The ethmoid bone is situated in front of the sphenoid, and forms the lower part of the division separating the cranium from the face. It consists of two lateral halves, separated by a perpendicular plate (the lamina). Each half in front consists of a number of thin fragile plates of bone, rolled up into small scrolls (ethmoidal cells), and attached to the cribriform plates, i.e. two bony plates having a number of small holes in them, by which the olfactory nerves escape from the cranium into the nostrils. At the sides it throws up two winglike processes, which articulate with the frontal bones.