THE INTERNAL PUDIC ARTERY. 477 



found to occur much more frequently in the embryo and young child than in the adult 

 (Jastschinski). 



When the obturator artery arises from the epigastric, it turns backwards into the pelvis to 

 reach the canal at the upper part of the thyroid foramen ; and in this course it is necessarily 

 close to the femoral ring, the opening situated at the inner side of the external iliac vein, 

 through which hernial protrusions descend from the abdomen into the thigh. In about six- 

 tenths of such cases the artery turns backwards close to the external iliac vein, and therefore 

 on the outer side of the femoral ring ; in three-tenths it passes backwards across the ring ; 

 and in the remaining one-tenth it is directed at first inwards and then arches backwards on 

 the inner side of the ring. Its relation to the femoral ring is in some measure dependent 

 upon the spot at which it leaves the epigastric artery, for when it arises from the transverse 

 part of that vessel it usually passes backwards at once to gain the obturator canal, but if it 

 arises from the epigastric after the latter has turned upwards, the obturator artery descends 

 forming an arch and occupies a more internal position (Jastschinski). The position on the 

 inner side of the ring is more frequent in males than females. 



The anastomosis which normally exists between the pubic branches of the obturator and 

 epigastric arteries explains the nature of the change which takes place when the origin 

 of the obturator artery is transferred from the one place to the other. In such cases one of 

 the anastomosing vessels may be supposed to have become enlarged, and the posterior or proper 

 root of the obturator artery to have remained undeveloped or to have become obliterated in a 

 proportionate degree. 



The obturator artery has also been seen to arise from the upper part of the femoral, either 

 alone or in conjunction with the internal circumflex artery, in which case it arches back- 

 wards over the superior ramus of the pubis, and through the femoral ring, to reach the thyroid 

 foramen. 



In a few cases the obturator artery has been observed giving off the epigastric artery, an 

 accessory pudic artery (within the pelvis), or the dorsal artery of the penis (in the thyroid 

 foramen). 



6. The internal pudic artery (iv), one of the terminal branches of the 

 anterior division of the internal iliac, is distributed to the perineum and the 

 external organs of generation. The following description of the artery has reference 

 to its arrangement in the male, and the differences which it presents in the female 

 will be afterwards pointed out. 



From its origin in front of the pyriformis muscle, the pudic artery descends 

 along with the sciatic artery, and leaves the pelvis by the lower part of the great 

 sacro-sciatic foramen. Then curving gradually forwards, it crosses over the ischial 

 spine and passes through the small sacro-sciatic foramen into the posterior division 

 of the perineal space, where it lies along the outer wall of the ischio-rectal fossa, 

 being placed from an inch to an inch and a half above the lower margin of 

 the ischial tuberosity. Continuing its course forwards, it gradually approaches the 

 margin of the ischial ramus, penetrates the base of the triangular ligament, and 

 runs between the layers of that structure to near the apex of the subpubic arch. 

 Close to the inferior ramus of the pubis it ends under cover of the crus penis by divid- 

 ing into the artery of the corpus cavernosum and the dorsal artery of the penis. The 

 pudic artery is accompanied throughout its course by the veins of the same name. 



Within the pelvis, the pudic artery rests against the rectum internally, and the 

 sacral plexus of nerves intervenes between it and the pyriformis muscle. Over the 

 ischial spine, the artery is covered by the gluteus maximus muscle, and the pudic 

 nerve lies to its inner side. In the ischio-rectal fossa, the artery is contained in the 

 substance of the obturator fascia, the dorsal nerve of the penis being above, and the 

 perineal division of the pudic nerve below it ; and between the layers of the 

 triangular ligament, it is embedded in the tendinous origin of the constrictor 

 urethras muscle, the dorsal nerve of the penis taking a similar course, but being 

 more deeply placed. 



Branches. From the part of the artery within the pelvis small offsets proceed to 

 the obturator internus, pyriformis, and coccygeus muscles. As the artery crosses 

 the ischial spine it gives off branches to the adjacent part of the gluteus maximus, 



