S., Its early philosophy was based on deduction from irrefutable doctrine helped distinguish chiropractic from medicine, provided it with legal and political defenses against claims of practicing medicine without a license, and allowed chiropractors to establish themselves as an autonomous profession.

The same survey showed that most chiropractors generally believed that the majority of their clinical approach for addressing musculoskeletal/biomechanical disorders such as back pain was based on subluxation. This concept was later expanded upon by his son, B. Palmer, and was instrumental in providing the legal basis of differentiating chiropractic from conventional medicine. Impressions are made on the peripheral afferent fiber-endings; these create sensations that are transmitted to the center of the nervous system.

Efferent nerve-fibers carry impulses out from the center to their endings.

Most of these go to muscles and are therefore called motor impulses; some are secretory and enter glands; a portion are inhibitory, their function being to restrain secretion.

concerned with the diagnosis and treatment of mechanical disorders of the musculoskeletal system, especially the spine, under the belief that such a disorder affects general health via the nervous system.

The main chiropractic treatment technique involves manual therapy, especially manipulation of the spine, other joints, and soft tissues, but may also include exercises and health and lifestyle counseling.

Chiropractic has two main groups: "straights", now the minority, emphasize vitalism, "innate intelligence" and spinal adjustments, and consider vertebral subluxations to be the cause of all disease; "mixers", the majority, are more open to mainstream views and conventional medical techniques, such as exercise, massage, and ice therapy.

Chiropractic has had a strong political base and sustained demand for services; in recent decades, it has gained more legitimacy and greater acceptance among conventional physicians and health plans in the U.

Their philosophy and explanations are metaphysical in nature and they prefer to use traditional chiropractic lexicon terminology (e.g., perform spinal analysis, detect subluxation, correct with adjustment).

Many of them incorporate mainstream medical diagnostics and employ conventional treatments including techniques of physical therapy such as exercise, stretching, massage, ice packs, electrical muscle stimulation, therapeutic ultrasound, and moist heat.

Although mixers are the majority group, many of them retain belief in vertebral subluxation as shown in a 2003 survey of 1100 North American chiropractors, which found that 88% wanted to retain the term "vertebral subluxation complex", and that when asked to estimate the percent of disorders of internal organs (such as the heart, the lungs, or the stomach) that subluxation significantly contributes to, the mean response was 62%.

A 2008 survey of 6,000 American chiropractors demonstrated that most chiropractors seem to believe that a subluxation-based clinical approach may be of limited utility for addressing visceral disorders, and greatly favored non-subluxation-based clinical approaches for such conditions. Palmer repudiated his earlier theory that vertebral subluxations caused pinched nerves in the intervertebral spaces in favor of subluxations causing altered nerve vibration, either too tense or too slack, affecting the tone (health) of the end organ. Palmer theorized that the nervous system controlled health: "Physiologists divide nerve-fibers, which form the nerves, into two classes, afferent and efferent.