_OPHIDIAN ACROBATS: CONSTRUCTION AND CONSTRICTION._
BEFORE discussing the most remarkable of all ophidian caudal
appendages, the _Crotalus_ rattle, and the many speculations regarding
it, we will enumerate some other acrobatic achievements of which snakes
are capable; as, in accounting for these, some interesting facts
appertaining to their anatomical structure can be described.
A humorous journalist has said, ‘There is apparently nothing that a
snake can _not_ do, except swallow a porcupine.’[63] Presuming that
he alludes to physical feats, he is not far from wrong. For all that,
the Western pioneers of America tell us of yet one more thing that
these reptiles cannot accomplish, and that is, cross over a rope
of horse-hair. Having by accident discovered that they turn aside
from this, some Western settlers, when camping out, have effectually
entrenched themselves within a circle of horse-hair rope as a barrier
to rattlesnakes while sleeping.
Let us try to account for this.
Many of my readers have seen the cast-off coat of a snake. Those who
have not can have the pleasure of examining one or several the next
time they go to the Zoological Gardens, where the obliging keeper
will cheerfully exhibit them. Others at a distance may not enjoy this
facility, and for these the accompanying diagrams may be a slight
compensation.
[Illustration: Portion of slough of a rattlesnake (exact size).
Ventral scales of the same, and a section.]
The whole cuticle or epidermis of a serpent is composed of these
overlapping scales, of which the above illustrations are only
fragments. Thus when we speak of their _scales_, we do not mean
distinct and separable laminæ, like the scales of some fishes, each
of which may be scraped or plucked off, and which overlie each other
like the feathers of birds. The covering of a snake is one entire
piece, loose-fitting, and so arranged as to lie in those scale-like
folds which accommodate themselves to every movement of the body. The
ventral or under scales are, in fact, a regular kilting, as may be seen
by the section; and the upper ones correspond somewhat with what our
lady friends call the shell or the leaf pattern in knitting work. The
outer or exposed folds are stronger, thicker, and more hardened than
the inner parts, just as the knitter ‘throws up’ her pattern with a
coarser wool or larger needles, and knits the less conspicuous parts in
a softer material. The naked space of thinner skin between these scales
being very considerable, one can therefore easily understand how,
when a snake would attempt to pass over a horse-hair rope, the sharp,
prickly hairs, standing out _chevaux-de-frise_ fashion, would insinuate
themselves unpleasantly in those softer and more vulnerable interstices
which become exposed by the sinuations of the body. Probably, if we
knew it, or had an opportunity of observing, we should ascertain that
snakes do not crawl over furze bushes, or thistles, or the prickly pear
(_opuntia_), or any similar vegetation of tropical climates, and for
the same reason. The close-scaled burrowing snakes, with their hard
and strong cuirass all round them, might have nothing to fear from a
furze bush; but this is mere speculation. That fine, sharp spines or
prickles, and therefore a horse-hair rope, would incommode the tender
intermediate epidermal folds of other snakes, we can well suppose. Had
they sense enough to _leap_ the obstacle, this they could easily do,
after the manner of ‘leaping’ already described; but the ‘leap’ is only
an instinctive action used in pursuit or escape; and it may be equally
instinctive to turn aside from uncomfortable obstacles, whether prickly
pears or horse-hair ropes.
Mr. Ruskin, in his highly-entertaining lecture on ‘Snakes,’ at the
London Institution, March 1880 (a lecture which, by the way, was
artistic, poetic, figurative, imaginative—‘Snakes’ from a Ruskin, but
not a zoological, point of view), remarked ‘that no scientific book
tells us why the reptile _is_ a “serpent,” _i.e._ serpentine in its
motions, and why it cannot go straight.’ Now, may not the fact that
snakes have acquired these ever-varying sinuations arise from their
sensitiveness to the slightest, and what would be to other creatures
almost impalpable, obstructions in their path?—mere inequalities which
in their lazy nature it is easier, they know not why, to circumvent
than to surmount; because they _can_ go straight, and _do_ go straight
when the way is plain.
Rymer Jones, in his _Organization of the Animal Kingdom_, thinks that
their sense of touch from the nature of their integument must be
extremely imperfect; they being ‘deprived of any limbs which can be
regarded as tactile organs,’ p. 753. But close observation leads one
to agree rather with a much older writer, Roget, who, in his _Animal
Physiology_, intimates that the peculiar conformation of serpents must
be exceedingly favourable to the acquisition of correct perceptions of
touch, and that these perceptions which lead to a perfect acquaintance
with the tangible properties of surrounding bodies must contribute much
to the sagacity of snakes;—that their whole body is a hand, conferring
some of the advantages of that instrument.
