A small snake with this pretence of a rattle is dangerous because it is so indistinctly heard.

This is also the case with Crotalus miliarius, whose rattle is so feeble as to be scarcely audible a few feet off.

So much for the size of rattles. Now for the development of them.

The theory that the rattle is the remains of cast-off cuticle, as some herpetologists have supposed, may be dismissed at once; for what would cause such vestiges to harden into a complicated and symmetrical form?

To Dumeril we owe some of our best conceptions of the growth of the rattle, which, whether it has or has not been evolved from the mere horny spine that terminates the tails of so many snakes, has certainly now an express provision for its production.

Like hair, claws, or nails, the rattle is horny matter excreted and hardened. In his Elementary Lessons in Physiology, Prof. Huxley shows us how in the growth of a nail new epidermic cells are added to the base, constraining it to move forward. ‘The nail, thus constantly receiving additions from below and from behind, slides forward over its bed and projects beyond the end of the finger.’ If the reader will look at his finger nail, and suppose the end bone of the Crotalus spine to be the ‘bed’ of the nail, he will to a certain extent be able to comprehend how the rattle grows out; but that the links become detached in succession is a phenomenon so astonishing and at the same time so difficult to comprehend, that few naturalists have ventured to state positively how this occurs. Conjecturally only and diffidently do I, therefore, presume to offer a supposition; and if my readers will once more pardon reference to human nails, and lend the aid of their imagination, they may be able to evolve a true theory out of my crude idea.

The young readers of Aunt Judy’s Magazine were also, a few years ago,[84] invited to lend the aid of their pink little finger nails to the illustrative development of a supposed rattle; and we will again imagine the whole tip of a finger to be covered with a round nail-cap, proceeding from the first joint, and to have grown so from birth. In growing out, this curious, cup-like nail, being never cut, would become hollow like a thimble. Pointed or tapering it would of course be, because, as the baby finger grew, the base or new portion of nail grew larger with it. We will also suppose that the joint whence the nail sprang was in constant activity, and so articulated that it could move with a quick and regular action or vibration; the hollow nail-cap, having attained a certain size, would become withered, and (as the constant bending of a piece of card or metal in time divides it) would be worn, and at length detached at its base. Meanwhile the growth of nail has not been arrested, but a new cap is forming within. The old, dry, and withered cap has now nothing to retain it, and would drop off, on account of its simple, conical form, like a loose-fitting thimble. But Dumeril explains to us that the terminal bones of the rattlesnake’s spine present a peculiar form, several of them coalescing.

‘Dans les Crotales cette extremitÉ de la queue, au lieu d’Être pointue, se trouve comme tronquÉe, et, par une bizarrerie que nous n’expliquons pas, il paraÎtrait que les trois derniÈres piÈces de la colonne vertÉbrale se seraient soudÉes entre elles, et comme aplaties pour composer un seul os triangulaire, avec trois bourrelets latÉraux simulant des restes d’apophyses transverses des vertÈbres, ainsi qu’on les voir souvent dans les trois derniÈres piÈces du coccyx chez l’homme. Cet os anormale a ÉtÉ dissÉquÉ chez un Crotale, on a reconnu qu’il est recouvert d’une sorte de matiÈre cartilagineuse dans laquelle aurait ÉtÉ secretÉe la substance cornÉe, comme un epiderme solide, qui conserve en effet extÉrieurement la forme de la piÈce osseuse, sur laquelle elle a ÉtÉ en quelque sorte moulÉe et qu’elle semble destinÉe ainsi À protÉger contre l’exfoliation, comme cela s’observe dans ceux des animaux ruminants dont la corne revÊt les chevilles osseuse du vÉritable coronal prolongÉ en pointe et devenu de cette faÇon une arme d’attaque, et surtout de defence.’[85]

Dumeril also tells us that the peculiar structure of those few terminal vertebrÆ, with their knobs or pads (‘bourrelets’) upon which the skin is moulded, tends to a movement lateral rather than up and down,—that quick action which we perceive when the rattle is being vibrated. Thus the horny covering takes the form of this bone with its lobes or bulges, which instead of permitting the supposed cup-like nail to fall off as in our finger illustration, causes the links as they are pushed out to hang or cling together; and we can only suppose that the constant action loosens, and not only loosens when dead or detached, but loosens, that is to say, enlarges, the link while growing. For if you examine the spine of a skeleton Crotalus and the rattle that grew upon that spine, you will perceive that the links are a great deal larger than the ‘piÈce osseuse sur laquelle elle a ÉtÉ en quelque sorte moulÉe.’

