the origin and nature of emotions-第23章

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e　us　a　definite　physical　basis　for　explaining　the　cost　to　the　body　mechanism　of　maintaining　the　conscious　state。　We　have　stated　that　the　brain…cell　changes　produced　by　prolonged　consciousness　are　identical　with　those　produced　by　physical　exertion　and　by　emotional　strain。　　Rest；　then；　and　especially　sleep；　is　needed　to　restore　the　physical　state　of　the　brain…cells　which　have　been　impaired；　and　as　the　brain…cells　constitute　the　central　battery　of　the　body　mechanism；　their　restoration　is　essential　for　the　maintenance　of　normal　vitality。

In　ordinary　parlance；　by　consciousness　we　mean　the　activity　of　that　part　of　the　brain　in　which　associative　memory　resides；　but　while　associative　memory　is　suspended　the　activities　of　the　brain　as　a　whole　are　by　no　means　suspended；　the　respiratory　and　circulatory　centers　are　active；　as　are　those　centers　which　maintain　muscular　tone。　This　is　shown　by　the　muscular　response　to　external　stimuli　made　by　the　normal　person　in　sleep；　by　the　occasional　activation　of　motor　patterns　which　may　break　through　into　consciousness　causing　dreams；　and　finally　by　the　responses　of　the　motor　mechanism　made　to　the　injuring　stimuli　of　an　operation　on　a　patient　under　inhalation　anesthesia　only。

Direct　proof　of　the　mechanistic　action　of　many　of　life's　phenomena　is　lacking；　but　the　proof　is　definite　and　final　of　the　part　that　the　brain…cells　play　in　maintaining　consciousness；　of　the　fact　that　the　degree　of　consciousness　and　mental　efficiency　depends　upon　the　physical　state　of　the　brain…cells；　and　finally　that　efficiency　may　be　restored　by　sleep；　provided　that　exhaustion　of　the　cells　has　not　progressed　too　far。　In　this　greatest　phenomenon　of　life；　then；　the　mechanistic　theory　is　in　harmony　with　the　facts。

Perhaps　no　more　convincing　proof　of　our　thesis　that　the　body　is　a　mechanism　developed　and　adapted　to　its　purposes　by　environment　can　be　secured　than　by　a　study　of　that　most　constant　manifestation　of　consciousnesspain。

Like　the　other　phenomena　of　life；　pain　was　undoubtedly　evolved　for　a　particular　purposesurely　for　the　good　of　the　individual。　Like　fear　and　worry；　it　frequently　is　injurious。　　What　then　may　be　its　purpose？

We　postulate　that　pain　is　a　result　of　contact　ceptor　stimulation　for　the　purpose　of　securing　protective　muscular　activity。　This　postulate　applies　to　all　kinds　of　pain；　whatever　their　cause　whether　physical　injury；　pyogenic　infection；　the　obstruction　of　hollow　viscera；　childbirth；　etc。

All　forms　of　pain　are　associated　with　muscular　action；　and　as　in　every　other　stimulation　of　the　ceptors；　each　kind　of　pain　is　specific　to　the　causative　stimuli。　　The　child　puts　his　hand　in　the　fire；　physical　injury　pain　results；　and　the　appropriate　muscular　response　is　elicited。　　If　pressure　is　prolonged　on　some　parts　of　the　body；　anemia　of　the　parts　may　result；　with　a　corresponding　discomfort　or　pain；　requiring　muscular　action　for　relief。　When　the　rays　of　the　sun　strike　directly　upon　the　retina；　light　pain　causes　an　immediate　protective　action；　so　too　in　the　evacuation　of　the　intestine　and　the　urinary　bladder　as　normal　acts；　and　in　overcoming　obstruction　of　these　tracts；　discomfort　or　pain　compel　the　required　muscular　actions。　　This　view　of　pain　as　a　stimulation　to　motor　action　explains　why　only　certain　types　of　infection　are　associated　with　pain；　namely；　those　types　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。　As　a　further　remarkable　proof　of　the　marvelous　adaptation　of　the　body　mechanism　to　meet　varying　environmental　conditions；　we　find　that　just　as　nociceptors　have　been　implanted　in　only　those　parts　of　the　body　which　have　been　subject　to　nocuous　contacts；　so　a　type　of　infection　which　causes　muscular　action　in　one　part　of　the　body　may　cause　none　when　it　attacks　another。

