At first sight, it might appear that we invariably cry because we are
sad, but this is by no means the case! We may cry because we are hurt,
physically or mentally, or because of joy or excessive happiness, or
because of any tender emotion, or when hearing beautiful music, or
seeing some splendid action of bravery, or for many other reasons.
Like laughter, crying may thus be due to various causes. Some of these
are purely physiological, due to sensory impressions or congestion of
the circulation. Thus, smelling onions will induce a flow of tears--a
defensive mechanism to protect the eyes. A foreign body, an insect or
a particle of dust in the eye will induce the same result. Again tears
are protective. Coughing, vomiting, strong effort, will also cause the
eyes to water; and here again “crying” is brought about by physical
means alone.
Weeping is usually due to some strong psychic initiation, however, such
as some powerful emotion. But this must find expression through the
mechanism of the body, and this consists in a stimulation of the tear
glands (lachrymal glands) situated just above the eyes, whose normal
duty it is to supply just enough fluid to keep the eyes moistened.
Excessive stimulation of these glands will cause a flow of tiny drops
of water, which run across the eyes, and into the nose; but if an
excessive quantity of water be produced at once, they overflow the
eye-lids and fall onto the cheeks--“crying.”
This sudden increase of the lachrymal secretion depends upon the
increase in the pressure of the blood; this in turn is increased by the
emotions of joy or tenderness, as is proved by the “shining” of the
eyes. The appearance of tears would be the natural consequence. Tears
produce relief by lessening this congestion within the head. They are
a safety-valve on the part of Nature. We cry to relieve this internal
congestion.