the origin and nature of emotions-第16节

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　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。



THE　RELATION　BETWEEN　THE　PHYSICAL　STATE　OF　THE　BRAIN…CELLS　AND　BRAIN　FUNCTIONSEXPERIMENTAL　AND　CLINICAL＇*＇

＇*＇　Address　before　The　American　Philosophical　Society；　April　18；　1913。


The　brain　in　all　animals　（including　man）　is　but　the　clearing…house　for　reactions　to　environment；　for　animals　are　essentially　motor　or　neuromotor　mechanisms；　composed　of　many　parts；　it　is　true；　but　integrated　by　the　nervous　system。　　Throughout　the　phylogenetic　history　of　the　race　the　stimuli　of　environment　have　driven　this　mechanism；　whose　seat　of　powerthe　batteryis　the　brain。

Since　all　normal　life　depends　upon　the　response　of　the　brain　to　the　daily　stimuli；　we　should　expect　in　health；　as　well　as　in　disease；　to　find　modifications　of　the　functions　and　the　physical　state　of　the　component　parts　of　this　central　battery　the　brain…cells。　Although　we　must　believe；　then；　that　every　reaction　to　stimuli；　however　slight；　produces　a　corresponding　change　in　the　brain…cells；　yet　there　are　certain　normal；　that　is；　non…diseased；　conditions　which　produce　especially　striking　changes。　The　cell　changes　due　to　the　emotions；　for　example；　are　so　similar；　and　in　extreme　conditions　approach　so　closely　to　the　changes　produced　by　disease；　that　it　is　impossible　to　say　where　the　normal　ceases　and　the　abnormal　begins。

In　view　of　the　similarity　of　brain…cell　changes　it　is　not　strange　that　in　the　clinic　as　well　as　in　daily　life；　we　are　confronted　constantly　by　outward　manifestations　which　are　so　nearly　identical　that　the　true　underlying　cause　of　the　condition　in　any　individual　case　is　too　often　overlooked　or　misunderstood。　In　our　laboratory　experiments　and　in　our　clinical　observations　we　have　found　that　exhaustion　produced　by　intense　emotion；　prolonged　physical　exertion；　insomnia；　intense　fear；　certain　toxemias；　hemorrhage；　and　the　condition　commonly　denominated　surgical　shock；　produce　similar　outward　manifestations　and　identical　brain…cell　changes。

It　is；　therefore；　the　purpose　of　this　paper　to　present　the　definite　results　of　laboratory　researches　which　show　certain　relations　between　alterations　in　brain　functions　and　physical　changes　in　the　brain…cells。

Fear。Our　experiments　have　shown　that　the　brain…cell　changes　due　to　fear　may　be　divided　into　two　stages：　　First；　that　of　hyperchromatism　stimulation；　second；　that　of　hypochromatismexhaustion　（Figs。　5　and　13）。　Hyperchromatism　was　shown　only　in　the　presence　of　the　activating　stimuli　or　within　a　very　short　time　after　they　had　been　received。　This　state　gradually　changed　until　the　period　of　maximum　exhaustion　was　reachedabout　six　hours　later。　　Then　a　process　of　reconstruction　began　and　continued　until　the　normal　state　was　again　reached。

Fatigue。Fatigue　from　overexertion　produced　in　the　brain…cells　like　changes　to　those　produced　by　fear；　these　changes　being　proportional　to　the　amount　of　exertion　（Fig。　4）。　In　the　extreme　stage　of　exhaustion　from　this　cause　we　found　that　the　total　quantity　of　Nissl　substance　was　enormously　reduced。　When　the　exertion　was　too　greatly　prolonged；　it　took　weeks　or　months　for　the　cells　to　be　restored　to　their　normal　condition。　We　have　proved；　therefore；　that　in　exhaustion　resulting　from　emotion　or　from　physical　work　a　certain　number　of　the　brain…cells　are　permanently　lost。　　This　is　the　probable　explanation　of　the　fact　that　an　athlete　or　a　race…horse　trained　to　the　point　of　highest　efficiency　can　reach　his　maximum　record　but　once　in　his　life。　Under　certain　conditions；　however；　it　is　possible　that；　though　some　chromatin　is　forever　lost；　the　remainder　may　be　so　remarkably　developed　that　for　a　time　at　least　it　will　compensate　for　that　which　is　gone。

Hemorrhage。The　loss　of　blood　from　any　cause；　if　sufficient　to　reduce　the　blood…pressure；　will　occasion　a　change　in　the　brain…cells；　provided　that　the　period　of　hypotension　lasts　for　more　than　five　minutes。　This　time　limit　is　a　safeguard　against　permanent　injury　from　the　temporary　hypotension　which　causes　one　to　faint。　If　the　hemorrhage　be　long　continued　and　the　blood…pressure　be　low；　there　will　be　a　permanent　loss　of　some　of　the　brain…cells。　This　explains　why　an　individu