62 HEAD AND NECK 



with the posterior and anterior lamellae, and, immediately 

 lateral to its line of union with the posterior lamella, the 

 internal oblique arises from its posterior surface. To expose 

 it thoroughly the mass of posterior spinal muscles must be 

 pushed medially. 



Dissection. After the middle lamella has been examined 

 divide it longitudinally, close to its attachment to the tips of the 

 transverse processes, and transversely along the line of the iliac 

 crest, and turn it laterally. A considerable part of the posterior 

 surface of the quadratus lumborum muscle will then be exposed. 

 Displace the lateral border of the quadratus lumborum towards 

 the median plane, and the anterior lamella of the lumbar part 

 of the lumbo-dorsal fascia will be brought into view. 



The anterior lamella of the lumbar part of the lumbo- 

 dorsal fascia is attached, medially, to the anterior surfaces of 

 the roots of the transverse processes of the lumbar vertebrae ; 

 laterally, it blends with the fused middle and posterior lamellae 

 to form the common aponeurosis of origin of the transversus 

 abdominis muscle, and it is by means of the three lamellae 

 of the lumbar fascia that the latter muscle arises from the tips 

 of the spines, and from the tips and the roots of the transverse 

 processes of the lumbar vertebrae. The upper border of the 

 anterior lamella becomes thickened, and extends, anterior to 

 the quadratus lumborum, from the last rib to the trans- 

 verse process of the first lumbar vertebra, as the lateral 

 lumbo- costal arch (O.T. external arcuate ligament); the 

 lower border blends with the ilio-lumbar ligament. The 

 dissector should verify the various attachments by passing 

 his fingers over the posterior surface of the lamella from its 

 lateral to its medial border, and from its upper to its lower end. 



Dissection. After satisfying himself regarding the lamellae 

 of the lumbar part of the lumbo-dorsal fascia and their relations 

 to the posterior spinal muscles, to the quadratus lumborum, and 

 to the internal oblique and the transversus abdominis muscles, 

 the dissector should make a longitudinal incision through the 

 anterior lamella, and the peri-nephric fascia anterior to it ; and, 

 introducing his finger through the opening into the extra- 

 peritoneal fatty tissue, he should scrape away the latter until he 

 exposes the kidney, below the level of the last rib, and the 

 adjacent part of the colon, which lies along the lower and lateral 

 part of the kidney. After that has been done he should reflect 

 the serratus posterior superior and secure its nerves of supply, 

 which spring from the upper intercostal nerves and enter' its 

 deep surface ; then he should remove the thoracic part of the 

 lumbo-dorsal fascia and commence the study of the posterior 

 spinal muscles, beginning with the splenius. 



