the origin and nature of emotions-第2部分

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n　of　brain　tissue　for　histologic　study。　　In　each　instance；　morphologic　changes　in　the　cells　of　all　parts　of　the　brain　were　found；　but　it　required　much　more　trauma　to　produce　brain…cell　changes　in　animals　whose　blood…pressure　was　kept　at　the　normal　level　than　in　the　animals　whose　blood…pressure　was　allowed　to　take　a　downward　course。　In　the　cortex　and　in　the　cerebellum；　the　changes　in　the　brain…cells　were　in　every　instance　more　marked　than　in　the　medulla。

There　is　also　strong　NEGATIVE　evidence　that　traumatic　impulses　are　not　excluded　by　ether　anesthesia　from　the　part　of　the　brain　that　is　apparently　asleep。　　This　evidence　is　as　follows：　If　the　factor　of　fear　be　excluded；　and　if　in　addition　the　traumatic　impulses　be　prevented　from　reaching　the　brain　by　cocain＇*＇　blocking；　then；　despite　the　intensity　or　the　duration　of　the　trauma　within　the　zone　so　blocked；　there　follows　no　exhaustion　after　the　effect　of　the　anesthetic　disappears；　and　no　morphologic　changes　are　noted　in　the　brain…cells。


＇*＇　Since　the　presentation　of　this　paper；　novocain　has　been　substituted　for　cocain　in　operations　under　anoci…association。


Still　further　negative　evidence　that　inhalation　anesthesia　offers　little　or　no　protection　to　the　brain…cells　against　trauma　is　derived　from　the　following　experiment：　　A　dog　whose　spinal　cord　had　been　divided　at　the　level　of　the　first　dorsal　segment；　and　which　had　then　been　kept　in　good　condition　for　two　months；　showed　a　recovery　of　the　spinal　reflexes；　such　as　the　scratch　reflex；　etc。　　Such　an　animal　is　known　as　a　〃spinal　dog。〃　　Now；　in　this　animal；　the　abdomen　and　hind　extremities　had　no　direct　nerve　connection　with　the　brain。　In　this　dog；　continuous　severe　trauma　of　the　abdominal　viscera　and　of　the　hind　extremities　lasting　for　four　　hours　was　accompanied　by　but　slight　change　in　either　the　circulation　or　in　the　respiration；　and　by　no　microscopic　alteration　of　the　brain…cells　（Fig。　1）。　Judging　from　a　large　number　of　experiments　on　NORMAL　dogs　under　ether；　such　an　amount　of　trauma　would　have　caused　not　only　complete　physiologic　exhaustion　of　the　brain；　but　also　morphologic　alterations　of　all　of　the　brain…cells　and　the　physical　destruction　of　many　（Fig。　2）。　We　must；　therefore；　conclude　that；　although　ether　anesthesia　produces　unconsciousness；　it　APPARENTLY　PROTECTS　NONE　OF　THE　BRAIN…CELLS　against　exhaustion　from　the　trauma　of　surgical　operations；　ether　is；　so　to　speak；　but　a　veneer。　　Under　nitrous　oxid　anesthesia　there　is　approximately　only　one…fourth　as　much　exhaustion　as　is　produced　by　equal　trauma　under　ether　（Fig。　3）。　We　must　conclude；　therefore；　either　that　nitrous　oxid　protects　the　brain…cells　against　trauma　or　that　ether　predisposes　the　brain…cells　to　exhaustion　as　a　result　of　trauma。　With　these　premises　let　us　now　inquire　into　the　cause　of　this　exhaustion　of　the　brain…cells。


The　Cause　of　the　Exhaustion　of　the　Brain…cells　as　a　Result　of　Trauma　of　Various　Parts　of　the　Body　under　Inhalation　Anesthesia


Numerous　experiments　on　animals　to　determine　the　effect　of　ether　anesthesia　_per　se_；　_i。　　e_。；　ether　anesthesia　without　trauma；　showed　that；　although　certain　changes　were　produced；　these　included　neither　the　physiologic　exhaustion　nor　the　alterations　in　the　brain…cells　which　are　characteristic　of　the　effects　of　trauma。　On　turning　to　the　study　of　trauma；　we　at　once　found　in　the　behavior　of　individuals　as　a　whole　under　deep　and　under　light　anesthesia　the　clue　to　the　cause　of　the　discharge　of　energy；　of　the　consequent　physiologic　exhaustion；　and　of　the　morphologic　changes　in　the　brain…cells。

