SOR RA aera of the Human Liver. 81 
largest of these pouches are subdivided into smaller compartments 
by secondary folds of the membrane in their interior ; and it is into 
these subdivisions that the ducts of the hepatic glands empty. 
Judging from the position of the crescent-formed, almost valve-like 
margin of the pouches, it seems that their office is: to arrest the 
bile—coming from the interior of the organ—until it has been 
mixed with the secretion of the hepatic glands. In the larger ducts 
these pouches are numerous and irregularly distributed over the 
whole mucous membrane; but when the ducts have decreased in 
diameter to some extent, the pouches become arranged in two rows. 
The epithelium, by which the larger ducts are lined, is columnar 
and zo of an inch thick; its component cells can easily be ob- 
served in their different stages of development; their colour is 
greenish yellow, similar to that of the hepatic cells. Many of the 
fully-developed cells of epithelium of the larger ducts have the pecu- 
liarity of possessing filamentous appendages of extraordinary length. 
The development of these cells seems, at first, chiefly to take 
place in two opposite directions by filamentous processes, the result 
of which is a bi-polar cell. The longer process of this cell, which 
points towards the surface of the epithelium—after having grown 
to its full length, expands laterally, when the cell has become mature. 
I have seen a number of fully-grown cells provided with those fila- 
mentous appendages above mentioned, whose total length exceeded 
considerably the whole thickness of the epithelium. In these cases, 
the appendage must have rested horizontally upon the basement 
membrane. ‘The fully-developed cells, without filamentous append- 
ages, are goo Of an inch long, and yosoo of an inch wide. When 
the diameters of the ducts decrease to +45 of an inch, or smaller, the 
epithelium gradually commences to change from the columnar to 
the scaly form; and with the further decrease of the former, the 
flattened epithelial cells also decrease in diameter, until in the finer 
ones the epithelium consists only of nuclei, closely set together. 
Its last trace is only a granular layer, lining the short branches of 
the lobular ducts through which the transition into the network of 
“ bihary tubules” takes place. The outlines of the epithelial cells 
and nuclei of the smaller hepatic ducts are dark and well defined, 
which forms a characteristic by which the latter may easily be dis- 
tinguished from the blood-vessels. 
The fibrous layer of the mucous membrane of the larger hepatic 
ducts lodges a network of capillaries with very small meshes, derived 
from the anastomoses of small blood-vessels in the middle coat. 
Origin of the Lymphatics.—The finest branches of the lymphatie 
vessels in the human liver arise, like those of the hepatic duct, from 
the network of biliary tubules (Figs. 2, 5); they then join each 
other to form a plexus of larger vessels which have already been 
described. In the capsule of the portal vessels, small branches 
