"But now," says Ruskin, "here's the first thing, it seems to me, we've got to ask the scientific peoplewhat use a serpent has for its tongue; since it neither works it to talk with, or taste with, or hiss with, nor, as far as I know, to lick with, and, least of all, to sting withand yet, for people who do not know the creature, the little vibrating forked thread, flicked out of its mouth and back again, as quick as lightning, is the most striking part of the beast; but what is the use of it ? Nearly every creature but a snake can do some sort of mischief with its tongue. A woman worries with it, a chameleon catches flies with it, a cat steals milk with it, a pholas digs holes in the rock with it, and a gnat digs holes in us with it; but the poor snake cannot do any manner of harm with it whatsoever; and what is his tongue forked for?"
The writer's manner in this paragraph, and the unexpectedness of the mocking question that leaps out at the end, suggest the idea that there are, in man, two sorts of forked tongues, and that one sort is not worked for mischief. Certainly few of these "vibrating forked threads" in literature have flickered more startlingly, like forked lightning, and to the purpose, than Ruskin's own. The passage is admirable, both in form and essence; it shines even in that brilliant lecture on Living Waves from which it is taken, and where there are very many fine things, along with others indifferent, and a few that are bad. But there is this fault to be found with it: after putting his question to the "scientific people," the questioner assumes that no answer is possible; that the stinging and hissing and licking theories having been discarded, the serpent's tongue can do no manner of mischief, and is quite useless. A most improbable conclusion, since the fact stares us in the face that the serpent does use its tongue; for instance, it exserts and makes it vibrate rapidly, but why it does so remains to be known. It is true that in the long life of a species an organ does sometimes lose its use without dwindling away, but persists as a mere idle appendage: it is, however, very unlikely that this has happened in the case of the serpent's tongue; the excitability and extreme activity at times of that organ rather incline one to the opinion that it has only changed its original use for a new one, as has happened in the case of some of the creatures mentioned in the passage quoted above.
"A chameleon," says Ruskin, "catches flies with its tongue," inferring that the snake has no such accomplishment. Yet the contrary has been often maintained. "The principal use of the tongue," says Lacépède in his Natural History of Serpents, "is to catch insects, which it catches by means of its double tongue." This notion about the use of the double tongue is quite common among the older ophiologists, and, along with it, the belief that snakes prey chiefly on insects. And here I cannot resist the temptation to quote a few more words touching on this point from Lacépèdea very perfect example of the teleological spirit in science which flourished a century ago, and made things easy for the naturalist. "We are not," he says, "to be amazed at the vast number of serpents, both species and individuals, which inhabit the intertropical countries. There they find the degree of warmth which seems congenial to their natures, and the smaller species find abundance of insects to serve them for food. In those torrid regions, where Nature has produced an infinite multitude of insects and worms, she has likewise produced the greatest number of serpents to destroy the worms and insects; which otherwise would multiply so exceedingly as to destroy all vegetable productions, and to reduce the most fertile regions of the earth into barren deserts, inaccessible to man and animals; nay, even these noxious and troublesome insects would be finally obliged to destroy each other, and nothing would remain but their mangled limbs."
Here the French naturalist pauses, aghast at the frightful picture of desolation he has himself conjured up.
When enumerating the uses to which a serpent does not put its tongue, Ruskin might very well have said that it is not used as a tactile organ. That it is a tactile organ is a very modern suppositiona small hypothesis about a small matter, but with a curious and rather amusing history. It was in the first place given out merely as a conjecture, but no sooner given than accepted as an irrefragable fact by some of the greatest authorities among us. Thus Dr. Günther, in his article on snakes in the Encyclopædia Britannica, ninth edition, says, "The tongue is exserted for the purpose of feeling some object, and sometimes under the influence of anger or fear."
Doubtless those who invented this use for the organ were misled by observing snakes in captivity, in the glass cases or cages in which it is usual to keep them; observing them in such conditions, it was easy to fall into the mistake, since the serpent, when moving, is frequently seen to thrust his tongue against the obstructing glass. It should be remembered that glass is glass, a substance that does not exist in nature; that a long and sometimes painful experience is necessary before even the most intelligent among the lower animals are brought to understand its character; and, finally, that the delicate, sensitive tongue comes against it for the same reason that the fly buzzes and the confined wild bird dashes itself against it in their efforts to escape. In a state of nature when the snake is approached, whether by its prey or by some large animal, the tongue is obtruded; again, when it is cautiously progressing through the herbage, even when unalarmed, the tongue is exserted at frequent intervals; but I can say, after a long experience of snakes, that the exserted organ never touches earth, or rock, or leaf, or anything whatsoever, consequently that it is not a tactile organ.
