the origin and nature of emotions-第26节

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s　aversion　to　food　and　frequently　there　is　vomiting。　　In　fever；　then；　we　have　diminished　intake　of　energy；　but　an　increased　output　of　energyhence　the　available　potential　energy　in　the　body　is　rapidly　consumed。　　This　may　be　an　adaptation　for　the　purpose　of　breaking　up　the　foreign　protein　molecules　composing　the　bacteria。　　Thus　the　body　may　be　purified　by　a　chemical　combustion　so　furious　that　frequently　the　host　itself　is　destroyed。　The　problems　of　immunity　are　not　considered　here。

As　to　the　mechanism　which　produces　fever；　we　postulate　that　it　is　the　same　mechanism　as　that　which　produces　muscular　activity。　Muscular　activity　is　produced　by　the　conversion　of　latent　energy　into　motion；　and　fever　is　produced　largely　in　the　muscles　by　the　conversion　of　latent　energy　into　heat。　　We　should；　therefore；　find　similar　changes　in　the　brain；　the　adrenals；　the　thyroid；　and　the　liver；　whatever　may　be　the　purpose　of　the　conversion　of　energy　whether　for　running；　for　fighting；　for　the　expression　of　emotion；　or　for　combating　infection。

We　shall　first　present　experimental　and　clinical　evidence　which　tends　to　show　what　part　is　played　by　the　brain　in　the　production　of　both　muscular　and　febrile　action；　and　later　we　shall　discuss　the　parts　played　by　the　adrenals；　the　thyroid；　and　the　liver。　　Histologic　Changes　in　the　Brain…cells　in　Relation　to　the　Maintenance　of　Consciousness　and　to　the　Production　of　the　Emotions；　Muscular　Activity；　and　Fever

We　have　studied　the　brain…cells　in　human　cases　of　fever；　and　in　animals　after　prolonged　insomnia；　after　the　injection　of　the　toxins　of　gonococci；　of　streptococci；　of　staphylococci；　and　of　colon；　tetanus；　diphtheria；　and　typhoid　bacilli；　and　after　the　injection　of　foreign　proteins；　of　indol　and　skatol；　of　leucin；　and　of　peptones。　　We　have　studied　the　brains　of　animals　which　had　been　activated　in　varying　degrees　up　to　the　point　of　complete　exhaustion　by　running；　by　fighting；　by　rage　and　fear；　by　physical　injury；　and　by　the　injection　of　strychnin　（Figs。　2；　4；　5；　and　37）。　We　have　studied　the　brains　of　salmon　at　the　mouth　of　the　Columbia　River　and　at　its　headwater　（Fig。　55）；　the　brains　of　electric　fish；　the　storage　batteries　of　which　had　been　partially　discharged；　and　of　those　the　batteries　of　which　had　been　completely　discharged；　the　brains　of　woodchucks　in　hibernation　and　after　fighting；　the　brains　of　humans　who　had　died　from　anemia　resulting　from　hemorrhage；　from　acidosis；　from　eclampsia；　from　cancer　and　from　other　chronic　diseases　（Figs。　40　to　43；　56；　74；　and　75）。　We　have　studied　also　the　brains　of　animals　after　the　excision　of　the　adrenals；　of　the　pancreas；　and　of　the　liver　（Figs。　57　and　60）。

In　every　instance　the　loss　of　vitalitythat　is；　the　loss　of　the　normal　power　to　convert　potential　into　kinetic　energy　was　accompanied　by　physical　changes　in　the　brain…cells　（Figs。　45　and　46）。　The　converse　was　also　true；　that　is；　the　brain…cells　of　animals　with　normal　vital　power　showed　no　histologic　changes。　The　changes　in　the　brain…cells　were　identical　whatever　the　cause。　The　crucial　question　then　becomes：　　Are　these　constant　changes　in　the　brain…cells　the　result　of　work　done　by　the　brain…cells　in　running；　in　fighting；　in　emotion；　in　fever？　　In　other　words；　does　the　brain　perform　a　definite　role　in　the　conversion　of　latent　energy　into　fever　or　into　muscular　action；　or　are　the　brain…cell　changes　caused　by　the　chemical　products　of　metabolism？　　Happily；　this　crucial　question　was　definitely　answered　by　the　following　experiment：　The　circulations　of　two　dogs　were　crossed　in　such　a　manner　that　the　circulation　of　the　head　of　one　dog　was　anastomosed　with　the　circulation　of　the　body　of　another　dog；　and　vice　versa。　　A　cord　encircled　the　neck　of　each　so　firmly　that　the　anastomosing　circulation　was　blocked　（Fig。　58）。　If　the　brain…cell　changes　were　due　to　metabolic　products；　then　when　the　body　of　dog　〃A〃　was　injured；　the　brain　of　dog　〃A〃　would　be　normal　and　the　brain　of　dog　〃B〃　would　show　changes。　Our　experiments　showed　brain…cell　changes　in　the　brain　of　the　dog　injured　and　no　changes　in　the　brain　of　the　uninjured　dog。