That this latter faculty is strictly and marvellously the case, we
shall presently see, owing to the flexibility of the spine, and its
capability of grasping and twining round objects of almost any shape,
and of taking, as Roget says, ‘their exact measure.’ For this grasping
power is not confined to the constricting snakes only. In all snakes
a great flexibility is abundantly provided for in the construction
of ‘these lithe and elegant beings,’ as Rymer Jones in unprejudiced
language calls them (p. 724 of the book above quoted); ‘the spinal
column admits the utmost pliancy of motion in any required direction.’
Though snakes have no limbs externally, ‘the work of hands, feet, and
fins is performed by a modification of the vertebral column.’[64]
‘Except flying, there is no limit to their locomotion,’ said Professor
Huxley in _his_ lecture on ‘Snakes,’ a few weeks previously to that of
Ruskin, and under the same roof. To both these lectures we shall again
refer, as the reader will feel sure that all coming from such sources
must add value to the present writer’s arguments.
As ‘flying,’ the swift motions of many snakes have been described by
ancient writers, as, for example, the ‘flying serpents’ of Scripture,
though these are by many supposed to be the _Dracunculi_, the earliest
known of human parasites. The astonishing movements of serpents were,
however, in superstitious ages ascribed to supernatural agency. Says
Pliny: ‘The Jaculus darts from trees, flies through the air as if
it were hurled from an engine.’ The ‘wisest of men’ admitted that
the actions of serpents were beyond his comprehension; ‘the way of a
serpent on a rock’ was ‘too wonderful’ for him.
Even in intermediate ages, when travellers and naturalists began to
confront fiction with fact, even in the days of Buffon and Lacepède,
a serpent was regarded as a living allegory rather than a zoological
reality by many intelligent, albeit unscientific persons. Of such
was Chateaubriand, whose contemplation of the serpent partook of
religious awe. ‘Everything is mysterious, secret, astonishing in this
incomprehensible reptile. His movements differ from those of all
other animals. It is impossible to say where his locomotive principle
lies, for he has neither fins, nor feet, nor wings; and yet he flits
like a shadow, he vanishes as if by magic, he reappears, and is gone
again like a light azure vapour on the gleams of a sabre in the dark.
Now he curls himself into a circle, and projects a tongue of fire;
now standing erect upon the extremity of his tail he moves as if by
enchantment. He rolls himself into a ball, rises and falls like a
spiral line, gives to his rings the undulations of a wave, twines round
the branches of trees, glides under the grass of the meadow, or skims
along the surface of the water,’ and so forth.[65]
Excepting the ‘tongue of fire,’ the whole of this poetic description is
so far true and unexaggerated, that Chateaubriand has not attributed
to the reptile one action of which it is not capable, and which, to
the untutored mind, might well seem supernatural. Roget, Schlegel,
Huxley, and others tell us the same things in the language of science.
To quote them all is impossible; the reader will be content with one
scientific assurance of ophidian capabilities, not less poetic than
Chateaubriand’s.
Professor Owen, in describing the bony structure of the Ophidia,
and in allusion to the scriptural text—‘Upon thy belly shalt thou
go’—affirms that so far from the reptiles being degraded from a higher
type, their whole organization demonstrates how exquisitely their parts
are adapted to their necessities, and thus proceeds: ‘They can outclimb
the monkey, outswim the fish, outleap the jerboa, and suddenly loosing
the coils of their crouching spiral, they can spring into the air and
seize the bird upon its wing.’
The active snakes can always ‘leap’ their own length, whether upwards
to seize a bird, or horizontally, and, as in the case of the Jamaica
boa (described p. 186), can leap much farther from a similar impetus
when the direction is _downwards_. Indeed, they can let themselves fall
from a certain elevation with an additional impetus to progress, as a
boy first runs in order to leap a ditch.
‘With neither hands nor talons, they can out-wrestle the athlete,
and crush their prey in the embrace of their ponderous, overlapping
folds.... Instead of licking up its food as it glides along, the
serpent uplifts its crushed prey, and presents it grasped in its
death-like coil, as in a hand, to its gaping mouth.’[66]
A similarly graphic account is given by Rymer Jones, p. 718 of his
work,[67] that will be read with interest by those who wish to pursue
the study scientifically.
In watching the larger constricting snakes while feeding, you see
how _dexterously_ they manage.—(One may use this word here, because
those above quoted, ‘as in a hand,’ are literally, scientifically
true; therefore we may suppose fingers as well as a hand, and say how
dexterously the creatures bring their coils to their aid.)
