HEPATIC VEINS IN THE HORSE. 61 



that taken by the ramifications of the hepatic artery and the 

 ramifications of the portal vein. The trunk of the hepatic 

 artery and the trunk of the portal vein are seen entering the 

 liver on its concave surface at the same point where the trunk 

 of the hepatic duct comes forth. The nerves of the liver enter 

 at the same point, and the lymphatic vessels come out from 

 the organ there. All these several vessels, nerves, and duct, 

 are here surrounded by a sheath of areolar tissue, named the 

 capsule of Glisson, which is continuous with the fibrous cover- 

 ing of the liver, and which proceeds into the interior of the 

 liver, constituting a canal ramified along with the ramifications 

 of the vessels, nerves, and ducts so as to form what are named 

 the portal canals, spread everywhere throughout the liver, co- 

 extensively with the vessels and ducts. Thus, of the five kinds 

 of vessels found in the liver namely, the hepatic artery, the 

 portal vein, the hepatic duct, the lymphatic vessels, and the 

 hepatic veins the last alone are excluded from the portal 

 canal formed by the capsule of Glisson. These last vessels 

 namely, the hepatic veins, two or three in number are very 

 large veins, as their name in human anatomy indicates ; for 

 they are called the vence cavce hepaticce, not because they end 

 in the vena cava of the abdomen, but because of their great 

 size. Their great size requires explanation ; for while it is a 

 rule of the animal system that systemic veins are much larger 

 than the corresponding arteries, it is remarked that this rule 

 is less exemplified in the case of secreting organs than in parts 

 which do not secrete, and therefore that it might be expected 

 that in the instance of a gland supplying so large a secretion 

 as the bile, the veins would little exceed the correspond- 

 ing artery in size. The great size of the hepatic veins is 

 owing to the peculiarity of the circulation in the liver ; for 

 these veins have two distinct supplies of blood, one from the 

 hepatic artery, the other from the portal vein, while the blood 



