THE ALLANTOIS 



349 



arteries and the same number of allantoic veins. The allantois 

 also receives the fetal urine. 

 As the true placental circulation is established and the visceral 



PP- 



FIG. 107 



< 



e, embryo; a, amnion; a', alimentary canal; vt, vitelline membrane; a/, amniotic 

 fold; ac, amniotic cavity; y, yolk; al, allantois. 



plates close the abdominal cavity, the allantois is constricted 

 at the umbilicus so as to be divided into two parts. That 

 outside the body shrivels and is cut away with the umbilical 