If；　in　the　course　of　abdominal　operations；　rough　manipulations　of　the　parietal　peritoneum　be　made；　there　will　be　frequently　observed　a　marked　increase　in　the　respiratory　rate　and　an　increase　in　the　expiratory　force　which　may　be　marked　by　the　production　of　an　audible　expiratory　groan。　　Under　light　ether　anesthesia；　severe　manipulations　of　the　peritoneum　often　cause　such　vigorous　contractions　of　the　abdominal　muscles　that　the　operator　is　greatly　hindered　in　his　work。

Among　the　unconscious　responses　to　trauma　under　ether　anesthesia　are　purposeless　moving；　the　withdrawal　of　the　injured　part；　and；　if　the　anesthesia　be　sufficiently　light　and　the　trauma　sufficiently　strong；　there　may　be　an　effort　toward　escape　from　the　injury。　In　injury　under　ether　anesthesia　every　grade　of　response　may　be　seen；　from　the　slightest　change　in　the　respiration　or　in　the　blood…pressure　to　a　vigorous　defensive　struggle。　　As　to　the　purpose　of　these　subconscious　movements　in　response　to　injury；　there　can　be　no　doubt　THEY　ARE　EFFORTS　TO　ESCAPE　FROM　THE　INJURY。

Picture　what　would　be　the　result　of　a　formidable　abdominal　operation　extending　over　a　period　of　half　an　hour　or　more　on　an　unanesthetized　human　patient；　during　which　extensive　adhesions　had　been　broken　up；　or　a　large　tumor　dislodged　from　its　bed！　　In　such　a　case；　would　not　the　nervous　system　discharge　its　energy　to　the　utmost　in　efforts　to　escape　from　the　injury；　and　would　not　the　patient　suffer　complete　exhaustion？　　If　the　traumata　under　inhalation　anesthesia　are　sufficiently　strong　and　are　repeated　in　sufficient　numbers；　the　brain…cells　are　finally　deprived　of　their　dischargeable　nervous　energy　and　become　exhausted　just　as　exhaustion　follows　such　strenuous　and　prolonged　muscular　exertion　as　is　seen　in　endurance　tests。　Whether　the　energy　of　the　brain　be　discharged　by　injury　under　anesthesia　or　by　ordinary　muscular　exertion；　identical　morphologic　changes　are　seen　in　the　nerve…cells。　In　shock　from　injury　（Fig。　2）；　in　exhaustion　from　overwork　（Hodge　and　Dolley）　（Fig。　4）；　and　in　exhaustion　from　pure　fear　（Fig。　5）；　the　resultant　general　functional　weakness　is　similar　in　each　case　a　certain　length　of　time　is　required　to　effect　recovery；　and　in　each　there　are　morphologic　changes　in　the　brain…cells。　It　is　quite　clear　that　in　each　of　these　cases　the　altered　function　and　form　of　the　brain…cells　are　due　to　an　_*excessive　discharge　of　nervous　energy_。　　This　brings　us　to　the　next　question：　What　determines　the　discharge　of　energy　as　a　result　of　trauma　with　or　without　inhalation　anesthesia？


The　Cause　of　the　Discharge　of　Nervous　Energy　as　a　Result　of　Trauma　under　Inhalation　Anesthesia　and　under　Normal　Conditions


