THE LARGE INTESTINE. 411 



THE LARGE INTESTINE. 



The large intestine comprises (i) the c&cum and appendix, (2) ascending 

 colon, (3) transverse colon, (4) descending colon, (5) sigmoid flexure, composed of 

 the iliac colon and pelvic colon, and (6) the rectum and anal canal. 



The length of the large intestine exclusive of the rectum and anal canal is 135 

 cm. (4 ft. 6 in. ) in the female, and 140 cm. (4 ft. 8 in. ) in the male. If the anterior 

 abdominal wall is removed the caecum and part of the ascending colon are visible, 

 but in the upper part of the lumbar region the colon disappears, being overlaid by 

 the small intestine. Having turned at the hepatic flexure, it again comes into view 

 below the lower edge of the liver and passes superficially across the abdomen to 

 disappear under the left costal margin to form the splenic flexure. It is not visible 

 again until it reaches the region of the crest of the ilium, where it once more 

 becomes superficial and follows the inguinal (Poupart's) ligament down to near its 

 lower end, where it turns backward and upward to form the sigmoid loop which 

 descends along the sacrum. In operating it is necessary to be able to distinguish 

 large from small intestine. 



Size. The large intestine at its commencement at the caecum may have a 

 diameter of 7.5 cm. (3 in.), but it decreases in size, and, especially if empty, the 

 descending colon and sigmoid flexure may only be 2.5 cm. (i in.) in diameter. A 

 distended part of the small intestine will be larger than a contracted part of the 

 colon. Inasmuch as operations are frequently done for obstructive conditions which 

 greatly enlarge the involved parts, it is unreliable to depend on size as distinguishing 

 the large intestine. There are three longitudinal bands (t&nia coli) on the colon, 

 from 6 to 12 mm. (^ to ^ in. ) wide, according to the amount of distention. One 

 is anterior, another postero-external, and the third postero-internal. On the trans- 

 verse colon they have the same relative position when the great omentum and colon 

 are raised and turned upward. They all begin at the appendix and traverse the 

 large intestine until the rectum is reached, where they blend together, forming a 

 longitudinal layer which is weak at the sides and strong anteriorly and posteriorly. 



Sacculation of the colon is produced by the longitudinal bands being one- 

 sixth shorter than the rest of the tube. While sacculation tends to become less 

 marked on distension, it is still a valuable means of identification. Dividing the 

 longitudinal bands will cause the sacculation to disappear and the gut to lengthen. 



Appendices epiploicae or the small tags of peritoneum containing fat, are 

 found along the large intestine as far as the rectum. They are most numerous along 

 the inner longitudinal band and the transverse colon. 



CCUM AND APPENDIX. 



' The caecum is the blind pouch of the large intestine which extends beyond the 

 opening of the ileum. It is about 7.5 cm. (3 in.) broad and 6.25 cm. (2% in.) 

 long. Its three longitudinal bands converge to the appendix and are continued over 

 it. It lies in the right iliac fossa on the iliacus and psoas muscles, more on the 

 latter, and reaches nearly or quite to its inner edge. It is in contact with the 

 abdominal wall above the outer half of the inguinal (Poupart's) ligament. In fetal 

 life the caecum is cone-shaped and passes gradually and regularly into the appendix. 

 It increases in size more rapidly on its outer side, so that the appendix, which was 

 before opposite the long axis of the gut, becomes placed to the inside just below the 

 ileocaecal valve. 



Four varieties of caecum are given by Treves: (i) the conical or fetal type, (2) 

 a globular or quadrilateral type, in which the development of both sides is even, (3) 

 the adult type, in which the outer side is much larger than the inner, (4) an irregular 

 type, in which there is an excess of development of the outer side and an atrophy 

 of the inner side resulting in placing the root of the appendix close to the lower and 

 posterior portion of the ileocaecal junction. 



Cunningham makes three varieties: (i) a fetal conical type, (2) an infantile 

 type, in which the outer side is somewhat larger than the inner, and (3) an adult 



