_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.[90] The ‘variations of form’ include, therefore, the
appendages above mentioned.
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 value for distinction
of species and genera.’[91] For this reason each and all of the head
shields are specially named.
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.
[Illustration:
_Fig. 1._ Top of the head of a Colubrine snake. _r_, rostral; _f’_,
anterior frontal; _f_, posterior frontal; _v_, vertical; _s_,
supraciliary; _o_, occipital; _t_, temporal.
_Fig. 2._ Profile of the same. _t_, temporal; _p_, posterior ocular or
orbital; _a_, anterior ocular or præorbital; _l_, loreal; _n_, nasals;
_uu_, upper labials; **, lower labials.
_Fig. 3._ Under side of the same. **, lower labials; _cc_,
chin-shields; _m_, mental or median lower labial.]
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 temporal and the
labial or lip shields. The study of them is simplified by the initial
letter of each name being used in reference to them. The names used
also speak for themselves; as _mental_, the chin shield; _nasals_, near
the nostril; _rostral_, the beak shields.
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.
[Illustration: Magnified carinated scale.
Magnified head-scale of _Vipera nasicornis_, of the
coloured illustration.]
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 about the nose and mouth,
exceptions which are now and then found in non-venomous ones also.
The preceding three illustrations are the head shields of a Colubrine
snake, in which a greater uniformity prevails. Below are given four
other types, though even here variations are constantly occurring.
[Illustration]
_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 angular form of
the viperine head is here noteworthy. In some of the Tropical American
viperine species (the _Crotalidæ_) the angular head is so marked as
to be separated into a genus—the _Trigonocephali_, three-cornered
heads. One head is sagittate or arrow-shaped to such an extent that the
serpent is known as the _Fer de lance_, the dreaded _Trigonocephalus
lanceolatus_ of the Antilles. There are _Trigonocephali_ among the
Indian Thanatophidia also.
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 if it take the form of
a groove or depression. In the _Tropidonoti_ the keel is so developed
as to distinguish the group; yet many with keels have comparatively
smooth skins. The carinated scales of vipers (from _carina_, a keel)
are sharply defined, like the keel at the prow of a ship, or like the
breast-bone of the swift-flying birds which Mr. Sclater, in one of
his zoological lectures, described as the carinate birds. It is these
sharply-defined, stiff; and dull scales belonging to the vipers which
produce the rustling noise when the snake is agitated, as described in
the little Indian _Echis carinata_ in the chapter on hissing. In the
_Cerastes_ I have witnessed the same agitated convolutions accompanied
by the audible rustling produced by the rough scales. See illus. p. 317.
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.
[Illustration: The sloughed horns of _Vipera nasicornis_ (exact size).]
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.
[Illustration: VIPERA NASICORNIS AND YOUNG ONE.
AFRICA.
Mother over five feet long, Viperling 9 inches.]
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 _now_?’ pleaded the
reader’s devoted servant. ‘You can’t want forty-one little dead vipers!’
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 cluster of
leaf-like scales in three distinct pairs decorating its nose. These in
the individual at the Zoological Gardens were particularly ear-like,
and there was a remarkable peculiarity about them which was not found
in either of the other horned specimens when dead. It was, that when
one horn was moved divergently with the finger, its fellow moved
_without being touched_ to correspond, and when let go _both_ sprang
back to their original position. I at first was merely feeling and
examining them when this singularly sympathetic movement arrested my
attention. Then I tried it with each of the six scales or ‘horns’
several times, and always with the same result. Whichever one of them
was held back, the opposite one diverged at a corresponding angle.
[Illustration:
1. Natural position.
2. Three held back to their utmost.
3. Three held back partly.]
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 to South Africa
(_Lophophrys_) has a bunch of irregular and much shorter horns standing
erect and apparently unpaired. Incipient horny scales often accompany
the regular pairs, making it difficult to decide exactly which was
Pliny’s of the ‘four horns,’ and which is the _Hexacornis_ of Shaw.
Varieties exist and add to the perplexity; probably also hybrids occur
among these as among non-viperine snakes.
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.
[Illustration: 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.
[Illustration: Profile of _Passerita_.]
But of these curious developments or prolongations, one of the Indian
fresh-water snakes presents a remarkable example, almost allying
it to some of the fishes with long tentacular appendages. _Herpeton
tentaculum_ is its name, its pair of tentacles being scaly and
flexible, and in appearance somewhat like the African viper’s horns,
sticking out horizontally from its snout. They are employed under water
as organs of touch, and probably to discern food.
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. They reminded one of Darwin’s words,
and though my style of talking to my pets was such as to suit lizard
comprehension solely, I did sometimes warn them in plain English. ‘If
you don’t give your legs sufficient exercise, they will dwindle away by
and by, and your descendants will have no hind legs at all!’
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, are not connected with the ventral scales in the
same way as those on which the snake progresses, but can be elevated
or expanded in the manner familiar to the reader; they then support
the extended skin exactly in the way that the ribs of a lined parasol
support the fabric; only while the ribs of the parasol spring from a
common centre, the ribs of the cobra are attached to its vertebræ,
requiring no other agency than the will of the owner. The action of
the ribs as expressive of emotion, in several species of snakes, was
mentioned page 150. In the ‘hooded’ snakes (_naja_), it is seen in an
extreme degree. Facing you, the angry cobra displays these umbra-like
expanded ribs, while the form of the ‘neck’ or vertebral column in the
centre is prominently perceptible. When at rest, they all lie flat one
over the other, like the ribs of a closed parasol.