They have quickly strangled and begun to eat, say an opossum or
a turkey buzzard, when a part of the prey not swallowed offers
some impediment to the expanded jaws; the wings or legs may be
inconveniently extended, or have become wedged between some immoveable
obstacles—a log, a narrow space, or under a portion of themselves.
Their mouth, the only apparent grasping agent, is already occupied, and
a strain sufficiently powerful, while the jaws are thus retaining the
prey, would be painful to the feeder, might even drag back the food,
to the injury of the engaged teeth. How does the reptile proceed in
this emergency? With the lightness and deftness of enormous strength,
it applies two folds of its body, two loops of its own coils, and with
them drags forth, lifts up, or otherwise adjusts its prey in a more
convenient position—in fact, ‘presents it as in a hand’ to its own
mouth.
A very remarkable instance of a constricting snake thus using its
coils is related by Dr. Elliott Coues, of the United States army,
late surgeon and naturalist to the United States Northern Boundary
Commission. He witnessed one of those frequent combats between the
Racer and the Rattlesnake, in which the former—and in far less time
than it takes to read one line of this page—threw two folds or coils
round his adversary, one coil of the anterior portion of his own body
round one part, and a second coil of the posterior portion of his own
body round another part, and then, by a sudden extension of himself,
tore the rattlesnake in halves. And this was done with greater ease
and swiftness than we could snap a thread which we must first secure
round the fingers of our two hands. As if indeed possessed of two
hands, the constrictor snapped his foe in twain. This is Lawson’s
‘Whipster,’ p. 182.
The coiling of the constricting snakes is like lightning; you cannot
follow the movements. In this case death must have been instantaneous,
and indeed it is doubtful whether any beast or bird of prey puts his
victim to a more speedy and less torturing death than the constrictors
when following their own instincts.
Repairing to the Zoological Gardens in the hope of witnessing the
wonderful adaptation of coils to manual uses, after reading what
Roget and Owen had affirmed, one soon had a favourable opportunity
in watching a python. It was, I think, in June 1874, and the poor
python had a ruptured side. In spite of which—as my zoological notes
record—‘it helped by the folds of its body to get the wings of the
duck down flat and close, so as to swallow it more easily. With reason
does Roget say, “Its whole body is a hand,” for it used its loops to
hold and to push and to flatten in a manner truly intelligent.’
Such was my first entry and observation. Subsequently, and indeed
almost on every feeding day, the same kind of thing was to be seen at
the Gardens. Many such examples are recorded in my notebook; but of
these one or two later notes will suffice to illustrate the subject.
[Illustration: ‘Totsey,’ a python born in the Gardens, June 30, 1877,
taking her supper, Sept. 24, 1880.]
A young python was hanging from a branch, more than half its body
curved as in the accompanying sketch, remaining motionless and
quiescent, watching some sparrows which the keeper had just put into
the cage. The birds, eyeing certain insects among the gravel, seemed
all unconscious of the pair of glistening eyes looking down upon them.
Suddenly a movement, a flicker, like the flash of a whip, and the snake
had changed its position. Too quick for us to follow the motion, but in
that flash of time it now hung like a pendulum, with a sparrow almost
hidden in its coils. The snake had precisely measured its distance,
reached down, and recoiled with the swiftness of an elastic spring.
After a few minutes, _feeling_ that its prey was dead, it prepared to
swallow it, holding it encircled in a portion of its body, while the
head was free to commence the usual examination. Still hanging there,
it held and devoured the bird.
On another occasion, one of the larger pythons caught a guinea-pig
in the same manner. This also was so quick in its movements that one
scarcely knew what had happened until the snake was seen to have
changed its position, some of the anterior coils had embraced a
something, and a quadruped was missing. This snake also still hung
while eating its meal, the whole process occupying less than ten
minutes. In both these cases we saw the prehensile tail in its natural
use, while the rest of the body was free for action.
One of the most remarkable cases of what we may call independent
constricting powers, that is, two or more parts of the reptile being
engaged at the same time, was in some very hungry, or very greedy, or
very sagacious little constrictors, the ‘four-rayed snakes,’ _Elaphis
quater-radiatus_.
