ARRANGKAIENT OF THE BILIARY DUCTS. 
395 
7 . The walls of the smallest ducts are composed of basement membrane only. 
The thick complex coat of the larger ducts contains within it small cavities (the so- 
called glands of the ducts), by which the bile in these thick-walled tubes would be 
brought into close proximity with the arteries, veins and lymphatics, which are very 
abundant wherever the ducts ramify. 
8. The office of the vasa aberrantia, which are so numerous in the transverse fissure 
of the human liver and in the larger portal canals, appears to be similar to tliat of 
the cavities in the walls of the ducts. It is worthy of remark, that the network of 
vessels ramifying so abundantly in the coats of the gall-bladder, in the transverse 
fissure, and in the large portal canals, is arranged in a similar manner, each branch 
of artery being accompanied by two branches of the vein. 
9. The liver is therefore a true gland, consisting of a formative portion and a 
system of excretory ducts directly continuous with it. The secreting cells lie within a 
delicate tubular network of basement membrane, through the thin wall of which they 
draw from the blood the materials of their secretion. 
Explanation of the Plates. 
The dotted shading in the Plates corresponds to the Prussian blue injection represented in the drawing. 
By tracing this shading, the extent to which the injection had penetrated in the preparation is shown. 
To ascertain the diameter of any object represented, it is only necessary to compare it with one of the scales 
at the foot of the Plates, the divisions of which are magnified in the same degree as the drawing. 
PLATE XIII. 
Fig. 1. Vasa aberrantia, from the transverse fissure of the human liver, injected with 
Prussian blue. a. Branches of portal vein injected with white lead. h. 
Branches of hepatic artery injected with vermilion, c. Branches of duct 
or vasa aberrantia, in some places only partially injected. 
Figs. 2 & 3. Ducts with vasa aberrantia, from the transverse fissure of the human 
liver, injected with Prussian blue. 
Fig. 4. Dilated portion of duct from the transverse fissure of the human liver, giving 
off long straight branches to secreting structure. 
Fig. 5. Vasa aberrantia and parietal appendages of ducts from the transverse fissure. 
This drawing represents the portion of fig. 3 marked a, magnified 8 
diameters. 
Fig. 6. Interlobular duct with lateral appendages and one or two irregular branched 
ducts or vasa aberrantia. The greater number of the lateral channels are 
seen not to project beyond the outer surface of the fibrous coat of the 
duct, a. 