Another suggestion, less improbable on the face of it than the one just cited, is that the tongue, without touching anything, may, in some way not yet known to us, serve as an organ of intelligence. The serpent's senses are defective; now when, in the presence of a strange object or animal, the creature protrudes its long slender tonguenot to feel the object, as has been showndoes it not do so to test the air, to catch an emanation from the object which might in some unknown way convey to the brain its character, whether animate or inanimate, cold or warm blooded, bird, beast, or reptile, also its size, etc.? The structure of the organ itself does not give support to this supposition; it could not taste an emanation without some such organs as are found in the wonderfully formed antennae of insects, and with these it is not provided.
Only by means of a sensitiveness to air waves and vibrations from other living bodies near it, in degree infinitely more delicate than that of the bat's wingthe so-called sixth sense of that animalcould the serpent's tongue serve as an organ of intelligence. Here, again, the structure of the tongue is against such an hypothesis; and if the structure were different it would only remain to be said that the instrument performs its work very badly.
Another explanation which has been put forward by two well-known writers on serpent life, Dr. Stradling and Miss Hopley, remains to be noticed. These observers came independently to the conclusion that the snake makes use of his tongue as a decoy to attract its prey.
In the case of one of these writers, the idea was suggested by an incident in our Zoological Gardens. A fowl was placed in a boa's cage to be eaten, and immediately began hunting about for food on the floor of the cage; the serpentapparently seen merely as an inanimate objectprotruded its tongue, whereupon the fowl rushed and pecked at it, mistaking it for a wriggling worm. Such a thing could not well happen in a state of nature. The tongue may resemble a wriggling worm, or, when vibrated very quickly, a fluttering moth; but we cannot assume that the serpent, however motionless it may lie, however in its colour and pattern it may assimilate to its surroundings, is not recognised as a separate and living thing by a bird or any other wild animal.
From the foregoing it will be seen that so far from being silent on this subject, as Ruskin imagined, the "scientific people" have found out or invented a variety of uses for the serpent's tongue. By turns it has been spoken of as an insect-catching organ, a decoy, a tactile organ, and, in some mysterious way, an organ of intelligence. And, after all, it is none of these things, and the way is still open for fresh speculation.
I have on numberless occasions observed the common pit-viper of southern South America, which is of a sluggish disposition, lying in the sun on a bed of sand or dry grass, coiled or extended at full length. Invariably, on approaching a snake of this kind, I have seen the tongue exserted; that nimble, glistening organ was the first, and for some time the only sign of life or wakefulness in the motionless creature; If I stood still at a distance of some yards to watch it, the tongue would be exserted again at intervals; if I moved nearer, or lifted my arms, or made any movement, the intervals would be shorter and the vibrations more rapid, and still the creature would not move. Only when I drew very near would other signs of excitement follow. At such times the tongue has scarcely seemed to me the "mute forked flash" that Ruskin calls it, but a tongue that said something, which, although not audible, was clearly understood and easy to translate into words. What it said or appeared to say was: "I am not dead nor sleeping, and I do not wish to be disturbed, much less trodden upon; keep your distance, for your own good as well as for mine." In other words, the tongue was obtruded and vibrated with a warning purpose.
Doubtless every venomous serpent of sluggish habits has more ways than one of making itself conspicuous to and warning off any large heavy animal that might injure by passing over and treading on it; and I think that in ophidians of this temper the tongue has become, incidentally, a warning organ. Small as it is, its obtrusion is the first of a series of warning motions, and may therefore be considered advantageous to the animal; and, in spite of its smallness, I believe that in very many instances it accomplishes its purpose without the aid of those larger and violent movements and actions resorted to when the danger becomes pressing.