They are slender for their length, which may be from three to five
feet, of an inconspicuous colour, but with two black lines on each
side, running the whole length of their body; hence their name,
‘four-lined,’ or ‘four-rayed.’ In the present instance, there were in
the same cage three of these, also one young royal python, one small
common boa, and one ‘thick-necked tree boa’ (_Epicratis cenchris_), all
constrictors. The day was close and warm for April, and the snakes,
reviving from their winter torpor, seemed particularly active and
lively. Probably they had not fed much of late, and thought now was
their opportunity, for the keeper no sooner threw the birds—finches,
and plenty of them for all—into the cage, than there was a general
scuffle. Each of the six snakes seized its bird and entwined it,
then on the part of the reptiles all was comparatively still. The
rest of the poor little birds, fluttering hither and thither, were,
however, not disregarded, for although each snake was constricting its
captive, several of them captured another bird by pressing it beneath
them, and holding it down with a disengaged part of themselves. One
of the four-rayed snakes felt its held-down victim struggling, and
instantaneously a second coil was thrown round it. Then another caught
a second bird in its mouth, for its head and neck were not occupied
with the bird already held, and in order to have coils at its disposal,
slipped down its first captive, or rather passed itself onwards to
constrict the second, the earlier coils not changing in form in the
slightest degree, any more than a ring passed down a cord would change
its form. The next moment I saw one of those two hungry ones with
three birds under its control. It had already begun to eat the first,
a second was coiled about eight inches behind, and a good deal of
the posterior portion of the reptile was still disengaged when a bird
passed across its tail, and instantly that was captured. All this was
done by a sense of feeling only, as the snakes did not once turn their
heads. Two of these ‘four-rayed’ snakes were so close together, so
rapid in their movements, so excited and eager for their prey, that
which of them first began his bird, and which one caught the third, it
is impossible to affirm confidently.
Whenever either of them was in the same position for one quiet minute,
a few hurried strokes of the pencil fixed them in my notebook, and of
the hasty though faithful sketches thus made, I present three to the
reader on the opposite page.
April 1st, 1881.—After this date nothing more was to be seen!
Henceforth visitors were to be excluded, and the reptiles were to be
fed _after sunset_.
Now, however painfully and sympathetically we may regard those poor
little birds so unceremoniously seized, crushed, and devoured, we can
but reverently, and almost with awe, admire the astonishing facility
with which these limbless, toolless reptiles provide themselves
with food. With still deeper awe and reverence we shall admire when
we examine their anatomical structure, and see by what marvellous
development it has been adapted to their necessities.
We feel sadly for the finches, it is true; because finches are often
our pets, and are sweet songsters. Were a toad or a rat thus treated,
we should care less, perhaps; because there is as much repugnance
towards toads and ‘vermin,’ as towards snakes.
[Illustration: First bird caught and a second held down.
First bird dead, the second coiled, and a third bird caught.
First bird half eaten, two others in coils.
_April 1st, 1881._]
But if the finches did not become the prey of snakes, they would become
the victims of bird-catchers and milliners; and if they escaped these
wanton spoilers, they would fall victims to birds of prey, as much
larger birds fall victims to our own need of food.
Reptiles also have existence and requirements, and an organization
adapted to such requirements. This should be their claim upon our
tolerance; and if they do not win our admiration, we cannot deny them
the right to live, the right to feed according to their instincts,
and to secure their natural food in their own way, which—begging the
reader to pardon this feeble moralizing—we find to be a very wonderful
way.
Though the term ‘reptile’ is applied to a whole tribe of crawling
creatures, whether four-legged or limbless, that are covered with
scales, horny plates, or a skin more or less hardened, imbricated, or
rugose (viz. crocodiles, lizards, frogs, toads, serpents, and their
congeners), snakes are more truly reptiles, being limbless, from
_repo_, to creep. Hence serpents (from _serpo_, to creep, and its
derivatives serpentine, serpentize, etc., from _serpens_, winding)
have been separated from the rest. The true serpents, therefore, are
those without feet, and which move only close to the ground, by the
sinuations of their body.
We have seen that the constricting snakes use this body as a substitute
for hands, literally _managing_ with it; but though they are externally
legless, and _apodal_ (without feet), the truth is that few creatures,
none perhaps, not even millipedes, are more liberally furnished with
legs and feet than serpents. One curious exception to general rules is,
that while other creatures have the same number of feet as legs, that
is, one foot to each leg, a snake has only one foot to each pair of
legs!
Many of my observant readers have already discovered for themselves
where and what these numerous legs and feet are. In the early days of
my ophidian studies, which then consisted chiefly of observations, I
noticed the action of limbs beneath the skin of the pythons as they
moved about, and more particularly when they were climbing up the glass
in front of their cages, and as in the case of the glottis, I thought
I had made a grand discovery; and so I had, as far as myself was
concerned.
Deductions from personal observation, which in the history of many
sciences have again and again been claimed as original discoveries by
rival thinkers or experimentalists, no doubt _were_ original on the
part of each.
