« VorigeDoorgaan »
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 fese, and where it incumbers nothing.
V. The great mechanical variety in the figure of the muscles may be thus stated. It appears to be a fixed law, that the contraction of a muscle shall be towards its centre. Therefore the subject for mechanism on each occasion is, so to modify the figure, and adjust the position, of the muscle, as to produce the motion required, agreeably with this law. This can only be done by giving to different muscles, a diversity of configuration, suited to their several offices, and to their situation with respect to the work which they have to perform. On which account we find them under a multiplicity of forms, and attitudes; sometimes with double, sometimes with treble tendons, sometimes with none; sometimes one tendon to several muscles, at other times one muscle to several tendons. The shape of the organ is susceptible of an incalculable variety, whilst the original property of the muscle, the law and line of its contraction, remains the fame; and is simple. Herein the muscular system may be faid to bear a perfect resemblance blance to our works of art. An artist does not alter the native quality of his materials, or their laws of action. He takes these as he finds them. His skill and ingenuity are employed in turning them, such 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 ease! How many more, to be vigorous and active! Yet vigor and activity are, in a vast plurality of instances, preserved in human bodies, notwithstanding that they depend upon so great a number of instruments of motion, and notwithstanding that the desect or disorder- sometimes of a very small instrument, of a single pair, for instance, out of the four hundred and forty-six muscles which are employed, may be attended with grievous inconveniency. There is piety and good sense in the following observation taken out of the Religious Philosopher. "With much compassion," fays this writer, "as well as astonishment at the goodness of our loving Creator, have I considered the fad state of a
certain certain gentleman, who, as to the rest, was in pretty good health, but only wanted the use of these two little muscles that serve to lift up the eyelids, and so had almost lost the use of his fight, being forced, as long as this desect lasted, to shove up his eyelids every moment with his own hands!" In general we may remark how little those, who enjoy the perfect use of their organs, know the comprehensiveness of the blessing, the variety of their obligation. They perceive a result, but they think little of the multitude of concurrences and rectitudes which go to form it.
Beside these observations, which belong to the muscular organ as such, we may notice some advantages of structure which are more conspicuous in muscles of a certain class or description than in others. Thus,
I. The variety, quickness, and precision, of which muscular motion is capable, are seen, I think, in no part so 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 position, and the perfect exactness. Each syllable of articulated found requires for its utterance a specific action of the 4 9 tongue, tongue, and of the parts adjacent to it. The disposition 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 sight; infomuch that curious persons have availed themselves of this circumstance to teach the deaf to speak, and to understand what is said by others. In the fame person, and after his habit of speaking is formed, one, and only one, position of the parts, will produce a given articulate sound correctly. How instantaneously are these positions assumed and dismissed; 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 diversified. I believe also that the anatomy of the tongue corresponds with these observations upon its activity. The muscles of the tongue are so numerous, and so implicated with one another, that they cannot be traced by the nicest dissection nevertheless, which is a great pe section of the organ, neither the number, nor the complexity, nor what might seem to be, the entanglement ment of its fibres, in any wise impede its motion, or render the determination or success of its efforts uncertain.
I here intreat the reader's permission to step a little out of my way to consider the parts, os the mouth in some of their other properties. It has been faid, and that by an eminent physiologist, that, whenever nature att mpts to work two or more purposes by one instrument, she does both or all impersectly. Is this true of the tongue regarded as an instrument of speech, and of taste; or regarded as an instrument of speech, of taste, and of deglutition? So much otherwise, that many persons, that is to fay, nine hundred, and ninety-nine persons out of a thoufand, by the instrumentality of this one organ, talk, and taste, and swallow, very well. In fact the constant warmth and moisture of the tongue, the thinness of the skin, the papillae upon its surface, qualify this organ for its office of tasting, as much as its inextricable multiplicity of fibres do for the rapid movements which are necessary to speech. Animals which feed upon grafs, have their tongues covered with a 4 perforated