THE INTEGUMENT—‘HORNS,’ AND OTHER EPIDERMAL APPENDAGES. HAVING decided that in animal organization nothing exists without its especial use; assuming also that the peculiar development of cuticle forming the rattle is to supply the deficiency of voice, we are next induced to examine those other appendages in serpents which are also modifications of the integument, such as the ‘horns’ of the Cerastes, the tentacles, snout-protuberances, and developments occasionally seen about the head of snakes, and which have all, no doubt, their uses. ‘Serpents are naked,’ says GÜnther—that is, they have no separate epidermal productions in the way of fur, feathers, hair, or wool, and all the variations of form in scales are but the folds of the epidermis. The heads of most snakes are covered with non-imbricated plates or shields. The form and position of these shields are in a great measure used in classification; ‘are of the greatest Ophiologists differ slightly in distinguishing them as regards assigning the exact position of some of the shields, which, like all other ophidian features, vary in closely allied species. As, for example, while one naturalist may decide that a certain shield is exactly over the eye, another may consider it somewhat to the right or the left. GÜnther’s classification being the one now generally adopted, I copy the names assigned by him, and the diagrams given in his work. It will be observed that some of these shields can be seen both in the profile and the others as well; as, for instance, the Ophiologists in deciding species, etc., enumerate those which are more than a pair as ‘upper labials’ so many, ‘lower labials’ so many. In some snakes these shields are so large as to cover nearly the entire head; in others, they are almost inconspicuously small, or absent altogether, and much varied, as we shall see. In the vipers the head is generally covered with small, rigid, imbricated, or overlapping scales instead of plates, and in some the scales are so extremely fine and closely arranged as almost to represent short bristles. This is noticeable in the African ‘nose-horned viper’ (Vipera nasicornis), p. 322, where they present a curiously complicated structure.
Too minute to examine except under the magnifying-glass, or to attempt to illustrate, we can convey only a general idea of these curious viper scales, which to the touch are spinous, and rough as a coarse brush. They must form an unpleasant perch for a bird, if it be true that the latter is enticed by the horns of some vipers to come and peck at them, as at a worm. These rigid head-scales become gradually larger and more simple on the body, but are still comparatively small for so large a serpent. In some few of the viperine snakes, plates are present as well as the fine scales, though chiefly Fig. a. One of the Indian CrotalidÆ. It has two conspicuous supraciliary shields, two equally conspicuous anterior frontals over the nostril. The rest are small, and those on the top are absent altogether. The scales are all finely carinated. Fig. b. The head of a Colubrine snake in which the same scales appear as those in Fig. 1 of the preceding page, viz. two orbitals, etc., but are all much smaller, and do not therefore more than half cover the head. Fig. c. The head of a sea snake, which as to design is really pretty, and, as GÜnther affirms, so different from land snakes in respect to head shields, that without any further investigation an ophiologist can at once distinguish the hydrophidÆ. Fig. d. The head of a viper in which only very small supraciliary and nasal (or anterior frontal) shields are seen. The One other very remarkable exception must not be omitted—namely, that in pythons may be seen an angular head, which makes the neck thin and conspicuous, only in a less degree; and also the absence of large head shields. In addition to this, many of the pythons have particularly short and very pointed tails—three singular viperine features in non-venomous snakes, which can only be inherited from a common ancestry. Another caprice is seen in the carinated or keel-shaped body scales, which are found in venomous and non-venomous, land and water, ground and tree snakes indifferently; though I think one may be safe in affirming that none of the true vipers have unkeeled and polished scales. Nicholson has observed that in several allied species, some have and some have not the keel, and that those without do as well as those with. ‘The history of the keel is not known,’ says this author. In appearance it reminds one of the mid-rib of a leaf or of a feather, and may probably be an inherited feature in common with birds whose reptilian ancestry in process of ages had fluttered their scales into feathers. In fact, in many snakes where no keel is found, there is some slight indication of a