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CHAPTER IV - MEANS OF EXPRESSION IN ANIMALS.

Charles Darwin (1809-1882)

CHAPTER IV.



MEANS OF EXPRESSION IN ANIMALS.



The emission of Sounds--Vocal sounds--Sounds otherwise produced--

Erection of the dermal appendages, hairs, feathers, &c., under

the emotions of anger and terror--The drawing back of the ears

as a preparation for fighting, and as an expression of anger--

Erection of the ears and raising the head, a sign of attention.





IN this and the following chapter I will describe, but only in

sufficient detail to illustrate my subject, the expressive movements,

under different states of the mind, of some few well-known animals.

But before considering them in due succession, it will save much

useless repetition to discuss certain means of expression common

to most of them.



_The emission of Sounds_.--With many kinds of animals, man included, the 
vocal

organs are efficient in the highest degree as a means of expression.

We have seen, in the last chapter, that when the sensorium is strongly

excited, the muscles of the body are generally thrown into violent action;

and as a consequence, loud sounds are uttered, however silent

the animal may generally be, and although the sounds may be of no use.

Hares and rabbits for instance, never, I believe, use their vocal

organs except in the extremity of suffering; as, when a wounded hare

is killed by the sportsman, or when a young rabbit is caught by a stoat.

Cattle and horses suffer great pain in silence; but when this is excessive,

and especially when associated with terror, they utter fearful sounds.

I have often recognized, from a distance on the Pampas, the agonized

death-bellow of the cattle, when caught by the lasso and hamstrung.

It is said that horses, when attacked by wolves, utter loud and peculiar

screams of distress.



Involuntary and purposeless contractions of the muscles of the chest

and glottis, excited in the above manner, may have first given rise

to the emission of vocal sounds.  But the voice is now largely used

by many animals for various purposes; and habit seems to have played

an important part in its employment under other circumstances.

Naturalists have remarked, I believe with truth, that social animals,

from habitually using their vocal organs as a means of intercommunication,

use them on other occasions much more freely than other animals.

But there are marked exceptions to this rule, for instance, with the 
rabbit.

The principle, also, of association, which is so widely extended in its 
power,

has likewise played its part.  Hence it follows that the voice, from having

been habitually employed as a serviceable aid under certain conditions,

inducing pleasure, pain, rage, &c,, is commonly used whenever the same

sensations or emotions are excited, under quite different conditions,

or in a lesser degree.



The sexes of many animals incessantly call for each other during

the breeding-season; and in not a few cases, the male endeavours

thus to charm or excite the female.  This, indeed, seems to have

been the primeval use and means of development of the voice,

as I have attempted to show in my `Descent of Man.'  Thus the use

of the vocal organs will have become associated with the anticipation

of the strongest pleasure which animals are capable of feeling.

Animals which live in society often call to each other when separated,

and evidently feel much joy at meeting; as we see with a horse,

on the return of his companion, for whom he has been neighing.

The mother calls incessantly for her lost young ones; for instance,

a cow for her calf; and the young of many animals call for their mothers.

When a flock of sheep is scattered, the ewes bleat incessantly for

their lambs, and their mutual pleasure at coming together is manifest.

Woe betide the man who meddles with the young of the larger and

fiercer quadrupeds, if they hear the cry of distress from their young.

Rage leads to the violent exertion of all the muscles, including those

of the voice; and some animals, when enraged, endeavour to strike

terror into their enemies by its power and harshness, as the lion

does by roaring, and the dog by growling.  I infer that their object

is to strike terror, because the lion at the same time erects

the hair of its mane, and the dog the hair along its back, and thus

they make themselves appear as large and terrible as possible.

Rival males try to excel and challenge each other by their voices,

and this leads to deadly contests.  Thus the use of the voice will have

become associated with the emotion of anger, however it may be aroused.

We have also seen that intense pain, like rage, leads to violent outcries,

and the exertion of screaming by itself gives some relief; and thus

the use of the voice will have become associated with suffering

of any kind.



The cause of widely different sounds being uttered under different

emotions and sensations is a very obscure subject.  Nor does

the rule always hold good that there is any marked difference.

For instance with the dog, the bark of anger and that of joy

do not differ much, though they can be distinguished.

