304 ZOOTOMY. 



and mesenteric arteries, and of the tributaries of the portal 

 vein in the mesentery and on the walls of the intestine : 

 in nearly every case an artery and a vein run side by side, 

 the vein being easily distinguishable from the artery by its 

 greater diameter and thinner walls, and by retaining its 

 blood after death. 



201. Thelacteals, delicate, transparent, colourless vessels 

 in the mesentery, running more or less parallel to the 

 arteries and veins. 



XXI. Pass double ligatures round the rectum just 

 anterior to the pelvic cavity, and round the portal 

 vein just before it enters the liver (the hepatic artery 

 and bile-duct may be included in the last liga- 

 ture). Cut the rectum and vein between the 

 ligatures, cut through the mesenteric attachments 

 of the stomach and intestines, and remove them 

 from the body. Unravel the intestine by cutting 

 or tearing the mesentery, and make out : 



202. The relations of the various divisions of the intestine : 

 the duodenum passes insensibly into the ileum : the ileum 

 at its posterior end enters an ovoidal sac with glandular walls, 

 the sacculus rotundus, which marks the junction between 

 ileum, colon, and cscum : the caecum preserves a tolerably 

 uniform diameter for the greater part of its length, finally 

 narrowing suddenly to form the appendix vermiformis : the 

 first portion of the colon passes insensibly into the caecum, 

 of which it appears to form the proximal part ; about one to 

 two inches from the sacculus rotundus it suddenly narrows 

 and takes on its characteristic sacculations, at the same 

 time making a sharp bend so as to run almost parallel to its 

 former course : the transition between the colon and rectum 

 is also very gradual, the sacculations of the former becoming 

 fainter and fainter. 