Probably, also, many other persons have noticed this leg-like action
of the ribs, but who, not being specially interested in snakeology,
have never troubled themselves to ascertain ‘further particulars,’ or
cared whether any one else had observed this or not. But it _is_ a very
evident and unmistakeable action, and one quite worth studying on your
next visit to the Reptilium.
Books on ophiology tell us that Sir Joseph Banks was the first to
observe this limb-like action of the ribs. Sir Everard—then Mr.—Home,
F.R.S, and the most distinguished anatomist of his time, was, however,
the first to publish a scientific description of the fact; his account
and the illustrations accompanying it having been subsequently adopted
by most ophiologists.
In vol. cii. of the _Philosophical Transactions_ of 1812, p. 163, is a
paper which was read before the Royal Society in February of that year,
by Everard Home, Esq., F.R.S. It is entitled, ‘Observations to show
that the Progressive Motion of Snakes is partly performed by the Ribs.’
We give his introductory words, not only because the ‘discovery’ was
a great event in the history of ophiology, but as showing that to see
and examine a foreign snake was at that time a rare if not a novel
occurrence. He tells us that on a former occasion in 1804, he had
described the anterior ribs of a cobra, those which form the ‘hood.’ At
that time he was ‘not in possession of the bodies of snakes,’ so that
he could compare their structure, but had _since_ found out a good deal
more about their anatomy, and then he proceeds: ‘A Coluber of unusual
size lately brought to London to be exhibited, was shown to Sir Joseph
Banks. The animal was lively and moved along the carpet briskly; while
it was doing so, Sir Joseph thought he saw the ribs come forward in
succession, like the feet of a caterpillar. This remark he immediately
communicated to me, and gave me an opportunity of seeing the snake
and making my own observations. The fact was already established, and
I could feel the ribs with my fingers as they were brought forward.
I placed my hand under the snake, and the ribs were felt distinctly
upon the palm as the animal passed over it. This becomes the more
interesting discovery as it constitutes a new species of progressive
motion, and one widely different from those already known.’
The ‘unusually large Coluber’ was probably a python. Had a previous
opportunity presented itself to this scientific and thoughtful
observer, Sir Joseph Banks might not have been the one to carry off
the palm in this discovery. Home had already described the peculiarity
of the cobra’s anterior ribs (chap. xviii.), and, as already suggested,
it is scarcely possible to watch one of those larger constrictors
_without_ perceiving the mode of progression. We shall see in the
course of this book that snake observers have arrived at the same
conclusions on several points, while wholly ignorant of what others had
said or decided regarding the same.
In the previous chapter the number of vertebræ forming the spinal
column of three or four snakes was given, but this number varies
greatly, not only in snakes but in species. In some species there are
above 400 vertebræ or joints in a snake’s spine. But here is a puzzle
that baffles the student. ‘Every one knows,’ says Schlegel, ‘that their
number differs’ (speaking of the vertebræ), ‘not only according to the
species, but also in individuals, so that sometimes we find in serpents
of the same species a difference of thirty or forty vertebræ more or
less.’[68]
Taking this literally according to the text, one might expect to find
one ring-snake in a family of ten measuring two feet, while his brother
measured two yards, and a third four feet, and so on, as if each had a
different number of vertebræ.
‘The same species,’ that is, two anacondas or two cobras! ‘A
mistranslation,’ one naturally decided, and proceeded to consult the
original. But no. The translator had faithfully and unquestioningly
followed the original French; but the fact was so irreconcilable that I
sought Dr. Günther’s kind assistance in comprehending the passage.
‘Evidently an oversight. Manifestly impossible,’ that learned authority
at once decided. (As Schlegel stands high as a scientific ophiologist,
the misprint is pointed out for the benefit of future students.)
Thus lengths, _as to the number of vertebræ_, vary in species of the
same genus, but _not_ in ‘individuals of the same species.’ And this
alone is sufficiently perplexing.
For example, we read in one work that a rattlesnake has 194 vertebræ,
and in another that ‘it,’ viz. ‘a rattlesnake,’ has 207 vertebræ. Both
equally correct, because two distinct species are described. Again,
Dr. Carpenter, in his _Animal Physiology_ (edition of 1872), gives a
table of the vertebræ of various animals, in which ‘a python’ has 422
joints, while Owen gives ‘a python’ 291 joints, each learned anatomist
having examined a different species. By these facts we comprehend what
Schlegel intended to say.
The little constrictors caught their finches with five feet of body
at their disposal. An anaconda, with five yards of body to work with,
might with equal ease coil three opossums.
