320 



THE DEVELOPMENT OF THE CHICK 



substance of the liver is derived. A third diverticulum is dis- 

 tinguished by Brouha as the right posterior diverticulum; this is 

 an early outgrowth of the posterior diverticulum. Hepatic cylin- 

 ders arise from both primary diverticula at an early stage, and 

 these, branching and anastomosing, soon form a basket-work of 

 liver tissue around the intermediate portion of the meatus venosus. 

 The anterior diverticulum alone extends forward to the anterior 



ff/z. - 



D.ch. 



FIG. 187. Reconstruction of gizzard, duodenum, 

 and hepato-pancreatic ducts of a chick embryo 

 of 124 hours. (After Brouha.) 



D. ch., Ductus choledochus. D. cy., Ductus cys- 

 ticus. D. h. cy., Ductus hepato-cysticus. D. h. d., 

 Dorsal or hepato-enteric duct. Du., Duodenum. 

 G. bl., Gall bladder. Giz., Gizzard. Pa. d., Dor- 

 sal pancreas. Pa. v. d., Right ventral pancreas. 

 Pa. v. s., Left ventral pancreas. 



end of the meatus, and it even encroaches on the sinus venosus, as 

 we have already seen; in the posterior part of the meatus venosus, 

 on the other hand, the liver tissue is derived entirely from the 

 posterior diverticulum. The mesenchyme in the interstices of 

 the hepatic framework is replaced almost immediately by blood- 



