514 A MANUAL OF ANA TOMY. 



loop, (c) The superior hemorrhoidal to the upper part of 

 the rectum. These arteries form a chain of anastomoses 

 with one after the other, uniting on the right with the colica 

 media, and below, in the pelvis, with the middle hemor- 

 rhoidal from the internal iliac. 



The longest arterial arches will be found on either side 

 of the colica media. 



This completes the arterial supply of the alimentary canal 

 from the oesophagus to the middle of the rectum. 



The Inferior Mesenteric Vein 



Drains the blood from the area supplied by the artery, 

 passes upward at the left of the artery and behind the peri- 

 neum to empty into the splenic vein just before it unites 

 with the superior mesenteric vein to form the portal vein. 



DISSECTION. 



Double ligature the rectum, and divide it. Remove the large intestine en- 

 tirely, carefully cutting through its peritoneal attachments close to the bowel. 



Tie a cord about the oesophagus as close to the stomach as possible, and 

 divide the former above it. Tie two cords around the first portion of the 

 duodenum and divide between them. Remove the stomach and spleen, sev- 

 ering their ligaments of attachment to the diaphragm and the arteries and 

 veins passing to and from them. 



Raise the duodenum and pancreas, and complete the dissection of the 

 common bile duct, the pancreatic duct, from where it joins the preceding to 

 a distance of two or three inches into the gland, the portal vein, and the 

 tributaries that form it. 



The Portal Vein. Fig. 105. 



This is formed behind the pancreas by the junction of the 

 superior mesenteric and splenic veins. It passes upward 

 toward the right behind the first part of the duodenum to 

 the transverse fissure of the liver. It is about three inches 

 long, and lies between the two layers of the gastrohepatic 

 omentum. It receives the pyloric, gastric, cystic, the supe- 