This　postulate　gives　us　the　key　to　the　pain…muscular　phenomena　of　peritonitis；　pleurisy；　cystitis；　cholecystitis；　etc。；　as　well　as　to　the　pain…muscular　phenomena　in　obstructions　of　the　hollow　viscera。　If　pain　is　a　part　of　a　muscular　response　and　occurs　only　as　a　result　of　contact　ceptor　stimulation　by　physical　injury；　infection；　anemia；　or　obstruction；　we　may　well　inquire　which　part　of　the　nerve　mechanism　is　the　site　of　the　phenomenon　of　pain。　Is　it　the　nerve…ending；　the　nerve…trunk；　or　the　brain？　　That　is；　is　pain　associated　with　the　physical　contact　with　the　nerve…ending；　or　with　the　physical　act　of　transmission　along　the　nerve…trunk；　or　with　the　change　of　brain…cell　substance　by　means　of　which　the　motor…producing　energy　is　released？

We　postulate　that　the　pain　is　associated　with　the　discharge　of　energy　from　the　brain…cells。　If　this　be　true；　then　if　every　nociceptor　in　the　body　were　equally　stimulated　in　such　a　manner　that　all　the　stimuli　should　reach　the　brain…cells　simultaneously；　then　the　cells　would　find　themselves　in　equilibrium　and　no　motor　act　would　be　performed。　But　if　all　the　pain　nerve　ceptors　but　one　were　equally　stimulated；　and　this　one　more　strongly　stimulated　than　the　rest；　then　this　one　would　gain　possession　of　the　final　common　pathwould　cause　a　muscular　action　and　the　sensation　of　pain。

It　is　well　known　that　when　a　greater　pain　or　stimulus　is　thrown　into　competition　with　a　lesser　one；　the　lesser　is　submerged。　Of　this　fact　the　school…boy　makes　use　when　he　initiates　the　novice　into　the　mystery　of　the　painless　pulling　of　hair。　The　simultaneous　but　severe　application　of　the　boot　to　the　blindfolded　victim　takes　complete　but　exclusive　possession　of　the　final　common　path　and　the　hair　is　painlessly　plucked　as　a　result　of　the　triumph　of　the　boot　stimulus　over　the　pull　on　the　hair　in　the　struggle　for　the　final　common　path。

Persons　who　have　survived　a　sudden；　complete　exposure　to　superheated　steam；　or　whose　bodies　have　been　enwrapped　in　flame；　testify　that　they　have　felt　no　pain。　　As　this　absence　of　pain　may　be　due　to　the　fact　that　the　emotion　of　fear　gained　the　final　common　path；　to　the　exclusion　of　all　other　stimuli；　we　are　trying　by　experimentation　to　discover　the　effects　of　simultaneous　painful　stimulation　of　all　parts　of　the　body。　The　data　already　in　hand；　and　the　experiments　now　in　progress；　in　which　anesthetized　animals　are　subjected　to　powerful　stimuli　applied　to　certain　parts　of　the　body　only；　or　simultaneously　to　all　parts　of　the　body；　lead　us　to　believe　that　in　the　former　case　the　brain…cells　become　stimulated　or　hyperchromatic；　while　in　the　latter　case　no　brain…cell　changes　occur。　　We　believe　that　our　experiments　will　prove　that　an　equal　and　simultaneous　stimulation　of　all　parts　of　the　body　leaves　the　brain…cells　in　a　state　of　equilibrium。　Our　theory　of　pain　will　then　be　well　sustained；　not　only　by　common　observation；　but　by　experimental　proof；　and　so　the　mechanistic　view　will　be　found　in　complete　harmony　with　another　important　reaction。

We　have　stated　that　when　a　number　of　contact　stimuli　act　simultaneously；　the　strongest　stimulus　will　gain　possession　of　the　final　common　path　the　path　of　action。　　When；　however；　stimuli　of　the　distance　ceptors　compete　with　stimuli　of　the　contact　ceptors；　the　contact…ceptor　stimuli　often　secure　the　common　path；　not　because　they　are　stronger　or　more　important；　but　because　they　are　immediate　and　urgent。　In　many　instances；　however；　the　distance…ceptor　stimuli　are　strong；　have　the　advantage　of　a　lowered　threshold；　and　therefore　compete　successfully　with　the　immediate　and　present　stimuli　of　the　contact　ceptors。　　In　such　cases　we　have　the　interesting　phenomenon　of　physical　injury　without　resultant　pain　or　muscular　response。　The　distance…ceptor　stimuli　which　may　thus　triumph　over　even　powerful　contact…ceptor　stimuli　are　those　causing　strong　emotionsas　great　anger　in　fighting；　great　fear　in　a　battle；　intense　sexual　excitement。　Dr。　Livingstone　has　testified　to　his　complete　unconsciousness　to　pain　during　his　struggle　with　a　lion；　although　he　was　torn　by　teeth　and　claws；　his　fear　overcame　all　other　impressions。　By　frequently　repeated　stimulation　the　Dervish　secures　a　low　threshold　to　the　emotions　caused　by　the　thought　of　God　or　the　devil；　and　his　emotional　excitement　is　increased　by　the　presence　of　others　under　the　same　stimulation；　emotion；　therefore；　secures　the　final　common　path　and　he　is　uncons