From　the　reasons　above　assigned；　namely；　the　fleeting　nature　of　some　expressions　（the　changes　in　the　features　being　often　extremely　slight）；　our　sympathy　being　easily　aroused　when　we　behold　any　strong　emotion；　and　our　attention　thus　distracted；　our　imagination　deceiving　us；　from　knowing　in　a　vague　manner　what　to　expect；　though　certainly　few　of　us　know　what　the　exact　changes　in　the　countenance　are；　and　lastly；　even　our　long　familiarity　with　the　subject；from　all　these　causes　combined；　the　observation　of　Expression　is　by　no　means　easy；　as　many　persons；　whom　I　have　asked　to　observe　certain　points；　have　soon　discovered。　Hence　it　is　difficult　to　determine；　with　certainty；　what　are　the　movements　of　the　features　and　of　the　body；　which　commonly　characterize　certain　states　of　the　mind。　Nevertheless；　some　of　the　doubts　and　difficulties　have；　as　I　hope；　been　cleared　away　by　the　observation　of　infants；　of　the　insane；of　the　different　races　of　man；of　works　of　art；　and　lastly；　of　the　facial　muscles　under　the　action　of　galvanism；　as　effected　by　Dr。　Duchenne。
  But　there　remains　the　much　greater　difficulty　of　understanding　the　cause　or　origin　of　the　several　expressions；　and　of　judging　whether　any　theoretical　explanation　is　trustworthy。　　Besides；　judging　as　well　as　we　can　by　our　reason；　without　the　aid　of　any　rules；　which　of　two　or　more　explanations　is　the　most　satisfactory；　or　are　quite　unsatisfactory；　I　see　only　one　way　of　testing　our　conclusions。　This　is　to　observe　whether　the　same　principle　by　which　one　expression　can；　as　it　appears；　be　explained；　is　applicable　in　other　allied　cases；　and　especially；　whether　the　same　general　principles　can　be　applied　with　satisfactory　results；　both　to　man　and　the　lower　animals。　This　latter　method；　I　am　inclined　to　think；　is　the　most　serviceable　of　all。　The　difficulty　of　judging　of　the　truth　of　any　theoretical　explanation；　and　of　testing　it　by　some　distinct　line　of　investigation；　is　the　great　drawback　to　that　interest　which　the　study　seems　well　fitted　to　excite。
  Finally；　with　respect　to　my　own　observations；　I　may　state　that　they　were　commenced　in　the　year　1838；　and　from　that　time　to　the　present　day；　I　have　occasionally　attended　to　the　subject。　　At　the　above　date；　I　was　already　inclined　to　believe　in　the　principle　of　evolution；　or　of　the　derivation　of　species　from　other　and　lower　forms。　Consequently；　when　I　read　Sir　C。　Bell's　great　work；　his　view；　that　man　had　been　created　with　certain　muscles　specially　adapted　for　the　expression　of　his　feelings；　struck　me　as　unsatisfactory。　It　seemed　probable　that　the　habit　of　expressing　our　feelings　by　certain　movements；　though　now　rendered　innate；　had　been　in　some　manner　gradually　acquired。　　But　to　discover　how　such　habits　had　been　acquired　was　perplexing　in　no　small　degree。　The　whole　subject　had　to　be　viewed　under　a　new　aspect；　and　each　expression　demanded　a　rational　explanation。　This　belief　led　me　to　attempt　the　present　work；　however　imperfectly　it　may　have　been　executed。
  I　will　now　give　the　names　of　the　gentlemen　to　whom；　as　I　have　said；　I　am　deeply　indebted　for　information　in　regard　to　the　expressions　exhibited　by　various　races　of　man；　and　I　will　specify　some　of　the　circumstances　under　which　the　observations　were　in　each　case　made。　　Owing　to　the　great　kindness　and　powerful　influence　of　Mr。　Wilson；　of　Hayes　Place；　Kent；　I　have　received　from　Australia　no　less　than　thirteen　sets　of　answers　to　my　queries。　This　has　been　particularly　fortunate；　as　the　Australian　aborigines　rank　amongst　the　most　distinct　of　all　the　races　of　man。　It　will　be　seen　that　the　observations　have　been　chiefly　made　in　the　south；　in　the　outlying　parts　of　the　colony　of　Victoria；　but　some　excellent　answers　have　been　received　from　the　north。
  Mr。　Dyson　Lacy　has　given　me　in　detail　some　valuable　observations；　made　several　hundred　miles　in　the　interior　of　Queensland。　To　Mr。　R。　Brough　Smyth；　of　Melbourne；　I　am　much　indebted　for　observations　made　by　himself；　and　for　sending　me　several　of　the　following　letters；　namely：From　the　Rev。　Mr。　Hagenauer；　of　Lake　Wellington；　a　missionary　in　Gippsland；　Victoria；　who　has　had　much　experience　with　the　natives。　　From　Mr。　Samuel　Wilson；　a　landowner；　residing　at　Langerenong；　Wimmera；　Victoria。　　From　the　Rev。　George　Taplin；　superintendent　of　the　native　Industrial　Settlement　at　Port　Macleay。　　From　Mr。　Archibald　G。　Lang；　of　Coranderik；　Victoria；　a　teacher　at　a　school　where　aborigines；　old　and　young；　are　collected　from　all　parts　of　the　colony。　From　Mr。　H。　B。　Lane；　of　Belfast；　Victoria；　a　police　magistrate　and　warden；　whose　observations；　as　I　am　assured；　are　highly　trustworthy。　From　Mr。　Templeton　Bunnett；　of　Echuca；　whose　station　is　on　the　borders　of　the　colony　of　Victoria；　and　who　has　thus　been　able　to　observe　many　aborigines　who　have　had　little　intercourse　with　white　men。　He　compared　his　observations　with　those　made　by　two　other　gentlemen　long　resident　in　the　neighbourhood。　　Also　from　Mr。　J。　Bulmer；　a　missionary　in　a　remote　part　of　Gippsland；　Victoria。
