116 MANUAL OF PHYSIOLOGY. 



pressed against the hard palate, and by the successive elevations 

 of the different parts of the dorsum of the tongue the bolus is 

 gradually pushed backward toward the isthmus of the fauces. 

 The root of the tongue with the hyoid bone is at the same time 

 drawn upward and forward, so that the bolus easily slips down 

 along the retreating slope leading from the mouth cavity, and 

 gets within the reach of the constrictors of the fauces. Imme- 

 diately before the morsel of food is grasped by the muscles of 

 the fauces the levator palati draws the soft palate upward and 

 backward to completely close the posterior openings of the nasal 



FIG. 50. 



The Pterygoid Muscles seen from without after removal of the superficial parts, the 

 temporal muscle, the zygomatic arch, and a portion of the lower jaw and naasseter. 

 (1) External, (2) Internal pterygoid muscle. 



cavity, as is shown by the fact that during the act of swallowing 

 the pressure in the nasal cavity is raised. At the same moment 

 the intrinsic muscles of the larynx, which surround the rima glot- 

 tidis like a constrictor, firmly close that opening by approximat- 

 ing the cords and arytenoid cartilages. The entire larynx is at 

 the same time drawn up behind the hyoid bone by the thyro- 

 hyoid muscle. The rima glottidis is thus tucked in under the 

 cushion 'of the epiglottis, while the leaf of the epiglottis is pulled 

 down over the larynx by the oblique aryteno-epiglottidean and 

 thyro-epiglottidean muscles. 



