the origin and nature of emotions-第14章

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r　passing　gall…stones　and　urinary　calculi；　urgent　motor　stimuli　are　awakened　by　pain。　For　each　of　these　diversified　pains　the　consequent　muscular　action　is　specific　in　type；　distribution；　and　intensity。　　This　statement　is　so　commonplace　that　we　are　apt　to　miss　the　significance　and　the　wonder　of　it。　　It　is　probable　that　every　nerve…ending　in　the　skin　and　every　type　of　stimulation　represents　a　separate　motor　pattern；　the　adequate　stimulation　of　which　causes　always　the　same　response。

Let　us　pass　on　to　the　discussion　of　another　and　perhaps　even　more　interesting　type　of　pain；　that　associated　with　infection。　Not　all　kinds　of　infection　are　painful；　and　in　those　infections　that　may　be　associated　with　pain　there　is　pain　only　when　certain　regions　of　the　body　are　involved。　　Among　the　infections　that　are　not　associated　with　pain　are　scarlet　fever；　typhoid　fever；　measles；　malaria；　whooping…cough；　typhus　fever；　and　syphilis　in　its　early　stages。　The　infections　that　are　usually；　though　not　always；　associated　with　pain　are　the　pyogenic　infections。　　The　pyogenic　infections　and　the　exanthemata　constitute　the　great　majority　of　infections　and　are　the　basis　of　the　discussion　which　follows。

I　will　state　one　of　my　principal　conclusions　first；　_i。　e_。；　that　the　only　types　of　infection　that　are　associated　with　pain　are　those　in　which　the　infection　may　be　spread　by　muscular　action　or　those　in　which　the　fixation　of　parts　by　continued　muscular　rigidity　is　an　advantage；　and；　further；　as　a　striking　corollary；　that　the　type　of　infection　that　may　cause　muscular　action　when　it　attacks　one　region　of　the　body　may　cause　no　such　action　when　it　attacks　another　region。

The　primary；　and　perhaps　the　most　striking；　difference　between　the　painless　exanthemata　and　the　painful　pyogenic　infections　is　that　in　the　case　of　the　exanthemata　the　protective　response　of　the　body　is　a　chemical　one；the　formation　of　antibodies　in　the　blood；　which　usually　produce　permanent　immunity；while　the　response　to　the　pyogenic　infections　is　largely　phagocytic。　　In　the　pyogenic　infections；　in　order　to　protect　the　remainder　of　the　body；　which；　of　course；　enjoys　no　immunity；　every　possible　barrier　against　the　spread　of　the　infection　is　thrown　about　the　local　point　of　infection。　How　are　these　barriers　formed？　　First；　lymph　is　poured　out；　then　the　part　is　fixed　by　the　continuous　contraction　of　the　neighboring　muscles　and　by　the　inhibition　of　those　muscles　that；　in　the　course　of　their　ordinary　function；　would　by　their　contractions　spread　the　infection。　Wherever　there　is　protective　muscular　rigidity　there　is　also　pain。　On　the　other　hand；　in　pyogenic　infections　in　the　substance　of　the　liver；　in　the　substance　of　the　kidney；　within　the　brain；　in　the　retroperitoneal　space；　in　the　lobes　of　the　lung；　in　the　chambers　of　the　heart　and　in　the　blood…vessels　of　the　chest　and　the　abdomen；　in　all　locations　in　which　muscular　contractions　can　in　no　way　assist　in　localizing　the　disease；　pyogenic　infections　produce　no　muscular　rigidity　and　no　pain。　　Apparently；　therefore；　only　those　infections　are　painful　which　are　associated　with　a　protective　muscular　contraction。　This　explains　why　tuberculosis　of　the　hip　is　painful；　while　tuberculosis　of　the　lung　is　painless。

There　is　a　third　type　of　pain　which　modifies　muscular　action　in　a　curious　way。　　We　have　already　stated　that　local　pain　serves　an　adaptive　purpose。　　In　this　light　let　us　now　consider　headache。　Headache　is　one　of　the　commonest　initiatory　symptoms　of　the　various　infections；　especially　of　those　infections　which　are　accompanied　by　no　local　pain　and　by　no　local　muscular　action。　In　peritonitis；　cholecystitis；　pleurisy；　arthritis；　appendicitis；　salpingitis；　child…birth；　in　obstructions　of　the　intestinal　and　the　genito…urinary　tract；　in　short；　in　those　acute　processes　in　which　the　local　symptoms　are　powerful　enough　to　govern　the　individual　as　a　whole；to　make　him　lie　down　and　keep　quiet；　refuse　food　and　possibly　reject　what　is　already　in　the　stomach；　in　all　these　conditions　there　is　rarely　a　headache；　but　in　the　diseases　in　which　local　pain　is　absent；　such　as　the　exanthemata；　typhoid　fever；　and　auto…intoxication；　which　have　no　dominating　local　disturbances　to　act　as　policemen　to　put　the　individual　to　bed　and　to　make　him　refuse　food　that　he　may　be　in　the　most　favorable　position　to　combat　the　oncoming　disease；　in　such　cases　in　which　these　masterful　and　beneficent　local　influences　are　absent　we　postulate　that　headache　has　been　evolved　to　perform　this　important　service。