All large animals, including man, when walking on an open space, see the ground before them, with every object on it, even when the head is raised and when the animal's attention is principally directed to something in the distance. The motions of the legs, the exact measurement of every slight obstruction and object in the wayhillocks, depressions in the soil, stones, pebbles, sticks, etc.are almost automatic; the puma may have nothing but his farseen quarry in his mind, and the philosopher be thinking only of the stars, as they move, both quite unconscious of what their feet are doing; but the ground must be seen all the same, otherwise they could not go smoothly even over a comparatively smooth surface.
When the man or other animal progressing in this ordinary way comes to where a serpent, with a protective or assimilative colour and appearance, lies motionless in the path, he certainly sees it, but without distinguishing it as a serpent. The varicoloured surface it rests on and with which it is in harmony is motionless, consequently without animal life and safe to tread ona rough flooring composed of mould, pebbles and sand, dead and green herbage, withered leaves, twisted vines, and sticks warped by the sun, brown and grey and mottled. But if the smallest thing moves on that still surface, if a blade trembles, or a minute insect flutters or flies up, the vision is instantly attracted to the spot and concentrated on a small area, and as by a flash every object on it is clearly seen, and its character recognised. Those who have been accustomed to walk much in dry, open places, in districts where snakes are abundant, have often marvelled at the instantaneous manner in which something that had been previously seen as a mere strip or patch of dull colour on the mottled earth, as a part of its indeterminate pattern, has taken the serpent form. And when once it has been recognised as a serpent it is seen so vividly and in such sharp contrast to its surroundings as to appear the most conspicuous and unmistakable object in nature. Why, in such cases, they ask in astonishment, did they not recognise its character sooner? I believe that in such cases it is the suddenly exserted, glistening, vibrating tongue that first attracts the eye to the dangerous spot and reveals the serpent to the mind.
This warning character is, I believe, as has already been intimated, an incidental use of the tongue, probably confined, or at all events most advantageous, to the vipers and to other venomous serpents of lethargic habits. In the case of the extremely active, nonvenomous snake, that glides away into hiding on the slightest alarm, the tongue would be of little use or no value as a warning organ. Between a snake of this kind and the slumberous pit-viper the difference in habit is extreme. But at bottom, all ground snakes are alike in dispositionall hate to be disturbed, and move only when necessity drives; and we can imagine that when the tremendous weapon of a lethal tooth had been acquired, when experience began to teach the larger mammalians to view the serpentine form with suspicion and to avoid it, the use of the tongue as a warning would react on the serpent, making it more and more lethargic in habitas inactive, in fact, as every snake loves to be.
There is, I imagine, another and more important use of the tongue, older than its warning use, although this may date back in time to the Miocene period, when the viperine form existeda use of the tongue common to all ophidians that possess the habit of exserting and vibrating that organ when excited. The subject is somewhat complicated, for we have not only to consider the tongue, but the whole creature of which the tongue is so small a part; its singularity and anomalous position in nature, and the many and diverse ways in which the animals it preys on are affected by its appearance. Furthermore, I have now in my mind two separate functions, the first of which occasionally, perhaps often, passes into and becomes one with the other.
When the common or ring snake pursues a frog, the chase would in most cases prove a very vain one but for that fatal weakness in the hunted animal, which quickly brings its superior activity to naught. The snake need not even be seen for the effect to be produced, as anyone can prove for himself by pushing his walking-stick, snake-wise, through the grass and causing it to follow up the frog's motions, whereupon, after some futile efforts to escape, the creature collapses, and stretching out its fore-feet like arms that implore mercy, emits a series of piteous, wailing screams. Thus, all that is necessary for this end to be reached is that the frog should be conscious of something, no matter what, pushing after it through the grass. There is here, apart from the question in animal psychology, a little mystery involved; for how comes it that in the course of the countless generations during which the snake has preyed on the frog, this peculiar weakness has not been eliminated by means of the continual destruction of the individuals most subject to it, and, on the other hand, the preservation of all those possessing it in a less degree, or not at all? It is hard for a good Darwinian to believe that the frog is excessively prolific for the snake's advantage rather than for its own. But this question need not detain us; there are vulnerable spots and weak joints in the defensive armour of all animals. What I wish to draw attention to is the fact that, speaking metaphorically, the serpent, of all creatures that kill their own meat, is the most unsportsmanlike in its methods, that it has found out and subtly taken advantage of the most secret and unsuspected weaknesses of the animals on which it preys.
