THE FASCIA LUMBORUM. 521 



lumbar fascia between the last rib and the hip bone, in company 

 with the worker on the abdomen. 



In the region referred to are portions of the external and internal Define 

 oblique muscles in the wall of the abdomen. Define the posterior oSfque 1 

 border of the external oblique (fig. 98, p. 265). Internal to this 

 the aponeurosis of the transversalis muscle (fascia lumborum, p. 272) 

 appears, and perforating it are two nerves : one, the last dorsal, 

 with an artery near the last rib ; and the other, the ilio-hypogastric, 

 with its vessels close to the iliac crest. 



Three layers of the fascia lumborum are to be demonstrated, to show 

 passing from the aponeurosis of the transversalis to the spinal j-kreejayers 

 column. The superficial layer is already exposed, being formed posterior, 

 mainly by the aponeurosis of the latissimus dorsi. To see the 

 middle layer, which passes beneath the erector spinae to the trans- 

 vt-r.se processes, the first layer is to be divided, with the attached 

 portion of the latissimus dorsi, by a horizontal incision carried 

 outwards from the third lumbar spine. On raising the outer middle, 

 border of the erector spinae muscle, which comes into view, the 

 strong middle process of the fascia will be apparent. 



After cutting in the same way through this prolongation, another and anterior, 

 muscle, the quadratus lumborum, will be seen ; and, on raising its 

 outer border, the thin deepest layer of the fascia will be evident 

 on the abdominal aspect of that muscle. 



The FASCIA LUMBORUM Or LUMBAR APONEUROSIS Occupies the Lumbar 



interval between the last rib and the iliac crest, and extends fa ' 

 inwards to the spine. It is formed mainly by the posterior tendon transversalis 

 of the transversalis muscle of the abdominal wall (fig. 101, c, tendon > 

 p. 271), but its superficial part receives important accessions from 

 two of the muscles of the back. If the tendon of the transversalis 

 be followed inwards, it will be found to divide at the outer edge 

 of the quadratus lumborum into two layers, which encase that 

 muscle ; and the posterior of these again splits, or gives off a 

 superficial process, at the outer margin of the erector spinae. There 

 are thus in the lumbar aponeurosis three layers of membrane, consists of 

 forming with the vertebrae two sheaths, the one of which encloses three layers : 

 the quadratus lumborum, and the other the multifidus and erector 

 spinae muscles. 



The anterior layer is thin, and passes on the abdominal surface anterior, 

 of the quadratus lumborum to be fixed to the front of the trans- 

 verse processes of the lumbar vertebrae near their tips. 



The middle layer is the direct continuation of the transversalis and middle 

 tendon, and lies between the quadratus lumborum and the erector J^* 88 " 

 spinae muscles ; it is fixed to the extremities of the transverse processes ; 

 processes. 



The posterior or superficial layer is the thickest, and is attached posterior to 

 internally to the spines of the lumbar vertebrae. In this layer are processes, 

 united the aponeuroses of the latissimus dorsi and serratus posticus 

 inferior muscles, with only a small offset of the tendon of the 

 transversalis. 



Directions. The structures in the floor of the posterior triangle 



