THE LIVER. 133 



consists at first of round cells, probably in many layers, by the 

 multiplication of its cells, and extend into the outer lamina, 

 branching out and anastomosing, whilst, at the same time, the 

 cells of the outer lamina included in the meshes of this net- 

 work, multiply and become successively changed into vessels, 

 nerves, connective tissue, &c. The difficulty is to say how 

 this peculiar, reticulated parenchyma of cells and rudimentary 

 vessels becomes ultimately arranged as we know it to be. In 

 the first place, as regards the hepatic- cell-network and the islets 

 or lobules of the complete liver. They evidently proceed from 

 the further growth of the original hepatic-cell-network, to which 

 by a continual new development of cells, fresh processes are 

 added, which unite into new networks, so that the hepatic- 

 cell-network of the adult liver is the direct progeny of the 

 original reticulation. More detailed information concerning 

 the separate steps of the formation of the hepatic-cell-network, 

 is at present wanting ; yet from what is known it would appear to 

 take place in somewhat different modes. Sometimes, in the 

 subsequent stages, free cylindrical processes of the hepatic- 

 cell-network do not exist to any extent, but it would appear 

 to increase by the continual addition of new meshes at its 

 edges, perhaps also by the constant elongation of the existing 

 columns of hepatic cells and the development of fresh anasto- 

 moses between them : this is, if I have observed rightly, the 

 case in man, where even in the seventh week I did not succeed 

 in clearly distinguishing free hepatic columns. At other times, 

 free terminations of the hepatic columns are apparently 

 developed for a considerable period, perhaps until the whole 

 organ has nearly arrived at perfection, their formation appear- 

 ing to precede by some time that of new anastomoses, as is the 

 case in the Chick and other Birds, and according to J. Miiller, 

 in a few Mammals ; in the latter of which, according to Muller's 

 figures; the hepatic columns are grouped in lobes. These free, 

 superficial hepatic columns may perhaps throw some light upon 

 the meaning of Weber's and Krause's statements respecting the 

 biliary ducts with coecal ends upon the surface of the liver. 

 With regard to the biliary ducts, they are assuredly nothing 

 but secondary excavations of a part of the primarily solid 

 hepatic columns and of the larger'internal tracts, which border 

 upon the original epithelial diverticulum and which all consist 