I　looked　into　this　problem　from　many　viewpoints　and　there　seemed　to　be　no　solution　until　it　occurred　to　me　to　seek　the　explanation　in　certain　of　the　postulates　which　make　up　the　doctrine　of　evolution。　I　realize　fully　the　difficulty　and　the　danger　in　attempting　to　reach　the　generalization　which　I　shall　make　later　and　in　the　hypothesis　I　shall　propose；　for　there　is；　of　course；　no　direct　final　proof　of　the　truth　of　even　the　doctrine　of　evolution。　It　is　idle　to　consider　any　experimental　research　into　the　cause　of　phenomena　that　have　developed　by　natural　selection　during　millions　of　years。　　Nature　herself　has　made　the　experiments　on　a　world…wide　scale　and　the　data　are　before　us　for　interpretation。　Darwin　could　do　no　more　than　to　collect　all　available　facts　and　then　to　frame　the　hypothesis　by　which　the　facts　were　best　harmonized。　Sherrington；　that　masterly　physiologist；　in　his　volume　entitled　〃The　Integrative　Action　of　the　Nervous　System；〃　shows　clearly　how　the　central　nervous　system　was　built　up　in　the　process　of　evolution。　Sherrington　has　made　free　use　of　Darwin's　doctrine　in　explaining　physiologic　functions；　just　as　anatomists　have　extensively　utilized　it　in　the　explanation　of　the　genesis　of　anatomic　forms。　I　shall　assume；　therefore；　that　the　discharge　of　nervous　energy　is　accomplished　by　the　application　of　the　laws　of　inheritance　and　association；　and　I　conclude　that　this　hypothesis　will　explain　many　clinical　phenomena。　I　shall　now　present　such　evidence　in　favor　of　this　hypothesis　as　time　and　my　limitations　will　admit；　after　which　I　shall　point　out　certain　clinical　facts　that　may　be　explained　by　this　hypothesis。

According　to　the　doctrine　of　evolution；　every　function　owes　its　origin　to　natural　selection　in　the　struggle　for　existence。　In　the　lower　and　simpler　forms　of　animal　life；　indeed；　in　our　human　progenitors　as　well；　existence　depended　principally　upon　the　success　with　which　three　great　purposes　were　achieved：　（1）　Self…defense　against　or　escape　from　enemies；　（2）　the　acquisition　of　food；　and　（3）　procreation；　and　these　were　virtually　the　only　purposes　for　which　nervous　energy　was　discharged。　　In　its　last　analysis；　in　a　biologic　sense；　this　statement　holds　true　of　man　today。　Disregarding　for　the　present　the　expenditure　of　energy　for　procuring　food　and　for　procreation；　let　us　consider　the　discharge　of　energy　for　self…preservation。　The　mechanisms　for　self…defense　which　we　now　possess　were　developed　in　the　course　of　vast　periods　of　time　through　innumerable　intermediary　stages　from　those　possessed　by　the　lowest　forms　of　life。　　One　would　suppose；　therefore；　that　we　must　now　be　in　possession　of　mechanisms　which　still　discharge　energy　on　adequate　stimulation；　but　which　are　not　suited　to　our　present　needs。　We　shall　point　out　some　examples　of　such　unnecessary　mechanisms。　As　Sherrington　has　stated；　our　skin；　in　which　are　implanted　many　receptors　for　receiving　specific　stimuli　which　are　transmitted　to　the　brain；　is　interposed　between　ourselves　and　the　environment　in　which　we　are　immersed。　　When　these　stimuli　reach　the　brain；　there　is　a　specific　response；　principally　in　the　form　of　muscular　action。　　Now；　each　receptor　can　be　adequately　stimulated　only　by　the　particular　factor　or　factors　in　the　environment　which　created　the　necessity　for　the　existence　of　that　receptor。　Thus　there　have　arisen　receptors　for　touch；　for　temperature；　for　pain；　etc。　　The　receptors　for　pain　have　been　designated　_nociceptors_　（nocuous　or　harmful）　by　Sherrington。

On　the　basis　of　natural　selection；　nociceptors　could　have　developed　in　only　those　regions　of　the　body　which　have　been　exposed　to　injury　during　long　periods　of　time。　　On　this　ground　the　finger；　because　it　is　exposed；　should　have　many　nociceptors；　while　the　brain；　though　the　most　important　organ　of　the　body；　should　have　no　nociceptors　because；　during　a　vast　period　of　time；　it　has　been　protected　by　a　skull。　Realizing　that　this　point　is　a　crucial　one；　Dr。　Sloan　and　I　made　a　series　of　careful　experiments。　　The　cerebral　hemispheres　of　dogs　were　exposed　by　removing　the　skull　and