the origin and nature of emotions-第14部分

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　the　innumerable　threats　of　danger　which　are　suddenly　averted；　a　breach　of　the　conventions；　a　sudden　relief　from　acute　nervous　tension；　a　surpriseindeed；　any　excitant　to　which　there　is　no　predetermined　method　of　giving　a　physical　response　may　be　neutralized　by　the　excitation　of　the　mechanism　of　laughter。

In　the　same　way　the　laughter　excited　by　jokes　may　be　explained。　An　analysis　of　a　joke　shows　that　it　is　composed　of　two　parts　the　first；　in　which　is　presented　a　subject　that　acts　as　a　stimulus　to　action；　and　the　second；　in　which　the　story　turns　suddenly　so　that　the　stimulus　to　action　is　unexpectedly　withdrawn。　The　subject　matter　of　the　joke　affects　each　hearer　according　to　the　type　of　stimuli　that　commonly　excites　that　individual。　Hence　it　is　that　a　joke　may　convulse　one　person　while　it　bores　another；　and　so　there　are　jokes　of　the　classes；　bankers'　jokes；　politicians'　jokes；　the　jokes　of　professional　men；　of　the　plebeian；　of　the　artist；　etc。　If　the　joke　fails；　the　integration　products　of　the　excitation　may　be　used　in　physical　resentment　（Fig。　32）。

Another　type　of　laughter　is　that　associated　with　the　ticklish　points　of　certain　parts　of　the　body；　the　soles　of　the　feet　and　certain　parts　of　the　trunk　and　of　the　abdomen。　　The　excitation　of　the　ticklish　receptors；　like　pain；　compels　self…defensive　motor　acts。　This　response　is　of　phylogenetic　origin；　and　may　be　awakened　only　by　stimuli　which　are　too　light　to　be　painful。　　In　this　connection　it　is　of　interest　to　note　that　a　superficial；　insect…like　contact　with　the　skin　rarely　provokes　laughter；　and　that　the　tickling　of　the　nasal；　oral；　and　pulmonary　tracts　does　not　produce　laughter。　The　ticklish　points　that　cause　laughter　are　rather　deeply　placed；　and　a　certain　type　of　physical　contact　is　required　to　constitute　an　adequate　stimulus。　　That　is；　the　contact　must　arouse　a　phylogenetic　association　with　a　physical　struggle　or　with　physical　exertion。　In　the　foot；　the　adequate　stimuli　for　laughter　are　such　contacts　as　resemble　or　suggest　piercing　by　stones　or　rough　objects。。　The　intention　of　the　one　who　tickles　must　be　known；　if　his　intention　be　playful；　laughter　results；　whereas　if　injury　be　intended；　then　an　effort　toward　escape　or　defense　is　excited；　but　no　laughter。　If　deep　tickling　of　the　ribs　is　known　to　be　malicious；　it　will　excite　physical　resentment　and　not　laughter。　　Self…tickling　rarely　causes　laughter　for　the　reason　that　auto…tickling　can　cause　only　a　known　degree　of　stimulation；　so　that　there　results　no　excessive　integration　which　requires　relief　by　the　neutral　muscular　activity　of　laughter。　In　fact；　one　never　sees　purposeful　acts　and　laughter　associated。　According　to　its　severity；　an　isolated　stimulus　causes　either　an　action　or　laughter。　　The　ticklish　points　in　our　bodies　were　probably　developed　as　a　means　of　defense　against　serious　attacks　and　of　escape　from　injurious　contacts。

Anger；　fear；　and　grief　are　also　strong　excitants　and；　therefore；　are　stimuli　to　motor　activity。　　It　is　obvious　that　whatever　the　excitant　the　physico…chemical　action　of　the　brain　and　the　ductless　glands　cannot　be　reversedthe　effect　of　the　stimulus　cannot　be　recalled；　therefore　either　a　purposeful　muscular　act　or　a　neutralizing　act　must　be　performed　or　else　the　liberated　energy　must　smoulder　in　the　various　parts　of　the　body。

