384 
DR. LIONEL BEALE ON THE 
for the most part, the cells form a single row within the basement membrane (human 
subject, pig, dog, cat, rabbit, horse, seal, Guinea-pig and others). In some situa- 
tions the tube contains two cells lying transversely across it, but this appearance is 
often produced by two tubes being placed in close juxtaposition. Sometimes, when 
the ducts have been injected, two ceils may be forced across the tube by the pressure 
of the injection, Plate XV. fig. 24. The cells do not completely fill the tubes, neither 
are they always placed quite close together, bat a certain quantity of granular matter 
is seen to intervene. The action of certain reagents in causing the fusion of the 
contents of the cells has been alluded to, but it is doubtful if these so-called cells in all 
instances have a distinct membranous wall. Injection runs sometimes on one side 
and sometimes upon the other side of the tube. Often it entirely surrounds the cells, 
and not unfrequentiy presses them to one side and separates them a little from each 
other, Plate XV. fig. 23. 
From these circumstances it would appear that the cells are not firmly adherent to 
the walls of the tube ; indeed many of them often appear to lie free vvithin its cavity, 
but exhibit a tendency to cohere to each other when set free. 
In the only embryos of mammalia which I have examined, there is often more than 
one row of cells within the tubes, frequently two or three (human subject, calf), Plate 
XV. fig. 17. The cells are smaller, but in many situations the diameter of the tubes 
is greater than in the adult. 
In birds, the tubes in some parts are wide enough to contain two or three iwvs of 
cells, but in others there is only room for one row (duck, linnet, turkey, starling, 
fowl). In the chick several rows of ceils lie within the tubes of the network, Plate 
XV. figs. 29 & 30. 
In those reptiles which 1 have examined, for the most part several cells are seen 
lying across the tube (frog, adder, field-snake, newt). 
In fishes also the tubes are wide and contain several in the transverse direction 
(flounder, frog-fish, sturgeon, herring, cod), Plate XV. figs. 36 & 3/. 
It may be remarked generally that the cell-containing network is widest among 
fishes, and most narrow in mammalia. The similarity of the arrangement of the cells 
in the tubular network in the embryos of the higher animals with that existing in the 
adult, as well as in the embryonic condition of the lower, is a point of interest, of 
which there are many analogous examples in the case of other organs. 
The changes in volume which the hepatic cells so readily undergo, renders it very 
difficult to ascertain their dimensions with accuracy. 
OF THE DUCTS OF THE LIVER. 
The duct, like the artery, lies close to the portal vein in the portal canals, and 
usually on the same side. In the large portal canals the external coats of the duct 
and artery are incorporated with that of the vein, a point well seen in the horse when 
the duct is very large. The position of the vessels remains nearly the same in the 
