18 THE PUR SEALS OF THE PKIBILOF ISLANDS. 



internal iliac veins. The former is composed of the femoral vein from the hind limb, 

 where it is formed by the union pf numerous trunks, of which the long saphenous is 

 the largest, and of another vein beginning on the plantar surface of the hind flipper 

 and tnen running forward superficially along the inside of the tibia and across the 

 upper end of the thigh into the abdominal cavity. Where the latter vein pierces the 

 peritoneum it receives the two epigastric veins of the same side. These lie one on 

 -each side of the epigastric artery. The external iliac receives a vein from the 

 dorsal wall of the abdominal cavity. The internal iliac is formed at the posterior 

 end of the pelvic cavity by the union of veins in that region. It increases as it 

 passes forward along the dorsal wall of the pelvis by receiving veins along its course. 

 In the posterior part of the abdominal cavity the two internal iliacs are united by a 

 transverse commissure, into which a small median caudal and sacral, vein empties. 

 Beyond this the internal iliac veins diverge and each unites with the corresponding 

 external iliac. The external and internal iliac veins are connected also by a com- 

 missure, joining the latter just back of that between it and its fellow and the former 

 a short distance back of its anterior end. A lateral vein from the pelvic organs 

 empties into this commissure near its inner end. 



The veins of the reproductive glands join the vena cava just back of the renal 

 veins. 



The portal vein. — The portal vein remains throughout life connected with the 

 umbilicus by a hollow vitelline vein, and with the vena cava inferior just where this 

 vessel pierces the diaphragm by a likewise hollow ductus venosus. Both of these unite 

 with the portal vein between its two branches, going to the anterior right and left 

 lobes of the liver, 



THE KEPBODtrOTIVB ORGANS. 



The male organs. — The testis is elongatedly oval, with the dorsal border a little 

 concave. The epididymis begins at the anterior end, goes backward along the concave 

 side, enlarging at the same time, and then at the posterior end of the testis turns 

 forward on the inner side of the first part. It then again decreases in size and 

 becomes the but slightly convoluted vas deferens. 



The scrotum is very long, but is entirely shut off from the abdominal cavity. By 

 means of the extremely elongated cremaster muscles, however, each pouch can be 

 drawn up far under the skin and fat of the pelvic region of the body close to the 

 ventral pelvic muscles. Each cremaster arises from the ventral surface of the 

 vertebra, just back of the posterior border of the kidneys, and is inserted along 

 the entire length of the corresponding scrotal sac. 



The upper part of the urethra is enlarged and its walls are greatly thickened and 

 glandular. The vasa deferentia unite into a common tube a short distance back of 

 the neck of the bladder, which immediately enters the glandular part of the urethra 

 and open within on a flabby papilla. 



The spermatic veins join the vena cava just back of the renal vessels. Each 

 is formed by numerous veins near the surface of the testis, which converge and unite 

 at its anterior end. Except near the vena cava the spermatic veins are very much 

 convoluted, and each is surrounded by an inner layer of spongy tissue and by an 

 outer membranous sheath. 



The penis is composed of two large corpora cavernosa having their distal halves 

 ossified, and of a membranous corpus spongiosum and glans. The penis of a bull is from 



