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The same process may be witnessed in ordinary snakes, for all serpentsswallow their prey whole. There is no mastication to facilitate degluti-tion. Their upper jaws are loosely connected to the head, so that themouth can be opened very wide, to admit larger animals tban the size ofthe serpents would lead one to suppose.
Such examples, it must be admitted, are not very familiär ones ; butthere is an experiment not much unlike them, that most people have wit-nessed, and not a few perform it in their own persons almost daily. Inevery age people have been fond of oysters, and numbers of our citizensoften luxuriate on a finer and larger species than those which Romanepicures formerly imported from Britain . Now, when a gentlemanindulges in this food in the ordinary way, he affords a striking Illustrationof the pressure of the atmosphere. A large one is opened by the restau-rateur, who also loosens the animal from its shell, and presents it on onehalf of the latter. The imitator of the boa then approaches his lips to thenewly slain victim, and when they come in contact with but a portion ofit, he immediately dilates his ehest as in the act of Inspiration, when theair, endeavoring to rush into his mouth to inflate the thorax, drives theoyster before it, and with a velocity that is somewhat alarming to aninexperienced spectator. If any one should doubt this to be effected byatmospheric pressure, let him fully inflate his lungs previous to attemptingthus to draw an oyster into his mouth, and he will find as much difficultyto accomplish it as to smoke a pipe or a cigar with his mouth open.
This philosophical mode of transmitting oysters to the stomach is iden-tical in principle with that proposed by Guerricke and Papin, for shootingbullets “ by the rarefaction of air.” a A leaden ball was fitted into thebreech of a gun-barrel, and the end being closed, a vaeuum was producedin front of it; after which the atmosphere was allowed to act suddenly onthe ball, when it was driven through the tube with the velocity of a thou-sand feet in a second. Just so with the oyster : it lays inertly at theorifice of the devourer’s mouth—a partial vaeuum is made in front of itby the act of respiration, and on dilating the ehest, the atmosphere drivesit in a twinkling down the natural tube in the throat—though, to be sure,with a velocity somewhat less than that of bullets through Papin’s gun.
When two substances, impervious to air, are fitted so close as to excludeit from between them, they are held together by its pressure on theirOutsides, and with a force proportioned to the extent of the surfaces incontact. Pieces of metal have been ground together so close as to bethus United. Two pieces of common window-glass dipped in water, andpressed together, are separated with difficulty ; because the water servesto expel the air, and prevent its entrajice. Glass grinders are frequentlyinconvenienced by this circumstance. If two plates of glass were per-fectly plane and smooth, so as wholly to exclude the air from betweenthem, they would become United as one. We have heard or read of in-stances when they have become actually one, and were cut by a diamondas an ordinary single plate.
The boys’ ‘ sucker,’ or ‘ cleaver,’ a circular piece of wet and thickleather, about the size of a dollar, is another Illustration. This, whenpressed against a smooth paving or other stone, of five or ten Ibs. weight,may be used to raise it, by means of a String attached to the centre.If one of these, four inches in diameter, were applied to the cranium of abald-headed gentleman, he might be elevated and suspended by it. Dr.Arnott recommends them to elevate depressed portions of fractured skulls,
Phil. Trans. Abridg. vol, i, 496.