THE BILIARY PASSAGES. 



181 



capillaries normally exist within the substance of the cells, thus forming 

 inimcellular secretion-canaliculi. The latter are sometimes pictured as 

 ending in minute dilatations, the secretion-vacuoles. It is highly probable that 

 such appearances, while not artefacts, at least depend upon particular condi- 

 tions of secretory activity and are, therefore, not constant details of the 

 hepatic cells. 



The intralobular connective tissue is very meagre in amount and 

 consists of delicate prolongations of the interlobular fibrous tissue along the 

 blood-capillaries. The tissue occurs only between the blood-channels and 

 the cells and never between the latter. Although present in some quantity 

 immediately around the central vein, in other parts of the lobule it is repre- 

 sented by lattice-works of fibres which surround the capillaries. The fibres 

 are not elastic in nature, but correspond most closely to modified white fibres, 



Portal vein 



' '' ' -*-*""." '' V". \ ,- 



Bile-duct 

 Hepatic artery 



Interlobular connectiv* 

 tissue 



Hepatic cells 

 FIG. 226. Section of liver, showing interlobular tissue and vessels. X 160. 



the entire intralobular connective tissue belonging to the variety known as 

 reticular. The small spindle or stellate elements seen in gold preparations, 

 known as the cells of Kupffer, have been shown to belong to the capillary wall 

 (perhaps distorted endothelial cells) and not to the peri vascular fibrous tissue. 



The Biliary Passages. The interlobular bile-ducts, which re- 

 ceive the canals that pierce the periphery of the lobule as outlets of the 

 intralobular network, accompany the branches of the portal vein and of the 

 hepatic artery within the connective tissue between the lobules. The ducts, 

 from 30-50 /j. in diameter, form a network over the exterior of the lobule 

 and possess walls consisting of a delicate fibro-elastic coat, in the smallest 

 tubes little more than a basement membrane, lined with low columnar epi- 

 thelium continuous with the cuboidal cells clothing the emergent canals. 

 The perilobular ducts are tributaries of larger bile-vessels, which increase in 

 diameter as they pass towards the transverse fissure. 



The large ducts join into two main lobar trunks, by whose union, within 

 or just beyond the transverse fissure, the hepatic duct is formed, a tube 

 from 4-6 mm. in diameter and about 2.5 cm. long. Its walls include a dense 

 fibro-elastic tunica propria, covered with a single layer of columnar epithelium 



