258 Mammalia^ 



the lower jaw by the genio-liyo-glossi muscles, in front of 

 which the mucous membrane beneath the tip forms a fold 

 called the Frcenum Linguce. A little anterior to the fraenum 

 on either side are the openings of the ducts of the sub-max- 

 illary and sub-lingual glands. 



The upper surface or dorsum of the tongue is covered with 

 papillae of various form throughout its whole extent, except 

 in the neighbourhood of the epiglottis. Four varieties of 

 papillce are found, viz. (a) circiimvallate, i.e. papillae resting in 

 cup-like depressions of the mucous membrane ; these are found 

 only along the lateral margin of the gibbous portion of the 

 tongue ; (b) fungiform, i.e. larger processes of the mucous 

 membrane than the circum vallate, wider at the free end than 

 at the part fixed to the tongue ; these are more numerous 

 than the circumvallate, and are principally situated in the 

 middle of the dorsum ; (c) conical, i.e. small cones like white 

 specks, principally along the sides of the tongue ; and, lastly, 

 (d) filiform, i.e. hair-like processes of the epithelium, sloping 

 generally towards the back of the mouth ; these papillae cover 

 the anterior two-thirds of the tongue and vanish towards the 

 base. 



Behind the Tongue and in front of the orifice of the 

 Larynx is the leaf- shaped cartilage, termed the Epiglottis ; 

 which during respiration is placed vertically, but during de- 

 glutition takes a horizontal position so as to close the open- 

 ing of the Larynx and prevent food passing into it during its 

 passage through the Pharynx into the (Esophagus. 



The rounded eminences posterior to the Epiglottis, and on 

 which the Epiglottis rests when depressed backwards, are the 

 Arytenoid Cartilages. 



Dissection of the Larynx. The (Esophagus, which lies 

 above the Larynx and Trachea, should be now dissected away 

 from the Trachea, in order to enable the Student to expose 

 the internal arrangement of the Larynx by a longitudinal cut 



