auses　hereafter　to　be　discussed；　are　somewhat　protruded；　and　this　form　of　the　mouth；　if　the　voice　be　at　all　exerted；　produces；　according　to　Helmholtz；　the　sound　of　the　vowel　_O_。　　Certainly　a　deep　sound　of　a　prolonged　_Oh！_　may　be　heard　from　a　whole　crowd　of　people　immediately　after　witnessing　any　astonishing　spectacle。　If；　together　with　surprise；　pain　be　felt；　there　is　a　tendency　to　contract　all　the　muscles　of　the　body；　including　those　of　the　face；　and　the　lips　will　then　be　drawn　back；　and　this　will　perhaps　account　for　the　sound　becoming　higher　and　assuming　the　character　of　_Ah！_　or　_Ach！_　As　fear　causes　all　the　muscles　of　the　body　to　tremble；　the　voice　naturally　becomes　tremulous；　and　at　the　same　time　husky　from　the　dryness　of　the　mouth；　owing　to　the　salivary　glands　failing　to　act。　　Why　the　laughter　of　man　and　the　tittering　of　monkeys　should　be　a　rapidly　reiterated　sound；　cannot　be　explained。　During　the　utterance　of　these　sounds；　the　mouth　is　transversely　elongated　by　the　corners　being　drawn　backwards　and　upwards；　and　of　this　fact　an　explanation　will　be　attempted　in　a　future　chapter。　But　the　whole　subject　of　the　differences　of　the　sounds　produced　under　different　states　of　the　mind　is　so　obscure；　that　I　have　succeeded　in　throwing　hardly　any　light　on　it；　and　the　remarks　which　I　have　made；　have　but　little　significance。
  All　the　sounds　hitherto　noticed　depend　on　the　respiratory　organs；　but　sounds　produced　by　wholly　different　means　are　likewise　expressive。　Rabbits　stamp　loudly　on　the　ground　as　a　signal　to　their　comrades；　and　if　a　man　knows　how　to　do　so　properly；　he　may　on　a　quiet　evening　hear　the　rabbits　answering　him　all　around。　　These　animals；　as　well　as　some　others；　also　stamp　on　the　ground　when　made　angry。　Porcupines　rattle　their　quills　and　vibrate　their　tails　when　angered；　and　one　behaved　in　this　manner　when　a　live　snake　was　placed　in　its　compartment。　The　tail　of　the　quills　on　the　tail　are　very　different　from　those　on　the　body：　they　are　short；　hollow；　thin　like　a　goose…quill；　with　their　ends　transversely　truncated；　so　that　they　are　open；　they　are　supported　on　long；　thin；　elastic　foot…stalks。　Now；　when　the　tail　is　rapidly　shaken；　these　hollow　quills　strike　against　each　other　and　produce；　as　I　heard　in　the　presence　of　Mr。　Bartlett；　a　peculiar　continuous　sound。　　We　can；　I　think；　understand　why　porcupines　have　been　provided；　through　the　modification　of　their　protective　spines；　with　this　special　sound…producing　instrument。　They　are　nocturnal　animals；　and　if　they　scented　or　heard　a　prowling　beast　of　prey；　it　would　be　a　great　advantage　to　them　in　the　dark　to　give　warning　to　their　enemy　what　they　were；　and　that　they　were　furnished　with　dangerous　spines。　　They　would　thus　escape　being　attacked。　They　are；　as　I　may　add；　so　fully　conscious　of　the　power　of　their　weapons；　that　when　enraged　they　will　charge　backwards　with　their　spines　erected；　yet　still　inclined　backwards。
