placenta
"In this way, the placenta is like the screen on a window of your house. Rain and pollen from outside can get in through the holes of your screen. But bugs are too big to fit through and get inside. And the smell of your cooking can waft outside through the holes in the screen - but you can't."
"As the doctor explained today, my placenta is like a big pillow covering the front of my uterus"
"Attached to the wall of the uterus, the placenta is like a spongy cake that supplies the fetus with nutrients and oxygen through the umbilical cord."
"The placenta is like nature's own built-in Brita filter system, but I was going to help its efforts as much as possible to reduce exposure to the fetus."

METAMIA is a free database of analogy and metaphor. Anyone can contribute or search. The subject matter can be anything. Science is popular, but poetry is encouraged. The goal is to integrate our fluid muses with the stark literalism of a relational database. Metamia is like a girdle for your muses, a cognitive girdle.