166 ; '. CONSTRICTORS OF THE PHARYNX. 



pharynx to the vertebral column. The saw is then to be applied 

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

 The vessels and loose structures should be removed from the prepa- 

 ration, and the pharynx stuffed with tow or wool for the purpose of 

 distending it, and rendering the muscles more easy of dissection. 

 The pharynx 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, from the cricoid 

 and the side of the thyroid cartilage. 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 lymphatic 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 to the 

 cricoid cartilage, it is in relation with the recurrent nerve ; and by 

 the upper border with the superior laryngeal nerve. 



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



The constrictor medius arises from the great cornu of the os hy- 

 oides, 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 

 superior. 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 con- 

 strictor, 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 membrane 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 muscu- 

 lar 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 pro- 

 cess which is deficient in muscular fibres, and it is overlapped in- 

 feriorly by the middle constrictor. Between the side of the pharynx 

 and the ramus of the lower jaw is a triangular interval, the maxillo- 

 pharyngeal space, which is bounded on the inner side by the supe- 