It is not probable that any precise explanation of the cause

or source of each particular sound, under different states

of the mind, will ever be given.  We now that some animals,

after being domesticated, have acquired the habit of uttering

sounds which were not natural to them.[1] Thus domestic dogs,

and even tamed jackals, have learnt to bark, which is a noise

not proper to any species of the genus, with the exception

of the _Canis latrans_ of North America, which is said to bark.

Some breeds, also, of the domestic pigeon have learnt to coo

in a new and quite peculiar manner.



The character of the human voice, under the influence of

various emotions, has been discussed by Mr. Herbert Spencer[2]

in his interesting essay on Music.  He clearly shows that the voice

alters much under different conditions, in loudness and in quality,

that is, in resonance and _timbre_, in pitch and intervals.

No one can listen to an eloquent orator or preacher, or to a man

calling angrily to another, or to one expressing astonishment,

without being struck with the truth of Mr. Spencer's remarks.

It is curious how early in life the modulation of the voice

becomes expressive.  With one of my children, under the age

of two years, I clearly perceived that his humph of assent was

rendered by a slight modulation strongly emphatic; and that by a

peculiar whine his negative expressed obstinate determination.

Mr. Spencer further shows that emotional speech, in all the above

respects is intimately related to vocal music, and consequently

to instrumental music; and he attempts to explain the characteristic

qualities of both on physiological grounds--namely, on "the

general law that a feeling is a stimulus to muscular action."

It may be admitted that the voice is affected through this law;

but the explanation appears to me too general and vague to throw much

light on the various differences, with the exception of that of loudness,

between ordinary speech and emotional speech, or singing.





[1] See the evidence on this head in my `Variation of Animals

and Plants under Domestication,' vol.  i.  p.  27.  On the cooing

of pigeons, vol.  i.  pp.  154, 155.



[2] `Essays, Scientific, Political, and Speculative,' 1858.

`The Origin and Function of Music,' p.  359.



This remark holds good, whether we believe that the various

qualities of the voice originated in speaking under the excitement

of strong feelings, and that these qualities have subsequently been

transferred to vocal music; or whether we believe, as I maintain,

that the habit of uttering musical sounds was first developed,

as a means of courtship, in the early progenitors of man,

and thus became associated with the strongest emotions of which

they were capable,--namely, ardent love, rivalry and triumph.

That animals utter musical notes is familiar to every one, as we

may daily hear in the singing of birds.  It is a more remarkable

fact that an ape, one of the Gibbons, produces an exact octave

of musical sounds, ascending and descending the scale by halftones;

so that this monkey "alone of brute mammals may be said to

sing."[3] From this fact, and from the analogy of other animals,

I have been led to infer that the progenitors of man probably

uttered musical tones, before they had acquired the power

of articulate speech; and that consequently, when the voice

is used under any strong emotion, it tends to assume,

through the principle of association, a musical character.

We can plainly perceive, with some of the lower animals,

that the males employ their voices to please the females,

and that they themselves take pleasure in their own vocal utterances;

but why particular sounds are uttered, and why these give

pleasure cannot at present be explained.





[3] `The Descent of Man,' 1870, vol.  ii.  p.  332.  The words

quoted are from Professor Owen.  It has lately been shown

that some quadrupeds much lower in the scale than monkeys,

namely Rodents, are able to produce correct musical tones:

see the account of a singing Hesperomys, by the Rev. S. Lockwood,

in the `American Naturalist,' vol.  v.  December, 1871, p.  761.



That the pitch of the voice bears some relation to certain states of

feeling is tolerably clear.  A person gently complaining of ill-treatment,

or slightly suffering, almost always speaks in a high-pitched voice.

Dogs, when a little impatient, often make a high piping note through

their noses, which at once strikes us as plaintive;[4] but how

difficult it is to know whether the sound is essentially plaintive,

or only appears so in this particular case, from our having learnt

by experience what it means!  Rengger, states[5] that the monkeys

(_Cebus azaroe_), which he kept in Paraguay, expressed astonishment

by a half-piping, half-snarling noise; anger or impatience,

by repeating the sound _hu hu_ in a deeper, grunting voice;

and fright or pain, by shrill screams.  On the other hand, with mankind,

deep groans and high piercing screams equally express an agony of pain.

