538 SPECIAL HISTOLOGY. 



of those -which have been injected as the origins of the hypothetical 

 lobular biliary ducts. 



All the biliary ducts, down to those which have a diameter of 0*1 of 

 a line, possess a thick fibrous membrane, composed of dense connective 

 tissue with many nuclei and elastic fibres, and a cylinder epithelium 

 0-01 of a line thick, which, in ducts under 0-04-0-05 of a line, becomes 

 gradually changed into a tessellated epithelium. The ductus communis 

 choledochus and the cystic duct are similarly constituted, only their walls 

 are thinner, and they may be readily separated into a fibrous and a mu- 

 cous layer, the latter of which contains also a few muscular fibre-cells, 

 but on the whole so sparingly, that these ducts cannot be said to possess 

 any special muscular coat. 



The gall-bladder has, between its peritoneal covering and the abundant 

 subserous connective tissue, a delicate layer of muscles, whose fibre-cells, 

 0-03-0-04 of a line long, take more particularly a longitudinal and a 

 transverse direction and present only indistinct nuclei. The mucous 

 membrane is distinguished by many reticulated, more or less prominent 

 folds, which contain a capillary network, exactly like that of the folia- 

 ceous intestinal villi, and it is also provided with a cylinder epithelium, 

 whose cells are often, like the membranes of the gall-bladder, thoroughly 

 stained with bile ; their nuclei are not always distinct. 



The walls of the biliary ducts contain a multitude of small, racemose, 

 yellowish mucous glands, the glands of the biliary ducts, whose vesicles 

 of 0-016-0-024 of a line, differ in no essential respect from those of 

 other racemose glands. In the ductus hepaticus, choledochus, and in the 

 lower portion of the systicus, the glands in the fibrous tunic and parts 

 external to it, are very numerous, \-\ line in diameter, opening singly 

 or many together by foramina of 0-1-0-14 of a line, visible to the 

 naked eye, which give the mucous membrane of those canals a reticulated 

 appearance. At the commencement of the cystic duct the glands 

 are few, and in the gall-bladder itself, in which they are said to have 

 been met with, their occurrence is certainly not constant. On the other 

 Land, in the branches of the hepatic duct, down to Jd of aline in diame- 

 ter, such glands are again met with, many of them opening by a double 

 series of fine apertures which exist in these canals. 



i 



We may refer here to certain peculiar ramifications of the biliary 

 duct, vasa aberrantia (E. H. Weber). They exist : 1, in the lig amentum 

 triangulare sinistrum, as 6-10 and more canals, 0-006-0-0027 of a line 

 in diameter, consisting of a fibrous membrane and small cells. Ferrein 

 and Kiernan traced them as far as the diaphragm, though for the most 

 part they only extend to the middle of the ligament, or not so far, 

 branching out, forming networks, or anastomosing in loops. According 

 to Theile, tolerably large biliary ducts frequently proceed as far as the 



