LIVER 



28l 



extends through the connective tissue around the gall bladder, so that the 

 cystic branch of the adult appears to be the main vessel in the young em- 

 bryo. Still later, as the connective tissue which surrounds the structures 

 at the porta gradually extends into the liver around the branches of the 

 hepatic duct and portal vein, the hepatic artery sends branches in with it, 

 and they form capillaries which empty into the adjacent portal sinusoids. 

 Branches of the artery ramify also in the connective tissue capsule around 

 the entire liver. The quantity of blood supplied to the liver by the artery 

 always remains much smaller than that brought in by the portal vein, and 

 it is distributed to the connective tissue. There are no vessels between 

 the hepatic cells other than the "capilliform sinusoids" derived directly 

 from the embryonic lacunae of the vitelline veins. 



MICROSCOPIC STRUCTURE. 



Lobules. A section of the embryonic liver, or of the liver at birth, shows 

 great areas of anastomosing trabeculae, with intervening sinusoids and oc- 

 casionally a larger vein. In the adult pig the hepatic tissue is arranged in 

 lobules bounded by connective tissue (Fig. 276). These subdivisions were 



FIG. 276. LIVER OF A PIG. (Radasch.) 



The lobules have artificially shrunken from the interlobular tissue, a; b, bile duct; c, hepatic artery; 

 d, interlobular vein (a branch of the portal); e, trabeculse; f, central vein. 



first recognized in the liver of the pig (Wepfer, 1664), and in 1666 Malpighi 

 made the general statement that the entire liver is composed of a multi- 

 plicity of lobules. In the dog Mall finds that the lobules are short cylinders 



