130 GLANDS. 



Its internal surface sends innumerable delicate pro- 

 cesses, or trabeculse, into the interior of the organ, 

 which traverse its parenchyma, ' and become ulti- 

 mately continuous with the connecting tissue which 

 accompanies its vessels to their extreme ramifications. 



The parenchyma of the gland consists of an aggre- 

 gation of little granules, one-fourth to one- half of a 

 line in diameter, of a yellowish-brown color, and 

 darker centrally than on the surface. This color 

 varies considerably, for it depends upon the amount 

 of blood in the ramifications of the portal vein, and 

 in those of the hepatic vein, and also upon the degree 

 of fatty infiltration which exists in the hepatic cells. 

 In the human liver the outlines of these granules, 

 called also acini or lobules, are rather indistinct ; 

 but in the hog it is different ; here each lobule forms 

 a little polygon, entirely independent of its neighbors, 

 and presenting a very distinct outline. 



Each lobule of the liver represents, in its structure, 

 a miniature of the whole organ ; it will suffice there- 

 fore to study one of them thoroughly, in order to get 

 an exact idea of the histology of the gland. In each 

 lobule we find : 1st, a mass of hepatic cells ; 2d, the 

 terminal ramifications of the venae portae and of the 

 hepatic veins ; 3d, the biliary apparatus, consisting of 

 the radicles of the hepatic duct, and the terminal 

 branches of the hepatic artery. 



The cells are of two sorts : the one, which consti- 

 tutes pretty much the whole epithelial mass, are large 

 and irregular polygons, jVth of a line in diameter, 

 with nuclei almost always infiltrated with fat, and 

 contents consisting of free oil-globules, and a large 



