16 



THE FUR SEALS OP THE PRIBTLOF ISLANDS. 



ofll an fdlanfoic vensel a short distance back of its origiu, whicli runs ventrally and 

 forward along the side of the urinary bladder to the anterior end of the same, where 

 the right and left vessels fuse with the urachis. They are hollow trunks in the adult 

 and contain blood. Back of the head of the ilium the internal iliac artery gives off" a 

 small sciatic branch. Other branches are given oft" to the pelvic organs. 



The systemic veins. — The vena cava anterior is formed by the union of the riijht 



Fio. f).— Veins of foro limb of pup, onelialf natural size. 



and left innominate trunks. These run transversely across the anterior part of the 

 thoracic cavity, and hence with the vena cava anterior they make a T. shaped vessel. 

 A short distance in front of the auricle the vena cava receives the azygos vein, which 

 is joined near its termination by two smaller veins from the neighboring muscles. 

 Just a little back of its anterior end it receives ventrally the internal mammari/ vein. 

 This is formed by the union of four vessels, two large inner ones and two smaller 



