THE y4RTERlES. 307 



between the centra of the vertebrae and the muscles of the 

 dorsal region, and send one main branch laterad, the other 

 dorsad; both supply the dorsal muscles. From the dorsal 

 branch small arteries pass into the vertebral canal to join the 

 anterior spinal artery. 



9. A. iliaca externa (Fig. 126, /'). — The external iliac 

 artery passes obliquely caudad from the aorta, lying ventrad of 

 the common iliac vein and against the medial surface of the 

 psoas minor muscle. It passes onto the ventral surface of this 

 and the iliopsoas and at the same time reaches the tendon of the 

 abdominal muscles ; through a small opening in this tendon 

 lying ventrocaudad of that for the iliopsoas, it leaves the 

 abdominal cavity. On its emergence from the abdominal 

 cavity onto the medial surface of the thigh it receives the name 

 A. femoralis (7//). The branches of the external iliac artery 

 are described below (page 309). 



10. A. hypogastrica (or iliaca interna) (Fig. 126, /). — The 

 hypogastric or internal iliac arteries are given off from the aorta 

 usually within a centimeter caudad of the external iliac. Each 

 passes caudolaterad, lying on the medial side of the common 

 iliac vein, and divides into branches which supply the struc- 

 tures within the pelvis and the muscles about the pelvic wall. 

 There is much variation in the origin and relations of the 

 branches of this artery. The following seems to be a very 

 common arrangement: A very short distance from the origin 

 the umbilical artery (;/) is given off. The hypogastric artery 

 then extends two or three centimeters and gives off A. 

 glutea superior (/), which passes at once to the pelvic 

 wall. A little farther caudad the hypogastric divides into the 

 middle hemorrhoidal (;-), to the rectum, and the glutea in- 

 ferior (</), which passes out of the pelvis. 



Branches of the hypogastric arter}^ : 



a. A. umbilicalis (Fig. 126, ?/). — This small artery arises 

 from the hypogastric about one centimeter from the beginning 

 of the latter, and passes ventrad to the bladder. Here it divides 

 into two branches — the superior vesical to the sides of the 

 bladder, the inferior vesical to the neck of the bladder and the 

 urethra. 



