THE VEINS 641 



three superficial plantar metatarsal arteries. Tliose vessels unite with three deep 

 plantar metatarsal arteries which descend from tlu^ jiroximal plantar arch and with 

 brandies from tlie tlorsal metatarsal arteries. From these anastomoses four digital 

 arteries n^sult; 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 the tlcxor nnisdes 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 the perforating metatarsal artery, which passes through the 

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

 with the i^lantar branches of tlie saj^henous 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 l)etwe(>n tlie metatarsal bones and concur witii 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. 401) runs l)ackward and a little outward across 

 the ilio-psoas, and on reaching the ilium divides into jiarietal 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 branch(\s: (1) The ilio-lumbar artery 

 jKisses outward between the ilio-jisoas and the shaft of the ilium and ramifies 

 in the gluteus medius, giving l)ranches to the ilio-psoas and tensor fascia? latse; 

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

 behind the posterior suix'rior spine of the ilium and supplies branches to the glutei. 



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



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

 on the outer face of the coccygeus and continues beneath the skin along the side of 

 the tail. The visceral branch or internal pudic artery passes back below the parietal 

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

 collateral branches are: (1) Th(> 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 w^hich ramifies chiefly in the body and neck of the uterus 

 and the vagina and anastomos(>s with the utero-ovarian. (2) The middle haemor- 

 rhoidal artery arises near the ischial arch, passes upward and forw^ard on the lateral 

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

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

 glands. (3) A small perineal artery is detached to the perineum. In the male the 

 trunk turns around the iscliial 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. bul])i urethrae) 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 branches of the trunk go to the vulva, vestibular 

 iDulb, and clitoris. 



The Veins 



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

 system, but a few special features are worthy of mention. 



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

 brachiocephalic (or sul^clavian) veins, and each of the latter results from the con- 

 fluence of jugular and brachial veins. 

 41 