centre line, even What are called ‘horns’ in some of the African vipers are curiously-modified scales, which, under close examination, present the appearance of half-curled leaves, sometimes of ears, like those of a rabbit or a mouse. Being only cuticle, and liable to injury, these ‘horns’ vary in size and colour as well as form. The sloughed horns of The accompanying figure is from the slough of the Vipera nasicornis of the coloured illustration. They were not reversed in desquamation, but came off with a portion of the fine spiny head scales. They were so dry and shrivelled at the time, that it is hard to conceive how they could possibly be reversed, the rest of the bristly head-scales peeling off in pieces. Yet we cannot conclude from this that the horns are never reversed in sloughing; the individual in question having undergone long captivity in a close box during her journey from West Africa, and arriving at the Zoological Gardens in such a miserable plight that it was difficult to distinguish species or colouring for many days. In this condition she remained for five weeks, when one fine Sunday afternoon she presented the Society with forty-six viperlings. Soon after this event she discarded her way-worn and bedraggled garment, and shone resplendent in gorgeous colouring, as presented to the reader in the coloured illustration. Her portrait was not taken until some weeks afterwards, when the horns were therefore a little dry and shrivelled again. With the new dress they presented a well-defined and perfect curve, tapering to a point, and without any break in their outline. By degrees they became curled in the manner here represented. Her colours were of a rich prismatic hue on the sides, where the brilliant tints are so blended that to paint them is impossible. Only on the back and in the darker markings can the pattern be fairly represented. Her children all resembled her in their rich tints, and were so handsome that one almost forgot their evil propensities. Forty of them died within a week. I begged hard for one of the deceased. The keeper of course had no power in his hands. All were wanted for scientific experimentalists. Alas, I was no scientist, but only a woman! The following Sunday, when I was at the Gardens, the forty-first baby viper had just died. The Superintendent ‘happened along,’ and was greeted with another appeal from me. He would ‘consider of it’ and let me know ‘to-morrow.’ ‘Oh, why not Suddenly to the rescue appeared on the scene no less a personage than Dr. GÜnther, and to him I urged my request. ‘Well,’ said he in response to my eagerness, ‘one of Our Council is here, and’—Yes, the F.Z.S. referred to had, with the Superintendent, just passed the iron barrier to view the interesting little survivors, and Dr. GÜnther followed, while I discreetly remained outside. My suspense was not of long duration, for soon reappeared the amiable Superintendent daintily carrying a little paper bag which might have contained bon-bons. ‘Fortunately,’ said he, ‘two of Our Council happen to be here, and so,’ etc., and I became the happy possessor of the scarcely cold viperling, here faithfully represented by the side of its mother. Exultantly I carried it off to a sequestered spot,—thinking chiefly of you, dear readers,—and examined its ‘horns,’ which wore the appearance of an ornamental top-knot rather than horns. They were like a bow, or two little ears, or half-unfolded leaves. Its colouring was gorgeous, but the pattern is too fine and complicated to represent on so small a scale. The black triangular mark on the head of both mother and child was like velvet in its density. Nor was this appearance lessened under the lens; for quickly I ran off with my treasure, and spent a delightful ‘evening at home’ in studying its ‘points,’ not even excepting those of tongue and fangs. The former is represented on p. 120, and the latter on p. 360. The other results of my investigations come under their separate heads in this book. Another of the horned serpents, Vipera cornuta, has a
Their natural position is nearly erect, and when one horn—say the longest to the right in Fig. 1—was pressed or pulled outwards, we might suppose that in a dead specimen it would drag its fellow that way also, should any movement at all take place; instead of which, it flew off in the opposite direction, like two negative or two positive poles repelling each other. If I pressed the three to the right as much as in the centre figure, the other three receded similarly to the left. Each pair acted in concert in this remarkable manner, or each two pairs, or all three pairs. The three sketches are given merely in illustration of a phenomenon which I cannot attempt to explain or even to comprehend. They were drawn from memory, and are not therefore offered as exact