Book 31, Question 52
How does a chick breathe inside a sealed egg?
An eggshell looks solid, but it is covered with thousands of tiny holes called pores.
Oxygen slips in through the pores, and carbon dioxide slips out. Inside the egg at the blunt end is a small pocket of air that the chick uses just before it hatches. The shell keeps germs out but still lets the baby bird breathe.