We have seen how the common snake catches the frog; but frogs are found only in wet places, and snakes abound everywhere, and the sedentary snake of the dry uplands must feed on the nimble rodent, volatile bird, and elusive lizard. How does he manage to catch them? For considering how alert and quick-sighted these small hunted creatures are, it must, I think, be assumed that the snake cannot, except in rare instances, approach them unseen and take them unawares. I believe that in many cases the snake succeeds by approaching its intended victim while appearing to be stationary. This stratagem is not confined to the ophidians: in a somewhat different form it is found in a great variety of animals. Perhaps the most familiar example is afforded by the widely distributed hunting-spider. The plan followed by this spider, on a smooth surface where it cannot hide its form, is to advance boldly towards its prey, and when the fly, who has been suspiciously watching its approach, is about to dart away, to become motionless. This appears to excite the fly's curiosity, and he does not take flight; but very soon his restive spirit returns, he moves about this way and that, to see all round him, and each time he turns his bright eyes away the spider rapidly moves a little nearer; but when the fly looks again, appears motionless as before. In this way, little by little, the space is lessened, and yet the fly, still turning at intervals to regard the suspicious-looking object, does not make his escape, simply because he does not know that the space has been lessened. Seeing the spider always motionless the illusion is produced that it has not moved: the dividing distance has been accurately measured once for all, and no second act of judgment is required; the fly, knowing his own quickness and volatile powers, feels himself perfectly safe; and this goes on until by chance he detects the motion and instantly flies away, or else fails to detect it and is caught. Cats often succeed in capturing birds by a similar stratagem.
The snake, unlike the spider and cat, cannot make the final spring and rush, but must glide up to within striking distance: this he is able to do by means of the faculty he possesses of progressing so gradually and evenly as to appear almost motionless; the tongue which he exserts and rapidly vibrates at intervals when approaching his victim helps in producing the deception.
Long observation has convinced me that a snake on the ground, moving or resting, is not a sight that violently excites birds, as they are excited by the appearance of a fox, cat, weasel, hawk, or any other creature whose enmity is well known to them. I have frequently seen little birds running about and feeding on the ground within a few feet of a snake lying conspicuously in their sight; furthermore, I have been convinced on such occasions that the birds knew the snake was there, having observed them raise their heads at intervals, regard the reptile for a few moments attentively, then go on seeking food. This shows that birds do sometimes come near snakes and see them with little or no fear, but probably with some slight suspicion and a great deal of curiosity, on account of the singularity of their appearance, their resemblance to vegetable rather than to animal forms of life, and, above all, to their strange manner of progression. Now the bird, or lizard, or small mammal, thus brought by chance near to a hungry, watchful snake, once it begins to regard the snake curiously, is in imminent danger of destruction in one of two ways, or by a combination of both: in the first case it may be deluded as to the distance of the suspicious-looking object and in the end seized, just as the fly is seized by the Salticus spider, before it can make its escape; secondly, it may, while regarding its singular enemy, be thrown into a trance or convulsive fit and so rendered powerless to escape, or it may even be moved to cast itself into the open jaws of the snake. In either case, the serpent's tongue would, I believe, play a very important part. In a case of the first kind the snake would approach its intended victim so slowly and continuously as almost to appear not to be moving; still, in most cases the movement probably would be detected but for the tongue, which attracts the eye by its eccentric motions, its sudden successive appearances and disappearances; watching the tongue, the long, sinuous body slowly gliding over the intervening space would not be observed; only the statuesque raised head and neck would be visible, and these would appear not to move. The snake's action in such a case would resemble the photographer's trick to make a restive child sit still while its picture is being taken by directing its attention to some curious object, or by causing a pocket-handkerchief to flutter above the camera.
Snakes have been observed to steal upon their victims in this quiet, subtle manner; the victim, bird or lizard, has been observed to continue motionless in a watchful attitude, as if ready to dart away, but still attentively regarding the gradually approaching head and flickering tongue; and in the end, by a sudden, quick-darting motion on the part of the snake, the capture has been effected. Cases of this description are usually set down to "fascination," which I think is a mistake.
