What is Laughter?

123. Why Don’t We Faint from Sadness?

Profound sadness which unexpectedly arises should so tightly constrict the heart’s openings that it could even extinguish its fire.

However, this does not happen. If it does, it is very rare.

This is because there is always blood in the heart that can maintain warmth when its openings are nearly closed.

124. Laughter

Laughter consists in the blood, coming from the right cavity of the heart through the pulmonary vein, suddenly inflating the lungs repeatedly.

This causes the air they contain to forcefully exit through the windpipe, where it forms an inarticulate and loud sound.

As the lungs swell and this air exits, it pushes all the muscles of the diaphragm, chest, and throat, thereby causing movement in the facial muscles connected to them.

Laughter is this action of the face, accompanied by this loud sound.

125. Why does laughter not accompany the greatest Joys?

Laughter seems to be one of the principal signs of joy. But joy can only cause laughter when joy is moderate and mixed with some admiration or some hatred.

In extreme joy, the subject of that joy never leads to bursts of laughter.

Moreover, one cannot easily be induced to laugh by any other cause as when one is sad.

This is because in great joys, the lungs are always so full of blood that they cannot be further inflated repeatedly.

126. The main causes of laughter

I observe only two causes that suddenly inflate the lungs in this way.

1. The surprise of admiration

When combined with joy, this can open the heart’s openings so quickly that a large amount of blood entering suddenly through the right side via the vena cava becomes rarefied there, and passing through the pulmonary vein, inflates the lung.

2. The mixture of some liquid that increases the rarefaction of the blood

An example is the more flowing part of that which comes from the spleen.

This part of the blood, pushed toward the heart by a slight motion of hatred, aided by the surprise of admiration, and mingling there with blood coming from other parts of the body, which joy abundantly introduces, can cause this blood to expand much more than usual.

127. Its cause in Indignation

Laughter sometimes accompanies indignation. It is usually artificial and feigned.

But when it is natural, it seems to arise from the joy one has in seeing that one cannot be offended by the evil of which one is indignant, combined with the surprise of the novelty or unexpected encounter with this evil.

Therefore, joy, hatred, and admiration contribute to it.

However, it can also be produced without any joy, solely by the movement of aversion. This sends blood from the spleen to the heart, where it is rarefied and pushed into the lung, which it easily inflates when it finds it nearly empty.

Generally, anything that can suddenly inflate the lung in this manner causes the outward action of laughter, except when sadness changes it to sighs and cries accompanying tears.

128. The origin of Tears

Just as laughter is never caused by extreme joy, tears do not come from extreme sadness, but only from that which is moderate and accompanied or followed by some feeling of love or even joy.

Vapors continually emanate from all parts of our body. But none of them exit as much as from the eyes, due to:

• the size of the optic nerves and
• the multitude of small arteries through which they enter.

Just as sweat consists only of vapors that, exiting from other parts, convert into water on their surface, tears form from vapors that exit from the eyes.

129. How Vapors Turn into Water

My work “The Meteors” explained how air vapors transform into rain.

This happens when they are less agitated or more abundant than usual.

When those leaving the body are much less agitated than usual.

They still convert into water even if they are not necessarily more abundant.

This causes cold sweats that sometimes arise from weakness when one is ill.

Similarly, when they are much more abundant, provided they are not more agitated, they also convert into water, which causes sweat during exercise.

However, the eyes do not sweat during exercise because during physical exertion, most of the spirits move towards the muscles used for movement, and less through the optic nerve towards the eyes.

It is the same substance that composes blood while in veins or arteries, spirits when in the brain, nerves, or muscles, vapors when they exit in the form of air, and finally sweat or tears when they thicken into water on the surface of the body or eyes.