THE GREAT OMESTl'M 



1001 



The dotted line represents the position of tlie hag ; a and p represent sections of its 

 anterior and posterior walls. 



The bag becomes larger and larger, and more and more pendulous, until it at 

 last hangs down over the transverse colon ayd the small intestines as a kind of 

 apron. Its orifice^ becomes narrowed in time by the growth of structures around 

 it, and is known as the foramen of Winslow. 



If the finger be introduced into this foramen, it will touch the ])Osterioi- wall of 

 the stomach, and consecjuently the right (or jx^sterior) layer of the original meso- 



Ficj. (>01.— GuEAT Omentum in Mavuoi'Vh peswillatuh. 



TOMACH 



TURNED Aaice 



"- O- '-.,. OMENTUM 



cur op.cN. 



gaster. As both layers of the meso-gaster enter into the formation of this pouch 

 or apron, it must of necessity be formed of four layers of peritoneunj. 



The place where the bulging takes place is a matter of importance. Originally 

 such part of the meso-gaster is involved in it as extends from the region of the 

 ])ylorus to about the middle of the fundus of the stomach (fig. 600). 



In the lower mammals' the rudimentary disposition of the great omentum is 

 well seen. Thus in the two-toed anteater it may be observed in its simplest possible 



Fig. 602. — Foemation of Great Omentum as seen in Vertical Section. 



condition. It here takes the form of a slight bag jirojecting towards the left, and 

 formed solely by that part of the primitive meso-gast«'r which is nearest to the 

 greater curvature of the stomach. It extends to the right as far as the i)ylorus. It 

 is quite horizontal. Its greatest depth does not exceecl an inch, and its orifice is a 

 wide, shallow^ opening upon the right side of the meso-gaster. 



In higher mammals — as in some marsu]iials — the great omentum apjicars as a 

 loose, pendulous, open l)ag, with so large an oi)ening tiiat it could not l)e termed a 

 foramen. (Fig. 601 shows the great omentum in the kangaroo.) 



