Character of the tongue: Tongue body is stiff, rigid and fails to stretch and retract.
Clinical significance: Stiff tongue with red color and few fluid is due to excess heat consuming the fluid; stiff tongue with thick and slimy fur is caused by wind-phlegm obstructing the collaterals; sudden tongue stiffness and inability to speak with numb limbs and dizziness are the signs of apoplexy.
Also see Transportation and Metabolism of Body Fluid.