She looked down at Lily fondly. "Her skull isn't fully developed. Literally. There are these things called fontanels, and they're these spaces of cartilage between the bones of her skull. They have that because they need to be able to squeeze through the birthing canal. That's why some babies come out with cones shaped heads."
"The coolest chemical, Francis," she said sleepily, lying back in the bed. "It's instrumental in childbirth! And other stuff."
"It's an instrumental part of the positive feedback loop of childbirth, Francis! The baby's head pushes against the uterine wall, oxytocin is released to move the baby deeper into the birthing canal, causing the baby's head to push more against the uterine wall, which causes more oxytocin to be released! It's crazy!"