representations, though near enough to serve our purpose. The movement seems to argue some peculiar muscular or nervous connection between each pair. The serpent had not been long dead; and as no others of this species have since been at the Gardens, I cannot tell whether the same sympathetic movement would be seen in the living viper. I have attentively watched the horns of the other vipers, but never detected the slightest voluntary action in them. Nor do the horns of V. nasicornis respond to the touch in the same way. A third of the horned vipers is the Cerastes of classic times. Illustrators of books from descriptions only have presented us with this serpent adorned with horns like a young heifer. They are simply scaly appendages like the rest, but when perfect do certainly curve backwards and upwards in a rather bovine fashion. It happened that a Cerastes was brought to the Gardens just after the six-horned viper had died, affording me a happy opportunity of examining it. It was of this viper that Pliny wrote: ‘It moves its little horns, often 4 in number, to attract birds, the rest of its body lying concealed.’ It is the habit of all those inhabiting sandy deserts thus to hide themselves, probably to escape the scorching, drying sunshine, and with perhaps the nose and upper part of the head exposed for breathing. I have carefully watched several of the horned vipers for a long while together, but have never detected the slightest volitional movement in their horns. A bird might come and peck at them, nevertheless. Another belonging A curious variety of the nasal appendages appears in the Langaha with the crÊte de coq; only the crest is on the snout instead of on the head. These spurs are merely modifications of the epidermis like the rest; but are, no doubt, endowed with peculiar sensitiveness, so that possibly they act as a sort of herald in the dark, like a cat’s whiskers. Profile of Langaha. There are the pointed-nosed Dryophidians also, with scaly protuberances, and others with variously-elongated snouts terminating in long, scaly, horn-like appendages, all, no doubt, more or less sensitive, to enable the owners to feel their way, or ascertain the nature of their surroundings, especially if they are of nocturnal habits. In some of the tree snakes, notably Passerita, there is no appendage, but the long snout is itself endowed with mobility. This is a nocturnal snake; a harmless and exceedingly slender, graceful creature. Profile of Passerita. But of these curious developments or prolongations, one of the Indian fresh-water snakes presents a remarkable These are some of the most striking head-appendages; though in the way of pug-nosed ophidians and curious profiles we might give a whole page of illustrations. In the acrobatic chapter, mention was made of a pair of rudimentary hind limbs in some of the boas. Externally the derm is condensed into ‘claws’ or ‘hooks.’ In form they are merely long, simple appendages, which in the largest boas are about as big as a finger. Claws and hooks they are in the matter of use, being a pair, and they no doubt assist the climbing snakes in grasping. As a condensed form of the tegument, they are included in this chapter; but as they are truly vestiges of limbs, I will digress a moment to add a word. Says Darwin on rudimentary and atrophied limbs: ‘The disuse of parts leads to their reduced size: and the result is inherited.’ Some tame little lizards in my possession—our native species—when crawling about their cages scratching the sand or pushing their way among the moss and rubbish, frequently made use of their fore legs only, allowing the hind legs to drag after them, not because the latter were in any way injured, but simply because the lizards could do well enough without them. They were folded back or permitted to lie passively prone against the tail, while the arms and exquisite little hands were sufficient for the work required. After thus moralizing to the unheeding lacertines, it was with secret gratification that one heard Professor Huxley, in his Lecture on ‘Snakes’ at the London Institution, Dec. 1, 1879, say—as nearly as I can remember—‘In evolution or a gradual change, the lizard found it profitable to lose its legs and become a snake; all modifications are an improvement to the creature, putting it in a better condition.’ In this ‘better condition,’ therefore, does the slow-worm find itself, when it glides noiselessly, and almost without stirring a blade of grass, into its burrow. In other lizards one may sometimes observe that the hind legs are most used in scratching and pushing the earth away. Thus, in the constricting snakes—these descendants of some pre-ophidian lizards—the unused limbs have become obsolete; and the spine, gaining strength with increased action, has at length become to the constrictors their hands, feet, arms, and legs, and endowed with those wondrous capabilities which were described in chap. xii. To return to the integument. As one of its developments, the hood of the cobra may be included in this chapter, the skin here exhibiting its extensile or expansive construction. It is the longer ribs, about twenty pairs nearest the head (see p. 33), which really do form the hood. These anterior ribs, gradually increasing in length and decreasing again, In the way of external peculiarities the ‘gular fissure’ may be mentioned. It is merely a slight groove or crease extending from the chin longitudinally under the throat for a few inches or more, according to the size of the snake; a sort of wrinkle (fosse) to admit of expansion during the swallowing of prey. Externally snakes have no indication of ears; therefore, in the way of integument, there is nothing to describe in their organ of hearing. But the eye covering is a beautiful and wonderful arrangement. Snakes have no eyelids, and can therefore never close their eyes, a fact which has given rise to a vulgar belief that they never sleep. Their eyes are, however, well developed, particularly in those snakes which live above ground, and are covered with a transparent layer of the epidermis, Illustration of eye covering. For the process of sloughing or casting the skin, the term desquamation—literally, an unscaling—is often used; but this word seems rather to imply an unhealthy action, as if the cuticle peels off in pieces, than the normal operation, which is to shed it entire. It is a matter of surprise—if we are to believe what we read—that few naturalists seem to have witnessed this process, so as to be able to describe it from their own observations; but this must be due more to lack of interest than of opportunity, since the occurrence is very frequent. Those in the vicinity of Zoological Gardens have no excuse for not observing it; yet so lately as Oct. 1879, we find a writer in Nature, vol. xx. p. 530, attempting to describe the Some of the older writers have told us that ‘a snake frequents the spot where it has cast its skin,’ or, in other words, that it selects that locality for its nest—a fact as curiously stated as if you related of a person that he chose for his home the house in which he performed his toilet. Snakes have a strong affection for locality; and where their nest is, there, or near it, their garments are naturally renewed. Another mooted question has been the precise period of sloughing; formerly the accepted opinion was that once a year, viz. in the spring, was the usual habit. This was probably from so many coils of skins being found at this season. That they do change in the spring may be established as an almost invariable rule; but not then only. No precise periods can be given with certainty, because it depends on the individual, its health and surroundings. The ophidian is a fastidious creature, and when his garment becomes soiled or uncomfortable he discards it. Thus after hibernation, when for some months numbers of snakes have been coiled in masses in a cave or under stones and rubbish, and they emerge into daylight, aroused by the sun’s revivifying rays, what more natural than to cast off the old winter garb for a more comfortable suit? Almost invariably, soon after a long journey, and on being established in a new home, a snake re-attires. We have seen what their travelling cages are! Closely nailed up, and often in air-tight boxes in which the poor things are tumbled over and over with as little mercy as ceremony during removal from one conveyance to another, they arrive—as in the case of the African viper (coloured illustration)—in such a pitiable plight that it is next to impossible to identify them. Another almost invariable rule is sloughing soon after birth—that is, in from a week to a fortnight; also, during early and rapid growth, the young snake will change frequently. Most ophiologists fix upon two months as an average time, taking one snake with another; for while one may desquamate every few weeks, another may keep his coat unsoiled for six months. Sir Joseph Fayrer made careful notes on this subject. He had one cobra which changed in rather less than a month—viz. first on Oct. 17th, next on Nov. 10th, and again on Dec. 7th. A Liophis at the London Gardens changed every few weeks, and a Ptyas—he of the lecture exhibition (p. 214)—changed almost once a month on an average. A curiously beautiful object is the cast-off coat, and well worth an examination. You discern the exact form of the reptile’s head, mouth, and nostrils, the exquisitely transparent eye-covering, the various forms of the overlapping or imbricated folds or ‘scales,’ and how admirably the broad ventral plates are adapted for locomotion; particularly noteworthy too