  Many　birds　during　their　courtship　produce　diversified　sounds　by　means　of　specially　adapted　feathers。　　Storks；　when　excited；　make　a　loud　clattering　noise　with　their　beaks。　　Some　snakes　produce　a　grating　or　rattling　noise。　　Many　insects　stridulate　by　rubbing　together　specially　modified　parts　of　their　hard　integuments。　This　stridulation　generally　serves　as　a　sexual　charm　or　call；　but　it　is　likewise　used　to　express　different　emotions。＇8＇　Every　one　who　has　attended　to　bees　knows　that　their　humming　changes　when　they　are　angry；　and　this　serves　as　a　warning　that　there　is　danger　of　being　stung。　I　have　made　these　few　remarks　because　some　writers　have　laid　so　much　stress　on　the　vocal　and　respiratory　organs　as　having　been　specially　adapted　for　expression；　that　it　was　advisable　to　show　that　sounds　otherwise　produced　serve　equally　well　for　the　same　purpose。
  _Erection　of　the　dermal　appendages_。Hardly　any　expressive　movement　is　so　general　as　the　involuntary　erection　of　the　hairs；　feathers　and　other　dermal　appendages；　for　it　is　common　throughout　three　of　the　great　vertebrate　classes。　　These　appendages　are　erected　under　the　excitement　of　anger　or　terror；　more　especially　when　these　emotions　are　combined；　or　quickly　succeed　each　other。　The　action　serves　to　make　the　animal　appear　larger　and　more　frightful　to　its　enemies　or　rivals；　and　is　generally　accompanied　by　various　voluntary　movements　adapted　for　the　same　purpose；　and　by　the　utterance　of　savage　sounds。　　Mr。　Bartlett；　who　has　had　such　wide　experience　with　animals　of　all　kinds；　does　not　doubt　that　this　is　the　case；　but　it　is　a　different　question　whether　the　power　of　erection　was　primarily　acquired　for　this　special　purpose。
  ＇8＇　I　have　given　some　details　on　this　subject　in　my　‘Descent　of　Man；'　vol。　　i。　　pp。　　352；　384。
  I　will　first　give　a　considerable　body　of　facts　showing　how　general　this　action　is　with　mammals；　birds　and　reptiles；　retaining　what　I　have　to　say　in　regard　to　man　for　a　future　chapter。　Mr。　Sutton；　the　intelligent　keeper　in　the　Zoological　Gardens；　carefully　observed　for　me　the　Chimpanzee　and　Orang；　and　he　states　that　when　they　are　suddenly　frightened；　as　by　a　thunderstorm；　or　when　they　are　made　angry；　as　by　being　teased；　their　hair　becomes　erect。　I　saw　a　chimpanzee　who　was　alarmed　at　the　sight　of　a　black　coalheaver；　and　the　hair　rose　all　over　his　body；　he　made　little　starts　forward　as　if　to　attack　the　man；　without　any　real　intention　of　doing　so；　but　with　the　hope；　as　the　keeper　remarked；　of　frightening　him。　The　Gorilla；　when　enraged；　is　described　by　Mr。　Ford＇9＇　as　having　his　crest　of　hair　〃erect　and　projecting　forward；　his　nostrils　dilated；　and　his　under　lip　thrown　down；　at　the　same　time　uttering　his　characteristic　yell；　designed；　it　would　seem；　to　terrify　his　antagonists。〃　　I　saw　the　hair　on　the　Anubis　baboon；　when　angered　bristling　along　the　back；　from　the　neck　to　the　loins；　but　not　on　the　rump　or　other　parts　of　the　body。　I　took　a　stuffed　snake　into　the　monkey…house；　and　the　hair　on　several　of　the　species　instantly　became　erect；　especially　on　their　tails；　as　I　particularly　noticed　with　the　_Cereopithecus　nictitans_。　Brehm　states＇10＇　that　the　_Midas　aedipus_　（belonging　to　the　American　division）　when　excited　erects　its　mane；　in　order；　as　he　adds；　to　make　itself　as　frightful　as　possible。
