BRANCHES OF THE INTERNAL ILIAC. 565 



below the acetabulum, and supplies the muscles attached to the tuberosity of the 

 ischium and anastomoses with the sciatic artery. It sends a branch to the hip- 

 joint through the cotyloid notch, which ramifies on the round ligament as far as 

 the head of the femur. 



Peculiarities. In two out of every three cases the obturator arises from the internal iliac ; 

 in one case in three and a half from the epigastric ; and in about one in seventy-two cases by 

 two roots from both vessels. It arises in about the same proportion from the external iliac 

 artery. The origin of the obturator from the epigastric is not commonly found on both sides 

 of the same body. 



When the obturator artery arises at the front of the pelvis from the epigastric, it descends 

 almost vertically to the upper part of the obturator foramen. The artery in this course usually 

 lies in contact with the external iliac vein and on the outer side of the femoral ring (Fig. 314, 'A) ; 

 in such cases it would not be endangered in the operation for femoral hernia. Occasionally, 

 however, it curves inward along the free margin of Gimbernat's ligament (Fig. 314, B), and 



if 



FIG. 314. Variations in origin and course of obturator artery. 



under such circumstances would almost completely encircle the neck of a hernial sac (supposing 

 a hernia to exist in such a case), and would be in great danger of being wounded if an operation 

 was performed. 



The internal pudic is the smaller of the two terminal branches of the anterior 

 trunk of the internal iliac, and supplies the external organs of generation. 

 Though the course of the artery is the same in the two sexes, the vessel is much 

 smaller in the female than in the male, and the distribution of its branches 

 somewhat different. The description of its arrangement in the male will first be 

 given, and subsequently the differences which it presents in the female will be 

 mentioned. 



The Internal Pudic Artery in the Male passes downward and outward to the 

 lower border of the great sacro-sciatic foramen, and emerges from the pelvis 

 between the Pyriformis and Coccygeus muscles : it then crosses the spine of the 

 ischium and re-enters the pelvis through the lesser sacro-sciatic foramen. The 

 artery now crosses the Obturator interims muscle along the outer wall of the ischio- 

 rectal fossa, being situated about an inch and a half above the lower margin of the 

 ischial tuberosity. It is here contained in a sheath of the obturator fascia, and 

 gradually approaches the margin of the ramus of the ischium, along which it passes 

 forward and upward, pierces the base of the superficial layer of the triangular 

 ligament of the urethra, and runs forward along the inner margin of the ramus of 

 the os pubis, and divides into its two terminal branches, the dorsal artery of the 

 [tents and the artery of the corpus cavernosum. ' 



Relations. In the first part of its course, within the pelvis, it lies in front of 

 the Pyriformis muscle and sacral plexus of nerves, and the sciatic artery, and 

 on the outer side of the rectum (on the left side). As it crosses the spine of 

 the ischium it is covered by the Gluteus maximus and overlapped by the great 

 sacro-sciatic ligament. Here the obturator nerve lies to the inner side and the 

 nerve to the Obturator internus to the outer side of the vessel. In the pelvis it 

 lies on the outer side of the ischio-rectal fossa, upon the surface of the Obturator 

 internus muscle, contained in a fibrous canal (canal of Alcock) formed by the 

 splitting of the obturator fascia. It is accompanied by the pudic veins and the 

 pudic nerve. 



