SAC OF THE OMEXTUM. 829 



the posterior surface of the stomach and commencement of the duodenum, 

 is continued downwards, back to back with the general peritoneum, into 

 the pendulous portion of the omentum, and, as it returns thence, is applied 

 to the anterior surface of the transverse colon. Passing these parts, it 

 resumes its position of proximity to the peritoneum of the greater sac, 

 and proceeds to the posterior wall of the abdomen. The two layers of peri- 

 toneum which thus hang pendulously one within the other, and are derived 

 from the general and the smaller sac, constitute the yastro-colic or great 

 omentum ; while those by which the transverse colon is connected with the 

 abdominal wall are termed the transverse mesocolon. In the pendulous great 

 omentum, there being a duplication of both the general peritoneum and 

 the wall of the smaller sac, four layers are to be distinguished, viz., first, 

 an anterior and a posterior layer belonging to the greater sac of the peri- 

 toneum, having their smooth surfaces respectively directed forwards to the 

 abdominal wall and backwards to the small intestines ; and second, between 

 these, the anterior and posterior layers derived from the lesser sac, lining 

 the omental cavity and gliding one against the other : these four layers are, 

 however, so intimately united and reduced to such extreme tenuity in the 

 adult, that they cannot be separately recognised in the omentum below 

 the colon. In most instances the pendulous part of the omentum presents 

 the appearance of lacework, the interstices of which in corpulent persons 

 are more or less loaded with fat. In some subjects, instead of lying like 

 an apron over the small intestine, it is crumpled into a bundle along the 

 transverse colon, as if displaced by the movements of the intestines against 

 the wall of the abdomen. 



The description now given of the great omentum and transverse meso- 

 colon agrees with the appearances most frequently seen in the adult subject, 

 and with the account usually given in English works of Anatomy, the pos- 

 terior layer of the great omentum being described as separating from 

 the layer within, belonging to the omental sac, when it reaches the trans- 

 verse colon, so as to pass behind or below that viscus, and from thence 

 as proceeding backwards to the abdominal wall as the posterior or lower 

 layer of the transverse meso-colon. It was, however, long ago pointed 

 out by Haller, and the view has been confirmed by the observations of 

 J. F. Meckel, J. Miiller, Hansen, and Huschke, that in the foatus, and 

 occasionally in the child, or even in the adult, the two posterior layers 

 of the omentum, though adherent to the transverse colon, may be separated 

 from it and from the transverse meso-colon, so as to demonstrate that the 

 transverse meso-colon is really a distinct duplicature of peritoneum. This 

 view has been adopted by Hoi den and Luschka in their more recent works, 

 and has been verified by Allen Thomson. Figures 579 A, and B, show 

 diagrammatically the difference of the two views. 



The anterior wall of the sac of the omentum invests the whole posterior 

 surface of the stomach ; above the small curvature of the stomach it lies 

 back to back with the general peritoneum, completing in conjunction with 

 it a gastro-phrenic ligament ; and further to the right it forms the posterior 

 layer of the gas tro -hepatic omeutum, and likewise invests the lobulus Spigelii 

 of the liver, close to the foramen of Wiuslow. Lying transversely in front 

 of the aorta and in contact with the posterior wall of the abdomen, the 

 pancreas is seen invested anteriorly by the hinder wall of the sac of the 

 omentum. To the left of the stomach the sac extends to the spleen, and 

 usually gives investment to a small portion of that organ at the lower end 

 of its hilus \ it thus forms the posterior layer of the gastro splenic omentum, 