Laughter maybe either high or low; so that, with adult men, as Haller

long ago remarked,[6] the sound partakes of the character of the vowels

(as pronounced in German) _O_ and _A_; whilst with children and women,

it has more of the character of _E_ and _I_; and these latter vowel-sounds

naturally have, as Helmholtz has shown, a higher pitch than the former;

yet both tones of laughter equally express enjoyment or amusement.



In considering the mode in which vocal utterances express emotion,

we are naturally led to inquire into the cause of what is called

"expression" in music.  Upon this point Mr. Litchfield, who has long

attended to the subject of music, has been so kind as to give me

the following remarks:--"The question, what is the essence of musical

`expression' involves a number of obscure points, which, so far as I

am aware, are as yet unsolved enigmas.  Up to a certain point, however,

any law which is found to hold as to the expression of the emotions

by simple sounds must apply to the more developed mode of expression

in song, which may be taken as the primary type of all music.

A great part of the emotional effect of a song depends on

the character of the action by which the sounds are produced.

In songs, for instance, which express great vehemence of passion,

the effect often chiefly depends on the forcible utterance of some one

or two characteristic passages which demand great exertion of vocal force;

and it will be frequently noticed that a song of this character

fails of its proper effect when sung by a voice of sufficient power

and range to give the characteristic passages without much exertion.

This is, no doubt, the secret of the loss of effect so often

produced by the transposition of a song from one key to another.

The effect is thus seen to depend not merely on the actual sounds,

but also in part on the nature of the action which produces the sounds.

Indeed it is obvious that whenever we feel the `expression'

of a song to be due to its quickness or slowness of movement--

to smoothness of flow, loudness of utterance, and so on--we are,

in fact, interpreting the muscular actions which produce sound,

in the same way in which we interpret muscular action generally.

But this leaves unexplained the more subtle and more specific

effect which we call the MUSICAL expression of the song--

the delight given by its melody, or even by the separate sounds

which make up the melody.  This is an effect indefinable in language--

one which, so far as I am aware, no one has been able to analyse,

and which the ingenious speculation of Mr. Herbert Spencer as to

the origin of music leaves quite unexplained.  For it is certain

that the MELODIC effect of a series of sounds does not depend in

the least on their loudness or softness, or on their ABSOLUTE pitch.

A tune is always the same tune, whether it is sung loudly or softly,

by a child or a man; whether it is played on a flute or on a trombone.

The purely musical effect of any sound depends on its place

in what is technically called a `scale;' the same sound producing

absolutely different effects on the ear, according as it is heard

in connection with one or another series of sounds.





[4] Mr. Tylor (`Primitive Culture,' 1871, vol.  i.  p.  166), in his

discussion on this subject, alludes to the whining of the dog.



[5] `Naturgeschichte der Saugethiere von Paraguay,' 1830, s.  46.



[6] Quoted by Gratiolet, `De la Physionomie,' 1865, p.  115.



"It is on this RELATIVE association of the sounds that all the

essentially characteristic effects which are summed up in the phrase

`musical expression,' depend.  But why certain associations of

sounds have such-and-such effects, is a problem which yet remains

to be solved.  These effects must indeed, in some way or other,

be connected with the well-known arithmetical relations between

the rates of vibration of the sounds which form a musical scale.

And it is possible--but this is merely a suggestion--that the greater

or less mechanical facility with which the vibrating apparatus

of the human larynx passes from one state of vibration to another,

may have been a primary cause of the greater or less pleasure

produced by various sequences of sounds."



But leaving aside these complex questions and confining ourselves

to the simpler sounds, we can, at least, see some reasons for the

association of certain kinds of sounds with certain states of mind.

A scream, for instance, uttered by a young animal, or by one of

the members of a community, as a call for assistance, will naturally

be loud, prolonged, and high, so as to penetrate to a distance.

For Helmholtz has shown[7] that, owing to the shape of the internal

cavity of the human ear and its consequent power of resonance,

high notes produce a particularly strong impression.  When male

animals utter sounds in order to please the females, they would

naturally employ those which are sweet to the ears of the species;

and it appears that the same sounds are often pleasing to widely

different animals, owing to the similarity of their nervous systems,

as we ourselves perceive in the singing of birds and even

in the chirping of certain tree-frogs giving us pleasure.

