If the patient willfully attempts to deceive the palpater, nerve-tracing might as well be abandoned except in those extreme cases where the patient will flinch against his will on account of extreme sensitiveness. Use of Second Hand As far as possible, the second hand is placed opposite the tracing hand and steadily supports the body; its position changes with changes in the position of the first. If the arm is to be examined it had best be held away from the body, and the part to be examined held between the two hands. Position of Patient For tracing nerves in the neck, back, and upper extremities, the patient should sit easily. For lumbar, abdominal, or pelvic tracing, or for tracing in the lower extremities, have patient lie on side or back. Do not hesitate to change the position of the patient as often as is necessary to secure easy access to the part to be examined and relaxation of the patient’s muscles. Never allow the assumption of a strained position during tracing; the sensation of cramped muscles may be confused with sensations of nerve tenderness. SUBLUXATIONS Definition A vertebral subluxation is a displacement, less than a dislocation, in which the chief element is the partial loss of normal apposition of the articular surfaces of the subluxated vertebra with those of the vertebra above or below, or both. Or, Vertebral subluxation is a permanent partial dislocation. How Produced Subluxations are primarily caused by trauma--falls, blows, strains, etc., being the chief factors. Hereditary weakness in structure of some part predisposes by rendering that portion more easily displaced. Subluxations are never hereditary but may be congenital through violent or instrumental delivery into the world or may _appear_ hereditary because they occur shortly after birth through the effect of light jars upon the hereditarily weakened segments of the spinal column. They are always the result of concussions of forces; never of forces acting entirely _within_ the organism. They result from the contact of the body with its environment. It has been said that muscular action in response to peripheral irritation may produce subluxation. The laws of reflex action render this impossible. Given a normally aligned vertebra, and consequently normal nerves and a normal reflex arc in that segment, the ventral horn cells respond to a _slight_ peripheral stimulus by exciting muscular contraction on the _same_ side with the irritation. If the irritation be sufficiently increased, the response occurs on _both_ sides but most strongly on the side from which the irritation comes. Greater irritation merely serves to cause greater distribution of the responsive action. (See any standard physiology on reflex action.) In no case will the difference between the contractions of muscles on the two sides be sufficient to displace a normally aligned vertebra. Nature has provided against that contingency.