DIGESTIVE SYSTEM. 433 



IV. DISSECTION OF THE DIQESTIVE SYSTEM. 



A. The Buccal Cavity. 



Open the mouth slightly ; cut through the cheek, parallel 

 to the jaios, for about half an inch on each side ; and turn 

 down the floor of the mouth so as to expose the cavity fully. 

 Note the following structures. 



1. The posterior narial apertures are a pair of long narrow 



apertures, lying side by side in the roof of the 

 mouth. The anterior two-thirds of their length is 

 hidden by a pair of prominent folds of the mucous 

 membrane of the palate. 



2. The aperture of the Eustachian tubes is a median open- 



ing, behind the posterior narial apertures. 



Pass a bristle through the aperture, and along the right 

 and left Eustachian tubes to the tympanic cavities. 



3. The tongue is triangular, ending in front in a sharp 



forwardly directed point ; and produced behind into 

 a pair of backwardly directed lobes, fringed with fine 

 horny processes. 



4. The glottis is an oval aperture, with tumid lips, in the 



floor of the mouth, just behind the tongue. 



5. The entrance to the oesophagus is large and wide, and 



situated behind the glottis. 



B. The Abdominal Viscera in situ. 



Lift up the hinder end of the sternuni, and cut through 

 its sides about midway between the dorsal and ventral surfaces. 

 Gut through the coracoids and clavicles about the middle of 

 their length. Detach the sternum with a scalpel from the 

 underlying parts, and remove it entirely. 



1. The falciform ligament is a median vertical sheet of 

 peritoneum, connecting the dorsal surface of the 

 sternum with the viscera : it is continuous in 



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