I 0-2 



the kidney, and is visible on its ventral snrface. AVe have 

 said that the kidney at its anterior extremity is divided 

 into two horns, which reach forwaid toAvards the heart. 

 The right cardinal vein emerges from the kidney- through 

 the right horn and enters the posterior side of the right 

 precaval vein. The left cardinal (as in the Cod) is a short 

 vessel which begins at about the anterior third of the 

 kidney, traverses the left horn, and enters the posterior 

 side of the left precaval vein. The two cardinals do not 

 apparently anastomose with each other. 



The Hepatic Portal System. — The afferent ve-ssels of 

 this system are the portal veins carrying the blood from 

 the stomach, intestine and spleen. The smaller factors of 

 this system have much the same course and distribution 

 as the branches of the coeliac and coeliaco-mesenteric 

 arteries. They do not, however, unite to form a single 

 hepatic portal vein, but enter the liver as a variable 

 number of separate portal veins. Coninionly there are 



(1) a trunk receiving the blood from the spleen and the 

 greater portion of the intestine, and anastomosing with 



(2) a vein receiving the blood returned from the loops of 

 the intestine posterior to the pylorus ; (-J) a smaller vessel 

 draining the region of the pylorus, and (4) a vein coming 

 from the stomach. These vessels enter the internal sur- 

 face of the liver principally on the larger left lobe, and 

 run for some distance parallel to and immediately beneath 

 the surface, so that their ramifications can be easily traced. 

 Their precise number and tlistribution in the liver varies ; 

 hve such trunks are represented in hg. 21, cut oif close to 

 the liver surface (F/^-) The apparent calibre of the intes- 

 tinal veins, and to a less extent the arteries also, is 

 increased by the presence of the perivascular glandular 

 tissue referred to above. The eft'erent vessels of the 

 hepatic portal system are the two large paired hepatic 



