SECTION II. MOUTH AND PHARYNX 



Open the mouth of the frog as widely as possible and locate 

 the following structures, commencing with the roof. 



13. The lips are thin and fleshy. 



14. The maxillary teeth are on the mesial edge of the 

 upper jaw; they are fine, conical, and closely set. 

 Note their extent. 



15. The sulcus marginalis is a groove into which the 

 lower jaw fits closely. 



16. The vomerine teeth are in two groups at the ce- 

 phalic end of the roof. 



17. The posterior (internal nares) are lateral to the 

 vomerine teeth. Probe these from the external nares 

 (7) with a bristle. 



18. At the caudal end of the cavity close to the angle of 

 the jaws, locate the openings of the Eustachian 

 (auditory) tubes. 



19. The portion of the cavity into which these open is 

 the pharynx. 



20. The pharynx communicates with the digestive tract 

 by the oesophagus, a transverse slit in the mesial 

 line, between the Eustachian tubes. 



21. Cephalad to the oesophagus and on the ventral sur- 

 face of the pharynx is a cephalo-caudal slit, the 

 glottis, opening into the larynx (in reality, laryngeo- 

 trachea) (60). 



22. The glottis is surrounded by two prominences caused 

 by the arytenoid cartilages of the larynx. 



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