THE LIVER. 417 



passes from the colon to the stomach forms the gastrocolic omentum and the two 

 organs may be either close together or some distance apart. The transverse colon 

 instead of running upward and to the left may form a large curve downward, reach- 

 ing almost to the pelvis. In cases of dilatation and descent (ptosis) of the stomach 

 the transverse colon descends with it. The transverse mesocolon passes backward 

 and one layer goes up and covers the pancreas while the other goes down to the 

 mesentery. Its importance in gastro-enterostomy has been pointed out (page 406). 

 Tumors and cysts of the pancreas may push forward above it, or below it, or it may 

 cross directly over the surface of the growth. 



The descending colon at its commencement at the splenic flexure is much 

 higher and more deeply situated than is the hepatic flexure. It follows the stomach 

 upward and backward and lies against the spleen. From here it descends and is 

 entirely covered by small intestine, the sigmoid flexure coming to the front in the left 

 iliac fossa. The descending colon is much smaller in size than the ascending colon, 

 and like it in the majority (two-thirds) of cases has no mesentery. In doing a colos- 

 tomy through the loin, the external border of the quadratus lumborum muscle is the 

 guide to the descending colon. It lies 1.25 cm. (^ in.) behind the middle of the 

 crest of the ilium. 



Sigmoid Flexure. The sigmoid flexure is composed of two parts: one in the 

 iliac fossa, called the iliac colon, and the other in the pelvis, called the pelvic colon, 

 or omega loop of Treves. 



The iliac colon is about 12.5 to 15 cm. (5 to 6 in.) long, and runs from the 

 crest of the ilium to the inner edge of the iliopsoas muscle. It has no mesentery in 

 90 per cent, of the cases (Jonnesco), and usually comes into contact with the ab- 

 dominal wall to the inner side of the anterior superior spine sometimes as far down 

 as the middle of Poupart's ligament. In doing an inguinal colostomy this is the 

 portion of the colon it is desired to find. It is then followed down until a part is 

 reached which has sufficient mesentery to allow of its being drawn out of the wound. 



The pelvic colon is about 40 to 42.5 cm. (16 to 17 in.) long and runs from the 

 edge of the psoas muscle to the level of the third sacral vertebra. It makes a large 

 horseshoe-shaped loop, from which it was named by Treves the omega loop, and has 

 a mesentery from 3 to 8 cm. (i^ to 3^ in.) long. The length of the loop as well 

 as its mesentery and its position all vary considerably. Its terminal portion usually 

 runs longitudinally down to end in the rectum, but its intervening portion may pass 

 over the bladder to the right side, or high above the symphysis, or even extend 

 well up in the abdominal cavity. On the under or left side of the loop between its 

 branches is the inter sigmoid fossa (see Fig. 422, page 410) ; sometimes it forms a 

 constricted pouch in which a knuckle of intestine has been known to become 

 strangulated. 



THE LIVER. 



The liver is wedge-shaped and has three surfaces. These are superior, inferior, 

 and posterior. The posterior forms the base of the wedge and its anterior edge is 

 the apex. The liver is divided into five lobes by five primary fissures and has 

 five ligaments (Fig. 428). 



The lobes of the liver are: (i) left, (2) right, (3) quadrate, (4) Spigelian, 

 (5) caudate. The left lobe is one-sixth the size of the right. It comprises that part 

 to the left of the falciform ligament above and the umbilical and ductus venosus fis- 

 sures below. The right lobe comprises that part to the right of the falciform ligament 

 above and the fissures of the gall-bladder and vena cava below. The quadrate lobe 

 is the anterior, small, square-shaped lobe between the fissure of the gall-bladder on the 

 right and the umbilical fissure on the left. It extends from the anterior edge back 

 to the portal fissure. The Spigelian lobe is best seen posteriorly, extending from the 

 vena cava on the right to the fissure of the ductus venosus on the left. The caudate 

 lobe or process is the name given to the liver tissue running from the lower end of 

 the Spigelian lobe to the right lobe. It passes behind the portal fissure and between 

 it and the vena cava. RiedeV-s lobe is the name given to an abnormal, tongue-like 

 projection of liver tissue from its anterior edge, which may extend downward either 

 over the gall-bladder or external to it. Mayo Robson has seen it extend to the caecal 

 27 



