, 



nf tVio i, 



DEGLUTITION. 



107 



of the tongue with the hyoid bone is at the same time drawn up- 

 wards and forwards, 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. Immediately before 

 the morsel of food is grasped by the muscles of the fauces the 

 levator palati draws the soft palate upwards and backwards to 

 completely close the posterior openings of the nasal cavity, as is 

 shown by the fact that during the act of swallowing the pressure 



FIG. 50. 





^^V^BM^^^^^P 



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



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

 muscles of the larynx, which surround the rima glottidis like a 

 constrictor, firmly close that opening by approximating 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 thryo-epiglotti- 

 dean muscles. 



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 



