THE LIVER 



177 



versum, and later when the septum becomes a part of the diaphragm the 

 liver remains attached to it. 



In embryos 4 to 5 mm. long, solid cords of cells proliferate from the 

 ventral and cranial portion of the hepatic diverticulum (Fig. 86). These 

 cords anastomose and form a crescentic mass with wings extending dorsal 

 and lateral to the gut (Fig. 177). This mass, a network of solid trabeculae, 

 is the glandular portion of the liver. The primitive, hollow diverticulum 

 later differentiates into the gall bladder and the large biliary ducts. 



Referring to Fig. 88, it will be seen that the liver anlage lies between 

 the vitelline veins and is in close proximity to them laterally. The veins 

 send anastomosing branches into the ventral mesentery. The trabeculae 

 of the expanding liver grow between and about these venous plexuses, and 



FIG. 184. 



-The trabeculae and sinusoids of the liver in section (after Minot). X 300. Tr. 

 Trabeculas of liver cells; Si., sinusoids. 



the plexuses in turn make their way between and around the liver cords 

 (Fig. 183). The vitelline veins on their way to the heart are thus sur- 

 rounded by the liver and largely subdivided into a network of vessels 

 termed sinusoids. The endothelium of the sinusoids is closely applied 

 to the cords of liver cells, which, in the early stages, contain no bile 

 capillaries (Fig. 184). The transformation of the vitelline veins into the 

 portal vein and the relations of the umbilical veins to the liver will be 

 treated in Chapter IX. 



The glandular portion of the liver grows rapidly, and, in embryos of 7 

 to 8 mm., is connected with the primitive hepatic diverticulum by a single 

 cord of cells only, the hepatic duct (Fig. 185 A). That portion of the 

 hepatic diverticulum distal to the hepatic duct is now differentiated into 

 the terminal, solid gall bladder and its cystic duct. Its proximal portion 

 forms the ductus choledochus. In embryos of 10 mm. (Fig. 185 B], the 



