THE SALIVARY GLANDS THE (ESOPHAGUS 451 



THE SALIVARY GLANDS 



The parotid gland is smaller and denser in texture than that of the horse, and 

 is hght red-brown in color; its average weight is about four ounces (ca. 115 g.). 

 It has somewhat the form of a very narrow long triangle, and lies chiefly on the ' 

 posterior part of the masseter muscle. The dorsal part is wide and thick; its 

 anterior border partly covers a large parotid lymph gland. The small ventral end 

 is bent forward and fits into the angle of union of the jugular and external maxillary 

 veins; it lies on the mandibular gland. The parotid duct leaves the ventral part 

 of the deep face; in its course it resembles that of the horse, but it pierces the cheek 

 opposite the fifth upper cheek tooth. 



The mandibular gland is larger than the parotid, and is pale yellow in color; 

 its average weight is about five ounces (ca. 140 g.) . It is covered to a small extent 

 by the parotid. Its general form resembles that of the horse, but its ventral end 

 is large and rounded, and is separated by a small interval only from the gland of 

 the other side (Fig. 302). This part can be distinctly felt in the living animal, and 

 is related laterally to a large lymph gland. The duct leaves the middle of the 

 concave border of the gland, crosses the stylohyoideus and the intermediate ten- 

 don of the digastricus, and is then disposed as in the horse. 



The sublingual gland consists of two parts. The dorsal part (Glandula sub- 

 lingualis parvicanalaris) is long, thin, and pale yellow in color. It extends from the 

 anterior pillar of the soft palate about to the symphysis of the mandible. It has 

 numerous small tortuous ducts (Ductus sublinguales minores) , which open between 

 the papiUae under the side of the tongue. The ventral part (Glandula sublingualis 

 grandicanalaris) is shorter and thicker, and lies ventral to the anterior portion of 

 the dorsal part; it is salmon pink in color. It has a single duct (Ductus sublin- 

 gualis major), which either opens alongside of or joins the mandibular duct. 



THE PHARYNX (Figs. 386, 476, 478) 



The pharynx is short and wide. The vault (Fornix pharyngis) is divided into 

 two culs-de-sac by a median fold of mucous membrane (Septum nasi membrana- 

 ceum), which is a continuation of that of the septum nasi; on the lateral wall of 

 each is the relatively small opening of the Eustachian tube, which is covered by a 

 simple fold of mucous membrane. The posterior nares are small. The entrance 

 to the oesophagus is large. 



On the dorsal wall of the pharynx there are two large suprapharyngeal lymph glands, which, 

 when enlarged, cause difficulty in swallowing and breathing (Fig. 386). 



THE (ESOPHAGUS 

 This is much shorter, wider, and more dilatable than that of the horse. Its 

 average diameter (when moderately inflated) is about two inches (ca. 5 cm.), and 

 its length in an animal of medium size is about three to three and a half feet (ca. 

 90 to 105 cm.). The wall is relatively thin, and the muscular tissue is striped 

 throughout. The latter consists, in the greater part of the tube, of two strata of 

 spiral fibers, except near the stomach, where they are longitudinal and circular. 

 Fibers are continued into the wall of the stomach for some distance. The mucous 

 membrane forms a prominence at the ventral side of the pharyngeal end of the 

 tube which contains glands; elsewhere it is non-glandular. There is no terminal 

 dilatation, and no part in the abdominal cavity. 



A very large mediastinal lymph gland lies above the posterior part of the oesophagus and 

 may, if enlarged, obstruct it (Fig. 389) . 



