the origin and nature of emotions-第15章

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obably　is　due　to　the　fact　that　the　flexors　are　stronger　than　the　extensors。　As　muscular　action　is　always　accompanied　by　heat　production；　the　purpose　of　the　muscular　contraction　and　the　shivering　is　quite　certainly　caused　by　cold　to　assist　in　the　maintenance　of　the　normal　body　temperature。

We　have　now　discussed　many　of　the　causes　of　pain　and　in　each　instance　we　have　found　an　associated　muscular　action　which　apparently　serves　some　adaptive　purpose　（Figs。　24　and　25）。　If　we　assume　that　pain　exists　for　the　purpose　of　stimulating　muscular　reactions；　we　may　well　inquire　what　part　of　the　nervous　are　is　the　site　of　the　sensation　of　painthe　nerve…endings；　the　trunk；　or　the　brain？　Does　pain　result　from　physical　contact　with　the　nerve…endings；　with　the　physical　act　of　transmitting　an　impression　along　the　nerve　trunk；　or　with　the　process　within　the　brain…cells　by　which　energy　is　released　to　cause　a　motor　act？

It　seems　most　probable　that　the　site　of　the　pain　is　in　the　brain…cells。　If　this　be　so；　then　what　is　the　physical　process　by　which　the　phenomena　of　pain　are　produced？　　The　one　hypothesis　that　can　be　tested　experimentally　is　that　pain　is　a　phenomenon　resulting　from　the　rapid　discharge　of　energy　in　the　brain…cells。　If　this　be　true；　then　if　every　pain　receptor　of　the　body　were　equally　stimulated　in　such　a　manner　that


