DEVELOPMENT OF LIVER AND PANCREAS 237 



dorsal to the right medial ramus. It soon breaks up into dorso- 

 lateral and ventro-medial branches. Both of these branches 

 are very long. At the attachment of the cystic duct to the lateral 

 branch there is a further division of the lateral again into medial 

 and lateral radicles. The medial branch has anastomoses with 

 the right medial hepatic ramus. Its further division is in a 

 dorso-ventral plane. In a 35 mm. embryo the right lateral 

 ramus divides into dorsal and ventral branches (fig. 44) . There 

 is another division of the dorsal branch and the cystic duct is 

 attached to the dorsal one of this last division. Frequent an- 

 astomoses are formed between the tubules of the dorsal and ven- 

 tral branches, and between those of the dorsal branch and those 

 from the right medial hepatic ramus, as also of the left medial 

 ramus. 



Right medial ramus. The right medial hepatic ramus of a 

 14 mm. embryo as shown by model is very simple (fig. 39). It 

 joins with the left medial ramus, the further division of this 

 common ramus is into right and left branches. The division of 

 the medial ramus is very short and its lateral and medial branches 

 long. Caudally directed tubules are given off from the lateral 

 branch. The medial branch here is connected with the right 

 lateral ramus. The medial branch divides dorso-ventrally 

 into tubules. In a 15 mm. embryo (fig. 42) the medial hepatic 

 ramus is again very simple. It is short and divides into lateral 

 and medial branches of which the latter is given off almost at 

 right angles and from its anterior surface are given off several 

 tubules. The medial hepatic ramus in a 20 mm. embryo as in a 

 14 mm. one is joined with the left medial ramus (fig. 43). The 

 resulting common ramus divides into a right dorsal {R. Br.) 

 and a left ventral branch (L. Br.). From the right dorsal branch, 

 dorso-lateral tubules are given off some of which are directed 

 caudally. In a 35 mm. embryo (fig. 44) the right medial ramus 

 is on the same horizontal plane as the right lateral. Its divisions 

 are also into dorsal and ventral branches. Many anastomoses 

 are found between the tubules of this ramus. Tubules from 

 this ramus join those from the right lateral and from the left 

 medial ramus. 



