DISSECTION OF THE ABDOMEN. 311 



superior edge of the gland, and passes from its anterior face to the 

 diaphragm, on which it ascends to the spine. The deep layer of the 

 omentum is now to be followed in the backward direction. It is seen 

 to reach the terminal part of the double colon and the initial part of the 

 single colon ; and, separating there from the superficial layer, it passes 

 over the anterior aspect of these portions of intestine, and is reflected 

 forwards on the under surface of the pancreas. It turns round the 

 anterior edge of that gland, covers for a little distance its upper face, 

 and then passes on to the spine, where it meets the same layer advancing 

 in the opposite direction. It is thus seen that the deep layer of the 

 omentum, when traced in the anteroposterior direction, forms a con- 

 tinuous layer ; and at first sight it does not appear to be continuous 

 with the remainder of the peritoneum. As already stated, however, the 

 peritoneum forms a single sac, and the before-mentioned layer is con- 

 tinuous with the remainder of the serous membrane at a narrow opening 

 termed the foramen of Window. To find this opening, pass the dorsal 

 aspect of the left forefinger along the posterior surface of the lobulus 

 caudatus of the liver, close to the spine ; and insinuate the point of the 

 finger onwards towards the left (of the subject). At the same time pass 

 the right hand up to the spine in the cavity of Winslow, and insinuate 

 the forefinger towards the right, above and behind the pylorus. The 

 tips of the forefingers of opposite hands can thus be made to meet, 

 showing the continuity of the larger sac of the peritoneum, in which the 

 left hand is, with the smaller sac, or cavity of Winslow, in which the 

 right hand is. Perhaps the simplest way to get an understanding of 

 the relationship of the two cavities, is to imagine the deep layer of the 

 omentum to be suppressed. In that condition, the anterior aspect of 

 the double and single colon at their point of junction, the pancreas, the 

 posterior surface of the stomach and initial dilatation of the duodenum, 

 the upper parts of the liver and diaphragm, and the roof of the abdomen 

 for a short space behind the hiatus aorticus would be without a serous 

 covering. It may be supposed that to supply this deficiency a pouch of 

 the great sac of peritoneum has to be made. This pouch is made at the 

 foramen of Winslow, the peritoneum being there thrust outwards towards 

 the right, and expanded until it forms what has already been traced as 

 the deep layer of the omentum. The foramen will be observed to have 

 the following boundaries : the base of the lobulus caudatus in front, 

 the 4th part of the double colon behind, the free edge of the gastro- 

 hepatic omentum below, and the posterior vena cava and right pillar of 

 the diaphragm above. 



The Great Mesentery is the membrane that suspends the small intes- 

 tine. Like the omentum, it is composed of two layers of peritoneum. 

 These layers leave the spine at the root of the anterior mesenteric 

 artery, being there continuous with the parietal peritoneum ; and they 



