PHARYNX 289 



always remains patent, and presents under all conditions very 

 much the same form. 



In its anterior boundary are the choanae, through which it 

 opens into the nasal cavities. The choantz are two oblong 

 orifices which slope from the base of the cranium downwards 

 and forwards to the posterior border of the hard palate. 

 Each is about 25 mm. (one inch) long and 12.5 mm. (half an 

 inch) wide, and it is separated from its fellow by the posterior 

 part of the septum nasi, which is formed by the posterior 

 border of the vomer. By looking through the choanse the 

 dissector will obtain a partial view of the lower two meatuses 

 of the nose and of the posterior ends of the middle and 

 inferior conchse. 



On each side wall of the naso-pharynx is seen the orifice 

 of the corresponding auditory tube, and posterior to it the 

 pharyngeal recess. The pharyngeal orifice of the auditory 

 tube lies immediately posterior to the lower part of the 

 corresponding choana, on a level with the posterior end of 

 the inferior concha of the same side. It is bounded above 

 and posteriorly by a prominent and rounded margin termed 

 the torus tubarius, which is altogether deficient below and 

 anteriorly. A fold of mucous membrane, termed the salpingo- 

 pharyngeal fold, descends, upon the side wall of the pharynx, 

 from the posterior lip of the orifice of the auditory tube. As 

 the fold is traced downwards it gradually disappears. 



The dissector should pass a Eustachian catheter through the nose into 

 the auditory tube. Hold the catheter with the point downwards. Pass it 

 backwards through the right nasal cavity, along the septum of the nose, to 

 the posterior wall of the pharynx. Pull it towards the palate till the bent end 

 of the catheter catches against the back of the hard palate. Turn the point 

 through a quarter of a circle to the right side of the head and it will enter 

 the right auditory tube. If it is desired to catheterise the left auditory tube 

 pass the catheter through the left nasal cavity, and in the final stage turn the 

 point to the left side. 



In the natural condition of parts there is a deep recess 

 on the side wall of the naso-pharynx immediately posterior 

 to the prominent posterior lip of the orifice of the auditory 

 tube. It is termed the pharyngeal recess. 



The roof and posterior wall of the naso-pharynx are not 

 marked off from one another. They form together a continuous 

 curved surface. The upper portion of the surface looks 

 downwards and may be regarded as the roof ; the lower portion, 

 which looks forwards, constitutes the posterior wall The roof 



VOL. Ill 19 



