DEVELOPMENT OF THE ALIMENTARY TUBE AND APPENDED ORGANS. 347 



branches which circumvent them. Thus there is formed a network of trabec- 

 ulae of liver cells, called hepatic cylinders, the meshes of which are filled with blood 

 vessels. Therefore the liver is distinguished from other glands in general in 



Stomach 



Left hep. 

 duct 



[ Dors, pancreas 



'A Vent, pancreas 



Duodenum 



FIG. 312. From a reconstruction of the anlagen of the liver and pancreas and a part of the 

 stomach and duodenum of a human embryo of 4 weeks. Felix. 



that the hepatic cylinders, which are comparable with the smaller ducts and 

 terminal tubules of other glands, anastomose, and in that the blood vessels are 

 broken up by the growth of these cylinders. 



4 



FIG. 313. From a reconstruction of the anlagen of the liver and pancreas and the stomach 



of a human embryo of 8 mm. Hammar. 



D.P., Dorsal pancreas; Du., duodenum; D. V., ductus venosus; G.B., gall bladder; 

 R.I., right lobe of liver; ., stomach; V.P., ventral pancreas. 



This mode of development establishes what is known as a sinusoidal circulation, which 

 differs from the ordinary capillary circulation. The sinusoids are produced by the growth 

 of the trabeculse of the developing organ into large vessels and the breaking up of the latter 



