ARRANGEMENT OF THE BILIARY DUCTS. 
383 
two sets of tubes gradually become incorporated, except in those situations where 
the capillary network is less dense, or where the meshes of the cell-containing net- 
work are more widely separated from each other; in which cases a distinct limitary 
membrane to the tubes containing the liver-cells can be demonstrated even in the 
adult. The cell-containing network and the vascular network can be alternately 
distended. The membrane is very permeable to water in both directions, as 1 have 
proved by first forcing fluid from the vessels into the duct, and afterwards in the 
opposite direction. Subsequent injection proved that no rupture had taken place. 
The greatest force which can be applied will not cause the bile to pass through 
this delicate membrane into the capillary vessels. It is permeable to bile only in 
one direction. 
Of the contents of the Tubular Network of Basement Membrane, and of the Arrange- 
ment of the Liver-cells within it. 
Within the tubular network lie the hepatic cells, with a certain quantity of granular 
matter and cell debris, and in some instances, free granules of yellow colouring 
matter and free oil-globules. The liver-cells have been described by many writers. 
They are not arranged in any definite or regular manner within the tubes of base- 
ment membrane. Their form appears to be determined to a great extent by mutual 
adaptation and pressure. In adult animals they usually contain one nucleus, and 
within this is a bright point (nucleolus) and faint granules ; rarely cells containing 
two nuclei are found. In the embryo, however, the cells contain two nuclei very 
commonly, and often cells are met with which contain several (from two to six). 
Besides the nucleus, the liver-cell contains, as is well known, coloured granules and 
oil-globules, apparently suspended in a viscid albuminous material. The coloured 
granules are not constantly present. Often they are numerous in cells near the 
centre of the lobule, and entirely absent in those near the margin, while the reverse is 
usually the case with reference to the oil-globules. On some occasions, ceils which 
contained no coloured granules when first examined, were found to contain several 
after having been allowed to soak for some time in dilute acetic acid. The granules 
of colouring matter are, however, not unfrequently present in the cells near the centre 
of the lobule, as well as in those containing much oil at the circumference. In some 
instances I have observed that the cells near the centre of the lobule were smaller and 
were surrounded with a greater quantity of granular matter than those nearer the 
margin. 
Many observers have endeavoured to show that the cells of the liver are arranged 
in a definite manner. Professor Lereboullet, one of the latest writers on this point 
(1853), describes the cells as arranged in double rows, between which injection can 
be forced so as to separate them, and he gives two diagrams to illustrate his views on 
this point. I have never seen anything like this arrangement, and, as I have before 
remarked, injection passes very readily at the outer part of the tubes. In mammalia, 
3 E 2 
