490 DISSECTION OF THE ABDOMEN. 



the posterior wall of the abdomen to the internal abdominal ring, where 

 it enters the spermatic cord (p. 418). In its course beneath the peri- 

 toneum the vessel runs along the front of the psoas, crossing over the 

 ureter ; and on the right side it passes over the vena cava. It is accom- 

 panied by the spermatic vein, and the spermatic plexus of nerves. In the 

 foetus before the testicle leaves the abdomen the spermatic artery is very 

 short, but the vessel elongates as the part supplied is removed from its 

 former site. 



In the female the corresponding artery (ovarian) descends into the 

 pelvis to end in the ovary and the uterus. 



The parietal branches of the aorta are the diaphragmatic, lumbar, and 

 middle sacral. 



The diaphragmatic arteries (inferior phrenic) (fig. 171, a) are directed 

 outwards along the under surface of the diaphragm near the posterior 

 part, the left artery passing behind the ocsophageal opening, and the right 

 behind the vena cava. Each ends in two branches : One (internal) passes 

 onwards towards the fore part of the diaphragm, and anastomoses with its 

 fellow, and with the branch (superior phrenic) to the diaphragm from the 

 internal mammary (p. 239). The other (external) is larger, and is di- 

 rected outwards to the side of the muscle, where it communicates with 

 the musculo-phrenic and intercostal arteries. 



Branches. Small offsets to the suprarenal body from the external divi- 

 sion of this artery are named superior capsular. Some twigs are given 

 by the left artery to the oesophagus, and by the right to the vena cava. 



On the under surface of the diaphragm are two branches of the internal 

 mammary artery ; one (superior phrenic, p. 239) accompanies the phrenic 

 nerve, and ramifies over the middle of the muscle ; the other (musculo- 

 phrenic, p. 239) appears opposite the ninth rib, and passing along the 

 edge of the thorax, gives offsets to the lower intercostal spaces. 



The other parietal branches, viz., lumbar and middle sacral, are not 

 learnt in this stage : the former will be seen after the lumbar plexus, and 

 the latter in the pelvis. 



The COMMON ILIAC ARTERY (fig. 171, ^) is directed Qutwards from the 

 bifurcation of the aorta, and divides into two large trunks opposite the 

 fibro-cartilage between the base of the sacrum and the last lumbar verte- 

 bra : one of these (external iliac) supplies the lower limb, and the other 

 (internal iliac) enters the pelvis. Placed obliquely on the vertebral 

 column, the vessel measures about two inches in length. It is covered by 

 the peritoneum, and is crossed by branches of the sympathetic nerve, and 

 sometimes by the ureter. It is accompanied by a vein of the same name. 

 Usually it does not furnish any named branch, but it may give origin to 

 the ilio-lumbar, or a renal artery. On opposite sides the vessels have 

 some differences. 



The right artery is rather the longest, in consequence of the position of 

 the aorta on the left side of the spine. To its outer side at first is the 

 vena cava, and near its termination is the psoas muscle. The companion 

 vein (jo) is at first beneath, but becomes external to the artery at the 

 upper part ; and beneath the right artery also is the left common iliac vein. 

 The left artery is crossed by the colon and the inferior mesenteric vessels ; 

 and its companion vein is situate below it. 



The length of the. common iliac ranges from less than half an inch (in 

 one case) to four inches and a half; but in the majority of instances it 

 varies between one inch and a halt' and three inches (Quain). 



