The tongue  diagnosis  theory considers that the zang-fu organs' diseases are reflected on the surface of tongue by rules of their own ( Fig.  I - 6):

The tongue tip can reflect the pathological changes in the heart and lungs. The bilateral sides of the tongue can tell the pathological changes in the liver and gallbladder. The center of the tongue can show the pathological changes in the spleen and stomach. The tongue root can indicate the pathological changes in the kidneys, intestines and bladder.  This theory simply means that some zang-fu organs' diseases have some rules on the changes of tongue manifestations, but they arc not absolute and should be analyzed in combination with other symptoms. To learn more information about the relationship of zang-fu organs, please click The Five Zang-Organs.