THE COLON 973 



vexity forwards; it also liciids a little downwards. It crosses thr<)U<(h the uiuliilical 

 r(.'gion from the ri;i;lit liyj)oc'lioiidriiiin to the left hypochondrium (tig. oC)")). 



In the majority of cases the superticial part of the colic arch — as seen before the 

 viscera are disturbed — is either in whole or in greater ])art above a straight line 

 drawn transversely across the body between the highest points of tlie iliac crest. 

 In the proportion of one to four it lies, in whole or in greater part, below this line 

 (%. 582). 



Certain remarkable bends are sometimes formed by this part of the bowel. The 

 bending is always in the same direction, namely, downwards, and is usually abrupt 

 and angular. The apex of the V or U-shaped bend thus formed may reach the 

 pubes. This bend appears to be due to two distinct causes: namely, long-continued 

 distension on the one hand, and to congenital malformati(jn on the other. 



The transverse colon is in relation above with the liver and gall bladder, the 

 stomach, and at its left extremity with the s])leen. The third portion of the duo- 

 denum passes behind it. B(>low are the coils of the small intestine. It is sur- 

 rounded with ]K'ritoneum, being connected with the posterior al)dominal wall by a 

 meso-colon. 



The descending colon extends from the spleen to the sigmoid liexure. It is 

 more movable than the ascending colon. It is also narrower. At its beginning 

 it is connected with the diaphragm, on a level with the tenth and eleventh ribs, by 

 a fold of peritoneum, the codo-ndlc ligament (or sustentaculum lienis, from the fact 

 that it supports the s])leen). The bend between the transverse colon and descend- 

 ing colon is called the splenic flexure. The descending colon is situated in the left 

 hypochondriac and luml)ar regions (tig. 501). Its relations to the ]~)eritoneum are 

 the same as obtain with the ascending colon, that is, it is covered in front and on 

 the sides. A meso-colon is met with oftener on* this side than on the right. In one 

 hundred dissections it was found thirty-six times. The descending colon is covered 

 in front by the small intestine; behind, are part of the diaphragm, the left kidney, 

 and the quadratus lumborum muscle (fig. 577). 



The sigmoid flexure and rectum. — The segment of gut termecl the sigmoid 

 flexure, and the so-called first part of the rectun), form together a single simple 

 loop that cannot be divided into parts. This loop begins where the descending 

 colon ends, viz., in the left iliac fossa, and ends at the commencement of the 

 so-called second piece of the rectum — at the spot where the meso-rectum ceases, 

 op])osite ai)out the third piece of the sacrum in the median line. The loop Avhen 

 unfolded describes a figure that may be compared to the capital omega. The aver- 

 age length of this sigmoid or omega loop is seventeen inches ancl a half. The 

 normal position of the loop is not in the left iliac fossa, but wholl}' in the pelvis. 

 The most common disposition of it may now be described. 



The descending colon ends just at the outer border of the psoas. The gut here 

 suddenly changes its direction, and the sigmoid or omega loop l)egins (figs. 565, 

 577 ). The bowel crosses the nuiscle at right angles and about midway between the 

 lumbo-sacral (eminence and Poupart's ligament. It now descends vertically along 

 the left ])elvic wall, and may at once reach the ])elvic floor. It then ])asses more or 

 less horizontally and transversely across the pelvis from left to right, and commonly 

 comes into conta(;t with the right pelvic wall. At this point it is bent upon itself, 

 and, pa.ssing once more towards the left, reaches the middle line and descends to 

 the anus. It will lie therefore in more or less direct contact with the bladder and 

 uterus, and may possibly touch the ca?cum. It is very closely related with tlie 

 coils of small gut that occupy the pelvis, and by these coils the loop is usually 

 hidden. 



The sigmoid or omega loo]) is attach(>d to the abdominal and ])clvie wall by a 

 meso-colon, so that it is (piite surrounded by peritoneum. The line of attachment 

 of this meso-colon is as follows: It crosses the ]>soas at a right angle, and then 

 takes a slight curve upwards so a« to pass over the iliac vessels at or about their 

 bifurcation. The curve ends at a point either just to the inner side of the psoas 

 nmscle, or between the jisoas and the middle line, or, as is most frecjuently the case, 

 just over the liifurcation of the vessels. From this ]>oint the line of attachment 

 proceeds vertically down, taking at first a slight cun-e to the right. Its course is 

 to tlie left of the middle line, while its ending will be ujton that line, about the thinl 