On the other hand, sounds produced in order to strike terror

into an enemy, would naturally be harsh or displeasing.



Whether the principle of antithesis has come into play

with sounds, as might perhaps have been expected, is doubtful.

The interrupted, laughing or tittering sounds made by man and by

various kinds of monkeys when pleased, are as different as possible

from the prolonged screams of these animals when distressed.

The deep grunt of satisfaction uttered by a pig, when pleased with

its food, is widely different from its harsh scream of pain or terror.

But with the dog, as lately remarked, the bark of anger and that of

joy are sounds which by no means stand in opposition to each other;

and so it is in some other cases.



There is another obscure point, namely, whether the sounds which are

produced under various states of the mind determine the shape of the mouth,

or whether its shape is not determined by independent causes, and the sound

thus modified.  When young infants cry they open their mouths widely,

and this, no doubt, is necessary for pouring forth a full volume of sound;

but the mouth then assumes, from a quite distinct cause, an almost

quadrangular shape, depending, as will hereafter be explained, on the firm

closing of the eyelids, and consequent drawing up of the upper lip.

How far this square shape of the mouth modifies the wailing or crying 
sound,

I am not prepared to say; but we know from the researches of Helmholtz

and others that the form of the cavity of the mouth and lips determines

the nature and pitch of the vowel sounds which are produced.





[7] `Theorie Physiologique de la Musique,' Paris, 1868, P. 146.

Helmholtz has also fully discussed in this profound work the relation

of the form of the cavity of the mouth to the production of vowel-sounds.



It will also be shown in a future chapter that, under the feeling

of contempt or disgust, there is a tendency, from intelligible causes,

to blow out of the mouth or nostrils, and this produces sounds

like pooh or pish.  When any one is startled or suddenly astonished,

there is an instantaneous tendency, likewise from an intelligible cause,

namely, to be ready for prolonged exertion, to open the mouth widely,

so as to draw a deep and rapid inspiration.  When the next full

expiration follows, the mouth is slightly closed, and the lips,

from causes 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 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.  12--Hen 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

repeatedly excited by rage and terror during many generations;

and consequently the direct effects of the disturbed nervous

system on the dermal appendages will almost certainly

have been increased through habit and through the tendency

of nerve-force to pass readily along accustomed channels.

We shall find this view of the force of habit strikingly

confirmed in a future chapter, where it will be shown that

the hair of the insane is affected in an extraordinary manner,

owing to their repeated accesses of fury and terror.

As soon as with animals the power of erection had thus been

strengthened or increased, they must often have seen the hairs

or feathers erected in rival and enraged males, and the bulk

of their bodies thus increased.  In this case it appears possible

that they might have wished to make themselves appear larger

and more terrible to their enemies, by voluntarily assuming

a threatening attitude and uttering harsh cries; such attitudes

and utterances after a time becoming through habit instinctive.

In this manner actions performed by the contraction

of voluntary muscles might have been combined for the same

special purpose with those effected by involuntary muscles.

It is even possible that animals, when excited and dimly

conscious of some change in the state of their hair, might act

on it by repeated exertions of their attention and will;

for we have reason to believe that the will is able to

influence in an obscure manner the action of some unstriped

or involuntary muscles, as in the period of the peristaltic

movements of the intestines, and in the contraction of the bladder.

Nor must we overlook the part which variation and natural

selection may have played; for the males which succeeded

in making themselves appear the most terrible to their rivals,

or to their other enemies, if not of overwhelming power,

will on an average have left more offspring to inherit their

characteristic qualities, whatever these may be and however

first acquired, than have other males.





[20] `Lehrbuch der Histologie,' 1857, s.  82.



_The inflation of the body, and other means of exciting fear

in an enemy_.--Certain Amphibians and Reptiles, which either have

no spines to erect, or no muscles by which they can be erected,

enlarge themselves when alarmed or angry by inhaling air.

This is well known to be the case with toads and frogs.

The latter animal is made, in AEsop's fable of the `Ox and the Frog,'

to blow itself up from vanity and envy until it burst.

This action must have been observed during the most ancient times, as,

according to Mr. Hensleigh Wedgwood,[21] the word _toad_ expresses

in all the languages of Europe the habit of swelling.  It has been

observed with some of the exotic species in the Zoological Gardens;

and Dr. Gunther believes that it is general throughout the group.

