DISSECTION OF THE ABDOMEN. 317 



subject inclines considerablj' over to the left side. Two ligatures a few 

 inches apart are to be passed round the duodenum where it encircles the 

 crook of the caecum, and the bowel is then to be cut across between the 

 ligatures, the object of which is to keep the contents from escaping. 

 Where the small colon joins the rectum, at the entrance to the pelvis, 

 the bowel is to be served in the same way, and the colic mesentery is to be 

 cut along its point of origin at the spine. Both large and small intestines 

 are then to be thrown as far as possible outwards over the left flank. 

 The next step must be to take the scalpel and carefully sever the con- 

 nective tissue adhesions between the cseoal crook and colon on the one 

 hand, and the sublumbar region and pancreas on the other. In doing 

 this, the dissector must cut close to the wall of the bowel, and take 

 especial care not to take away any portion of the pancreas, which will 

 be recognised by its dark colour. The operation will be favoured by the 

 weight of the intestines, which tends to tear these connections. When 

 the caecum and colon have been freed, it will be found that strong resist- 

 ance to the removal of the intestines is still offered by the mesentery, or 

 rather, by its included vessels. These must therefore be cut near the 

 spine, and the entire mass will then slip over the left side, the omentum 

 beino- cut or torn from its attachment to the colon. The intestines 

 should now be spread out on a table ; and, when the student has refreshed 

 his memory regarding their form and connections with one another, he 

 must proceed to examine their structure. This should be done by taking 

 a short piece of the gut, slitting it up, and pinning it with its mucous 

 surface downwards on a block of wood. 



Structure of the Small Intestine. The wall of the bowel is made 

 up of four layers, viz., serous, muscular, submucous, and mucous. 



1. The Serous Layer, the most external, is a part of the visceral 

 peritoneum. It reaches the bowel by the mesentery, whose two layers 

 separate at the concave border of the intestine, and pass round each 

 side to meet and become continuous on its convex or free border. It is 

 closely adherent to the subjacent muscular layer, which it completely 

 covers except at the line of separation of the two layers of the mesentery, 

 where the vessels enter. It must be stripped off to expose the next coat. 



2. The Muscular Coat is made up of two distinct sets of fibres : 

 1. Longitudinal fibres, which are most external, and form a thin layer 

 uniformly spread along the wall. 2. Circular fibres, thicker than the 

 preceding, and also spread over every part of the wall. These fibres are 

 of the pale, non-striated variety. 



3 The Submucous Coat is composed of loose areolar tissue uniting 

 the muscular and mucous layers. In the duodenum it contains the 

 glands of Brunner, which have the racemose type of structure, and are 

 about the size of a hemp seed. Their ducts pass through the mucous 

 membrane, and open on its free surface. 



