Animal Spirits and Digestion

26. Animal spirits can exist at different times, in more or less abundance.

Among themselves, their particles can be:

• more or less dense
• more or less agitated or
• more or less unequal

In our body, we are affected by diverse temperaments and natural affections from:

• the constitution of the brain or
• the peculiar affections of the soul
• those differences in the animal spirits

If these spirit particles were:

• greater in abundance than usual, they will have the capacity to excite movements which testify to goodness, generosity, and love in us.
• stronger and denser, they will excite confidence and boldness

• more agitated, they will excite promptness, diligence, and desire
• equally moved, they will excite tranquility of mind.*

Conversely, they manifest malignity, timidity, inconstancy, negligence, and restlessness if they lack these qualities.

All other temperaments, or natural inclinations, are composed of or depend on these.

For instance, a cheerful temperament is composed of promptness and tranquility of mind.

But goodness and confidence make that temperament more perfect.

A sad temperament consists of slowness and restlessness.

• This can be intensified by malice and fear.

A choleric temperament is formed by promptness and restlessness.

• This can be strengthened by malignancy and confidence.

The same goes for the others.

Those temperaments, or at least the passions to which they incline, also depend greatly on the impressions with which the substance of the brain is affected.

What are the causes of the differences in spirits?

27. The juice of foods passes through the stomach into the veins, mingling with the blood.

This juice always imparts certain of its qualities to the blood.

When it is freshly mixed with blood, the blood becomes thicker.

• This makes the finer blood less agitated, less efficacious, and less abundant than usual.
• Consequently, they do not impart as much vigor and lightness to the body as they do later.

The blood sends the finer particles of blood to the brain to become animal spirits there.

After complete digestion, the blood gets more subtlety through repeated passage through the heart.

Moreover, the air that is inspired, also mingling with the blood in a certain manner before it enters the left ventricle of the heart, causes it to be more strongly ignited there.

There it produces spirits that are more lively and more agitated in dry weather than in humid weather.

• This is the same as flames flare up more violently in dry weather.

The liver pours the blood into the heart.

• When the liver is well disposed and labors perfectly for this, the spirits that are excreted from that blood are far more copious and evenly agitated.

But when the liver is pressed by its nerves, the finer parts of the blood inside it go up suddenly to the heart.

• This will also generate spirits more copious and lively than usual, yet less evenly agitated.

Bile is naturally meant to purge the blood.

It bile fails its duty to inflame the remaining mass of blood in the heart from those parts that are more apt to be inflamed, or if it is constricted by its nerve or another part of the body, the matter it contains will be poured back into the veins.

The spirits will be more lively or agile, yet more unevenly agitated.

The spleen’s duty is to purify the blood from those parts that are less likely to be inflamed in the heart.

If the spleen is ill disposed, or if it is constricted or pressed by its nerve or another part of the body, the matter it contains will be regurgitated into the veins.

The spirits will then be less copious, less agitated, and more unevenly driven.

Finally, all those things that can bring about some change in the blood can also change the spirits.

This is especially true to the little nerve that terminates in the heart. It can:

• expand and contract
• impart a thousand differentiations to the spirits. This is done through:
  • the 2 entrances through which the blood of the veins and the air from the lungs descend
  • the blood exhales into the arteries.

This is similar to how the heat of certain lamps used in chemistry can be varied in various ways through:

• the valve that feeds it with fuel
• the valve that lets smoke escape