THE PERITONETBI. 485 



cohere, and it becomes impervious in its lower part. Fat, moreover, 

 accumulates between its laminre ; long slender branches also pass down 

 into it from the gastro-epiploic vessels. 



The part of the membrane just described, which is attached to the 

 great curvature of the stomach and transverse colon, which is con- 

 nected also with the gastro-splenic ligament (or omentum), is usually 

 named the great or gasfro-colic omentum. This may reach the hepatic 

 flexure, and pass a certain way down on the right colon, and this part 

 has been distinguished by Haller and others as the omentum colicum. 

 The great omentum (proper) usually reaches lower down at its left 

 border, and it is said that omental inguinal hernife are more common 

 on the left side. 



The description now given of the relation of the omentum to the 

 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 exterior (here also posterior) layer of the great omentum 

 being described as separating from the layer Avithin, belonging to the 

 omental sac, when it reaches the transverse colon so as to pass behind 

 or below that viscus, and as proceeding from thence 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. ileckel, J. Milller, Hansen, 

 and Huschke, that in the foetus, and occasionally in the child, or even 

 in the adult, the two ascending layers of the omentum, though adherent 

 to the transverse colon, may be separated from it and from the trans- 

 verse meso-colon, so as to demonstrate that the transverse meso-colon 

 is really a distinct duplicature of peritoneum. This view has been 

 adopted by Holden and Luschka in their more recent works, and has 

 been verified by Allen Thomson. Figures oiO a, and b, show diagram- 

 matically the difference of the two views. 



It appears, therefore, that a portion of peritoneum, -which in the foetus passes 

 above the transverse colon to the back of the abdomen, and is thence reflected 

 forwards as the upper layer of the meso-colon. disappears in the adult ; the peri- 

 toneal layers between which it was interposed having cohered to form the trans- 

 verse meso-colon. It is conceivable that the foetal duplicatiu'e may be obliterated 

 by absolution of its substance as the adhesion goes on between the layers, 

 between which it is jslaced ; or, more probably perhaps, it may be drawn or 

 pushed forward from its place in the progress of visceral development, and thus 

 effaced. 



