The Animal Spirits

The spirits flow through the nerves into the muscles, and swell them according to how the brain distributes them.

This causes the movement of all the limbs.

It is the little filaments of which the interior substance of these nerves is composed which serve the senses.

These little nets are enclosed in pipes which are always swollen and held open by the spirits in them.

They do not crowd or impede one another.

They are extended from the brain to the extremities of all the members which are capable of feeling.

If one touches and does move the place of these members where some of them are attached, one also makes move at the same moment the place of the brain from which it comes, pulling one of the ends of a cord which is all tense, one makes the other end move at the same instant.

These nets are thus enclosed in pipes which are always held a little swollen and half-open by the spirits.

They are much more:

• slender than those spun by silkworms
• weaker than those of spiders.

But they extend from the head to the furthest members without any risk of breaking.

Philosophers say that in order to feel, the soul needs to contemplate some images which are sent by objects to the brain.

It is impossible for them to show us how they can be formed by these objects, and received by the external sense organs, and transmitted by the nerves to the brain.

They had no reason to suppose them, except that, seeing that

Our thought can easily be excited by a painting. This makes us conceive the object painted there.

Those philosophers connected this with how objects touch our senses.

Instead, I believe that there are several things other than images which can excite our thoughts. For example:

• the signs and the lyrics

The objects that we feel truly send their images to the interior of our brain.

There are no images which must in every respect resemble the objects which they represent.

For otherwise, there would be no distinction between the object and its image, but it suffices that they resemble them in a little things.

Often even that their perfection depends on what they do not resemble them so much as they could do.

An example are the intaglios which are made only of a little ink, placed here and there on paper.

They represent to us forests, cities, men, and even battles and storms.

although, of an infinity of diverse qualities that they make us conceive of in these objects, there is none that the only figure whose resemblance they have properly.

Even then this is a very imperfect resemblance, since, on a quite flat surface, they represent to us bodies variously raised and sunken, and that even, according to the rules of perspective, often they better represent circles by ovals than by other circles, and squares by lozenges than by other squares, and so with all the other figures; so that often, to be more perfect in quality of images and better represent an object, they must not resemble it.

The images which are formed in our brain gives the soul a means of feeling all the various qualities of the objects to which they are attached.

When the blind man touches some bodies with his stick, these bodies do not send anything him. They only make his stick move differently according to the qualities in them.

They move the nerves of his hand, and then the places of his brain where these nerves come from.

This gives occasion to his soul to feel as many different qualities in these bodies as there are varieties in the movements which are caused by them in his brain.