CHAP. XXIII.] DEGLUTITION. 187 



The soft palate contains a thick layer of glands under its mucous 

 membrane, in front of its muscles ; and great numbers are situated 

 about the upper orifice of the larynx and on the general surface of 

 the pharynx. The tonsils are large and somewhat peculiar glands 

 projecting between the arches of the palate. They open by several 

 distinct orifices, which lead into cells, around which the secretory 

 structure is arranged. They are very vascular organs, and evidently 

 placed where they are to lubricate the food in its passage from the 

 mouth. It is not, however, known with accuracy what is the 

 nature or composition of the secretion they furnish ; but it is, pro- 

 bably, little besides simple mucus. That it is not identical with 

 the saliva may be inferred from the difference in structure of the 

 glands, and from the tonsils being liable to inflammation and sup- 

 puration, as well as to strumous enlargement, while the salivary 

 glands are seldom or never affected in the same way. 



The food, when sufficiently comminuted and mingled with saliva 

 in the mouth, and collected in the hollow of the tongue, is thrown 

 into the alimentary pharynx by the tongue being pressed upwards 

 against the roof of the mouth, this movement beginning at the 

 tip, and ending near the base. The division of the pharynx which 

 is to receive it is dilated as the food enters, by the advance and 

 elevation of the larynx, and by the yielding of its sides and posterior 

 wall, while the communication with the respiratory compartment 

 above is effectually closed by the coming together of the posterior 

 pillars of the fauces, by the contraction of the palato-pharyngeal 

 and upper constrictor muscles. The base of the tongue is now 

 forced backwards and upwards, so that the pellet is pressed between 

 it and the soft palate with its posterior pillars now in contact, and 

 is thereby carried downwards and backwards into that portion of 

 the cavity which lies behind the larynx. It crosses over the glottis 

 without entering it, because while the larynx is advanced the base 

 of the tongue presses back the epiglottis, and so covers the orifice ; 

 this movement of the epiglottis being assisted by the small aryteno- 

 epiglottidean muscular fibres, and by the very course of the food 

 itself; but it is abundantly proved, that even without an epiglottis 

 the glottis would for the most part be so closed by sudden spasm of 

 its constrictors, as to prevent any alimentary matters from falling 

 into the larynx. In the act of vomiting, where the matters pass in 

 the contrary direction, it is probable that the glottis is partly pro- 

 tected by the backward position of the tongue and epiglottis, and 

 partly by this conservative contraction of the arytenoid muscles in 

 answer to the mechanical stimulus of the food on the mucous mem- 