is the perfect reversion of this coat of some feet or some yards in length, turned inside out as you may turn a sleeve. The first time I watched the process was with the celebrated Hamadryad soon after it was installed as a distinguished inmate at the Zoological Gardens. The interest attached to this Ophiophagus or snake-eater had caused me to observe it on all possible occasions; and as the whole front of its cage was clear glass at that time, the spectator could easily see all that occurred within. Will the reader once more accompany me in imagination to the Gardens, and see how a snake performs its toilet? I have watched many since then, and have observed the same proceeding in them all, those in good health and able to assist themselves; in others it is a literal desquamation or peeling off of scales or fragments in a dry state. Encouraged by the very recent statement in a highly scientific journal, that no one is supposed ever to have witnessed the sloughing of snakes, I venture to again describe what I saw, having already done so in the Dublin University Magazine in Dec. 1875, and in Aunt Judy’s Magazine (Sept. 1874), and elsewhere. We stand before the cage of the interesting Hamadryad (Ophiophagus elaps). His name at once tells us that he is fond of trees as well as of snakes; but, alas! there is no tree in his cage, not even an old bough on which to exercise his climbing propensities. He is wonderfully restless to-day, crawling ceaselessly about as if in search of something. This, however, cannot be his object; for his head is not raised in observation, but is close to the shingle, as if too heavy to lift. He seems to be pushing it before him in a very strange manner, and is evidently suffering discomfort of some sort. All round his cage he goes, against the edge of the tank, ‘Going to change,’ said Holland. ‘That’s the way they always do.’ To you and me, dear reader, the sight is novel and interesting; so let us continue to watch, glad that nothing more serious is the matter with this rare and valuable snake than doffing an old coat. And soon we see the skin separating at the lips, where, no doubt, it has caused irritation and induced that incessant rubbing. Now the entire upper lip is free, and the loose portion laps back as Ophio pursues his course. Next we see the skin of the under lip detaching itself; and that is also reversed, the two portions above and below the jaw increasing every moment and folding farther and farther back with the ceaseless friction until they look like a cape or hood round Ophio’s neck, from which his clean bright head emerges. Hitherto the process has been tedious, but now the ribs are reached, and they take part in the work and The constricting snakes are less at a loss. From their pliancy of motion, and their habits of coiling—from the fact of their ‘whole body being a hand,’ as we have already seen, they can assist themselves by their own coils passing through them, and so helping to drag off the slough. Those who have kept snakes tell us that the tame ones will even leave the slough in the hand, if you hold them during the process, and permit them to pass gently through the closed fingers. Owen, in his Anatomy of the Vertebrates, mentions as a not unfrequent action, that when the head is free from the slough the snake brings forward the tail, and coils it transversely round the head, then pushes itself through the coil, threading its body through this caudal ring. But we have left our captive with still about a foot and a half of garment to get rid of and this is not much less difficult to accomplish than the head-gear. He has arrived at the last pair of ribs, and now, without such agency to free the tail cuticle, he more than ever needs some opposing obstacle. He has only his blanket, however, to pass under; and at last, by dragging himself along, the process is completed, the extreme few inches sliding off unreversed. On several subsequent occasions the Hamadryad has left the entire tail, often nearly all of it, unreversed, as do many other snakes. Sometimes by a succession of jerks they manage to get rid of this portion; sometimes a comrade happens to pass over the slough—a great assistance, as affording resistance. I observed this particularly in a small constrictor, one of the three that entrapped two or three sparrows in as many coils at the same moment. In this case the whole process occupied less than ten minutes. After rubbing its head against the gravel, and turning it completely over to free itself from the upper shields, its ribs took chief part as usual, and I noted particularly that each pair moved in concert, and not alternately. This little snake went round close under the slanting edge of his bath-pan, which afforded When all was over, the large, beautiful black eyes of this four-striped