Чарльз Дарвин
The Expression of the Emotions in Man and Animals
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. 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.
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.
