LARGE INTESTINE. 507 



then passes nearly transversely across the third lumbar vertebra ; terminat- 

 ing 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 

 oblique portion of its course, between two and three inches in length, is 

 completely enclosed by the peritoneum : it is in relation, above with the 

 liver and neck of the gall-bladder ; in front with the great omentum and 

 abdominal parietes ; and behind with the right border of the lesser omen- 

 tum and its vessels. The second or perpendicular portion is situated alto- 

 gether 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 

 ductiis communis choledochus ; by its right border with the ascending 

 colon ; and by its left border with the pancreas. The ductus communis 

 choledochus and pancreatic duct open into the internal and posterior side 

 of the perpendicular portion, a little below 7 its middle. The third or 

 transverse portion of the duodenum lies between the diverging layers of 

 the transverse meso-colon, with which and with the stomach it is in rela- 

 tion 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 ter- 

 minating 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 (s'/Xsiv, 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 commencement 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 abdominal 

 parietes ; they are retained in their position by the mesentery, which con- 

 nects 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 vestige 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 ccecum, colon, and rectum. 



The Cacum (csecus, blind) is the blind pouch, or cul-de-sac, at the 

 commencement ^of the large intestine. It is situated in the right iliac fossa, 

 and" is retained in its place by the peritoneum which passes over its ante- 

 rior surface ; its posterior surface is connected by loose areolar tissue with 

 the iliac fascia. Attached to its extremity is the appendix vermiformis, a 

 long worm-shaped tube, the rudiment of the lengthened crecum found in 

 all mammiferous animals except man and the higher quadrumana. Thr 



