The bodily parts that are formed in the seed

A still more perfect knowledge of how all the parts of the body are nourished is to be had when we consider how they were originally formed from the seed.

Until now, I have been unwilling to put my views on this topic into writing, because I have not yet been able to make enough observations to test all the thoughts I have had on the matter.

I specify nothing on the shape and arrangement of the particles of the seed.

Plants, being hard and solid, can have its parts arranged and situated in a particular way which cannot be altered without making them useless.

But the situation in the case of seed in animals and humans is quite different, for this is quite fluid and is usually produced in the copulation between the two sexes, being, it seems, an unorganised mixture of two liquids, which act on each other like a kind of yeast, heating one another so that some of the particles acquire the same degree of agitation as fire, expanding and pressing on the others, and in this way putting them gradually into the state required for the formation of parts of the body.

These two liquids need not be very different from one another for this purpose.

Old dough can make new dough swell.

The scum formed on beer is able to serve as yeast for making more beer

Likewise, the seeds of the two sexes, when mixed together, serve as yeast to one another.

The first thing that happens in this mixture of seed, and which makes all the drops cease to resemble one another, is that the heat generated there – which acts in the same way as does new wine when it ferments, or as hay which is stored before it is dry – causes some of the particles to collect in a part of the space containing them, and then makes them expand, pressing against the others. This is how the heart begins to be formed.

These tiny parts then expand and continue their movement in a straight line.

Its heart has now begun to form. This resists them.

They slowly move away and go to where the brain stem will later be formed.

In the process, they displace others which move around in a circle to occupy the place vacated by them in the heart.

After the brief time needed for them to collect in the heart, these in turn expand and move away, following the same path as the former.

This results in some of the former group which are still in the same position – together with others that have moved in from elsewhere to take the place of those that have left in the meantime – moving into the heart.

The beating of the heart, or the pulse, consists in this repeating expansion.

this material that passes into the heart, that

The violent agitation of the heat makes the blood:

• expand and move apart and become separated
• gather and press and bump against one another and divide into many extremely tiny branches.

These branches remain so close to one another.

• Only the fire-aether can occupy the spaces remaining around them.

The particles that, in leaving the heart, join together with one another in this way, never leave the circuit by which they return to it, in contrast to the many other particles that penetrate the mass of seed more easily, and from the seed new particles continue to move towards the heart, until it is all used up.

This is why the blood of all animals is red, as explained in:

• Dioptrics and Principles of Philosophy on the nature of light
• Meteors on the nature of colours

We see light through the pressure exerted by the air-aether [2nd element] which are made up of many little corpuscles all touching one another.

These corpuscles have 2 motions:

1. They follow a straight line towards our eyes

This gives us the sensation of light.

2. They turn around their own centres.

If their rotation speed is much less than that of their rectilinear motion, the body which they come from appears blue.

If they turn much more quickly, it looks red to us.

Blood particles have branches so delicate and so close to one another. Only the fire-aether can go around them.

On the surface of the blood, the air-aether meets the fire-aether.

The fire-aether continually:

• passes very quickly obliquely from one blood-pore to the next
• moves in the opposite direction to the air-aether

This forces the air-aether to rotate faster, creating a red color.

This is why hot iron and burning coals appear red – their pores are filled only with the fire-aether.

• Their pores are not as small as those of blood.
• This is why their shade of red is different from that of blood.

As soon as the heart begins to form in this way, the decompressed blood which leaves it takes its course in a straight line in the direction in which it is freest to move, which is the region where the brain will later be formed.

The path taken by the blood begins to form the upper part of the aorta.

Because of the resistance offered by the parts of the seed that it encounters, the blood does not travel very far in a straight line. It is pushed back towards the heart along the same path by which it came.

But it cannot go back down this path because the way is blocked by the new blood that the heart is producing.

This forces it to return to the side opposite to that of the new material entering the heart.

It is on this side, where the spine will later develop, that it makes its way towards the region where the parts that will serve for generation will be formed, and the path that it takes in its descent is the lower part of the aorta.

But because parts of the seed also press on it from this side, they resist the movement of the blood.

The heart continually sends new blood to the top and bottom of this artery. And so this blood is forced to take a circular path back towards the heart, via the side furthest from the spine, where the chest will later develop.

The path that the blood takes in returning thus to the heart is the vena cava.