Fascination is a fine old word, which has done good service and has had a long day and happily outlived its evil repute: but it had its faults at the best of times; it originally expressed things purely human, and therefore did not exactly fit things serpentine, and was, to some extent, misleading. What its future historyin sciencewill be cannot be guessed. In France it has been used to describe a mild form of hypnotism induced by the contemplation of a bright spot, and no doubt there would be a certain propriety in applying the word to the soothing somnolent effect produced on the human subject by the revolving mirror invented by Dr. Luys. But this is not the form we are concerned with. Fascination in serpent life is something very different; in the present state of knowledge on the subject the old word cannot be discarded. We are now in possession of a very large number of well-authenticated cases of undoubted fascination in which the victims are seen to act in a variety of ways, but all alike exhibit very keen distress. The animal that falls under the spell appears to be conscious of his loss of power, as in the case of the frog pursued by the ring-snake. He is thrown into violent convulsions, or trembles, or screams, or struggles to escape, and sometimes rushes in terror away only to return again, perhaps in the end to jump into the serpent's jaws. A brother of mine once observed a pipit running with flutterings round and round a coiled snake, uttering distressed chirps and cries; the snake, vibrating its tongue, moved its head round to follow the motions of the bird. This is a common formthe desire and vain striving to escape. But when an animal is seen to remain motionless, showing no signs of distress or fear, attentively regarding the gradually approaching snake, such a case cannot, I think, be safely set down to fascination, nor to anything more out of the common than curiosity, and, as in the case of the volatile, sprightly fly and terrestrial spider, to the illusion produced in the victim's mind that the suspicious-looking object is stationary.
Concerning the use, here suggested, of the tongue in fascination, I can scarcely expect that those whose knowledge of the snake is derived from books, from specimens in museums, and from seeing the animal alive in confinement, will regard it as anything more than an improbable supposition, unsupported by facts. But to those who have attentively observed the creature in a state of nature, and have been drawn to it by, and wondered at, its strangeness, the explanation, I venture to think, will not seem improbable. To weigh, count, measure, and dissect for purposes of identification, classification, and what not, and to search in bones and tissues for hidden affinities, it is necessary to see closely; but this close seeing would be out of place and a hindrance in other lines of inquiry. To know the creature, undivested of life or liberty or of anything belonging to it, it must be seen with an atmosphere, in the midst of the nature in which it harmoniously moves and has its being, and the image it casts on the observer's retina and mind must be identical with its image in the eye and mind of the other wild creatures that share the earth with it. It is not here maintained that the tongue is everything, nor that it is the principal agent in fascination, but only that it is a necessary part of the creature, and of the creature's strangeness, which is able to produce so great and wonderful an effect. The long, limbless body, lithely and mysteriously gliding on the surface; the glittering scales and curious mottlings, bright or lurid; the statuesque, arrowy head, sharp-cut and immovable; the round lidless eyes, fixed and brilliant; and the long, bifurcated tongue, shining black or crimson, with its fantastic flickering play before the close-shut, lipless mouththat is the serpent, and probably no single detail in the fateful creature's appearance could be omitted and the effect of its presence on other animals be the same.
When, years ago, I had finished writing the above paper, which appeared later in the Fortnightly Review, I made the following entry in my diary, and reproduce it here just to show that I am not apt to set too high a value on my own theory.
This paper was not too long, but I'm glad it's finished and done with. Not because the subject didn't interest meon the contrary, it had a tremendous attraction for mebut because, having written it, a difficulty has been removed, a pain relieved, a want satisfied. True that I've only imagined this use for a serpent's tongue, and that it may not be the true use if any use there be; but if we have a need to build, and there is any wind or cloud to build on, 'tis best to go on bravely with the building business. Who cares if the structure is all to tumble down again? Not I. Nevertheless the mere building is a pleasure, and the completion of the structure a satisfaction in that it puts something where before there was nothing. The speculative soul which is in man abhors the desert, vacant spaces and waters and islands of nothingness. Thus, to illustrate this little thing by a big thingthe little flickering tongue of the serpent by something so big that it fills the entire universethe existence of an ethereal medium is possibly no more than a figment of the mind, an invention to get us out of a difficulty, or a "purely hypothetical supposition," as was boldly said by one of our greatest physicists. At all events, a lady lean and pale who came at our call, tottering forth wrapped in a gauzy veilsurely the most attenuated and shadowy of all the daughters of Old Father Speculation. But having got her in our arms, thin and pale though she be, we imagine her beautiful and love her dearly, and rest satisfied with the breasts of her consolations, albeit they are of no more substance than thistledown.