THE VEINS 641 



thro(^ superficial plantar metatarsal arteries. These vessels unite with three deep 

 plantar metatarsal arteries which descend from the proximal plantar arch and with 

 branches from the dorsul metatarsal arteries. From these anastomoses four digital 

 arteries result; of these, the central two have a common digital trunk. 



The popliteal and posterior femoral arteries present nothing of special interest. 



The posterior tibial artery is small, being replaced largely by the saphenous. 

 It supplies twigs to tlie flexor muscles at the upper part of the leg. 



The anterior tibial artery descends on the anterior face of the tibia and tarsus 

 and is continued as th(> perforating metatarsal artery, which passes through the 

 upper part of the space between the second and third metatarsal bones and concurs 

 with the plantar branches of the saphenous in the formation of the plantar arch. 

 Besides muscular and articular branches, the anterior tibial supplies the external 

 or fifth dorsal metatarsal artery for the outer side of the fifth digit. At the proximal 

 part of the metatarsus it gives off three deep dorsal metatarsal arteries which 

 descend in the intervals between the metatarsal bones and concur with the super- 

 ficial dorsal and the plantar arteries in the formation of the digital arteries. The 

 latter resemble in general arrangement the corresponding arteries of the thoracic 

 limb. 



The internal iliac artery (Fig. 491) runs l)ackward and a little outward across 

 the ilio-psoas, and on reaching the ilium divides into parietal and visceral branches. 

 The parietal branch is the larger. It runs backward on the lateral wall of the 

 pelvis, passes out through the lesser sciatic notch, and breaks up into branches 

 which supply the muscles in this region like the posterior gluteal (or ischiatic) artery 

 of the horse. It gives off the following branches: (1) The ilio-lumbar artery 

 passes outward between the ilio-psoas and the shaft of the ilium and ramifies 

 in the gluteus medius, giving branches to the ilio-psoas and tensor fascia? lata; 

 it may arise from the internal iliac. (2) The anterior gluteal artery passes out 

 Ijehind the posterior su})erior spine of the ilium and supplies branches to the glutei, 



(3) Muscular branches go to the obturator internus, coccygeus, and retractor ani. 



(4) The lateral coccygeal artery (A. caudalis lateralis superficialis) passes back at first 

 on the outer face of tlie coccygeus and continues l)eneath the skin along the side of 

 the tail. The visceral branch or internal pudic artery passes l)ack below the parietal 

 branch on the lateral face of the rectum, retractor ani, and coccygeus. Its chief 

 collateral branches are: (1) The umbilical artery, which pursues a flexuous course 

 and supplies twigs to the bladder, ureter, and vas deferens. In the bitch it gives 

 off a large uterine artery which ramifies chiefly in the body and neck of the utt^rus 

 and the vagina and anastomoses with the utero-ovarian. (2) The middle haemor- 

 rhoidal artery arises near the ischial arch, passes upward and forward on the lateral 

 surface of the rectum, gains its dorsal surface and anastomoses wdth the posterior 

 mesenteric; it supjilies the rectum and the anus, together with its muscles and 

 glands. (3) A small perineal artery is detached to the pc^rineum. In the male the 

 trunk turns around the ischial arch as the artery of the penis (A. penis). This 

 vessel, after giving off the deep artery of the penis (A. profunda penis), which 

 supplies the artery of the bulb (A. l)ul])i urethrtie) and enters the corpus cavernosum, 

 is continued as the dorsal artery of the penis (A. dorsalis penis) along the dorsum 

 penis. In the female the terminal l)ranches of the trunk go to the vulva, vestibular 

 bulb, and clitoris. 



The Veins 



The arrangement of the veins is, of course, correlated in general with the arterial 

 system, but a few si)ecial features are worthy of mention. 



The anterior vena cava is formed by the junction of short right and left 

 brachiocephalic (or subclavian) veins, and each of the latter results from the con- 

 fluence of jugular and brachial veins. 

 41 



