CHAP.,XXXIII.] PASSAGE OF BILE INTO DUCTS. 479 



liver. The cells have been nearly destroyed by the action of 

 reagents in preparing the specimen. 



The epithelial cells which line these vig.w\ 



minute ducts approach to the tesselated 

 variety. They are, for the most part, round 

 or oval granular cells, some of them about 

 the yoVo^h of an inch in diameter, 

 while others are less. They present very 

 similar characters in the different ani- 

 mals which we have examined, and the 

 same general arrangement of the minute 

 ducts has been shown to occur in birds, 



,'i -in-t ',1 , Narrowest portions of the duct, 



reptiles, and fishes, with certain umrn- lined by ductai epithelium, showing 



. , -,. . ' their connection with the cell-con - 



portant mOOinCatlOnS. taining network. Close to the narrow 



mu in *.i/i T p ji i i L. ducts, a venous capillary and a small 



1 he Epithelium of the duCtS does not branch of the artery are represented 



-i j ,. . , .-, ,. in section. The liver cells have been 



paSS by gradations into the Secreting epi- destroyed by the mode of prepara- 



j.11' -i , . , , tion. From an uninjected specimen 



tnellUm, but terminates at the point O f the human liver, magnified 215 



where the latter commences. The nar- diame ers ' aft 

 rowing of the excretory portion of the tube is met with in many 

 other glands, but in none is there a more striking contrast between 

 the excretory and secreting portions of the gland, or between the 

 epithelium lining the ducts and that by which the secretion is 

 formed, than in the liver. 



Of the Passage of the Bile into the Ducts. If the view of the 

 anatomy of the liver which we have described be correct, the 

 secreting cells at the surface of the lobule are those which take the 

 most active part in the secretion. These are the cells which the 

 portal blood first reaches ; and it is in this situation that the cells 

 first show an increased quantity of oil globules within them in 

 cases of fatty degeneration. The bile is not formed in the central 

 part of the lobule and transmitted from cell to cell, as has been 

 described by some authorities, but the bile formed by each indi- 

 vidual cell escapes through the interstices between the cells until it 

 reaches the duct. If it be urged as an objection to this view, that 

 no visible interstices exist between the cells, it may be answered, 

 that injection can be made to flow by these channels in a direction 

 the reverse of that which the bile naturally takes, and, therefore, 

 under the greatest disadvantage. There can then be no obstacle to 

 the passage of the bile towards the ducts : moreover, the great 

 changes in bulk which we know the liver cells so readily undergo, 

 will readily account for the close contact in which they are often 

 observed to lie. 



