“Pressure on nerves causes irritation and tension with deranged functions as a result. Why not release the pressure? Why not adjust the cause instead of treating the effects? Why not?”
“Life is the expression of tone. In that sentence is the basic principle of chiropractic. Tone is the normal degree of nerve tension. Tone is expressed in functions by the normal elasticity, activity, strength, and excitability of the various organs, as observed in a state of health. Consequently, the cause of disease is any variation of tone–nerves too tense or too slack.”
D.D. Palmer, in Text-Book of the Science, Art and Philosophy of Chiropractic for Students and Practitioners