530 HUMAN ANATOMY. 



point than at another — should be remembered. This may make accurate suturing 

 in layers difficult, but such suturing, together with careful approximation of the edges 

 of the peritoneal layer, is necessary to lessen the risk of ventral hernia. 



The respiratory movements prevent the attainment of absolute rest during the 

 healing of abdominal wounds, as they do after fractures of ribs ; but in both cases 

 approximate rest, as secured by strapping with adhesive plaster or by abdominal 

 binders, gives excellent average results. 



THE LOIN. 



The posterior abdominal wall is in far less intimate association with the peri- 

 toneum or the small intestine, and is, in its relation to injury or disease, of less 

 importance than the antero-lateral walls, but it will be convenient to consider it and 

 the loin here. Contusions, if over the ilio-costal space, — the posterior segment of 

 that portion of the abdominal wall which has no bony protection, — are apt, if severe 

 enough, to result in injury to the friable kidneys (page 1891) rather than to the rela- 

 tively strong and elastic ascending or descending colon. IVounds, if they pass 

 through the entire thickness of the wall, may involve either of these structures. 

 When they become infected, the resulting cellulitis or abscess will be influenced as to 

 the direction it takes and in its limitations by the various fasciae and muscular sheaths. 

 The subcutaneo2is connective tissue is loose and abundant, and is frequently the seat 

 of suppuration or of extensive collections of blood which gravitate towards the iliac 

 crest or pass below it. The boundaries of effusion into the iriter muscular spaces 

 external to the edge of the erector spinae have already been described {vide supra). 

 Within the musculo-aponeurotic compartments made by the splitting of the strong 

 lumbar fascia into three layers (page 508) and enclosing the erector spinae and 

 quadratus lumborum muscles the products of suppuration may for a time be con- 

 fined. The middle and posterior layers are, moreover, very dense and resistant, and 

 therefore, as they form the sheath of the erector spinae, that muscle is rarely the seat 

 of abscess of other than vertebral origin ; beginning in caries of the neural arches, 

 however, an abscess may directly penetrate the muscle between its fibres of origin or 

 insertion. The anterior layer, separating the quadratus lumborum from the sub- 

 serous areolar tissue, is very thin and is continuous with the transversalis fascia. For 

 this reason, abscesses originating about the kidney or around the caecum or sigmoid 

 not infrequently perforate this layer and pass either directly through the outer third 

 of the thin quadratus lumborum external to the erector spinae (which buttresses its 

 inner two-thirds) or through the transversalis fascia external to the quadratus. If 

 they are high (perirenal), they may follow the last dorsal nerve, which pierces this 

 fascia and the transversalis muscle just below the last rib, and may then make their 

 way through the internal oblique and appear at the outer border of the erector 

 spinae ; or they may gravitate to the triangle of Petit, — the interval between the 

 crest of the ilium (its base) and the converging edges of the external oblique and 

 latissimus dorsi, — where, as the floor of the triangle is formed by the internal 

 oblique, they will be subcutaneous as soon as they have perforated the latter muscle. 

 An abscess of lower origin (pericaecal, pericolic) may reach the same space by fol- 

 lowing the ilio-hypogastric branch of the first lumbar nerve. 



Abscesses in the lumbar subserous areolar tissue are more frequent on the right 

 side, on account of the presence of the appendix. Like abscesses of perinephric 

 origin occupying the same situations, they may open into the colon or sigmoid. As 

 this tissue is continuous below with the corresponding layer in the pelvis, abscesses 

 originating there may ascend and appear at one or other of the various points de- 

 scribed. Tiue iliac abscesses (^vide supra) are beneath the iliac fascia, which is con- 

 tinuous with the transversalis fascia at Poupart's ligament, but encloses the ilio-psoas 

 muscle in a definite compartment, weak below, where the fascia accompanies the 

 muscle beneath Poupart's ligament to become the pectineal fascia. The upper part 

 of this fascia, covering the psoas muscle, is thinner and less resistant than the lower. 

 Abscesses beginning in disease of the lumbar spine may penetrate directly into the 

 muscular substance. Those beginning in the thoracic spine are often so limited an- 

 teriorly by the internal arcuate ligament and posteriorly by the spine and last rib 



