514 



URO-GENITAL SYSTEM. 



liver. This portion of the old trunk afterwards forms the 

 upper part of the inferior vena cava, whose lower portion is 



Fig. 148. Venous system of the 

 embryo.* 



Fig. 149. Formation of the true or per- 

 manent venous system. t 



* 1, Duct ,f Cuvier. 2, Place where all the veins unite and pour their con- 

 tents into the inferior extremity of the heart (future auricle). 3, Anterior 

 cardinal vein. 6, Umbilical vein. 7, The same vein near the liver (which is 

 rot in the plate, neither the afferent and efferent hepatic veins). 8, Omphalo- 

 mesentcric vein. 9, Inferior vena cava. 12, Posterior cardinal veins. Kolliker, 

 " Entwickelungsgeschichte.") 



t A. Period of formation. 1, Left superior vena cava. 2, Eight superior 

 vena cava. 3, Inferior vena cava. 4, 5, Inferior cardinal veins (future azygos). 

 7, Anastomosis between the two anterior cardinal veins, future left brachio- 

 cephalic trunk. 8, 9, 10, Future jugular and subclavian veins. 



B. Permanent venous trunks (as in the adult). These vessels (as in the Fig. 

 A) are represented as if looking at the posterior portion of the body. 1, Oblit- 

 erated left superior vena cava. 6, liight vena innominata. 7, Left vena 

 innominata. 8, Subclavian. 13, Trunk of the hemi-axygos. 18, Left superior 

 intercostal. 19, 20, Superior and inferior portions of the left azygos. 



