628 THE ARTERIES. 



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 rectus femoris muscle, to descend on the external side of the latter, and 

 plunge into the mass of the patellar muscles, entering them between the rectus 

 femoris and vastus externus, after sending some branches to the psoas and gluteal 

 muscles, and tensor vaginae femoris. 



Differential Characters in the Internal Iliac Arteries of the other Animals. 

 1. Internal Iliac Arteries of Ruminants. 



Tlie terminal extremity of tlie aorta, after giving off the external iliac arteries, bifurcates 

 to constitute the internal iliacs, and in the augle of bifurcation tlirows out a very large branch 

 — the sacra media — from which emanate the arteries of the tail. This, however, i.s not the 

 only important peculiarity to be noted in tlie disposition of tl.e pelvic arteries. Tlie internal 

 iliac artery emits at its origin a very short, but very large brancli, which divides to form the 

 umbilical artery, and an enormous uterine artery, that supplants, to a gieat extent, the utero- 

 ovarian artery ; it is then directed backwards, on the internal face of the great tacro-sciatic 

 ligament, crossing the direction of the lumbo-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 pudic artery, which terminates by forming the dorsal artery of the 

 clitoris, after distributing branches to the rectum and the geuito-uriuary organs lodged in the 

 pelvic cavity. 



It will be seen frctm this description — which refers only to female animals, but is easily appli- 

 cable to males — tliat no mention is made of an iliaco-femoral or obturator artery. This is 

 because these two vessels are entirely absent in the Sheep, and tlie last, though present in the 

 larger Euminants, is yet in a very rudimentary state, botli lieing supplemented by the deep 

 femoral, the dimeiisious of which are considerable. Neither is tlie lateral sacral artery described, 

 as it is also absent, its ischiatic branch coming directly from the pelvic trunk, and its coccygeal 

 divisions being supplied by the middle sacral artery. 



2. Internal Iliac Arteries of the Pig. 



Two single branches, originating one above the other, arise from the extremity of the aorta, 

 between the two internal iliac arteries; one divides almost at once into two lateral brunches, 

 which go to right and left beneath the iliacus, and are the representatives of the iliaio muscular 

 arteries of the Horse ; the other, or sacra media, placed in the midd'le line, proceeds backwards 

 on the inferior face of the os sacrum, and constitutes the coccygeal arteries after giving off, at 

 about 1^ inches from its origin, two lateral branches, traces of the lateral sacral arteries, which 

 furnish the spinal ramuscules of the sacral region. 



The internal iliac artery, near its origin, sends off the umbilical artery, is directed back 

 towards the sacro-sciatic foramen, there detaches gluteal branches, and is prolonged beyond 

 the foramen to the external surface of the saero-sciatic ligament, in forming the internal pudic 

 artery. 



The latter emits, befoie leaving the pelvic cavity, a long hemorrhoidal artery, that creeps 

 back by the side of the rectum, to be distributed to the posterior extremity of that intestine 

 and the adjoining geni o-urinary organs. Outside the pelvis, it g'wes off some gbiteal branches, 

 the most considerable and posterior of which represent tlie ischiatic artery of Solipeds. It then 

 re-enters the cavity of the pelvi.s, and terminates at the base of the penis by forming the 

 cavernous and dorsal arteries of that organ. 



3. Internal Iliac Arteries of Carnivora. 



The internal iliac arteries in the Carnivora result from tlie bifurcation of an arterial trunk 

 that prolongs the aorta beyond the origin of the external iliacs, as far as the first intersacral 

 articulation. 



This pelvic trunk at first gives off the umbilical artery, which is remarkable for its small 

 calibre, and the flexuosities it describes before reaching the bladder. 



Tlicn the internal iliac artery courses for 1 or U inches behind, and to the inside of, the 

 pelvi-crural venous trunk, dividing into two branches at the entrance to the pelvis. 



One of these branches goes towards the viscera contained in the pelvic ca\ity ; this is the 

 inttrnal pudic artery. It passes backwards, turns round the ischial arch, and terminates in the 