‘The skeleton of a snake exhibits the greatest possible simplicity
to which a vertebrate animal can be reduced,’ says Roget. It is
‘merely a lengthened spinal column.’ It is ‘simple’ in the same way
that botanists call a stem simple when it has no branches, or bracts,
or leaves, to interrupt its uniformity. For this reason, having no
limbs, and therefore none of those bones which in quadrupeds connect
the limbs to the trunk, the spine is, in unscientific language, alike
all the way down; ‘_un corps tout en tronc_.’ And because those two
first joints of the spine which have no ribs attached to them are in
form precisely like the other joints, physiologists tell us that a
snake has ‘no neck.’ By way of simplifying matters we just now called
those two joints an invariable neck. But in the way of _cervical_ or
neck vertebræ, however, we must bear in mind that a true anatomical
neck, in the eyes of science, a snake has not. Some of the four-legged
reptiles have a true neck, that is, they have cervical vertebræ which
differ from dorsal, lumbar, etc. vertebræ, as we ourselves and mammals
in general have; because four-legged reptiles have a breast-bone and
limbs to support, and their neck varies in length. For example, a
tortoise has nine cervical or neck joints, a monitor lizard six, and a
salamander only one.
But so also do the necks of mammals vary very greatly _in length_,
while all, without exception, are formed of seven joints, _only seven
vertebræ_; a man, a whale, a giraffe, and a mouse possess each seven
cervical vertebræ, different in form from the rest of the joints of the
spinal column. We might say that in appearance a whale has no neck,
but its seven neck joints are flat and close as seven cards or seven
pennies, while those of the giraffe are extraordinarily prolonged; and
in ourselves—well, of course, the reader will admit the perfection
of symmetry in our own necks, and the seven joints, therefore, are
precisely of the proper size.
While the spine of a snake is ‘simple’ in respect of its joints being
all formed on the same plan, it is the reverse of simple in its
wonderfully complex structure. Professor Huxley, in his delightful
lecture, said that ‘the most beautiful piece of anatomy he knew was
the vertebra of a snake.’ Professor Owen thus anatomically describes
it: ‘The vertebræ of serpents articulate with each other by eight
joints, in addition to those of the cup and ball on the centrum; and
interlock by parts reciprocally receiving and entering one another,
like the joints called tenon and mortice in carpentry’ (_Anatomy of the
Vertebrates_, p. 54).
[Illustration: Front and back view of a vertebra.]
Bearing in mind that each of these highly complicated joints supports
a pair of moveable ribs, and that the ends of these ribs are connected
by muscles with the large stiff scutes or scales crossing the under
surface of the body (see illustrations, p. 193), which move with the
ribs, one foot-like scale to each pair, we comprehend how snakes exceed
millipedes in the number of their _limbs_, if not true legs, and how
they excel the insect also in variety of movement. Those ‘ball and
socket’ joints admit of free lateral flexion, and every variety of
curvature—‘_the utmost pliancy of motion_,’ to repeat the words of
Rymer Jones; and also of that surprisingly independent motion which
enables the constrictors to surpass even the _Bimana_ (except practised
experts) in doing _several things at once_.
Thoughtful persons who can contemplate this wondrous organization with
due reverence, and witness it in activity—as we admiringly observe the
works of a watch in motion—will forget to censure those who supply
food to this piece of animated mechanism, and even pardon a hungry
little snake for so expertly securing three birds at once.
Think of 300 back-bones and 300 pairs of legs, all requiring wholesome
exercise. Some snakes have 300 pairs of ribs—each pair capable of
independent motion, and articulated with that complex spine; and each
pair moving together, and carrying along with them a foot in the shape
of a broad ventral scale. ‘This scutum by its posterior edge lays hold
of the ground,’ says Sir Everard Home, ‘and becomes a fixed point
whence to set out anew.’
The hold which the ventral scales have of the ground obviously renders
it easier for the reptiles to pass over a rough than a smooth surface;
what are obstacles to other creatures are facilities to them. But they
appear to be never at a loss. On a boarded room, or even a marble
floor, they will manage progression of some sort,—many by the pressure
of the tail to push themselves forward, and others with an action that
can be compared only with swimming. With the same rapid, undulating
motion as swimming, the active snakes skim through the grass, or over
soft herbage, on which they seem to make no impression. Their swift
sinuations are almost invisible to the eye. You only know that a snake
_was_ there, and now has vanished. The ‘Rat’ snake of Ceylon (_Ptyas
mucosus_) (see frontispiece) and the ‘Pilot’ snakes of America are
among the best known of these swift-flitting or gliding creatures.
