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changed its line of direction, is inserted into the inner part of the chin: by which device, viz. the turn at the loop, the action of the muscle (which in all muscles is contraction) that before would have pulled the jaw up, now as necessarily draws it down. w The mouth," faith Heister, "is opened by means of this trochlea in a most wonderful and elegant manner."
II. What contrivance can be more mechanical than the following, viz. a flit in one tendon to let another tendon pass through it? This structure is found in the tendons which move the toes and fingers. The long tendon, as it is called, in the foot, which bends the first joint of the toe, passes through the short tendon which bends the second joint; which course allows to the sinew more liberty, and a more commodious action than it would otherwise have been capable of exerting. There is nothing, I believe, in a silk or cotton millI in the belts, or straps, or ropes, by which motion is communicated from one part of the machine to another, that is more artificial, or more evidently so, than this perforation.
* Chef. Anat. p. 93. 119.
III. The next circumstance which I shall mention, under this head of muscular arrangement, is so decisive a mark of intention, that it always appeared to me, to supersede, in some measure, the necessity of seeking for any other observation upon the subject: and that circumstance is, the tendons, which pass from the leg to the foot, being bound down by a ligament at the ancle. The foot is placed at a considerable angle with the leg. It is manifest, therefore, that flexible strings, passing along the interior of the angle, if left to themselves, would, when stretched, start from it. The obvious preventative is to tie them down. And this is done in fact. Across the instep, or rather just above it, the anatomist finds a strong ligament, under which the tendons pass to the foot. The effect of the ligament as a bandage, can be made evident to the senses; for if it be cut, the tendons start up. The simplicity, yet the clearness of this contrivance, its exact resemblance to established resources of art, place it amongst the most indubitable manisestations of design with which we are acquainted.
There is also a further use to be made of the present example, and that is, as it pre4 cisely cisely contradicts the opinion, that the parts of animals may have been allformed by what is called appetency, i. e. endeavour, perpetua*ed,^and imperceptibly working its effect, through an incalculable series of generations. We have here no endeavour, but the reverse of it; a constant renitency and reluctance. The endeavour is all the other way. The pressure of the ligament constrains the tendons; the tendons react upon the pressure of the ligament. It is impossible that the ligament should ever have been generated by the ex rcise of the tendon, or in the course of that exercise, forasmuch as the force of the tendon perpendicularly resists the fibre which confines -it, and is constantly endeavouring, not to form, but to rupture and displace, the threads of which the ligament is composed.
Keill has reckoned up, in the human body, four hundred and-forty six muscles, dissectible and describable; and hath assigned an use to every one of the number. This cannot be all imagination.
Bishop Wilkins hath observed from Galen, that there are, at least, ten several qualifica
tions to be attended to in each particular muscle, viz. its proper figure, its just magnitude, its fulcrum, its point of action supposing the figure to be fixed, its collocation with respect to its two ends the upper and the lower, the place, the position of the whole muscle, the introduction into it of nerves, arteries, veins. How are things, including so many adjustments, to be made; or, when made, how are they to be put together, without intelligence? 1
I have sometimes wondered, why we are not struck with mechanism in animal bodies, as readily and as strongly as we are struck with it, at first sight, in a watch or a mill. One reason of the difference may be, that animal bodies are, in a great measure, made up of soft, flabby, substances, such as muscles and membranes; whereas we have been accustomed to trace mechanism in sharp lines, in the configuration of hard materials, in the moulding, chiseling, and filing into shapes, such articles as metals or wood. There is something therefore of habit in the case: but it is sufficiently evident, that there can be no proper reason for any distinction of the sort.
Mechanism Mechanism may be displayed in the one kind of substance, as well as in the other.
Although the few instances we have selected, even as they stand in our description, are nothing short perhaps of logical proofs of design, yet it must not be forgotten, that, in every part of anatomy, description is a poor substitute for inspection. It was well faid by an able anatomist*, and faid in reference to the very part of the subject which we have been treating of, " Impersecta hæc musculorum destriptio, non minus arida est legentibus, quara inspectantibus fuerit jucunda eorundem præparatio. Elegantiflima enim mechanices artificia, creberrime in illis obvia, verbis nonnisi obscure exprimuntur; carnium autem ductu, tendinum colore, insertionum proportione, et trochlearium distributione,oculis exposita, omnem superant admirationem."
* Steno in Bias. Anat. Animal, p. 2. c. 4.