Judging from analogy, the primary purpose probably was to make the body

appear as large and frightful as possible to an enemy; but another,

and perhaps more important secondary advantage is thus gained.

When frogs are seized by snakes, which are their chief enemies,

they enlarge themselves wonderfully; so that if the snake be of

small size, as Dr. Gunther informs me, it cannot swallow the frog,

which thus escapes being devoured.





[21] `Dictionary of English Etymology,' p.  403.



Chameleons and some other lizards inflate themselves when angry.

Thus a species inhabiting Oregon, the _Tapaya Douglasii_, is slow

in its movements and does not bite, but has a ferocious aspect;

"when irritated it springs in a most threatening manner at

anything pointed at it, at the same time opening its mouth

wide and hissing audibly, after which it inflates its body,

and shows other marks of anger."[22]



Several kinds of snakes likewise inflate themselves when irritated.

The puff-adder (_Clotho arietans_) is remarkable in this respect;

but I believe, after carefully watching these animals, that they

do not act thus for the sake of increasing their apparent bulk,

but simply for inhaling a large supply of air, so as to produce

their surprisingly loud, harsh, and prolonged hissing sound.

The Cobras-de-capello, when irritated, enlarge themselves a little,

and hiss moderately; but, at the same time they lift their heads aloft,

and dilate by means of their elongated anterior ribs, the skin on

each side of the neck into a large flat disk,--the so-called hood.

With their widely opened mouths, they then assume a terrific aspect.

The benefit thus derived ought to be considerable, in order to compensate

for the somewhat lessened rapidity (though this is still great)

with which, when dilated, they can strike at their enemies or prey;

on the same principle that a broad, thin piece of wood cannot

be moved through the air so quickly as a small round stick.

An innocuous snake, the _Trovidonotus macrophthalmus_,

an inhabitant of India, likewise dilates its neck when irritated;

and consequently is often mistaken for its compatriot, the deadly

Cobra.[23] This resemblance perhaps serves as some protection

to the Tropidonotus.





[21] See the account of the habits of this animal by Dr, Cooper, as quoted

in `Nature,' April 27, 1871, p.  512.



[22] Dr. Gunther, `Reptiles of British India,' p.  262.



Another innocuous species, the Dasypeltis of South Africa,

blows itself out, distends its neck, hisses and darts at an

intruder.[24] Many other snakes hiss under similar circumstances.

They also rapidly vibrate their protruded tongues; and this

may aid in increasing their terrific appearance.



Snakes possess other means of producing sounds besides hissing.

Many years ago I observed in South America that a venomous Trigonocephalus,

when disturbed, rapidly vibrated the end of its tail, which striking

against the dry grass and twigs produced a rattling noise

that could be distinctly heard at the distance of six feet.[25]

The deadly and fierce _Echis carinata_ of India produces "a

curious prolonged, almost hissing sound in a very different manner,

namely by rubbing "the sides of the folds of its body against

each other," whilst the head remains in almost the same position.

The scales on the sides, and not on other parts of the body,

are strongly keeled, with the keels toothed like a saw;

and as the coiled-up animal rubs its sides together, these grate

against each other.[26] Lastly, we have the well-known case of the

Rattle-snake. He who has merely shaken the rattle of a dead snake,

can form no just idea of the sound produced by the living animal.

Professor Shaler states that it is indistinguishable from that

made by the male of a large Cicada (an Homopterous insect),

which inhabits the same district.[27] In the Zoological Gardens,

when the rattle-snakes and puff-adders were greatly excited at

the same time, I was much struck at the similarity of the sound

produced by them; and although that made by the rattle-snake is louder

and shriller than the hissing of the puff-adder, yet when standing

at some yards distance I could scarcely distinguish the two.

For whatever purpose the sound is produced by the one species, I can

hardly doubt that it serves for the same purpose in the other species;

and I conclude from the threatening gestures made at the same time

by many snakes, that their hissing,--the rattling of the rattle-snake

and of the tail of the Trigonocephalus,--the grating of the scales

of the Echis,--and the dilatation of the hood of the Cobra,--

all subserve the same end, namely, to make them appear terrible

to their enemies.[28]





[24] Mr. J. Mansel Weale, `Nature,' April 27, 1871, p.  508.



