ANIMAL BIOLOGY. [Parti. 



unite in the middle line under the vertebrae. Each gives off a 

 vertebral artery (ver.). 



Traced backwards the aorta gives rise to a coeliac (cce. a.) and 

 an anterior mesenteric (a. m. a.), and sends an anterior renal (a. r. a.) 

 branch on each side to the front lobes of the kidney. The 

 femoral arteries (fern, a.) are not of great size. The ischiatic 

 arteries (isc. a.) are larger, and give off renal branches to the 

 second and third lobes of the kidney, and eventually become the 

 sciatic arteries (sc. a.). At the posterior end of the body the aorta 

 divides into four small vessels, the caudal to the tail (c.), the 

 posterior mesenteric (p. m. a.) to the rectum and cloaca, and the 

 paired internal iliacs (in. il.) to the roof of the pelvis. 



Turning now to the veins, the right auricle receives the two 

 precavals (r. and /. pc.) and the postcaval (pt. c.). Each precaval 

 receives as factors a large pectoral (pc. #.), a brachial (br. v.), 

 and a jugular (ju.). Traced forwards up the neck the two 

 jugulars curve round and unite in the middle line beneath the 

 head. The postcaval receives several large hepatic (he. v.) fac- 

 tors from the liver. Slightly further back it is formed by the 

 union of the two large iliac veins (il. v.), which receive afferent 

 renal veins (a.r. f , a.r.", a.r.'") from the three lobes of the kidney, 

 those from the more posterior lobes uniting into a common trunk. 

 Following the iliacs down, they are seen to be composed of a 

 large crural vein (cr. v.), and a hypogastric vein (hyp. v.) which 

 passes through the substance of the kidney and receives a small 

 sciatic vein (sc. v.). Posteriorly the hypogastrics receive internal 

 iliac veins from the roof of the pelvis. Further back they are 

 seen to arise from the division of a posterior mesenteric vein 

 (p. m. v.), which receives a small caudal vein near its point of 

 division. The posterior mesenteric vein returns blood from the 

 rectum and part of the small intestine. The blood in its 

 posterior (coccygeo-mesenteric) portion flows into the hypogas- 

 trics. That in its anterior (inferior mesenteric) portion joins 

 the portal vein, which also receives blood (1) by a gastro-duodenal 

 from the right side of the gizzard, the duodenum, and the last 

 loop of the small intestine, and (2) by the superior mesenteric 

 from the rest of the small intestine. 