Rats are fleet little quadrupeds, but their enemies, the Rat snakes
of India, are more than their match. Sir Emerson Tennant, in his
_History of Ceylon_, describes an encounter with one. _Ptyas mucosus_
caught a rat, and both captor and captive were promptly covered with
a glass shade to be watched. With an instinct to escape stronger than
hunger, _Ptyas_ relinquished his hold, and manifested uneasiness. Then
the glass shade was raised a trifle, and instantly away ran the rat;
but the snake was after it like a flash, caught it, and glided away
swiftly, with head erect and the rat in its mouth.
At one of the Davis lectures at the Zoological Gardens, a fine Rat
snake in the Society’s collection was exhibited, and was permitted to
be handled by a favoured few. To hold it _still_ was not possible,
for the creature glided through the hand, and entwined itself about
one as if a dozen snakes had you in possession. It was very tame, and
accustomed to be handled by the keeper, whose especial pet it was;
otherwise _Ptyas_ is a powerful snake, and quite capable of strangling
you should it take a fancy to constrict your neck. On another occasion
this same snake constricted my arm sufficiently to make my fingers
swell; but that was not so much in anger as for safety, because it
did not like to be fettered in its movements, or to be somewhat
unceremoniously examined. A younger and less tame specimen tried to
bite me, and squeezed my fingers blue by constricting them.
There is no circumventing these ‘lithe and elegant beings.’ They will
get into your pocket, or up your sleeve; and while you think you have
the head safely in your hand, the whole twelve feet of snake will have
glided through, and be making its way to the book shelves, or where you
least expect to see it.
When frequently handling the young constrictors, one has been able
to _feel_ as well as to observe the action of the ribs. As they pass
through the hand, you feel them expanded, so as to present a flatter
under surface. In _Ptyas_ the back is remarkably keeled when crawling,
a section of his body presenting the form of the middle diagram given
below.
[Illustration]
Schlegel describes the forms which the bodies of various snakes assume
in swimming, climbing, clinging, etc. Sometimes they are laterally
compressed, at others flattened. The three figures above are on a much
reduced scale, but give an idea of the sections of three different
snakes, though each snake is capable of several such changes of form.
When snakes climb against the glass of their cages, you may easily
discern the flattening of their bodies. In this action there seems to
be a compressing power, any hold of the scutæ against a polished plane
being, of course, impossible; yet without holding they seem to cling;
and the ribs advance in wave-like intervals just the same, with an
intermediate space at rest until in turn the wave is there and passes
on, while from an anterior portion another wave approaches, and so on.
Yet the _compressure_ strikes one forcibly. There is also the evident
support of the tail in a large python thus crawling to the very top of
his cage.
Mr. Gosse observed the dilatation and flattening of the body in the
climbing snakes, and that they had no more difficulty in gliding up a
tree or a wall in a straight line than on the ground. In the _Anecdotes
of Serpents_, revised for the Messrs. W. & R. Chambers, of Edinburgh,
in 1875, from the tract by the late John Keast Lord, I also recorded my
observations on this peculiarity.
Some young Jamaica boas crawled to the top of their cage as soon as
they were born. I saw them the same day; _held_ them, as well as it
was possible to hold threads of quicksilver; _felt_ them, too, for
the exceedingly juvenile constrictors tied up my fingers cleverly. So
did some young boa constrictors, born alive at the Gardens, June 30,
1877. They were from fifteen to twenty inches in length, and had teeth
sufficiently developed to draw blood from Holland’s hand, showing fight
and ingratitude at the same time. They were exceedingly active, and fed
on young mice, which they constricted instinctively. One of them, known
as ‘Totsey,’ subsequently _hung_ for her portrait, as on p. 201.
In vol. xx. of _Nature_, p. 528, is a very clever paper on the
progression of snakes, by H. F. Hutchinson, who has evidently
observed them closely. He arrives at the conclusion that they have
three different modes, viz. ‘on smooth plane surfaces by means of
their rib-legs;’ ... ‘through high grass by rapid, almost invisible,
sinuous onward movement, like swimming;’ in climbing straight walls
or ascending smooth surfaces by creating a vacuum with the ventral
scales. He reminds us that cobras, kraits, the rat snake, and other
slender and active kinds are constantly found on house roofs, walls,
straight smooth trees, etc., and asks how they got there. He has seen
the ‘abdominal scales creating a vacuum like the pedal scales of house
lizards.’ He put some active little snakes on the ground, where there
was no hold for the scutæ, and they ‘flew about in all directions.’ He
saw that they moved on by these quick, sinuous curves—‘rapid wriggles.’
