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 know that some animals, after being
domesticated, have acquired the habit of uttering sounds which were not
natural to them.[401] 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[402] 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.

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.”[403] 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.

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;[404] 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[405] that the monkeys (Cebus azaræ),
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,[406] 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.

“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[407]
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.

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 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.[408]
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.

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[409] 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[410]
that the Midas œdipus (belonging to the American division) when
excited erects its mane, in order, as he adds, to make itself as frightful
as possible.

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.[411] 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,[412] 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.”

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
pugnæ) 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[413] 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.”[414]
So do other kinds of owls. Hawks, as I am 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.

{illust. caption = FIG. 12—Hen driving away a dog from her chickens.
Drawn from life by Mr. Wood.}

{illust. caption = FIG. 13.—Swan driving away an intruder. Drawn
from life by Mr. Wood.}

Small birds, also, as I hear from Mr. Weir, such as various finches,
buntings and warblers, when angry, 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.[415]
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.[416]
But Dr. Günther 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,[417] 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[418]
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,[419]
that tickling a neighbouring part of the skin causes the erection and
protrusion of the hairs.

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.

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,[420]
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.

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,[421] 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. Günther 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. Günther informs me, it cannot swallow the frog,
which thus escapes being devoured.

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.”[422]

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.[423] This resemblance perhaps
serves as some protection to the Tropidonotus. Another innocuous species, the
Dasypeltis of South Africa, blows itself out, distends its neck, hisses and
darts at an intruder.[424] 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.[425] 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.[426] 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.[427]
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.[428]

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 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.[429]
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;[430] 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.[431]
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.[432]
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.

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.

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.”[433] 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.

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[434] 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.

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.