ORAL CAVITY 



233 



of attachment is more extensive and embraces the anterior margin 

 of the tongue and part of the ventral surface as well. The sup- 

 porting skeleton (fig. 94) consists of the median portion (copula) 

 with usually two pairs of cornua, largely formed from the ventral 

 ends of the hyoid and first branchial arches (see p. 72). 



The reptilian tongue includes not only the parts found in the am- 

 phibia (the fold above the basihyal) , but also a median growth, the 

 tuberculum impar (fig. 247) , arising between the basihyal and the 

 lower jaw, and also a pair of lateral folds lying above the first visceral 

 » (mandibular) arch {Lacerta). With the development of these parts, 

 P the trigeminal nerve also suppUes the tongue, in addition to the hy- 

 poglossal and glossopharygeal of the lower 

 groups. In the turtles and crocodiles the 

 tongue lies on the floor of the mouth and 

 is not protrusible. In the squamata it 

 can be extended from the mouth, and in 

 snakes and many lizards there is a sheath 

 into which it is withdrawn. In many 

 snakes the tongue is two-pointed at the 

 tip; in the lizards its shape varies greatly, 

 the differences being used in classifying 

 these animalsy/ln the reptiles (fig. 246) 

 with retractile tongue the hyoid apparatus 

 extends into the tongue, its unpaired an- 

 I terior portion being called the OS entog- 

 *^*lo»6um (copula or basihyal), while the 



two cornua (usually hyoid and first fig. 246.— Hyoid apparatus of 

 branchial) afford attachment for the re- Itt^^U'f^r^^Xl^yit' 

 tractor muscles. In addition to the usual 



lingual nerve (glossopharyngeal) the tongue also receives a lingual 

 twig from the mandibular branch of the fifth nerve, y 



In birds the tongue has lost the lateral parts of the reptilian 

 tongue and with this the trigeminal branch. It contains no intrinsic 

 muscles. In its form it varies greatly, but usually it is slender and is 

 covered with retrorse horny papillae. Its skeleton is also reduced 

 (fig. in) and consists of an os entoglossum, bearing in front a pair of 

 elements (paraglossae) and on the sides a pair of cornua (first bran- 

 chials) and in the median line behind, a urohyal portion. This 

 skeleton has a marked development in the woodpeckers, where the 

 cornua curve around the base of the skull and over its dorsal side to 



