SECT.  XXXIV.  Of the Bones, and their Jointing.

Do you consider that excellent order and proportion of the limbs?  The legs and thighs are great bones jointed one with another, and knit together by tendons.  They are two sorts of pillars, equal and regular, erected to support the whole fabric.  But those pillars fold; and the rotula of the knee is a bone of a circular figure, which is placed on purpose on the joint, in order to fill it up, and preserve it, when the bones fold, for the bending of the knee.  Each column or pillar has its pedestal, which is composed of various inlaid parts, so well jointed together, that they can either bend, or keep stiff, as occasion requires.  The pedestal, I mean the foot, turns, at a man’s pleasure, under the pillar.  In this foot we find nothing but nerves, tendons, and little bones closely knit, that this part may, at once, be either more supple or more firm, according to various occasions.  Even the toes, with their articles and nails, serve to feel the ground a man walks on, to lean and stand with more dexterity and nimbleness, the better to preserve the equilibrium of the body, to rise, or to stoop.  The two feet stretch forward, to keep the body from falling that way, when it stoops or bends.  The two pillars are jointed together at the top, to bear up the rest of the body, but are still divided there in such a manner, that that joint affords man the conveniency of resting himself, by sitting on the two biggest muscles of the body.

The body of the structure is proportioned to the height of the pillars.  It contains such parts as are necessary for life, and which consequently ought to be placed in the centre, and shut up in the securest place.  Therefore two rows of ribs pretty close to one another, that come out of the backbone, as the branches of a tree do from its trunk, form a kind of hoop, to hide and shelter those noble and tender parts.  But because the ribs could not entirely shut up that centre of the human body, without hindering the dilatation of the stomach and of the entrails, they form that hoop but to a certain place, below which they leave an empty space, that the inside may freely distend and stretch, both for respiration and feeding.

As for the backbone, all the works of man afford nothing so artfully and curiously wrought.  It would be too stiff, and too frangible or brittle, if it were made of one single bone: and in such a case man could never bend or stoop.  The author of this machine has prevented that inconveniency by forming vertebræ, which jointing one with another make up a whole, consisting of several pieces of bones, more strong than if it were of a single piece.  This compound being sometimes supple and pliant, and sometimes stiff, stands either upright, or bends, in a moment, as a man pleases.  All these vertebræ have in the middle a gutter or channel, that serves to convey a continuation of the substance of the brain to the extremities of the body, and with speed to send thither spirits through that pipe.

But who can forbear admiring the nature of the bones?  They are very hard; and we see that even the corruption of all the rest of the body, after death, does not affect them.  Nevertheless, they are full of numberless holes and cavities that make them lighter; and in the middle they are full of the marrow, or pith, that is to nourish them.  They are bored exactly in those places through which the ligaments that knit them are to pass.  Moreover, their extremities are bigger than the middle, and form, as it were, two semicircular heads, to make one bone turn more easily with another, that so the whole may fold and bend without trouble.