MOVEMENTS OP THE ALIMENTARY CANAL. DEGLUTITION. 401 



425. When the reduction of the food in the mouth has been sufficiently ac- 

 complished, it is carried into the Pharynx, and thence propelled down the 



Fig. 117. 



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 cricoid cartilage ; 11, the trachea, covered by its lining membrane ; 12, section of 

 sternum ; 13, inside of the upper portion of the thorax ; 14, genio-hyoglossus muscle ; 15, its origin ; 16, 17, 

 the fan-like expansion of the fibres of this muscle ; 18, superficial linguae muscle ; 19, verticalis linguae mus- 

 cle; 20, genio-hyoideus muscle; 21, mylo-hyoideus muscle; 22, anterior belly of digastricus; 23, section of 

 platysma myoides ; 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 uvulae muscle ; 30, stylo pharyn- 

 geus ; 31, constrictor pharyngis superior ; 32, constrictor pharyngis medius ; 33, insertion of stylo-pharyngeus ; 

 34, constrictor pharyngis inferior ; 35, 36, 37, muscular coat of oesophagus ; 38, thyreo-arytenoid muscle and liga- 

 ments, and above is the ventricle of Galen ; 39, section of arytenoid cartilage ; 40, border of sterno-hyoideus. 



oesophagus into the stomach, by a set of associated movements, which, taken 

 together, constitute the act of Deglutition. These movements were first de- 

 scribed in detail by Magendie; but his account requires some modification, 

 through the more recent observations of Dzondi. 1 The first stage in the pro- 

 cess is the carrying back of the food until it has passed the anterior palatine 

 arch; this, which is effected by the approximation of the tongue and the palate, 

 is a purely voluntary movement. 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 ante- 

 rior palatine arch contract after the morsel has passed it, and assist its passage 

 backwards; these, with the tongue, cut off completely the communication be- 

 tween the fauces and the mouth. At the same time, the muscles of the poste- 

 rior palatine arch contract 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; and to the cleft between the 



1 See Prof. Midler's " Elements of Physiology" (translated by Dr. Baly), p. 501. 

 26 



