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HANDBOOK OF PHYSIOLOGY. 



be always bounded by hepatic cells on all sides, aiid are thus separated, 

 from the nearest blood-capillary by at least the breadth of one cell (Figs. 

 211 and 212). 



THE GALL-BLADDER. 



The Gall-bladder (G, B, Fig. 204) is a pyriform bag, attached to 

 the under surface of the liver, and supported also by the peritoneum, 

 which passes below it. The larger end or fundus, projects beyond the 

 front margin of the liver ; while the smaller end contracts into the 

 cystic duct. 



Structure. The walls of the gall-bladder are constructed of three 

 principal coats. (1) Externally (excepting that part which is in con- 

 tact with the liver), is the serous coat, which has the same structure as 



FIG. 211. 



FIG. 212. 



FIG. 211. Portion of a lobule of liver, a, bile capillaries between liver-cells, the network in 

 which is well seen ; 6, blood capillaries. X 350. (Klein and Noble Smith.) 



FIG. 212. Hepatic cells and bile capillaries, from the liver of a child three months old. Both 

 figures represent fragments of a section carried through the periphery of a lobule. The red cor- 



mds to an interlpbular 

 :ts, to which, at. 

 Hering.) 



the peritoneum with which it is continuous. Within this is (2) the 

 fibrous or areolar coat, constructed of tough fibrous and elastic tissue, with 

 which is mingled a considerable number of plain muscular fibres, both 

 longitudinal and circular. (3) Internally the gall-bladder is lined by 

 mucous membrane, and a layer of columnar epithelium. The surface 

 of the mucous membrane presents to the naked eye a minutely honey- 

 combed appearance from a number of tiny polygonal depressions with 

 intervening ridges, by which its surface is mapped out. In the cystic 

 duct the mucous membrane is raised up in the form of crescentic folds, 

 which together appear like a spiral valve, and which minister to the- 

 function of the gall-bladder in retaining the bile during the intervals, 

 of digestion. 



