gures；　but　the　names　are　given　of　only　the　more　important　ones　to　which　I　shall　have　to　allude。　The　facial　muscles　blend　much　together；　and；　as　I　am　informed；　hardly　appear　on　a　dissected　face　so　distinct　as　they　are　here　represented。　Some　writers　consider　that　these　muscles　consist　of　nineteen　pairs；　with　one　unpaired；＇20＇　but　others　make　the　number　much　larger；　amounting　even　to　fifty…five；　according　to　Moreau。　　They　are；　as　is　admitted　by　everyone　who　has　written　on　the　subject；　very　variable　in　structure；　and　Moreau　remarks　that　they　are　hardly　alike　in　half…a…dozen　subjects。＇21＇　They　are　also　variable　in　function。　Thus　the　power　of　uncovering　the　canine　tooth　on　one　side　differs　much　in　different　persons。　　The　power　of　raising　the　wings　of　the　nostrils　is　also；　according　to　Dr。　Piderit；＇22＇　variable　in　a　remarkable　degree；　and　other　such　cases　could　be　given。
  ＇20＇　Mr。　Partridge　in　Todd's　‘Cyclopaedia　of　Anatomy　and　Physiology；'　vol。　　ii。　　p。　　227。
  ＇21＇　‘La　Physionomie；'　par　G。　Lavater；　tom。　　iv。　　1820；　p。　　274。　　On　the　number　of　the　facial　muscles；　see　vol。　　iv。　　pp。　　209…211。
  ＇22＇　〃　‘Mimik　und　Physiognomik；'　1867；　s。　　91。
  Finally；　I　must　have　the　pleasure　of　expressing　my　obligations　to　Mr。　Rejlander　for　the　trouble　which　he　has　taken　in　photographing　for　me　various　expressions　and　gestures。　　I　am　also　indebted　to　Herr　Kindermann；　of　Hamburg；　for　the　loan　of　some　excellent　negatives　of　crying　infants；　and　to　Dr。　Wallich　for　a　charming　one　of　a　smiling　girl。　I　have　already　expressed　my　obligations　to　Dr。　Duchenne　for　generously　permitting　me　to　have　some　of　his　large　photographs　copied　and　reduced。　All　these　photographs　have　been　printed　by　the　Heliotype　process；　and　the　accuracy　of　the　copy　is　thus　guaranteed。　　These　plates　are　referred　to　by　Roman　numerals。
  I　am　also　greatly　indebted　to　Mr。　T。　W。　Wood　for　the　extreme　pains　which　he　has　taken　in　drawing　from　life　the　expressions　of　various　animals。　　A　distinguished　artist；　Mr。　Riviere；　has　had　the　kindness　to　give　me　two　drawings　of　dogsone　in　a　hostile　and　the　other　in　a　humble　and　caressing　frame　of　mind。　Mr。　A。　May　has　also　given　me　two　similar　sketches　of　dogs。　Mr。　Cooper　has　taken　much　care　in　cutting　the　blocks。　Some　of　the　photographs　and　drawings；　namely；　those　by　Mr。　May；　and　those　by　Mr。　Wolf　of　the　Cynopithecus；　were　first　reproduced　by　Mr。　Cooper　on　wood　by　means　of　photography；　and　then　engraved：　by　this　means　almost　complete　fidelity　is　ensured。
  CHAPTER　I。
  GENERAL　PRINCIPLES　OF　EXPRESSION。
  The　three　chief　principles　statedThe　first　principleServiceable　actions　become　habitual　in　association　with　certain　states　of　the　mind；　and　are　performed　whether　or　not　of　service　in　each　particular　case　The　force　of　habitInheritanceAssociated　habitual　movements　in　man　Reflex　actionsPassage　of　habits　into　reflex　actionsAssociated　habitual　movements　in　the　lower　animalsConcluding　remarks。
  I　WILL　begin　by　giving　the　three　Principles；　which　appear　to　me　to　account　for　most　of　the　expressions　and　gestures　involuntarily　used　by　man　and　the　lower　animals；　under　the　influence　of　various　emotions　and　sensations。＇1＇　I　arrived；　however；　at　these　three　Principles　only　at　the　close　of　my　observations。　　They　will　be　discussed　in　the　present　and　two　following　chapters　in　a　general　manner。　Facts　observed　both　with　man　and　the　lower　animals　will　here　be　made　use　of；　but　the　latter　facts　are　preferable；　as　less　likely　to　deceive　us。　In　the　fourth　and　fifth　chapters；　I　will　describe　the　special　expressions　of　some　of　the　lower　animals；　and　in　the　succeeding　chapters　those　of　man。　　Everyone　will　thus　be　able　to　judge　for　himself；　how　far　my　three　principles　throw　light　on　the　theory　of　the　subject。　It　appears　to　me　that　so　many　expressions　are　thus　explained　in　a　fairly　satisfactory　manner；　that　probably　all　will　hereafter　be　found　to　come　under　the　same　or　closely　analogous　heads。　I　need　hardly　premise　that　movements　or　changes　in　any　part　of　the　body；　as　the　wagging　of　a　dog's　tail；　the　drawing　back　of　a　horse's　ears；　the　shrugging　of　a　man's　shoulders；　or　the　dilatation　of　the　capillary　vessels　of　the　skin；may　all　equally　well　serve　for　expression。　The　three　Principles　are　as　follows。
  ＇1＇　Mr。　Herbert　Spencer　（‘Essays；'　Second　Series；　1863；　p。　138）　has　drawn　a　clear　distinction　between　emotions　and　sensations；　the　latter　being　〃generated　in　our　corporeal　framework。〃　He　classes　as　Feelings　both　emotions　and…sensations。
