SECT. 163.] DEVELOPMENT OF THE LIVER. 



and fibres of Remah, they always contain some thick 

 They may be traced: 1. on the gall-bladder and the large\ 

 ducts; 2. in the capsule of Glisson, as far as the interlob 

 arteries, where the finest branches, of o - oo8'" to O'oiz"' in cu 

 meter, possess only nucleated fibres; 3. to the hepatic veins; lastly, 

 4. into the coats of the liver. 



In the transverse fissure of the human liver, in the large portal canals, and 

 in the gall-bladder of the human subject, a very peculiar ai'rangement of the 

 \ . ssels occurs. Both arteries and veins form a network, and each branch of 

 the artery is accompanied with two branches of the vein, one on either side 

 of it (E. II. Weber, L.Beale). 



§ 163. The development of the liver may, according to the most 

 recent observations of Bisclioff and Remah, be best understood in 

 the following manner : — The primitive rudiment of the liver, 

 appearing, as is well known, very early (in the chick, at the fifty- 

 fifth and fifty-eighth hour; in mammalia, after the Wolffian 

 bodies and the allantois), consists of two collections of cells, an 

 outer, which has arisen from the fibrous coat of the intestine, and an 

 inner epithelial, which forms at first a simple, and then a bifurcated 

 tube. From the epithelial layer, which, like the intestine, at first 

 consists of round cells, perhaps in several strata, there are formed, 

 by the multiplication of cells, solid outgrowths into the outer 

 layer, the hepatic cylinders of Remah, which, in their further 

 growth, ramify and anastomose; whilst, at the same time, the cells 

 of the outer layer, enclosed in the meshes of this network, likewise 

 multiply, and become successively converted into vessels, nerves, 

 connective tissue, etc. It is difficult, however, to say in what 

 manner, out of this peculiar reticulated parenchyma of cells and 

 vascular rudiments, the subsequent conditions are evolved. The 

 hepatic cell-networks and lobules of the fully developed liver are 

 obviously produced by the further growth of the primitive hepatic 

 cylinders, which, by the continued multiplication of cells, succes- 

 sively put forth new processes, and join again and again in a 

 reticulate manner; so that the hepatic cell-network of the fully 

 developed liver appears thus to be lineally derived from the pri- 

 mitive network. AVith respect to the bile-ducts, they certainly 

 originate as secondary excavations of a part of the originally solid 

 hepatic cylinders and of the larger inner cords, bordering upon 

 the primitive protrusion of the epithelium (all of which consist 

 of several rows of cells), which excavation advances from the 

 common bile-duct to the branches. In this way of viewing the 



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