DIGESTIVE ORGANS. 217 
The Tongue. 
The tongue as it occurs in its more primitive condition in the fishes 
is merely a fleshy fold developed from the floor of the mouth between the 
hyoid and mandibular arches, the hyoid frequently extending into and 
supporting it. It is incapable of motion, except as moved by the sup- 
porting skeleton, for it lacks intrinsic muscles. It is sensory, having 
both tactile and gustatory functions. It is often papillose, and in a 
few teleosts it bears teeth (p. 209). 
The tongue in the cyclostomes is considerably different. Here it 
is thick and fleshy and is supported by a cartilaginous skeleton (p. 75) 
and is moved by appropriate protractor and retractor muscles at the 
base, developed from the postotic myotomes and innervated by the 
hypoglossal nerve. With its terminal armament of epidermal teeth 
it serves as the boring organ with which the myxinoids obtain entrance 
into their prey, while in the lampreys it serves as a rasping organ and 
also as part of the sucking apparatus. 
In the amphibia there is a greater range of structure. In a few 
anura (aglossa) the tongue is practically absent; in the perennibranchs 
it is scarcely more advanced than in the fishes, but elsewhere it contains 
intrinsic muscles.and is extremely mobile. It consists of a small basal 
portion corresponding to the tongue of the fish, to which is added a 
large glandular part arising between the copula and the lower jaw. 
This secretes the slime, so useful in capturing the prey. In the anura 
the tongue is attached at the margin of the jaw, its free end, when at 
rest, being folded back on the floor of the mouth. In urodeles the base 
of attachment is more extensive and embraces the anterior margin of 
the tongue and part of the ventral surface as well. The supporting 
skeleton (fig. 85) 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. 64). 
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, arising between the basihyal and the lower jaw, 
and also a pair of lateral folds lying above the first visceral arch 
(Lacerta). In the turtles and crocodiles the tongue lies on the floor 
of the mouth and isnot 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which it is withdrawn.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 
