THE LIVER. 



681 



already claimed that the liver of man can be classified among 

 the tubular glands (Biesiadecki). In human embryos these rela- 

 tions are still more marked, and for this reason Toldt and 

 Zuckerkandl have maintained that the structure of the liver of 

 human embryos is tubular, each bile-capillary being surrounded 

 by from three to five liver epithelia; the transformation into 

 liver- structure proper begins, according to these authors, after 

 birth. But, in fact, there is no difference between the liver of 

 an embryo, that of a child six years old (see Fig. 277), and that 

 of adults, with the exception that the 

 individual epithelia appear larger with 

 the advancing development of the 

 liver. (See Fig. 301,) 



In places where interstitial con- 

 nective tissue is most abundant, the 

 bile-capillaries, upon approaching the 

 periphery of a lobule, produce a sys- 

 tem of canals lying between the outer- 

 most epithelia and the connective 

 tissue, and inosculating with the Ule- 

 ducts. These at first are only slightly 

 larger than the bile-capillaries, and 

 by their union at right angles produce 

 larger tubules, which invariably run 

 in the interstitial connective tissue 

 only. The epithelial lining, at first 

 composed of flat and small bodies, 

 gradually becomes more distinct, as- 

 suming the characters of cuboidal 

 epithelia, while in the largest ducts the 



epithelia are distinctly columnar. Toward the central caliber 

 the cement-substance produces a distinct investing layer, which 

 in the larger ducts is studded with short rods (Virchow), similar to 

 those of the columnar epithelia of the intestines. In the smaller 

 ducts the connective tissue is not differentiated into a separate 

 investing layer, while the larger ducts have such a layer, pro- 

 vided with elastic fibrillae and a reticulum of capillary blood- 

 vessels ; smooth muscle-fibers are also met with in the wall of 

 the larger bile-ducts. (See Fig. 302.) 



E. H. Weber has described as vasa dberrantia bile-ducts which 

 occur, sometimes in large numbers, in membranaceous forma- 

 tions on the outside of the liver-tissue, where, evidently, in the 



FIG. 301. LIVER OF A 

 HUMAN FCETUS OF FIVE 

 MONTHS. 



E, epithelia, arranged around a 

 central bile-capillary ; C, capillary 

 blood-vessels, containing a few 

 blood-corpuscles, their endothelial 

 wall detached from the surface of 

 the liver epithelia. Magnified 500 

 diameters. 



