378 RICHARD E. SCAMMON 



lies to the left of the median line and the cystic duct is inclined 

 to the right as well as upward to meet the median hepatic pouch or 

 ductus choledochus. 



At 19 mm., the gall bladder is widely separated from the ductus 

 choledochus and inclined at a distinct angle to it. The cystic 

 duct is decidedly elongated and extends upward to the right and 

 decidedly forward to meet the ductus choledochus. This elonga- 

 tion is due in part to the increase in size of the left omphalo- 

 mesenteric vein, which lies in this region between the gall bladder 

 below and the ductus choledochus above, and perhaps also in 

 part to the great growth of the hepatic trabeculae which takes 

 place at this time. Probably the increased length of the duct is 

 derived in part at least from the lower part of the ductus chole- 

 dochus from which the anterior end of the cystic duct seems to 

 be separating. This separation is peculiar in that it takes place 

 mesially more rapidlj' than laterally, thus forming a distinct 

 l)ocket which is bounded below by the cystic duct, above by the 

 floor of the ductus choledochus and laterally by the sides of these 

 structures which are still confluent. This formation is only 

 temporary. . 



At 20.() mm. (fig. 50, and fig. 26, F) the cystic duct is still 

 more elongated and joins the floor of the ductus choledochus 

 nearly at right angles to it. The gall bladder is shifted downward 

 until its long axis is almost in the vertical plane of the embryo 

 and at right angles to the ductus choledochus. It is drawn out 

 until the sac appears as little more than the expanded end of the 

 cystic duct. 



The shifting of the ductus choledochus and the rotation of its 

 anterior end, described on page 371, now takes place, and the 

 cystic duct and a part of the gall bladder share in this displace- 

 ment. The posterior half of the gall bladder remains almost 

 in the position occupied in the preceding stage or is shifted a 

 little dorsally, while the anterior half and the cystic duct form 

 together an abruptly curved tube which extends to the right and 

 dorsally. In this way there is formed a distinct flexure in the 

 middle part of the gall bladder. This is illustrated by an embryo 

 28 mm. in length (figs. 51 and 52). 



