THE ALIMENTARY CANAL. 233 



uous with the circular fibres of the oesophagus. The cranial 

 fibres may pass as far as the base of the sphenoid. 



Action. Constrictor of the pharynx. 



M. constrictor pharyngis medius (/). A thin sheet which 

 covers the middle part of the lateral surface of the pharynx. 



Origin. The ventral two pieces of the cranial horn and 

 the whole of the caudal horn of the hyoid. The fibres diverge, 

 passing dorsad. 



Insertion into the median dorsal raphe of the pharynx. 

 The cranial fibres are inserted into the base of the sphenoid 

 bone. The muscle covers part of the stylopharyngeus (/) and 

 the superior constrictor (Fig. 66, f, page 112) and is partly 

 covered by the glossopharyngeus (Fig. 96, z). 



Action. Constrictor of the pharynx. 



M. stylopharyngeus (/). 



Origin from the tip of the mastoid process of the temporal 

 bone and from the inner surface of the cartilaginous piece 

 between the tympanohyal and the stylohyal bones. The 

 parallel fibres form a flat band which passes ventrocaudad over 

 the outer surface of the constrictor superior. 



Insertion. The ventral fibres pass- beneath the middle con- 

 strictor (_/) at its cranial border and, continuing toward the 

 middle line of the pharynx, gradually lose themselves among 

 the fibres of the superior constrictor. The dorsal fibres pass 

 onto the outer surface of the middle constrictor and are lost 

 among its fibres. 



Action. Constrictor of the pharynx. 



M. constrictor pharyngis superior or pterygopharyngeus 

 (Fig. 66, f, page 112). A flat, triangular sheet beneath the 

 constrictor medius. 



Origin. The tip of the hamular process of the pterygoid 

 bone. The muscle passes caudad, the fibres diverging, and 

 dips beneath the cranial border of the constrictor medius. 



Insertion into the median dorsal raphe of the pharynx. 

 The dorsal fibres are inserted into the base of the sphenoid. 

 The ventral fibres pass lengthwise of the pharynx, closely 

 connected with those of the stylopharyngeus (Fig. 96, /), and 

 finally reach the level of the larynx. 



