Moreover, the mind, in this corporeal system, must be endued with the power of moving from place to place; that she may have intercourse with a variety of objects; that she may fly from such as are disagreeable, dangerous, or hurtful; and pursue such as are pleasant and useful to her. And accordingly she is furnished with limbs, with muscles and tendons, the instruments of motion, which are found in every part of the fabric where motion is necessary.
But to support, to give firmness and shape to the fabric; to keep the softer parts in their proper places; to give fixed points for, and the proper directions to its motions, as well as to protect some of the more important and tender organs from external injuries, there must be some firm prop-work interwoven through the whole. And in fact, for such purposes the bones are given.
The prop-work is not made with one rigid fabric, for that would prevent motion. Therefore there are a number of bones.
These pieces must all be firmly bound together, to prevent their dislocation. And this end is perfectly well answered by the ligaments.
The extremities of these bony pieces, where they move and rub upon one another, must have smooth and slippery surfaces for easy motion. This is most happily provided for, by the cartilages and mucus of the joints.
The interstices of all these parts must be filled up with some soft and ductile matter, which shall keep them in their places, unite them, and at the same time allow them to move a little upon one another; these purposes are answered by the cellular membrane, or edipose substance.
There must be an outward covering over the whole apparatus, both to give it compactness, and to defend it from a thousand injuries; which, in fact, are the very purposes of the skin and other integuments.
Say, what the various bones so wisely wrought?
How was their frame to such perfection brought?
What did their figures for their uses fit,
Their numbers fix, and joints adapted knit;
And made them all in that just order stand,
Which motion, strength, and ornament, demand?
Blackmore.
Lastly, the mind being formed for society and intercourse with beings of her own kind, she must be endued with powers of expressing and communicating her thoughts by some sensible marks or signs, which shall be both easy to herself, and admit of great variety. And accordingly she is provided with the organs and faculty of speech, by which she can throw out signs with amazing facility, and vary them without end.
Thus we have built up an animal body, which would seem to be pretty complete; but as it is the nature of matter to be altered and worked upon by matter, so in a very little time such a living creature must be destroyed, if there is no provision for repairing the injuries which she must commit upon herself, and those which she must be exposed to from without. Therefore a treasure of blood is actually provided in the heart and vascular system, full of nutritious and healing particles; fluid enough to penetrate into the minutest parts of the animal; impelled by the heart, and conveyed by the arteries, it washes every part, builds up what was broken down, and sweeps away the old and useless materials. Hence we see the necessity or advantage of the heart and arterial system.