

Aortic arches 1-4 



Atrium 

 ^VYl Vitello-umbilical vein 



r, V... ' i 

 \ V^^-^H L. umbilical vein 



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



Olfactory pit 

 ' Mahdibular arch 



' Common cardinal vein 



*.: Vitelline vein 

 'Umbilical vein 



Umbilical vein 



1 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.ti., posterior cardinal vein; ot, otocyst. 



