MOVEMENTS OF THE ALIMENTARY CANAL DEGLUTITION. 129 



the mastication of food are supplied by the third branch of the Fifth pair, 

 which is well known to be a nerve of mixed endowments; but some, especially 

 those of the cheeks, are also supplied by the Facial nerve; and yet, if the 

 former he paralyzed, the latter cannot stimulate them to the necessary com- 

 bined actions. Hence we see that the movements are of an associated char- 

 acter, their due performance being dependent on the part of the nervous 

 centres from which the motor influence originates. If the Fifth pair, ou 

 the other hand, be uninjured, \vhilst the Portio dura is paralyzed, the move- 

 ments of mastication are performed without difficulty ; whilst those connected 

 in any way with the Respiratory function, or with Expression, are paralyzed. 

 If again, the sensory portion of the Fifth pair be paralyzed, the act of Mastica- 

 tion is very imperfectly performed, even though the motor power be not in the 

 least impaired; for the muscles cannot be made to perform the requisite as- 

 sociated movements without the guidance of sensations; so that the morsel 

 lodges between the teeth and the cheek, or beneath the tongue, and can with 

 difficulty be kept in the appropriate position. 



87. When the reduction of the food in the mouth has been sufficiently 

 accomplished it is carried into the Phari/n.r, and is thence propelled down 

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

 taken together constitute the act of Deyhilition. These movements were 

 first described in detail by Magendie ; but his account requires some modifi- 

 cation, through the more recent observations of Dzondi, 1 Budge, 2 Bidder, 3 

 Czermak, 4 Schuh, 5 and Moura. 6 The first stage in the process is the carry- 

 ing back of the food until it has passed the anterior palatine arch ; this is 

 effected by the contraction of the mylo-hyoid, and of the longitudinal and 

 transverse muscles of the tongue, which together render the tongue shorter 

 and thicker, pressing it against the roof of the mouth, whilst the stylo-glossi 

 draw it somewhat backward ; those movements are purely voluntary. The 

 second stage now commences, during which the entrance of food into the 

 nasal cavities and trachea is most jealously guarded against by certain reflex 

 actions, which have only been clearly recognized since the introduction of the 

 laryngoscope by Czermak. During this stage the tongue is carried still 

 farther backwards, the larynx rises, its orifice being covered by the epiglottis, 

 which is at the same time somewhat depressed, and placed horizontally, so 

 that its upper border touches the posterior wall of the pharynx. The cush- 

 ion at the base of the epiglottis becomes applied to the arytenoid cartilages, 

 and the vocal cords, both true and false, are closely approximated ; a triple 

 protection against the entrance of the food into the trachea being thus 

 afforded. Coincideutly with these movements, the lower border of the velum 

 palati becomes applied to the walls of the pharynx, and the muscles of the 

 posterior 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 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. Though some of these acts may be performed 

 voluntarily, the combination of the whole is automatic. 7 The third stage 



1 See Prof. Miiller's Elements of Physiology (translated by Dr. B;ily), p. 501. 



2 Phys., I860, p. 157. 3 Neue Beobachtungen, Dorpat, 1838. 

 4 The Laryngoscope, New Syd. Soc. Translation, 1861, vol. ix. 



6 On the Laryngoscope, Can'statt, 1858. 



6 Robin, Journal de 1'Anatomie, 1867. p. 157. 



7 The observation of Schuh (Canstatt, 1858) upon the movements of the soft pal- 

 ate during deglutition seem to show that this part is somewhat more active during 