It　is　on　this　hypothesis　that　the　origin　and　the　purpose　of　laughter　and　crying　may　be　understood。　　Even　a　superficial　analysis　of　the　phenomena　of　both　laughter　and　crying　show　them　to　be　without　any　external　motor　purpose；　the　respiratory　mechanism　is　intermittently　stimulated　and　inhibited；　and　the　shoulder　and　arm　muscles；　indeed；　many　muscles　of　the　trunk　and　the　extremities　are；　as　far　as　any　external　design　is　concerned；　purposelessly　contracted　and　released　until　the　kinetic　energy　mobilized　by　excitation　is　utilized。　During　this　time　the　facial　expression　gives　the　index　to　the　mental　state。

Crying；　like　laughter；　is　always　preceded　by　a　stimulation　to　some　motor　action　which　may　or　may　not　be　performed　（Figs。　33　and　34）。　If　a　mother　is　anxiously　watching　the　course　of　a　serious　illness　of　her　child　and　if；　in　caring　for　it；　she　is　stimulated　to　the　utmost　to　perform　motor　acts；　she　will　continue　in　a　state　of　motor　tenseness　until　the　child　recovers　or　dies。　If　relief　is　sudden；　as　in　the　crisis　of　pneumonia；　and　the　mother　is　not　exhausted；　she　will　easily　laugh　if　tired；　she　may　cry。　If　death　occurs；　the　stimulus　to　motor　acts　is　suddenly　withdrawn　and　she　then　cries　aloud；　and　performs　many　motor　acts　as　a　result　of　the　intense　stimulation　to　motor　activity　which　is　no　longer　needed　in　the　physical　care　of　her　child。　With　this　clue　we　can　find　the　explanation　of　many　phenomena。　　We　can　understand　why　laughter　and　crying　are　so　frequently　interchangeable；　why　they　often　blend　and　why　either　gives　a　sense　of　relief；　we　can　understand　why　either　laughter　or　crying　can　come　only　when　the　issue　that　causes　the　integration　is　determined；　we　can　understand　the　extraordinary　tendency　to　laughter　that　discloses　the　unspoken　sentiments　of　love；　we　can　understand　the　tears　of　the　woman　when　she　receives　a　proposal　of　marriage　from　the　man　she　loves；　we　can　understand　why　any　averted　circumstance；　such　as　a　threatened　breach　of　the　conventions；　which　would　have　led　to　embarrassment　or　humiliation；　leads　to　a　tendency　to　laughter；　and　why　the　recital　of　heroic　deeds　by　association　leads　to　tears；　On　the　other　hand；　under　the　domination　of　acute　diseases；　of　acute　fear；　or　of　great　exhaustion；　there　is　usually　neither　laughter　nor　crying　because　the　nervous　system　is　under　the　control　of　a　dominating　influence　as　a　result　of　which　the　body　is　so　exhausted　that　the　excess　of　energy　which　alone　can　produce　laughing　or　crying　is　lacking。

A　remarkable　study　of　the　modification　of　laughter　and　crying　by　disease　is　found　in　that　most　interesting　of　diseasesexophthalmic　goiter。　In　this　disease　there　is　a　low　threshold　to　all　stimuli。　That　the　very　motor　mechanism　of　which　we　have　been　speaking　is　involved；　is　shown　by　an　enormous　increase　in　its　activity。　There　is　also　an　increase　in　the　size　of　certain　at　least　of　the　activating　glandsthe　thyroid　and　the　adrenals　are　enlarged　and　overactive　and　the　glycogen…producing　function　of　the　liver　is　stimulated。　The　most　striking　phenomenon　of　this　disease；　however；　is　the　remarkable　lowering　of　the　brain　thresholds　to　stimuli。　　In　other　words；　in　Graves'　disease　the　nervous　system　and　the　activating　glands　the　entire　motor　mechanismare　in　an　exalted　state　of　activity。

If　this　be　true；　then　these　patients　should　exhibit　behavior　precisely　contrary　to　that　of　those　suffering　from　acute　infection；　that　is；　they　should　be　constantly　clearing　their　systems　of　these　superabundant　energizing　materials　by　crying　or　laughing；　and　this　is　precisely　what　happensthe　flood…gates　of　tears　are　open　much　of　the　time　in　Graves'　diseasea　disease　of　the　emotions。

