D.D. Palmer emphasized the importance of “tone” in the dynamics of health and disease. “Life is an expression of tone. Tone is the normal degree of nerve tension. Tone is expressed in function by normal elasticity, strength, and excitability…the cause of disease is any variation in tone.” [3] B.J. Palmer acknowledged the role of muscular function in maintaining life. “Life is motion; motion is life. The absence of motion is death…in human beings, motion is produced by muscles…that which moves muscles is nerve force. ” [4]
— DD Palmer, BJ Palmer