  I　am　also　indebted　to　the　distinguished　botanist；　Dr。　Ferdinand　Muller；　of　Victoria；　for　some　observations　made　by　himself；　and　for　sending　me　others　made　by　Mrs。　Green；　as　well　as　for　some　of　the　foregoing　letters。
  In　regard　to　the　Maoris　of　New　Zealand；　the　Rev。　J。　W。　Stack　has　answered　only　a　few　of　my　queries；　but　the　answers　have　been　remarkably　full；　clear；　and　distinct；　with　the　circumstances　recorded　under　which　the　observations　were　made。
  The　Rajah　Brooke　has　given　me　some　information　with　respect　to　the　Dyaks　of　Borneo。
  Respecting　the　Malays；　I　have　been　highly　successful；　for　Mr。　F。　Geach　（to　whom　I　was　introduced　by　Mr。　Wallace）；　during　his　residence　as　a　mining　engineer　in　the　interior　of　Malacca；　observed　many　natives；　who　had　never　before　associated　with　white　men。　　He　wrote　me　two　long　letters　with　admirable　and　detailed　observations　on　their　expression。　He　likewise　observed　the　Chinese　immigrants　in　the　Malay　archipelago。
  The　well…known　naturalist；　H。　M。　Consul；　Mr。　Swinhoe；　also　observed　for　me　the　Chinese　in　their　native　country；　and　he　made　inquiries　from　others　whom　he　could　trust。
  In　India　Mr。　H。　Erskine；　whilst　residing　in　his　official　capacity　in　the　Admednugur　District　in　the　Bombay　Presidency；　attended　to　the　expression　of　the　inhabitants；　but　found　much　difficulty　in　arriving　at　any　safe　conclusions；　owing　to　their　habitual　concealment　of　all　emotions　in　the　presence　of　Europeans。　　He　also　obtained　information　for　me　from　Mr。　West；　the　Judge　in　Canara；　and　he　consulted　some　intelligent　native　gentlemen　on　certain　points。　　In　Calcutta　Mr。　J。　Scott；　curator　of　the　Botanic　Gardens；　carefully　observed　the　various　tribes　of　men　therein　employed　during　a　considerable　period；　and　no　one　has　sent　me　such　full　and　valuable　details。　The　habit　of　accurate　observation；　gained　by　his　botanical　studies；　has　been　brought　to　bear　on　our　present　subject。　For　Ceylon　I　am　much　indebted　to　the　Rev。　S。　O。　Glenie　for　answers　to　some　of　my　queries。
  Turning　to　Africa；　I　have　been　unfortunate　with　respect　to　the　negroes；　though　Mr。　Winwood　Reade　aided　me　as　far　as　lay　in　his　power。　It　would　have　been　comparatively　easy　to　have　obtained　information　in　regard　to　the　negro　slaves　in　America；　but　as　they　have　long　associated　with　white　men；　such　observations　would　have　possessed　little　value。　　In　the　southern　parts　of　the　continent　Mrs。　Barber　observed　the　Kafirs　and　Fingoes；　and　sent　me　many　distinct　answers。　Mr。　J。　P。　Mansel　Weale　also　made　some　observations　on　the　natives；　and　procured　for　me　a　curious　document；　namely；　the　opinion；　written　in　English；　of　Christian　Gaika；　brother　of　the　Chief　Sandilli；　on　the　expressions　of　his　fellow…countrymen。　In　the　northern　regions　of　Africa　Captain　Speedy；　who　long　resided　with　the　Abyssinians；　answered　my　queries　partly　from　memory　and　partly　from　observations　made　on　the　son　of　King　Theodore；　who　was　then　under　his　charge。　Professor　and　Mrs。　Asa　Gray　attended　to　some　points　in　the　expressions　of　the　natives；　as　observed　by　them　whilst　ascending　the　Nile。
  On　the　great　American　continent　Mr。　Bridges；　a　catechist　residing　with　the　Fuegians；　answered　some　few　questions　about　their　expression；　addressed　to　him　many　years　ago。　In　the　northern　half　of　the　continent　Dr。　Rothrock　attended　to　the　expressions　of　the　wild　Atnah　and　Espyox　tribes　on　the　Nasse　River；　in　North…Western　America。　　Mr。　Washington　Matthews　Assistant…Surgeon　in　the　United　States　Army；　also　observed　with　special　care　（after　having　seen　my　queries；　as　printed　in　the　‘Smithsonian　Report'）　some　of　the　wildest　tribes　in　the　Western　parts　of　the　United　States；　namely；　the　Tetons；　Grosventres；　Mandans；　and　Assinaboines；　and　his　answers　have　proved　of　the　highest　value。
  Lastly；　besides　these　special　sources　of　information；　I　have　collected　some　few　facts　incidentally　given　in　books　of　travels。
  As　I　shall　often　have　to　refer；　more　especially　in　the　latter　part　of　this　volume；　to　the　muscles　of　the　human　face；　I　have　had　a　diagram　（fig。　1）　copied　and　reduced　from　Sir　C。　Bell's　work；　and　two　others；　with　more　accurate　details　（figs。　2　and　3）；　from　Herde's　well…known　‘Handbuch　der　Systematischen　Anatomie　des　Menschen。'　　The　same　letters　refer　to　the　same　muscles　in　all　three　figures；　but　the　names　are　given