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 their nests are said not to fly away； but 〃merely to stick out their feathers and scream。〃 The Barn…owl； when approached 〃instantly swells out its plumage； extends its wings and tail； hisses and clacks its mandibles with force and rapidity。〃＇14＇ So do other kinds of owls。 Hawks； as I am
＇11＇ The Hon。 J。 Caton； Ottawa Acad。 of Nat。 Sciences； May； 1868； pp。 36； 40。 For the _Capra； AEgagrus_； ‘Land and Water；' 1867； p。 37。
＇12＇ ‘Land and Water；' July 20； 1867； p。 659。
＇13＇ _Phaeton rubricauda_： ‘Ibis；' vol。 iii。 1861； p。 180。
｛illust。 caption = FIG。 12Hen driving away a dog from her chickens。 Drawn from life by Mr。 Wood。 informed by Mr。 Jenner Weir； likewise ruffle their feathers； and spread out their wings and tail under similar circumstances。 Some kinds of parrots erect their feathers； and I have seen this action in the Cassowary； when angered at the sight of an Ant…eater。 Young cuckoos in the nest； raise their feathers； open their mouths widely； and make themselves as frightful as possible。 ＇14＇ On the _Strix flammea_； Audubon； ‘Ornithological Biography；' 1864； vol。 ii。 p。 407。 I have observed other cases in the Zoological Gardens。Small birds； also； as I hear from Mr。 Weir； such as various finches； buntings and warblers； when angry； ｛illust。 caption = FIG。 13。Swan driving away an intruder。 Drawn from life by Mr。 Wood。｝
ruffle all their feathers； or only those round the neck； or they spread out their wings and tail…feathers。 With their plumage in this state； they rush at each other with open beaks and threatening gestures。 Mr。 Weir concludes from his large experience that the erection of the feathers is caused much more by anger than by fear。 He gives as an instance a hybrid goldfinch of a most irascible disposition； which when approached too closely by a servant； instantly assumes the appearance of a ball of ruffled feathers。 He believes that birds when frightened； as a general rule； closely adpress all their feathers； and their consequently diminished size is often astonishing。 As soon as they recover from their fear or surprise； the first thing which they do is to shake out their feathers。 The best instances of this adpression of the feathers and apparent shrinking of the body from fear； which Mr。 Weir has noticed； has been in the quail and grass…parrakeet。＇15＇ The habit is intelligible in these birds from their being accustomed； when in danger； either to squat on the ground or to sit motionless on a branch； so as to escape detection。 Though； with birds； anger may be the chief and commonest cause of the erection of the feathers； it is probable that young cuckoos when looked at in the nest； and a hen with her chickens when approached by a dog； feel at least some terror。 Mr。 Tegetmeier informs me that with game…cocks； the erection of the feathers on the head has long been recognized in the cock…pit as a sign of cowardice。
The males of some lizards； when fighting together during their courtship； expand their throat pouches or frills； and erect their dorsal crests。＇16＇ But Dr。 Gunther does not believe that they can erect their separate spines or scales。
We thus see how generally throughout the two higher vertebrate classes； and with some reptiles； the dermal appendages are erected under the influence of anger and fear。 The movement is effected； as we know from Kolliker's interesting discovery； by the contraction of minute； unstriped； involuntary muscles；＇17＇ often called _arrectores pili_； which are attached to the capsules of the separate hairs； feathers； &c。 By the contraction of these muscles the hairs can be instantly erected； as we see in a dog； being at the same time drawn a little out of their sockets； they are afterwards quickly depressed。 The vast number of these minute muscles over the whole body of a hairy quadruped is astonishing。 The erection of the hair is； however； aided in some cases； as with that on the head of a man； by the striped and voluntary muscles of the underlying _panniculus carnosus_。 It is by the action of these latter muscles； that the hedgehog erects its spines。 It appears； also； from the researches of Leydig＇18＇ and others； that striped fibres extend from the panniculus to some of the larger hairs； such as the vibrissae of certain quadrupeds。 The _arrectores pili_ contract not only under the above emotions； but from the application of cold to the surface。 I remember that my mules and dogs； brought from a lower and warmer country； after spending a night on the bleak Cordillera； had the hair all over their bodies as erect as under the greatest terror。 We see the same action in our own _goose…skin_ during the chill before a fever…fit。 Mr。 Lister has also found；＇19＇ that tickling a neighbouring part of the skin causes the erection and protrusion of the hairs。
＇15＇ _Melopsittacus undulatus_。 See an account of its habits by Gould； ‘Handbook of Birds of Australia；' 1865； vol。 ii。 p。 82。
＇16＇ See； for instance； the account which I have given （‘Descent of Man；' vol。 ii。 p。 32） of an Anolis and Draco。
＇17＇ These muscles are described in his well…known works。 I am greatly indebted to this distinguished observer for having given me in a letter information on this same subject。
From these facts it is manifest that the erection of the dermal appendages is a reflex action； independent of the will； and this action must be looked at； when； occurring under the influence of anger or fear； not as a power acquired for the sake of some advantage； but as an incidental result； at least to a large extent； of the sensorium being affected。 The result； in as far as it is incidental； may be compared with the profuse sweating from an agony of pain or terror。 Nevertheless； it is remarkable how slight an excitement often suffices to cause the hair to become erect； as when two dogs pretend to fight together in play。 We have； also； seen in a large number of animals； belonging to widely distinct classes； that the erection of the hair or feathers is almost always accompanied by various voluntary movements by threatening gestures； opening the mouth； uncovering the teeth； spreading out of the wings and tail by birds； and by the utterance of harsh sounds； and the purpose of these voluntary movements is unmistakable。 Therefore it seems hardly credible that the co…ordinated erection of the dermal appendages； by which the animal is made to appear larger and more terrible to its enemies or rivals； should be altogether an incidental and purposeless result of the disturbance of the sensorium。 This seems almost as incredible as that the erection by the hedgehog of its spines； or of the quills by the porcupine； or of the ornamental plumes by many birds during their courtship。 should all be purposeless actions。
＇18＇ ‘Lehrbuch der Histologie des Menschen；' 1857； s。 82。 I owe to Prof。 W。 Turner's kindness an extract from this work。
＇19＇ ‘Quarterly Journal of Microscopical Science；' 1853； vol。 i。 p。 262。
We here encounter a great difficulty。 How can the contraction of the unstriped and involuntary _arrectores pili_ have been co…ordinated with that of various voluntary muscles for the same special purpose？ If we could believe that the arrectores primordially had been voluntary muscles； and had since lost their stripes and become involuntary； the case would be comparatively simple。 I am not； however； aware that there is any evidence in favour of this view； although the reversed transition would not have presented any great difficulty； as the voluntary muscles are in an unstriped condition in the embryos of the higher animals； and in the larvae of some crustaceans。 Moreover in the deeper layers of the skin of adult birds； the muscular network is； according to Leydig；＇20＇ in a transitional condition； the fibres exhibiting only indications of transverse striation。
Another explanation seems possible。 We may admit that originally the _arrectores pili_ were slightly acted on in a direct manner； under the influence of rage and terror； by the disturbance of the nervous system； as is undoubtedly the case with our so…called _goose…skin_ before a fever…fit。 Animals have been re