THE ABDOMEN. 



393 



the ilium. It passes upward and. forward to insert into the inner lip of the bicipital 

 groove of the humerus. 



It will thus be seen that while the direction of the outer fibres of the latissimus 

 dorsi is from below upward and forward, the direction of those of the quadratus 

 lumborum is upward and backward. It will also be observed that the attachment 

 of the quadratus lumborum is farther out on the crest of the ilium than is that 

 of the latissimus dorsi, reaching about its middle (Figs. 408, 409 and 410). 



Fascias. The lumbar fascia (fascia lumbodorsalis), so called, is the 

 continuation backward of the posterior aponeurosis of the transversalis and internal 

 oblique muscles to the spine. When the aponeurosis, from which these two muscles 

 spring, reaches the outer edge of the quadratus lumborum, it splits; one thin layer 

 goes on its ventral surface to be attached to the roots of the transverse processes of 

 the vertebrae; the other thick posterior layer, on reaching the edge of the erector 



Latissimus dorsi 



External oblique 



Petit's triangle and 

 internal oblique 



Sacrospinalis (erector 

 spinae) 



FIG. 407. The lumbar region, superficial view. 



spinae muscles divides into two, the anterior of which covers the dorsal surface of the 

 quadratus lumborum and the ventral surface of the erector spinae to attach itself to 

 the tips of the transverse processes, while the posterior layer passes over the dorsal 

 surface of the erector spinae to be attached to the spinous processes of the lumbar 

 vertebrae. These three layers are called the anterior, middle, and posterior layers 

 of the lumbar fascia (see Fig. 410). 



The anterior layer is attached to the tip of the twelfth rib and arches inward to- 

 the transverse process of the first or second lumbar vertebra, to form the external 

 arcuate ligament of the diaphragm. It is practically continuous with the transver- 

 salis fascia. 



The middle layer is attached above to the last rib, and below to the iliac crest, 

 ant;, is very strong. 



' The posterior layer is continuous above with the vertebral aponeurosis and gives 

 origin to the latissimus dorsi muscle. 



