ABDOMINAL WALL 419 



down the deep muscles of the back at the sides of the spines of the vertebrae. 

 In the thoracic region it is a thin transparent lamina which extends from 

 the spines of the vertebrae to the angles of the ribs. At the upper end of 

 the thoracic region it disappears into the neck under cover of the serratus 

 posterior superior. In the lumbar region it becomes much stronger and 

 more complicated. Above it is continuous with the dorsal portion of the 

 fascia and is attached to the last rib. Medially it is attached to the tips of 

 the spines and transverse processes, and to the fronts of the transverse 

 processes of the lumbar vertebrae ; laterally it is connected with the 

 transversus abdominis and the internal oblique, and below it is closely 

 attached to the posterior part of the lateral lip of the iliac crest. In the 

 pelvic region it is attached to the spines of the sacrum and to the back of 

 the lower part of the sacrum and to the back of the coccyx. In the lumbar 

 region its posterior lamella covers the rounded column of the spinal muscles, 

 and to this part the remains of the origin of the latissimus dorsi and the 

 serratus posterior inferior will be found attached. The former must be 

 cleared away, the latter extends upwards and laterally to its attachment to 

 the lower four ribs. It must be cut through at right angles to its fibres 

 and turned aside, its nerves of supply, from the anterior branches of the 

 lower thoracic nerves, being sought for on its deep surface. The remains 

 of its origin from the lumbar fascia must be cleared away and then a 

 vertical incision must be made through the fascia, midway between the 

 medial and lateral borders of the rounded mass of the spinal muscles, and at 

 each end of the longitudinal incision a transverse incision must be made, one 

 just below the last rib and the other just above the iliac crest. The trans- 

 verse incisions should commence at the spine and should not extend beyond 

 the lateral margin of the mass of spinal muscles. The medial part of the 

 divided fascia must be turned to the median plane and its attachments to 

 the tips of the spine verified. The lateral part should be pulled laterally, 

 and at the lateral border of the mass of spinal muscles it will be found to 

 blend with a deeper layer. Push the spinal muscles medially and follow 

 the middle lamella to its attachment to the tips of the transverse processes. 

 The dissectors should then note that the upper fibres of origin of the 

 internal oblique spring from the lumbar fascia just lateral to the line where 

 the middle and posterior lamellae of the fasciae blend. There is still, how- 

 ever, another lamella of the lumbar fascia, the anterior lamella. To 

 display this the dissector must divide the middle lamella vertically, close to 

 its attachments to the tips of the transverse processes, and transversely 

 along the line of its attachment to the iliac crest. The middle lamella can 

 then be turned laterally and the posterior surface of the quadratus lumborum 

 is brought into view. When the lateral border of this muscle is displaced 

 towards the median plane the anterior lamella of the lumbar fascia will 

 be exposed. The dissector should place his finger upon its surface and 

 trace it medially and laterally. Medially he will be able to follow it to, or 

 to within a short distance of the roots of the transverse processes of the 

 vertebrae, and laterally he will find that it joins the remainder of the fascia 

 some distance lateral to the union of the posterior and middle lamellae. 

 He must note, further, that beyond the union of the three lamellae the 

 lumbar fascia is continued into the transversus abdominis, and thus it is, 

 through the lumbar fascia, that the transversus obtains its origin from the 

 tips of the spines, and transverse processes, and the fronts of the transverse 

 processes of the lumbar vertebrae. When he has satisfied himself regarding 

 the lamellae of the lumbar fascia and their relation to the internal oblique 

 and the transversus adominis, the dissector should carefully divide the 

 anterior, lamella longitudinally and introducing his finger, through the 

 incision, into the extra-peritoneal fatty tissue, he should scrape away the 



