Discuss the function and significance of Constance's red tongue

Constance's red tongue is indicative of her true nature. At first, Constance comes across as quite a passive, non-assertive character; far from shaping her life, she is shaped by it. She allows herself to be browbeaten and manipulated by Professor Night, the unrequited object of her affections. Yet beneath her unassuming exterior beats the heart of a passionate woman, filled with love and desire, emotions she explores throughout her Shakespearean adventures.
Red is traditionally associated with these emotions, and as Constance's true nature is revealed, her red tongue comes to symbolize her growing self-awareness of previously hidden feelings. Red is also the symbol of blood, and its significance lies in the fact that it draws attention to the fine line in Shakespeare's plays—most notably Romeo and Juliet and Othello—between love and violence.