All can move or use each of the six jaws, or any two, three, or more of them independently, as we observed in feeding, some of the six holding the prey while others move on. Some writers have conveyed the idea that there is a regular alternation and even rotation of the jaws in feeding, No. 1, 2, and so on in succession till all the six have moved, and then No. 1 in its turn again; but observation inclines me rather to decide that there is no other rule than the feeder’s individual convenience, according to what its teeth may be grasping, any more than there is in other creatures that without reflection or intent, and not strictly in turn, eat now on one side of the mouth and now on the other (except in the case of some poor mortal with the toothache, when, having only the two jaws, his distressful efforts are chiefly directed towards relieving that side of its ordinary duties). Snakes, for aught we know, may have the toothache: loose teeth they frequently have; they suffer from gum and mouth affections too, and no doubt can at such times relieve a whole jaw of its work. In all true snakes the teeth are long, conical, and curved: not planted perpendicularly, but directed backwards; these long, fine, claw-shaped instruments presenting a formidable obstacle against the retreat of a creature once seized by them. Their arrangement is a species of trap, like the wires of a mouse-trap: to enter being easy enough, but to escape against the spikes being impossible. All snakes renew their teeth throughout life. Except fishes, therefore, no creatures are so abundantly supplied with teeth as are the Ophidia. On account of this continual loss and replacement of teeth, the number is rarely so fixed and determinate as to be characteristic of the species. Probably no two snakes, not even brothers and sisters of the same brood, may possess precisely the same number of teeth at a given age; because they are so easily loosened and lost, that the normal number might rarely occur in all the members of the same family at the same time. In the scientific language of Rymer Jones, ‘the facility for developing new tooth germs is unlimited, and the phenomena of dental decadence and replacement are manifested in every period of life.’