THE DIGESTIVE SYSTEM 



223 



True salivary glands secreting enzymes are limited to mammals. 

 There seems no good reason to doubt, however, that the salivary glands of 

 mammals are derived from the oral glands of reptiles. Labial and buccal 

 glands become abundant in mammals, and possibly the parotid is an 

 enlarged buccal gland. In addition to the Ungual and palatine glands, 



TUBULAR GLANO> 



TUBULAR GLAND 



iCOMPOUND 

 TUBULAR GLAND 



Fig. 210. — Various types of digestive and endocrinal glands which develop from the 

 endodermal (mucous) lining of the alimentary canal. The endocrine glands are duct- 

 less. The digestive glands may be simple or compound, tubular or alveolar (acinous). 

 (Redrawn after Braus.) 



the sublingual and submaxillary glands are present; and in general, the 

 glands of man resemble those of other primates. 



The Tongue 



The tongue is a muscular organ of miscellaneous functions — digestive, 

 sensory, conversational — lying in the floor of the mouth cavity and 

 attached to the hyoid bone. It consists of an apex or body directed 

 towards the teeth of the lower jaw, a root or muscular attachment, a 

 dorsum divided by the sulcus terminalis into an anterior papillated por- 

 tion and a posterior tonsillar and glandular portion, and an inferior surface 

 below the apex. The sulcus terminahs is a V-shaped groove with the 

 apex of the V pointing backwards and marking the position of the foramen 

 coecum. See Fig. 211. 



The dorsum of the tongue anterior to the sulcus is covered with 

 numerous papillae which give the tongue its characteristic rough appear- 

 ance. Four kinds of papillae are distinguished, vallate, filiform, foliate, 

 and fungiform. The vallate papillae are the largest, and are distinguished 

 also by the deep depression or fossa which surrounds each of them. On 

 their sides they bear numerous taste-buds. Their number varies from six 

 to twelve, and they occur in a V-shaped row just in front of the sulcus 

 terminahs. Of the various forms of papillae on the tongue the filiform 

 papillae are the most numerous. Each filiform papilla is covered with 

 filamentous processes. Foliate papillae are three to eight parallel folds 

 on each side of the tongue. Like the vallate papillae, the fohate papillae 

 have taste-buds. The fungiform papillae are scattered over the entire 



