In Chinese medicine the Heart regulates the flow of Blood. Disharmonies of the Heart are often revealed in the condition of the tongue and/or the face. The Heart stores Shen, one of the fundamental substances which may be loosely equated with vital spirit, and clear healthy Shen is often recognized as sparkle or light in the eye. When the Shen-storing of the Heart is impaired, symptoms of deficient Shen may arise, such as unbalanced feelings, unclarity of speech, insomnia, excessive dreaming or forgetfulness. In more extreme cases there may appear serious mental disorders.