The Machine of the Human Body

1. Men have a soul and a body.

2. The body is a machine of earth which God forms on purpose to make it as similar to us as possible.

He gives its outside the color and shape of all our members, but he also puts on its inside the color and shape of our bodies.

These parts make the body walk, eat, breathe, and finally imitate all those of our functions which can be imagined to proceed from matter, and depend only on the disposition of the organs.

We see clocks, artificial fountains, mills, and other similar machines which, being made only by men, do not fail to have the power to move by themselves in many different ways.

It seems to me that I cannot imagine so many kinds of movement in this one, which I suppose to be made by the hands of God, nor attribute to it so much artifice, that you do not have reason to think that there may be even more.

I will not describe the large parts of the body such as:

• the bones
• the nerves
• the muscles
• the veins
• the arteries
• the stomach
• the liver
• the spleen
• the heart
• the brain
• and their parts

I will explain instead the small parts which are invisible because of their smallness. These small parts are known by the movements that they cause. Each of these movements serve a function.

3. The meats are digested in the stomach through the force of certain liquors.

These liquors slip between their parts, separate, agitate, and heat them just as common water does the same to quicklime, or strong water those of metals.

These liquors, brought from the heart by the arteries, become very hot.

The meats could even corrode and heat up by themselves, just as new hay does in the barn when it is squeezed before it is dry.

The agitation that the small parts of these meats receive as they heat up, combined with that of the stomach and the intestines that contain them, and with the arrangement of the small threads of which these intestines are composed, means that as they digest, they descend little by little towards the conduit through which the coarser parts of them must leave; that prevents the bran from following it.

These subtler parts of the meats are uneven and still imperfectly mixed together.

• These make up a liquor which is hollow and whitish when unmixed with blood

But a part of it mingles incontinently with the mass of blood in all the branches of the ‘portal vein’.

• This vein receives this liquor from the intestines.
• It sends this liquor to the liver then to the heart through the vena cava vein

The pores of the liver make the entering liquor more subtle so that it elaborates itself.

• It takes on its color and acquires the form of blood, just as the juice of black grapes, which is white, is converted into clear wine when it is left to ferment on the grater.

This blood in the veins leaves the liver only through one way that also leads it into the right side of the heart.

The Heart

The flesh of the heart contains in its pores one of those lightless fires of which I have spoken above, which makes it so hot and burning.

As blood enters any of the 2 chambers in it, it swells rapidly and expands. This is like what happens when you pour the milk from any animal drop by drop into a very hot vessel.

The fire in the heart dilates, warms, and subtilises the blood which falls in continuously drop by drop through a pipe of the vena cava in its right cavity from where it exhales in the lung.

From there it goes to what is called by anatomists as the vein of the lung ‘venous Yartère’ from where it is distributed to the body.

4. The flesh of the lung is so rare and soft.

It is always refreshed by the air of the breath.

The vapors of the blood come out of the right cavity of the heart and enter the flesh of the lungs to be thickened and converted into blood again.

From there, they fall drop by drop into the left cavity of the heart, where they serve as fuel for the fire in the heart.

Respiration serves only to thicken these vapors to maintain this fire.

Babies who are still in their mothers’ wombs cannot draw any fresh air by breathing. They have 2 conduits which make up for this defect:

1. One through which the blood of the vena cava passes into the vein called the artery
2. The other through which the vapors or rarefied blood of the artery called the vein are exhaled and go into the great artery