The Senses In General

To explain the eye, we must explain the senses.

It is the soul which feels and not the body.

When it is diverted by an ecstasy or strong contemplation, the whole body remains without feeling, although there are various objects which touch it.

The external senses do not sense. It is the brain which does.

We see wounds and illnesses which offend only the brain and impedes all the senses, although the rest of the body does not allow it to be animated.

The impressions from objects in the external senses reach the soul in the brain through the intermediary of the nerves.

Some accidents harm only some nerve. Thisremoves the feeling from all the parts of the body where this nerve sends these branches.

How does the soul, residing in the brain, receive the impressions of objects through the nerves?

The Parts of the Nerve-Pipe

There are 3 things in these nerves:

1. The skins which envelop them

These take their origin from those which envelop the brain. These are like small pipes divided into several branches which spread here and there through all the limbs in the same way as the veins and arteries

2. Their interior substance

This extends in the form of small nets all along these tubes from the brain, from where it takes its origin, to the extremities of the other members where it attaches.

Each of these small pipes have several of these small nets independent of each other.

3. The animal spirits

These are like a very subtle air or wind*. These come from the chambers or concavities in the brain and flow through these pipes in the nerves into the muscles.

The nerves give feeling to the limbs, and also move them.

There are sometimes paralyses which take away the movement without on that account taking away the feeling. This leads to 2 kinds of nerves:

1. One for the senses [Afferent nerves]
2. One for the movements [Efferent nerves

Sometimes:

• the faculty of feeling was in the skins or membranes
• the faculty of moving was in the interior substance of the nerves

These ideas are very repugnant to experience and to reason.

Whoever has ever been able to notice any nerve which served the movement without also serving some sense?

How, if it were on the skins that feeling depended, could the various impressions of objects by means of these skins reach the brain?