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the kidney, and is visible on its ventral surface. We have 
said that the kidney at its anterior extremity is divided 
into two horns, which reach forward towards 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 vessels 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 celiac and cceliaco-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. Commonly 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; (3) 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 distribution in the liver varies ; 
five such trunks are represented in fig. 21, cut off close to 
the liver surface (Vp.) 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 efferent vessels of the 
hepatic portal system are the two large paired hepatic 
—_—s 
