fectly, so as not to close the pharynx, he was able to exhibit the phenomena to a 

 number of persons. He showed that the action of the epiglottis was not abso- 

 lutely necessary to protect the larynx during the passage of the alimentary bolus 

 from the pharynx to the O3sophagus, and that the passages could be protected by 

 simple closure of the vocal cords ; and that in gargling, the space above the superior 

 vocal cords was filled and the liquid agitated by the air as it was allowed to pass 

 slowly from the glottis. As regards the function of the epiglottis, it must be re- 

 membered that in these experiments, deglutition was not and could not be nor- 

 mal. The observations on gargling, however, seem very satisfactory. 