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, forming a capsule which is moulted with
the cuticle. Physiologists tell us that it is moistened with the
lachrymal fluid. Bright and glistening is the serpent’s eye, except
previous to desquamation, when, from the new skin forming beneath, it
becomes opaque and dull, and the snake is blind for a few days more or
less, according to its health at the time. Rymer Jones considers the
transparent membrane cast with the slough a real eyelid in a framework
of regular scales; Huxley (in the lecture already alluded to) said
snakes’ eyelids are as if our two eyelids were joined. In form and
appearance this moulted cuticle is singularly clear and shapely: on the
outer side, like a miniature watchglass; but within it is a perfect
cup, standing up and out from the surrounding scales like a cup in a
saucer, the rounded base of which is the transparent skin, as here seen.
[Illustration: 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 ‘skin-shedding,’
with the admission that he has never witnessed the process, nor, he
believes, ‘has any observer’! He thinks snakes shed the skin ‘as if you
turned a narrow hem, or a glove-finger by a knotted thread fastened at
the tip,’ and which of course would draw the tip _inside_ the finger.
The glove tip is to represent the tail of the snake, which, as he
supposes, adhering _at the tip_, is drawn along _inwards_ as the snake
proceeds to crawl out of its own mouth, or its cuticle’s mouth—which
has already become loosened round the lips. This, in the mind of that
writer, satisfactorily accounts for the skin being usually found
reversed! Can he have never seen a silkworm change its skin; or found
the slough of a common caterpillar adhering to its tail; or observed
the appearance of its mouth previous to the moulting? True, a slow-worm
sometimes leaves its slough in a crumpled-up condition, exactly like
the silk-worm’s. This I have seen. On the other hand, the same little
reptile, on another occasion, crawled out of its coat, leaving it
perfect and unreversed through its entire length. Both sloughs have
been preserved. As a more general rule the slough is reversed; but in
the process it folds back and over the body, _outside_ of it, in the
manner of a stocking drawn off from knee-wards, and turning back till
entirely reversed it leaves the foot. This common and apt illustration
is easily understood if we suppose the top of the stocking to be the
mouth of the slough, and the toe its tail. But as the toes might
sometimes slip out of a stocking when nearly off, so does the tail
of a snake sometimes slip out; this portion therefore is often found
_unreversed_. More than a hundred years ago the sloughing of snakes was
understood and described in the _Phil. Trans._ for 1747, vol. xl.; as
also of lizards ‘slipping off their skins as vipers do.’ Some young
vipers changed at six weeks old, and again in two months after that.
‘They always began at the mouth,’ said the writer. The process has been
witnessed and described by many since that, though more by foreign than
by English naturalists.
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, still pushing and
rubbing his head, now under his blanket, or against any projecting
surface, under again, close to the floor, restlessly on and on in these
untiring perambulations; what can be the cause? After a tedious while
‘Ophio’—as his admirers call him—varies his movements, but only to
turn the chin upwards and push his head sideways over the shingle.
Now the other side he pushes along: the action is like that of a cat
rubbing her head against your chair. Now he turns his head completely
over, so that the top of it may come in for its share of rubbing;
and such for a considerable time are his persistent movements, while
we watch him wonderingly, and at length point him out to the keeper
inquiringly.
‘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 facilitate matters greatly. The snake has no
longer to rub himself so vigorously, but simply to keep moving; and at
every step, so to speak—that is, with every pair of ribs in succession
beginning at the neck—the large ventral scale belonging to that pair
is shoved off, carrying with it the complete circle of scales. With an
almost imperceptible nudge each pair of ribs eases off a portion, which
continually lengthening as it is vacated, and reversed of course, folds
back more and more, till Ophio looks as if he were crawling out of a
silken tube. As he thus proceeds, now very rapidly, he emerges bright
and beautiful—six inches, a foot, two feet; and all the while each
pair of ribs successively performs its part with that nudging sort of
action, like elbowing off a coat sleeve. If we had begun to count from
the very first pair, and if he had not gone under his blanket during
the process, we could have told the precise number of pairs of ribs
which he has to assist his toilet. He had two yards and a half of old
coat to walk out of, but this he achieves in far less time than it
took him to get his head clear. In his native tree or jungle he would
have found leaves and underbrush to aid the operation; and it would
be a great kindness to snakes in captivity to provide them with wisps
of straw, when sloughing, or some rough rubbish in their cages. Soft
blankets and smooth wood-work do not offer sufficient resistance for
them.
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 him some assistance, and by the time he reappeared in
front the whole slough was discarded, excepting a few inches of tail.
These few inches caused some trouble, until his friend the python
happened to pass over it, when with one final jerk the slough was free
and entire from lip to tip. It was the quickest and most complete
sloughing I have ever watched.
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 moment the slough is discarded.
They then appear to rejoice in a new existence, their functions are in
fullest activity, their appetite keen. At this time the poisonous kinds
are most to be dreaded, probably from the venom having accumulated
during the quiescent condition.
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 crimson rings. The African viper and her young one
baffle the artist’s palette in their prismatic hues, as do several
other of the horned snakes. Indeed, for rich colourings the venomous
kinds rather carry the day. The _form_, it is true, is often clumsy
and ungraceful in the vipers, but as an exception we have ‘_vipera
elegans_,’ and others of less ugly and slighter forms.
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.
[Illustration: Plan of design.]
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 centres had a splash
or spot of white, and most of the points were opposite, but no two feet
consecutively could I find with better finished markings than this.
[Illustration: Exact pattern with the lateral spots.]
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.
[Illustration: 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!
[Illustration]
[Illustration]