1 688 HUMAN ANATOMY. 



of the abdominal aorta may burst into the gut, the blood passing between the layers 

 of the transverse mesocolon ; (<?) an iliac abscess may discharge into the ccecum or 

 sigmoid flexure ; {f) the latter may by ulceration communicate with the bladder or 

 vagina ; (^) or may, in chronic fecal distention, produce left-sided varicocele (the 

 more frequent) by pressure on the left spermatic vein. 



The angulation at the junction of the lower end of the sigmoid flexure with the 

 first part of the rectum, caused by the greater mobility of the former and its descent by 

 gravitation to a lower level, often constitutes an obstacle to the passage of a bougie or 

 tube, or sometimes even of liquids, into the sigmoid. In various examinations and in 

 washing out the colon it is therefore frequently desirable to put the patient in the knee- 

 chest posture, which often, by gravity, lessens or removes this cause of obstruction. 



Usually a tube cannot be passed completely through the sigmoid flexure, but 

 often carries the latter with it by engaging in a sacculus or a fold of mucous mem- 

 brane. The tip of the instrument may be felt through the abdominal wall at a point 

 at or beyond the mid-line, which may lead to the mistaken belief that it has entered 

 the colon. Exceptionally it is possible to make it do so, the passage of the tube 

 being facilitated by the injection through it, as it advances, of an oily liquid in suf- ' 

 ficient quantity to distend as well as lubricate the sigmoid curve. 



Woimds of the large intestine are less dangerous than those of any other ^portion 

 of the intestinal tract because (a) the lessened fluidity of the intestinal contents dimin- 

 ishes the risk of fecal extravasation, and (<5) if the wound passes through the lumbar 

 parietes and involves only the posterior wall of the gut, the opening may be entirely 

 extraperitoneal. According to Treves, a mesocolon is found in connection with 

 the ascending colon approximately once in four times, and with the descending colon 

 once in three and one-half times. In 75 cases out of 100, therefore, such a wound 

 of the colon would be attended by a minimum of danger. 



In operations on the large intestine it may be identified by (a) the longitudinal 

 bands, especially the anterior and inner, the posterior being uncovered by peritoneum 

 and therefore less conspicuous, and being placed along the attached border of the 

 ascending and the descending colon ; (b) the epiploic appendages found more abun- 

 dantly along the inner band and on the transverse colon ; (c) its sacculi which may be 

 seen, and its fecal concretions which may often be felt ; and in addition, as compared 

 with the small intestine, (d ) its lesser mobility, greater diameter, and the absence 

 of the palpable transverse ridges of the valvulae conniventes. It should be remem- 

 bered that when it is greatly distended the longitudinal bands and sacculi are almost 

 or quite obliterated, and that the epiploic appendages — peritoneal pouches filled with 

 fat — are absent on the posterior aspect of the gut and in the rectum. 



Colostomy. — {a^ Ljimbar. — If the descending colon is opened through the loin, 

 it should be through an incision following the oblique supra-iliac crease. The course 

 of the gut corresponds to a vertical line 12 mm. (3^ in.) external to the centre of 

 the crest of the ilium. The incision crosses this at its middle, therefore a little below 

 the kidney or on a level with its lower edge, and divides the posterior fibres of the 

 external oblique, the anterior ones of the latissimus dorsi and those of the internal 

 oblique, the lumbar fascia, the posterior fibres of the transversalis muscle, and the 

 transversalis fascia. At this level the descending colon lies in the angle between the 

 psoas and quadratus lumborum muscles. In the absence of a mesocolon (64 per 

 cent. ) the operation should be extraperitoneal. 



{b) higidnal. — An incision similar to that often employed in appendix cases 

 and largely intermuscular may be made, its -centre being 4 cm. (about i J4 in.) from 

 the left anterior superior spine on a line from that point to the umbilicus. The sig- 

 moid flexure, die portion of gut to be opened, may be recognized by the taeniae, the 

 sacculi, the appendages, etc. 



The various operations to effect anastomosis between portions of intestine above 

 and below occluded, diseased, or gangrenous areas depend for their success in many 

 instances upon the mobility of the intestine and therefore upon the existence and the 

 length of a mesocolon. 



In colectomy, or complete resection of a portion of the large intestine, the usual 

 care as to the vascular supply of the retained gut, the inversion of its edges, and the 

 approximation of serous surfaces must be exercised. 



