592 THE DIGESTIVE TRACT. 



the furrow of the circumvallate papillae. On the anterior portion 

 of the tongue mucous glands are found only along the lateral 

 border, which coalesce into a larger group at the apex of the 

 tongue. 



At the posterior portion of the mucosa of the tongue, where 

 papillae are not present, a varying number of nodular elevations 

 occur, which are lymph-ganglia, and have been erroneously 

 termed "follicular glands." They are accumulations of lymph- 

 tissue with numerous f ollicular formations, and in their centers 

 usually show a longitudinal cleft, in open communication 

 with the outer surface of the tongue. Stratified epithelium 

 directly covers the lymph-ganglion, the papillae being imperfectly 

 developed on the outer periphery of the ganglion and altogether 

 wanting within the cleft. Sometimes the fibrous connective 

 tissue produces a distinct capsule around the ganglion. Dif- 

 fused layers of lymph-tissue immediately above the muscle of the 

 tongue are also observed, especially in children. 



The muscle-fibers of the tongue are of the striped variety j 

 they interlace in different directions and produce a dense felt- 

 work, are attached to the fibrous septum in the longitudinal 

 median line of the tongue, and freely ramify upon approaching 

 the mucous layer, with which they blend. The perimysium con- 

 tains a varying number of fat- globules, chiefly in the posterior 

 portions of the tongue. 



The blood- and lymph-vessels are numerous. The latter, 

 according to Teichmann, produce two plexiform extensions, the 

 upper and finer of which lies close beneath the papillae, receiving 

 the usually single lymph-ramules from the filiform papillae and 

 the plexuses from the fungif orm and circumvallate papillae. Rich 

 plexuses of lymphatics surround the lymph-ganglia. 



(3) In the pharynx and oesophagus the structure of the mucosa 

 resembles that of the oral cavity i. e., it has small papillae, not 

 distinctly marked on the epithelial surface. The latter is strati- 

 fied and produces small acinous mucous glands, which are more 

 numerous in the throat than in the oesophagus. In the lower half 

 of the oesophagus they are absent, except in the portion immedi- 

 ately above the cardiac orifice of the stomach (Kolliker). The 

 stratified epithelial investment in the neighborhood of the choanae 

 blends with the ciliated columnar epithelia of the nasal cavities. 



The lymph-tissue is a widely spread formation in the mucosa 

 of the pharynx; besides, a large amount is stored up in the 

 two lymph-ganglia, the tonsils, which are situated in the niches 



