The colour of the Deirodon is of a brightish or yellowish brown, very minutely spotted with white. Such few true teeth as some individuals may possess are extremely small and conical, discovered only towards the angle of the mouth.
Dr. Andrew Smith first examined a specimen in 1829, when he found that the gular teeth commence exactly 2-1/4 inches behind the apex of the lower jaw, and penetrate the œsophagal canal through small holes in its tunics, and that each point is armed with enamel. He had observed that the living specimens which he had in captivity always, when feeding, retained the egg stationary about two inches from their head, and while there, used great efforts to crush it. Dissecting a specimen in order to investigate this strange action, he discovered the gular teeth just where the egg had stopped, and which, he felt satisfied, had assisted in fixing it there, and also in breaking the shell when subjected to the muscular action of the surrounding parts. The gular teeth are developed in very young Deirodons.
Dr. Smith saw that the broken shell was ejected, while the fluid contents were conveyed onwards; but this may have been an exceptional case, because by a snake in health egg-shells are easily digested. Probably those snakes watched by Dr. A. Smith being captives, and presumably not altogether as happy and healthy as in their sylvan homes, found the shells too much for them, and so ejected them; as the cobras above described disgorged the stolen eggs. This habit of disgorging food appears to be sometimes voluntary.
Snakes have been known to pass the egg through their body entire, but this also must be owing to an abnormal state of health or of habit, as the strong juices of the stomach, which can convert even bones and horn to nutriment, ordinarily dissolve an egg-shell.
Throughout nature we find that, whatever the habits of the creature may be, its structure and capacities are adapted to it. Every need is, as it were, anticipated in the process of development; and wherever, as in this harmless little tree snake, we find a departure from general rules, it is because some especial requirements are met, and in order that the creature may be the better prepared for the struggle for existence. In the present example we find a marvellous adaptation of spine bones to dental purposes; how many ages it has taken to develop them we cannot conjecture. All we know is that these spinal projections are just the sort of teeth that the egg-swallower requires, and that its natural teeth are gradually becoming obsolete from disuse.
A writer who was quoted at some length in the Zoologist for 1875, and in several other contemporary journals, stated that some snakes ‘suck out the contents of hen’s eggs by making a hole at the end.’[12]
We are not told with what instrument these evidently scientific serpents punctured the shell. Some skill is required, as schoolboys give us to understand, to prick an egg-shell without breaking it; and even when the hole is bored, additional care is required to suck out the contents. How a snake could first grasp firmly, and then puncture a fowl’s egg, is incomprehensible; how the sucking process is achieved is still more so. We can understand that a snake which discovered a broken egg might seem to lap some of the contents, because, as we shall by and by show, the tongue habitually investigates, and is immediately in requisition under all circumstances. But to lap up an egg would be a very slow process for so slender an instrument. One is reminded of the dinner which Sir Reynard invited his friend the Stork to partake with him.
While still marvelling over these South African egg-suckers, I watched some lizards with a broken egg in their cage. Their tongues were long, thin, blade-like, and bifid, much better adapted for the purpose of lapping than that of a snake, yet stupidly slow and inefficient was this ribbon-like tongue. The lizards threw it out, spatula-fashion, into the midst of the pool of egg which was spreading itself over the floor, and caught whatever of the fluid adhered to it. Had the lizards possessed lips adapted for such a purpose, and, in addition, intelligence enough to ‘suck,’ they might have drawn some of the cohesive mass into their throats, but they only obeyed their instinctive habit of lapping. Snakes would do the same. Their habit is to moisten the tongue in lapping; and I fear we must not place too much credence in the exceptional intelligence of that South African egg-sucker, but rather regret the loose account which conveys so erroneous an impression. I watched those lizards for many minutes, and decided that the egg would be dried up long before it could be consumed by lizard-lapping.
The tongue of a snake is undoubtedly an important and highly-developed organ. That its sensitiveness assists the smell, we have reason to believe, and possibly it possesses other faculties of which we are at present ignorant. In the case of an unbroken egg, for instance, the tongue has told the snake that there is something good inside it; and instinct immediately leads the reptile to get the awkward mouthful between its jaws, which expand just so far as to retain it safely, yet just so lightly that not one of those rows of long, sharp teeth shall penetrate the shell or fracture it in the slightest degree. How delicate must be the adjustment whereby those six jaws, all bristling with fine, needle-like teeth, grasp and yet not break the delicate shell! for, after all, an egg is a fragile substance in proportion to the size of the feeder and its muscular power.
Snakes have been known to get choked in attempting to swallow an egg, as they have also come to grief with other impediments, such as horns of cattle; but this we must attribute to their not being able to estimate their own swallowing capacities, or to some other untoward event.