Aortic arches 7-4 



Atrium 



V Hello-umbilical vein 



L. umbilical vein 



FIG. 88. Ventral reconstruction of a 3.2 mm. embryo, showing vessels (His). 



Umbilical vein 



Olfactory pit 

 Mandibular arch 



Common cardinal vein 



) ...Allantois 



Umbilical artery 



Placental attachment 



FIG. 89. Lateral view of human embryo of 4.2 mm., showing aortic arches and venous trunks (His). 

 mx, Maxillary process; jv., anterior cardinal vein; c.v., posterior cardinal vein; ot, otocyst. 



