TONGUE 



253 



Fishes is not capable of movement apart from the visceral 

 skeleton, and is wanting in a proper musculature. It is provided 

 with papillae and serves only as a tactile organ, or, when provided 

 with teeth {e.g., certain Teleostei, Fig. 60), as a prehensile organ 

 also. 



In Dipnoans the tongue is not more highly differentiated 

 than in many Fishes. 



Amphibians. — In the Perennibranchiata {e.g., Proteus") there 

 is a little advance on the condition seen in Fishes, but in all other 

 Amphibia except the Aglossa (Pipa and Xenopus), in which it has 

 become degenerated, the tongue reaches a higher stage, owing to 

 the development of definite muscles which render an independent 

 movement of the organ possible, 

 as well as of glands. The tongue, 

 moreover, is relatively larger, 

 and the numerous papillae render 

 the surface velvet-like. Its 

 mobility varies greatly in the 

 different forms. It is usually 

 attached only by the anterior 

 end or by a portion of its ventral 

 surface (Fig. 202) : in other cases 

 it is free all round, and in 

 Spelerpes (Fig. 203) is capable 

 of being extended far out of the 



mouth by means of a complicated mechanism, similar 

 which occurs in the Chameleon amongst Reptiles. 



Fig. 202. — Figure showing the Tongue 

 OF the Frog in Three Difpebent 

 Positions. 



to that 



Fig. 203.— Head oe SpeUrpes fiiscua, with the Tongue Extended. 



Reptiles. — In most Reptiles the tongue is usually freely 

 moveable, but its form and relative size varies greatly ^ (Fig. 

 204, A to e). It is provided with numerous sensory organs, 

 but no glands are present in the tongue itself It is least mobile 

 in Chelonians and Crocodiles : in Snakes and many Lizards it is 

 forked at the apex, and in the Chameleon it is protrusible, as in 

 Spelerpes. 



Birds. — The tongue of Birds is usually poorly provided with 

 muscles. It possesses a horny covering, usually provided with 

 papillae and pointed, recurved processes; it may, as in many 



1 Thus in Lizards the tongiie is used for classificatory purposes ( VermUinguia, 

 Cras-iilinguia, Brevilinguia, Fissilinguia). 



