DEGLUTITION. 



117 



While the closure of the nasal and pulmonary air passages is 

 going on, the bolus has passed out of the cavity of the mouth and 

 has been caught by the palato-glossal and palato-pharyugeal 

 muscles which force it into the pharynx, and at the same time 

 close the isthmus faucium behind the descending morsel. The 



FIG. 51. 



12 



Muscles of Tongue and Pharynx. 1, 2, 3, Muscles from styloid process (6) to the 

 tongue, hyoid bone (d) and pharynx respectively ; 4, 5, 6, 7, 8, muscles of tongue; 9, 10, 

 11, constrictors of pharynx; 12, oesophagus; 13 is placed on larynx (e). (Allen Thomson.) 



stylo-pharyngeus and the pharyngeal constrictors now grasp the 

 bolus spasmodically, and the latter contract in rapid succession, 

 moving the bolus onward, and drawing themselves over it, pass 

 it on to the oesophagus, where, by a progressing ring-like con- 

 traction of the circular muscles and a simultaneous shortening 



