DEVELOPMENT OF LIVER AND PANCREAS 247 



However, in general, a study of the models shows a close shni- 

 larity in their positions. Theue is a constant rotation of the 

 liver towards the right and with this is a similar one of the 

 hepatic ducts. In this rotation the right ducts come to be more 

 dorsal in position, the left more ventral. The right lateral 

 divisions would thus be dorsal to the right medial and the reverse 

 should be true for the left. In general such an arrangement is 

 found. A variation in the length of the different ducts is present. 

 However, there is qute a definite relation in the total lengths 

 of ducts in the different embryos. In a 15 mm. embryo the 

 common duct is quite short but the greater length of the hepatic 

 ducts compensates for this reduction. In a 35 mm. embryo the 

 common duct is long, the hepatic ducts and their radicles divide 

 shortly. 



III. THE DEVELOPMENT OF THE PANCREAS AND PANCREATIC 



DUCTS 



1. Literature 



The literature concerning the development of the amphibian 

 pancreas like that regarding the liver is divisible into two periods, 

 and Goette's work ('75) may again be said to mark the begin- 

 ning of the newer one. The older observers mainly considered 

 the pancreas as a part of the liver, or a modified lobe of that 

 organ. 



A list of the investigators describing the development of the 

 pancreas will be found included in the tabular classification of 

 the literature on the development of the liver (table 2). 



Goette ('75) in his studies on the development of the Bombin- 

 ator recognized three distinct pancreatic anlagen, two ventral 

 and one dorsal. The dorsal one he described as placed just 

 caudal to the gastroduodenal loop. The two symmetrical ven- 

 tral anlagen develop from the primitive hepatic duct. Of 

 these the right grows dorsalward to join the ventral growing 

 dorsal anlage. The right duct changes in position until it opens 

 into the left side of the hepatic duct. The united right and left 

 duct then separates from the common bile-duct. Apparently 



