Though there are always on an average fifty snakes in the Reptile House, and on an average each casts its coat three times a year, the visitors are for the most part much mystified about this phenomenon. A snake that had just completed a new toilet had a portion of the old slough still adhering to its tail, when a boy drew attention to it, saying, ‘Papa, that snake is all ragged and torn on its tail.’
‘Yes, my dear, it is casting its tail.’ Papa must have been reading Aristotle, who wrote: ‘Tails, also, of serpents and lizards when cut off are reproduced.’ With regard to the reproduction of their eyes, Aristotle spake more cautiously. ‘It is reported that the eyes of serpents, if dug out, will be reproduced.’ But, on the contrary, the eyes of snakes are easily injured, and not easily healed; snakes are therefore frequently seen partially blind. As need scarcely be said, only lizards ‘reproduce’ a tail that has been accidentally abridged; and the repair is after all only a boneless one. The truncated member gradually heals, and by and by a short point is again formed, but can always be recognised as a repaired, and not the original, tail; and as far as I have been able to observe, viz. for three or four months, no bone was reproduced. Probably also a snake’s tail might heal in the same way, and to a casual observer appear quite perfect; but the anatomical structure in either case would not, I imagine, be restored.
That boy was not far wrong when he said he thought the python did not know which was its own tail. At all events, it is not endowed with much external sensation, as one might judge by the way in which the rats and guinea-pigs take liberties with it. This must be owing to the thickness of the cuticle, because, as we have seen in the constricting snakes, there is keen muscular sensibility in the tail. I may cite an instance of each case. One day a young rabbit caught hold of a small python with its teeth and held firmly on. The reptile was moving across the cage, and did not appear to feel any hindrance. Indeed, being much the stronger of the two, the persistent bunny was compelled to hop along at the same pace, still holding on by its teeth. But presently, from the position of the snake, the rabbit was obliged to let go, when it next caught hold of the tip of the python’s tail, and again holding tight, hopped after the retreating reptile as if enjoying the joke. In this case I do not think the snake was conscious of the insult, as perhaps the rabbit had hold of the skin only.
On the other occasion a guinea-pig was biting a coiled and passive constrictor, Python sebœ. The snake wished to be quiet, but piggy got among its coils and worried it, hopping over it and biting its tail. The python on this, moving only the end of its tail, pushed away the guinea-pig, which soon returned to the attack. The snake again gave the little animal a caudal hint that his fidgeting was annoying; but as the guinea-pig did not take the hint, and still nibbled and teased the snake, the latter with two coils of the tail put an end to the annoyance, not once turning its head, but just tucking up its persecutor in the end of its tail as you might tuck up a parcel under your arm. The python was not hungry, and took no more notice of the offender, though thus effectually punishing the offence with the last two feet of its practical tail. Could we suppose such a quality as muscular intelligence, we might think the tails of those constricting snakes were surely endowed with it. As in other instances already described in chaps. xi. and xii., the eyes took no part in directing the movements of the snake; the whole nine or ten feet of the animal remaining passively coiled, while only the extremity of the tail exerted itself. When reptiles are in a partially torpid condition, their sensations are slow; when hibernating, they are reduced to a minimum. At such times, the creatures being half dead, they may be maimed or injured without any apparent effect. Rats have been known to attack and nibble snakes under these circumstances, and even to eat bits out of them, the snakes being at the time unconscious of injury, though possibly dying from the after effects.
A good deal of very interesting matter might be added on the economics of the reptilian ménage, the mode of ventilating and warming it, the cost of its larder, and the best means of preserving the health of the inmates. There are, besides, some incidental experiences not devoid of sensationalism in connection with snake guardianship, but my own herpetological experience does not extend beyond the keeping of pet lizards, including blindworms. I may add a word, however, in reply to some often-heard lamentations of disappointed spectators who object to the coverlets, after sometimes waiting in vain to see the snakes emerge from beneath them.
‘Those horrid blankets! Why not give the snakes moss or hay in their cages? or turf and sand and dead leaves? Much more natural for them than those woollen rugs.’
I, too, may have echoed such plaints until a better comprehension of ophidian nature showed the wisdom of what is certainly a somewhat disappointing arrangement. And those who have honoured these pages with a patient perusal, and discovered the nervous timidity and sensitiveness of these reptiles, their proneness to reject or to disgorge their food, to injure themselves or each other when molested, not to mention the danger of meddling with the venomous kinds and the easy escape of the swifter snakes, will admit the importance of providing them with such retreat and shelter as can be most speedily arranged, and which will secure the least annoyance to the terrified serpents while the keepers are doing their best to preserve order and cleanliness.