There is one other peculiarity observable in a detached rattle, which I cannot pretend to explain in any way. If you hold one up by its base or largest link, you will find it invariably hangs in a slight curve and not perpendicularly. You can straighten it, but you will not be able to curve it in the opposite direction, proving that it naturally inclines one way, whether to the right or the left of the animal while living, I cannot assert. But it is a curious feature, and one that can no doubt be accounted for by scientific observers. Thus, as in the illustration below, you can curve a rattle so as to discern the interior links on one side, but not on the other. I have made the attempt with many rattles, but always with the same result. The centre fig. below is a section.

Not the least important of all the speculations to which the rattling tail has given rise, is the question, ‘Of what use is it?’ for we know that nothing exists in vain. Apart from the fact that the American savages make some medicinal use of the rattle, this elaborated, curious, and not unsightly instrument has as yet had no special and determined office assigned to it to the advantage of its possessor, though theories regarding it are numerous.

Formerly, when only the dangerous powers of the reptile were understood, it was sufficient to say of it in a tone of pious thankfulness, that the Almighty had so armed this serpent as a warning to its enemies. Some of those early writers introduce the rattlesnake to us as the most benevolent and disinterested of dumb animals, conscientiously living up to his duties, obedient to that ‘peculiar Providence’ which has given him a rattle ‘to warn the inadvertent intruder of danger.’ ‘He maketh such a noise that he catcheth very few,’ an evidence of imprudence wholly inconsistent with his inherited ‘wisdom.’ Indeed, between the character given of this ‘superb reptile’ by Chateaubriand, and the self-sacrificing qualities assigned it by some other writers, we can only wonder how a hungry rattlesnake ever managed to survive at all, and how it is that the race is not extinct long ago.

That the early and unscientific travellers, speaking from a thankful experience of having escaped a rattlesnake through hearing where it was, should seek no further for the utility of the rattle, is not much to be wondered at. But so lately as 1871 one of our popular physiologists, whose work is a textbook, has expatiated on this theme so positively that it is necessary to quote his words on this ‘admirable provision of nature,’ which apparently has elaborated a unique appendage for the purpose of starving its proprietor!

‘The intention of this organ is so obvious, that the most obtuse cannot contemplate it without at once appreciating the beauty of the contrivance.... It (the snake) announces the place of its concealment, even when at rest, to caution the inadvertent intruder against too near an approach.’[86]

If all the venomous serpents were thus beneficently armed (the cobras of India especially), the crusade against snakes would be at an end, or never need have been instituted; for supposing the heedless loiterer to have been a bird, squirrel, guinea-pig, or any of the lesser mammalia which form the food of most snakes, these happy creatures would have had the world to themselves long ago, while vipers had kindly starved themselves out of all traces.

‘Every creature of God is good,’ we must repeat and ponder over. Even a deadly rattlesnake, and every part of that rattlesnake, has its appointed use.

The ‘inadvertence’ (in this instance on the part of the writer who thus expressed himself) has not been without its use as well, for a more careful attention has been given to the rattle in consequence; and much controversy has since arisen among some of the ablest herpetologists, particularly in America, where much that was new and suggestive soon found its way into the scientific journals.

