180 EQUINE ANATOMY. 



and the circumflex iliac running at a right angle out- 

 wardly to divide into anterior and posterior branches, 

 ramifying in the abdominal muscles. 



Internal iliac ob pelvic trunk. — Extends from 

 the last lumbar vertebrae downv^ards, outwards and 

 backwards to the in sertio n of the small psoas, where 

 it terminates by the obturator and the iliaco-f emoral . 

 Its collateral branches are : 



1. Umbilical — Almost entirely obliterated in the 

 adult, and found extending to the fundus of the 

 bladder, placed in the free border of its lateral liga- 

 ments. 



2. Internal pudic. — In the male ; running back- 

 wards along the superior border of the internal obtu- 

 rator muscle, into the pelvic cavity to the ischial arch, 

 where it terminates^ the bulb of the urethra. Its 

 principal collaterals are the vesico-prostatic, which 

 ramifies iti the bladder, and the vesicula seminalis. 

 In the female, it ends in the vagina by rectal, vulvar, 

 vaginal and bulbous branches ; its principal collateral 

 is the vaginal artery. 



3. Sub-sacral or lateral sacral. — Runs back- 

 wards under the sub-sacral foramen to the posterior 

 extremity of the sacrum, where it ends by the ischia- 

 tic and lateral coccygeal after furnishing collaterals to 

 the surrounding parts and four spinal branches. 



