Snakes

Name: Snakes
Brand: Books on Demand
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Catherine Cooper Hopley(Autor*in)

Books on Demand (Verlag)

1. Auflage

Erschienen am 29. Oktober 2018

633 Seiten

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CHAPTER I.

SEEING A SNAKE FEED.
IN any person who for the first time witnesses a snake with prey just captured, the predominant feeling must be one of surprise at the seemingly unmanageable size of the animal it has seized; and he probably exclaims to himself, or to his companion, as we did on the occasion described in the introduction, 'What will he do with it?' Let us again take our common ring snake, Coluber natrix , that ate a frog for our edification; only, in the present instance, instead of seeing a tame snake in a private residence at Chelsea, we will suppose ourselves to be watching one on the banks of a stream in fine summer weather. A slight movement in the grass causes us to turn our eyes towards the spot, and we are just in time to see the quick dash, and the next instant a recalcitrant frog held aloft in the jaws of a snake that with elevated head glides up the bank. Coluber's head is no bigger than a filbert, and the frog is nearly full grown, its body inflated to twice its original size, and its legs, of impracticable length and angles, kicking remonstrantly.
' How in the world is the snake going to manage it?' again you exclaim, and your amazement is not exceptional. It is what has been witnessed and heard weekly in London when the public were admitted to the Reptilium on feeding days, and it is what the reader will recall in his own case when first informed that a snake was going to swallow that monstrous mouthful undivided.
In the present instance, the injury to froggie's feelings thus far partakes more of moral than of physical pain, for the grasp of the snake is not violent, and he finds that the more he struggles the more he injures himself. Yet he kicks and struggles on, at thus being forcibly detained against his will. In the mouth of the snake he is as proportionately large as the shoulder of mutton in the jaws of the dog that has just stolen it from the butcher's shop. How do the canines manage unwieldy food? The dog can tackle the joint of meat, big though it be, because he has limbs to aid him, and he was prepared for emergencies before he stole it. He knew of a certain deserted yard up a passage close by, and of some lumber stacked there; he watched his opportunity, and is off to his hiding-place; and once hidden behind the lumber, he settles down quietly with his ill-gotten dinner firmly held between his fore-paws, while, with eyes and ears on the alert, he gnaws away.
The snake, no doubt, knows of a hole in the bank, or in a hollow tree, in which he can hide if alarmed; but he cannot set his frog down for one instant, nor can he relax his jaws in the slightest degree, or his dinner hops away, and he has to pursue it, or wait for another frog, when the same thing may happen again. He has only his teeth to trust to, and these have all the work of paws and claws, and nails and talons, to accomplish, while yet, not for one instant, must they relinquish their hold.
' Besides!-how much too big that frog is for Coluber's small mouth!' And we continue to gaze in wonderment, filled with amazement that brings us to the bookshelves, to endeavour to comprehend the phenomenon. Not, however, until we have seen the end of that frog on the banks of the stream, where the reader is supposed to be waiting.
First, let me explain that in the manner of feeding, snakes may be divided into three classes, viz. those that kill their prey by constriction or by smothering it in the coils of their body; those that kill by poison; and some smaller kinds, which, like the ring snake, eat it alive-the latter a quick process, which may also be said to be death by suffocation. Our little Coluber is in a spot where we can watch it easily; so we keep rigidly still, and soon perceive that though the snake just now had hold of froggie's side, he now has the head in his mouth. How can this be? and how has he managed to shift it thus, almost imperceptibly, while seeming to hold it still? Now the head begins to disappear, and the snake's jaws stretch in a most distorted fashion, as if dislocated; its head expands out of all original shape, while slowly, slowly, the frog is drawn in as if by suction. Now its legs are passive; they no longer kick right and left, but lie parallel, as by degrees they also vanish, and only the four feet remain in sight. These presently have been sucked in, and the skin of the snake is stretched like a knitted stocking over the lump which tells us just how far down Coluber's neck the frog has reached. Gradually the lump gets farther and farther down, but is less evident as it reaches the larger part of the body. The snake remains still for a few moments till his jaws are comfortably in place again; then he yawns once or twice, and finally retires for his siesta, and we to the bookshelves.
' Snakes work their prey down through the collapsed pharynx,' says Günther. That is, the muscles of the throat seize upon what is presented to them, and do their part, as in other animals. Only, in most other animals there is the action of swallowing, one mouthful at a time; whereas in serpents the action is continuous, the throat going on with the work begun by the teeth, which in a snake is only grasping and working the food in with a motion so gradual as to simulate suction. The reason why the head and jaws have been so enormously stretched and distorted, is because all the bones are, in common language, loose ; that is, they are not consolidated like the head-bones of higher animals, but united by ligaments so elastic as to enable them to separate in the way we have seen. This extends to the jaws, and even to the palate, which is also armed with teeth, two rows extending backwards. The lower jaw or mandible being extremely long, the elastic ligament by which the pair of bones is connected in front, forming the chin, enables them to separate widely and move independently. This is the case in a lesser degree with the palate bones, and the upper jaw-bones, all six being furnished with long, fine, recurved, close-set teeth, adapted for grasping and holding , but not for dividing or for mastication in any way.
For, as we have seen, if a snake were to open its mouth one moment for the purpose of what we call biting , the prey would escape. In addition to a very unusual length, the lower jaw is joined to the skull by an extra bone,-one which is not found in mammals, but only, I think, in birds,-a long 'tympanic' bone, which forms an elbow, and permits of that wide expansion of the throat necessary for the passage of such large undivided prey.
The illustration of the skeleton of a cobra, on p. 33, will enable the student to distinguish the principal head-bones. There is so much similarity of construction throughout the whole ophidian families that a cobra is chosen here, because the unusually long anterior ribs which form the hood can be observed, and the expansion of which is described elsewhere. The longer teeth in the upper jaw are here fangs; the inclination of the other rows of teeth and the bones sufficiently illustrate those of the non-venomous kinds generally, such as the little ring snake that has just swallowed his frog. A few of the larger constricting snakes possess an additional bone-an intermaxillary in front between the upper jaws, very small, yet sometimes furnished with two or four teeth, thus facilitating the expansion of the jaws as well as the retention of the food.
It is this adaptive development of head-bones that enabled Coluber natrix to turn his frog round to a more convenient position, and then draw it into his mouth so gradually that we scarcely comprehended how it disappeared. The six rows of small teeth form six jaws so to speak, each one of which advanced a very little, while the other five were engaged in holding firmly. In those largest pythons which have the little bone in front between the two upper jaw-bones (intermaxillary) we may say there are seven jaws. As those gigantic snakes have to deal with proportionately large and strong prey, they are thus enabled to retain and manage it.
In the graphic language of Professor Owen let me recapitulate.
The mouth can be opened laterally or transversely, as in insects, as well as vertically, as in other vertebrates. The six jaws are four above and two below, each of which can be protruded or retracted independently of the others. 'The prey having been caught and held, one jaw is then unfixed by the teeth of that jaw being withdrawn and pushed forward, when they are again unfixed farther back upon the prey; another jaw is then unfixed, protruded, and re-attached, and so with the rest in succession. This movement of protraction, being almost the only one of which they are susceptible, while stretched apart to the utmost by the bulk of the animal encompassed by them: and thus by their successive movements, the prey is slowly introduced into the gullet.' [3]

Skeleton of a Cobra (from Owen's Anatomy of the Vertebrates ).
This working of the jaws would be almost imperceptible excepting to a very close observer. In the lower jaw-bones the independent action can be more readily perceived and is often very grotesque, one side of the mouth opening while the other is closed, conveying the idea of the reptile making grimaces at...

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