ABDOMINAL CAVITY 555 



traced to the medial border of the psoas. They are now 

 observed to pass backwards behind this muscle to the 

 intervals between the transverse processes of the vertebrae, 

 where each gives off a dorsal branch. 



Each dorsal branch runs backwards, between the transverse 

 processes, and, after giving a spinal branch which enters the 

 spinal canal through the intervertebral foramen, it ends in the 

 muscles and integument of the back. 



After giving off their ^b^^/branches the trunks of the arteries, 

 with the exception of the last, proceed laterally behind the 

 quadratus lumborum, and are then directed forwards between 

 the internal oblique and transversus muscles, where they 

 anastomose, above with the intercostal arteries, below with 

 the deep circumflex iliac and ilio-lumbar arteries, and in 

 front with the branches of the superior and inferior epigastric 

 arteries. The last abdominal branch, as a rule, passes in 

 front of the quadratus lumborum. 



Venae Lumbales (Lumbar Veins). These vessels accompany 

 the corresponding arteries, and pour their blood into the inferior 

 vena cava. The veins of the left side pass behind the aorta. 

 The lumbar veins of each side are linked together, in front of 

 the transverse processes of the vertebrae, by anastomosing 

 channels which form a continuous longitudinal vessel, called 

 the ascending lumbar vein. By its upper end this venous 

 trunk is connected with the corresponding azygos vein. 



Last Thoracic or Subcostal Artery. At this stage of the 

 dissection the subcostal artery, the last parietal branch of 

 the thoracic aorta, will be seen crossing the upper part of 

 the quadratus lumborum in company with the last thoracic 

 nerve. It lies in series with the abdominal branches of the 

 lumbar arteries. 



Dissection. The lower limbs having, by this time, been removed from 

 the trunk, the pelvis also may be detached. Place a ligature around the 

 aorta and inferior vena cava at the level of the bifurcation of the former, and 

 divide them immediately above this point. Then carry the knife through 

 the intervertebral disc which intervenes between the third and fourth lumbar 

 vertebrge, and, having cut the nerves and soft parts, complete the separation 

 of the pelvis from the remainder of the trunk by means of the saw. 



PELVIS. 



The pelvis, using the term in its widest sense, is the region 

 bounded posteriorly by the sacrum and coccyx, and laterally 



