ARRANGEMENT OF THE BILIARY DUCTS. 
387 
rantia,” originally described by Weber in the transverse fissure of the liver. They 
have been previously alluded to when the anastomoses of the ducts were described. 
Theile regarded these ducts, so well named by Weber, as irregular and branched 
mucous glands. Some observers, and lately Lereboullet, have altogether failed to 
discover these curious branches. The csecal appendages connected with these ducts 
are very numerous and of uniform size. Their coats are much thinner than those of 
the ordinary galUducts. They are lined with epithelium, principally of the sub- 
columnar form. 
These curious ducts are most numerous in the transverse fissure, but are also found 
in the upper part of the umbilical fissure. I have seen these ducts in all the large 
portal canals, and in those not more than a quarter of an inch in diameter, they are 
found occasionally. Many of the smaller ducts at their origin from a larger trunk 
in a portal canal have csecal appendages like a branch of the vasa aberrantia, and on 
the other hand straight branches may be traced from these aberrant ducts in some 
instances in the transverse fissure, to the hepatic tissue, Plate XIII. fig. 4 a. 
The vasa aberrantia are always closely surrounded by areolar tissue, in which 
lymphatics are very numerous, and adipose tissue not unfrequently abundant. 
The arrangement of the vessels is peculiar. The arteries and veins form a network, 
in the meshes of which the vasa aberrantia lie. Each small branch of the artery is 
accompanied by two branches of the vein, lying one on each side of it, which 
communicate by numerous transverse branches, some of which pass over the artery, 
and others under it. It is interesting to observe that this peculiar arrangement 
of the arteries and veins exists in the coats of the gall-bladder, in the transverse 
Jissure of the liver, and in the portal canals. It is only to be seen in good double 
injections ; but when the vessels are thoroughly injected with different colours, a most 
beautiful appearance is produced. The veins pour their blood into large branches of 
the portal vein. This peculiar arrangement of the veins doubtless has the effect of 
ensuring free circulation through them under different circumstances, and admits of 
their being compressed or stretched to a great degree without obstruction to the 
passage of blood through them. Some of these vessels are represented in Plate XIII. 
fig. 1 a. 
In the transverse fissure of the adult human liver the vasa aberrantia lie nearer to 
the trunk of the portal vein than to the hepatic tissue, and they can be removed 
without cutting into it. In the liver of the foetus, on the other hand, the quantity of 
areolar tissue is much less, and the vasa aberrantia lie so close to the hepatic tissue, 
that it is impossible to remove them without a thin layer of the latter, into which they 
enter at numerous points. In the foetus these ducts are less numerous than in the 
adult, and their course is less tortuous. They occur in small patches in which the 
branches are seen to be very numerous, and the anastomoses very frequent. The 
epithelium is more abundant, and the cells large and of a dark colour, and the 
injection does not run so readily as in the adult. 
