746 COMPARATIVE ANATOMY 



still further increased by the lateral torsion of the entire stomach. The 

 spleen develops within this widened part and by its weight produces a 

 fullness which in turn causes a sagging down behind (dorsal to) the 

 lesser curvature, although attached to the greater. This tendency con- 

 tinues and causes the free lower fold of the bag-like extension to hang 

 down behind the stomach (Fig. 427). 



This fold is called the greater omentum (omentum majus), which, 

 as all mesenteries are essentially double, must consist of four layers of 

 serous membranes, applied two and two, each pair holding between them 

 the blood vessels and absorbent vessels naturally belonging to a mesen- 



Fig. 435. 



Stomach of a Sheep. 4 abom, abomasum ; d, intestine ; / J ,/ 2 , 

 two folds which divide the rumen (paunch) into three regions; 

 kl, plyoric valve; o (3-4) opening which leads from the third 

 to the fourth stomach region ; oes, oesophagus ; 3, psalt, 

 psalterium (omasus or manyplies) ; 2.ret, reticulum (honey- 

 comb) ; l,rum, rumen (paunch) ; schl.r., pharyngeal groove. 



The piece of wire marked I shows the direction the un- 

 masticated food takes, while // shows the direction of the re- 

 masticated food. (After Carus and Otto.) 



tery. The cavity of the bag is the lesser peritoneal cavity of human 

 anatomy, and the opening into it (behind the stomach) is the foramen 

 epiploicum (foramen of Winslow). While the bag is widely open in 

 most mammals, in man the foramen is considerably reduced in size, and 

 the layers forming the pendulous fold are fused together to form a four- 

 layered apron that hangs below the stomach and covers the intestinal 

 folds. 



THE INTESTINE 



The duodenum takes its name from the twelve inches of rather large 

 diameter intestine which immediately follows the stomach. The word 

 "duodenum" is a name which was taken from human anatomy though 



