436 DISSECTION OF THE ABDOMEN. 



The inner surface is smooth ; but the outer is rough, when it is detached 

 from the parts with which it is naturally in contact. The membrane 

 forms processes or folds as it passes from viscus to viscus along the ves- 

 sels ; and the folds attaching the viscera to the abdominal wall consist lor 

 the most part of two layers, one on each side of the vessels. 



The continuity of the sac may be traced in a horizontal and a vertical 

 direction. 



Horizontal circle arottnd the abdomen. The membrane, when followed 

 outwards from the umbilicus, surrounds partly the large intestine on the 

 left side, and fixes it to the abdominal wall. From the colon it may be 

 traced over the kidney as far as the middle line, where it is reflected along 

 the front of the vessels supplying the small intestine, thence around the 

 intestine, and back to the spine along the same vessels. Lastly, it may 

 be pursued outwards to the right kidney, to the colon which it encircles 

 like the left, and along the wall of the abdomen to the umbilicus. 



The piece of membrane fixing the colon on each side to the abdominal 

 wall, is named meso-colon, and that attaching the small intestine is the 

 mesentery. 



Vertical circle from above downwards. From the under surface of the 

 liver the peritoneum may be followed along the hepatic vessels, one piece 

 before and the other behind them to the upper border of the stomach, the 

 two forming the small omentum. At the stomach the two pieces disunite, 

 one passing before, and the other behind it ; but beyond that viscus they 

 are applied to each other to form the great omentum or epiploon. After 

 descending in contact to the lower part of the abdomen they bend back- 

 wards, separating to inclose the transverse colon like the stomach, and 

 they are then continued to the spine, giving rise to the transverse meso- 

 colon. At the attachment of the transverse meso-colon to the abdominal 

 wall, the two companion pieces part from each other one passing up- 

 wards, the other downwards. 1 



The ascending piece is continued in front of the pancreas and the pillars 

 of the diaphragm, and blends with the peritoneum on the under surface of 

 the liver. 



The descending piece or layer may be followed from the transverse 

 meso-colon over the duodenum and the great vessels on the spine (aorta 

 and cava), till it meets with the artery to the small intestine, along which 

 it is continued to form the mesentery, as before explained in tracing the 

 peritoneum in a circular direction. 



From the root of the mesenteric artery the peritoneum descends to the 

 pelvis, and covers partly the viscera in that cavity. For instance, sur- 

 rounding the upper part of the rectum, it attaches this to the abdominal 

 wall by the meso-rectum ; next, it is continued forwards between the rec- 

 tum and the bladder in the male, or between the rectum and the uterus in 

 the female, where it forms a pouch. Thence it passes from the pelvis over 

 the back and sides of the bladder. 



Lastly, the serous membrane is continued to the inguinal region, where 

 it presents the fossae before alluded to (p. 427) ; and it can be traced up- 

 wards on the wall of the abdomen, and over ihe diaphragm and upper 

 surface of the liver, to the under surface of this viscus. 



1 Sometimes the two pieces ascend over the transverse colon, being slightly 

 attached to it and the transverse meso-colon, as high as the pancreas before they 

 separate. In that case the descending layer would form a distinct mesentery for 

 the transverse colon, like that for the small intestine. 



