118 



MANUAL OF PHYSIOLOGY. 



of the longitudinal layer of fibres the mass is slowly squeezed 

 down to the cardiac orifice of the stomach. The movements of 

 the O3sophagus are essentially peristaltic in character, the pecu- 

 liarities of which form of motion will be discussed when speak- 

 ing of the intestinal movements. 



FJG. 52. 



Deep Muscles of Cheek, Pharynx, etc. (1) Orbicularis oris ; (2) buccinator ; (3) superior, 

 (4) middle, and (5) inferior constrictors of the pharynx; (6) oesophagus; (7) styloid 

 muscles cut across; (8, 9, 10) muscles attached to the hyoid bone (d) and thyroid cartil- 

 age (e). (Allen Thomson.) 



The entire process of swallowing is a continuous series of 

 coordinated muscular acts, quite independent of gravitation, as 

 may be seen in animals drinking with their heads downward. 

 Although all the complex sets of movements follow each other 

 perfectly, evenly and without any check or pause, the act of 