[25] `Journal of Researches during the Voyage of the "Beagle,"

' 1845, p.  96.  I have compared the rattling thus produced

with that of the Rattle-snake.



[26] See the account by Dr. Anderson, Proc.  Zool.  Soc.  1871, p.  196.



[27] The `American Naturalist,' Jan. 1872, p.  32.  I regret that I cannot

follow Prof. Shaler in believing that the rattle has been developed,

by the aid of natural selection, for the sake of producing sounds which

deceive and attract birds, so that they may serve as prey to the snake.



It seems at first a probable conclusion that venomous snakes,

such as the foregoing, from being already so well defended

by their poison-fangs, would never be attacked by any enemy;

and consequently would have





{note [27] continued} I do not, however, wish to doubt

that the sounds may occasionally subserve this end.

But the conclusion at which I have arrived, viz.  that the rattling

serves as a warning to would-be devourers, appears to me much

more probable, as it connects together various classes of facts.

If this snake had acquired its rattle and the habit of rattling,

for the sake of attracting prey, it does not seem probable that it

would have invariably used its instrument when angered or disturbed.

Prof. Shaler takes nearly the same view as I do of the manner

of development of the rattle; and I have always held this opinion

since observing the Trigonocephalus in South America.



[28] From the accounts lately collected, and given in the `Journal

of the Linnean Society,' by Airs.  Barber, on the habits of the snakes

of South Africa; and from the accounts published by several writers,

for instance by Lawson, of the rattle-snake in North America,--it does

not seem improbable that the terrific appearance of snakes and the sounds

produced by them, may likewise serve in procuring prey, by paralysing,

or as it is sometimes called fascinating, the smaller animals.

no need to excite additional terror.  But this is far from being the case,

for they are largely preyed on in all quarters of the world by many 
animals.

It is well known that pigs are employed in the United States

to clear districts infested with rattle-snakes, which they do most

effectually.[29] In England the hedgehog attacks and devours the viper.

In India, as I hear from Dr. Jerdon, several kinds of hawks, and at least

one mammal, the Herpestes, kill cobras and other venomous species;[30]

and so it is in South Africa.  Therefore it is by no means improbable

that any sounds or signs by which the venomous species could instantly

make themselves recognized as dangerous, would be of more service to them

than to the innocuous species which would not be able, if attacked,

to inflict any real injury.



Having said thus much about snakes, I am tempted to add a few remarks on

the means by which the rattle of the rattle-snake was probably developed.

Various animals, including some lizards, either curl or vibrate their

tails when excited.  This is the case with many kinds of snakes.[31]

In the Zoological Gardens, an innocuous species, the _Coronella Sayi_,

vibrates its tail so rapidly that it becomes almost invisible.

The Trigonocephalus, before alluded to, has the same habit;

and the extremity of its tail is a little enlarged, or ends in a bead.

In the Lachesis, which is so closely allied to the rattle-snake

that it was placed by Linnaeus in the same genus, the tail ends

in a single, large, lancet-shaped point or scale.  With some snakes

the skin, as Professor Shaler remarks, "is more imperfectly detached

from the region about the tail than at other parts of the body."

Now if we suppose that the end of the tail of some ancient American

species was enlarged, and was covered by a single large scale,

this could hardly have been cast off at the successive moults.

In this case it would have been permanently retained, and at each period

of growth, as the snake grew larger, a new scale, larger than the last,

would have been formed above it, and would likewise have been retained.

The foundation for the development of a rattle would thus have

been laid; and it would have been habitually used, if the species,

like so many others, vibrated its tail whenever it was irritated.

That the rattle has since been specially developed to serve as an

efficient sound-producing instrument, there can hardly be a doubt;

for even the vertebrae included within the extremity of the tail have

been altered in shape and cohere.  But there is no greater improbability

in various structures, such as the rattle of the rattle-snake,--

the lateral scales of the Echis,--the neck with the included ribs

of the Cobra,--and the whole body of the puff-adder,--having been

modified for the sake of warning and frightening away their enemies,

than in a bird, namely, the wonderful Secretary-hawk (_Gypogeranus_) having

had its whole frame modified for the sake of killing snakes with impunity.

