374 RICHARD E. SCAMMON 



mediana and apparently even the anterior left ramus may be 

 carried dextrally until they face the right. Apparently also 

 any intermediate step between this extreme and the embryonic 

 type described above may exist. When rotation first takes place 

 and before the cystic duct begins to shift upward and forward 

 the ostia of the minor anterior ducts remain quite close to that 

 of the main left hepatic duct. With this change however the 

 curve formed by the extreme anterior part of the ductus choledo- 

 chus and the cystic duct is gradually obliterated so that the two 

 ducts come to form together a slender tube which extends antero- 

 posteriorly in frontal plane, and the ostia of the rami which for- 

 merly were on the anterior surface of this curve come to lie on one 

 side or the other of duct and are separated by its dorsal surface. 

 Figures 51 and 52 are of a reconstruction of the biliary apparatus 

 at a stage immediately after a distinct dextral rotation of the duc- 

 tus choledochus has taken place and before the dorso-anterior 

 migration of the cystic duct and gall bladder is very noticeable. 

 Had this specimen continued its growth, if one may judge from 

 reconstruction's of later embryos, the cystic duct would probably 

 be carried forward and upwards in such a way that it would inter- 

 vene between +;he left medial ramus and the left main hepatic 

 duct in such a way that it would receive the opening of the former 

 on the right hand side and the latter on the left. Figures 53 and 

 54 of an embryo 33.1 mm. in length shows a somewhat later stage 

 in which the cystic duct is being forced forward and the right 

 medial ramus which formerly lay almost in the median line is 

 being carried over to the right side of the duct. 



Some reconstructions which illustrate the results brought about 

 by the above processes may be illustrated here as they also show 

 the changes which take place in the major ducts and gall bladder 

 in the later periods of embryonic development. 



Figure 23 of a very late embryo 18 cm. in length shows a vari- 

 ant in which the left medial ramus has remained attached to 

 the main left hepatic duct but in which the right medial ramus 

 arises from the ductus choledochus. Except for this change, the 

 rami have remained in their early embryonic position. Figure 



