224 



CHORDATE ANATOMY 



dorsum of the tongue, and are distinguished by their reddish color and 

 their globular mushroom shape. They also bear taste-buds. No papillae 

 occur on the posterior and inferior surfaces of the tongue. (Fig. 211) 



Most of the mass of the tongue consists of striated muscle. In the 

 connective-tissue corium of the tongue, both mucus and serous glands are 

 abundant. The lingual tonsils lie on the posterior dorsum. 



Development of the Tongue. The apex and root of the tongue, which 

 develop from separate anlagen, remain throughout life divided by the 



EPIGLOTTIS. 

 'v . A^ 



FORAMEN 

 CAECUM \/ 





Fig. 211. — The dorsal surface of the tongue. The sulcus terminalis divides the 

 body or apex of the tongue from the root. The two regions have a different embryonic 

 origin. (Redrawn after Sobotta.) 



sulcus terminalis. The apex of the tongue is formed by the union of a 

 median tuberculum impar with the basal portions of the two halves of the 

 mandibular arch. (Fig. 212) The root of the tongue arises from por- 

 tions of the second, third and fourth visceral arches. The tongue muscles, 

 however, are not formed from those of the visceral arches, but from post- 

 occipital myotomes which send buds downward and forwards into the 

 tongue. 



History of the Tongue. None of the lower chordates has a tongue, 

 so that the vertebrate tongue seems to be an emergent organ like the 

 notochord. The so-called tongue of cyclostomes is a muscular piston 



