CHAPTER VIII 



THE BLOOD AND LYMPH VESSELS 



THE ARTERIES 



Synopsis of Origin, Distribution, and Anastomoses 



The Internal Iliac Artery. — Although chiefly concerned in the supply 

 of the walls of the pelvis and the contents of that cavity, this vessel is 

 described here, since some of its branches also contribute towards the 

 supply of parts of the hind limb. 



The vessel is one of the terminal divisions of the posterior aorta, 

 which divides beneath the fifth lumbar vertebra into two pairs of vessels, 

 one pair on either side. The members of each pair are the external and 

 internal iliacs. 



From the body of the fifth lumbar vertebra the internal iliac artery 

 takes a course which is obliquely backwards, downwards, and outwards. 

 It runs across the articulation formed between the sacrum and the last 

 lumbar vertebra, and then over the sacro-iliac articulation, where it 

 terminates near the insertion of the psoas parvus muscle by splitting 

 into three main divisions. Outwardly the internal iliac artery is related 

 to the common iliac vein, which separates it from the external iliac 

 artery. Inw^ardly it is related to the peritoneum. 



During its course the internal iliac artery gives off the following 

 collateral branches : 



I. The Umbilical Artery. — In the foetus this is a vessel of considerable 

 calibre, and through it the blood of the foetus passes to the placenta. In 



