ALIMENTARY TRACT AND ITS APPENDAGES 320 
final terminations of the buds form the secreting and the inter- 
mediate portions the various intercalated and excretory ducts 
that form a branching system opening into the main ducts. 
The successive stages in the development of the pancreas 
may be stated thus (following Brouha): At 124 hours the two 
ventral pancreatic ducts pass anteriorly and a little to the left, 
crossing the cephalic hepatic duct which les between them. 
They are continued into ramified pancreatic tubes which already 
form two considerable glandular masses. The right ventral 
pancreas is united by a very narrow bridge to the dorsal pancreas, 
and the latter is moulded on the left wall of the portal vein, 
while its excretory duct has shifted on the left side of the duo- 
denum nearer the ductus choledochus. At 154 hours the duct. of 
the dorsal pancreas is still nearer to the others, and the three pan- 
creatic ducts enter a single glandular mass, the dorsal portion of 
which, derived from the primitive dorsal pancreas, is moulded on 
the left wall of the portal vein, and is continued into a smaller ven- 
tral portion formed by the fusion of the two ventral pancreases. 
Subsequently, the pancreatic lobes fill up the duodenal loop 
(Figs. 179 and 180), and elongate with this so as to extend from 
one end of it to the other in the adult; the three ducts open 
near the termination of the duodenum (end of distal limb) 
beside the two bile ducts. 
V. Tue Resprratory TRAcT 
The origin of the laryngotracheal groove and the paired 
primordia of the lungs was described in Chapter VI. At the stage 
of 36 somites the laryngotracheal groove includes the ventral 
division of the postbranchial portion of the pharynx, which is 
much contracted laterally so as to convert its cavity into a deep 
and narrow groove. This communicates posteriorly with right 
and left finger-shaped entodermal diverticula (the entodermal 
lung-primordia) extending into the base of the massive pear- 
shaped mesodermal lung-primordia attached to the lateral walls 
of the cesophagus. The mesodermal lung-primordia are con- 
tinuous with the accessory mesenteries,as described in Chapter XI; 
and by them attached to the septum transversum. 
Bronchi, Lungs and Air-sacs. The primitive entodermal 
tubes form the primary bronchi, in which two divisions may be 
distinguished on each side, viz: a part leading from the end of 
