DIGESTIVE SYSTEM OF THE SHEEP 



407 



The salivary glands resemble those of the ox in general, but the parotid duct 

 crosses the surface of tlie masseter muscle, and opens opposite the third or fourth 

 cheek tooth. 



The tonsil is bean-shaped and about half an inch (ca. 12 mm.) in length. It 

 does not project into the fauces. The mucous meml^rane of the latter presents two 

 deep and very narrow tonsillar sinuses on either side. 



Fig. 30.3. — Cross-section of Sheep, through Ninth Thoracic Vertebra, Anterior View. 

 i. Cardiac orifice; ^, a?sophageal groove; 3, rumino-reticular orifice; 4. ''uniino-reticular fold; 5, dorsal sac 

 of rumen; 6, body of ninth thoracic vertebra; 7, vena hemiazygos; 8, aorta; 9, posterior mediastinal lymph 

 gland; /O, 70, crura of diaphragm; ^7, posterior vena cava; /;2, portal vein; i?./., right lung; L./., left lung; S, 

 spleen (cut very ol)liquely); L, liver; R, reticulum (posterior wall), .\rrow points to reticulo-omasal orifice. 



The fornix of the pharynx presents a median plicated fold which is a continua- 

 tion of the septum nasi. The pharyngeal orifice of the Eustachian tube has the 

 form of a crescentic slit, placed aliout on a level with the inferior nasal meatus. 

 There are two large l>mph glantls and a number of hsemolymph glands above the 

 pharynx. 



The oesophagus has a lumen of about an inch when moderately distended: 

 otherwise it resembles that of the ox. 



