Spock would feel the smile on Bones' mouth, despite his constant attention to those long fingers. You think? he thought lazily, feeling the fingers slide together.

It was clear how much Spock was getting off on this, and it spurred him to try harder, to try new things, to make his tongue flick lightly on the fingertips before pulling them out and seeking the flesh between his fingers, spreading them and tonguing, sucking on the webbing.