ILIAC ARTERIES. 361 



§ 973. Divisions cf the Aorta abdominalis (Fig. 101, B). — Expo- 

 sure and Disseciion. — Draw the urocystis (Fig. 101) caudo-ven- 

 trad ; press the contents of the rectum cephalad ; doubly ligate and 

 cut it opposite the neck of the urocystis. Cut the mesocolon 

 (§ 726) and mesentery near their attachment to the intestine as far 

 cephalad as the duodenum ; then cut the small Intestine at the cau- 

 dal end of the duodenum, and throw the intestines away. If the 

 remaining part of the rectum is washed out with a solution of ferric 

 sulphate (copperas) by introducing the canula of the syringe into 

 the anus, the unpleasant odor will be avoided. If the urocystis 

 contains urine, it should be pressed out through the urethra, or a 

 slit may be cut in it. 



In demonstrating the vessels, employ the forceps and tracer 

 mostly ; but use the scissors when it is necessary to remove any 

 tough masses. 



(A) A. iliaca externa (Fig. 101, B). — This passes obliquely cau- 

 dad, penetrates the abdominal wall dorsad of PouparV s ligament, 

 and reaches the cephalic side of the meros where it is called the 

 femoral artery. Just before the A. iliaca externa leaves the abdo- 

 men, it gives off a large branch from its mesal aspect. This branch 

 supplies the A. epigastrica (Fig. 101), then penetrates the abdomen 

 near the symphysis pubis, and sends branches to the skin in the 

 pubic region, but is mainly distributed to the muscles on the ce- 

 phalic and ventral aspects of the proximal end of the meros. The 

 human homologue of this artery has not yet been satisfactorily 

 determined. 



(B) A. iliaca interna (Fig. 101, B). — This arises from the aorta 

 about 1 cm. caudad of the origin of the preceding. It passes 

 obliquely caudad within the pelvis and dorsad of the pubis. A 

 short distance from its origin the A. msicalis superior (Fig. 101) 

 is given off from its ventral surface. This small vessel is the rem- 

 nant of the A. Jiypogastrlca of the foetus. It occasionally arises 

 from the aorta. 



The A. iliaca interna supplies most of tlie pelvic viscera entirely and furnishes part 

 of the blood supply to the innominate and meral regions. 



(C) A. sacra media, az. (Fig. 101, B). — The aorta is continued to the tail by this small 

 mesal artery, which passes through the arches formed by the chevron bones (§ 465). 



It will be seen by comparing the figure of the cat with that of man (Quain, A, I, 281, 

 Gray, A, 321), that in the cat thero is no common iliac as in man, but each iliac is a 

 branch of the aorta. 



