208 



THE SIXTH DAT. 

 Fig. 63. 



[chap. 



sm& 



DlAGKAir OP THE VENOTJS CIRCULATION DURING THE LATER DATS OP 



Incubation. 



H. heart. V. S. R. right vena cava superior. V. S. L. left vena cava superior. 

 8. V. sinua venoaus. The two venae cav® superiores are the original 

 'ductus Cuvieri,' they still open into the sinus venosus and not in- 

 dependently into the heart. /. jugular vein. SU. V. superior vertebral 

 vein. W. vein for the wing. V. C. I. vena cava inferior, which receives 

 most of the blood from the inferior extremities, etc. HP. Hepatic veins, 

 which fall into the vena cava inferior. D. V. ductus venosus. P. V. portal 

 vein. M. a vein bringing blood from the intestines into the portal vein. 

 0/. omphalo-mesaraic vein. J/^ umbilical vein. The three last menticned 

 veins unite together to form the portal vein. 

 The remnants of the inferior cardinal veins are not shewn. 



