ALIMENTARY TRACT AND ITS APPENDAGES 321 
vessels that empty into the meatus, and thus appear as branches 
of the latter. 
The gall-bladder is a very early formation, arising from the 
hindermost portion of the posterior hepatic diverticulum, as a 
distinct bud about the stage of 68 hours (Fig. 103), and forming 
a pyriform appendage at 84 hours. It may reasonably be re- 
garded as derived from the most posterior portion of the prim- 
itive hepatic gutter, an interpretation that agrees with the 
condition found in more primitive vertebrates. 
At the stage of 68 hours (cf. Fig. 103B), the anterior and 
posterior diverticula proceed from a common depression of the 
ventral wall of the duodenum, the ductus choledochus. By 
means of an antero-posterior constriction, the latter becomes 
much more clearly defined as development proceeds (Fig. 187); 
there arise from it also the right and left ventral primordia of 
the pancreas (see below), so that it receives at this stage four 
main ducts, viz.: the right and left ventral pancreatic diverticula 
and the cephalic and caudal hepatic diverticula. On the sixth 
day these four ducts obtain independent openings into the duo- 
denum and the common bile duct thus ceases to exist. The 
relations thus established are practically the same as in the 
adult. 
As the caudal hepatic diverticulum grows out it carries the 
attachment of the gall-bladder with it, so that the latter is then 
attached to the caudal diverticulum, which is thus divided in 
two parts, a distal or ductus hepato-cysticus, and a proximal or 
ductus cystico-entericus. That portion of the liver arising from 
the cephalic diverticulum is thus without any connection with 
the gall-bladder. There seem, however, to be anastomoses 
between the ductus hepato-cysticus and the original cephalic 
duct (ductus hepato-entericus) in the adult, lying in the com- 
missure of the liver; the embryological origin of these appears, 
however, to be unknown. In the course of the development, 
the openings of the two original ducts into the duodenum come 
to lie side by side instead of one behind the other, and the original 
cephalic duct (ductus hepato-entericus) appears to be derived 
maimy from the left lobe, and the ductus cystico-entericus mainly 
from the right lobe of the liver. The actual distribution is, how- 
ever, by no means so simple; the mode of development of the 
lobes of the liver (see below) would explain a preponderant dis- 
