ARRANGEMENT OF THE BILIARY DUCTS. 
389 
Of the finest branches of the Ducts, and of their connexion with the cell containing 
Network. 
Mammalia. — In well-injected preparations the smallest branches of the duct can be 
readily traced up to the secreting ceils, Plate XIV. fig. 10. The walls of these ducts 
are composed of basement membrane only, lined with delicate epithelium. In the 
human liver, and in that of most mammalia, except the pig, a few of the finest 
branches of the duct can be followed for some distance beneath the surface of the 
lobule, and are seen apparently lying amongst the secreting cells. 
In many animals, particularly in the rabbit, and to a much more limited extent in 
the dog and in the human subject, these smallest branches of the duct are connected 
together so as to form a network of ducts, distinguished by their diameter being 
much less than that of the netvvork in which the liver-cells lie, and by the character 
of their epithelium. These branches appear to lie in the most superficial part of the 
cell containing network, without being connected with the cells which surround them; 
but they join, or are continuous with, a portion of the cell-containing network at a 
deeper part of the lobule. The most superficial portion of the cell-containing net- 
work is connected with small ducts which do not penetrate amongst its meshes. 
This arrangement is shown in a very simple form in Plate XIV. fig. 16, which repre- 
sents a section from a seal’s liver, in which the ducts and cell-containing network 
were both well injected with transparent blue injection : at c, some of the superficial 
branches of the duct, and at d, branches which penetrate beneath the surface of the 
lobule, are represented. Some of these branches, which appear to lie amongst the 
secreting cells at the peripheral part of the lobule, have been figured by Gerlach, 
and are, as he justly observes, much narrower than the cells amongst which they lie. 
He makes them terminate by open mouths, into which the bile is poured from the 
cells. The narrowness of these tubes has been advanced as an argument against the 
possibility of the cells lying within tubes, but from the description just given it will 
be seen that this objection does not apply. 
In the pig, numerous fine branches of the duct are, as it were, applied to the sur- 
face of the capsule of the lobule (Plate XIII. fig. 9), which is perforated at frequent in- 
tervals by many very narrow short branches, which are immediately connected with 
a network which partly lies amongst the fibres of the capsule. This network may be 
looked upon as the most superficial portion of the cell-containing network, and the 
narrow tubes of which it is composed are found to contain oil-globules, granular 
matter, and a few very minute cells, Plate XV. fig. 25. When the liver is very fatty, 
however, this most superficial portion contains numerous secreting cells filled with 
oil-globules, Plate XV. fig. 28. I have not been able to trace any ducts passing 
amongst the meshes of the most superficial part of the cell-containing network, as I 
have described in animals in which the distinct lobules do not exist. In the last 
figure, the very narrow ductal portion of the tube is seen to dilate considerably at the 
MDCCCLVI. 3 F 
