may accompany many otlher sensations besides those whicl -4fl on urt5f have a right to be-called s-pcifical1y painful.This un- ON oopleasant feeling may be associated with touch in the form CE rn s TAIN ACSln PEs cv T s OFT PAIN.of tickling or itclhing, with pressure, as an intolerable sensa- CEIRTAliNASPECTS OF PA iT3* tion we call "crushing paia," with heat as " burning," and DELIVERED BEFORE THE SHEFFIELD MEDICO-CHIRURGICAL with1 cold as that disagreeable state tht w.e know so well SOCIETY, DECEMBER 8TH, 1921.whlen our lhands and feet are chilled.But it is a matter of no importance fronm the point of view of the organism wlhetlher the sensatidn evoked be. a strictly HENRY HEAl), M.D., F.R.S. specific one of pain, or whit slhould be more truly callted discomfort.Botlh lead to the production of reflexes tlhat PAIN and disconmfort are the oldest defensive reactions of the tend to remove the affected part or even the whole animal organism, and potentially unpleasant stimuli form the basis from the place or object prQductive of such unpleasant of most primitive reflexes.Even the simplest animal slluns experiences.Reactions of.this kind are impulsive a.nd pain and moves in the direction of pleasure.All suclh urgent; once they come into beina, the movements they impulsive actions allow of little choice, and,any part of tlhe produce are uncontrolled; they permit of no choice.It is body exposed to a lharmful form of stimulation is urgently therefore most important that the impulses whiclh undbrlie wlthdrawvn.Sensory impulses capable of evoking pain or any of these disagreeable sensations should be diminished in discomfort are tllerefore most important factors in tlhe life extent, or actually inhibited, in favour of those sensory of even thelighlest organism, althlougal their action may be -impressions more capable of leading to discriminative action.almost automatic.But, on the other hand, tlle mechanism underlying the In man, hlowever, where they not only cause impulsive production of pain and discomfort mist remain in full reflexes, but also produce conscious physiological activity, so that it can discomfort, pain is the most urgent play its part in defence of the or- symptom with which the medical ganism, whienever noxiotus stimuli man is cormpelled to deal.At the reacb a higlh grade of intensity.samrhe time it forms one of the most Fthalamo Such dominance of a higlher centre important diagnostic aids, if rightly over tlle activities of another, 'sub.inteirpreted.But in so many cases -F.cortlcO) serving more primitive modes of its meaning is misunderstood; the .thaam.response, is exemplified by tlle rela- initonhsity of the patient's suffering tion between tlhQ cortex and optic cries for relief, and attention is more Ni thalamus.This is the end-station often focussed on easing the pain aI a for all t se afferent ipulses sub- than upon its diagnostic significance._-1Sseving the more affective forms of
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Helen Ivy Head (1922) studied this question.