PRACTICAL CONSIDERATIONS : THE ABDOMEN. 529 



Wounds involving the muscular layers of the abdominal wall may gape widely, 

 but the differing directions of the fibres of the external oblique, internal oblique, 

 and transversalis tend to limit this just as they lessen the after-risk of ventral hernia 

 and favor certain physiological acts, as the emptying of the bladder, the bowels, or 

 the uterus, "This difference of direction is taken advantage of in gaining access to the 

 abdominal cavity in some operations (page 535). 



Infection in the lateral intermuscular spaces usually spreads rapidly on account 

 of the abundance of loose cellular tissue. The cellulitis or resulting abscess (or 

 collection of blood or air) will be limited by the semilunar line in front, by the costo- 

 chondral arch above, by Poupart's ligament and the crest of the ilium below, and by 

 the edge of the erector spinae behind ; in other words, by the attachments of the 

 muscles between which they spread (Treves). 



Beneath the abdominal wall, practically making a portion of it, lies a layer of 

 loose connective tissue — the subperitoneal or subserous areolar tissue — which connects 

 the peritoneum with the parietes. ' ' Extraperitoneal connective tissue' ' has been sug- 

 gested (Eccles) as a better name for it. Infection of this tissue, whether from without, 

 as in the case of wounds, or by extension from some of the viscera lying wholly or 

 partly behind the peritoneum, as in perirenal abscess or certain forms of appendiceal 

 abscess, is likely to spread widely. Abscesses, especially if chronic, often gravi- 

 tate into the iliac fossa and are arrested at Poupart's ligament by the junction of the 

 transversalis and iliac fasciae, constituting a form of iliac abscess. If they are incised 

 here, it will usually be necessary to go through only the abdominal muscles and 

 aponeuroses, including the transversalis fascia, as the looseness and abundance of 

 the subserous tissue will have permitted the abscess to dissect off and push upward 

 the peritoneum. If the patient is supine, pus in the iliac fossae — i.e., in the shallow 

 lower zone of the abdomen — may gravitate into the deep lateral recesses of the 

 middle zone (page 1615), and it often takes this direction in cases in which the 

 source of infection is an appendix situated behind the caecum. It should be noted 

 that a true iliac abscess is beneath the iliac fascia, and is therefore more apt to 

 be guided by that fascia to the lowest point of the ilio-psoas space and to pass 

 with the ilio-psoas muscle into the thigh, pointing at the outer side of the femoral 

 vessels. 



The laxity of the subserous tissue favors certain retroperitoneal operations — 

 e.g., uretero-lithotomy — by permitting the stripping forward of the peritoneum 

 itself. The relatively great resistant power of the side of the peritoneum in contact 

 with this tissue is subsequently described (page 1754). The fat contained in this 

 layer — greatest in the lumbar region {perinephric fat) and in front of the bladder in 

 the space of Retzius (the triangular interval defined by the symphysis pubis, the 

 bladder, and the peritoneum), and abundant in the inguinal and iliac regions — 

 may serve as a guide in approaching the peritoneum by incision, or may mislead if 

 mistaken for the omental fat. The latter error has resulted, as, for example, in 

 operation for ovarian cyst, in regarding the peritoneum as the cyst-wall, and in 

 detaching it from the parietes over a wide area. This fat occasionally works its way 

 through intervals between the fibres of the overlying fascia or muscles, especially 

 along the linea alba, and constitutes the subseroiis lipomata, which, if large enough, 

 are sometimes thought to be irreducible ventral herniae. The laxity of the subse- 

 rous areolar layer between the bladder and the posterior surface of the symphysis 

 pubis permits the peritoneum to be carried up on the summit of a distended bladder 

 as it rises into the abdomen and thus facilitates extraperitoneal access to the an- 

 terior vesical wall (page 1912). Its looseness over the iliacus muscle is a factor 

 in the formation of the sac of inguinal hernia (page 1767). Wounds of the abdom- 

 inal wall dividing this subserous layer, but leaving the peritoneum untouched, 

 should practically be classified among 7ion-penetrati7ig wounds, although in a sense 

 the abdominal cavity has been opened. The symptoms and dangers of infec- 

 tion will be as above enumerated. Wounds involving the peritoneum are called 

 penetrating wounds, the dangers of which have been considered in the section on 

 the peritoneum. 



In the closing of abdominal wounds the irregularities that may result from the 

 differing directions of the muscular fibres involved — causing greater retraction at one 



34 



