122 SPECIAL HISTOLOGY. 



or very sparingly; the ductus interlobulares, however, as they have 

 been termed, appear to be continuous with each other and thus 

 to invest the hepatic islets. From these ducts of ^ — ij/" 

 branches of T ^ — ■•£&" proceed, in no very great numbers, to the 

 hepatic islets and become continuous with the hepatic network 

 in the mode above described. Perhaps the very fine biliary 

 ducts, which I have, as stated above, observed microscopically, 

 with a diameter of 001'" and a cavity of 00033"', are identical 

 with a part, at all events, 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'", possess a thick fibrous membrane, composed of dense 

 connective tissue with many nuclei and elastic fibres, and a 

 cylinder epithelium O'Ol"' thick, which, in ducts under 0*04 — 

 0*05'", becomes gradually changed into a tesselated 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 mucous 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'" 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 foliaceous intestinal 

 villi and it is also provided with a cylinder epithelium, whose 

 cells are often, like the membranes of the gall-bladder, tho- 

 roughly 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 0016 — 0*024 /// , differ in no essential 

 respect from those of other racemose glands. In the ductus 

 hepaticus, choledochus, and in the lower portion of the cysticus, 

 the glands in the fibrous tunic and parts external to it, are 

 very numerous, \ — \'" in diameter, opening singly or many 

 together by foramina of 0*1 — 0*14'" visible to the naked eye, 

 which give the mucous membrane of those canals a reticulated 



