468 



Anatomy and Development of Veins of Chelonia 



The omphalo-mesentcric veins of an embryo of about 12 mm. — In this 

 stage the separation of the right hepatic from the mesenteric portal is 

 still more complete. The original connection between the two veins is 

 now almost entirely reduced to sinusoids (not shown in Fig. 6). There 

 still remains, however, one, sometimes two, direct anastomosing branches 

 which may represent the remains of the original connections. These, 

 when present, occur just after the mesenteric portal enters the liver. 



We find at this stage, in addition to the original connections between 

 these two veins, a series of three or four anastomosing branches that 



SINUS VENOSUS 



GASTRIC VEIN 



,''- VESENTER'C PORTAL 



RIGHT HEPATIC 



Fig. 6. Frontal reconstruction of the liver veins of a 12 mm. embryo of 

 Kinosternon pennsylvanicum. Ventral view. 



appear to be new formations. As shown by Figs. G and 7 " A;' they take 

 a somewhat curved course through the liver and open into the dorsal 

 side of the right hepatic vein. They appear to be formed through the 

 fusion of some of the sinusoids ventral to, and on the right side of, the 

 right hepatic vein. The first indications of these curved veins appear 

 in the 11 mm. stage. 



In the 12 mm. stage these curved veins have reached their maximum 

 of development. The first one to be given ofl: from the mesenteric portal 

 on entering the liver is found a short distance caudad of the gall bladder, 

 while the other two pass dorsal to it, as in Fig. 7. When the fourth is 