It is highly probable, judging from what we have before seen,

that this bird would ruffle its feathers whenever it attacked a snake;

and it is certain that the Herpestes, when it eagerly rushes to attack

a snake, erects the hair all over its body, and especially that on its

tail.[32] We have also seen that some porcupines, when angered or alarmed

at the sight of a snake, rapidly vibrate their tails, thus producing

a peculiar sound by the striking together of the hollow quills.

So that here both the attackers and the attacked endeavour to make

themselves as dreadful as possible to each other; and both possess

for this purpose specialised means, which, oddly enough, are nearly

the same in some of these cases.  Finally we can see that if,

on the one hand, those individual snakes, which were best able

to frighten away their enemies, escaped best from being devoured;

and if, on the other hand, those individuals of the attacking

enemy survived in larger numbers which were the best fitted

for the dangerous task of killing and devouring venomous snakes;--

then in the one case as in the other, beneficial variations,

supposing the characters in question to vary, would commonly have been

preserved through the survival of the fittest.





[29] See the account by Dr. R. Brown, in Proc.  Zool.  Soc.  1871, p.  39.

He says that as soon as a pig sees a snake it rushes upon it; and a snake

makes off immediately on the appearance of a pig.



[30] Dr. Gunther remarks (`Reptiles of British India,' p.  340) on the

destruction of cobras by the ichneumon or herpestes, and whilst the cobras

are young by the jungle-fowl. It is well known that the peacock also

eagerly kills snakes.



[31] Prof. Cope enumerates a number of kinds in his `Method of Creation

of Organic Types,' read before the American Phil.  Soc., December 15th,

1871, p.  20.  Prof. Cope takes the same view as I do of the use

of the gestures and sounds made by snakes.  I briefly alluded to this

subject in the last edition of my `Origin of Species.'  Since the passages

in the text above have been printed, I have been pleased to find that

Mr. Henderson (`The American Naturalist,' May, 1872, p.  260) also takes

a similar view of the use of the rattle, namely "in preventing an attack

from being made."



_The Drawing back and pressure of the Ears to the Head_.--The ears

through their movements are highly expressive in many animals;

but in some, such as man, the higher apes, and many ruminants,

they fail in this respect.  A slight difference in position serves

to express in the plainest manner a different state of mind,

as we may daily see in the dog; but we are here concerned only with

the ears being drawn closely backwards and pressed to the head.

A savage frame of mind is thus shown, but only in the case of those

animals which fight with their teeth; and the care which they

take to prevent their ears being seized by their antagonists,

accounts for this position.  Consequently, through habit

and association, whenever they feel slightly savage, or pretend

in their play to be savage, their ears are drawn back.

That this is the true explanation may be inferred from the relation

which exists in very many animals between their manner of fighting

and the retraction of their ears.





[32] Mr. des Voeux, in Proc.  Zool.  Soc.  1871, p.  3.



All the Carnivora fight with their canine teeth, and all, as far

as I have observed, draw their ears back when feeling savage.

This may be continually seen with dogs when fighting in earnest,

and with puppies fighting in play.  The movement is different

from the falling down and slight drawing back of the ears,

when a dog feels pleased and is caressed by his master.

The retraction of the ears may likewise be seen in kittens

fighting together in their play, and in full-grown cats when

really savage, as before illustrated in fig.  9 (p. 58). Although

their ears are thus to a large extent protected, yet they often

get much torn in old male cats during their mutual battles.

The same movement is very striking in tigers, leopards,

&c., whilst growling over their food in menageries.

The lynx has remarkably long ears; and their retraction, when one

of these animals is approached in its cage, is very conspicuous,

and is eminently expressive of its savage disposition.

Even one of the Eared Seals, the _Otariapusilla_, which has

very small ears, draws them backwards, when it makes a savage

rush at the legs of its keeper.



When horses fight together they use their incisors for biting,

and their fore-legs for striking, much more than they do their hind-legs

for kicking backwards.  This has been observed when stallions have broken

loose and have fought together, and may likewise be inferred from the kind

of wounds which they inflict on each other.  Every one recognizes

the vicious appearance which the drawing back of the ears gives to a horse.

This movement is very different from that of listening to a sound behind.