  I。　_The　principle　of　serviceable　associated　Habits_。Certain　complex　actions　are　of　direct　or　indirect　service　under　certain　states　of　the　mind；　in　order　to　relieve　or　gratify　certain　sensations；　desires；　&c。；　and　whenever　the　same　state　of　mind　is　induced；　however　feebly；　there　is　a　tendency　through　the　force　of　habit　and　association　for　the　same　movements　to　be　performed；　though　they　may　not　then　be　of　the　least　use。　　Some　actions　ordinarily　associated　through　habit　with　certain　states　of　the　mind　may　be　partially　repressed　through　the　will；　and　in　such　cases　the　muscles　which　are　least　under　the　separate　control　of　the　will　are　the　most　liable　still　to　act；　causing　movements　which　we　recognize　as　expressive。　　In　certain　other　cases　the　checking　of　one　habitual　movement　requires　other　slight　movements；　and　these　are　likewise　expressive。
  II。　　_The　principle　of　Antithesis_。Certain　states　of　the　mind　lead　to　certain　habitual　actions；　which　are　of　service；　as　under　our　first　principle。　Now　when　a　directly　opposite　state　of　mind　is　induced；　there　is　a　strong　and　involuntary　tendency　to　the　performance　of　movements　of　a　directly　opposite　nature；　though　these　are　of　no　use；　and　such　movements　are　in　some　cases　highly　expressive。
  III。　　_The　principle　of　actions　due　to　the　constitution　of　the　Nervous　System；　independently　from　the　first　of　the　Will；　and　independently　to　a　certain　extent　of　Habit_。…　When　the　sensorium　is　strongly　excited；　nerve…force　is　generated　in　excess；　and　is　transmitted　in　certain　definite　directions；　depending　on　the　connection　of　the　nerve…cells；　and　partly　on　habit：　or　the　supply　of　nerve…force　may；　as　it　appears；　be　interrupted。　Effects　are　thus　produced　which　we　recognize　as　expressive。　This　third　principle　may；　for　the　sake　of　brevity；　be　called　that　of　the　direct　action　of　the　nervous　system。
  With　respect　to　our　_first　Principle_；　it　is　notorious　how　powerful　is　the　force　of　habit。　　The　most　complex　and　difficult　movements　can　in　time　be　performed　without　the　least　effort　or　consciousness。　　It　is　not　positively　known　how　it　comes　that　habit　is　so　efficient　in　facilitating　complex　movements；　but　physiologists　admit＇2＇　〃that　the　conducting　power　of　the　nervous　fibres　increases　with　the　frequency　of　their　excitement。〃　This　applies　to　the　nerves　of　motion　and　sensation；　as　well　as　to　those　connected　with　the　act　of　thinking。　That　some　physical　change　is　produced　in　the　nerve…cells　or　nerves　which　are　habitually　used　can　hardly　be　doubted；　for　otherwise　it　is　impossible　to　understand　how　the　tendency　to　certain　acquired　movements　is　inherited。　　That　they　are　inherited　we　see　with　horses　in　certain　transmitted　paces；　such　as　cantering　and　ambling；　which　are　not　natural　to　them；　in　the　pointing　of　young　pointers　and　the　setting　of　young　setters　in　the　peculiar　manner　of　flight　of　certain　breeds　of　the　pigeon；　&c。　We　have　analogous　cases　with　mankind　in　the　inheritance　of　tricks　or　unusual　gestures；　to　which　we　shall　presently　recur。　To　those　who　admit　the　gradual　evolution　of　species；　a　most　striking　instance　of　the　perfection　with　which　the　most　difficult　consensual　movements　can　be　transmitted；　is　afforded　by　the　humming…bird　Sphinx…moth　（_Macroglossa_）；　for　this　moth；　shortly　after　its　emergence　from　the　cocoon；　as　shown　by　the　bloom　on　its　unruffled　scales；　may　be　seen　poised　stationary　in　the　air；　with　its　long　hair…like　proboscis　uncurled　and　inserted　into　the　minute　orifices　of　flowers；　and　no　one；　I　believe；　has　ever　seen　this　moth　learning　to　perform　its　difficult　task；　which　requires　such　unerring　aim。
  ＇2＇　Muller；　‘Elements　of　Physiology；'　Eng。　　translat。　　vol。　　ii。　　p。　　939。　See　also　Mr。　H。　Spencer's　interesting　speculations　on　the　same　subject；　and　on　the　genesis　of　nerves；　in　his　‘Principles　of　Biology；'　vol。　　ii。　　p。　　346；　and　in　his　‘Principles　of　Psychology；'　2nd　edit。　　pp。　　511…557。
  When　there　exists　an　inherited　or　instinctive　tendency　to　the　performance　of　an　action；　or　an　inherited　taste　for　certain　kinds　of　food；　some　degree　of　habit　in　the　individual　is　often　or　generally　requisite。　We　find　this　in　the　paces　of　the　horse；　and　to　a　certain　extent　in　the　pointing　of　dogs；　although　some　young　dogs　point　excellently　the　first　time　they　are　taken　out；　yet　they　often　associate　the　proper　inherited　attitude　with　a　wrong　odour；　and　even　with　eyesight。　I　have　heard　it　asserted　that　if　a　calf　be　allowed　to　suck　its　mother　only　once；　it　is　much　more　difficult　afterwards　to　rear　it　by　hand。＇3＇　Caterpillars　which　have　been　fed　on　the　leaves　of　one　kind　of　tree；　have　been　known　to　perish　from　hunger　rather　than　to　eat　the　leaves　of　another　tree；　although　this　afforded　them　their　proper　food；　under　a　state　of　nature；＇4＇　and　so　it　is　in　many　other　cases。
  ＇3＇　A　remark　to　much　the　same　effect　was　made　long