262 THE DIGESTIVE ORGANS. 



would appear, situated in the otic ganglia. The nerve-ending in 

 the smaller glands of the mouth is similar to that given for the 

 salivary glands, as has been shown by Retzius and other observers. 

 It is very probable that the cell-bodies of the sympathetic neu- 

 rones, the neuraxes of which innervate the glands of the tongue, are 

 situated in the small sympathetic ganglia found on the lingual 

 branches of the glossopharyngeal and lingual nerves. 



B. THE PHARYNX AND ESOPHAGUS. 



Pharynx. The epithelium of the pharynx is of the stratified 

 squamous variety, and also contains prickle cells and keratohyalin. 

 (See Skin.) A stratified ciliated epithelium is present only in the 

 fornix in the region of the posterior nares. The area covered by 

 this type of epithelium is more extensive in the fetus and new-born, 

 and extends over the whole nasopharyngcal vault. In the human 

 embryo the superficial epithelial cells of the esophagus possess cilia 

 up to the thirty-second week (Neumann, 76). The papillae of the 

 mucosa are loosely arranged and are in the form of slender cones. 

 The mucosa of the pharynx contains diffuse adenoid tissue rich in 

 cells \vhich in some places forms accessory tonsils (vid. p. 251); 

 it is bounded externally by a well -developed layer of elastic fibers 

 which occupies the same relative position as does the muscularis 

 mucosae in the esophagus. External to this elastic layer, there is 

 found a muscular coat consisting of striated muscle-fibers. 



Esophagus. The esophagus is lined by a stratified pavement 

 epithelium, which rests on a papillated mucosa, consisting of fibrous 

 tissue which contains few elastic fibers and is bounded externally 

 by a muscularis mucosae, the majority of the cells of which show 

 a longitudinal arrangement. External to the muscularis mucosae 

 there is found a well-developed submucosa, consisting of loosely 

 woven fibre-elastic connective tissue. Outside of the submucosa 

 there is found a muscular layer, consisting of an inner circular and 

 an outer longitudinal layer. These muscular layers consist in the 

 upper half of the esophagus mainly of striated muscle-fibers, while 

 in the lower half they consist almost wholly of nonstriated muscular 

 tissue. There is, however, no sharply defined line of demarcation 

 between the two types of muscular tissue, as the fibers of the 

 unstriped variety penetrate for some distance upward into the 

 substance of the striated muscle, giving the tissue here a mixed 

 character. 



The esophagus contains two varieties of glands: (i) Mucous 

 glands of the type of branched tubulo-alveolar glands. The secret- 

 ing portions of these glands are situated in the submucosa, while 

 the ducts pass through the muscularis mucosae to the surface. 

 The secreting tubules and alveoli are lined by mucous cells ; demi- 

 lunes are absent. The ducts, which often show cystic dilations, 



