THE VEINS 721 



correspond to the arteries of which they are sateUites. The renal veins are large 

 and thick-walled; they run obliquely forward and join the vena cava at an acute 

 angle. The left one is much the longer. 



Two middle sacral veins usually accompany the artery. 



The veins of the mammary glands deserve special notice. They converge to 

 a venous circle at the base of the udder, which is drained chiefly by two pairs of 

 veins. The subcutaneous abdominal vein (anterior mammary or "milk" vein) 

 is very large in animals of the dairy breeds, and its course along the ventral wall of 

 the abdomen is easily followed. It is usually flexuous. It emerges at the anterior 

 border of the udder about two or three inches (ca. 5-S cm.) from the hnea alba, 

 runs forward (deviating a little outward), dips under the cutaneus, passes through 

 a foramen in the abdominal wall about a handbreadth from the median plane, and 

 joins the internal thoracic vein. The two veins are connected by a transverse 

 anastomosis at the anterior border of the base of the udder, and each anastomoses 

 behind with a branch of the external pudic vein. The external pudic vein (middle 

 mammary vein) is also of considerable size. It ascends in the inguinal canal as a 

 satellite of the artery and joins the external iliac vein. The right and left veins 

 are connected at the posterior border of the base of the udder by a large transverse 

 branch. From the latter arises the perineal vein (posterior mammary vein), 

 which runs medially upward and backward to the perineui^, turns around the 

 ischial arch, and joins the internal pudic vein. Two veins maj' present. In the 

 male these veins are relatively small. 



The deep veins of the thigh and leg resemble those of the horse, but there is 

 no recurrent tibial vein. 



The saphenous vein is much smaller than in the horse. It may be regarded 

 chiefly as the upward continuation of the medial tarsal vein, which arises from the 

 deep plantar arch. 



The recurrent tarsal vein^ is large. It is the upward continuation of the dorsal 

 metatarsal vein and anastomoses with the anterior tibial and saphenous veins. It 

 arises on the lateral face of the hock, ascends at first in front of the tendo Achillis, 

 then crosses the latter laterally, passes up between the biceps femoris and semi- 

 tendinosus, and joins the posterior femoral vein. 



There are three chief metatarsal veins. The large dorsal metatarsal vein 

 arises at the distal part of the metatarsus by the union of the dorsal digital vein 

 and a large branch from the venous arch above the sesamoids. It ascends super- 

 ficially between the long and lateral extensor tendons and may be regarded as being 

 continued in the leg by the recurrent tarsal vein; it also furnishes a large chief 

 radicle of the anterior tibial vein. The medial plantar metatarsal vein arises from 

 the venous arch above the fetlock, ascends between the medial border of the sus- 

 pensory ligament and the plantar surface of the metatarsal bone; it is connected 

 with the corresponding lateral vein at the proximal end of the metatarsus by a 

 transverse anastomosis, thus forming the deep plantar arch. From this the per- 

 forating tarsal vein passes through the vascular canal of the metatarsus and centro- 

 tarsal (as the perforating tarsal) and joins the anterior tibial vein. The lateral 

 plantar metatarsal vein pursues a similar course laterally, and is continued by the 

 lateral tarsal vein, which joins the recurrent tarsal vein above the hock. It passes 

 superficially over the lateral face of the hock and is continued by the recurrent tarsal 

 vein. 



The digital veins differ from those of the forelimb chiefly in that the dorsal 

 common vein is large and the plantar absent or small. 



The dorsal common digital vein arises at the distal part of the interdigital space by the union 

 of branches coming from the venous plexuses of each digit . It deviates outward at the fetlock and 

 joins the lateral digital vein to form the dorsal metatarsal vein. The medial digital vem ascends 



1 Also termed the external saphenous vein. 

 46 



