284 



THE DEVELOPMENT OF THE VASCULAR SYSTEM 



of the digits, the vv. cephalica et basilica become distinct as in embryos of 35 mm. but later are 

 again connected by a plexus on the dorsum mani, as in the adult (Evans in Keibel and Mall). 

 In the lower extremity the fibular border vein persists as the v. saphena parva which runs 

 deep as the v. glutea inferior and drains into the hypogastric portion of the posterior vena cava. 

 The v. saphena magna and the v. femoralis arise later and join the v. ischiadica which drains into 

 the posterior cardinal vein. The veins to accompany the arteries are the last to develop. 



Dorsal subclavian 

 vein 



Vena ulnaris 

 prima. 



V.thoraco-epiaastrika. 



V.linguo- facial 1 5 



V. lingua- facialis 



Ant. cardinal vein 



Dorsal .subclavian 



vein 

 Com. cardinal 

 Vein 



V.uh 



nans prim 



Poshcardmal vein 



V. thoraco-epioastrica 

 Ventral subclavian vein 



VcephaJ, 



anonynta d'extra. 



Fig. 277. — Four reconstructions of the veins of the right arm (after F. T. Lewis). A, 10 mm. embryo; 

 B, 11. 5 mm. embryo; C, 15 mm. embryo; D, 22.8 mm. embryo. 



FETAL CIRCULATION 



During fetal life the placental blood enters the embryo by way of the large 



umbilical vein and is conveyed to the liver (Fig. 278). There it mingles with the 



small amount of venous blood brought to the liver by the portal vein. It is carried 



to the inferior vena cava either directly, through the ductus venosus, or indirectly 



