THE LIVER 



185 



ductus choledochus. In embryos of 10 mm. (Fig. 178 B) the gall-bladder and 

 ducts have become longer and more slender. The hepatic duct receives a right 

 and left branch from the corresponding lobes of the liver. The gall-bladder is 

 without a lumen up to the 15 mm. stage. Later its cavity appears surrounded 

 by a wall of high columnar epithelium. 



The glandular portion of the liver develops fast and is largest relatively at 

 31 mm. (Jackson, Anat. Record, vol. 3, pp. 361-396, 1909). The liver tissue 

 degenerates, especially in the peripheral portion of the left lobe. In embryos of 

 two months the liver weighs 2 gm.; at birth 75 gm. ; in the adult 1500 gm. 



During the development of the liver the endothelial cells of the sinusoids become stellate 

 in outline, and thus form an incomplete layer. From the second month of fetal life to some 



Stomach 

 Hepatic duct 



Gall bladdi 



Cystic duct 

 Ductus choledoch 



Ventral pancreas 



Qorsal 

 pancreas 



ball bladder 



Cystic duct' 



rlepaiic ducr 



ctus choledochus 

 tral pancreas 



Duodenum 



Duct of dorsal 



pancreas 



Head of dorsal 



pancreas 



Duodenum 



Tail of dorsal 

 pancreas 



Fig. 178. — Reconstructions showing the development of the hepatic diverticulum and pancreatic 

 anlages. A, 7.5 mm. embryo, X 36 (after Thyng); B, 10 mm. embryo, X 33 (specimen loaned by Dr. 

 H. C. Tracy). 



time after birth, blood-cells are actively developed between the hepatic cells and the endothelium 

 of the sinusoids. The hepatic trabecular are mostly solid in 10 mm. embryos. At 22 

 mm. hollow periportal ducts develop, spreading inward from the hepatic duct along the 

 larger branches of the portal vein. These ducts form a plexus, as has been proved by injections. 

 Lumina bounded by five or six cells may be observed in some of the liver trabeculae of 10 mm. 

 embryos (Lewis). In 44 mrr. embryos, bile capillaries with cuticular borders are present, 

 most numerous near the periportal ducts with which some of them connect. At birth, or 

 shortly after, the number of liver cells surrounding a bile capillary is reduced to two, three or 

 four. 



The lobules, or vascular units of the liver, are formed, according to Mall, by the peculiar 

 and regular manner in which the veins of the liver branch. The primary branches of the portal 

 vein extend along the periphery of each primitive lobule, parallel to similar branches of the 

 hepatic veins which drain the blood from the center of each lobule (Fig. 179). As development 

 proceeds, each primary branch becomes a stem, giving off on either side secondary branches 