In company with my esteemed friend, Mr. Robert Chambers of Edinburgh,
we made similar experiments by placing some of the smooth-scaled,
active snakes on a boarded floor. Being extremely wild, they displayed
their anger and skill to perfection, and literally _swam_ along,
scarcely touching the floor, and so swiftly that we had difficulty in
pursuing and securing them again. Some very young _Tropidonoti_ when
disturbed flew or ‘swam’ about their cage in the same manner. We also
saw pythons climb up a window-frame, and a corner of the room where no
visible hold could be obtained; and after the example of Sir Everard
Home, we allowed the reptiles to crawl over our hands, when we could
feel the expansion and flattening of the body by the spreading of the
ribs. I incline to agree, therefore, with the writer in _Nature_, that
there is a sort of vacuum created by the ventral scales. Dr. Stradling
observed that on occasions of retreat, some snakes move in such rapid
and ever-varying sinuations as to baffle you completely when you
attempt to lay hold of them; the part you thought to grasp is gone.[69]
Such are the movements of _Pituophis_ and of _Echis_ (p. 151).
At the risk of being tedious, a few more words must be added on this
subject of progression, because we so constantly see it asserted that
snakes ‘move with difficulty over smooth surfaces.’ Their actions have
not excited sufficient attention and study. Have you ever watched them
moving about in their bath at the Zoological Gardens? The motions of
a python once particularly struck me. The earthenware pan was smooth
polished ware, and with enough water in it to render it smoother, if
that be possible. The reptile was not swimming, for the thicker part
of its body was not even wholly submersed. The pan was too shallow
for that, and too small to permit of any portion of the python being
fully extended. It moved in ever-varying coils and curves, yet with
the greatest ease, its head slightly raised, so that the nostrils and
mouth were out of water. It seemed to be enjoying its bath, as it
actively glided, turned, and curved in that wonderful fashion which
Ruskin described as ‘a bit one way, a bit another, and some of him not
at all.’ There could be no hold for the scutæ in this case, nor could
I detect any action of the ribs as in crawling over a less smooth
surface. The creature seemed to move by its easy sinuations, and with
no more effort than you see in the fish at an aquarium. Perfectly
incomprehensible is this lax and leisurely movement in shallow
water. Even the inert little slow-worm astonishes us by its physical
achievements, which will be duly described in its especial chapter.
But among the most characteristically active are the small and slender
tree snakes, the _Dryadidæ_ and _Dendrophidæ_, mostly of a brilliant
green. These and the Whip snakes are exceedingly long and slender,
the tails of many of them very gradually diminishing to a fine and
attenuated point. Some of them are closely allied to the lizards, and
skim and dash through the foliage with a scarcely perceptible weight.
These are the true acrobats, full of gracile ease and activity. Many
are over four feet in length, and not much thicker than a pencil.
They are found in the hot countries of both hemispheres. The Siamese
call some of them ‘sunbeams,’ from their combination of grace and
splendour, and in Brazil some have the brilliant tints of the
humming-birds. These little creatures in your hand feel like soft,
fine, satin cords endowed with life.
Dr. Wucherer, writing from Brazil, enthusiastically declared that he
was always delighted to find one of them in his garden. He discovered
them coiled in a bird’s nest, their body of two feet long occupying a
space no larger than the hollow of your hand. ‘In an instant they dart
upwards between the branches and over the leaves, which scarcely bend
beneath their weight. A moment more, and you have lost them.’[70]
Krefft, of Australia, had some of the active snakes, which were
confined in an empty room, but one day could not be found. At last they
were discovered upon the moulding of a door, nine feet from the floor!
They must have climbed up the smooth wood-work in their own mysterious
fashion.
Ere concluding this chapter, one slight exception to the extremely
‘simple’ spinal column must be named. This is that certain families,
more nearly allied to the lizards, or most far removed from the vipers,
have rudiments of pelvic bones, or those which in bipeds connect the
legs with the trunk. In a few families there is even a pair of these
rudiments externally, though only in the form of a spur or claw, as
seen in the boa constrictor, the pythons, and some of the blindworms,
and usually more developed in the male.
There is, however, the true skeleton of a claw beneath the skin,
composed of several bones, and presenting somewhat the form of a bird’s
claw, hinting at the common ancestry between snakes and lizards. These
spurs, though mere vestiges of limbs, must still be of some use to the
large constrictors when climbing trees and hanging from the branches.
They are found in the boa, python, eryx, and tortrix, four groups
which approach the lizard characteristics; also in _Boa aquatica_, the
anaconda.
[Illustration]
[Illustration]