180 THE DEVELOPMENT OF THE CHICK 
of the anterior intestinal portal becomes incorporated in the 
floor of the intestine as the anterior intestinal portal retreats 
backwards, and the original dorsal liver diverticulum therefore 
becomes anterior or cephalic and the ventral becomes posterior 
or caudal (Fig. 103 B). Before this transposition occurs, how- 
ever, the diverticula have grown forward towards the sinus 
venosus in the ventral mesentery of the stomach, the anterior 
diverticulum above and the posterior diverticulum below the 
ductus venosus. The stretch of entoderm between the two liver 
diverticula thus lies in the angle made by the union of the two 
omphalomesenteric veins. At the stage of 26 somites, the anterior 
diverticulum has grown forward above the ductus venosus 
to the level of the Cuvierian veins and is large and flattened 
laterally. The posterior diverticulum is barely indicated at this 
time. 
The anterior diverticulum was originally described as left and the 
posterior as right (Goette, 1867), and this description was taken up 
by Foster and Balfour. This was corrected by Felix (1892). Subse- 
quent writers do not agree exactly as to the time or precise relations 
of the diverticula; however, it is generally agreed that the two diver- 
ticula are subdivisions of a common hepatic furrow, inasmuch as the 
entoderm between them lies below the level of the entoderm in front 
and behind (Fig. 103 B). Brouha maintains that at first the hepatic 
furrow lies in front of the anterior intestinal portal, and that the latter 
secondarily moves forward so as to include the hepatic furrow, which 
later again comes into the floor of the intestine with the definitive retreat 
of the anterior intestinal portal. This view does not rest on very secure 
evidence, and is probably based on interpretation of slight individual 
variations as successive stages of development. Choronschitzky places the 
time of appearance of the hepatic diverticula at about the thirty-sixth 
hour. It is probable, however, that this is too early. I have found the 
first unmistakable diverticulum at a stage of 22 somites, a slight rudi- 
ment of the anterior diverticulum in the anterior intestinal portal. 
At the 30s stage the anterior or dorsal diverticulum has ex- 
panded much more, mainly to the left of the middle line, as though 
to embrace the ductus venosus, and the posterior or ventral 
diverticulum has an even greater development and embraces 
the right side of the ductus venosus, but it does not extend as 
far forward as the anterior diverticulum. Both diverticula 
now branch rapidly and profusely, forming secondary anasto- 
x 
“ 
