ABDOMINAL VISCERA IN MAN. 201 



Meso-Sigmoid. 



In connection with the meso-sigmoid, it cannot be too much 

 emphasised that the sigmoid flexure has not a long free attach- 

 ment over the left psoas muscle. The part of intestine lying in 

 the iliac fossa is in most cases more or less bound down by 

 peritoneal reflections or by adhesions. The free part of the 

 sigmoid colon, hanging into the pelvic cavity or having a free 

 excursion in the abdomen, is that which has its mesentery 

 attached passing upwards along the inner border of the left 

 psoas muscle. 



The normal meso-sigmoid, as represented in fig. 12, case 17, 

 consists of two limbs. The upper or outer limb when it is 

 present begins over the left psoas muscle about the plane of 

 CD. and passes inwards and downwards to the brim of the pelvis 

 at a point about 1 cm. above the level of the anterior superior 

 iliac spine, and just internal to the left lateral line (5 cm. from 

 the middle line), where the peritoneal attachment turns upwards 

 as the inner limb of the meso-sigmoid. 



The inner limb usually ascends along the inner margin of the 

 left psoas muscle to the summit of the little recess between 

 the psoas muscle and the side of the vertebral body bounding 

 the lumbo-sacral promontory. Here it presents in most cases 

 a sharp bend with the convexity upwards and turns downwards 

 on the side of the vertebral body, or across the little recess, 

 into the pelvic cavity, where it is placed about 2 cm. from the 

 middle line. At the summit of the sharp bend upwards there 

 sometimes persists in the adult a well-marked band or fold 

 passing upwards, which is carefully described by Eobinson (21) 

 as the suspensory ligament of the meso-sigmoid. This fold 

 is shown on No. 14 in fig. 12. 



The length of the mesentery along the outer limb of the 

 meso-sigmoid is very short, and this part of the attached bowel 

 has, as a rule, but little mobility. The length of the meso- 

 sigmoid, on the other hand, along the inner limb is very long, 

 and the attached part of the bowel is freely movable. 



Alterations in the character of the upward bend of the meso- 

 sigmoid are brought about by the altered position of the 

 suspensory fold, causing it perhaps to be very sharply defined. 



