DEVELOPMENT OF THE ALIMENTARY TUBE AND APPENDED ORGANS. 351 



(or two) ventral. The dorsal anlage appears first as a ridge-like evagination 

 from the dorsal wall of the gut, slightly cranial to the level of the liver (Figs. 311 

 and 312). It appears about the same time as the liver or a little later. The 

 mass of cells grows into the dorsal mesentery and becomes constricted from 

 the parent epithelium except for a thin neck which becomes the duct of 

 Santorini (Fig. 316). A little later two other diverticula appear, one from each 

 side of the common bile duct. It is uncertain whether only one or both of these 



Stomach 



Liver 



Cystic duct 



Dorsal pancreas - 



Gall bladder 



Ductus choledochus 

 Ventral pancreas 



Ductus choledochus 



Liver 



Dorsal pancreas 



Acces. pancr. duct 

 (Santorini) 



Duodenum 



Cystic duct 



Gall bladder 



Ventral pancreas with 

 pancr. duct (Wirsung) 

 FIG. 317. 



FIGS. 316 and 317. From models of the developing liver and pancreas of rabbit embryos of 

 8 mm. and 10 mm , respectively-. Both seen from the right side. Hammar, Bonnet. 



take part in the formation of the pancreas, but it seems most probable that the 

 left one disappears entirely. The right diverticulum continues to develop and 

 becomes constricted from the parent epithelium, leaving only a thin neck which 

 becomes the duct of Wirsung. 



The smaller ventral pancreas grows to the right and then dorsally in the 

 mesentery (Fig. 318), passing over the right surface of the portal vein, until it 

 meets and fuses with the proximal part of the larger dorsal pancreas. The 

 fusion takes place in the sixth week, and the two anlagen then form a single 



