THE DIGESTIVE SYSTEM 



79 



communicate with the middle ear. The latter are slit-like 

 openings, situated high up on the lateral walls of the pharynx, 

 with a cartilaginous flap, which closes during swallowing. 



The esophagus is a fibromuscular tube which connects the 

 pharynx with the stomach. It is about £}i feet long and runs 

 down the left side of the neck. Upon reaching the thorax it 

 assumes a median position, passes between the two lungs, pierces 



Fig. 23. — Stomach of ox; right view: Oes., esophagus; 1, right longitudinal 

 groove of rumen; 2, posterior groove of rumen; 3, 4, coronary grooves; 5, 6, 

 posterior blind sacs of rumen; 7, pylorus. (Sisson, Anatomy of Domestic 

 Animals.) 



the diaphragm, and at once enters the stomach. The lining 

 membrane in the esophagus of the horse is always thrown up in 

 folds except during the act of swallowing. This organ in the ox 

 is about 2 inches in diameter and capable of dilating to a 

 considerable extent. 



The stomach of the horse is a U-shaped sac located between 

 the esophagus and intestines (Fig. 22). It has a capacity of 

 2 to 4 gallons. The inlet or cardia and the outlet or -pylorus are 

 close together. It is situated in the abdominal cavity opposite 

 the fourteenth to sixteenth ribs, behind the diaphragm and liver, 



Digitized by Microsoft® 