｛illust。　caption　=　FIG。　　25。FEAR　AND　AGONY。　　〃Amid　this　dread　exuberance　of　woe　ran　naked　spirits　wing'd　with　horrid　fear。〃　Dante's　〃Inferno；〃　Canto　XXIV；　lines　89；　90。　　all　the　stimuli　reached　the　brain…cells　simultaneously；　the　cells　would　find　themselves　in　equilibrium　and　no　motor　act　would　be　performed。　But　if　all　the　pain　receptors　of　the　body　but　one　were　equally　stimulated；　and　this　one　stimu…lated　harder　than　the　rest；　then　the　latter　would　gain　possession　of　the　final　common　path；　the　sensation　of　pain　would　be　felt；　and　a　muscular　contraction　would　result。　It　is　well　known　that　when　a　greater　pain　is　thrown　into　competition　with　a　lesser　one；　the　lesser　is　completely　submerged。　In　this　manner　the　school…boy　initiates　the　novice　into　the　mystery　of　the　painless　plucking　of　hair。　　The　simultaneous；　but　severe　application　of　the　boot　to　the　blindfolded　victim　takes　complete　and　exclusive　possession　of　the　final　common　path　and　the　hair　is　painlessly　plucked　through　the　triumph　of　the　boot　stimulus　over　the　hair　stimulus　in　the　struggle　for　the　possession　of　the　final　common　path。　　Another　argument　in　favor　of　this　hypothesis　that　pain　is　an　accompaniment　of　the　release　of　energy　in　the　brain…　cells　is　found　in　the　fact　that　painless　stimuli　received　through　the　special　senses　may　completely　submerge　the　painful　stimuli　of　physical　injury；　for　although　the　stimuli　to　motor　action；　which　are　received　through　the　senses　of　sight；　hearing；　and　smell；　cause　even　more　powerful　motor　action　than　those　caused　by　physical　contact　stimuli；　yet　they　are　not　accompanied　by　pain。　Examples　of　this　triumph　of　stimulation　of　the　special　senses　over　contact　stimulation　are　frequently　seen　in　persons　obsessed　by　anger　or　fear；　and　to　a　less　degree　in　those　obsessed　by　sexual　emotion。　In　the　fury　of　battle　the　soldier　may　not　perceive　his　wound　until　the　emotional　excitation　is　wearing　away；　when　the　sensation　of　warm　blood　on　the　skin　may　first　attract　his　attention。　Religious　fanatics　are　said　to　feel　no　pain　when　they　subject　themselves　to　self…injury。　Now；　since　both　psychic　and　mechanical　stimuli　cause　motor　action　by　the　excitation　ofprecisely　the　same　mechanism　in　the　brain；　and　since　the　more　rapid　release　of　energy　from　psychic　stimuli　submerges　the　physical　stimuli　and　prevents　pain；　it　would　seem　that　pain　must　be　a　phenomenon　which　is　associated　with　the　process　of　releasing　energy　by　the　brain…cells。　Were　physical　injury　inflicted　in　a　quiescent　state　equal　to　that　inflicted　in　the　emotional　state；　great　pain　and　intense　muscular　action　would　be　experienced。　Now　the　emotions　are　as　purely　motor　excitants　as　is　pain。　The　dynamic　result　is　the　same　the　principal　difference　being　the　greater　suddenness　and　the　absolute　specificity　of　the　pain　stimuli　as　compared　with　the　more　complex　and　less　peremptory　stimuli　of　the　emotions。　A　further　evidence　that　pain　is　a　product　of　the　release　of　brain…cell　energy　is　the　probability　that　if　one　could　pierce　the　skin　at　many　points　on　a　limb　in　such　a　manner　that　antagonistic　points　only　were　equally　and　simultaneously　stimulated；　then　an　equilibrium　in　the　governing　brain…　cells　would　be　established　and　neither　pain　nor　motion　would　follow。　　An　absolute　test　of　this　assumption　cannot　be　made　but　it　is　supported　by　the　obtainable　evidence。　We　will　now　turn　to　a　new　viewpoint；　a　practical　as　well　as　a　fascinating　one；　which　can　best　be　illustrated　by　two　case　histories：　A　man；　seventy…eight　years　old；　whose　chief　complaint　was　obstinate　constipation；　was　admitted　to　the　medical　ward　of　the　Lakeside　Hospital　several　years　ago。　　The　abdomen　was　but　slightly　distended；　there　was　no　fever；　no　increased　leukocytosis；　no　muscular　rigidity；　and　but　slight　general　tenderness。　　He　claimed　to　have　lost　in　weight　and　strength　during　the　several　months　previous　to　his　admission。　A　tentative　diagnosis　of　malignant　tumor　of　the　large　intestine　was　made；　but　free　movements　weresecured　rather　easily；　and　we　abandoned　the　idea　of　an　exploratory　operation。　　The　patient　gradually　failed　and　died　without　a　definite　diagnosis　having　been　made　by　either　the　medical　or　the　surgical　service。　　At　autopsy　there　was　found　a　wide…spread　peritonitis　arising　from　a　perforated　appendix。　A　child；　several　years　old；　was　taken　ill　with　some　indefinite　disease。　A　number　of　the　ablest　medical　and　surgical　consultants　of　a　leading　medical　center　thoroughly　and　repeatedly　investigated　the　case。　Although　they　could　make　no　definite　diagnosis　they　all　agreed　that　the　trouble　surely　could　not　be　appendicitis　because　there　was　neither　muscular　rigidity　nor　tenderness。　The　autopsy　showed　a　gangrenous　appendix　and　general　peritonitis。　How　can　these　apparently　anomalous　cases　be　explained？　These　two　cases　are　illustrations　of　the　same　principle　that　underlies　the　freedom　from　pain　which　results　from　the　use　of　narcotics　and　anesthetics；　the　same　principle　that　explains　the　fact　that　cholecystitis　may　occur　in　the　aged　without　any　other　local　symptoms　than　the　presence　of　a　mass　and　perhaps　very　slight　tenderness；　and　that　accounts　in　general　for　the　lack　of　well…expressed　disease　phenomena　in　senility　and　in　infancy。　　The　reason　why　the　aged；　the　very　young；　and　the　subjects　of　general　paresis　show　but　few　symptoms　of　disease　is　that　in　senility　the　brain　is　deteriorated；　while　in　infancy　the　brain　is　so　undeveloped　that　the　mechanism　of　association　is　inactive；　hence　pain　and　tenderness；　which　are　among　the　oldest　of　the　associations；　are　wanting。　Senility　and　infancy　are　by　nature　normally　narcotized。　The　senile　are　passing　through　the　twilight　into　the　night；　while　infants　are　traversing　through　the　dawn　into　the　day。　Hence　it　is　that　the　diagnosis　of　injury　and　disease　in　the　extremes　oflife　is　beset　by　especial　difficulties；　since　the　entire　body　is　as　silent　as　are　the　brain；　the　pericardium；　the　mediastinum；　and　other　symptomless　areas。　　For　the　same　reason；　when　a　patient　who　is　seriously　ill　with　a　painful　disease　turns　upon　the　physician　a　glowing　eye　and　an　eager　face；　and　remarks　how　comfortable　he　feels；　then　the　end　is　near。　　This　is　a　brilliant　and　fateful　clinical　mirage。　When　one　reflects　on　the　vast　amount　of　evidence　as　to　the　origin　and　the　purpose　of　pain；　he　is　forced　to　conclude　that　pain　is　a　phenomenon　of　motor　stimulation；　and　that　its　principal　role　is　the　protection　of　the　individual　against　the　gross　and　the　microscopic　enemies　in　his　environment。　　The　benefits　of　pain　are　especially　manifested　in　the　urgent　muscular　actions　by　means　of　which　the　body　moves　away　from　physical　injury；　obstructions　of　the　hollow　viscera　are　overcome；　rest　is　compelled　in　the　acute　infections　the　infected　points　are　held　rigidly　quiet；　the　muscles　of　the　abdomen　are　fixed；　and　harmful　peristalsis　is　arrested　in　peritonitis；　while　there　is　absolutely　no　pain　in　the　diseases　or　injuries　which　affect　those　regions　of　the　bo