566 JEJUNUM. ILEUM. 



right kidney, and then passes nearly transversely across the third lumbar 

 vertebra ; terminating in the jejunum on the left side of the second 

 lumbar vertebra, where it is crossed by the superior mesenteric artery 

 and vein. The first or oblige portion of its course, between two and 

 three inches, is completely enclosed by the peritoneum : it is in re- 

 lation, above with the liver and neck of the gall-bladder; in front 

 with the greater omenturn and abdominal parietes ; and behind with 

 the right border of the lesser omentum and its vessels. The second or 

 perpendicular portion is situated altogether behind the peritoneum ; it 

 is in relation by its anterior surface with the commencement of the arch 

 of the colon ; by its posterior surface with the concave margin of the 

 right kidney, the inferior vena cava, and the ductus communis chole- 

 dochus ; by its right border with the ascending colon ; and by its left 

 border with the pancreas. The ductus communis choledochus and pan- 

 creatic duct open into the internal and posterior side of the perpendi- 

 cular portion, a little below its middle. The third or transverse por- 

 tion of the duodenum lies between the diverging layers of the trans- 

 vers meso-colon, with which and with the stomach it is in relation in 

 front; above it is in contact with the lower border of the pancreas, the 

 superior mesenteric artery and vein being interposed; and behind it 

 rests upon the inferior vena cava and aorta. 



The Jejunum (jejunus, empty) is named from being generally 

 found empty. It forms the upper two-fifths of the small intestine ; 

 commencing at the duodenum on the left side of the second lumbar 

 vertebra, and terminating in the ileum. It is thicker to the touch 

 than the rest of the intestine, and has a pinkish tinge from containing 

 more mucous membrane than the ileum. 



The Ileum (E/'XS<V, to twist, to convolute) includes the remaining 

 three-fifths of the small intestine. It is somewhat smaller in calibre, 

 thinner in texture, and paler than the jejunum ; but there is no mark 

 by which to distinguish the termination of the one or the commence- 

 ment of the other. It terminates in the right iliac fossa, by opening 

 at an obtuse angle into the colon. 



The jejunum and ileum are surrounded above and at the sides by 

 the colon ; in front they are in relation with the omentum and abdo- 

 minal parietes ; they are retained in their position by the mesentery, 

 which connects them with the posterior wall of the abdomen ; and 

 below they descend into the cavity of the pelvis. At about the lower 

 third of the ileum a pouch-like process or diverticulum of the intestine 

 is occasionally seen. This is a remnant of embryonic structure, and 

 is formed by the obliteration of the vitelline duct at a short distance 

 from the cylinder of the intestine, 



LARGE INTESTINE. 



The large intestine, about five feet in length, is sacculated in appear- 

 ance, and is divided into the caecum, colon, and rectum. 



The Ccscum (caecus, blind) is the blind pouch, or cul-de-sac, at the 