  ＇9＇　As　quoted　in　Huxley's　‘Evidence　as　to　Man's　Place　in　Nature；'　1863；　p。　　52。
  With　the　Carnivora　the　erection　of　the　hair　seems　to　be　almost　universal；　often　accompanied　by　threatening　movements；　the　uncovering　of　the　teeth　and　the　utterance　of　savage　growls。　In　the　Herpestes；　I　have　seen　the　hair　on　end　over　nearly　the　whole　body；　including　the　tail；　and　the　dorsal　crest　is　erected　in　a　conspicuous　manner　by　the　Hyaena　and　Proteles。　　The　enraged　lion　erects　his　mane。　The　bristling　of　the　hair　along　the　neck　and　back　of　the　dog；　and　over　the　whole　body　of　the　cat；　especially　on　the　tail；　is　familiar　to　every　one。　　With　the　cat　it　apparently　occurs　only　under　fear；　with　the　dog；　under　anger　and　fear；　but　not；　as　far　as　I　have　observed；　under　abject　fear；　as　when　a　dog　is　going　to　be　flogged　by　a　severe　gamekeeper。　　If；　however；　the　dog　shows　fight；　as　sometimes　happens；　up　goes　his　hair。　I　have　often　noticed　that　the　hair　of　a　dog　is　particularly　liable　to　rise；　if　he　is　half　angry　and　half　afraid；　as　on　beholding　some　object　only　indistinctly　seen　in　the　dusk。
  I　have　been　assured　by　a　veterinary　surgeon　that　he　has　often　seen　the　hair　erected　on　horses　and　cattle；　on　which　he　had　operated　and　was　again　going　to　operate。　　When　I　showed　a　stuffed　snake　to　a　Peccary；　the　hair　rose　in　a　wonderful　manner　along　its　back；　and　so　it　does　with　the　boar　when　enraged。　An　Elk　which　gored　a　man　to　death　in　the　United　States；　is　described　as　first　brandishing　his　antlers；　squealing　with　rage　and　stamping　on　the　ground；　〃at　length　his　hair　was　seen　to　rise　and　stand　on　end；〃　and　then　he　plunged　forward　to　the　attack。＇11＇　The　hair　likewise　becomes　erect　on　goats；　and；　as　I　hear　from　Mr。　Blyth；　on　some　Indian　antelopes。　I　have　seen　it　erected　on　the　hairy　Ant…eater；　and　on　the　Agouti；　one　of　the　Rodents。　　A　female　Bat；＇12＇　which　reared　her　young　under　confinement；　when　any　one　looked　into　the　cage　〃erected　the　fur　on　her　back；　and　bit　viciously　at　intruding　fingers。〃
  ＇10＇　Illust。　　Thierleben；　1864；　B。　i。　　s。　　130。
  Birds　belonging　to　all　the　chief　Orders　ruffle　their　feathers　when　angry　or　frightened。　　Every　one　must　have　seen　two　cocks；　even　quite　young　birds；　preparing　to　fight　with　erected　neck…hackles；　nor　can　these　feathers　when　erected　serve　as　a　means　of　defence；　for　cock…fighters　have　found　by　experience　that　it　is　advantageous　to　trim　them。　　The　male　Ruff　（_Machetes　pugnax_）　likewise　erects　its　collar　of　feathers　when　fighting。　When　a　dog　approaches　a　common　hen　with　her　chickens；　she　spreads　out　her　wings；　raises　her　tail；　ruffles　all　her　feathers；　and　looking　as　ferocious　as　possible；　dashes　at　the　intruder。　The　tail　is　not　always　held　in　exactly　the　same　position；　it　is　sometimes　so　much　erected；　that　the　central　feathers；　as　in　the　accompanying　drawing；　almost　touch　the　back。　　Swans；　when　angered；　likewise　raise　their　wings　and　tail；　and　erect　their　feathers。　They　open　their　beaks；　and　make　by　paddling　little　rapid　starts　forwards；　against　any　one　who　approaches　the　water's　edge　too　closely。　Tropic　birds＇13＇　when　disturbed　on