The allusion to lizards tempts me to add a word or two on the exceptional species which has lately become an inmate of our Zoological Gardens. There are certain features in it so much in common with viperine snakes, that I may be pardoned for dragging a lizard into these pages. I allude to the Heloderm (Heloderma horridum) from Mexico, presented to the Zoological Society in July 1882 by Sir John Lubbock. Its advent was an event in reptilian annals; and being surrounded by a halo of curiosity, it claims a passing notice. We have been at some pains to exonerate saurians from the evil character which our ancestors were apt to give them; but suddenly—and to the surprise of even some herpetological authorities—there comes a lizard that with one grip of his jaws caused a frog to fall dead in a moment, and a guinea-pig in three minutes, the symptoms appearing to be the same as those produced by deadly snakes. The Heloderm is ‘said’ to be furnished with poison glands in both jaws! But until a dead specimen has been further examined and described, the signification of ‘poison gland’ must be restricted. Its teeth—many and strong—are grooved with a deep furrow; its salivary glands are largely developed; and under excitement a thick, acrid secretion flows abundantly from its jaws. Yet so far as present observations enable us to form an opinion, the reptile does not use these formidable teeth to secure its prey, or even in feeding. It did not devour the victims of its bite, nor has it since killed any creature for the express purpose of eating it. Up to the date at which I write (Oct. 1882), eggs have formed its chief diet, varied by an occasional dead mouse. Now it certainly does not require deeply-grooved teeth and venomous saliva to bite raw eggs and dead mice. Nor does the noxious secretion flow continuously from its gums in repose, but abundantly so when irritated.
Though a stranger in England, this lizard was known more than two hundred years ago. Hernandez, in his Nova Animalium Mexicanum, published at Rome in 1651, described its bite as ‘hurtful, but not deadly;’ and that it was ‘more dreadful in appearance than reality.’ Its Mexican name, Acaltetepon, is (or was then) applied to all large and suspicious-looking lizards. Scorpione is its modern name. As Heloderma horridum was awarded plenty of space in the journals at the time of its arrival, full accounts of it will be found elsewhere; it is introduced here merely as one of the venomous reptiles that form the chief subjects of this chapter, and to trace its analogy with them. In its slow, stealthy movements there is the same striking contrast between the Heloderm and most other lizards, that there is between the deadly vipers and the active colubrine snakes; and the inquiry suggests itself, Can the venom elaborated in their system so act upon themselves as to produce this habitual lethargy? Drowsiness and coma are almost invariable effects of snake venom in the blood, and why is it that the deadly serpents are so constitutionally different from others? The Heloderm has a round, heavy tail, of no service to it in swimming, and short, weak fingers, ill suited to climbing; and it passes its lethargic existence on the sandy plains of Mexico, manifesting in its actions, or rather in its inactivity and stealthiness, a conscious timidity and cowardice. Motionless for hours, with an impulse to retreat if molested, but attempting to bite if angered, its noxious saliva would seem to be rather protective than aggressive. It may have formidable enemies at home; and by all we see of it here, it does not use its teeth as a means of obtaining food. In this respect, therefore, it is an exception to deadly serpents, and cannot take its venom into its stomach as they do. And, again, the remarkable development of its tongue suggests a peculiarity of food. In lapping the egg, the action of it is apparently perfected by practice; the tongue is twisted, extended, twined under, then over, now used as a shovel, a scoop, or a broom, as occasion requires. It is the very reverse of what I noticed in some other lizards feebly lapping up an egg (see p. 71), for in a most expeditious manner does Heloderm cause its raw eggs to disappear.
A word à propos of its name horridum, supposed by many to refer to its objectionable qualities. Unfortunately the word ‘horrid’ has almost entirely lost its original signification and become mere slang in English. But when Wiegmann assigned it the name of Heloderma horridum in 1829, ‘horrid’ was understood according to its original meaning, from horridus, rough, rugged, etc.; and as this reptile has a remarkable skin, dotted over with little prominences, like knobs or warts (hence its generic name, Heloderma, warty skin), there can be but little doubt as to the intention of horridum. In a communication to Knowledge (Sept. 29), I ventured to call this the ‘Warty-skinned Lizard,’ in consequence of the confused accounts of it which have appeared in print. There are several other warty-skinned or ‘tuberculous lizards.’ The specific horridus, as applied to the South American Crotalus, also signified its terrible or dreadful character, and not the ‘horrid’ which spectators apply indiscriminately to snakes and their blankets.