TEE INTERNAL ILIAC ARTERIES. 543 



course backward and downward, accompanied by a satellite vein and nerve, 

 passes beween the peritoneum and ilium in following the inferior border 

 of the internal obturator muscle, and finally insinuates itself beneath 'that 

 muscle to make its exit from the pelvis by creeping through the oval (obtu- 

 rator) foramen, after furnishing a constant vesical twig. Placed between the 

 external obturator muscle and the inferior face of the ischium, it separates 

 into several _ branches, the majority of which descend into the internal 

 crural and ischio-tibial muscles (long or external vastus, and the semi- 

 membranosis and semiteudinosis), anastomosing with the ultimate divisions 

 of the ischiatic and deep femoral arteries. Among these branches there 

 are two or three which go to the roots of the penis, and enter the erectile 

 tissue of the cavernous body ; one of them, more important than the others by 

 its volume, is designated the artery of the corpus^cavernosum. 



Aeteet of the Corpus Caverhosum (Fig. 275, 20). — This vessel 

 creeps on the inferior face of the ischium, backwards and inwards, reaches 

 the crus penis, and pierces it by several branches, after supplying some 

 muscular divisions and the posterior dorsal artery of the penis. 



The latter is situated on the dorsal margin of the penis, passes forward 

 between the two ligaments attaching that organ to the symphysis pubis, 

 and proceeds to anastomose with the posterior branch of the anterior dorsal 

 artery (Fig. 275, 21.) 



7. niaco-femoral Artery (Figs. 275, 18 ; 277, 9.) 



Noticed as one of the terminal branches of the pelvic trunk, the iliaco- 

 femoral artery only exists as a vessel of a certain volume in Solipeds. In 

 other animals, as in Man, it is merely an insignificant and innominate branch 

 of the obturator artery. It proceeds outside the tendon of the small psoas 

 muscle, between the iliacus and the neck of the ilium, which it passes round 

 obliquely, above the origin of the anterior rectus muscle, to descend on the 

 external side of the latter, and plunge into the mass of the patellar muscles, 

 entering them between the anterior rectus and vastus externus, after sending 

 out some branches to the psoas, gluteal, and muscles of the fascia lata, 



DIFFERENTIAL CHAKACTEES OP THE INTEENAL ILIAC ARTERIES IN OTHER THAN SOLTPED 



ANIMALS. 



1. Internal Iliac Arteries of Ruminants. 



The terminal extremity of the aorta, after giving off the external iliac arteries, 

 bifurcates to constitute the pelvic trunks, and in the angle of bifurcation throws out a 

 very large branch — the sacra media — from which emanate the arteries of the tail. 

 This, however, is not the only important peculiarity to be noted in the disposition of the 

 pelvic arteries. The internal iliac artery emits at its origm a very short, but very large 

 branch, which divides to form the umbilical artery, and an enormous uterine artery, that 

 supplants, to a great extent, the utero-ovarian artery ; it is then directed backwards, on 

 the internal face of the great ischiatic ligament, crossing the direction of the liimbo-sacral 

 plexus. In its course it furnishes branches resembling the iliaco-muscular, the gluteal, 

 and the ischiatic, and is continued about the middle of the pelvis by the internal pudia 

 artery, which terminates by forming the dorsal artery of the clitoris, after distributing 

 branches to the rectum and the genito-urinary organs lodged in the pelvic cavity. 



It will be seen from this descriptioii — which refers only to female animals, but is 

 easily applicable to males — that no mention is made of an iliaco-femoral or obturator 

 artery. This is because these two vessels are entirely absent in the Sheep, and the last, 

 though present in the larger Euminants, is yet in a very rudimentary state, both being 

 supplemented by the deep femoral, whose dimensions are considerable. Neither is 

 i\^ lateral sacral or svbsacral artery described, as it is also wanting, its ischiatic branch 

 coming directly from the pelvic trunk, and its coccygeal divisions being supplied by tha 

 middle sacral artery. 



