338 OF DIGESTION AND NUTRITIVE ABSORPTION. 



[Fig. 81. 



A view of the Muscles of the Tongue, Palate. Larynx and Pharynx as well as the position of the upper 

 portion of the (Esophagus, as shown by a vertical section of the head; 1, 1, the vertical section of the head; 

 2, points to the spinal canal ; 3, section of the hard palate ; 4, inferior spongy bone ; 5. middle spongy bone ; 

 6, orifice of the right nostril ; 7, section of the inferior maxilla ; 8, section of the os hyoides ; 9, section of 

 the epiglottis; 10, section of the ericoid cartilage; 11, the trachea, covered by its lining membrane; 12, 

 section of sternum; 13, inside of the upper portion of the thorax; 14, genio-hyo-glossus muscle; 15, its 

 origin; 16, 17, the fan-like expansion of the fibres of this muscle; 18, superficialis linguae muscle; 19, ver- 

 ticales linguse muscle; 20, genio-hyoideus muscle; 21, mylo-hyoideus muscle; 22, anterior belly of digas- 

 tricus ; 23, section of platysma myodes ; 24, levator menti ; 25. orbicularis oris ; 26, orifice of Eustachian 

 tube; 27, levator palati; 28, internal pterygoid; 29, section of velum pendulum palati, and azygos uvulse 

 muscle; 30, stylo-pharyngeus; 31, constrictor pharyngis superior; 32, constrictor pharyngis medius; 33, 

 insertion stylo-pharyngeus; 34, constrictor pharyngis inferior; 35, 36, 37, muscular coat of oesophagus; 38> 

 thyreo-arytenoid muscle and ligaments, and above is the ventricle of Galen; 39, section of arytenoid carti- 

 lage ; 40, border of sterno-hyoideus.] 



ment. In the second stage, the tongue is carried still further backwards, and 

 the larynx is drawn forwards under its root, so that the epiglottis is pressed 

 down over the rima glottidis. The muscles of the anterior palatine arch con- 

 tract after the morsel has passed it, and assist its passage backwards ; these, 

 with the tongue, cut off completely the communication between the fauces and 

 the mouth. At the same time, the muscles of the posterior palatine arch con- 

 tract in such a manner as to cause the sides of the arch to approach each other 

 like a pair of curtains ; so that the passage from the fauces into the posterior 

 nares is nearly closed by them ; to the cleft between the approximated sides, 

 the uvula is applied like a valve. A sort of inclined plane, directed obliquely 

 downwards and backwards, is thus formed; and the morsel slides along it into 

 the pharynx, which is brought up to receive it. Some of these acts may be 

 performed voluntarily ; but the combination of the whole is instinctive. The 

 third stage of the process, the propulsion of the food down the oesophagus, 

 then commences. This is accomplished in the upper part by means of the 

 constrictors of the pharynx ; and in the lower by the muscular coat of the oeso- 

 phagus itself. When the morsels are small, and are mixed with much fluid, 

 the undulating movements from above downwards succeed each other very 



