The Effects of the Pineal Gland

Gland H is composed of a very soft material – a substance that is not united with the substance of the brain everywhere, but is only attached to it by small arteries. The tunics of which are sufficiently loose and foldable, suspended as if on a balance, by the force of the blood which the heat of the heart impels into it.

So that it can easily be determined to incline more or less towards itself, now here, now there. By inclining, it disposes the spirits that emanate from it to flow more towards these parts of the brain than those.

However, two considerations arise here (the forces of the soul, which will be discussed later, not being counted) that can move that gland:

1. The difference between the particles of the spirits that emanate from it.

If all the spirits were of equal strength, and there were no other cause that could incline it here or there, then the spirits would flow equally through all the pores of the gland.

It would be held entirely immobile like a balance in the center of the head, as shown in figure 40.

However, a body attached to certain threads and lifted by the force of smoke coming out of a chimney would continually fluctuate depending on how the smoke acted on it.

So too, the particles of those spirits that uplift and sustain that gland, almost always vary slightly, inclining it now to one side, now to another, as seen in figure 41.

The center H is somewhat farther from the center of the brain, marked with the letter O.

The extremities of the arteries that sustain it are also farther from the center and so curved that almost all the spirits they offer tend through the surface a, b, c, to tubes 2, 4, 6, 8: thus opening the pores of those tubes which look more directly there than others.

The spirits emanate from certain parts of the surface of the gland, rather than from others. They can cause the interior surface of the brain’s tubes into which they are received, to turn towards the places from which they emanate.

• This is unless they find them all turned in that direction.

This causes the members, to which those tubes are attached, to move to those places referred to by the parts of surface H.

The idea of the motion of the members consists only in the way how the spirits leap from that gland. Thus, the motion itself is formed from its idea.

For example, Tube 8 turns more towards point b than elsewhere only because the spirits emanating from this point tend with greater force towards it than others.

• This affords the soul an opportunity to feel the arm turning towards B.

All the points to which those tubes can be turned correspond in such a way to all the places to which the arm, noted 7, can be moved.

The arm is turned towards object B for no other reason than that its tube looks at point b.

But if the spirits change their course and turned their tube to some other point, say to c, the filaments 7, arising around it, would expand or contract their position in the same way.

• They would dilate some brain pores situated around d, and others, so that the spirits from them would turn the arm towards object C.

As conversely, if some other action, other than that of the spirits entering through tube 8, were to turn the same arm towards B or towards C, causing those tubes 8 or d to turn towards b or c: and thus the idea of that motion would also be formed; at least if attention were not distracted, that is, if gland H were not hindered from inclining towards 8 by some stronger action.

Thus, any other tube situated on the inner surface of the brain refers to each of the other members. Each of the other points on the surface of gland H, to any place to which those members can be turned.

So the motion of the members, and their ideas mutually and reciprocally cause nothing to oppose.

This is why when both the eye and the other sense-organs are turned to the same object, only one idea is formed in its brain, not multiple ideas.

The same points of this surface of gland H, from which the spirits emanate, which, tending to various tubes, can cause different members to be turned to different objects:

As here, for example, spirits emanate from the point b alone, which, tending to tubes 4 and 8, at the same time turn both eyes and the right arm towards object B: which is not difficult to believe.

Moreover, to understand in what idea the distance of the object consists; it must be considered how much the surface changes its position, those same points refer to places so much more distant from the center of the brain, noted O, the closer they are, and the closer, the Figure 40.

They are more distant.

For example, if point B had moved back a little, it would refer to a more remote place than B.

But if it were a little more inclined towards the anterior part, it would refer to a closer place. This is why the soul can sometimes perceive different objects with the same organs, arranged in the same way, although nothing is changed except the position of gland H.

For example, the soul may perceive what is at point l, by holding two sticks N L and O L with two hands.

Since spirits emanate from point l of gland H, tending to 7 and 8, to which those two hands respond.

But if this gland H were still closer, so that points n and o were in places marked I, K, and consequently spirits had emanated from them, tending to 7 and 8, the soul should perceive what is at N and O, by the same hands, also not changed at all.

However, when gland H is inclined towards some part solely by the force of the spirits, the rational soul and external senses contribute nothing to the production of ideas formed on the surface of the gland. Ideas then arise from:

• the inequalities of the spirits, which consist of the particular ones mutually encountering each other, and
• traces of memory

When the distinctive shape of an object is impressed on a part of the brain more distinctly than any other, the gland accurately inclines to it.

• The spirits tending towards it then receive the impression.
• This is why past things sometimes return to thought merely by chance, even if memory is not much excited by any object that strikes the senses.

But if, as often happens, more and different figures are found almost equally perfectly impressed on the same part of the brain, the spirits will receive something from the impression of each, more or less, as their particles come upon them differently.

Thus, in this way chimeras and hippogriffs are created in the imagination of people who dream while awake. They let loose their imagination through laziness, not diverted by any external objects, nor governed by reason.

But the effect of memory, whose examination is here of greater utility, consists in this, that this machine, even though no soul exists in it, can nevertheless be naturally arranged so that it can imitate the motions of true men, or other similar things that are present to it.

Another cause that can determine the motion of gland H is the action of objects on the senses that occur.

The first effect is that when the entrances of the tubes 2, 4, 6, 8 are dilated, the action of objects A, B, C, the spirits, which immediately begin to flow more freely and vigorously towards them than before, attract that gland a little after themselves: which if it were not hindered from elsewhere, would become more inclined.

By changing the arrangement of its pores, it would emit more spirits through a, b, c, to 2, 4, 6, 8 than before.

This renders the idea formed by those spirits so much more perfect.

Another effect is when the gland is thus held inclined in some way, it is hindered from receiving ideas of objects that affect the organs of other senses so easily.

For example, when almost all the spirits produced by gland H emanate from points a, b, c, they do not sufficiently emanate from point d to form the idea of object D.

Hence, the action is not as lively, nor as effective, as from a, b, c.

This means that the ideas interfere with each other. Therefore, the more senses are involved, the weaker is each one individually.

Whenever the sense-organs are affected more strongly by this than by that, not yet accurately disposed to receive that action, the presence of that object alone is sufficient to complete that disposition.

For example, if the eye looks at a very remote place, when the object A, B, C, which is very close to it, begins to present itself, the action of this object can cause it to be immediately arranged to be looked at with a fixed gaze.