1182 



SPLANCHNOLOGY 



the Transversus abdominis, and the Quadratus lumborum (Fig. 1056). It is smaller 

 in caliber and more deeply placed than the ascending colon, and is more frequently 

 covered with peritoneum on its posterior surface than the ascending colon (Treves) 

 In front of it are some coils of small intestine. 



The Iliac Colon (Fig. 1076) is situated in the left iliac fossa, and is about 12 t 

 15 cm. long. It begins at the level of the iliac crest, where it is continuous with 

 the descending colon, and ends in the sigmoid colon at the superior aperture of the 

 lesser pelvis. It curves downward and medialward in front of the Iliacus and Psoas, 

 and, as a rule, is covered by peritoneum on its sides and anterior surface only. 



I 



FIQ. 1077. The posterior aspect of the rectum exposed by removing the lower part of the sacrum and the coccyx. 



The Sigmoid Colon (colon sigmoideum; pelvic colon; sigmoid flexure) (Fig. 1076) 

 forms a loop which averages about 40 cm. in length, and normally lies within the 

 pelvis, but on account of its freedom 'of movement it is liable to be displaced into 

 the abdominal cavity. It begins at the superior aperture of the lesser pelvis, 

 where it is continuous with the iliac colon, and passes transversely across the front 

 of the sacrum to the right side of the pelvis; it then curves on itself and turns 

 toward the left to reach the middle line at the level of the third piece of the sacrum, 

 where it bends downward and ends in the rectum. It is completely surrounded by 

 peritoneum, which forms a mesentery (sigmoid mesocolon), which diminishes in 