If an ill-tempered horse in a stall is inclined to kick backwards, his ears

are retracted from habit, though he has no intention or power to bite.

But when a horse throws up both hind-legs in play, as when entering

an open field, or when just touched by the whip, he does not generally

depress his ears, for he does not then feel vicious.  Guanacoes fight

savagely with their teeth; and they must do so frequently, for I found

the hides of several which I shot in Patagonia deeply scored.  So do 
camels;

and both these animals, when savage, draw their ears closely backwards.

Guanacoes, as I have noticed, when not intending to bite, but merely to 
spit

their offensive saliva from a distance at an intruder, retract their ears.

Even the hippopotamus, when threatening with its widely-open enormous

mouth a comrade, draws back its small ears, just like a horse.



Now what a contrast is presented between the foregoing animals

and cattle, sheep, or goats, which never use their teeth in fighting,

and never draw back their ears when enraged!  Although sheep and goats

appear such placid animals, the males often join in furious contests.

As deer form a closely related family, and as I did not know that they

ever fought with their teeth, I was much surprised at the account given

by Major Ross King of the Moose-deer in Canada.  He says, when "two males

chance to meet, laying back their ears and gnashing their teeth together,

they rush at each other with appalling fury."[33] But Mr. Bartlett

informs me that some species of deer fight savagely with their teeth,

so that the drawing back of the ears by the moose accords with our rule.

Several kinds of kangaroos, kept in the Zoological Gardens, fight by

scratching with their fore-feet and by kicking with their hind-legs;

but they never bite each other, and the keepers have never seen

them draw back their ears when angered.  Rabbits fight chiefly

by kicking and scratching, but they likewise bite each other;

and I have known one to bite off half the tail of its antagonist.

At the commencement of their battles they lay back their ears,

but afterwards, as they bound over and kick each other, they keep

their ears erect, or move them much about.





[33] `The Sportsman and Naturalist in Canada,' 1866, p.  53.  p.  53.{sic}



Mr. Bartlett watched a wild boar quarrelling rather savagely with his sow;

and both had their mouths open and their ears drawn backwards.

But this does not appear to be a common action with domestic pigs

when quarrelling.  Boars fight together by striking upwards with their 
tusks;

and Mr. Bartlett doubts whether they then draw back their ears.

Elephants, which in like manner fight with their tusks, do not retract

their ears, but, on the contrary, erect them when rushing at each other

or at an enemy.



The rhinoceroses in the Zoological Gardens fight with their nasal horns,

and have never been seen to attempt biting each other except in play;

and the keepers are convinced that they do not draw back their ears,

like horses and dogs, when feeling savage.  The following statement,

therefore, by Sir S. Baker[34] is inexplicable, namely, that a rhinoceros,

which he shot in North Africa, "had no ears; they had been bitten

off close to the head by another of the same species while fighting;

and this mutilation is by no means uncommon."



Lastly, with respect to monkeys.  Some kinds, which have moveable ears,

and which fight with their teeth--for instance the _Cereopithecus ruber_--

draw back their ears when irritated just like dogs; and they then have

a very spiteful appearance.  Other kinds, as the _Inuus ecaudatus_,

apparently do not thus act.  Again, other kinds--and this is a great 
anomaly

in comparison with most other animals--retract their ears, show their 
teeth,

and jabber, when they are pleased by being caressed.  I observed this

in two or three species of Macacus, and in the _Cynopithecus niger_.

This expression, owing to our familiarity with dogs, would never be

recognized as one of joy or pleasure by those unacquainted with monkeys.





[34] `The Nile Tributaries of Abyssinia,' 1867, p.  443.





_Erection of the Ears_.--This movement requires hardly any notice.

All animals which have the power of freely moving their ears,

when they are startled, or when they closely observe any object,

direct their ears to the point towards which they are looking,

in order to hear any sound from this quarter.  At the same time

they generally raise their heads, as all their organs of sense

are there situated, and some of the smaller animals rise on their

hind-legs. Even those kinds which squat on the ground or instantly

flee away to avoid danger, generally act momentarily in this manner,

in order to ascertain the source and nature of the danger.

The head being raised, with erected ears and eyes directed forwards,

gives an unmistakable expression of close attention to any animal.

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