A. Hairy tongue. B. Brown hairy tongue.
To read about hairy tongue in context, click here:
Fitzpatrick's Dermatology in General Medicine, 8e: Chapter 76. Biology and Pathology of the Oral Cavity
Additional readings about hairy tongue:
The Atlas of Emergency Medicine, 4e: Chapter 6. Oral Conditions
The Color Atlas of Family Medicine, 2e: Chapter 37. Black Hairy Tongue