CONSTRICTOR MEDIUS. CONSTRICTOR SUPERIOR. 189 



styloid processes, and the base of the skull sawn through. The 

 vessels and loose structures should be removed from the preparation, 

 and the pharynx stuffed with tow or wool for the purpose of distend- 

 ing it, and rendering the muscles more easy of dissection. The pha- 

 rynx is invested by a proper pharyngeal fascia. 



The CONSTRICTOR INFERIOR, the thickest of the three muscles of 

 this class, arises from the upper rings of the trachea, the cricoid car- 

 tilage, and the oblique line of the thyroid. Its fibres spread out and 

 are inserted into the fibrous raphe of the middle of the pharynx, the 

 inferior fibres being almost horizontal, and the superior oblique, and 

 overlapping the middle constrictor. 



Relations. By its external surface with the anterior surface of the 

 vertebral column, the longus colli, the sheath of the common carotid 

 artery, the sterno-thyroid muscle, the thyroid gland, and some lymph- 

 atic glands. By its internal surface with the middle constrictor, the 

 stylo-pharyngeus, the palato-pharyngeus, and the mucous membrane 

 of the pharynx. By its lower border, near the cricoid cartilage, it 

 is in relation with the recurrent nerve ; and by the upper border with 

 the superior laryngeal nerve. The fibres of origin of this muscle are 

 blended with those of the sterno-hyoid, sterno-thyroid, and crico- 

 thyroid, and it frequently forms a tendinous arch across the latter. 



This muscle must be removed before the next can be examined. 



The CONSTRICTOR MEDIUS arises from the great cornu of the os 

 hyoides, from the lesser cornu, and from the stylo-hyoidean ligament. 

 It radiates from its origin upon the side of the pharynx, the lower 

 fibres descending and being overlapped by the constrictor inferior, 

 and the upper fibres ascending so as to cover in the constrictor supe- 

 rior. It is inserted into the raphe and by a fibrous aponeurosis into 

 the basilar process of the occipital bone. 



Relations. By its external surface with the vertebral column, the 

 longus colli, rectus anticus major, the carotid vessels, inferior constric- 

 tor, hyo-glossus muscle, lingual artery, pharyngeal plexus of nerves, 

 and some lymphatic glands. By its internal surface, with the superior 

 constrictor, stylo-pharyngeus, palato-pharyngeus, and mucous mem- 

 brane of the pharynx. 



The upper portion of this muscle must be turned down, to bring 

 the whole of the superior constrictor into view ; in so doing, the 

 stylo-pharyngeus muscle will be seen passing beneath its upper 

 border. 



The CONSTRICTOR SUPERIOR is a thin and quadrilateral plane of 

 muscular fibres arising from the extremity of the molar ridge of the 

 lower jaw, from the ptery go -maxillary ligament, and from the lower 

 half of the internal pterygoid plate, and inserted into the raphe and 

 basilar process of the occipital bone. Its superior fibres are arched 

 and leave an interval between its upper border and the basilar process 

 which is deficient in muscular fibres, and it is overlapped inferiorly by 

 the middle constrictor. Between the side of the pharynx and the 

 ramus of the lower jaw is a triangular interval, the maxillo pliaryngeal 



