Tongue

The tongue was a body part used for tasting and communication.

Some Time Lords could determine what was in a substance by touching it to their tongue. Romana tasted a mineral with her tongue on Skaro to guess its composition. (TV: Destiny of the Daleks) The Tenth Doctor was able to tell not only that the Sycorax were using blood magic, but what blood type they were using. (TV: The Christmas Invasion) While visiting Queen Victoria, he could tell there was mistletoe oil on some woodwork by licking it. (TV: Tooth and Claw)