34 8 EFFERENT BILTAEY PASSAGES. [sect. l6l. 



rower gall-duct, and on the other, an artery which is likewise narrow, 

 and is surrounded along with them by an envelope of connective 

 tissue, the capsula Glissonii, as it is termed. In man, the hepatic 

 ducts ramify in an arborescent manner with the portal vein; they can 

 be exposed with the knife for a considerable extent inwards, and 

 can be traced with the microscope, in fresh and injected livers, as 

 far as the lobules. Before they pass to the lobules, the hepatic 

 ducts unite here and there by smaller branches ; but the anas- 

 tomoses of the small interlobular branches, coming from opposite 

 points, are very rare (Beale). From these interlobular ducts finer 

 branches are given off to the lobules, and, in the human subject 

 according to Beale, are connected together so as to form a lax net- 

 work of ducts, which is directly continuous with the lobular network 

 of liver-cells, as represented in fig. 150, after L. Beale, who first 



Fig. 150. 



Termination of a small interlobular duct in the pice's liver, and communication of its 

 smallest branches with the network of tubes containing liver-cells. 



succeeded in showing the manner in which these two structures 

 unite. The smallest ducts are lined with a single layer of very deli- 

 cate, flattened epithelial cells, and not wider than -j^^tli of an 

 inch ; therefore, they contrast remarkably with the tubes of the 

 secreting network, whose breadth is about y^^-th of an inch and 

 whose cells are nearly of the same size. 



All the hepatic ducts down to canals of o*i'" in diameter, 

 consist of a thick fibrous coat, of dense areolar tissue, with 

 numerous nuclei and elastic fibrils, and of a cylindrical epithelium 

 001"' in thickness, which, in ducts below 0-04'" to 005'" in dia- 

 meter, is gradually converted into a pavement epithelium. The 

 ductus choledochus and cystic duct are similarly constructed, only 

 their walls are thinner, and are distinctly sub-divided into a mucous 



