66 TOPOGRAPHICAL ANATOMY OF THE 



arise from the lateral surface of the arch of the cricoid cartilage of the 

 larynx, and are inserted partly into the pharyngeal raphe and partly 

 into the linear tendon between this and the preceding muscle. 



The four muscles just described are all constrictors of the pharynx. 



Dissection. — Reflect the clioiidro-, thyro- and cric()-pliarvnf,'eal muscles. 

 Do this by cutting througli them close to their origins. This method 

 removes the danger of injury to the deeper part of the wall of the 

 pharynx. 



M. PALATOPHARYNGEUS. — The origin of the palato-pharyngeal 

 muscle from the border of the palatine and pterygoid bones cannot be 

 properly displayed until the soft palate is dissected. A few fibres 

 spring from the wall of the most anterior part of the auditory tube. 

 The muscle itself will be found running along the lateral wall of the 

 pharynx, to end partly in the pharyngeal raphe and partly on the 

 anterior border of the lamina of the thyroid cartilage. 



M. PTERYGOPHARYNGEUS. — The pterygo-pharyngeal muscle is thin 

 but moderately broad and triangular, and is not very definitely separated 

 from the palato-pharyngeus. Its origin is from the pterygoid bone, 

 whence it sweeps round the lateral wall of the pharynx to join its fellow 

 in the pharyngeal raphe. 



M. STYLOPHARYNGEUS. — The stylo-pharyngeal is a band-like muscle 

 that arises from the upper third of the medial surface of the great cornu 

 of the hyoid bone, passes between the palato- and pterygo-pharyngeal 

 muscles, and ends in the pharyngeal wall. 



Dissection. — Clean up the tenth, eleventh and twelfth cerebral nerves 

 as close to the base of tlie skull as possible. It is not, as yet, convenient 

 to reveal the foramina by which they leave the cranium, but their 

 approximate position may be determined. 



N. VAGUS. — The vagus or tenth cerebral nerve leaves the cranium 

 by the jugular foramen in company Avith the glosso-pharyngeal and 

 a,ccessory nerves. For a variable distance the vagus and accessor}^ 

 nerves are included in a common fibrous sheath. 



The vagus runs downwards and backwards, over the wall of the 

 diverticulum of the auditory (Eustachian) tube, to the termination of 

 the common carotid artery, where it meets the sympathetic trunk. 

 From this point onwards the two nerves, enclosed in the same sheath, 

 have been examined in the neck where they follow the dorsal border of 

 the common carotid artery (page 6). 



From the part of the vagus that is now under examination arise the 

 pharyngeal ramus and the cranial laryngeal nerve. 



(1) The ramus pharyngeus runs downwards and forwards over the 



