M. 



FIG. 35. To show the anterior relations of the lumbar column and sacrum. Semidiagrammatic, the lower portion being repre- 

 sented as somewhat flattened out in order to exhibit the structures. For the lumbar region the figure should be compared with 

 Fig. 27, and for the sacrum, with Fig. 34 (2). A , cut anterior lamella of Transversalis aponeurosis : a, its attachment on 

 transverse process : ps, origin of Psoas : OL, Quadratus lumborum : lig., attachment of small sacro-sciatic ligament, 

 continuous with Coccygeus : N. VS, N. Cocc, anterior divisions of last sacral and coccygeal nerves. The aorta is cut away 

 down to the bifurcation, leaving the lumbar arteries in place ; these are exposed on one side by removal of the Psoas. 

 The first two arteries run under the crus of the Diaphragm on each side as well as the Psoas. They come into contact with 

 the bones as soon as they come off the anterior common ligament. Observe that the main (middle) lamella of Transversalis 

 aponeurosis contains fibres radiating from the ends of the transverse processes, and these are continuous with the costo- 

 lumbar set above and with the ilio-lumbar bands below : all these are behind the plane of puadratus lumborum. The band 

 seen in front of the lower end of the muscle is in the anterior lamella and does not really belong to the proper ilio-lumbar 

 ligamentous system. The central part of the sacrum is covered for its upper half or so by peritoneum, forming the pelvic 

 mesocolon along an oblique line, and supports the rectum below. The peritoneum has been cut to expose the middle sacral 

 artery. Pyriformis origin extends on to the bodies, and this is usually the only part of the origin that is tendinous, making 

 definite markings on the bone. The sympathetic chain and lateral sacral arteries reach the bone under the peritoneum 

 internal to these origins. The small sacro-sciatic ligament is attached to the edge of the bone as far up as the lower level of 

 the articular surface ; it is continuous below with the Coccygeus, the fibres of which muscle also extend on to the front of the bone 

 and join the fibrous tissue which covers this aspect of the bone and the coccyx and separates them from the rectum. The last 

 sacral and coccygeal nerves must pierce the Coccygeus to reach a plane anterior to the bone. Other details are considered in 

 the text. 