The　injection　of　adrenalin　causes　striking　brain…cell　changes：　first；　a　hyperchromatism；　then　a　chromatolysis。　　Now　if　adrenalin　caused　these　changes　merely　as　a　metabolic　phenomenon　and　not　as　a　〃work〃　phenomenon；　then　the　injection　of　adrenalin　into　the　carotid　artery　of　a　crossed　circulation　dog　would　cause　no　change　in　its　circulation　and　its　respiration；　since　the　brain　thus　injected　is　in　exclusive　vascular　connection　with　the　body　of　another　dog。　In　our　experiment　the　blood…pressures　of　both　dogs　were　recorded　on　a　drum　when　adrenalin　was　injected　into　the　common　carotid。　The　adrenalin　caused　a　rise　in　blood…pressure；　an　increase　in　the　force　of　cardiac　contraction；　increase　in　respiration；　and　a　characteristic　adrenalin　rise　in　the　blood…pressure　of　both　dogs。　The　rise　was　seen　first　in　the　dog　whose　brain　alone　received　adrenalin　and　about　a　minute　later　in　the　dog　whose　body　alone　received　adrenalin　（Fig。　59）。　Histologic　examinations　of　the　brains　of　both　dogs　showed　marked　hyperchromatism　in　the　brain　receiving　adrenalin；　while　the　brain　receiving　no　adrenalin　showed　no　change。　Here　is　a　clear…cut　observation　on　the　action　of　adrenalin　on　the　brain；　for　both　the　functional　and　the　histologic　tests　showed　that　adrenalin　causes　increased　brain　action。　The　significance　of　this　affinity　of　the　brain　for　adrenalin　begins　to　be　seen　when　I　call　attention　to　the　following　striking　facts：

1。　　Adrenalin　alone　causes　hyperchromatism　followed　by　chromatolysis；　and　in　overdosage　causes　the　destruction　of　some　brain…cells。

2。　　When　both　adrenal　glands　are　excised　and　no　other　factor　is　introduced；　the　Nissl　substance　progressively　disappears　from　the　brain…cells　until　death。　　This　far…reaching　point　will　be　taken　up　later　（Fig。　60）。

Here　our　purpose　is　to　discuss　the　cause　of　the　brain…cell　changes。　We　have　seen　that　in　crossed　brain　and　body　circulation　trauma　causes　changes　in　the　cells　of　the　brain　which　is　disconnected　from　the　traumatized　body　by　its　circulation；　but　which　is　connected　with　the　traumatized　body　by　the　nervous　system。　We　have　seen　that　adrenalin　causes　activation　of　the　body　connected　with　its　brain　by　the　nervous　system；　and　histologic　changes　in　the　brain　acted　on　directly　by　the　adrenalin；　but　we　found　no　notable　brain…cell　changes　in　the　other　brain　through　which　the　products　of　metabolism　have　circulated。

In　the　foregoing　we　find　direct　evidence　that　the　products　of　metabolism　are　not　the　principal　cause　of　the　brain…cell　changes。　We　shall　now　present　evidence　to　show　that　for　the　most　part　the　brain…cell　changes　are　〃work〃　changes。　　What　work？　　We　postulate　that　it　is　the　work　by　which　the　energy　stored　in　the　brain…cells　is　converted　into　electricity　or　some　other　form　of　transmissible　energy　which　then　activates　certain　glands　and　muscles；　thus　converting　latent　energy　into　beat　and　motion。　　It　has　chanced　that　certain　other　studies　have　given　an　analogous　and　convincing　proof　of　this　postulate。　In　the　electric　fish　a　part　of　the　muscular　mechanism　is　replaced　by　a　specialized　structure　for　storing　and　discharging　electricity。　We　found　〃work〃　changes　in　the　brain…cells　of　electric　fish　after　all　their　electricity　had　been　rapidly　discharged　（Fig。　61）。　We　found　further　that　electric　fish　could　not　discharge　their　electricity　when　under　anesthesia；　and　clinically　we　know　that　under　deep　morphin　narcosis；　and　under　anesthesia；　the　production　both　of　heat　and　of　muscular　action　is　hindered。　The　action　of　morphin　in　lessening　fever　production　is　probably　the　result　of　its　depressing　influence　on　the　brain…cells；　because　of　which　a　diminished　amount　of　their　potential　energy　is　converted　into　electricity　and　a　diminished　electric　discharge　from　the　brain　to　the　muscles　should　diminish　heat　production　proportionally。　We　found　by　experiment　that　under　deep　morphinization　brain…cell　changes　due　to　toxins　could　be　largely　prevented　（Fig。　62）；　in　human　patients　deep　morphinization　diminishes　the　production　of　muscular　action　and　of　fever　and　conserves　life　when　it　is　threatened　by　acute　infections。　　The　contribution　of　the　brain…cells　to　the　production　of　heat　is　either　the　result　of　the　direct　conversion　of　their　stored　energy　into　heat；　or　of　the　conversion　of　their　latent　energy　into　electricity　or　a　similar　force；　which　in　turn　causes　certain　glands　and　muscles　to　convert　latent　energy　into　heat。

A　further　support　to　the　postulate　that　the　brain…cells　contribute　to　the　production　of　fever　by　sending　impulses　to　the　muscles　is　found　in　the　effect　of　muscular　exertion；　or　of　other　forms　of　motor　stimulation；　in　the　presence　of　a　fever…producing　infection。　Under　such　circumstances　muscular　exertion　causes　additional　fever；　and　causes　also　added　but　identical　changes　in　the　brain…cells。　Thyroid　extract　and　iodin　have　the　same　effect　as　muscular　exertion　and　infection　in　the　production　of　fever　and　the　production　of　brain…cell　changes。　All　this　evidence　is　a　strong　argument　in　favor　of　the　theory　that　certain　constituents　of　the　brain…cells　are　consumed　in　the　work　performed　by　the　brain　in　the　production　of　fever。

That　the　stimulation　of　the　brain…cells　without　gross　activity　of　the　skele