382 
DR. LIONEL BEALE ON THE 
The cells of which these rows are composed, for the most part form single lines, 
although here and there, where the tubes are wider than usual, two cells may be 
seen lying transversely across the tube. In a specimen in which these radiating tubes 
had been injected, not only was the existence of a basement membrane proved, but 
one distinct from, and not adhering to the walls of the capillary vessels. Although 
the meshes of the capillary network are slightly elongated towards the centre of the 
lobule, such an arrangement could not produce the appearance observed. If the cells 
lay promiscuously in the meshes of the capillaries without being circumscribed by any 
basement membrane, the radiating lines would necessarily be connected transversely 
by very numerous cells. 
Some of these tubes from the human liver are represented in a drawing not 
published, which was copied from an injected specimen*. 
The contents of the cell-containing network are liable to considerable alterations 
in volume, a change which can be readily effected artificially. In the same specimen 
the diameter of the network varies to a limited extent, according to the size and 
number of the cells within the basement membrane. It is usually about jioowth of 
an inch in diameter in most mammalian animals, and is considerably wider than the 
narrowest part of the small ducts with which it is immediately continuous. 
The width of the spaces between the tubes of the network, or in other words, the 
diameter of the vessels, varies much in different parts of the lobule of the human 
liver, being much wider at the portal surface, where the small branches of the vein 
enter, than at a greater depth where capillaries are alone found. 
This point is shown in sections from different parts of the lobule of the liver of the 
foetus in Plate XV. fig. I7. 
In some situations, then, it is demonstrable that the basement membrane of the 
cell-containing network is distinct from the walls of the capillaries ; but in the greater 
part of the lobule, where the two membranes come into close contact, they are incor- 
porated, so that really the majority of the liver-cells are nearly surrounded with 
blood, from which they are only separated by one thin layer of delicate structureless 
membrane. 
In the foetus there is a distinct interval between the wall of the tube in which the 
secreting cells lie, and that of the capillary vessels ; so that when a good section is 
obtained, two distinct lines are seen between the liver-cells and the cavity of the 
cajnllaries. These two lines are separated by a transparent, apparently structureless 
substance, in which no trace of fibres can be detected, as represented in fig. 17. 
These circumstances impress me with the notion that the liver is originally com- 
posed of two distinct networks which intimately interdigitate with, or fit into, each 
other, — one containing the secreting cells, the other the blood. The walls of these 
* I have not been able to demonstrate the presence of csecal tubes connected with the branches of the net- 
work in the lobules of the liver, but from the arrangement of those of the “ vasa aberrantia,” presently to be 
described, and from other appearances which I have observed, I think it likely that such exist in small number. 
