SECRETION. 



451 



tion of the bile-ducts in the left lateral liga- 

 ment, which he considers as in itself a rudi- 

 mental liver, exhibiting the structure of the 

 entire organ in its most simple form. By Mr. 

 Bowman it was supposed, that the limitary 

 membrane forming the wall of the minute 

 biliary ducts is not continued into the sub- 

 stance of the lobule, but that the epithelial 

 lining of the ducts is continuous with the mass 

 of hepatic cells which forms its parenchyma. 

 There is an a priori improbability in such an 

 idea, which would leave the glandular cells in 

 immediate 'contact with the surface of the 

 blood-vessels ; an arrangement which does 

 not exist in any other gland. We have been 

 accustomed, therefore, to accord with the 

 opinion of Dr. Thomas Williams*, that the 

 limitary membrane of the bile-ducts is pro- 

 bably expanded over the whole of the paren- 

 chymatous portion of each lobule, moulding 

 itself upon, and identifying itself with, the 

 capsule or sheath of the vessels, and thus 

 forming a sort of irregularly reticulated cavity, 

 which may be described as the whole space 

 occupied by the lobule, minus the series of 

 passages containing the capillary plexus. The 

 manner in which the lining membrane of the 

 uterine sinuses with the cellular decidua are 

 prolonged into the placenta, and reflected 

 over the capillary tufts of the foetal vessels, so 

 as to divide the whole cavity of the placenta 

 into a series of irregularly shaped chambers, 

 freely communicating with each other, into 

 which the maternal blood is conveyed, will 

 convey an idea of this method of viewing the 

 disposition of parts in the liver ; the uterine 

 sinuses representingthebile-ducts ; thecellated 

 cavities of the placenta, corresponding with 

 the spaces occupied by the cells of the hepatic 

 parenchyma ; and the foetal vessels occupying 



Fig. 317. 



the place of the capillary plexus from whicli 

 the secretion is formed. 



The observations recently published by Dr. 

 Leidy harmonise precisely with the view pro- 

 mulgated by Mr. Kiernan, and seem to confirm 

 the idea that here, as elsewhere, the hepatic 

 cells are enclosed in a limitary membrane. 

 " The lobules are composed of an intertexture 

 of biliary tubes (.fig. 317.) ; and in the inter- 

 spaces of the network the blood-vessels ramify 

 and form among themselves an intricate 

 anastomosis, the whole being intimately con- 

 nected together by a combination of the white 

 fibrous and the yellow elastic tissue. In 



Biliary plexus in human Liver. 



Transverse section of a lobule of the human liver' 

 highly magnified, showing the reticulate struc- 

 ture of the biliary tubes. In the centre of the 

 figure is seen the hepatic vein cut across, and 

 several small branches terminating in it. At the 

 periphery are seen branches of the hepatic artery, 

 vena ports, and hepatic duct. (.After * 



Biliary plexus in human Liver. 



A small portion of the same section more highly 

 magnified. The secreting cells are seen within 

 the tubes ; and in the interspaces of the latter, the 

 fibrous tissue is represented. (After Leidy.} 



structure, the biliary tubes (Jigs. 318,319.) cor- 

 respond with those of Invertebrata, consisting 



Fig. 319. 



* Op. cit. p. 330. 



Biliary tulmlus of human Liver. 



Portion of a biliary tube from a fresh human liver, 

 very highly magnified. The secreting cells are 

 seen to be polygonal from mutual pressure. 

 (After Leidy. ) 



of cylinders of basement membrane, containing 

 numerous secreting cells, and the only differ- 

 ence exists in the arrangement, the free 

 tubes of the lower animals becoming anasto- 

 mosed on forming an intertexture in the Ver- 

 tebrata. The tubuli vary in size in an un- 

 important degree in different animals, and also 

 in the same animal, being generally from two 



G G 2 



