prolonged contraction of the several surrounding muscles suffice.
As the lacrymal glands of children are easily excited, I persuaded
my own and several other children of different ages to contract
these muscles repeatedly with their utmost force, and to continue
doing so as long as they possibly could; but this produced hardly
any effect. There was sometimes a little moisture in the eyes,
but not more than apparently could be accounted for by the squeezing
out of the already secreted tears within the glands.

The nature of the relation between the involuntary and energetic
contraction of the muscles round the eyes, and the secretion of tears,
cannot be positively ascertained, but a probable view may be suggested.
The primary function of the secretion of tears, together with some mucus,
is to lubricate the surface of the eye; and a secondary one,
as some believe, is to keep the nostrils damp, so that the inhaled
air may be moist,[21] and likewise to favour the power of smelling.
But another, and at least equally important function of tears, is to wash
out particles of dust or other minute objects which may get into the eyes.
That this is of great importance is clear from the cases in which the cornea
has been rendered opaque through inflammation, caused by particles
of dust not being removed, in consequence of the eye and eyelid becoming
immovable.[22] The secretion of tears from the irritation of any foreign
body in the eye is a reflex action;--that is, the body irritates a
peripheral nerve which sends an impression to certain sensory nerve-cells;
these transmit an influence to other cells, and these again to the
lacrymal glands. The influence transmitted to these glands causes,
as there is good reason to believe, the relaxation of the muscular
coats of the smaller arteries; this allows more blood to permeate
the glandular tissue, and this induces a free secretion of tears.
When the small arteries of the face, including those of the retina,