SPLANCHNOLOGY 141 



horny sheath, does not form a part of the tubes, but ends in the 

 region of the point of the entoglossum. 



The top surface is covered by a thick stratum corneum, giving it 

 a rather horny surface. Glands occur in the posterior part of the- 

 tongue. 



While not so freely movable as in mammals, the tongues of birds 

 are very flexible. 



The Pharynx (Fig. 27). Location. The anterior part of the 

 pharynx joins with the mouth and the posterior part with the upper 

 portion of the esophagus and the superior larynx. The pharynx is 

 bounded anteriorly by the base of the tongue and by the posterior 

 edge of the hard palate. Posteriorly, it is marked by the entrance of 

 the esophagus and by a ridge of filiform papillae located on the 

 supero-posterior part of the larynx, called the palatal papillaries. 

 A few filiform papillae stud the roof. The pharynx communicates 

 anteriorly with the posterior nares and the mouth, and, posteriorly, 

 with the esophagus and the larynx. 



Shape. The pharynx is a musculo-membranous sac. 



Structure. The pharynx is lined with a mucous membrane 

 covered by squamous epithelium. The mucous membrane is thrown 

 into irregular folds. The bird has two Eustachian tubes. Pneu- 

 matic apertures conduct the air from the Eustachian tubes to the 

 pericranial diploe. 



In the posterior pharyngeal roof is situated the infundibular 

 crevice. 



Function. The function of the pharynx is to give passage for the 

 air from the posterior nares to the larynx, and to give passage for 

 the food from the mouth to the esophagus. 



Glands Adjacent to the Mouth and to the Pharynx. The 

 mucous membrane adjacent to the glottis and in the roof of 

 the mouth contains alveolar glands. The angular gland of the 

 mouth, located beneath the zygomatic arch, by some anatomists is 

 considered the rudimentary parotid gland. The sublingual glands, 

 or glandulae sublinguales, are well developed (Fig. 17, No. B, 4). 

 They form conical masses, with the apex directed anteriorly, and 

 occupy a portion of the intermaxillary space. Several ducts from 

 these glands open into the mouth cavity. In the palatine region 

 there are also located glands called the palatine glands, which open 

 by many stomata upon the surface. 



