370 COMPARATIVE SPLANCHNOLOGY. 



canal is wrinkled on its free surface, but on the interior resembles that of the 

 oesophagus, being white, and longitudinally folded. At its opening into the 

 third compartment are a number of conical papillae. Transverse and longitu- 

 dinal muscular fibres control the canal ; the longitudinal fibres, by drawing 

 the lips of the pillars together, form a channel leading from the oesophagus 

 into the third compartment, thus eflfectually closing the openings into the 

 rumen and reticulum. 



The third com-psLTtment , psalterium or omasum, is situated at the anterior 

 extremity of the right sac of the rumen. When full, it is ovoid, slightly curved, 

 and depressed from above downwards. The anterior surface is in relation with 

 and attached to the diaphragm by cellular tissue, while the posterior is related 

 with the rumen. The greater or convex curvature is turned upwards, and 

 fixed to the posterior fissure of the liver by a fold of peritoneum, which is con- 

 tinued on to the lesser curvature of the fourth compartment, and thence to 

 the duodenum. The lesser curvature looks downwards, and is related with 

 the reticulum. The left extremity is constricted, forming the neck, by which 

 it communicates with the reticulum. The right extremity is continuous with 

 the base of the fourth compartment, from which it is separated by a constric- 

 tion similar to, but less marked than, the neck. 



The interior presents two openings, one of which communicates with the 

 second, the other with the fourth compartment. It is filled with leaves or 

 folds of mucous membrane, which follow the long axis of the organ. They are 

 unequally developed, and attached by one border to the great curvature of the 

 cavityi while the other, free and concave, is turned towards the lesser curva- 

 ture. The cavity being ovoid, the central leaves are the largest ; and between 

 each pair of large we have intermediate and small leaves, which extend a 

 limited distance only. They consist of an inner framework of muscular fibres, 

 clothed with mucous membrane, and studded with papillae, some of which are 

 small, others large and bent, the latter retaining crude portions of food, for 

 further trituration and maceration, while fluid and finer pabulum pass directly 

 through into the fourth compartment. The papillae at the entrance of the 

 oesophageal canal are large and hooked ; perhaps their use is to retain the 

 alimentary material in the cavity, to which end the latter is also furnished 

 with a small valve at the orifice leading into the abomasum. 



The fourth, the true digestive compartment, or abomasum, is curved upon 

 itself, elongated from before backwards, and continuous with the psalterium 

 about the right sac of the rumen. The right side is in the epigastric region, and 

 related with the diaphragm, while the left contacts the rumen. The greater 

 curvature is turned backwards, receiving the insertion of the great omentum ; 

 the lesser is directed upwards, and is attached by serous membrane to the 

 greater curvature of the psalterium. The base is in contact with the cul-de-sac 

 of the second, and separated from the third compartment by a constriction. 

 The point, directed upwards and backwards, is continuous with the duodenum, 

 forming the pylorus, which is constricted by a muscular ring. The interior 

 resembles the villous portion of the stomach of the horse, and the mucous 

 membrane is thrown into oblique folds, crossing from end to end in a spiral 

 direction. The serous coat is a continuation of the great omentum, the 



