DISSECTION OF THE ABDOMEN. 307 



placed on the Avail of the bowel, at the edge of the mesentery ; but a few- 

 are included between the layers of the colic mesentery. The lacteals 

 from the small intestine and the lymphatic vessels from the large intes- 

 tine traverse these various groups of glands on their course towards the 

 receptaculum chyli. 



The Sympathetic Nebve. This nerve forms on the aorta, in front of 

 the anterior mesenteric artery, a great network termed the Solar plexus. 

 The solar plexus is at present concealed by the pancreas, but the student 

 has to notice the anterior and posterior mesenteric plexuses, which are 

 wholly or in part derived from it. 



The Anterior Mesenteric Plexus comprises numerous nerves already 

 met in dissecting the branches of the anterior mesenteric arteiy. The 

 nerves interlace around the arteries, and pass with them to gain the 

 bowel, where they further interlace before penetrating its wall. 



The Posterior Mesenteric Plexus. — The branches of this plexus run in 

 company with the divisions of the artery of the same name. Its nerves 

 are derived in part from the aortic plexus, which is a backward continua- 

 tion of the solar plexus, and in part from roots furnished by the lumbar 

 cord of the sympathetic. The ultimate branches are distributed in the 

 wall of the small colon and rectum. 



Directions. — The intestinal mass is now to be removed in the following 

 manner. The ropes must be unfastened from the left limbs of the animal, 

 while those on the right limbs are to be lengthened until the subject 

 inclines considerably 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 liga- 

 tures, 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 Avay, 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 throAvii as far as possible oiitwards over the left flank. 

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

 nective-tissue adhesions between the caecal 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 

 rathei-, 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 

 being 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 