On　the　hypothesis　that　it　is　good　for　the　individual　who　is　acutely　stricken　by　a　disease　or　who　is　poisoned　by　autointoxication　to　rest　and　fast；　and　that　the　muscular　system　obeys　the　imperial　command　of　pain；　and　in　view　of　the　fact　that　the　brain　is　not　only　in　constant　touch　with　the　conditions　of　every　part　of　the　body　but　that　it　is　also　the　controlling　organ　of　the　body；　one　would　expect　that　in　these　diseases　the　major　pain　whose　purpose　it　is　to　govern　general　muscular　action　would　be　located　in　the　head　and　there　we　find　it。　How　curious　and　yet　how　intelligible　is　the　fact　that；　though　a　headache　may　be　induced　by　even　a　slight　auto…intoxication；　an　abscess　may　exist　within　the　brain　without　causing　pain。　When　an　obliterative　endarteritis　is　threatening　a　leg　with　anemic　gangrene；　or　when　one　lies　too　long　in　the　same　position　on　a　hard　bed；　there　is　threatening　injury　from　local　anemia；　and　as　a　result　there　is　acute　pain；　but　when　the　obliterative　endarteritis　threatens　anemia　of　the　brain；　or　when　an　embolism　or　thrombosis　has　produced　anemia　of　the　brain；　there　may　be　no　accompanying　pain。　The　probable　explanation　of　the　pain　which　results　in　the　first　instance　and　the　lack　of　pain　in　the　second　is　that　in　the　former　muscular　action　constitutes　a　self…protective　response；　but　in　the　other　it　does　not。　Diseases　and　injuries　of　the　brain　are　notoriously　difficult　to　diagnosticate。　　This　may　well　be　because　it　has　always　been　so　well　protected　by　the　skull　that　there　have　been　evolved　within　it　few　tell…tale　self…protective　responses；　so　that　in　the　presence　of　injury　and　disease　within　itself　the　brain　remains　remarkably　silent。　It　should　occasion　no　surprise　that　there　are　in　the　brain　no　receptors；　the　mechanical　stimulation　of　which　can　cause　pain；　because　its　bony　covering　has　always　prevented　the　adaptive　implantation　within　it　of　contact　pain　receptors。　　Dr。　Frazier　tells　me　that　in　the　course　of　his　operations　on　the　brains　of　unanesthetized　patients　he　is　able　to　explore　the　entire　brain　freely　and　without　pain。　From　my　own　experience　I　am　able　to　confirm　Dr。　Frazier's　observation。　In　addition；　the　two…stage　operation　for　the　excision　of　the　Gasserian　ganglion　provides　an　observation　of　extraordinary　interest。　If　at　the　first　seance　the　ganglion　is　exposed；　but　is　not　disturbed　except　by　the　iodoform　gauze　packing；　then　on　the　following　day　the　gauze　may　be　removed；　the　ganglion　picked　up；　and　its　branches　and　root　excised　without　anesthesia　and　without　pain。　The　same　statement　and　explanation　may　be　made　regarding　the　distribution　of　pain　receptors　for　physical　contact　within　the　parenchyma　of　the　liver；　the　gall…bladder；　the　abdominal　viscera；　the　spleen；　the　heart；　the　lungs；　the　retroperitoneal　tissue；　the　deep　tissue　of　the　back；　the　vertebrae；　and　in　certain　portions　of　the　spinal　cord。　Just　what　is　the　distribution　of　the　receptors　for　heat　and　for　cold　I　am　unable　to　state；　but　this　much　we　do　know；　that　without　anesthesia　the　intestines　may　be　cauterized　freely　without　the　least　pain　resulting；　and　in　animals　the　cauterization　of　the　brain　causes　no　demonstrable　change　in　the　circulatory　or　respiratory　reactions。　It　is　probable　therefore　that　the　distribution　of　the　pain　receptors　for　physical　contact　and　for　heat　are　limited　to　those　parts　of　the　body　that　have　been　exposed　to　injurious　contacts　with　environment。

Of　special　significance　is　the　pain　which　is　due　to　cold；　which　increases　muscular　tone　and　produces　shivering。　　The　general　increase　in　muscular　tone　produces　an　interesting　postural　phenomenon：　the　limbs　are　flexed　and　the　body　bent　forward；　a　position　which　probably　is　due　to　the　fact　that　the　flexors　are　stronger　than　the　extensors。　As　muscular　action　is　al