440 ELEMENTARY ANATOMY. [LESS. 



end they are mostly long and pointed, and are called conical 

 and filiform papillae. 



Scattered over the middle of the tongue are very red 

 papillae, ca\\Q&fungiform, because each is narrower at its 

 root than at its upper part. 



The third kind are the circumvallate papillae from eight to 

 fifteen in number arranged at the back of the tongue so as to 

 form the letter V, with the point of the V directed towards 

 the throat. Each of these is shaped like an inverted cone, of 

 which the apex is attached to the bottom of a cup-shaped 

 cavity, so that the papilla is surrounded by a circular furrow. 

 Man's tongue contains no osseous or cartilaginous struc- 

 ture. Its shape, degree of mobility, and extensibility are too 

 familiar to require notice. 



7. The tongue in Vertebrates generally presents a great 

 variety as to form and function, relative size, and denseness 

 of structure. 



It may be completely absent, as <?.-. in the Siluroids, where 

 even the glosso-hyal bone is absent. It may, as in most 

 Fishes, be almost destitute of muscular tissue, and very 

 slightly mobile, merely investing a glosso-hyal bone, and often 

 being furnished with teeth. 



The tongue may be apparently absent in Batrachians, as in 

 Pipa; or even in Reptiles, as in the Crocodile. It may be 

 long, pointed, and coated with a horny 

 sheath, with recurved processes towards 

 the apex, as in the Woodpecker. It 

 may be fixed in front and free behind 

 being protruded by eversion as in the 

 Frog. It may be very extensible, 

 thickened and somewhat cup-shaped 

 at the end, as in the Chameleon. It 

 may be exceedingly mobile and ex- 

 tensible, with its apex deeply cleft, as 



in Serpents. 



In man 's own class the tongue may 

 terioriy. likewise only form the floor of the 



mouth, as in the Dolphin. It may, as 



in the Dog and Mole, have on its under surface a longitudinal 

 fusiform, rather dense body, attached to the rest by cellular 

 tissue, and called the worm, or lytta. The coniral papillae 

 may be horny, and shaped like small claws, as in the Cat. 

 Fungiform papillae may be absent, as in the Horse and 

 Manatee. There may be but two circumvallate papillae, as 



G. 373. HEAD OF THE 



FKOG Phyllomedusa 