Briefly to summarize some of the arguments, I will repeat a few of them as suggested by some well-known naturalists. In that able periodical, the American Naturalist, vol. vi. 1872, the subject was thoroughly discussed. Professor Shaler, in a paper on ‘The Rattlesnake and Natural Selection,’ admitted that whereas he had hitherto thought and taught that the rattle did more harm than good to its owner, he now knew that the sound is so similar to that of the stridulating insects upon which some birds feed, that he had no doubt of its use in attracting these to the snake. He himself had mistaken the sound for a locust. ‘Does it invite its enemies or entice its prey?’ he asks. ‘Those snakes that can best attract birds, are best fed.’ In reply to this, a Mr. J. W. Beal of Michigan affirmed that he had often mistaken the sound for grasshoppers; which educed many similar accounts from persons who had been in danger of treading on a Crotalus through ‘inadvertent approach,’ supposing that only an insect were there. A child had taken it for a cicada, some one else for a locust, etc. Any one who is acquainted with the wild parts of the American Continent, is familiar with the ceaseless chirps and whizzings of those ubiquitous insects which are furnished with the stridulating apparatus, and which lead you almost to expect to see a scissors-grinder behind every tree. These are all the more deceptive on account of their varying cadences, now louder, now softer, approaching or receding, just as the sound of the rattle varies by increased or less rapid vibrations, or according to its individual size and strength. In a paper read before the Zoological Society by Mr. A. R. Wallace in 1871, he invited attention to this fact of the resemblance between the sound of the rattle and the singing of a cricket, and that its use seemed to be to decoy insectivorous animals.

Dr. Elliott Coues is also of this opinion, viz. that to an unpractised ear the sound cannot be distinguished from the crepitation of the large Western grasshopper. A case has been reported, he tells us, of a bird observed to be drawn within reach, thinking it was a grasshopper. Dr. Coues also affirms that the sound has been heard when no perceptible irritation disturbed the snake.[87]

Thus we see that the ‘inadvertent intruder,’ so far from being warned away, is beguiled to his injury, both in the case of human beings not quick to discriminate sounds, or not having rattlesnakes in their minds, and with animals in their early experience who perhaps hear one for the first time.

Another question is, ‘Does the snake sound its rattles when seeking to capture prey?’

The editor of the American Naturalist in the volume already quoted, thinks they do not systematically set up a rattling for this purpose; and as far as observation of snakes in confinement can be of use, this opinion may be confirmed. Probably a captive snake may have learned by experience that, hungry or not, it must wait for its periodical dinner, and that its ‘dinner bell’ avails it nothing. Nevertheless, we do not find that the snake uses its rattle upon food being placed in its cage, unless the rat or the guinea-pig come tumbling unexpectedly or unceremoniously upon the snake, when it would sound its rattle in alarm; but it waits quietly, silently, rather receding than advancing towards the destined prey, and then, after cautious observation, stealthily approaching to give the fatal bite. Mr. Arthur Nicols, author of Zoological Notes, etc., has there discussed this point, but dismisses it by declaring he has no faith in ‘the dinner-bell theory.’[88]

Nor can the rattle be designed to terrify enemies or as a menace, since the sound would invite the attack of those very animals which the snake has most cause to fear, namely goats, hogs, and the large carnivorous birds that devour it. If, besides, it were used as a warning, why have the young ones, which are more in need of protection, no rattle?

Darwin, in the sixth edition of his Origin of Species, 1872, writes as follows, p. 162:—

‘It is admitted that the rattlesnake has a poison-fang for its own defence and for the destruction of its prey; but some authors suppose that at the same time it is furnished with a rattle for its own injury, namely to warn its prey. I would almost as soon believe that the cat curls the end of its tail when preparing to spring in order to warn the doomed mouse. It is a much more probable view that the rattlesnake uses its rattle, the cobra expands its frill, and the puffadder swells whilst hissing so loudly and harshly, in order to alarm the many birds and beasts which are known to attack even the most venomous species. Snakes act on the same principle which makes a hen ruffle her feathers and expand her wings when a dog approaches her chickens.’ This profound thinker, then, is one of those who include the rattle among ‘the many ways by which animals endeavour to frighten away their enemies.’

