the nictitating membrane over the eye. Its office is in the front of the eye; but its body is lodged in the back part of the globe, where it lies fafe, and where it incumbers nothing.

V. The great mechanical variety in the figure of the muscles may be thus ftated. It appears to be a fixed law, that the contraction of a mufcle fhall be towards its centre. Therefore the fubject for mechanifm on each occafion is, fo to modify the figure, and adjust the pofition, of the mufcle, as to produce the motion required, agreeably with this law. This can only be done by giving to different mufcles, a diversity of configuration, fuited to their feveral offices, and to their fituation with refpect to the work which they have to perform. On which account we find them under a multiplicity of forms, and attitudes; fometimes with double, fometimes with treble tendons, fometimes with none; fometimes one tendon to feveral muscles, at other times one muscle to several tendons. The shape of the organ is fufceptible of an incalculable variety, whilft the original property of the muscle, the law and line of its contraction, remains the fame; and is fimple. Herein the muscular fyftem may be faid to bear a perfect refem

blance

blance to our works of art. An artift does not alter the native quality of his materials, or their laws of action. He takes these as he finds them. His fkill and ingenuity are employed in turning them, fuch as they are, to his account, by giving to the parts of his machine a form and relation, in which these unalterable properties may operate to the production of the effects intended.

VI. The ejaculations can never too often be repeated, How many things must go right for us to be an hour at eafe! How many more, to be vigorous and active! Yet vigor and activity are, in a vaft plurality of inftances, preferved in human bodies, notwithstanding that they depend upon fo great a number of inftruments of motion, and notwithstanding that the defect or diforder fometimes of a very fmall inftrument, of a fingle pair, for instance, out of the four hundred and forty-fix muscles which are employed, may be attended with grievous inconveniency. There is piety and good fenfe in the following obfervation taken out of the Religious Philofopher. "With much compaffion," fays this writer, "as well as astonishment at the goodness of our loving Creator, have I confidered the fad ftate of a

certain

certain gentleman, who, as to the rest, was in pretty good health, but only wanted the ufe of these two little muscles that ferve to lift up the eyelids, and fo had almoft loft the ufe of his fight, being forced, as long as this defect lafted, to fhove up his eyelids every moment with his own hands!" In general we may remark how little thofe, who enjoy the perfect use of their organs, know the comprehenfivenefs of the bleffing, the variety of their obligation. They perceive a refult, but they think little of the multitude of concurrences and rectitudes which go to form it.

BESIDE these observations, which belong to the mufcular organ as fuch, we may notice fome advantages of ftructure which are more confpicuous in muscles of a certain clafs or defcription than in others. Thus,

I. The variety, quickness, and precision, of which mufcular motion is capable, are feen, I think, in no part fo remarkably as in the tongue. It is worth any man's while to watch the agility of his tongue; the wonderful promptitude with which it executes changes of pofition, and the perfect exactnefs. Each fyllable of articulated found requires for its utterance a specific action of the tongue,

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How in

tongue, and of the parts adjacent to it. The difpofition and configuration of the mouth, appertaining to every letter and word, is not only peculiar, but, if nicely and accurately attended to, perceptible to the fight; infomuch that curious perfons have availed themfelves of this circumftance to teach the deaf to fpeak, and to understand what is faid by others. In the fame perfon, and after his habit of speaking is formed, one, and only one, pofition of the parts, will produce a given articulate found correctly. stantaneously are thefe pofitions affumed and difmiffed; how numerous are the permutations, how various, yet how infallible! Arbitrary and antic variety is not the thing we admire; but variety obeying a rule, conducing to an effect, and commensurate with exigencies infinitely diverfified. I believe also that the anatomy of the tongue corresponds with these observations upon its activity. The muscles of the tongue are fo numerous, and fo implicated with one another, that they cannot be traced by the niceft diffection nevertheless, which is a great perfection of the organ, neither the number, nor the complexity, nor what might feem to be, the entangle

ment

ment of its fibres, in any wife impede its motion, or render the determination or fuccefs of its efforts uncertain.

I here intreat the reader's permiffion to ftep a little out of my way to confider the parts of the mouth in fome of their other properties. It has been faid, and that by an eminent phyfiologist, that, whenever nature att mpts to work two or more purposes by one inftru ment, she does both or all imperfectly. Is this true of the tongue regarded as an instrument of speech, and of tafte; or regarded as an inftrument of speech, of tafte, and of deglutition? So much otherwise, that many perfons, that is to fay, nine hundred and ninety-nine perfons out of a thousand, by the inftrumentality of this one organ, talk, and taste, and fwallow, very well. In fact the conftant warmth and moisture of the tongue, the thinness of the skin, the papillæ upon its furface, qualify this organ for its office of tafting, as much as its inextricable multiplicity of fibres do for the rapid movements which are neceffary to fpeech. Animals which feed upon grafs, have their tongues covered with a perforated

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