DIGESTIVE ORGANS. 219 
In the whales the tongue has little power of motion, but elsewhere 
in the mammals it is very mobile, reaching the extreme in the ant-eaters. 
This mobility is largely due to the extensive intrinsic musculature. 
The tongue is developed from the tuberculum impar, which furnishes 
the larger anterior part (fig. 221), the rest arising from the fleshy ridges 
abovethehyoid arch. In the adult the line between these parts is largely 
obliterated, but it lies near the line of circumvallate papille (p. 189) 
and the foramen cecum, a blind tube connected with the development 
of the thyreoid gland. Arising in this 
way from the tubercle and the lateral supra- 
hyoid parts, the tongue of the amphibia is 
Fic. 222. Fic. 223. 
Fic. 222.—Ventral and side views of tongue of Stenops gracilis, after Weber. 1, 
lateral margin of sublingua; m, plica mediana. 
Fic. 223.—Section through lyssa of late dog embryo, after Nussbaum. ¢, cartilage of 
lyssa, cl, capsule of lyssa; m, muscles of tongue; ml, longitudinal and transverse muscles 
of lyssa; s, septum of tongue. 
unrepresented in that of most mammals, unless it be in the sublingua, 
a fleshy fold developed beneath the functional tongue in the marsupials 
and lemurs (fig. 222). Traces of this are to be found in other mam- 
mals, even in man, as folds (plice fimbriatz) beneath the tongue. 
In some cases (Stenops) this sublingua is supported by a cartilage 
which is regarded as an entoglossal part. Others think that the 
tongue of the lower vertebrates is represented in the mammalian 
tongue and regard the lyssa as the os entoglossum. The lyssa is 
a vermiform structure of cartilage, muscle and connective tissue (fig. 
223) lying ventral to the septum of the tongue. 
The tongue varies considerably in shape in the different mammalian 
‘orders, but the differences are of little morphological importance. 
