428 DIGESTIVE SYSTEM OF THE DOG 



(Torus tubarius). The oesophageal opening is relatively small and is encircled by a 

 fold of the mucous membrane. The hyo-pharyngeus muscle is clearly divided 

 into a kerato-pharyngeus and a chondro-pharyngeus. 



THE (ESOPHAGUS 

 The oesophagus is relatively wide and dilatable except at its origin. The 

 constriction at its origin is termed the isthmus oesophagi. The cardiac end is 

 slightly dilated; it joins the stomach under the tenth or eleventh thoracic vertebra, 

 slightly to the left of the median plane. The muscular tissue is striated and con- 

 sists mainly of two layers of spiral fibers which cross each other; near the cardia, 

 however, the fibers are longitudinal and circular. There are mucous glands and 

 lymph glands in the submucosa throughout. 



(Esophagus 



Lesser curvature . ^Kf- 

 Bile-duct 



Pylorus 



Fig. 3.31. — Stomach of Dog, Parietal Surface. 

 Organ fixed in situ when well filled. 



THE STOMACH 

 The stomach is relatively large. Its capacity in a dog weighing about 40 

 pounds is about six to seven pints. 



Colin estimate.s the average capacity at about 3 liters (ca. 6J2 pints), with a range between 

 0.6 and 8 liters (ca. lA to 17 1 2 pints). Neumayer gives the capacity as 100 to 250 c.c.per kilogram 

 of body-weight (ca. 2.7 ounces per pound). The average capacity of the human stomach is esti- 

 mated at 35 to 40 ounces — only about one-half of that of a dog of medium size. 



When full it is irregularly pyriform. The left or cardiac part (Corpus 

 ventriculi) is large and rounded, while the right or pyloric part (Pars pylorica) is 

 small and cylindrical. When empty, or nearly so, the left sac is strongly contracted; 

 the pyloric part is not materially affected by variations in the amount of ingesta. 



The parietal surface of the full stomach is very extensive, strongly convex, 

 and faces partly forward, but largely to the left. It is related to the liver, the left 

 part of the diaphragm, antl the left and ventral abdominal wall as far back as a 

 transverse section through the second or third lumbar vertebra. 



The visceral surface is much less extensive and is considerably flattened; it 

 faces chiefly to the right, and is related to the intestine, pancreas, and left kidney. 



The upper part of the lesser curvature is nearly straight and vertical, but the 

 lower part forms a deep, narrow angle, due to the fact that the pyloric part is 

 directed sharply forward and upward. 