We may reasonably conclude that the Crotalus, in common with other snakes, also with dogs and cats, expresses a variety of feelings with its sounding tail, fear being the most predominant one. The Indians recognise its utility as a warning by gratefully abstaining from killing one that rattles. They superstitiously regard it as protective to themselves if not to the snake, and they in turn carefully protect the reptile. Backwoodsmen display little or no fear when they hear the Crotalus, and though they do not spare it, regard it with less bitter animosity than they display towards its cousin the Copper-head; because, as a facetious writer has testified of it, ‘it never bites without provocation, living up to the laws of honour, and by his rattles giving challenge in an honourable way.’

That the sound has a language of its own is known by the fact that when disturbed and one rattle is sprung, all other rattlesnakes within hearing take up the chorus. That the sexes also understand each other through crotaline eloquence is generally believed. In fact, to each other and to themselves they have, no doubt, as many variations in the use of their rattles, as any other animal in the expression of its tail; and probably all the above enumerated examples are at one time or another its legitimate uses. Those who have most closely observed them have detected a variety of cadences in one and the same rattle.

Those also who have carefully watched rattlesnakes under various circumstances, must perceive that timidity is one of the strongest features in this reptile. In chap. xxx. I will give examples of this. Already convinced by observation, I attributed to excessive timidity the chief agitation of the rattle, when writing on the Ophidia in the Dublin University Magazine, December 1875, and again in Aunt Judy’s Magazine, July 1877. Fear causes some snakes to puff themselves; others to expand or flatten the body; fear excites the cobra to erect its anterior ribs and display its ‘hood;’ and, above all, fear causes most snakes to hiss. Fear is coupled with anger, in these attempts to do their best towards repelling the offender. Dr. E. Coues, in speaking of the rattle, supposes it to have possibly ‘resulted in the course of time from the continual agitation of the caudal extremity of these highly nervous and irritable creatures.’ Dr. Weir Mitchell has known captive snakes to vibrate the rattle for hours at a time; and probably, if there were opportunities of becoming more intimately acquainted with crotaline idiosyncrasies, we should discover some snakes to be more or less afflicted with temper, nervousness, terror, or other emotions which induce an animal to express its feelings in its own way.

But the most remarkable peculiarity in this snake is that no other way is in its power: a rattlesnake never hisses. Throughout the numerous arguments, theories, explanations, and suggestions, there is such an absence of allusion to this fact that we must suppose it to be very little known. Says Dumeril in describing les petits Étuis cornÉs, comparÉ À celui que feraient plusieurs grelots peu sonorÉs: ‘Les Crotales diffÈrent de tous les autres serpents connus par la facultÉ qu’ils ont de produire des sons sourds et rapides, cu plutÔt des bruits continus et prolongÉs À l’aide d’un organe spÉcial, qui suplÉerait—pour ainsi dire—À la voix, dont ces serpents sont toujours privÉs.’[89] But the sibilations of the rattle are often so like hissing that they have been compared to the whistling of wind among the leaves, to the escape of water through a pipe, to the whizzing of insects, the rattling of seed pods, and many similar sounds, showing at the same time the character of the noise and its variability.

Concisely recapitulating what this rattle does, we understand that in the first place it is a substitute for the voice—so far as hissing can be called voice; and that what would cause other excessively nervous, timid, terrified snakes to hiss, causes the rattle to vibrate. It may attract insectivorous birds; it may alarm other timid creatures; it may summon its mate; and, as is well known, it has sympathy with its mate; for a second rattle is almost sure to be sounded, and they have been observed to sound in pairs or numbers responsively—it may be to express anger, fear, and for aught we know pleasure, in a state of liberty and enjoyment, feelings expressed by the tail of other creatures.

Why it is formed as it is, so wholly different from all other tails; from what it has been evolved; and how long in evolving,—all these are problems to be solved by future Darwins and future Evolutionists.

This chapter, therefore, closes with only feeble speculations after feeble attempts to explain an inexplicable phenomenon. The simplest and truest solution seems to be found in those few words, ‘qui suplÉerait À la voix, dont ces serpents sont toujours privÉs.’

Again, we wonder whether in the non-hissing serpents any peculiarity of trachea may be observed.