CHAP, iv.] METABOLIC PROCESSES OF THE BODY. 711 



marginal cells as of all the other cells of the lobule run bile- 

 capillaries, and these are continuous on the one side with the lumen 

 of the ductule, and on the other hand with the network of the bile- 

 capillaries traversing the lobule. In the ductule itself the lumen 

 is single, cylindrical, and of some size, it suddenly divides into 

 much smaller passages, and the cells lining these smaller branching 

 passages are no longer simply epithelium cells lining a duct, but 

 complex hepatic cells. 



It would appear then that after all the hepatic cells are really 

 cells lining the terminal secreting portions of the duct, lining we 

 might almost say the alveoli, but owing on the one hand to the 

 distribution of blood vessels, so different from that which obtains 

 in the alveoli of other glands, and on the other hand to modifica- 

 tions of the hepatic cells, due to their being engaged in other 

 functions than that of secreting bile, the relations of the cells to 

 the lumina of the alveoli is peculiar. 



451. In the lower animals the structure of the liver is 

 simpler, and a brief description of the frog's liver may perhaps 

 assist towards the comprehension of the nature of the mammalian 

 liver. The liver of the frog as seen in a section appears to be 



FIG. 91. SECTION OF LIVEB OF FROG. (Langley.) 



The Figure shews the tubular structure of the liver. At (a) a tubule is seen in 

 transverse, at (b) in longitudinal section. I, lumen of tubule. 



The liver was that of a winter frog, and the cells shew an inner zone of proteid 

 granules ; the outer zone was chiefly occupied by glycogen. 



