THE ALIMENTARY CANAL AND ITS APPENDAGES 461 



important influence on the general nutritional processes of the 

 Body (Chap. XXX). 



The Blood-Vessels of Alimentary Canal, Liver, Spleen, and 

 Pancreas. The portal vein (Vp, Fig. 135) has already been referred 

 to as differing from all other veins in that it not only receives blood 

 from a system of capillaries but ends in a second set of capillaries, 

 which lie in the liver. The quantity of blood brought to supply 

 the hepatic capillaries by the hepatic artery is in fact much less than 

 that brought by the portal vein. The stomach, the intestines, the 

 pancreas, and the spleen are supplied with arterial blood from 

 three great branches of the aorta. The most anterior of these, the 

 celiac axis, springs from the aorta close beneath the diaphragm and 

 divides into the hepatic artery, splenic artery, and arteries for the 

 stomach; some of these divisions may be seen in Fig. 135. The 

 pancreas is supplied partly from the hepatic, partly from the 

 splenic artery. The two other branches (superior and inferior 

 mesenteric artery) are given off from the aorta lower down in the 

 abdominal cavity; the former (5, Fig. 135) supplies the small in- 

 testine and half of the large, the latter the remainder of the large. 

 The blood passing through all these arteries becomes venous in the 

 capillaries of the organs they supply, and is gathered into corre- 

 sponding veins (Fig. 135) which unite near the liver to form the 

 portal vein. The further course of the blood carried to the liver 

 (partly arterial from the hepatic artery, partly venous from the 

 portal system) has been described already (p. 335). 