or ‘four-rayed’ snake were particularly brilliant, as the little constrictor looked about and watched observantly, rejoicing in his newly-found faculty, after the blindness of the preceding days. Often the snakes are shy, and change at night; the tamer ones, however, undress when it suits them, affording frequent opportunities for observation. The slough when first discarded is moist and flabby; but it soon dries, and then in substance is as much like what is called ‘gold-beater’s skin’ as anything else, though a stronger texture is observable in the head-shields and the ventral scales. The size of the scales does not appear to bear any very regular correspondence with the size of their owner; for you will notice that some snakes only three feet in length, have larger scales than others three yards in length. Some of the immense pythons have smaller scales than a rattlesnake; and again, snakes of similar dimensions have scales different both in size and form. As great a variety is seen in the form and arrangement of scales as of shields. Snakes are to a certain extent invalids previous to the shedding of their skin, temporarily blind, courting retirement, and declining food; but they recover triumphantly the At this time, too, their colours show to the greatest advantage, their eyes are brightest, and their personal comfort no doubt is enhanced in every way. Before taking leave of the integument, a few words about the markings or patterns and colouring of serpents may not come amiss. Mr. Ruskin, in his celebrated lecture on Snakes, exhibited to his delighted audience a fine anaconda skin, and drew attention to the ‘disorderly spots, without system,’ with which this snake is marked. Taches À tortue, as it was at first described; and by Dumeril as marked ‘avec de grandes taches semÉes sans ordre.’ Notwithstanding the irregularity the skin is handsome. The oval spots of various sizes and at unequal distances have still a character of their own, as much as the spots of the leopard or the stripes of the zebra, no two of which are placed with mathematical precision. Mr. Ruskin had but few kind words to bestow on ophidian reptiles, but the disorderly patterns of their coats he greatly disapproved. Moreover, the great artist was inclined to pronounce a sweeping verdict on the conspicuous ‘ugliness of the whole poisonous families’ without exception. Now unfortunately we have had occasion to lament the good looks of many venomous kinds which are easily mistaken for harmless snakes. Some of the American elapidÆ are amongst the most beautiful, with their black, white, and Since the subject was thus presented to us, I have, however, observed the markings more closely; and it really is curious as well as interesting to note how very nearly the various patterns approach to a perfectly geometrical design, yet failing in the same manner that a bad workman would fail in imitating the pattern given him to copy. To Dr. Stradling I am indebted for a very handsome boa skin from Brazil. Spread upon the carpet it is like a piece of oilcloth, and at the first glance I exclaimed, ‘Even Mr. Ruskin could not disapprove of this.’ But on closer inspection one was obliged to admit ‘disorder’ throughout. The skin is about ten feet long, and the whole way down the centre of the back runs a pattern which an accomplished artificer would thus represent. There is evident intention of two straight lines with points at equal distances, a very pretty centre of rich brown, picked out with darker shades and spots of white. Throughout the entire ten feet of skin most of the points and intermediate The outer spots also were evidently of triangular intentions, and for the most part occupying the spaces midway between the points. These, of lighter tints, also run the whole length of the snake, the pattern of course diminishing with the size tailwards, but varying in no other way. The question is not whether the strictly geometrical or the less perfect design would be the handsomer, or we might give the preference to the pattern as we find it; but looking closely at any elaborately-marked snake, it certainly is curious to perceive that in every case there is this same attempt at something too difficult to accomplish, as when a novice in fancy-work does her stitches wrong. The same thing is seen in the snakes of the frontispiece, and the same is seen again even in this simple pattern, a chain running down the back of little Echis carinata. The spaces are unequal, the black cross bands imperfect, and the centre spots some round, some oval, some almost absent. Pattern of a snake. May we conclude that this incompleteness is a sign that the design is not fixed by long inheritance? But if it were so, and presented to us with geometrical precision, it is doubtful whether we could admire it equally! |