DEGLUTITION. 



109 



longitudinal layer of fibres the mass is slowly squeezed down to 

 the cardiac orifice of the stomach. The movements of the oeso- 

 phagus are essentially peristaltic in character, the peculiarities 

 of which form of motion will be discussed when speaking of the 

 intestinal movements. 



FIG. 52. 



Deep Muscles of Cheek, Pharynx, etc. (1) Orbicularis oris; (2) buc- 

 cinator; (3) superior, (4) middle, and (5) inferior constrictors of the 

 pharynx; (6) oesophagus; (7) styloid muscles cut across; (8,9, 10) mus- 

 cles attached to the hyoid bone (d) and thyroid cartilage (e). (Allen 

 Thomson.) 



The entire process of swallowing is a continuous series of co- 

 ordinated muscular acts, quite independent of gravitation, as may 

 be seen in animals drinking with their heads downwards. Al- 

 though all the complex sets of movements follow each other per- 