We　have　already　interpreted　pain　as　a　phenomenon　of　motor　activity。　When　pain　does　not　lead　to　muscular　activity　it　therefore　frequently　leads　to　crying　or　to　moaning；　just　as　tickling；　which　is　equally　an　incentive　to　motor　activity；　results　in　laughter　if　it　does　not　find　full　expression　in　action。

From　the　foregoing　we　infer　that　pain；　the　intense　motor　response　to　tickling；　and　emotional　excitation　are　all　primitive　biologic　reactions　for　the　good　of　the　individual；　and　that　all　have　their　origin　in　the　operation　of　the　great　laws　of　evolution。　If　to　this　inference　we　add　the　physiologic　dictum　that　the　nervous　system　always　acts　as　a　whole；　and　that　it　can　respond　to　but　one　stimulus　at　a　time；　we　can　easily　understand　that　while　diverse　causes　may　integrate　the　nervous　system　for　a　specific　action；　if　the　cause　be　suddenly　removed；　then　the　result　of　the　integration　of　the　nervous　system　may　be；　not　a　specific　action；　but　an　undesigned　muscular　action；　such　as　crying　or　laughter。　Hence　it　is　that　laughter　and　crying　may　be　evoked　by　diverse　exciting　causes。　　The　intensity　of　the　laughter　or　of　the　crying　depends　upon　the　intensity　of　the　stimulus　and　the　dynamic　state　of　the　individual。

The　linking　together　of　these　apparently　widely　separated　phenomena　by　the　simple　law　of　the　discharge　of　energy　by　association　perhaps　explains　the　association　of　an　abnormal　tendency　to　tears　with　an　abnormally　low　threshold　for　pain　（Fig。　36）。　In　the　neurasthenic；　tears　and　pain　are　produced　with　abnormal　facility。　　Hence　it　is　that；　if　a　patient　about　to　undergo　a　surgical　operation　is　in　a　state　of　fear　and　dread　before　the　operation；　the　threshold　to　all　stimuli　is　lowered；　and　this　lowered　threshold　will　continue　throughout　the　operation；　even　under　inhalation　anesthesia；　because　the　stimulus　produced　by　cutting　sensitive　tissue　is　transmitted　to　the　brain　just　as　readily　as　if　the　patient　were　not　anesthetized。　　In　like　manner；　the　brain　may　be　sensitized　by　the　administration　of　large　doses　of　thyroid　extract　prior　to　operation；　the　threshold　to　injury　in　such　a　case　continuing　to　be　low　to　traumatic　stimuli　even　under　anesthesia。　Under　the　sensitizing　influences　of　thyroid　extract　or　of　Graves'　disease　the　effect　of　an　injury；　of　an　operation；　or　of　emotional　excitation　is　heightened。　　The　extent　to　which　the　threshold　to　pain　or　to　any　other　excitant　is　affected　by　Graves'　disease　is　illustrated　by　the　almost　fatal　reaction　which　I　once　saw　result　from　the　mere　pricking　with　a　hypodermic　needle　of　a　patient　with　this　disease。　As　the　result　of　a　visit　from　a　friend；　the　pulse…rate　of　a　victim　of　this　disease　may　increase　twenty　beats　and　his　temperature　rise　markedly。　I　have　seen　the　mere　suggestion　of　an　operation　produce　collapse。　As　the　brain　is　thus　remarkably　sensitized　in　Graves'　disease；　we　find　that　in　these　patients　laughter；　crying；　emotional　disturbances；　and　surgical　shock　are　produced　with　remarkable　facility。

I　hope　that　even　this　admittedly　crude　and　imperfect　consideration　of　this　subject　will　suggest　the　possibility　of　establishing　a　practical　viewpoint　as　to　the　origin　and　purpose　of　pain；　of　tickling；　and　of　such　expressions　of　emotion　as　laughter　and　crying；　and　that　it　may　help　us　to　understand　their　significance　in　health　and　in　disease。



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